Redact secrets before writing logs

Build a safe record

Prefer an allowlist such as operation, status, duration and correlation_id. Do not serialize the whole request and attempt to remove secrets afterward. OWASP identifies access tokens, passwords and connection strings among data that should not be directly logged.

Boundary procedure

Remove authorization headers, cookies, credential-bearing query parameters and sensitive nested fields before the record reaches a logger, exception formatter or telemetry exporter. Bound string lengths and neutralize control characters where the log format requires it. Avoid logging request or response bodies by default.

Test with a canary secret

Use a synthetic marker, never a real credential. Pass it through a successful request, validation failure, timeout and unhandled-exception fixture. Capture application logs, transport debug output and telemetry. Assert that the marker is absent from all outputs, including nested error messages.

Failure handling and limits

If an actual credential was logged, stop further exposure and follow the credential owner's rotation and incident procedure. Redacting future records does not remove earlier copies. Hashing a low-entropy secret does not necessarily anonymize it. Redaction reduces exposure, but access controls and retention limits are still required for the remaining diagnostic data.