1 // Copyright 2023 Google LLC 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef ANONYMOUS_TOKENS_CPP_CRYPTO_RSA_SSA_PSS_VERIFIER_H_ 16 #define ANONYMOUS_TOKENS_CPP_CRYPTO_RSA_SSA_PSS_VERIFIER_H_ 17 18 #include <stdint.h> 19 20 #include <memory> 21 #include <optional> 22 23 #include "absl/status/status.h" 24 #include "absl/status/statusor.h" 25 #include "absl/strings/string_view.h" 26 #include "anonymous_tokens/cpp/crypto/crypto_utils.h" 27 #include "anonymous_tokens/cpp/crypto/verifier.h" 28 #include "anonymous_tokens/proto/anonymous_tokens.pb.h" 29 30 namespace anonymous_tokens { 31 32 // RsaSsaPssVerifier is able to verify an unblinded token (signature) against an 33 // inputted message using a public key and other input parameters. 34 class RsaSsaPssVerifier : public Verifier { 35 public: 36 // Passing of public_metadata is optional. If it is set to any value including 37 // an empty string, RsaSsaPssVerifier will assume that partially blind RSA 38 // signature protocol is being executed. 39 // 40 // If public metadata is passed and the boolean "use_rsa_public_exponent" is 41 // set to false, the public exponent in the public_key is not used in any 42 // computations in the protocol. 43 // 44 // Setting "use_rsa_public_exponent" to true is deprecated. All new users 45 // should set it to false. 46 static absl::StatusOr<std::unique_ptr<RsaSsaPssVerifier>> New( 47 int salt_length, const EVP_MD* sig_hash, const EVP_MD* mgf1_hash, 48 const RSAPublicKey& public_key, bool use_rsa_public_exponent, 49 std::optional<absl::string_view> public_metadata = std::nullopt); 50 51 // Verifies the signature. 52 // 53 // Returns OkStatus() on successful verification. Otherwise returns an error. 54 absl::Status Verify(absl::string_view unblind_token, 55 absl::string_view message) override; 56 57 private: 58 // Use `New` to construct 59 RsaSsaPssVerifier(int salt_length, 60 std::optional<absl::string_view> public_metadata, 61 const EVP_MD* sig_hash, const EVP_MD* mgf1_hash, 62 bssl::UniquePtr<RSA> rsa_public_key); 63 64 const int salt_length_; 65 std::optional<std::string> public_metadata_; 66 const EVP_MD* const sig_hash_; // Owned by BoringSSL. 67 const EVP_MD* const mgf1_hash_; // Owned by BoringSSL. 68 69 // If public metadata is passed to RsaSsaPssVerifier::New, rsa_public_key_ 70 // will be initialized using RSA_new_public_key_large_e method. 71 const bssl::UniquePtr<RSA> rsa_public_key_; 72 }; 73 74 } // namespace anonymous_tokens 75 76 #endif // ANONYMOUS_TOKENS_CPP_CRYPTO_RSA_SSA_PSS_VERIFIER_H_ 77