If you discover a security vulnerability in rust-expect, please report it by:

1. Do NOT open a public GitHub issue
2. Use GitHub's private vulnerability reporting feature at Security Advisories
3. Include detailed information about the vulnerability
4. Allow reasonable time for a fix before public disclosure (typically 90 days)

This security policy covers:

• The rust-expect library
• The rust-expect-macros crate
• The rust-pty crate

The pii-redaction feature provides best-effort redaction of sensitive data in logs. It is not a security boundary and should not be relied upon to prevent data leakage in adversarial scenarios.

When using the ssh feature:

• Private keys are handled in memory; ensure proper memory protection
• Credentials should not be logged (even with PII redaction enabled)
• Use agent forwarding or key-based authentication when possible

Status: Unpatched upstream (as of January 2025)

The ssh feature depends on the russh crate, which transitively depends on the rsa crate. The RSA crate has a known timing sidechannel vulnerability (RUSTSEC-2023-0071) that could potentially allow private key recovery through timing analysis in networked environments.

Impact:

• RSA key operations may leak timing information observable over the network
• In theory, this could enable private key recovery by a sophisticated attacker
• Local use on non-compromised systems is generally safe

Mitigation:

• STRONGLY RECOMMENDED: Use Ed25519 keys instead of RSA keys for SSH authentication
• The default credential helper (SshCredentials::with_defaults()) already prioritizes ~/.ssh/id_ed25519 before ~/.ssh/id_rsa
• If you must use RSA keys, avoid using them in environments where attackers can observe network timing

Workaround: Generate and use Ed25519 keys:

ssh-keygen -t ed25519 -C "your_email@example.com"

This issue is tracked upstream in the RustCrypto/RSA repository. We will update our dependencies when a fixed version becomes available.

By default, rust-expect uses HostKeyVerification::KnownHosts which validates SSH server keys against the user's ~/.ssh/known_hosts file. This prevents man-in-the-middle attacks.

The HostKeyVerification::AcceptAll variant (which disables host key verification) is gated behind the insecure-skip-verify feature flag. This flag is:

• NOT included in the full feature bundle
• NOT recommended for production use
• ONLY intended for controlled testing environments

To enable it (at your own risk):

[dependencies]
rust-expect = { version = "0.1", features = ["ssh", "insecure-skip-verify"] }

PTY operations run with the privileges of the calling process. Be cautious when:

• Spawning processes with elevated privileges
• Handling user-provided input
• Logging session content

1. Keep dependencies updated
2. Use cargo audit regularly
3. Review session logs before sharing
4. Use environment variables for sensitive configuration
5. Run tests in isolated environments