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polyjose

Swift package

This page has the details of the polyjose Swift package that you don’t need to get started: what printing a record shows, how to wipe secret results, and which copies of secrets stay in memory. To install it and sign your first token, see Get started in Swift.

Secrets in records

Section titled “Secrets in records”

  • Printing redacts secret fields. String(describing:), String(reflecting:), string interpolation, print, debugPrint and dump show a secret field’s length only: <redacted, N chars> for a String, <redacted, N bytes> for a Data, and nil when it is absent. The other fields print as usual. The redacted fields are:

    • JwsSigner.key and JweRecipient.key
    • JwsVerified.payload and JwsVerifyOptions.detachedPayload
    • JweDecrypted.plaintext and aad
    • JweEncryptOptions.aad; its recipients print redacted too.

    The package’s own Redaction.swift does this; the generated Polyjose.swift is unchanged.

  • Reading a field still gives the secret. Only the printed form changes, so don’t log a field itself.

  • JWT claims are not redacted (JwtVerified.claims, also inside JwtNestedVerified). Put secrets in a JWE payload, not in claims.

  • Wipe returned Data when you are done with it. For example, result.payload.resetBytes(in: result.payload.indices) on a var. Data is copy-on-write, so this wipes the bytes only if no other copy shares them; wiping a copy leaves the original. Swift Strings, such as keys and JWKs, can’t be wiped.

  • Wiping returned Data doesn’t remove every copy. The generated Polyjose.swift copies secret inputs (keys, payloads, plaintexts, aad, detachedPayload) and secret outputs (payload, plaintext, aad) through temporary Swift arrays, and frees them without wiping them. The Rust side of the call leaves unwiped copies on its own heap too, as the Kotlin library does, through the same generated interface layer. Your wipe reaches only the Data you hold. Reading the freed memory needs access to your app’s process (a debugger, a core dump or a jailbroken device).

Secrets in memory covers what every platform does with secrets.