Security

Security

Read the main repository's security policy before reporting a vulnerability.

Rules that must stay true

• IDMUX_SESSION never contains a clear IdP session ID.
• AES-256-GCM encrypts and authenticates the complete client state.
• Every encryption uses a fresh random nonce.
• The encryption key is never logged or returned in a response.
• Session cookies are HttpOnly, Secure, and SameSite=Lax or Strict.
• IDMUX_SESSION is never forwarded to the IdP.
• An upstream request contains zero or one IdP identity cookie.
• authuser=new sends no IdP identity cookie upstream.
• Logout removes only the selected session slot.
• Invalid input returns a safe response and never causes a panic.
• Logs never contain cookie values, keys, tokens, or IdP session IDs.

Key rotation

Use IDMUX_ENCRYPTION_KEY for the new key and IDMUX_ENCRYPTION_KEY_PREVIOUS for old keys during a planned rotation. Remove old keys only after old cookies have expired.

Do not share secrets

Never add real cookies, tokens, keys, customer data, or production logs to a wiki page, issue, pull request, or commit.