fix(gateway): persist pairing tokens with atomic replace - #71
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auth_pair truncated auth_tokens.json in place and ignored write errors, so ENOSPC, a crash after O_TRUNC, or fdopen failure could wipe every device token and still return success with a token that never landed on disk. Write to a sibling temp file, fsync, then rename. Keep the pairing code until the store is committed so a failed pair can be retried. Co-authored-by: esadrianno <[email protected]>
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Bug and impact
auth_pairopenedauth_tokens.jsonwithO_TRUNCand ignoredfprintf/fcloseerrors. A disk-full write, crash after truncate, orfdopenfailure afteropen()emptied (or partially wrote) the token store and still returned success with a bearer token that never landed on disk.Concrete trigger: pairing is in progress, tokens already exist on disk (second device in the append window, or a prior successful pair), then the write hits
ENOSPC/EFBIG. Existing devices stop authenticating. If the leftover file is non-empty invalid JSON,auth_get_or_create_pairing_codewill not issue a new code, so the gateway stays locked until the file is deleted by hand.Root cause
In-place truncate-then-write with unchecked stdio, plus clearing the pairing code after a write that may have failed.
Fix
Write JSON to
auth_tokens.json.tmp,fsync, thenrenameover the live file (same pattern as dashboard config save). Checkgenerate_random_hex. Keep the pending pairing code until the store commit succeeds so a failed pair can be retried.Validation
CI=true make test_auth(includes-Werror). New regressiontest_auth_pair_write_failure_preserves_existing_tokensusesRLIMIT_FSIZEto fail the write, asserts the existing token still validates, then retries successfully after the limit is restored.