net/ssl/ssl_platform_key_android.cc

// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "net/ssl/ssl_platform_key_android.h"

#include <strings.h>

#include <memory>
#include <utility>
#include <vector>

#include "base/android/scoped_java_ref.h"
#include "base/containers/flat_set.h"
#include "base/logging.h"
#include "net/android/keystore.h"
#include "net/base/net_errors.h"
#include "net/ssl/ssl_platform_key_util.h"
#include "net/ssl/threaded_ssl_private_key.h"
#include "third_party/abseil-cpp/absl/types/optional.h"
#include "third_party/boringssl/src/include/openssl/ecdsa.h"
#include "third_party/boringssl/src/include/openssl/evp.h"
#include "third_party/boringssl/src/include/openssl/mem.h"
#include "third_party/boringssl/src/include/openssl/nid.h"
#include "third_party/boringssl/src/include/openssl/rsa.h"
#include "third_party/boringssl/src/include/openssl/ssl.h"

using base::android::JavaRef;
using base::android::ScopedJavaGlobalRef;

namespace net {

namespace {

const char* GetJavaAlgorithm(uint16_t algorithm) {
  switch (algorithm) {
    case SSL_SIGN_RSA_PKCS1_SHA1:
      return "SHA1withRSA";
    case SSL_SIGN_RSA_PKCS1_SHA256:
      return "SHA256withRSA";
    case SSL_SIGN_RSA_PKCS1_SHA384:
      return "SHA384withRSA";
    case SSL_SIGN_RSA_PKCS1_SHA512:
      return "SHA512withRSA";
    case SSL_SIGN_ECDSA_SHA1:
      return "SHA1withECDSA";
    case SSL_SIGN_ECDSA_SECP256R1_SHA256:
      return "SHA256withECDSA";
    case SSL_SIGN_ECDSA_SECP384R1_SHA384:
      return "SHA384withECDSA";
    case SSL_SIGN_ECDSA_SECP521R1_SHA512:
      return "SHA512withECDSA";
    case SSL_SIGN_RSA_PSS_SHA256:
      return "SHA256withRSA/PSS";
    case SSL_SIGN_RSA_PSS_SHA384:
      return "SHA384withRSA/PSS";
    case SSL_SIGN_RSA_PSS_SHA512:
      return "SHA512withRSA/PSS";
    default:
      return nullptr;
  }
}

// Java's public-key encryption algorithms are mis-named. It incorrectly
// classifies RSA's "mode" as ECB.
const char kRSANoPadding[] = "RSA/ECB/NoPadding";

class SSLPlatformKeyAndroid : public ThreadedSSLPrivateKey::Delegate {
 public:
  SSLPlatformKeyAndroid(bssl::UniquePtr<EVP_PKEY> pubkey,
                        const JavaRef<jobject>& key)
      : pubkey_(std::move(pubkey)),
        provider_name_(android::GetPrivateKeyClassName(key)) {
    key_.Reset(key);

    absl::optional<bool> supports_rsa_no_padding;
    for (uint16_t algorithm : SSLPrivateKey::DefaultAlgorithmPreferences(
             EVP_PKEY_id(pubkey_.get()), true /* include PSS */)) {
      const char* java_algorithm = GetJavaAlgorithm(algorithm);
      if (java_algorithm &&
          android::PrivateKeySupportsSignature(key_, java_algorithm)) {
        preferences_.push_back(algorithm);
      } else if (SSL_is_signature_algorithm_rsa_pss(algorithm)) {
        // Check if we can use the fallback path instead.
        if (!supports_rsa_no_padding) {
          supports_rsa_no_padding =
              android::PrivateKeySupportsCipher(key_, kRSANoPadding);
        }
        if (*supports_rsa_no_padding) {
          preferences_.push_back(algorithm);
          use_pss_fallback_.insert(algorithm);
        }
      }
    }
  }

  SSLPlatformKeyAndroid(const SSLPlatformKeyAndroid&) = delete;
  SSLPlatformKeyAndroid& operator=(const SSLPlatformKeyAndroid&) = delete;

  ~SSLPlatformKeyAndroid() override = default;

  std::string GetProviderName() override { return provider_name_; }

  std::vector<uint16_t> GetAlgorithmPreferences() override {
    return preferences_;
  }

  Error Sign(uint16_t algorithm,
             base::span<const uint8_t> input,
             std::vector<uint8_t>* signature) override {
    if (use_pss_fallback_.contains(algorithm)) {
      return SignPSSFallback(algorithm, input, signature);
    }

    const char* java_algorithm = GetJavaAlgorithm(algorithm);
    if (!java_algorithm) {
      LOG(ERROR) << "Unknown algorithm " << algorithm;
      return ERR_SSL_CLIENT_AUTH_SIGNATURE_FAILED;
    }
    if (!android::SignWithPrivateKey(key_, java_algorithm, input, signature)) {
      LOG(ERROR) << "Could not sign message with private key!";
      return ERR_SSL_CLIENT_AUTH_SIGNATURE_FAILED;
    }
    return OK;
  }

 private:
  Error SignPSSFallback(uint16_t algorithm,
                        base::span<const uint8_t> input,
                        std::vector<uint8_t>* signature) {
    const EVP_MD* md = SSL_get_signature_algorithm_digest(algorithm);
    uint8_t digest[EVP_MAX_MD_SIZE];
    unsigned digest_len;
    if (!EVP_Digest(input.data(), input.size(), digest, &digest_len, md,
                    nullptr)) {
      return ERR_SSL_CLIENT_AUTH_SIGNATURE_FAILED;
    }

    absl::optional<std::vector<uint8_t>> padded =
        AddPSSPadding(pubkey_.get(), md, base::make_span(digest, digest_len));
    if (!padded) {
      return ERR_SSL_CLIENT_AUTH_SIGNATURE_FAILED;
    }

    if (!android::EncryptWithPrivateKey(key_, kRSANoPadding, *padded,
                                        signature)) {
      return ERR_SSL_CLIENT_AUTH_SIGNATURE_FAILED;
    }
    return OK;
  }

  bssl::UniquePtr<EVP_PKEY> pubkey_;
  ScopedJavaGlobalRef<jobject> key_;
  std::string provider_name_;
  std::vector<uint16_t> preferences_;
  base::flat_set<uint16_t> use_pss_fallback_;
};

}  // namespace

scoped_refptr<SSLPrivateKey> WrapJavaPrivateKey(
    const X509Certificate* certificate,
    const JavaRef<jobject>& key) {
  bssl::UniquePtr<EVP_PKEY> pubkey = GetClientCertPublicKey(certificate);
  if (!pubkey)
    return nullptr;

  return base::MakeRefCounted<ThreadedSSLPrivateKey>(
      std::make_unique<SSLPlatformKeyAndroid>(std::move(pubkey), key),
      GetSSLPlatformKeyTaskRunner());
}

std::vector<std::string> SignatureAlgorithmsToJavaKeyTypes(
    base::span<const uint16_t> algorithms) {
  std::vector<std::string> key_types;
  bool has_rsa = false, has_ec = false;
  for (uint16_t alg : algorithms) {
    switch (SSL_get_signature_algorithm_key_type(alg)) {
      case EVP_PKEY_RSA:
        if (!has_rsa) {
          // https://developer.android.com/reference/android/security/keystore/KeyProperties#KEY_ALGORITHM_RSA
          key_types.push_back("RSA");
          has_rsa = true;
        }
        break;
      case EVP_PKEY_EC:
        if (!has_ec) {
          // https://developer.android.com/reference/android/security/keystore/KeyProperties#KEY_ALGORITHM_EC
          key_types.push_back("EC");
          has_ec = true;
        }
        break;
    }
  }
  return key_types;
}

}  // namespace net