Check whether or not a certificate is self-signed.

net/cert/x509_certificate_mac.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/x509_certificate.h"
 
 #include <CommonCrypto/CommonDigest.h>
 #include <CoreServices/CoreServices.h>
 #include <Security/Security.h>
 
 #include <vector>
 
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/mac/mac_logging.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "base/memory/singleton.h"
+#include "base/numerics/safe_conversions.h"
 #include "base/pickle.h"
 #include "base/sha1.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/synchronization/lock.h"
 #include "crypto/cssm_init.h"
 #include "crypto/mac_security_services_lock.h"
 #include "net/cert/x509_util_mac.h"
 
 using base::ScopedCFTypeRef;
@@ skipping 478 matching lines @@
     case CSSM_ALGID_DH:
       *type = kPublicKeyTypeDH;
       break;
     default:
       *type = kPublicKeyTypeUnknown;
       *size_bits = 0;
       break;
   }
 }
 
+// static
+bool X509Certificate::IsSelfSigned(OSCertHandle cert_handle) {
+  std::string der_cert;
+  if (!GetDEREncoded(cert_handle, &der_cert))
+    return false;
+
+  const unsigned char* cert_data =
+      reinterpret_cast<const unsigned char*>(der_cert.data());
+  int cert_data_len = checked_cast<int>(der_cert.size());
+  ScopedX509 cert(d2i_X509(NULL, &cert_data, cert_data_len));
+  crypto::ScopedEVP_PKEY scoped_key(X509_get_pubkey(cert_handle));
+  if (!scoped_key)
+    return false;
+  DCHECK(scoped_key.get());
+  EVP_PKEY* key = scoped_key.get();
+
+  // NOTE: X509_verify() returns 1 in case of success, 0 or -1 on error.
+  return X509_verify(cert.get(), key) == 1;
+}
+
 }  // namespace net