FLOSS Best Practices Criteria (All Levels)

This is the set of best practices for Free/Libre and Open Source Software (FLOSS) projects to achieve the Open Source Security Foundation (OpenSSF) Best Practices badges at the passing, silver, and gold badge levels. You can show this list with just the criteria or with additional information. You may also view just the passing, silver, and gold criteria, as well as criteria statistics.

See criteria discussion for more information about these criteria.

Passing

Basics

Basic project website content

• The project website MUST succinctly describe what the software does (what problem does it solve?). ^{[description_good]}

  Details:

  This MUST be in language that potential users can understand (e.g., it uses minimal jargon).

• The project website MUST provide information on how to: obtain, provide feedback (as bug reports or enhancements), and contribute to the software. ^[interact]
• The information on how to contribute MUST explain the contribution process (e.g., are pull requests used?) {Met URL} ^{[contribution]}

  Details:

  We presume that projects on GitHub use issues and pull requests unless otherwise noted. This information can be short, e.g., stating that the project uses pull requests, an issue tracker, or posts to a mailing list (which one?)

  Rationale:

  Contributors need to understand not only how to contribute, but also the overall contribution process, so that they'll understand how their work could be incorporated and what the expectations are after the initial submission. This means that wherever the project describes how to contribute, the project must include (directly or by reference) information on the contribution process. Note that criterion "interact" (listed earlier) requires that the contribution information be on the project website.

• The information on how to contribute SHOULD include the requirements for acceptable contributions (e.g., a reference to any required coding standard). {Met URL} ^{[contribution_requirements]}

FLOSS license

• The software produced by the project MUST be released as FLOSS. ^{[floss_license]}

  Details:

  FLOSS is software released in a way that meets the Open Source Definition or Free Software Definition. Examples of such licenses include the CC0, MIT, BSD 2-clause, BSD 3-clause revised, Apache 2.0, Lesser GNU General Public License (LGPL), and the GNU General Public License (GPL). For our purposes, this means that the license MUST be:

  • an approved license by the Open Source Initiative (OSI), or
  • a free license as approved by the Free Software Foundation (FSF), or
  • a free license acceptable to Debian main, or
  • a "good" license according to Fedora.

  The software MAY also be licensed other ways (e.g., "GPLv2 or proprietary" is acceptable).

  Rationale:

  These criteria are designed for FLOSS projects, so we need to ensure that they're only used where they apply. Some projects may be mistakenly considered FLOSS even though they are not (e.g., they might not have any license, in which case the defaults of the country's legal system apply, or they might use a non-FLOSS license). We've added "produced by the project" as a clarification - many projects use non-FLOSS software/services in the process of creating software, or depend on them to run, and that is allowed.

• It is SUGGESTED that any required license(s) for the software produced by the project be approved by the Open Source Initiative (OSI). ^{[floss_license_osi]}

  Details:

  The OSI uses a rigorous approval process to determine which licenses are OSS.

  Rationale:

  Unusual licenses can cause long-term problems for FLOSS projects and are more difficult for tools to handle. That said, there are FLOSS licenses that are not OSI-approved, e.g., the CC0 license is used by many projects but is not OSI-approved at the time of this writing. We expect that more advanced badges would set a higher bar (e.g., that it must be released under an OSI-approved license).

• The project MUST post the license(s) of its results in a standard location in their source repository. {Met URL} ^{[license_location]}

  Details:

  One convention is posting the license as a top-level file named LICENSE or COPYING, which MAY be followed by an extension such as ".txt" or ".md". An alternative convention is to have a directory named LICENSES containing license file(s); these files are typically named as their SPDX license identifier followed by an appropriate file extension, as described in the REUSE Specification. Note that this criterion is only a requirement on the source repository. You do NOT need to include the license file when generating something from the source code (such as an executable, package, or container). For example, when generating an R package for the Comprehensive R Archive Network (CRAN), follow standard CRAN practice: if the license is a standard license, use the standard short license specification (to avoid installing yet another copy of the text) and list the LICENSE file in an exclusion file such as .Rbuildignore. Similarly, when creating a Debian package, you may put a link in the copyright file to the license text in /usr/share/common-licenses, and exclude the license file from the created package (e.g., by deleting the file after calling dh_auto_install). We encourage including machine-readable license information in generated formats where practical.

  Rationale:

  The goal is to make the license very clear and connected with the project results it applies to. It is a good idea to also make the license clear on the project website, but there isn't a widely-accepted way to do that today.

Documentation

• The project MUST provide basic documentation for the software produced by the project. {N/A justification} ^{[documentation_basics]}

  Details:

  This documentation must be in some media (such as text or video) that includes: how to install it, how to start it, how to use it (possibly with a tutorial using examples), and how to use it securely (e.g., what to do and what not to do) if that is an appropriate topic for the software. The security documentation need not be long. The project MAY use hypertext links to non-project material as documentation. If the project does not produce software, choose "not applicable" (N/A).

  Rationale:

  Potential users need documentation so that they can learn how to use the software. This documentation could be provided via the project website or repository, or even via hyperlink to some external information, so we do not specify exactly where this information is.

• The project MUST provide reference documentation that describes the external interface (both input and output) of the software produced by the project. {N/A justification} ^{[documentation_interface]}

  Details:

  The documentation of an external interface explains to an end-user or developer how to use it. This would include its application program interface (API) if the software has one. If it is a library, document the major classes/types and methods/functions that can be called. If it is a web application, define its URL interface (often its REST interface). If it is a command-line interface, document the parameters and options it supports. In many cases it's best if most of this documentation is automatically generated, so that this documentation stays synchronized with the software as it changes, but this isn't required. The project MAY use hypertext links to non-project material as documentation. Documentation MAY be automatically generated (where practical this is often the best way to do so). Documentation of a REST interface may be generated using Swagger/OpenAPI. Code interface documentation MAY be generated using tools such as JSDoc (JavaScript), ESDoc (JavaScript), pydoc (Python), devtools (R), pkgdown (R), and Doxygen (many). Merely having comments in implementation code is not sufficient to satisfy this criterion; there needs to be an easy way to see the information without reading through all the source code. If the project does not produce software, choose "not applicable" (N/A).

Other

• The project sites (website, repository, and download URLs) MUST support HTTPS using TLS. ^{[sites_https]}

  Details:

  This requires that the project home page URL and the version control repository URL begin with "https:", not "http:". You can get free certificates from Let's Encrypt. Projects MAY implement this criterion using (for example) GitHub pages, GitLab pages, or SourceForge project pages. If you support HTTP, we urge you to redirect the HTTP traffic to HTTPS.

• The project MUST have one or more mechanisms for discussion (including proposed changes and issues) that are searchable, allow messages and topics to be addressed by URL, enable new people to participate in some of the discussions, and do not require client-side installation of proprietary software. ^[discussion]

  Details:

  Examples of acceptable mechanisms include archived mailing list(s), GitHub issue and pull request discussions, Bugzilla, Mantis, and Trac. Asynchronous discussion mechanisms (like IRC) are acceptable if they meet these criteria; make sure there is a URL-addressable archiving mechanism. Proprietary JavaScript, while discouraged, is permitted.

• The project SHOULD provide documentation in English and be able to accept bug reports and comments about code in English. ^[english]

  Details:

  English is currently the lingua franca of computer technology; supporting English increases the number of different potential developers and reviewers worldwide. A project can meet this criterion even if its core developers' primary language is not English.

• The project MUST be maintained. ^[maintained]

  Details:

  As a minimum, the project should attempt to respond to significant problem and vulnerability reports. A project that is actively pursuing a badge is probably maintained. All projects and people have limited resources, and typical projects must reject some proposed changes, so limited resources and proposal rejections do not by themselves indicate an unmaintained project.
  
  When a project knows that it will no longer be maintained, it should set this criterion to "Unmet" and use the appropriate mechanism(s) to indicate to others that it is not being maintained. For example, use “DEPRECATED” as the first heading of its README, add “DEPRECATED” near the beginning of its home page, add “DEPRECATED” to the beginning of its code repository project description, add a no-maintenance-intended badge in its README and/or home page, mark it as deprecated in any package repositories (e.g., npm deprecate), and/or use the code repository's marking system to archive it (e.g., GitHub's "archive" setting, GitLab’s "archived" marking, Gerrit's "readonly" status, or SourceForge’s "abandoned" project status). Additional discussion can be found here.

Change Control

Public version-controlled source repository

• The project MUST have a version-controlled source repository that is publicly readable and has a URL. ^{[repo_public]}

  Details:

  The URL MAY be the same as the project URL. The project MAY use private (non-public) branches in specific cases while the change is not publicly released (e.g., for fixing a vulnerability before it is revealed to the public).

• The project's source repository MUST track what changes were made, who made the changes, and when the changes were made. ^[repo_track]
• To enable collaborative review, the project's source repository MUST include interim versions for review between releases; it MUST NOT include only final releases. ^{[repo_interim]}

  Details:

  Projects MAY choose to omit specific interim versions from their public source repositories (e.g., ones that fix specific non-public security vulnerabilities, may never be publicly released, or include material that cannot be legally posted and are not in the final release).

• It is SUGGESTED that common distributed version control software be used (e.g., git) for the project's source repository. ^{[repo_distributed]}

  Details:

  Git is not specifically required and projects can use centralized version control software (such as subversion) with justification.

Unique version numbering

• The project results MUST have a unique version identifier for each release intended to be used by users. ^{[version_unique]}

  Details:

  This MAY be met in a variety of ways including a commit IDs (such as git commit id or mercurial changeset id) or a version number (including version numbers that use semantic versioning or date-based schemes like YYYYMMDD).

• It is SUGGESTED that the Semantic Versioning (SemVer) or Calendar Versioning (CalVer) version numbering format be used for releases. It is SUGGESTED that those who use CalVer include a micro level value. ^{[version_semver]}

  Details:

  Projects should generally prefer whatever format is expected by their users, e.g., because it is the normal format used by their ecosystem. Many ecosystems prefer SemVer, and SemVer is generally preferred for application programmer interfaces (APIs) and software development kits (SDKs). CalVer tends to be used by projects that are large, have an unusually large number of independently-developed dependencies, have a constantly-changing scope, or are time-sensitive. It is SUGGESTED that those who use CalVer include a micro level value, because including a micro level supports simultaneously-maintained branches whenever that becomes necessary. Other version numbering formats may be used as version numbers, including git commit IDs or mercurial changeset IDs, as long as they uniquely identify versions. However, some alternatives (such as git commit IDs) can cause problems as release identifiers, because users may not be able to easily determine if they are up-to-date. The version ID format may be unimportant for identifying software releases if all recipients only run the latest version (e.g., it is the code for a single website or internet service that is constantly updated via continuous delivery).

  Rationale:

  SemVer is widely used to communicate what an update is (e.g., if it involves incompatible API changes), whether something is newer or older. The scheme is simple, supports multiple simultaneous branches, and because it uses at least three numbers it can be distinguished from floating point. However, many find SemVer less useful for identifying software versions if only one version of the component is run (e.g., it is the code for a single website or internet service that is constantly updated via continuous delivery). For more discussion of the pros and cons of SemVer, see Hacker News' Is Semantic Versioning an Anti-Pattern? and The Semantic Versioning Anti-Pattern.

• It is SUGGESTED that projects identify each release within their version control system. For example, it is SUGGESTED that those using git identify each release using git tags. ^{[version_tags]}

Release notes

• The project MUST provide, in each release, release notes that are a human-readable summary of major changes in that release to help users determine if they should upgrade and what the upgrade impact will be. The release notes MUST NOT be the raw output of a version control log (e.g., the "git log" command results are not release notes). Projects whose results are not intended for reuse in multiple locations (such as the software for a single website or service) AND employ continuous delivery MAY select "N/A". {N/A justification} {Met URL} ^{[release_notes]}

  Details:

  The release notes MAY be implemented in a variety of ways. Many projects provide them in a file named "NEWS", "CHANGELOG", or "ChangeLog", optionally with extensions such as ".txt", ".md", or ".html". Historically the term "change log" meant a log of every change, but to meet these criteria what is needed is a human-readable summary. The release notes MAY instead be provided by version control system mechanisms such as the GitHub Releases workflow.

  Rationale:

  Release notes are important because they help users decide whether or not they will want to update, and what the impact would be (e.g., if the new release fixes vulnerabilities). We realize this may not apply to projects whose main results are continuously updated and are deployed to primarily one place and so allow "N/A" from such projects.

• The release notes MUST identify every publicly known run-time vulnerability fixed in this release that already had a CVE assignment or similar when the release was created. This criterion may be marked as not applicable (N/A) if users typically cannot practically update the software themselves (e.g., as is often true for kernel updates). This criterion applies only to the project results, not to its dependencies. If there are no release notes or there have been no publicly known vulnerabilities, choose N/A. {N/A justification} ^{[release_notes_vulns]}

  Details:

  This criterion helps users determine if a given update will fix a vulnerability that is publicly known, to help users make an informed decision about updating. If users typically cannot practically update the software themselves on their computers, but must instead depend on one or more intermediaries to perform the update (as is often the case for a kernel and low-level software that is intertwined with a kernel), the project may choose "not applicable" (N/A) instead, since this additional information will not be helpful to those users. Similarly, a project may choose N/A if all recipients only run the latest version (e.g., it is the code for a single website or internet service that is constantly updated via continuous delivery). This criterion only applies to the project results, not its dependencies. Listing the vulnerabilities of all transitive dependencies of a project becomes unwieldy as dependencies increase and vary, and is unnecessary since tools that examine and track dependencies can do this in a more scalable way.

Reporting

Bug-reporting process

• The project MUST provide a process for users to submit bug reports (e.g., using an issue tracker or a mailing list). {Met URL} ^{[report_process]}
• The project SHOULD use an issue tracker for tracking individual issues. ^{[report_tracker]}
• The project MUST acknowledge a majority of bug reports submitted in the last 2-12 months (inclusive); the response need not include a fix. ^{[report_responses]}
• The project SHOULD respond to a majority (>50%) of enhancement requests in the last 2-12 months (inclusive). ^{[enhancement_responses]}

  Details:

  The response MAY be 'no' or a discussion about its merits. The goal is simply that there be some response to some requests, which indicates that the project is still alive. For purposes of this criterion, projects need not count fake requests (e.g., from spammers or automated systems). If a project is no longer making enhancements, please select "unmet" and include the URL that makes this situation clear to users. If a project tends to be overwhelmed by the number of enhancement requests, please select "unmet" and explain.

• The project MUST have a publicly available archive for reports and responses for later searching. {Met URL} ^{[report_archive]}

Vulnerability report process

• The project MUST publish the process for reporting vulnerabilities on the project site. {Met URL} ^{[vulnerability_report_process]}

  Details:

  Projects hosted on GitHub SHOULD consider enabling privately reporting a security vulnerability. Projects on GitLab SHOULD consider using its ability for privately reporting a vulnerability. Projects MAY identify a mailing address on https://PROJECTSITE/security, often in the form security@example.org. This vulnerability reporting process MAY be the same as its bug reporting process. Vulnerability reports MAY always be public, but many projects have a private vulnerability reporting mechanism.

• If private vulnerability reports are supported, the project MUST include how to send the information in a way that is kept private. {N/A allowed} {Met URL} ^{[vulnerability_report_private]}

  Details:

  Examples include a private defect report submitted on the web using HTTPS (TLS) or an email encrypted using OpenPGP. If vulnerability reports are always public (so there are never private vulnerability reports), choose "not applicable" (N/A).

• The project's initial response time for any vulnerability report received in the last 6 months MUST be less than or equal to 14 days. {N/A allowed} ^{[vulnerability_report_response]}

  Details:

  If there have been no vulnerabilities reported in the last 6 months, choose "not applicable" (N/A).

Quality

Working build system

• If the software produced by the project requires building for use, the project MUST provide a working build system that can automatically rebuild the software from source code. {N/A allowed} ^[build]

  Details:

  A build system determines what actions need to occur to rebuild the software (and in what order), and then performs those steps. For example, it can invoke a compiler to compile the source code. If an executable is created from source code, it must be possible to modify the project's source code and then generate an updated executable with those modifications. If the software produced by the project depends on external libraries, the build system does not need to build those external libraries. If there is no need to build anything to use the software after its source code is modified, select "not applicable" (N/A).

  Rationale:

  If a project needs to be built but there is no working build system, then potential co-developers will not be able to easily contribute and many security analysis tools will be ineffective. This is related to Joel Test point 2, "Can you make a build in one step?"

• It is SUGGESTED that common tools be used for building the software. {N/A allowed} ^{[build_common_tools]}

  Details:

  For example, Maven, Ant, cmake, the autotools, make, rake (Ruby), or devtools (R).

• The project SHOULD be buildable using only FLOSS tools. {N/A allowed} ^{[build_floss_tools]}

Automated test suite

• The project MUST use at least one automated test suite that is publicly released as FLOSS (this test suite may be maintained as a separate FLOSS project). The project MUST clearly show or document how to run the test suite(s) (e.g., via a continuous integration (CI) script or via documentation in files such as BUILD.md, README.md, or CONTRIBUTING.md). ^[test]

  Details:

  The project MAY use multiple automated test suites (e.g., one that runs quickly, vs. another that is more thorough but requires special equipment). There are many test frameworks and test support systems available, including Selenium (web browser automation), Junit (JVM, Java), RUnit (R), testthat (R).

  Rationale:

  Automated test suites immediately help detect a variety of problems. A large test suite can find more problems, but even a small test suite can detect problems and provide a framework to build on. E.g., "Tip #62: Test Early, Test Often, Test Automatically" ("The Pragmatic Programmer" by Andrew Hunt and David Thomas, p. 237)

• A test suite SHOULD be invocable in a standard way for that language. ^{[test_invocation]}

  Details:

  For example, "make check", "mvn test", or "rake test" (Ruby).

• It is SUGGESTED that the test suite cover most (or ideally all) the code branches, input fields, and functionality. ^[test_most]
• It is SUGGESTED that the project implement continuous integration (where new or changed code is frequently integrated into a central code repository and automated tests are run on the result). ^{[test_continuous_integration]}

  Rationale:

  See Martin Fowler There has been some shift in the meaning of the term continuous integration. Historically the term continuous integration focused on the first part - the frequent integration - and not on its testing. However, over time the emphasis has shifted to include the notion of running automated tests as soon as the code is integrated. We realize that this can be difficult for some projects to apply, which is why it is only SUGGESTED at the passing level.

New functionality testing

• The project MUST have a general policy (formal or not) that as major new functionality is added to the software produced by the project, tests of that functionality should be added to an automated test suite. ^{[test_policy]}

  Details:

  As long as a policy is in place, even by word of mouth, that says developers should add tests to the automated test suite for major new functionality, select "Met."

• The project MUST have evidence that the test_policy for adding tests has been adhered to in the most recent major changes to the software produced by the project. ^{[tests_are_added]}

  Details:

  Major functionality would typically be mentioned in the release notes. Perfection is not required, merely evidence that tests are typically being added in practice to the automated test suite when new major functionality is added to the software produced by the project.

• It is SUGGESTED that this policy on adding tests (see test_policy) be documented in the instructions for change proposals. ^{[tests_documented_added]}

  Details:

  However, even an informal rule is acceptable as long as the tests are being added in practice.

Warning flags

• The project MUST enable one or more compiler warning flags, a "safe" language mode, or use a separate "linter" tool to look for code quality errors or common simple mistakes, if there is at least one FLOSS tool that can implement this criterion in the selected language. {N/A allowed} ^[warnings]

  Details:

  Examples of compiler warning flags include gcc/clang "-Wall". Examples of a "safe" language mode include JavaScript "use strict" and perl5's "use warnings". A separate "linter" tool is simply a tool that examines the source code to look for code quality errors or common simple mistakes. These are typically enabled within the source code or build instructions.

  Rationale:

  "We routinely set compiler warning levels as high as possible. It doesn't make sense to waste time trying to find a problem that the compiler could find for you! We need to concentrate on the harder problems at hand." ("The Pragmatic Programmer" by Andrew Hunt and David Thomas, p. 91-92) "Tip #23: Always use Source Code Control. Always. Even if you are a single-person team on a one-week project." ("The Pragmatic Programmer" by Andrew Hunt and David Thomas, p. 88)

• The project MUST address warnings. {N/A allowed} ^{[warnings_fixed]}

  Details:

  These are the warnings identified by the implementation of the warnings criterion. The project should fix warnings or mark them in the source code as false positives. Ideally there would be no warnings, but a project MAY accept some warnings (typically less than 1 warning per 100 lines or less than 10 warnings).

• It is SUGGESTED that projects be maximally strict with warnings in the software produced by the project, where practical. {N/A allowed} ^{[warnings_strict]}

  Details:

  Some warnings cannot be effectively enabled on some projects. What is needed is evidence that the project is striving to enable warning flags where it can, so that errors are detected early.

Security

Secure development knowledge

• The project MUST have at least one primary developer who knows how to design secure software. (See ‘details’ for the exact requirements.) ^{[know_secure_design]}

  Details:

  This requires understanding the following design principles, including the 8 principles from Saltzer and Schroeder:

  • economy of mechanism (keep the design as simple and small as practical, e.g., by adopting sweeping simplifications)
  • fail-safe defaults (access decisions should deny by default, and projects' installation should be secure by default)
  • complete mediation (every access that might be limited must be checked for authority and be non-bypassable)
  • open design (security mechanisms should not depend on attacker ignorance of its design, but instead on more easily protected and changed information like keys and passwords)
  • separation of privilege (ideally, access to important objects should depend on more than one condition, so that defeating one protection system won't enable complete access. E.G., multi-factor authentication, such as requiring both a password and a hardware token, is stronger than single-factor authentication)
  • least privilege (processes should operate with the least privilege necessary)
  • least common mechanism (the design should minimize the mechanisms common to more than one user and depended on by all users, e.g., directories for temporary files)
  • psychological acceptability (the human interface must be designed for ease of use - designing for "least astonishment" can help)
  • limited attack surface (the attack surface - the set of the different points where an attacker can try to enter or extract data - should be limited)
  • input validation with allowlists (inputs should typically be checked to determine if they are valid before they are accepted; this validation should use allowlists (which only accept known-good values), not denylists (which attempt to list known-bad values)).

  A "primary developer" in a project is anyone who is familiar with the project's code base, is comfortable making changes to it, and is acknowledged as such by most other participants in the project. A primary developer would typically make a number of contributions over the past year (via code, documentation, or answering questions). Developers would typically be considered primary developers if they initiated the project (and have not left the project more than three years ago), have the option of receiving information on a private vulnerability reporting channel (if there is one), can accept commits on behalf of the project, or perform final releases of the project software. If there is only one developer, that individual is the primary developer. Many books and courses are available to help you understand how to develop more secure software and discuss design. For example, the Secure Software Development Fundamentals course is a free set of three courses that explain how to develop more secure software (it's free if you audit it; for an extra fee you can earn a certificate to prove you learned the material).

• At least one of the project's primary developers MUST know of common kinds of errors that lead to vulnerabilities in this kind of software, as well as at least one method to counter or mitigate each of them. ^{[know_common_errors]}

  Details:

  Examples (depending on the type of software) include SQL injection, OS injection, classic buffer overflow, cross-site scripting, missing authentication, and missing authorization. See the CWE/SANS top 25 or OWASP Top 10 for commonly used lists. Many books and courses are available to help you understand how to develop more secure software and discuss common implementation errors that lead to vulnerabilities. For example, the Secure Software Development Fundamentals course is a free set of three courses that explain how to develop more secure software (it's free if you audit it; for an extra fee you can earn a certificate to prove you learned the material).

Use basic good cryptographic practices

• The software produced by the project MUST use, by default, only cryptographic protocols and algorithms that are publicly published and reviewed by experts (if cryptographic protocols and algorithms are used). {N/A allowed} ^{[crypto_published]}

  Details:

  These cryptographic criteria do not always apply because some software has no need to directly use cryptographic capabilities.

• If the software produced by the project is an application or library, and its primary purpose is not to implement cryptography, then it SHOULD only call on software specifically designed to implement cryptographic functions; it SHOULD NOT re-implement its own. {N/A allowed} ^{[crypto_call]}
• All functionality in the software produced by the project that depends on cryptography MUST be implementable using FLOSS. {N/A allowed} ^{[crypto_floss]}

  Details:

  See the Open Standards Requirement for Software by the Open Source Initiative.

  Rationale:

  Software must interoperate with other software. If the functionality cannot be implemented with FLOSS, e.g., because of patents, then this can set a trap for others who depend on the software.

• The security mechanisms within the software produced by the project MUST use default keylengths that at least meet the NIST minimum requirements through the year 2030 (as stated in 2012). It MUST be possible to configure the software so that smaller keylengths are completely disabled. {N/A allowed} ^{[crypto_keylength]}

  Details:

  These minimum bitlengths are: symmetric key 112, factoring modulus 2048, discrete logarithm key 224, discrete logarithmic group 2048, elliptic curve 224, and hash 224 (password hashing is not covered by this bitlength, more information on password hashing can be found in the crypto_password_storage criterion). See https://www.keylength.com for a comparison of keylength recommendations from various organizations. The software MAY allow smaller keylengths in some configurations (ideally it would not, since this allows downgrade attacks, but shorter keylengths are sometimes necessary for interoperability).

• The default security mechanisms within the software produced by the project MUST NOT depend on broken cryptographic algorithms (e.g., MD4, MD5, single DES, RC4, Dual_EC_DRBG), or use cipher modes that are inappropriate to the context, unless they are necessary to implement an interoperable protocol (where the protocol implemented is the most recent version of that standard broadly supported by the network ecosystem, that ecosystem requires the use of such an algorithm or mode, and that ecosystem does not offer any more secure alternative). The documentation MUST describe any relevant security risks and any known mitigations if these broken algorithms or modes are necessary for an interoperable protocol. {N/A allowed} ^{[crypto_working]}

  Details:

  ECB mode is almost never appropriate because it reveals identical blocks within the ciphertext as demonstrated by the ECB penguin, and CTR mode is often inappropriate because it does not perform authentication and causes duplicates if the input state is repeated. In many cases it's best to choose a block cipher algorithm mode designed to combine secrecy and authentication, e.g., Galois/Counter Mode (GCM) and EAX. Projects MAY allow users to enable broken mechanisms (e.g., during configuration) where necessary for compatibility, but then users know they're doing it.

  Rationale:

  If a cryptographic algorithm or mode is completely broken, then it cannot provide a useful cryptographic service. This is different from having a weakness; many cryptographic algorithms have some weaknesses, yet for backwards-compatibility it may sometimes be appropriate to use the algorithm anyway. "EAX" appears to be a name, not an abbreviation. The paper describing EAX, "A Conventional Authenticated-Encryption Mode" by M. Bellare, P. Rogaway D. Wagner (April 13, 2003), does not give an expansion.

• The default security mechanisms within the software produced by the project SHOULD NOT depend on cryptographic algorithms or modes with known serious weaknesses (e.g., the SHA-1 cryptographic hash algorithm or the CBC mode in SSH). {N/A allowed} ^{[crypto_weaknesses]}

  Details:

  Concerns about CBC mode in SSH are discussed in CERT: SSH CBC vulnerability.

  Rationale:

  SHA-1 has been known to be weak for many years; In February 2017 Google demonstrated a SHA-1 collision. There are a number of alternatives to SHA-1 that are not patent-encumbered, such as the SHA-2 suite (including SHA-256 and SHA-512) and SHA-3. There is some disagreement on how important it is to avoid CBC mode in SSH. The OpenSSH cbc.adv page argues that the attack on SSH CBC is not a practical attack. However, others clearly think it's more important; CERT notes it, as does FAQ: Disable CBC in SSH. It is also easy to use a different mode than CBC; generally when there are safer widely-available options, you should use the safe ones instead. This is a SHOULD, not a MUST; sometimes these weaker mechanisms need to be used for backwards compatibility.

• The security mechanisms within the software produced by the project SHOULD implement perfect forward secrecy for key agreement protocols so a session key derived from a set of long-term keys cannot be compromised if one of the long-term keys is compromised in the future. {N/A allowed} ^[crypto_pfs]
• If the software produced by the project causes the storing of passwords for authentication of external users, the passwords MUST be stored as iterated hashes with a per-user salt by using a key stretching (iterated) algorithm (e.g., Argon2id, Bcrypt, Scrypt, or PBKDF2). See also OWASP Password Storage Cheat Sheet). {N/A allowed} ^{[crypto_password_storage]}

  Details:

  This criterion applies only when the software is enforcing authentication of users using passwords for external users (aka inbound authentication), such as server-side web applications. It does not apply in cases where the software stores passwords for authenticating into other systems (aka outbound authentication, e.g., the software implements a client for some other system), since at least parts of that software must have often access to the unhashed password.

  Rationale:

  This is a bare minimum today when storing passwords. Sometimes software needs to have a credential, such as a password, to authenticate it to other systems; those are intentionally out of scope for this criterion, because in many cases it's not possible to store them as iterated hashes using per-user salt.

• The security mechanisms within the software produced by the project MUST generate all cryptographic keys and nonces using a cryptographically secure random number generator, and MUST NOT do so using generators that are cryptographically insecure. {N/A allowed} ^{[crypto_random]}

  Details:

  A cryptographically secure random number generator may be a hardware random number generator, or it may be a cryptographically secure pseudo-random number generator (CSPRNG) using an algorithm such as Hash_DRBG, HMAC_DRBG, CTR_DRBG, Yarrow, or Fortuna. Examples of calls to secure random number generators include Java's java.security.SecureRandom and JavaScript's window.crypto.getRandomValues. Examples of calls to insecure random number generators include Java's java.util.Random and JavaScript's Math.random.

Secured delivery against man-in-the-middle (MITM) attacks

• The project MUST use a delivery mechanism that counters MITM attacks. Using https or ssh+scp is acceptable. ^{[delivery_mitm]}

  Details:

  An even stronger mechanism is releasing the software with digitally signed packages, since that mitigates attacks on the distribution system, but this only works if the users can be confident that the public keys for signatures are correct and if the users will actually check the signature.

• A cryptographic hash (e.g., a sha1sum) MUST NOT be retrieved over http and used without checking for a cryptographic signature. ^{[delivery_unsigned]}

  Details:

  These hashes can be modified in transit.

Publicly known vulnerabilities fixed

• There MUST be no unpatched vulnerabilities of medium or higher severity that have been publicly known for more than 60 days. ^{[vulnerabilities_fixed_60_days]}

  Details:

  The vulnerability must be patched and released by the project itself (patches may be developed elsewhere). A vulnerability becomes publicly known (for this purpose) once it has a CVE with publicly released non-paywalled information (reported, for example, in the National Vulnerability Database) or when the project has been informed and the information has been released to the public (possibly by the project). A vulnerability is considered medium or higher severity if its Common Vulnerability Scoring System (CVSS) base qualitative score is medium or higher. In CVSS versions 2.0 through 3.1, this is equivalent to a CVSS score of 4.0 or higher. Projects may use the CVSS score as published in a widely-used vulnerability database (such as the National Vulnerability Database) using the most-recent version of CVSS reported in that database. Projects may instead calculate the severity themselves using the latest version of CVSS at the time of the vulnerability disclosure, if the calculation inputs are publicly revealed once the vulnerability is publicly known. Note: this means that users might be left vulnerable to all attackers worldwide for up to 60 days. This criterion is often much easier to meet than what Google recommends in Rebooting responsible disclosure, because Google recommends that the 60-day period start when the project is notified even if the report is not public. Also note that this badge criterion, like other criteria, applies to the individual project. Some projects are part of larger umbrella organizations or larger projects, possibly in multiple layers, and many projects feed their results to other organizations and projects as part of a potentially-complex supply chain. An individual project often cannot control the rest, but an individual project can work to release a vulnerability patch in a timely way. Therefore, we focus solely on the individual project's response time. Once a patch is available from the individual project, others can determine how to deal with the patch (e.g., they can update to the newer version or they can apply just the patch as a cherry-picked solution).

  Rationale:

  We intentionally chose to start measurement from the time of public knowledge, and not from the time reported to the project, because this is much easier to measure and verify by those outside the project.

• Projects SHOULD fix all critical vulnerabilities rapidly after they are reported. ^{[vulnerabilities_critical_fixed]}

Other security issues

• The public repositories MUST NOT leak a valid private credential (e.g., a working password or private key) that is intended to limit public access. ^{[no_leaked_credentials]}

  Details:

  A project MAY leak "sample" credentials for testing and unimportant databases, as long as they are not intended to limit public access.

Analysis

Static code analysis

• At least one static code analysis tool (beyond compiler warnings and "safe" language modes) MUST be applied to any proposed major production release of the software before its release, if there is at least one FLOSS tool that implements this criterion in the selected language. {N/A justification} {Met justification} ^{[static_analysis]}

  Details:

  A static code analysis tool examines the software code (as source code, intermediate code, or executable) without executing it with specific inputs. For purposes of this criterion, compiler warnings and "safe" language modes do not count as static code analysis tools (these typically avoid deep analysis because speed is vital). Some static analysis tools focus on detecting generic defects, others focus on finding specific kinds of defects (such as vulnerabilities), and some do a combination. Examples of such static code analysis tools include cppcheck (C, C++), clang static analyzer (C, C++), SpotBugs (Java), FindBugs (Java) (including FindSecurityBugs), PMD (Java), Brakeman (Ruby on Rails), lintr (R), goodpractice (R), Coverity Quality Analyzer, SonarQube, Codacy, and HP Enterprise Fortify Static Code Analyzer. Larger lists of tools can be found in places such as the Wikipedia list of tools for static code analysis, OWASP information on static code analysis, NIST list of source code security analyzers, and Wheeler's list of static analysis tools. If there are no FLOSS static analysis tools available for the implementation language(s) used, you may select 'N/A'.

• It is SUGGESTED that at least one of the static analysis tools used for the static_analysis criterion include rules or approaches to look for common vulnerabilities in the analyzed language or environment. {N/A allowed} ^{[static_analysis_common_vulnerabilities]}

  Details:

  Static analysis tools that are specifically designed to look for common vulnerabilities are more likely to find them. That said, using any static tools will typically help find some problems, so we are suggesting but not requiring this for the 'passing' level badge.

  Rationale:

  We'd like all projects to use this kind of static analysis tool, but there may not be one in the chosen language, or it may only be proprietary (and some developers will therefore not use it).

• All medium and higher severity exploitable vulnerabilities discovered with static code analysis MUST be fixed in a timely way after they are confirmed. {N/A allowed} ^{[static_analysis_fixed]}

  Details:

  A vulnerability is considered medium or higher severity if its Common Vulnerability Scoring System (CVSS) base qualitative score is medium or higher. In CVSS versions 2.0 through 3.1, this is equivalent to a CVSS score of 4.0 or higher. Projects may use the CVSS score as published in a widely-used vulnerability database (such as the National Vulnerability Database) using the most-recent version of CVSS reported in that database. Projects may instead calculate the severity themselves using the latest version of CVSS at the time of the vulnerability disclosure, if the calculation inputs are publicly revealed once the vulnerability is publicly known. Note that criterion vulnerabilities_fixed_60_days requires that all such vulnerabilities be fixed within 60 days of being made public.

• It is SUGGESTED that static source code analysis occur on every commit or at least daily. {N/A allowed} ^{[static_analysis_often]}

Dynamic code analysis

• It is SUGGESTED that at least one dynamic analysis tool be applied to any proposed major production release of the software before its release. ^{[dynamic_analysis]}

  Details:

  A dynamic analysis tool examines the software by executing it with specific inputs. For example, the project MAY use a fuzzing tool (e.g., American Fuzzy Lop) or a web application scanner (e.g., OWASP ZAP or w3af). In some cases the OSS-Fuzz project may be willing to apply fuzz testing to your project. For purposes of this criterion the dynamic analysis tool needs to vary the inputs in some way to look for various kinds of problems or be an automated test suite with at least 80% branch coverage. The Wikipedia page on dynamic analysis and the OWASP page on fuzzing identify some dynamic analysis tools. The analysis tool(s) MAY be focused on looking for security vulnerabilities, but this is not required.

  Rationale:

  Static source code analysis and dynamic analysis tend to find different kinds of defects (including defects that lead to vulnerabilities), so combining them is more likely to be effective. For example, Linus Torvalds' "Linux 4.14-rc5" announcement (October 15, 2017) notes that "(people are doing) random fuzzing... and it's finding things... Very nice to see."

• It is SUGGESTED that if the software produced by the project includes software written using a memory-unsafe language (e.g., C or C++), then at least one dynamic tool (e.g., a fuzzer or web application scanner) be routinely used in combination with a mechanism to detect memory safety problems such as buffer overwrites. If the project does not produce software written in a memory-unsafe language, choose "not applicable" (N/A). {N/A allowed} ^{[dynamic_analysis_unsafe]}

  Details:

  Examples of mechanisms to detect memory safety problems include Address Sanitizer (ASAN) (available in GCC and LLVM), Memory Sanitizer, and valgrind. Other potentially-used tools include thread sanitizer and undefined behavior sanitizer. Widespread assertions would also work.

• It is SUGGESTED that the project use a configuration for at least some dynamic analysis (such as testing or fuzzing) which enables many assertions. In many cases these assertions should not be enabled in production builds. ^{[dynamic_analysis_enable_assertions]}

  Details:

  This criterion does not suggest enabling assertions during production; that is entirely up to the project and its users to decide. This criterion's focus is instead to improve fault detection during dynamic analysis before deployment. Enabling assertions in production use is completely different from enabling assertions during dynamic analysis (such as testing). In some cases enabling assertions in production use is extremely unwise (especially in high-integrity components). There are many arguments against enabling assertions in production, e.g., libraries should not crash callers, their presence may cause rejection by app stores, and/or activating an assertion in production may expose private data such as private keys. Beware that in many Linux distributions NDEBUG is not defined, so C/C++ assert() will by default be enabled for production in those environments. It may be important to use a different assertion mechanism or defining NDEBUG for production in those environments.

  Rationale:

  Assertions make dynamic analysis more effective, because they increase the number of problems (including vulnerabilities) that dynamic analysis can detect. Other sources also recommend the use of assertions. "Tip #33: If it Can't happen, use assertions to ensure that it won't." ("The Pragmatic Programmer" by Andrew Hunt and David Thomas, p. 122) The paper "Assessing the Relationship between Software Assertions and Code Quality: An Empirical Investigation" by Gunnar Kudrjavets, Nachi Nagappan, and Tom Ball, May 1, 2006, Technical report MSR-TR-2006-54, presented "... an empirical case study of two commercial software components at Microsoft Corporation. The developers of these components systematically employed assertions, which allowed us to investigate the relationship between software assertions and code quality... with an increase in the assertion density in a file there is a statistically significant decrease in fault density. Further, the usage of software assertions in these components found a large percentage of the faults in the bug database."

• All medium and higher severity exploitable vulnerabilities discovered with dynamic code analysis MUST be fixed in a timely way after they are confirmed. {N/A allowed} ^{[dynamic_analysis_fixed]}

  Details:

  If you are not running dynamic code analysis and thus have not found any vulnerabilities in this way, choose "not applicable" (N/A). A vulnerability is considered medium or higher severity if its Common Vulnerability Scoring System (CVSS) base qualitative score is medium or higher. In CVSS versions 2.0 through 3.1, this is equivalent to a CVSS score of 4.0 or higher. Projects may use the CVSS score as published in a widely-used vulnerability database (such as the National Vulnerability Database) using the most-recent version of CVSS reported in that database. Projects may instead calculate the severity themselves using the latest version of CVSS at the time of the vulnerability disclosure, if the calculation inputs are publicly revealed once the vulnerability is publicly known.

Silver

Basics

Prerequisites

• The project MUST achieve a passing level badge. ^{[achieve_passing]}

Basic project website content

• The information on how to contribute MUST include the requirements for acceptable contributions (e.g., a reference to any required coding standard). {Met URL} ^{[contribution_requirements]}

Project oversight

• The project SHOULD have a legal mechanism where all developers of non-trivial amounts of project software assert that they are legally authorized to make these contributions. The most common and easily-implemented approach for doing this is by using a Developer Certificate of Origin (DCO), where users add "signed-off-by" in their commits and the project links to the DCO website. However, this MAY be implemented as a Contributor License Agreement (CLA), or other legal mechanism. {Met URL} ^[dco]

  Details:

  The DCO is the recommended mechanism because it's easy to implement, tracked in the source code, and git directly supports a "signed-off" feature using "commit -s". To be most effective it is best if the project documentation explains what "signed-off" means for that project. A CLA is a legal agreement that defines the terms under which intellectual works have been licensed to an organization or project. A contributor assignment agreement (CAA) is a legal agreement that transfers rights in an intellectual work to another party; projects are not required to have CAAs, since having CAA increases the risk that potential contributors will not contribute, especially if the receiver is a for-profit organization. The Apache Software Foundation CLAs (the individual contributor license and the corporate CLA) are examples of CLAs, for projects which determine that the risks of these kinds of CLAs to the project are less than their benefits.

• The project MUST clearly define and document its project governance model (the way it makes decisions, including key roles). {Met URL} ^[governance]

  Details:

  There needs to be some well-established documented way to make decisions and resolve disputes. In small projects, this may be as simple as "the project owner and lead makes all final decisions". There are various governance models, including benevolent dictator and formal meritocracy; for more details, see Governance models. Both centralized (e.g., single-maintainer) and decentralized (e.g., group maintainers) approaches have been successfully used in projects. The governance information does not need to document the possibility of creating a project fork, since that is always possible for FLOSS projects.

  Rationale:

  There are many different governance models used by a wide array of successful projects. Therefore, we do not believe that we should specify a particular governance model. However, we do think it is important to have a governance model, and clearly define it, so that all participants and potential participants will know how decisions will be made. This was inspired by the OW2 Open-source Maturity Model, in particular RDMP-1 and STK-1.

• The project MUST adopt a code of conduct and post it in a standard location. {Met URL} ^{[code_of_conduct]}

  Details:

  Projects may be able to improve the civility of their community and to set expectations about acceptable conduct by adopting a code of conduct. This can help avoid problems before they occur and make the project a more welcoming place to encourage contributions. This should focus only on behavior within the community/workplace of the project. Example codes of conduct are the Linux kernel code of conduct, the Contributor Covenant Code of Conduct, the Debian Code of Conduct, the Ubuntu Code of Conduct, the Fedora Code of Conduct, the GNOME Code Of Conduct, the KDE Community Code of Conduct, the Python Community Code of Conduct, The Ruby Community Conduct Guideline, and The Rust Code of Conduct.

  Rationale:

  Suggested in issue#608 by Dan Kohn and in the NYC 2016 brainstorm session.

• The project MUST clearly define and publicly document the key roles in the project and their responsibilities, including any tasks those roles must perform. It MUST be clear who has which role(s), though this might not be documented in the same way. {Met URL} ^{[roles_responsibilities]}

  Details:

  The documentation for governance and roles and responsibilities may be in one place.

  Rationale:

  Much knowledge about the project roles builds up over the years, and is not sufficiently passed down to new people. Documenting the roles can help recruit, train, and mentor new project members. Projects may choose document the roles and responsibilities in one place, and identify who has the roles separately, so that the project doesn't need to update the role information when people change roles. The goal is to make underlying assumptions clear.

• The project MUST be able to continue with minimal interruption if any one person dies, is incapacitated, or is otherwise unable or unwilling to continue support of the project. In particular, the project MUST be able to create and close issues, accept proposed changes, and release versions of software, within a week of confirmation of the loss of support from any one individual. This MAY be done by ensuring someone else has any necessary keys, passwords, and legal rights to continue the project. Individuals who run a FLOSS project MAY do this by providing keys in a lockbox and a will providing any needed legal rights (e.g., for DNS names). {Met URL} ^{[access_continuity]}
• The project SHOULD have a "bus factor" of 2 or more. {Met URL} ^[bus_factor]

  Details:

  A "bus factor" (aka "truck factor") is the minimum number of project members that have to suddenly disappear from a project ("hit by a bus") before the project stalls due to lack of knowledgeable or competent personnel. The truck-factor tool can estimate this for projects on GitHub. For more information, see Assessing the Bus Factor of Git Repositories by Cosentino et al.

Documentation

• The project MUST have a documented roadmap that describes what the project intends to do and not do for at least the next year. {Met URL} ^{[documentation_roadmap]}

  Details:

  The project might not achieve the roadmap, and that's fine; the purpose of the roadmap is to help potential users and contributors understand the intended direction of the project. It need not be detailed.

• The project MUST include documentation of the architecture (aka high-level design) of the software produced by the project. If the project does not produce software, select "not applicable" (N/A). {N/A justification} {Met URL} ^{[documentation_architecture]}

  Details:

  A software architecture explains a program's fundamental structures, i.e., the program's major components, the relationships among them, and the key properties of these components and relationships.

  Rationale:

  Documenting the basic design makes it easier for potential new developers to understand its basics. This is related to know_secure_design, as well as implement_secure_design and proposed documentation_security.

• The project MUST document what the user can and cannot expect in terms of security from the software produced by the project (its "security requirements"). {N/A allowed} {Met URL} ^{[documentation_security]}

  Details:

  These are the security requirements that the software is intended to meet.

  Rationale:

  Writing the specification helps the developers think about the interface (including the API) the developers are providing, as well letting any user or researcher know what to expect.

• The project MUST provide a "quick start" guide for new users to help them quickly do something with the software. {N/A justification} {Met URL} ^{[documentation_quick_start]}

  Details:

  The idea is to show users how to get started and make the software do anything at all. This is critically important for potential users to get started.

  Rationale:

  This is based on a conversation with Mike Milinkovich, Executive Director of the Eclipse Foundation, about the OSS project criteria and "what is important". He believes, based on his long experience, that it is critically important that any project have some sort of "quick start" guide to help someone get started and do something with the software; this feeling of accomplishment and demonstration that it works builds understanding and confidence in the user. See issue#645.

• The project MUST make an effort to keep the documentation consistent with the current version of the project results (including software produced by the project). Any known documentation defects making it inconsistent MUST be fixed. If the documentation is generally current, but erroneously includes some older information that is no longer true, just treat that as a defect, then track and fix as usual. {N/A justification} {Met justification} ^{[documentation_current]}

  Details:

  The documentation MAY include information about differences or changes between versions of the software and/or link to older versions of the documentation. The intent of this criterion is that an effort is made to keep the documentation consistent, not that the documentation must be perfect.

  Rationale:

  It's difficult to keep documentation up-to-date, so the criterion is worded this way to make it more practical. Information on differences or changes between versions of the software helps users of older versions and users who are transitioning from older versions.

• The project repository front page and/or website MUST identify and hyperlink to any achievements, including this best practices badge, within 48 hours of public recognition that the achievement has been attained. {Met URL} ^{[documentation_achievements]}

  Details:

  An achievement is any set of external criteria that the project has specifically worked to meet, including some badges. This information does not need to be on the project website front page. A project using GitHub can put achievements on the repository front page by adding them to the README file.

  Rationale:

  Users and potential co-developers need to be able to see what achievements have been attained by a project they are considering using or contributing to. This information can help them determine if they should. In addition, if projects identify their achievements, other projects will be encouraged to follow suit and also make those achievements, benefitting everyone.

Accessibility and internationalization

• The project (both project sites and project results) SHOULD follow accessibility best practices so that persons with disabilities can still participate in the project and use the project results where it is reasonable to do so. {N/A justification} {Met justification} ^{[accessibility_best_practices]}

  Details:

  For web applications, see the Web Content Accessibility Guidelines (WCAG 2.0) and its supporting document Understanding WCAG 2.0; see also W3C accessibility information. For GUI applications, consider using the environment-specific accessibility guidelines (such as Gnome, KDE, XFCE, Android, iOS, Mac, and Windows). Some TUI applications (e.g. `ncurses` programs) can do certain things to make themselves more accessible (such as `alpine`'s `force-arrow-cursor` setting). Most command-line applications are fairly accessible as-is. This criterion is often N/A, e.g., for program libraries. Here are some examples of actions to take or issues to consider:

  • Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language ( WCAG 2.0 guideline 1.1)
  • Color is not used as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element. ( WCAG 2.0 guideline 1.4.1)
  • The visual presentation of text and images of text has a contrast ratio of at least 4.5:1, except for large text, incidental text, and logotypes ( WCAG 2.0 guideline 1.4.3)
  • Make all functionality available from a keyboard (WCAG guideline 2.1)
  • A GUI or web-based project SHOULD test with at least one screen-reader on the target platform(s) (e.g. NVDA, Jaws, or WindowEyes on Windows; VoiceOver on Mac & iOS; Orca on Linux/BSD; TalkBack on Android). TUI programs MAY work to reduce overdraw to prevent redundant reading by screen-readers.

• The software produced by the project SHOULD be internationalized to enable easy localization for the target audience's culture, region, or language. If internationalization (i18n) does not apply (e.g., the software doesn't generate text intended for end-users and doesn't sort human-readable text), select "not applicable" (N/A). {N/A justification} {Met justification} ^{[internationalization]}

  Details:

  Localization "refers to the adaptation of a product, application or document content to meet the language, cultural and other requirements of a specific target market (a locale)." Internationalization is the "design and development of a product, application or document content that enables easy localization for target audiences that vary in culture, region, or language." (See W3C's "Localization vs. Internationalization".) Software meets this criterion simply by being internationalized. No localization for another specific language is required, since once software has been internationalized it's possible for others to work on localization.

  Rationale:

  When software is internationalized, the software can be used by far more people. By itself, that's valuable. In addition, software that can be used by far more people is more likely to lead to larger communities, which increases the likelihood of contributions and reviews.

Other

• If the project sites (website, repository, and download URLs) store passwords for authentication of external users, the passwords MUST be stored as iterated hashes with a per-user salt by using a key stretching (iterated) algorithm (e.g., Argon2id, Bcrypt, Scrypt, or PBKDF2). If the project sites do not store passwords for this purpose, select "not applicable" (N/A). {N/A justification} {Met justification} ^{[sites_password_security]}

  Details:

  Note that the use of GitHub meets this criterion. This criterion only applies to passwords used for authentication of external users into the project sites (aka inbound authentication). If the project sites must log in to other sites (aka outbound authentication), they may need to store authorization tokens for that purpose differently (since storing a hash would be useless). This applies criterion crypto_password_storage to the project sites, similar to sites_https.

Change Control

Previous versions

• The project MUST maintain the most often used older versions of the product or provide an upgrade path to newer versions. If the upgrade path is difficult, the project MUST document how to perform the upgrade (e.g., the interfaces that have changed and detailed suggested steps to help upgrade). {N/A justification} {Met justification} ^{[maintenance_or_update]}

  Rationale:

  This was inspired by DFCT-1.2

Reporting

Bug-reporting process

• The project MUST use an issue tracker for tracking individual issues. {N/A justification} {Met justification} ^{[report_tracker]}

Vulnerability report process

• The project MUST give credit to the reporter(s) of all vulnerability reports resolved in the last 12 months, except for the reporter(s) who request anonymity. If there have been no vulnerabilities resolved in the last 12 months, select "not applicable" (N/A). {N/A justification} {Met URL} ^{[vulnerability_report_credit]}

  Rationale:

  It is only fair to credit those who provide vulnerability reports. In many cases, the only reporter requirement is that they receive credit. This is also important long-term, because giving credit encourages additional reporting. This was recommended in the NYC 2016 brainstorming session.

• The project MUST have a documented process for responding to vulnerability reports. {Met URL} ^{[vulnerability_response_process]}

  Details:

  This is strongly related to vulnerability_report_process, which requires that there be a documented way to report vulnerabilities. It also related to vulnerability_report_response, which requires response to vulnerability reports within a certain time frame.

  Rationale:

  This is inspired by Apache Project Maturity Model QU30.

Quality

Coding standards

• The project MUST identify the specific coding style guides for the primary languages it uses, and require that contributions generally comply with it. {N/A justification} {Met URL} ^{[coding_standards]}

  Details:

  In most cases this is done by referring to some existing style guide(s), possibly listing differences. These style guides can include ways to improve readability and ways to reduce the likelihood of defects (including vulnerabilities). Many programming languages have one or more widely-used style guides. Examples of style guides include Google's style guides and SEI CERT Coding Standards.

• The project MUST automatically enforce its selected coding style(s) if there is at least one FLOSS tool that can do so in the selected language(s). {N/A justification} {Met justification} ^{[coding_standards_enforced]}

  Details:

  This MAY be implemented using static analysis tool(s) and/or by forcing the code through code reformatters. In many cases the tool configuration is included in the project's repository (since different projects may choose different configurations). Projects MAY allow style exceptions (and typically will); where exceptions occur, they MUST be rare and documented in the code at their locations, so that these exceptions can be reviewed and so that tools can automatically handle them in the future. Examples of such tools include ESLint (JavaScript), Rubocop (Ruby), and devtools check (R).

Working build system

• Build systems for native binaries MUST honor the relevant compiler and linker (environment) variables passed in to them (e.g., CC, CFLAGS, CXX, CXXFLAGS, and LDFLAGS) and pass them to compiler and linker invocations. A build system MAY extend them with additional flags; it MUST NOT simply replace provided values with its own. If no native binaries are being generated, select "not applicable" (N/A). {N/A justification} {Met justification} ^{[build_standard_variables]}

  Details:

  It should be easy to enable special build features like Address Sanitizer (ASAN), or to comply with distribution hardening best practices (e.g., by easily turning on compiler flags to do so).

  Rationale:

  See Build system should honor CC, CFLAGS, CXX, CXXFLAGS

• The build and installation system SHOULD preserve debugging information if they are requested in the relevant flags (e.g., "install -s" is not used). If there is no build or installation system (e.g., typical JavaScript libraries), select "not applicable" (N/A). {N/A justification} {Met justification} ^{[build_preserve_debug]}

  Details:

  E.G., setting CFLAGS (C) or CXXFLAGS (C++) should create the relevant debugging information if those languages are used, and they should not be stripped during installation. Debugging information is needed for support and analysis, and also useful for measuring the presence of hardening features in the compiled binaries.

• The build system for the software produced by the project MUST NOT recursively build subdirectories if there are cross-dependencies in the subdirectories. If there is no build or installation system (e.g., typical JavaScript libraries), select "not applicable" (N/A). {N/A justification} {Met justification} ^{[build_non_recursive]}

  Details:

  The project build system's internal dependency information needs to be accurate, otherwise, changes to the project may not build correctly. Incorrect builds can lead to defects (including vulnerabilities). A common mistake in large build systems is to use a "recursive build" or "recursive make", that is, a hierarchy of subdirectories containing source files, where each subdirectory is independently built. Unless each subdirectory is fully independent, this is a mistake, because the dependency information is incorrect.

  Rationale:

  For more information, see "Recursive Make Considered Harmful" by Peter Miller (note that this incorrect approach can be used in any build system, not just make). Note that "Non-recursive Make Considered Harmful" agrees that recursive builds are bad; its argument is that for large projects you should use a tool other than make. In many cases it is better to automatically determine the dependencies, but this is not always accurate or practical, so we did not require that dependencies be automatically generated.

• The project MUST be able to repeat the process of generating information from source files and get exactly the same bit-for-bit result. If no building occurs (e.g., scripting languages where the source code is used directly instead of being compiled), select "not applicable" (N/A). {N/A justification} {Met justification} ^{[build_repeatable]}

  Details:

  GCC and clang users may find the -frandom-seed option useful; in some cases, this can be resolved by forcing some sort order. More suggestions can be found at the reproducible build site.

  Rationale:

  This is a step towards having a reproducible build. This criterion is much easier to meet, because it does not require that external parties be able to reproduce the results - merely that the project can. Supporting full reproducible builds requires that projects provide external parties enough information about their build environment(s), which can be harder to do - so we have split this requirement up.

Installation system

• The project MUST provide a way to easily install and uninstall the software produced by the project using a commonly-used convention. {N/A justification} {Met justification} ^{[installation_common]}

  Details:

  Examples include using a package manager (at the system or language level), "make install/uninstall" (supporting DESTDIR), a container in a standard format, or a virtual machine image in a standard format. The installation and uninstallation process (e.g., its packaging) MAY be implemented by a third party as long as it is FLOSS.

• The installation system for end-users MUST honor standard conventions for selecting the location where built artifacts are written to at installation time. For example, if it installs files on a POSIX system it MUST honor the DESTDIR environment variable. If there is no installation system or no standard convention, select "not applicable" (N/A). {N/A justification} {Met justification} ^{[installation_standard_variables]}

  Rationale:

  This supports capturing the artifacts (e.g., for analysis) without interfering with the build or installation system due to system-wide changes. See DESTDIR honored at install time This doesn't apply when there's no "installation" process, or when POSIX filesystems aren't supported during installation (e.g., Windows-only programs). See Build system should honor CC, CFLAGS, CXX, CXXFLAGS

• The project MUST provide a way for potential developers to quickly install all the project results and support environment necessary to make changes, including the tests and test environment. This MUST be performed with a commonly-used convention. {N/A justification} {Met justification} ^{[installation_development_quick]}

  Details:

  This MAY be implemented using a generated container and/or installation script(s). External dependencies would typically be installed by invoking system and/or language package manager(s), per external_dependencies.

  Rationale:

  Recommended in the NYC 2016 brainstorming session.

Externally-maintained components

• The project MUST list external dependencies in a computer-processable way. {N/A justification} {Met URL} ^{[external_dependencies]}

  Details:

  Typically this is done using the conventions of package manager and/or build system. Note that this helps implement installation_development_quick.

  Rationale:

  Inspired by the NYC 2016 brainstorming session.

• Projects MUST monitor or periodically check their external dependencies (including convenience copies) to detect known vulnerabilities, and fix exploitable vulnerabilities or verify them as unexploitable. {N/A justification} {Met justification} ^{[dependency_monitoring]}

  Details:

  This can be done using an origin analyzer / dependency checking tool / software composition analysis tool such as OWASP's Dependency-Check, Sonatype's Nexus Auditor, Synopsys' Black Duck Software Composition Analysis, and Bundler-audit (for Ruby). Some package managers include mechanisms to do this. It is acceptable if the components' vulnerability cannot be exploited, but this analysis is difficult and it is sometimes easier to simply update or fix the part.

  Rationale:

  This must be monitored or periodically checked, because new vulnerabilities are continuously being discovered.

• The project MUST either:
  1. make it easy to identify and update reused externally-maintained components; or
  2. use the standard components provided by the system or programming language.
  Then, if a vulnerability is found in a reused component, it will be easy to update that component. {N/A justification} {Met justification} ^{[updateable_reused_components]}

  Details:

  A typical way to meet this criterion is to use system and programming language package management systems. Many FLOSS programs are distributed with "convenience libraries" that are local copies of standard libraries (possibly forked). By itself, that's fine. However, if the program *must* use these local (forked) copies, then updating the "standard" libraries as a security update will leave these additional copies still vulnerable. This is especially an issue for cloud-based systems; if the cloud provider updates their "standard" libaries but the program won't use them, then the updates don't actually help. See, e.g., "Chromium: Why it isn't in Fedora yet as a proper package" by Tom Callaway.

  Rationale:

  A very common problem is to have obsolete components with known vulnerabilities. This is OWASP Top 10 (2013) number A9 (using known vulnerable components). See also The Unfortunate Reality of Insecure Libraries.

• The project SHOULD avoid using deprecated or obsolete functions and APIs where FLOSS alternatives are available in the set of technology it uses (its "technology stack") and to a supermajority of the users the project supports (so that users have ready access to the alternative). {N/A justification} {Met justification} ^{[interfaces_current]}

Automated test suite

• An automated test suite MUST be applied on each check-in to a shared repository for at least one branch. This test suite MUST produce a report on test success or failure. {Met justification} ^{[automated_integration_testing]}

  Details:

  This requirement can be viewed as a subset of test_continuous_integration, but focused on just testing, without requiring continuous integration.

  Rationale:

  This is inspired by continuous integration. Continuous integration provides much more rapid feedback on whether or not changes will cause test failures, including regressions. The term "continuous integration" (CI) is defined in Wikipedia as "merging all developer working copies to a shared mainline several times a day". Martin Fowler says that "Continuous Integration is a software development practice where members of a team integrate their work frequently, usually each person integrates at least daily - leading to multiple integrations per day. Each integration is verified by an automated build (including ) to detect integration errors as quickly as possible. Many teams find that this approach leads to significantly reduced integration problems and allows a team to develop cohesive software more rapidly." However, while merging all developer working copies at this pace can be very useful, in practice many projects do not or cannot always do this. In practice, many developers maintain at least some branches that are not merged for longer than a day.

• The project MUST add regression tests to an automated test suite for at least 50% of the bugs fixed within the last six months. {N/A justification} {Met justification} ^{[regression_tests_added50]}

  Rationale:

  Regression tests prevent undetected resurfacing of defects. If a defect has happened before, there is an increased likelihood that it will happen again. We only require 50% of bugs to have regression tests; not all bugs are equally likely to recur, and in some cases it is extremely difficult to build robust tests for them. Thus, there is a diminishing point of return for adding regression tests. The 50% value could be argued as being arbitrary, however, requiring less than 50% would mean that projects could get the badge even if a majority of their bugs in the time frame would not have regression tests. Projects may, of course, choose to have much larger percentages. We choose six months, as with other requirements, so that projects that have done nothing in the past (or recorded nothing in the past) can catch up in a reasonable period of time.

• The project MUST have FLOSS automated test suite(s) that provide at least 80% statement coverage if there is at least one FLOSS tool that can measure this criterion in the selected language. {N/A justification} {Met justification} ^{[test_statement_coverage80]}

  Details:

  Many FLOSS tools are available to measure test coverage, including gcov/lcov, Blanket.js, Istanbul, JCov, and covr (R). Note that meeting this criterion is not a guarantee that the test suite is thorough, instead, failing to meet this criterion is a strong indicator of a poor test suite.

  Rationale:

  Statement coverage is widely used as a test quality measure; it's often a first "starter" measure for test quality. It's well-supported, including by gcov/lcov and codecov.io. Bad test suites could also meet this requirement, but it's generally agreed that any good test suite will meet this requirement, so it provides a useful way to filter out clearly-bad test suites. After all, if your tests aren't even *running* many of the program's statements, you don't have very good tests. Only FLOSS test suites are considered, to ensure that the test suite can be examined and improved over time. A good automated test suite enables rapid response to vulnerability reports. If a vulnerability is reported to a project, the project may be able to quickly repair it, but that is not enough. A good automated test suite is necessary so the project can rapidly gain confidence that the repair doesn't break anything else so it can field the update. It could be argued that anything less than 100% is unacceptable, but this is not a widely held belief. There are many ways to determine if a program is correct - testing is only one of them. Some conditions are hard to create during testing, and the return-on-investment to get those last few percentages is arguably not worth it. The time working to get 100% statement coverage might be much better spent on checking the results more thoroughly (which statement coverage does *not* measure). The 80% suggested here is supported by various sources. The defaults of codecov.io. They define 70% and below as red, 100% as perfectly green, and anything between 70..100 as a range between red and green. This renders ~80% as yellow, and somewhere between ~85% and 90% it starts looking pretty green. The paper "Minimum Acceptable Code Coverage" by Steve Cornett claims, "Code coverage of 70-80% is a reasonable goal for system test of most projects with most coverage metrics. Use a higher goal for projects specifically organized for high testability or that have high failure costs. Minimum code coverage for unit testing can be 10-20% higher than for system testing... Empirical studies of real projects found that increasing code coverage above 70-80% is time consuming and therefore leads to a relatively slow bug detection rate. Your goal should depend on the risk assessment and economics of the project... Although 100% code coverage may appear like a best possible effort, even 100% code coverage is estimated to only expose about half the faults in a system. Low code coverage indicates inadequate testing, but high code coverage guarantees nothing." "TestCoverage" by Martin Fowler (17 April 2012) points out the problems with coverage measures. he states that "Test coverage is a useful tool for finding untested parts of a codebase. Test coverage is of little use as a numeric statement of how good your tests are... The trouble is that high coverage numbers are too easy to reach with low quality testing... If you are testing thoughtfully and well, I would expect a coverage percentage in the upper 80s or 90s. I would be suspicious of anything like 100%... Certainly low coverage numbers, say below half, are a sign of trouble. But high numbers don't necessarily mean much, and lead to ignorance-promoting dashboards."

New functionality testing

• The project MUST have a formal written policy that as major new functionality is added, tests for the new functionality MUST be added to an automated test suite. {N/A justification} {Met justification} ^{[test_policy_mandated]}

  Rationale:

  This ensures that major new functionality is tested. This is related to the criterion test_policy, but is rewritten to be stronger.

• The project MUST include, in its documented instructions for change proposals, the policy that tests are to be added for major new functionality. {N/A justification} {Met justification} ^{[tests_documented_added]}

Warning flags

• Projects MUST be maximally strict with warnings in the software produced by the project, where practical. {N/A justification} {Met justification} ^{[warnings_strict]}

Security

Secure development knowledge

• The project MUST implement secure design principles (from "know_secure_design"), where applicable. If the project is not producing software, select "not applicable" (N/A). {N/A justification} {Met justification} ^{[implement_secure_design]}

  Details:

  For example, the project results should have fail-safe defaults (access decisions should deny by default, and projects' installation should be secure by default). They should also have complete mediation (every access that might be limited must be checked for authority and be non-bypassable). Note that in some cases principles will conflict, in which case a choice must be made (e.g., many mechanisms can make things more complex, contravening "economy of mechanism" / keep it simple).

  Rationale:

  This was inspired by the NYC 2016 brainstorming session.

Use basic good cryptographic practices

• The default security mechanisms within the software produced by the project MUST NOT depend on cryptographic algorithms or modes with known serious weaknesses (e.g., the SHA-1 cryptographic hash algorithm or the CBC mode in SSH). {N/A allowed} {Met justification} ^{[crypto_weaknesses]}

  Rationale:

  SHA-1 has been known to be weak for many years; In February 2017 Google demonstrated a SHA-1 collision. There are a number of alternatives to SHA-1 that are not patent-encumbered, such as the SHA-2 suite (including SHA-256 and SHA-512) and SHA-3. There is some disagreement on how important it is to avoid CBC mode in SSH. The OpenSSH cbc.adv page argues that the attack on SSH CBC is not a practical attack. However, others clearly think it's more important; CERT notes it, as does FAQ: Disable CBC in SSH. It is also easy to use a different mode than CBC; generally when there are safer widely-available options, you should use the safe ones instead. This is a SHOULD, not a MUST; sometimes these weaker mechanisms need to be used for backwards compatibility.

• The project SHOULD support multiple cryptographic algorithms, so users can quickly switch if one is broken. Common symmetric key algorithms include AES, Twofish, and Serpent. Common cryptographic hash algorithm alternatives include SHA-2 (including SHA-224, SHA-256, SHA-384 AND SHA-512) and SHA-3. {N/A allowed} {Met justification} ^{[crypto_algorithm_agility]}

  Rationale:

  The advantage of crypto agility is that if one crypto algorithm is broken, other algorithms can be used instead. Many protocols, including TLS and IPSEC, are specifically designed to support crypto agility. There is disagreement by some experts who argue that this negotiation can itself be a point of attack, and that people should instead simply choose and stay with with one good algorithm. The problem with this position is that no one can be certain about what that "one good algorithm" is; a new attack could be found at any time. See the discussion at Remove requirement for supporting alternative crypto algorithms (crypto_alternatives)?

• The project MUST support storing authentication credentials (such as passwords and dynamic tokens) and private cryptographic keys in files that are separate from other information (such as configuration files, databases, and logs), and permit users to update and replace them without code recompilation. If the project never processes authentication credentials and private cryptographic keys, select "not applicable" (N/A). {N/A allowed} {Met justification} ^{[crypto_credential_agility]}
• The software produced by the project SHOULD support secure protocols for all of its network communications, such as SSHv2 or later, TLS1.2 or later (HTTPS), IPsec, SFTP, and SNMPv3. Insecure protocols such as FTP, HTTP, telnet, SSLv3 or earlier, and SSHv1 SHOULD be disabled by default, and only enabled if the user specifically configures it. If the software produced by the project does not support network communications, select "not applicable" (N/A). {N/A allowed} {Met justification} ^{[crypto_used_network]}
• The software produced by the project SHOULD, if it supports or uses TLS, support at least TLS version 1.2. Note that the predecessor of TLS was called SSL. If the software does not use TLS, select "not applicable" (N/A). {N/A allowed} {Met justification} ^{[crypto_tls12]}
• The software produced by the project MUST, if it supports TLS, perform TLS certificate verification by default when using TLS, including on subresources. If the software does not use TLS, select "not applicable" (N/A). {N/A allowed} {Met justification} ^{[crypto_certificate_verification]}

  Details:

  Note that incorrect TLS certificate verification is a common mistake. For more information, see "The Most Dangerous Code in the World: Validating SSL Certificates in Non-Browser Software" by Martin Georgiev et al. and "Do you trust this application?" by Michael Catanzaro.

• The software produced by the project MUST, if it supports TLS, perform certificate verification before sending HTTP headers with private information (such as secure cookies). If the software does not use TLS, select "not applicable" (N/A). {N/A allowed} {Met justification} ^{[crypto_verification_private]}

Secure release

• The project MUST cryptographically sign releases of the project results intended for widespread use, and there MUST be a documented process explaining to users how they can obtain the public signing keys and verify the signature(s). The private key for these signature(s) MUST NOT be on site(s) used to directly distribute the software to the public. If releases are not intended for widespread use, select "not applicable" (N/A). {N/A justification} {Met justification} ^{[signed_releases]}

  Details:

  The project results include both source code and any generated deliverables where applicable (e.g., executables, packages, and containers). Generated deliverables MAY be signed separately from source code. These MAY be implemented as signed git tags (using cryptographic digital signatures). Projects MAY provide generated results separately from tools like git, but in those cases, the separate results MUST be separately signed.

  Rationale:

  This provides protection from compromised distribution systems. The public key must be accessible so that recipients can check the signature. The private key must not be on sites(s) distributing the software to the public; that way, even if those sites are compromised, the signature cannot be altered. This is sometimes called "code signing". A common way to implement this is by using GPG to sign the code, for example, the GPG keys of every person who signs releases could be in the project README. Node.js implements this via GPG keys in the README, but note that in the criterion we are intentionally more general: Node.js Release Team

• It is SUGGESTED that in the version control system, each important version tag (a tag that is part of a major release, minor release, or fixes publicly noted vulnerabilities) be cryptographically signed and verifiable as described in signed_releases. {Met justification} ^{[version_tags_signed]}

  Rationale:

  This was suggested by Kevin W. Wall (@kwwall)in issue #709.

Other security issues

• The project results MUST check all inputs from potentially untrusted sources to ensure they are valid (an *allowlist*), and reject invalid inputs, if there are any restrictions on the data at all. {N/A justification} {Met justification} ^{[input_validation]}

  Details:

  Note that comparing input against a list of "bad formats" (aka a *denylist*) is normally not enough, because attackers can often work around a denylist. In particular, numbers are converted into internal formats and then checked if they are between their minimum and maximum (inclusive), and text strings are checked to ensure that they are valid text patterns (e.g., valid UTF-8, length, syntax, etc.). Some data may need to be "anything at all" (e.g., a file uploader), but these would typically be rare.

• Hardening mechanisms SHOULD be used in the software produced by the project so that software defects are less likely to result in security vulnerabilities. {N/A justification} {Met justification} ^[hardening]

  Details:

  Hardening mechanisms may include HTTP headers like Content Security Policy (CSP), compiler flags to mitigate attacks (such as -fstack-protector), or compiler flags to eliminate undefined behavior. For our purposes least privilege is not considered a hardening mechanism (least privilege is important, but separate).

• The project MUST provide an assurance case that justifies why its security requirements are met. The assurance case MUST include: a description of the threat model, clear identification of trust boundaries, an argument that secure design principles have been applied, and an argument that common implementation security weaknesses have been countered. {Met URL} ^{[assurance_case]}

  Details:

  An assurance case is "a documented body of evidence that provides a convincing and valid argument that a specified set of critical claims regarding a system’s properties are adequately justified for a given application in a given environment" ("Software Assurance Using Structured Assurance Case Models", Thomas Rhodes et al, NIST Interagency Report 7608). Trust boundaries are boundaries where data or execution changes its level of trust, e.g., a server's boundaries in a typical web application. It's common to list secure design principles (such as Saltzer and Schroeer) and common implementation security weaknesses (such as the OWASP top 10 or CWE/SANS top 25), and show how each are countered. The BadgeApp assurance case may be a useful example. This is related to documentation_security, documentation_architecture, and implement_secure_design.

  Rationale:

  Many sources discuss the rationale for an "assurance case". This was inspired by Security specification and facilitation of bug bounties and by the NYC 2016 brainstorming session.

Analysis

Static code analysis

• The project MUST use at least one static analysis tool with rules or approaches to look for common vulnerabilities in the analyzed language or environment, if there is at least one FLOSS tool that can implement this criterion in the selected language. {N/A justification} {Met justification} ^{[static_analysis_common_vulnerabilities]}

  Rationale:

  We'd like all projects to use this kind of static analysis tool, but there may not be one in the chosen language, or it may only be proprietary (and some developers will therefore not use it).

Dynamic code analysis

• If the software produced by the project includes software written using a memory-unsafe language (e.g., C or C++), then at least one dynamic tool (e.g., a fuzzer or web application scanner) MUST be routinely used in combination with a mechanism to detect memory safety problems such as buffer overwrites. If the project does not produce software written in a memory-unsafe language, choose "not applicable" (N/A). {N/A justification} {Met justification} ^{[dynamic_analysis_unsafe]}

  Rationale:

  This would mean that C/C++ would be required to use something like ASAN during some testing and/or fuzz testing. See: consider giving links to asan/msan/tsan/ubsan and libFuzzer

Gold

Basics

Prerequisites

• The project MUST achieve a silver level badge. ^{[achieve_silver]}

Project oversight

• The project MUST have a "bus factor" of 2 or more. {Met URL} ^[bus_factor]
• The project MUST have at least two unassociated significant contributors. {Met URL} ^{[contributors_unassociated]}

  Details:

  Contributors are associated if they are paid to work by the same organization (as an employee or contractor) and the organization stands to benefit from the project's results. Financial grants do not count as being from the same organization if they pass through other organizations (e.g., science grants paid to different organizations from a common government or NGO source do not cause contributors to be associated). Someone is a significant contributor if they have made non-trivial contributions to the project in the past year. Examples of good indicators of a significant contributor are: written at least 1,000 lines of code, contributed 50 commits, or contributed at least 20 pages of documentation.

  Rationale:

  This reduces the risk of non-support if a single organization stops supporting the project as FLOSS. It also reduces the risk of malicious code insertion, since there is more independence between contributors. This covers the case where "two people work for company X, but only one is paid to work on this project" (because the non-paid person could still have many of the same incentives). It also covers the case where "two people got paid working for Red Cross for a day, but Red Cross doesn't use the project".

Other

• The project MUST include a copyright statement in each source file, identifying the copyright holder (e.g., the [project name] contributors). {Met justification} ^{[copyright_per_file]}

  Details:

  This MAY be done by including the following inside a comment near the beginning of each file: "Copyright the [project name] contributors.". See "Copyright Notices in Open Source Software Projects" by Steve Winslow.

  Rationale:

  This isn't legally required in most jurisdictions, per the Berne Convention. For example, copyright notices have not been required in the US since 1979. On the other hand, this is not hard to add. Ben Balter's "Copyright notices for open source projects" provides some good arguments for why it *should* be included: "First, someone may want to use your work in ways not allowed by your license; notices help them determine who to ask for permission. Explicit notices can help you prove that you and your collaborators really are the copyright holders. They can serve to put a potential infringer on notice by providing an informal sniff test to counter the 'Oh yeah, well I didn’t know it was copyrighted' defense. For some users the copyright notice may suggest higher quality, as they expect that good software will include a notice... Git can track these things, but people may receive software outside of git or where the git history has not been retained." In addition, we have been informed by the Linux Foundation's SPDX community that having this information is extremely valuable for relicensing and for checking to determine if a copyrighted work is derived from another. While version control systems do track versioning within a project, when files are copied between projects this information is often lost. Having the copyright notice information helps those researching sources, e.g., if they wish to try to relicense something.

• The project MUST include a license statement in each source file. This MAY be done by including the following inside a comment near the beginning of each file: SPDX-License-Identifier: [SPDX license expression for project]. {Met justification} ^{[license_per_file]}

  Details:

  This MAY also be done by including a statement in natural language identifying the license. The project MAY also include a stable URL pointing to the license text, or the full license text. Note that the criterion license_location requires the project license be in a standard location. See this SPDX tutorial for more information about SPDX license expressions. Note the relationship with copyright_per_file, whose content would typically precede the license information.

  Rationale:

  Files are sometimes individually copied from one project into another. Per-file license information increases the likelihood that the original license will be honored. SPDX provides a simple standard way to identify common licenses, without having to embed the full license text in each file; since this makes the criterion easier to do, we specifically mention it. Technically, the text after "SPDX-License-Identifier" is a SPDX license expression, not an identifier, but the tag "SPDX-License-Identifier" is what is used for backwards-compatibility.

Change Control

Public version-controlled source repository

• The project's source repository MUST use a common distributed version control software (e.g., git or mercurial). {Met justification} ^{[repo_distributed]}
• The project MUST clearly identify small tasks that can be performed by new or casual contributors. {Met URL} ^{[small_tasks]}

  Details:

  This identification is typically done by marking selected issues in an issue tracker with one or more tags the project uses for the purpose, e.g., up-for-grabs, first-timers-only, "Small fix", microtask, or IdealFirstBug. These new tasks need not involve adding functionality; they can be improving documentation, adding test cases, or anything else that aids the project and helps the contributor understand more about the project.

  Rationale:

  Identified small tasks make it easier for new potential contributors to become involved in a project, and projects with more contributors have an increased likelihood of continuing. Alluxio uses SMALLFIX and OWASP ZAP uses IdealFirstBug. This is related to criterion installation_development_quick.

• The project MUST require two-factor authentication (2FA) for developers for changing a central repository or accessing sensitive data (such as private vulnerability reports). This 2FA mechanism MAY use mechanisms without cryptographic mechanisms such as SMS, though that is not recommended. {Met justification} ^{[require_2FA]}

  Rationale:

  2FA is used by Node.js and the Linux kernel projects. See "Linux Kernel Git Repositories Add 2-Factor Authentication" by Kontin Ryabitsev and "Linux Foundation Protects Kernel Git Repositories With 2FA" by Eduard Kovacs.

• The project's two-factor authentication (2FA) SHOULD use cryptographic mechanisms to prevent impersonation. Short Message Service (SMS) based 2FA, by itself, does NOT meet this criterion, since it is not encrypted. {Met justification} ^[secure_2FA]

  Details:

  A 2FA mechanism that meets this criterion would be a Time-based One-Time Password (TOTP) application that automatically generates an authentication code that changes after a certain period of time. Note that GitHub supports TOTP.

  Rationale:

  SMS is easier and lower cost for many people, but it also provides much weaker security. It has been argued that SMS isn't really 2FA at all; we permit it, because it's better than nothing, but we don't recommend it because of its weaknesses. So Hey You Should Stop Using Texts for Two-Factor Authentication

Quality

Coding standards

• The project MUST document its code review requirements, including how code review is conducted, what must be checked, and what is required to be acceptable. {N/A justification} {Met URL} ^{[code_review_standards]}

  Details:

  See also two_person_review and contribution_requirements.

  Rationale:

  Code review is a cornerstone of quality and secure coding practices. Projects often seek new contributors but lack training and documentation to increase the number of reviewers. An increase in code reviewers lowers maintainer workload while aiding in meeting the badge requirement two_person_review. See issue 699 from GeorgLink.

• The project MUST have at least 50% of all proposed modifications reviewed before release by a person other than the author, to determine if it is a worthwhile modification and free of known issues which would argue against its inclusion {Met justification} ^{[two_person_review]}

  Rationale:

  Review can counter many problems. The percentage here could be changed; 100% would be great but untenable for many projects. We have selected 50%, because anything less than 50% would mean that most changes could go unreviewed. See, for example, the Linux Kernel's "Reviewer's statement of oversight". Note that the set of criteria allow people within the same organization to review each others' work; it is better to require different organizations to review each others' work, but in many situations that is not practical.

Working build system

• The project MUST have a reproducible build. If no building occurs (e.g., scripting languages where the source code is used directly instead of being compiled), select "not applicable" (N/A). {N/A justification} {Met URL} ^{[build_reproducible]}

  Details:

  A reproducible build means that multiple parties can independently redo the process of generating information from source files and get exactly the same bit-for-bit result. In some cases, this can be resolved by forcing some sort order. JavaScript developers may consider using npm shrinkwrap and webpack OccurenceOrderPlugin. GCC and clang users may find the -frandom-seed option useful. The build environment (including the toolset) can often be defined for external parties by specifying the cryptographic hash of a specific container or virtual machine that they can use for rebuilding. The reproducible builds project has documentation on how to do this.

  Rationale:

  If a project needs to be built but there is no working build system, then potential co-developers will not be able to easily contribute and many security analysis tools will be ineffective. Reproduceable builds counter malicious attacks that generate malicious executables, by making it easy to recreate the executable to determine if the result is correct. By itself, reproducible builds do not counter malicious compilers, but they can be extended to counter malicious compilers using processes such as diverse double-compiling (DDC).

Automated test suite

• A test suite MUST be invocable in a standard way for that language. {Met URL} ^{[test_invocation]}
• The project MUST implement continuous integration, where new or changed code is frequently integrated into a central code repository and automated tests are run on the result. {Met URL} ^{[test_continuous_integration]}

  Details:

  In most cases this means that each developer who works full-time on the project integrates at least daily.

  Rationale:

  See Martin Fowler There has been some shift in the meaning of the term continuous integration. Historically the term continuous integration focused on the first part - the frequent integration - and not on its testing. However, over time the emphasis has shifted to include the notion of running automated tests as soon as the code is integrated. This criterion is merely SUGGESTED at passing level. A subset of this criterion is required for passing+1; see automated_integration_testing. Here, we require both the continuous check-in and its testing.

• The project MUST have FLOSS automated test suite(s) that provide at least 90% statement coverage if there is at least one FLOSS tool that can measure this criterion in the selected language. {N/A justification} {Met justification} ^{[test_statement_coverage90]}

  Rationale:

  This increases the statement coverage requirement from the previous badge level, thus requiring even more thorough testing (by this measure).

• The project MUST have FLOSS automated test suite(s) that provide at least 80% branch coverage if there is at least one FLOSS tool that can measure this criterion in the selected language. {N/A justification} {Met justification} ^{[test_branch_coverage80]}

  Rationale:

  This adds another test coverage requirement, again requiring more thorough testing. A program with many one-armed "if" statements could achieve 100% statement coverage but only 50% branch coverage (if the tests only checked the "true" branches). Branch coverage is probably the second most common test coverage measure (after statement coverage), and is often added when a stricter measure of tests is used. Branch coverage is widely (but not universally) implemented.

Security

Use basic good cryptographic practices

• The software produced by the project MUST support secure protocols for all of its network communications, such as SSHv2 or later, TLS1.2 or later (HTTPS), IPsec, SFTP, and SNMPv3. Insecure protocols such as FTP, HTTP, telnet, SSLv3 or earlier, and SSHv1 MUST be disabled by default, and only enabled if the user specifically configures it. If the software produced by the project does not support network communications, select "not applicable" (N/A). {N/A allowed} {Met justification} ^{[crypto_used_network]}
• The software produced by the project MUST, if it supports or uses TLS, support at least TLS version 1.2. Note that the predecessor of TLS was called SSL. If the software does not use TLS, select "not applicable" (N/A). {N/A allowed} {Met justification} ^{[crypto_tls12]}

Secured delivery against man-in-the-middle (MITM) attacks

• The project website, repository (if accessible via the web), and download site (if separate) MUST include key hardening headers with nonpermissive values. {Met URL} ^{[hardened_site]}

  Details:

  Note that GitHub and GitLab are known to meet this. Sites such as https://securityheaders.com/ can quickly check this. The key hardening headers are: Content Security Policy (CSP), HTTP Strict Transport Security (HSTS), X-Content-Type-Options (as "nosniff"), and X-Frame-Options. Fully static web sites with no ability to log in via the web pages could omit some hardening headers with less risk, but there's no reliable way to detect such sites, so we require these headers even if they are fully static sites.

Other security issues

• The project MUST have performed a security review within the last 5 years. This review MUST consider the security requirements and security boundary. {Met justification} ^{[security_review]}

  Details:

  This MAY be done by the project members and/or an independent evaluation. This evaluation MAY be supported by static and dynamic analysis tools, but there also must be human review to identify problems (particularly in design) that tools cannot detect.

  Rationale:

  Security review is important, because security problems often come from subtle interactions of components. Reviewing the system as a whole can help find these problems. Ideally this would be independent, but that often requires a lot of money, and we would rather have some review than none at all. We do not require a specific level of review; this is difficult to quantify given the different environments, requirements, and sizes of various projects. Kevin Wall noted, "If passing+2 is going to be the highest back level, I'd also like to see some sort of mandatory code inspection (possibly SAST assisted), and when applicable, some sort of DAST (for APIs, probably just fuzzing), where failed tests would have to be added to the regression test suite." It's difficult to get agreement on the details of what a security review must include, but we believe that the stated criteria would be agreed on.

• Hardening mechanisms MUST be used in the software produced by the project so that software defects are less likely to result in security vulnerabilities. {N/A justification} {Met URL} ^[hardening]

Analysis

Dynamic code analysis

• The project MUST apply at least one dynamic analysis tool to any proposed major production release of the software produced by the project before its release. {N/A justification} {Met justification} ^{[dynamic_analysis]}

  Rationale:

  Static source code analysis and dynamic analysis tend to find different kinds of defects (including defects that lead to vulnerabilities), so combining them is more likely to be effective.

• The project SHOULD include many run-time assertions in the software it produces and check those assertions during dynamic analysis. {N/A justification} {Met justification} ^{[dynamic_analysis_enable_assertions]}