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| 1 // Copyright 2014 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 #include "extensions/common/cast/cast_cert_validator.h" | |
| 6 | |
| 7 #include <stddef.h> | |
| 8 #include <stdint.h> | |
| 9 | |
| 10 #include <algorithm> | |
| 11 #include <memory> | |
| 12 #include <utility> | |
| 13 | |
| 14 #include "base/memory/ptr_util.h" | |
| 15 #include "base/memory/singleton.h" | |
| 16 #include "net/cert/internal/certificate_policies.h" | |
| 17 #include "net/cert/internal/extended_key_usage.h" | |
| 18 #include "net/cert/internal/parse_certificate.h" | |
| 19 #include "net/cert/internal/parse_name.h" | |
| 20 #include "net/cert/internal/signature_algorithm.h" | |
| 21 #include "net/cert/internal/signature_policy.h" | |
| 22 #include "net/cert/internal/verify_certificate_chain.h" | |
| 23 #include "net/cert/internal/verify_signed_data.h" | |
| 24 #include "net/der/input.h" | |
| 25 | |
| 26 namespace extensions { | |
| 27 namespace api { | |
| 28 namespace cast_crypto { | |
| 29 namespace { | |
| 30 | |
| 31 // ------------------------------------------------------------------------- | |
| 32 // Cast trust anchors. | |
| 33 // ------------------------------------------------------------------------- | |
| 34 | |
| 35 // There are two trusted roots for Cast certificate chains: | |
| 36 // | |
| 37 // (1) CN=Cast Root CA (kCastRootCaDer) | |
| 38 // (2) CN=Eureka Root CA (kEurekaRootCaDer) | |
| 39 // | |
| 40 // These constants are defined by the files included next: | |
| 41 | |
| 42 #include "extensions/common/cast/cast_root_ca_cert_der-inc.h" | |
| 43 #include "extensions/common/cast/eureka_root_ca_der-inc.h" | |
| 44 | |
| 45 // Singleton for the Cast trust store. | |
| 46 class CastTrustStore { | |
| 47 public: | |
| 48 static CastTrustStore* GetInstance() { | |
| 49 return base::Singleton<CastTrustStore, | |
| 50 base::LeakySingletonTraits<CastTrustStore>>::get(); | |
| 51 } | |
| 52 | |
| 53 static net::TrustStore& Get() { return GetInstance()->store_; } | |
| 54 | |
| 55 private: | |
| 56 friend struct base::DefaultSingletonTraits<CastTrustStore>; | |
| 57 | |
| 58 CastTrustStore() { | |
| 59 // Initialize the trust store with two root certificates. | |
| 60 CHECK(store_.AddTrustedCertificateWithoutCopying(kCastRootCaDer, | |
| 61 sizeof(kCastRootCaDer))); | |
| 62 CHECK(store_.AddTrustedCertificateWithoutCopying(kEurekaRootCaDer, | |
| 63 sizeof(kEurekaRootCaDer))); | |
| 64 } | |
| 65 | |
| 66 net::TrustStore store_; | |
| 67 DISALLOW_COPY_AND_ASSIGN(CastTrustStore); | |
| 68 }; | |
| 69 | |
| 70 using ExtensionsMap = std::map<net::der::Input, net::ParsedExtension>; | |
| 71 | |
| 72 // Helper that looks up an extension by OID given a map of extensions. | |
| 73 bool GetExtensionValue(const ExtensionsMap& extensions, | |
| 74 const net::der::Input& oid, | |
| 75 net::der::Input* value) { | |
| 76 auto it = extensions.find(oid); | |
| 77 if (it == extensions.end()) | |
| 78 return false; | |
| 79 *value = it->second.value; | |
| 80 return true; | |
| 81 } | |
| 82 | |
| 83 // Returns the OID for the Audio-Only Cast policy | |
| 84 // (1.3.6.1.4.1.11129.2.5.2) in DER form. | |
| 85 net::der::Input AudioOnlyPolicyOid() { | |
| 86 static const uint8_t kAudioOnlyPolicy[] = {0x2B, 0x06, 0x01, 0x04, 0x01, | |
| 87 0xD6, 0x79, 0x02, 0x05, 0x02}; | |
| 88 return net::der::Input(kAudioOnlyPolicy); | |
| 89 } | |
| 90 | |
| 91 // Cast certificates rely on RSASSA-PKCS#1 v1.5 with SHA-1 for signatures. | |
| 92 // | |
| 93 // The following signature policy specifies which signature algorithms (and key | |
| 94 // sizes) are acceptable. It is used when verifying a chain of certificates, as | |
| 95 // well as when verifying digital signature using the target certificate's | |
| 96 // SPKI. | |
| 97 // | |
| 98 // This particular policy allows for: | |
| 99 // * ECDSA, RSA-SSA, and RSA-PSS | |
| 100 // * Supported EC curves: P-256, P-384, P-521. | |
| 101 // * Hashes: All SHA hashes including SHA-1 (despite being known weak). | |
| 102 // * RSA keys must have a modulus at least 2048-bits long. | |
| 103 std::unique_ptr<net::SignaturePolicy> CreateCastSignaturePolicy() { | |
| 104 return base::WrapUnique(new net::SimpleSignaturePolicy(2048)); | |
| 105 } | |
| 106 | |
| 107 class CertVerificationContextImpl : public CertVerificationContext { | |
| 108 public: | |
| 109 // Save a copy of the passed in public key (DER) and common name (text). | |
| 110 CertVerificationContextImpl(const net::der::Input& spki, | |
| 111 const base::StringPiece& common_name) | |
| 112 : spki_(spki.AsString()), common_name_(common_name.as_string()) {} | |
| 113 | |
| 114 bool VerifySignatureOverData(const base::StringPiece& signature, | |
| 115 const base::StringPiece& data) const override { | |
| 116 // This code assumes the signature algorithm was RSASSA PKCS#1 v1.5 with | |
| 117 // SHA-1. | |
| 118 // TODO(eroman): Is it possible to use other hash algorithms? | |
| 119 auto signature_algorithm = | |
| 120 net::SignatureAlgorithm::CreateRsaPkcs1(net::DigestAlgorithm::Sha1); | |
| 121 | |
| 122 // Use the same policy as was used for verifying signatures in | |
| 123 // certificates. This will ensure for instance that the key used is at | |
| 124 // least 2048-bits long. | |
| 125 auto signature_policy = CreateCastSignaturePolicy(); | |
| 126 | |
| 127 return net::VerifySignedData( | |
| 128 *signature_algorithm, net::der::Input(data), | |
| 129 net::der::BitString(net::der::Input(signature), 0), | |
| 130 net::der::Input(&spki_), signature_policy.get()); | |
| 131 } | |
| 132 | |
| 133 std::string GetCommonName() const override { return common_name_; } | |
| 134 | |
| 135 private: | |
| 136 std::string spki_; | |
| 137 std::string common_name_; | |
| 138 }; | |
| 139 | |
| 140 // Helper that extracts the Common Name from a certificate's subject field. On | |
| 141 // success |common_name| contains the text for the attribute (unescaped, so | |
| 142 // will depend on the encoding used, but for Cast device certs it should | |
| 143 // be ASCII). | |
| 144 bool GetCommonNameFromSubject(const net::der::Input& subject_tlv, | |
| 145 std::string* common_name) { | |
| 146 net::RDNSequence rdn_sequence; | |
| 147 if (!net::ParseName(subject_tlv, &rdn_sequence)) | |
| 148 return false; | |
| 149 | |
| 150 for (const net::RelativeDistinguishedName& rdn : rdn_sequence) { | |
| 151 for (const auto& atv : rdn) { | |
| 152 if (atv.type == net::TypeCommonNameOid()) { | |
| 153 return atv.ValueAsStringUnsafe(common_name); | |
| 154 } | |
| 155 } | |
| 156 } | |
| 157 return false; | |
| 158 } | |
| 159 | |
| 160 // Returns true if the extended key usage list |ekus| contains client auth. | |
| 161 bool HasClientAuth(const std::vector<net::der::Input>& ekus) { | |
| 162 for (const auto& oid : ekus) { | |
| 163 if (oid == net::ClientAuth()) | |
| 164 return true; | |
| 165 } | |
| 166 return false; | |
| 167 } | |
| 168 | |
| 169 // Checks properties on the target certificate. | |
| 170 // | |
| 171 // * The Key Usage must include Digital Signature | |
| 172 // * THe Extended Key Usage must includ TLS Client Auth | |
| 173 // * May have the policy 1.3.6.1.4.1.11129.2.5.2 to indicate it | |
| 174 // is an audio-only device. | |
| 175 WARN_UNUSED_RESULT bool CheckTargetCertificate( | |
| 176 const net::der::Input& cert_der, | |
| 177 std::unique_ptr<CertVerificationContext>* context, | |
| 178 CastDeviceCertPolicy* policy) { | |
| 179 // TODO(eroman): Simplify this. The certificate chain verification | |
| 180 // function already parses this stuff, awkward to re-do it here. | |
| 181 | |
| 182 net::ParsedCertificate cert; | |
| 183 if (!net::ParseCertificate(cert_der, &cert)) | |
| 184 return false; | |
| 185 | |
| 186 net::ParsedTbsCertificate tbs; | |
| 187 if (!net::ParseTbsCertificate(cert.tbs_certificate_tlv, &tbs)) | |
| 188 return false; | |
| 189 | |
| 190 // Get the extensions. | |
| 191 if (!tbs.has_extensions) | |
| 192 return false; | |
| 193 ExtensionsMap extensions; | |
| 194 if (!net::ParseExtensions(tbs.extensions_tlv, &extensions)) | |
| 195 return false; | |
| 196 | |
| 197 net::der::Input extension_value; | |
| 198 | |
| 199 // Get the Key Usage extension. | |
| 200 if (!GetExtensionValue(extensions, net::KeyUsageOid(), &extension_value)) | |
| 201 return false; | |
| 202 net::der::BitString key_usage; | |
| 203 if (!net::ParseKeyUsage(extension_value, &key_usage)) | |
| 204 return false; | |
| 205 | |
| 206 // Ensure Key Usage contains digitalSignature. | |
| 207 if (!key_usage.AssertsBit(net::KEY_USAGE_BIT_DIGITAL_SIGNATURE)) | |
| 208 return false; | |
| 209 | |
| 210 // Get the Extended Key Usage extension. | |
| 211 if (!GetExtensionValue(extensions, net::ExtKeyUsageOid(), &extension_value)) | |
| 212 return false; | |
| 213 std::vector<net::der::Input> ekus; | |
| 214 if (!net::ParseEKUExtension(extension_value, &ekus)) | |
| 215 return false; | |
| 216 | |
| 217 // Ensure Extended Key Usage contains client auth. | |
| 218 if (!HasClientAuth(ekus)) | |
| 219 return false; | |
| 220 | |
| 221 // Check for an optional audio-only policy extension. | |
| 222 *policy = CastDeviceCertPolicy::NONE; | |
| 223 if (GetExtensionValue(extensions, net::CertificatePoliciesOid(), | |
| 224 &extension_value)) { | |
| 225 std::vector<net::der::Input> policies; | |
| 226 if (!net::ParseCertificatePoliciesExtension(extension_value, &policies)) | |
| 227 return false; | |
| 228 | |
| 229 // Look for an audio-only policy. Disregard any other policy found. | |
| 230 if (std::find(policies.begin(), policies.end(), AudioOnlyPolicyOid()) != | |
| 231 policies.end()) { | |
| 232 *policy = CastDeviceCertPolicy::AUDIO_ONLY; | |
| 233 } | |
| 234 } | |
| 235 | |
| 236 // Get the Common Name for the certificate. | |
| 237 std::string common_name; | |
| 238 if (!GetCommonNameFromSubject(tbs.subject_tlv, &common_name)) | |
| 239 return false; | |
| 240 | |
| 241 context->reset(new CertVerificationContextImpl(tbs.spki_tlv, common_name)); | |
| 242 return true; | |
| 243 } | |
| 244 | |
| 245 | |
| 246 // Converts a base::Time::Exploded to a net::der::GeneralizedTime. | |
| 247 net::der::GeneralizedTime ConvertExplodedTime( | |
| 248 const base::Time::Exploded& exploded) { | |
| 249 net::der::GeneralizedTime result; | |
| 250 result.year = exploded.year; | |
| 251 result.month = exploded.month; | |
| 252 result.day = exploded.day_of_month; | |
| 253 result.hours = exploded.hour; | |
| 254 result.minutes = exploded.minute; | |
| 255 result.seconds = exploded.second; | |
| 256 return result; | |
| 257 } | |
| 258 | |
| 259 } // namespace | |
| 260 | |
| 261 bool VerifyDeviceCert(const std::vector<std::string>& certs, | |
| 262 const base::Time::Exploded& time, | |
| 263 std::unique_ptr<CertVerificationContext>* context, | |
| 264 CastDeviceCertPolicy* policy) { | |
| 265 // The underlying verification function expects a sequence of | |
| 266 // der::Input, so wrap the data in it (cheap). | |
| 267 std::vector<net::der::Input> input_chain; | |
| 268 for (const auto& cert : certs) | |
| 269 input_chain.push_back(net::der::Input(&cert)); | |
| 270 | |
| 271 // Use a signature policy compatible with Cast's PKI. | |
| 272 auto signature_policy = CreateCastSignaturePolicy(); | |
| 273 | |
| 274 // Do RFC 5280 compatible certificate verification using the two Cast | |
| 275 // trust anchors and Cast signature policy. | |
| 276 if (!net::VerifyCertificateChain(input_chain, CastTrustStore::Get(), | |
| 277 signature_policy.get(), | |
| 278 ConvertExplodedTime(time))) { | |
| 279 return false; | |
| 280 } | |
| 281 | |
| 282 // Check properties of the leaf certificate (key usage, policy), and construct | |
| 283 // a CertVerificationContext that uses its public key. | |
| 284 return CheckTargetCertificate(input_chain[0], context, policy); | |
| 285 } | |
| 286 | |
| 287 std::unique_ptr<CertVerificationContext> CertVerificationContextImplForTest( | |
| 288 const base::StringPiece& spki) { | |
| 289 // Use a bogus CommonName, since this is just exposed for testing signature | |
| 290 // verification by unittests. | |
| 291 return base::WrapUnique( | |
| 292 new CertVerificationContextImpl(net::der::Input(spki), "CommonName")); | |
| 293 } | |
| 294 | |
| 295 bool AddTrustAnchorForTest(const uint8_t* data, size_t length) { | |
| 296 return CastTrustStore::Get().AddTrustedCertificateWithoutCopying(data, | |
| 297 length); | |
| 298 } | |
| 299 | |
| 300 } // namespace cast_crypto | |
| 301 } // namespace api | |
| 302 } // namespace extensions | |
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Chromium Code Reviews
Issue 1924323002:
Move Cast certificate verification code from extensions to components. (Closed)
Base URL: https://chromium.googlesource.com/chromium/src.git@master