docs(auth): explain why MCP OAuth secrets/tokens aren't app-encrypted#2968
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docs(auth): explain why MCP OAuth secrets/tokens aren't app-encrypted#2968tofikwest wants to merge 2 commits into
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Replaces the breaking attempt to set `storeClientSecret: 'encrypted'` (cubic P1 on PR #2956) with a warning comment. That option would have broken the Gram OAuth flow: better-auth verifies every confidential client through the same decrypt/hash path, including config `trustedClients` whose secret is the plaintext GRAM_OAUTH_CLIENT_SECRET, so verification would fail (`invalid_client`). There is also nothing to encrypt: the Gram client is config-only and DCR is disabled, so no client secrets are persisted to `oauth_application`. The `accessToken`/`refreshToken` in `oauth_access_token` are generated and looked up by raw value by better-auth, so they can't be hashed/encrypted at our layer without breaking token validation; they rely on DB encryption-at-rest + short TTLs. Net: no safe app-level fix exists; documented to prevent re-introduction. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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TL;DR
My first attempt (
storeClientSecret: 'encrypted') would have broken the Gram OAuth flow — caught in review. This PR replaces it with a warning comment only (zero behavior change). The honest finding: cubic's P1 has no safe app-level fix for our setup.Why
storeClientSecretbreaks thingsVerified in the locked better-auth 1.4.22 source:
getClient()returns a configtrustedClientdirectly, withclientSecret= the plaintextGRAM_OAUTH_CLIENT_SECRET.verifyStoredClientSecret()for every confidential client — no trusted-client bypass.'encrypted', that doessymmetricDecrypt(plaintext_config_secret) === presented→ fails/throws →invalid_client.'hashed'fails identically.Why there's nothing to encrypt anyway
trustedClient(secret in env, never in the DB).oauth_applicationhas no rows. No client secrets are persisted.The access/refresh tokens (what cubic pointed at)
oauth_access_token.accessToken/refreshTokenare generated and looked up by raw value by better-auth, so they can't be hashed/encrypted at our layer without breaking token validation. They rely on DB encryption-at-rest + short access-token TTLs.What this PR does
Leaves a comment in
auth.server.tsdocumenting all of the above, so nobody (human or bot) re-introduces the breakingstoreClientSecretchange. No code behavior changes.Alternative: if a doc-only PR isn't wanted, close this — the knowledge is captured here and in the investigation.
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