Distrust publicly trusted SHA-1 certs

net/cert/cert_verify_proc.cc

 // Copyright (c) 2012 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 "net/cert/cert_verify_proc.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 
@@ skipping 23 matching lines @@
 #include "net/cert/cert_verify_proc_nss.h"
 #elif defined(USE_OPENSSL_CERTS) && !defined(OS_ANDROID)
 #include "net/cert/cert_verify_proc_openssl.h"
 #elif defined(OS_ANDROID)
 #include "net/cert/cert_verify_proc_android.h"
 #elif defined(OS_IOS)
 #include "net/cert/cert_verify_proc_ios.h"
 #elif defined(OS_MACOSX)
 #include "net/cert/cert_verify_proc_mac.h"
 #elif defined(OS_WIN)
+#include "base/win/windows_version.h"
 #include "net/cert/cert_verify_proc_win.h"
 #else
 #error Implement certificate verification.
 #endif
 
 namespace net {
 
 namespace {
 
 // Constants used to build histogram names
@@ skipping 296 matching lines @@
   }
 
   template <size_t N>
   bool operator()(const HashValue& lhs, const uint8_t(&rhs)[N]) const {
     static_assert(N == crypto::kSHA256Length,
                   "Only SHA-256 hashes are supported");
     return memcmp(lhs.data(), rhs, crypto::kSHA256Length) < 0;
   }
 };
 
+bool AreSHA1IntermediatesAllowed() {
+#if defined(OS_WIN)
+  // TODO(rsleevi): Remove this once https://crbug.com/588789 is resolved
+  // for Windows 7/2008 users.
+  // Note: This must be kept in sync with cert_verify_proc_unittest.cc
+  return base::win::GetVersion() < base::win::VERSION_WIN8;
+#else
+  return false;
+#endif
+};
+
 }  // namespace
 
 // static
 CertVerifyProc* CertVerifyProc::CreateDefault() {
 #if defined(USE_NSS_CERTS)
   return new CertVerifyProcNSS();
 #elif defined(USE_OPENSSL_CERTS) && !defined(OS_ANDROID)
   return new CertVerifyProcOpenSSL();
 #elif defined(OS_ANDROID)
   return new CertVerifyProcAndroid();
@@ skipping 96 matching lines @@
   // The CA/Browser Forum Baseline Requirements (beginning with v1.2.1)
   // prohibits SHA-1 certificates from being issued beginning on
   // 1 January 2016. Ideally, all of SHA-1 in new certificates would be
   // disabled on this date, but enterprises need more time to transition.
   // As the risk is greatest for publicly trusted certificates, prevent
   // those certificates from being trusted from that date forward.
   //
   // TODO(mattm): apply the SHA-1 deprecation check to all certs unless
   // CertVerifier::VERIFY_ENABLE_SHA1_LOCAL_ANCHORS flag is present.
   if (verify_result->has_md5 ||
-      (verify_result->has_sha1_leaf && verify_result->is_issued_by_known_root &&
-       IsPastSHA1DeprecationDate(*cert))) {
+      // Current SHA-1 behaviour:
+      // - Reject all publicly trusted SHA-1
+      // - ... unless it's in the intermediate and SHA-1 intermediates are
+      //   allowed for that platform. See https://crbug.com/588789
+      (!base::FeatureList::IsEnabled(kSHA1LegacyMode) &&
+       (verify_result->is_issued_by_known_root &&
+        (verify_result->has_sha1_leaf ||
+         (verify_result->has_sha1 && !AreSHA1IntermediatesAllowed())))) ||
+      // Legacy SHA-1 behaviour:
+      // - Reject all publicly trusted SHA-1 leaf certs issued after
+      //   2016-01-01.
+      (base::FeatureList::IsEnabled(kSHA1LegacyMode) &&
+       (verify_result->has_sha1_leaf &&
+        verify_result->is_issued_by_known_root &&
+        IsPastSHA1DeprecationDate(*cert)))) {
     verify_result->cert_status |= CERT_STATUS_WEAK_SIGNATURE_ALGORITHM;
     // Avoid replacing a more serious error, such as an OS/library failure,
     // by ensuring that if verification failed, it failed with a certificate
     // error.
     if (rv == OK || IsCertificateError(rv))
       rv = MapCertStatusToNetError(verify_result->cert_status);
   }
 
   // Flag certificates from publicly-trusted CAs that are issued to intranet
   // hosts. While the CA/Browser Forum Baseline Requirements (v1.1) permit
@@ skipping 252 matching lines @@
   if (start >= time_2012_07_01 && month_diff > 60)
     return true;
 
   // For certificates issued after 1 April 2015: 39 months.
   if (start >= time_2015_04_01 && month_diff > 39)
     return true;
 
   return false;
 }
 
+// static
+const base::Feature CertVerifyProc::kSHA1LegacyMode{
+    "SHA1LegacyMode", base::FEATURE_DISABLED_BY_DEFAULT};
+
 }  // namespace net