Allow empty keys in hmac_openssl.cc.

crypto/hmac_unittest.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 <string>
 
 #include "crypto/hmac.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 static const size_t kSHA1DigestSize = 20;
@@ skipping 257 matching lines @@
         base::StringPiece(kSimpleHmacCases[i].data,
                           kSimpleHmacCases[i].data_len)));
 
     // Expected size, mismatched data
     EXPECT_FALSE(hmac.Verify(
         base::StringPiece(kSimpleHmacCases[i].data,
                           kSimpleHmacCases[i].data_len),
         base::StringPiece(empty_digest, kSHA1DigestSize)));
   }
 }
+
+TEST(HMACTest, EmptyKey) {
+  // Test vector from https://en.wikipedia.org/wiki/HMAC
+  const char* kExpectedDigest =
+      "\xFB\xDB\x1D\x1B\x18\xAA\x6C\x08\x32\x4B\x7D\x64\xB7\x1F\xB7\x63"
+      "\x70\x69\x0E\x1D";
+  base::StringPiece data("", 0u);

[wtc, 2014/04/10 18:43:41]

You can also try using a std::string:

  std::string data;

My experiments show that data.data() is a non-null pointer on Linux and Windows.
Your current solution is fine, too.

[davidben, 2014/04/10 18:54:29]

Yeah, per C++11, std::string::data and std::string::c_str are the same and both
include the trailing NUL. I think it's actually not required to in C++03, but
putting the NUL byte in when calling c_str would be insane so I doubt anyone
does that. Though std::string::data apparently always returns non-NULL per C++03
too:

"If size() is zero, the member returns a non-null pointer that is copyable and
can have zero added to it"

which does make me wonder what that pointer is supposed to point to... something
random?


Anyway... empty byte arrays. They are ridiculous. :-)

+
+  crypto::HMAC hmac(crypto::HMAC::SHA1);
+  ASSERT_TRUE(hmac.Init(NULL, 0));
+
+  unsigned char digest[kSHA1DigestSize];
+  EXPECT_TRUE(hmac.Sign(data, digest, kSHA1DigestSize));
+  EXPECT_EQ(0, memcmp(kExpectedDigest, digest, kSHA1DigestSize));
+
+  EXPECT_TRUE(hmac.Verify(
+      data, base::StringPiece(kExpectedDigest, kSHA1DigestSize)));
+}