Refuse to accept certificate chains containing any RSA public key smaller

net/base/x509_certificate_openssl.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 <openssl/asn1.h>
 #include <openssl/crypto.h>
 #include <openssl/obj_mac.h>
 #include <openssl/pem.h>
@@ skipping 601 matching lines @@
                                                 Pickle* pickle) {
   DERCache der_cache;
   if (!GetDERAndCacheIfNeeded(cert_handle, &der_cache))
     return false;
 
   return pickle->WriteData(
       reinterpret_cast<const char*>(der_cache.data),
       der_cache.data_length);
 }
 
+// static
+void X509Certificate::GetPublicKeyInfo(OSCertHandle cert_handle,
+                                       size_t* size_bits,
+                                       PublicKeyType* type) {
+  EVP_PKEY* key = X509_get_pubkey(cert_handle);
+  CHECK(key);
+  *size_bits = EVP_PKEY_size(key) * 8;

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

Is there an OpenSSL function that returns the key size in
bits?  Some EC key sizes are not a multiple of 8 (e.g., 521).

[Ryan Sleevi, 2011/11/17 03:20:33]

That was on me.

EVP_PKEY_bits, but then it gets into the weird 1023/1024 bit size IIRC. For
DSA/EC/RSA/DH, it's just a wrapper for BN_num_bits.

EVP_PKEY_size does the right thing for RSA, but for DSA/ECDH returns
[EC]DSA_size, which is the maximum length of an [EC]DSA signature created with
that key.

So there's no good solution that solves both cases.

FWIW, the OpenSSL code (command-line, etc) in 0.9.8 just uses a series of ifs
switched off pkey->type, so perhaps both *size_bits and *type should be handled
in the switch.

[palmer, 2011/12/13 18:55:44]

Done.

+
+  switch (key->type) {
+    case EVP_PKEY_RSA:
+      *type = kPublicKeyTypeRSA;
+      break;
+    case EVP_PKEY_DSA:
+      *type = kPublicKeyTypeDSA;
+      break;
+    case EVP_PKEY_EC:
+      *type = kPublicKeyTypeECDSA;
+      break;
+    case EVP_PKEY_DH:
+      *type = kPublicKeyTypeDH;
+      break;
+    default:
+      *type = kPublicKeyTypeUnknown;
+  }
+}
+
 }  // namespace net