Freebird is pre-1.0 software. Treat public deployments as experimental unless you have reviewed the code, configuration, and operational controls for your own threat model.

Use GitHub private vulnerability reporting for this repository if it is available. If private reporting is not available, open a public issue asking the maintainers for a private security contact and do not include exploit details, secrets, logs, or proof-of-concept code in the public issue.

Useful reports include:

• affected commit or release
• deployment mode and relevant feature flags
• reproduction steps
• expected and actual behavior
• whether the issue affects issuer, verifier, client SDK, admin routes, or deployment assets

Until tagged stable releases exist, security fixes target the main development branch. Operators should pin a reviewed commit and update deliberately after reading the changelog or commit diff.

Freebird separates three concerns:

• token issuance: the issuer evaluates blinded client requests
• token redemption: the verifier checks and consumes finalized tokens
• admission control: optional Sybil-resistance gates decide who may request issuance

The privacy property is about unlinking issuance from redemption. Sybil resistance is configurable and local to the issuer. A weak or disabled Sybil mode means tokens may be easy to farm even if the token cryptography works.

• The project has not had an external security audit.
• SYBIL_RESISTANCE=none is for local testing or fully trusted issuers only.
• In-memory verifier nullifier storage rejects replay only until the verifier restarts. Use Redis for public deployments.
• Sybil proof replay protection for proof-of-work, WebAuthn gate proofs, and multi-party vouching defaults to process-local memory. Use SYBIL_REPLAY_STORE=redis for restart-safe and multi-instance issuer deployments.
• combined mode with SYBIL_COMBINED_MODE=or is only as strong as the easiest configured mechanism to satisfy.
• WebAuthn attestation is not automatic. It must be enabled and configured with WEBAUTHN_REQUIRE_ATTESTATION, WEBAUTHN_ATTESTATION_POLICY, and, where appropriate, WEBAUTHN_ALLOWED_AAGUIDS.
• Admin APIs rely on ADMIN_API_KEY or an admin session cookie. Public deployments should put admin routes behind TLS, network policy, and a reverse proxy or VPN boundary.
• Audit logs are operational records, not tamper-evident security logs.

The following narrowly scoped exceptions are temporary maintainer-approved compatibility decisions; they are not security sign-offs and do not waive any other RustSec advisory:

• RUSTSEC-2023-0071 (rsa) is currently reached through blind-rsa-signatures. It is temporarily excepted from the CI cargo audit exit check while the blind-RSA/RSA implementation is migrated and reviewed. A crypto migration is required; this exception must be removed when that migration is available and validated, or sooner if the risk or dependency path changes.
• RUSTSEC-2024-0436 (paste) is reached only through the optional freebird-crypto/pkcs11 feature and cryptoki 0.6. This is a temporary compatibility exception: the feature is excluded by default and the advisory remains visible in audit output. Upgrade work requires compilation and real HSM (or equivalent SoftHSM) validation before it is accepted. The exception expires when that validation-backed upgrade is completed, or must be revisited sooner if PKCS#11 becomes part of a release build.

CI ignores only RUSTSEC-2023-0071. These exceptions do not suppress warnings, yanked-package checks, or any other advisory.

For an internet-exposed issuer or verifier:

• set REQUIRE_TLS=true
• set a high-entropy ADMIN_API_KEY
• use Redis for verifier nullifier storage
• use SYBIL_REPLAY_STORE=redis for issuer Sybil proof replay protection
• use protected persistent storage for issuer key material and Sybil state
• avoid SYBIL_RESISTANCE=none
• document which Sybil mode is configured and what it does not prevent
• keep admin routes off the public internet where possible

See also:

• Profile and Claim Matrix for the authoritative status of planned issuance profiles and limits on profile claims
• Architecture
• Threat Model
• Sybil Modes
• Audit Logging