Refuse to accept certificate chains containing any RSA public key smaller

net/base/x509_certificate.cc

 // Copyright (c) 2011 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/base/x509_certificate.h"
 
 #include <stdlib.h>
 
 #include <algorithm>
 #include <map>
@@ skipping 572 matching lines @@
   verify_result->Reset();
   verify_result->verified_cert = const_cast<X509Certificate*>(this);
 
   if (IsBlacklisted()) {
     verify_result->cert_status |= CERT_STATUS_REVOKED;
     return ERR_CERT_REVOKED;
   }
 
   int rv = VerifyInternal(hostname, flags, crl_set, verify_result);
 
+  // Check for weak keys in the entire verified chain.
+  size_t size_bits = 0;
+  PublicKeyType type = kPublicKeyTypeUnknown;
+  bool weak_key = false;
+
+  GetPublicKeyInfo(verify_result->verified_cert->os_cert_handle(), &size_bits,
+                   &type);
+  if (type == kPublicKeyTypeRSA && size_bits < 1024)
+    weak_key = true;

[wtc, 2011/11/17 02:52:18]

It seems that a IsWeakPublicKey/ContainsWeakPublicKey function
may be more appropriate than the GetPublicKeyInfo function.
Also, it may be a good idea to create a method for the code
on lines 593-610.

Please define a constant for 1024.  Your CL's commit message
says "less than 1023 bits".  Should we use 1023 instead?

+
+  const OSCertHandles& intermediates =
+      verify_result->verified_cert->GetIntermediateCertificates();
+  for (OSCertHandles::const_iterator i = intermediates.begin();
+       i != intermediates.end(); ++i) {
+    GetPublicKeyInfo(*i, &size_bits, &type);
+    if (type == kPublicKeyTypeRSA && size_bits < 1024)
+      weak_key = true;
+  }
+
+  if (weak_key) {
+    verify_result->cert_status |= CERT_STATUS_WEAK_KEY;
+    return MapCertStatusToNetError(verify_result->cert_status);
+  }
+
   // This check is done after VerifyInternal so that VerifyInternal can fill in
   // the list of public key hashes.
   if (IsPublicKeyBlacklisted(verify_result->public_key_hashes)) {
     verify_result->cert_status |= CERT_STATUS_REVOKED;
     rv = MapCertStatusToNetError(verify_result->cert_status);
   }
 
   return rv;
 }
 
@@ skipping 195 matching lines @@
 bool X509Certificate::IsSHA1HashInSortedArray(const SHA1Fingerprint& hash,
                                               const uint8* array,
                                               size_t array_byte_len) {
   DCHECK_EQ(0u, array_byte_len % base::kSHA1Length);
   const size_t arraylen = array_byte_len / base::kSHA1Length;
   return NULL != bsearch(hash.data, array, arraylen, base::kSHA1Length,
                          CompareSHA1Hashes);
 }
 
 }  // namespace net