OpenSSF Best Practices
The Open Source Security Foundation (OpenSSF) provides a list of best practices for open source projects. Although this list is tailored towards free and open source projects, I believe that this list is valuable for all software projects. Here's a breakdown of all practices that I consider generic to all projects, no matter its license, alongside some personal notes.
Basic project website content
The project website MUST succinctly describe what the software does (what problem does it solve?).
A website might not always apply, but a README is a good place to put this information.
The information on how to contribute MUST explain the contribution process (e.g., are pull requests used?)
This information is also best placed in the README.
The information on how to contribute SHOULD include the requirements for acceptable contributions (e.g., a reference to any required coding standard)
The project MUST provide basic documentation for the software produced by the project.
The project MUST provide reference documentation that describes the external interface (both input and output) of the software produced by the project.
I wouldn't consider reference documentation a requirement, but it's nice to have.
The project sites (website, repository, and download URLs) MUST support HTTPS using TLS.
Public version-controlled source repository
The project MUST have a version-controlled source repository
that is publicly readable and has a URL.
The project's source repository MUST track what changes were made, who made the changes, and when the changes were made.
To enable collaborative review, the project's source repository MUST include interim versions for review between releases; it MUST NOT include only final releases.
In some cases, code can't or shouldn't be versioned. For most website projects, review environments in merge requests (Vercel, Netlify, GitLab) could be considered.
It is SUGGESTED that common distributed version control software be used (e.g., git) for the project's source repository.
Unique version numbering
The project results MUST have a unique version identifier for each release intended to be used by users.
Commit hashes can be used as unique version numbers in some cases.
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.
As mentioned above, projects that are constantly in motion (e.g. darktheme.club) might want to consider using commit hashes for version numbers instead.
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.
Git tags are often neglected during development, but can be very useful.
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".
I wrote a post about changelogs a while back.
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.
Vulnerability report process
If private vulnerability reports are supported, the project MUST include how to send the information in a way that is kept private.
For proprietary projects, it's often a good idea to have a public "Report an issue" feature.
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.
It is SUGGESTED that common tools be used for building the software.
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).
A test suite SHOULD be invocable in a standard way for that language.
npm run test,
cargo test, etc.
It is SUGGESTED that the test suite cover most (or ideally all) the code branches, input fields, and functionality.
Write tests if they are useful, not for the sake of having 100% test coverage.
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).
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.
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.
This is often covered if you have a CI pipeline.
It is SUGGESTED that this policy on adding tests (see test_policy) be documented in the instructions for change proposals.
Consider adding a checkbox to your merge request template. For reference, here's a checklist that I often use in templates:
# Checklist: - [ ] documented in the changelog - [ ] sufficiently tested - [ ] sufficiently documented
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.
The project MUST address warnings.
Ensure this by disallowing warnings in your CI pipeline.
It is SUGGESTED that projects be maximally strict with warnings in the software produced by the project, where practical.
Secure development knowledge
The project MUST have at least one primary developer who knows how to design secure software.
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.
Easier said than done, but be vocal if you're hesitant towards a feature or implementation path.
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).
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.
Don't reinvent the wheel. Not just for cryptography.
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.
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.
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).
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.
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).
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.
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.
A cryptographic hash (e.g., a sha1sum) MUST NOT be retrieved over http and used without checking for a cryptographic signature.
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.
This can be ensured using Dependabot or Renovate
Projects SHOULD fix all critical vulnerabilities rapidly after they are reported.
Again, use automatic dependency updating mechanisms for this.
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.
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.
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.
All medium and higher severity exploitable vulnerabilities discovered with static code analysis MUST be fixed in a timely way after they are confirmed.
It is SUGGESTED that static source code analysis occur on every commit or at least daily.
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.
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.
This is often overlooked.
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.
All medium and higher severity exploitable vulnerabilities discovered with dynamic code analysis MUST be fixed in a timely way after they are confirmed.
This is post 046 of #100DaysToOffload.