Call CryptSignHash twice in client certificate logic.

net/ssl/openssl_platform_key_win.cc

Index: net/ssl/openssl_platform_key_win.cc
diff --git a/net/ssl/openssl_platform_key_win.cc b/net/ssl/openssl_platform_key_win.cc
index 4a399fb20d03e100eedc4ae4ee18ea385be40ae2..9033c6e8e4b3d99929846258c29926ced129d2a1 100644
--- a/net/ssl/openssl_platform_key_win.cc
+++ b/net/ssl/openssl_platform_key_win.cc
@@ -317,7 +317,20 @@ int RsaMethodSign(int hash_nid,
     OpenSSLPutNetError(FROM_HERE, ERR_SSL_CLIENT_AUTH_SIGNATURE_FAILED);
     return 0;
   }
-  DWORD signature_len = RSA_size(rsa);
+  // Determine the output length.
+  DWORD signature_len = 0;
+  if (!CryptSignHash(hash.get(), ex_data->key->dwKeySpec, nullptr, 0, nullptr,
+                     &signature_len)) {
+    PLOG(ERROR) << "CryptSignHash failed";
+    OpenSSLPutNetError(FROM_HERE, ERR_SSL_CLIENT_AUTH_SIGNATURE_FAILED);
+    return 0;
+  }
+  if (signature_len == 0 || signature_len > RSA_size(rsa)) {
+    LOG(ERROR) << "Bad signature length";
+    OpenSSLPutNetError(FROM_HERE, ERR_SSL_CLIENT_AUTH_SIGNATURE_FAILED);
+    return 0;
+  }
+  // Sign the hash.
   if (!CryptSignHash(hash.get(), ex_data->key->dwKeySpec, nullptr, 0, out,
                      &signature_len)) {
     PLOG(ERROR) << "CryptSignHash failed";