Allow empty keys in hmac_openssl.cc.

crypto/hmac_unittest.cc

Index: crypto/hmac_unittest.cc
diff --git a/crypto/hmac_unittest.cc b/crypto/hmac_unittest.cc
index f0844a9186c9d661273483266408dcb9b2e1a3c1..2cbecf2fc6a3ba60d94a6d1f26178387d987270a 100644
--- a/crypto/hmac_unittest.cc
+++ b/crypto/hmac_unittest.cc
@@ -275,3 +275,20 @@ TEST(HMACTest, Verify) {
         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";
+
+  crypto::HMAC hmac(crypto::HMAC::SHA1);
+  ASSERT_TRUE(hmac.Init(NULL, 0));
+
+  unsigned char digest[kSHA1DigestSize];
+  EXPECT_TRUE(hmac.Sign("", digest, kSHA1DigestSize));

[wtc, 2014/04/09 21:30:58]

Please use base::StringPiece() instead of "" here and in the hmac.Verify() call,
to eliminate the doubt that the null terminator in an empty C string may get
used.

[davidben, 2014/04/09 21:44:29]

Done. Amusingly, I had to use base::StringPiece("", 0) rather than
base::StringPiece(NULL, 0). The latter upsets NSS. I think I have to conclude C
code by and large doesn't deal with empty byte arrays very well. :-)

+  EXPECT_EQ(0, memcmp(kExpectedDigest, digest, kSHA1DigestSize));
+
+  EXPECT_TRUE(hmac.Verify(
+      "", base::StringPiece(kExpectedDigest, kSHA1DigestSize)));
+}