support quick seach jwk by kid

[wbpcode]

Now we will try to iterate all the jwks to find a matched jwk and then verify it. Can we create a hash table based on the kid? And if kid of jwt is not empty, we can try a quick search first before the iteration?

Status verifyJwtWithoutTimeChecking(const Jwt& jwt, const Jwks& jwks) {
  // Verify signature
  std::string signed_data =
      jwt.header_str_base64url_ + '.' + jwt.payload_str_base64url_;[Wayne Zhang, 4 years ago: • Initial code](https://sourcegraph.com/github.com/google/jwt_verify_lib/-/commit/d856e7692ce470a961ac15d635570ac5379036f3)
  bool kid_alg_matched = false;
  for (const auto& jwk : jwks.keys()) {
    // If kid is specified in JWT, JWK with the same kid is used for
    // verification.
    // If kid is not specified in JWT, try all JWK.
    if (!jwt.kid_.empty() && !jwk->kid_.empty() && jwk->kid_ != jwt.kid_) {
      continue;
    }

    // The same alg must be used.
    if (!jwk->alg_.empty() && jwk->alg_ != jwt.alg_) {
      continue;
    }
    kid_alg_matched = true;

    if (jwk->kty_ == "EC") {
      const EVP_MD* md;
      if (jwt.alg_ == "ES384") {
        md = EVP_sha384();
      } else if (jwt.alg_ == "ES512") {
        md = EVP_sha512();
      } else {
        // default to SHA256
        md = EVP_sha256();
      }

      if (verifySignatureEC(jwk->ec_key_.get(), md, jwt.signature_,
                            signed_data)) {
        // Verification succeeded.
        return Status::Ok;
      }
    } else if (jwk->kty_ == "RSA") {
      const EVP_MD* md;
      if (jwt.alg_ == "RS384" || jwt.alg_ == "PS384") {
        md = EVP_sha384();
      } else if (jwt.alg_ == "RS512" || jwt.alg_ == "PS512") {
        md = EVP_sha512();
      } else {
        // default to SHA256
        md = EVP_sha256();
      }

      if (jwt.alg_.compare(0, 2, "RS") == 0) {
        if (verifySignatureRSA(jwk->rsa_.get(), md, jwt.signature_,
                               signed_data)) {
          // Verification succeeded.
          return Status::Ok;
        }
      } else if (jwt.alg_.compare(0, 2, "PS") == 0) {
        if (verifySignatureRSAPSS(jwk->rsa_.get(), md, jwt.signature_,
                                  signed_data)) {
          // Verification succeeded.
          return Status::Ok;
        }
      }
    } else if (jwk->kty_ == "oct") {
      const EVP_MD* md;
      if (jwt.alg_ == "HS384") {
        md = EVP_sha384();
      } else if (jwt.alg_ == "HS512") {
        md = EVP_sha512();
      } else {
        // default to SHA256
        md = EVP_sha256();
      }

      if (verifySignatureOct(jwk->hmac_key_, md, jwt.signature_, signed_data)) {
        // Verification succeeded.
        return Status::Ok;
      }
    } else if (jwk->kty_ == "OKP" && jwk->crv_ == "Ed25519") {
      Status status = verifySignatureEd25519(jwk->okp_key_raw_, jwt.signature_,
                                             signed_data);
      // For verification failures keep going and try the rest of the keys in
      // the JWKS. Otherwise status is either OK or an error with the JWT and we
      // can return immediately.
      if (status == Status::Ok ||
          status == Status::JwtEd25519SignatureWrongLength) {
        return status;
      }
    }
  }

  // Verification failed.
  return kid_alg_matched ? Status::JwtVerificationFail
                         : Status::JwksKidAlgMismatch;
}

[wbpcode]

If the community thinks the work is worthwhile, I can give it a try.

[qiwzhang]

In my view, such optimization is not very useful. JWKS is very small with only a few "kid" in general. If you can proof to me that there are many production JWKS with large amount of kids, then please go ahead with such optimization.

[wbpcode]

@qiwzhang
In our new gateway, we may create a jwk for every consumer which result in large amount of kids.
In this way, we can manage consumer authentication in a more granular and flexible way. For example, if a consumer's token is leaked, we can immediately invalidate the token by disabling the corresponding jwk, rather than waiting until the token expires itself.

And I think this optimisation should be very simple.

[qiwzhang]

I see. It makes sense. Please go ahead.