Cast device revocation checking.

components/cast_certificate/cast_crl.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/cast_certificate/cast_crl.h"
+
+#include <unordered_map>
+#include <unordered_set>
+
+#include "base/base64.h"
+#include "base/memory/ptr_util.h"
+#include "base/memory/singleton.h"
+#include "components/cast_certificate/proto/revocation.pb.h"
+#include "crypto/sha2.h"
+#include "net/cert/internal/parse_certificate.h"
+#include "net/cert/internal/parsed_certificate.h"
+#include "net/cert/internal/path_builder.h"
+#include "net/cert/internal/signature_algorithm.h"
+#include "net/cert/internal/signature_policy.h"
+#include "net/cert/internal/trust_store.h"
+#include "net/cert/internal/verify_certificate_chain.h"
+#include "net/cert/internal/verify_signed_data.h"
+#include "net/cert/x509_certificate.h"
+#include "net/der/encode_values.h"
+#include "net/der/input.h"
+#include "net/der/parser.h"
+#include "net/der/parse_values.h"
+
+namespace cast_certificate {
+namespace {
+
+enum CrlVersion {
+  // version 0: Spki Hash Algorithm = SHA-256
+  //            Signature Algorithm = RSA-PKCS1 V1.5 with SHA-256
+  CRL_VERSION_0 = 0,
+};
+
+// -------------------------------------------------------------------------
+// Cast CRL trust anchors.
+// -------------------------------------------------------------------------
+
+// There is one trusted root for Cast CRL certificate chains:
+//
+//   (1) CN=Cast CRL Root CA    (kCastCRLRootCaDer)
+//
+// These constants are defined by the file included next:
+
+#include "components/cast_certificate/cast_crl_root_ca_cert_der-inc.h"
+
+// Singleton for the Cast CRL trust store.
+class CastCRLTrustStore {
+ public:
+  static CastCRLTrustStore* GetInstance() {
+    return base::Singleton<CastCRLTrustStore, base::LeakySingletonTraits<
+                                                  CastCRLTrustStore>>::get();
+  }
+
+  static net::TrustStore& Get() { return GetInstance()->store_; }
+
+ private:
+  friend struct base::DefaultSingletonTraits<CastCRLTrustStore>;
+
+  CastCRLTrustStore() {
+    // Initialize the trust store with the root certificate.
+    // TODO(ryanchung): Add official Cast CRL Root here
+    // scoped_refptr<net::ParsedCertificate> root = net::ParsedCertificate::
+    //     net::ParsedCertificate::CreateFromCertificateData(
+    //         kCastCRLRootCaDer, sizeof(kCastCRLRootCaDer),
+    //         net::ParsedCertificate::DataSource::EXTERNAL_REFERENCE, {});
+    // CHECK(root);
+    // store_.AddTrustedCertificate(std::move(root));
+  }
+
+  net::TrustStore store_;
+  DISALLOW_COPY_AND_ASSIGN(CastCRLTrustStore);
+};
+
+// Converts a uint64_t unix timestamp to net::der::GeneralizedTime.
+bool ConvertTimeSeconds(uint64_t seconds,
+                        net::der::GeneralizedTime* generalized_time) {
+  base::Time unix_timestamp =
+      base::Time::UnixEpoch() +
+      base::TimeDelta::FromSeconds(base::saturated_cast<int64_t>(seconds));
+  return net::der::EncodeTimeAsGeneralizedTime(unix_timestamp,
+                                               generalized_time);
+}
+
+// Specifies the signature verification policy.
+// The required algorithms are:
+// RSASSA PKCS#1 v1.5 with SHA-256, using RSA keys 2048-bits or longer.
+std::unique_ptr<net::SignaturePolicy> CreateCastSignaturePolicy() {
+  return base::WrapUnique(new net::SimpleSignaturePolicy(2048));
+}
+
+// Verifies the CRL is signed by a trusted CRL authority at the time the CRL
+// was issued. Verifies the signature of |tbs_crl| is valid based on the
+// certificate and signature in |crl|. The validity of |tbs_crl| is verified
+// at |time|. The validity period of the CRL is adjusted to be the earliest
+// of the issuer certificate chain's expiration and the CRL's expiration and
+// the result is stored in |overall_not_after|.
+bool VerifyCRL(const Crl& crl,
+               const TbsCrl& tbs_crl,
+               const base::Time& time,
+               net::der::GeneralizedTime* overall_not_after) {
+  // Verify the trust of the CRL authority.
+  scoped_refptr<net::ParsedCertificate> parsed_cert =
+      net::ParsedCertificate::CreateFromCertificateData(
+          reinterpret_cast<const uint8_t*>(crl.signer_cert().data()),
+          crl.signer_cert().size(),
+          net::ParsedCertificate::DataSource::EXTERNAL_REFERENCE, {});
+  if (parsed_cert == nullptr) {
+    VLOG(2) << "CRL - Issuer certificate parsing failed.";
+    return false;
+  }
+
+  // Wrap the signature in a BitString.
+  net::der::BitString signature_value_bit_string = net::der::BitString(
+      net::der::Input(base::StringPiece(crl.signature())), 0);
+
+  // Verify the signature.
+  auto signature_policy = CreateCastSignaturePolicy();
+  std::unique_ptr<net::SignatureAlgorithm> signature_algorithm_type =
+      net::SignatureAlgorithm::CreateRsaPkcs1(net::DigestAlgorithm::Sha256);
+  if (!VerifySignedData(*signature_algorithm_type,
+                        net::der::Input(&crl.tbs_crl()),
+                        signature_value_bit_string, parsed_cert->tbs().spki_tlv,
+                        signature_policy.get())) {
+    VLOG(2) << "CRL - Signature verification failed.";
+    return false;
+  }
+
+  // Verify the issuer certificate.
+  net::der::GeneralizedTime verification_time;
+  if (!net::der::EncodeTimeAsGeneralizedTime(time, &verification_time)) {
+    VLOG(2) << "CRL - Unable to parse verification time.";
+    return false;
+  }
+  net::CertPathBuilder::Result result;
+  net::CertPathBuilder path_builder(
+      parsed_cert.get(), &CastCRLTrustStore::Get(), signature_policy.get(),
+      verification_time, &result);
+  net::CompletionStatus rv = path_builder.Run(base::Closure());
+  DCHECK_EQ(rv, net::CompletionStatus::SYNC);
+  if (!result.is_success() || result.paths.empty() ||
+      !result.paths[result.best_result_index]->is_success()) {
+    VLOG(2) << "CRL - Issuer certificate verification failed.";
+    return false;
+  }
+  // There are no requirements placed on the leaf certificate having any
+  // particular KeyUsages. Leaf certificate checks are bypassed.
+
+  // Verify the CRL is still valid.
+  net::der::GeneralizedTime not_before;
+  if (!ConvertTimeSeconds(tbs_crl.not_before_seconds(), &not_before)) {
+    VLOG(2) << "CRL - Unable to parse not_before.";
+    return false;
+  }
+  net::der::GeneralizedTime not_after;
+  if (!ConvertTimeSeconds(tbs_crl.not_after_seconds(), &not_after)) {
+    VLOG(2) << "CRL - Unable to parse not_after.";
+    return false;
+  }
+  if ((verification_time < not_before) || (verification_time > not_after)) {
+    VLOG(2) << "CRL - Not time-valid.";
+    return false;
+  }
+
+  // Set CRL expiry to the earliest of the cert chain expiry and CRL expiry.
+  *overall_not_after = not_after;
+  for (const auto& cert : result.paths[result.best_result_index]->path) {
+    net::der::GeneralizedTime cert_not_after = cert->tbs().validity_not_after;
+    if (cert_not_after < *overall_not_after)
+      *overall_not_after = cert_not_after;
+  }
+
+  // Perform sanity check on serial numbers.
+  for (const auto& range : tbs_crl.revoked_serial_number_ranges()) {
+    uint64_t first_serial_number = range.first_serial_number();
+    uint64_t last_serial_number = range.last_serial_number();
+    if (last_serial_number < first_serial_number) {
+      VLOG(2) << "CRL - Malformed serial number range.";
+      return false;
+    }
+  }
+  return true;
+}
+
+class CastCRLImpl : public CastCRL {
+ public:
+  CastCRLImpl(const TbsCrl& tbs_crl,
+              const net::der::GeneralizedTime& overall_not_after);
+  ~CastCRLImpl() override;
+
+  bool CheckRevocation(const net::ParsedCertificateList& trusted_chain,
+                       const base::Time& time) const override;
+
+ private:
+  struct SerialNumberRange {
+    uint64_t first_serial;
+    uint64_t last_serial;
+  };
+
+  net::der::GeneralizedTime not_before_;
+  net::der::GeneralizedTime not_after_;
+
+  // Revoked public key hashes.
+  // The values consist of the SHA256 hash of the SubjectPublicKeyInfo.
+  std::set<std::string> revoked_hashes_;
+
+  // Revoked serial number ranges indexed by issuer public key hash.
+  // The key is the SHA256 hash of issuer's SubjectPublicKeyInfo.
+  // The value is a list of revoked serial number ranges.
+  std::unordered_map<std::string, std::vector<SerialNumberRange>>
+      revoked_serial_numbers_;
+  DISALLOW_COPY_AND_ASSIGN(CastCRLImpl);
+};
+
+CastCRLImpl::CastCRLImpl(const TbsCrl& tbs_crl,
+                         const net::der::GeneralizedTime& overall_not_after) {
+  // Parse the validity information.
+  // Assume ConvertTimeSeconds will succeed. Successful call to VerifyCRL
+  // means that these calls were successful.
+  ConvertTimeSeconds(tbs_crl.not_before_seconds(), &not_before_);
+  ConvertTimeSeconds(tbs_crl.not_after_seconds(), &not_after_);
+  if (overall_not_after < not_after_)
+    not_after_ = overall_not_after;
+
+  // Parse the revoked hashes.
+  for (const auto& hash : tbs_crl.revoked_public_key_hashes()) {
+    revoked_hashes_.insert(hash);
+  }
+
+  // Parse the revoked serial ranges.
+  for (const auto& range : tbs_crl.revoked_serial_number_ranges()) {
+    std::string issuer_hash = range.issuer_public_key_hash();
+
+    uint64_t first_serial_number = range.first_serial_number();
+    uint64_t last_serial_number = range.last_serial_number();
+    auto& serial_number_range = revoked_serial_numbers_[issuer_hash];
+    serial_number_range.push_back({first_serial_number, last_serial_number});
+  }
+}
+
+CastCRLImpl::~CastCRLImpl() {}
+
+// Verifies the revocation status of the certificate chain, at the specified
+// time.
+bool CastCRLImpl::CheckRevocation(
+    const net::ParsedCertificateList& trusted_chain,
+    const base::Time& time) const {
+  if (trusted_chain.empty())
+    return false;
+
+  // Check the validity of the CRL at the specified time.
+  net::der::GeneralizedTime verification_time;
+  if (!net::der::EncodeTimeAsGeneralizedTime(time, &verification_time)) {
+    VLOG(2) << "CRL verification time malformed.";
+    return false;
+  }
+  if ((verification_time < not_before_) || (verification_time > not_after_)) {
+    VLOG(2) << "CRL not time-valid. Perform hard fail.";
+    return false;
+  }
+
+  // Check revocation.
+  for (size_t i = 0; i < trusted_chain.size(); ++i) {
+    const auto& parsed_cert = trusted_chain[i];
+    // Calculate the public key's hash to check for revocation.
+    std::string spki_hash =
+        crypto::SHA256HashString(parsed_cert->tbs().spki_tlv.AsString());
+    if (revoked_hashes_.find(spki_hash) != revoked_hashes_.end()) {
+      VLOG(2) << "Public key is revoked.";
+      return false;
+    }
+
+    // Check if the subordinate certificate was revoked by serial number.
+    if (i > 0) {
+      auto issuer_iter = revoked_serial_numbers_.find(spki_hash);
+      if (issuer_iter != revoked_serial_numbers_.end()) {
+        const auto& subordinate = trusted_chain[i - 1];
+        uint64_t serial_number;
+        // Only Google generated device certificates will be revoked by range.
+        // These will always be less than 64 bits in length.
+        if (!net::der::ParseUint64(subordinate->tbs().serial_number,
+                                   &serial_number)) {
+          continue;
+        }
+        for (const auto& revoked_serial : issuer_iter->second) {
+          if (revoked_serial.first_serial <= serial_number &&
+              revoked_serial.last_serial >= serial_number) {
+            VLOG(2) << "Serial number is revoked";
+            return false;
+          }
+        }
+      }
+    }
+  }
+  return true;
+}
+
+}  // namespace
+
+std::unique_ptr<CastCRL> ParseAndVerifyCRL(const std::string& crl_proto,
+                                           const base::Time& time) {
+  CrlBundle crl_bundle;
+  if (!crl_bundle.ParseFromString(crl_proto)) {
+    LOG(ERROR) << "CRL - Binary could not be parsed.";
+    return nullptr;
+  }
+  for (auto const& crl : crl_bundle.crls()) {
+    TbsCrl tbs_crl;
+    if (!tbs_crl.ParseFromString(crl.tbs_crl())) {
+      LOG(WARNING) << "Binary TBS CRL could not be parsed.";
+      continue;
+    }
+    if (tbs_crl.version() != CRL_VERSION_0) {
+      continue;
+    }
+    net::der::GeneralizedTime overall_not_after;
+    if (!VerifyCRL(crl, tbs_crl, time, &overall_not_after)) {
+      LOG(ERROR) << "CRL - Verification failed.";
+      return nullptr;
+    }
+    return base::WrapUnique(new CastCRLImpl(tbs_crl, overall_not_after));
+  }
+  LOG(ERROR) << "No supported version of revocation data.";
+  return nullptr;
+}
+
+bool SetCRLTrustAnchorForTest(const std::string& cert) {
+  scoped_refptr<net::ParsedCertificate> anchor(
+      net::ParsedCertificate::CreateFromCertificateCopy(cert, {}));
+  if (!anchor)
+    return false;
+  CastCRLTrustStore::Get().Clear();
+  CastCRLTrustStore::Get().AddTrustedCertificate(std::move(anchor));
+  return true;
+}
+
+}  // namespace cast_certificate