Providers and crypto options

The compact jose.jws/sign and verify functions accept :provider and :secure-random. A provider is either a java.security.Provider or :bouncy-castle / :bouncy-castle-fips; the latter names are resolved through Nimbus' provider singletons. JWE encrypt and decrypt accept the same options, plus :key-encryption-provider, :content-encryption-provider, and :mac-provider when those cryptographic operations need separate providers.

JWS signing also accepts :allow-weak-rsa-key? and :user-authentication-required? where Nimbus' signer constructors support those options. JWE encryption accepts :cipher-mode (:wrap-unwrap or :encrypt-decrypt), and JWE decryption accepts that option, :allow-weak-rsa-key?, and :max-compressed-length. The latter bounds the compressed ciphertext length Nimbus will expand while processing a :zip JWE; set it explicitly when the default limit is not appropriate.

The provider options make FIPS and hardware-provider deployments possible without changing the process-wide JCA provider order. The FIPS singleton is optional; if its classes are unavailable, jose-clj reports :missing-optional-dep.

When :user-authentication-required? true is supplied to JWS signing with an RSA or EC key, jose-clj returns a deferred-signing map containing the initialized java.security.Signature and a :complete function. The caller may authenticate through its environment and invoke :complete to obtain the finished compact JWS. Nimbus' RSASSASigner and ECDSASigner implement this through anonymous CompletableJWSObjectSigning classes; Nimbus signals the pause with ActionRequiredForJWSCompletionException and the completion object produces the signature.