[webcrypto] Add decrypt() for AES-CBC.

content/renderer/webcrypto_impl_unittest.cc

 // Copyright 2013 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 "webcrypto_impl.h"
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 103 matching lines @@
 
   bool EncryptInternal(
       const WebKit::WebCryptoAlgorithm& algorithm,
       const WebKit::WebCryptoKey& key,
       const unsigned char* data,
       unsigned data_size,
       WebKit::WebArrayBuffer* buffer) {
     return crypto_.EncryptInternal(algorithm, key, data, data_size, buffer);
   }
 
+  bool DecryptInternal(
+      const WebKit::WebCryptoAlgorithm& algorithm,
+      const WebKit::WebCryptoKey& key,
+      const unsigned char* data,
+      unsigned data_size,
+      WebKit::WebArrayBuffer* buffer) {
+    return crypto_.DecryptInternal(algorithm, key, data, data_size, buffer);
+  }
+
  private:
   WebCryptoImpl crypto_;
 };
 
 TEST_F(WebCryptoImplTest, DigestSampleSets) {
   // The results are stored here in hex format for readability.
   //
   // TODO(bryaneyler): Eventually, all these sample test sets should be replaced
   // with the sets here: http://csrc.nist.gov/groups/STM/cavp/index.html#03
   //
@@ skipping 174 matching lines @@
 
     WebKit::WebArrayBuffer output;
 
     ASSERT_TRUE(SignInternal(
         algorithm, key, message_raw.data(), message_raw.size(), &output));
 
     ExpectArrayBufferMatchesHex(test.mac, output);
   }
 }
 
-TEST_F(WebCryptoImplTest, AesCbcEncryptionFailures) {
+TEST_F(WebCryptoImplTest, AesCbcFailures) {
   WebKit::WebCryptoKey key = ImportSecretKeyFromRawHexString(
       "2b7e151628aed2a6abf7158809cf4f3c",
       CreateAlgorithm(WebKit::WebCryptoAlgorithmIdAesCbc),
       WebKit::WebCryptoKeyUsageEncrypt | WebKit::WebCryptoKeyUsageDecrypt);
 
   WebKit::WebArrayBuffer output;
 
   // Use an invalid |iv| (fewer than 16 bytes)
   {
-    std::vector<uint8> plain_text(33);
+    std::vector<uint8> input(32);
     std::vector<uint8> iv;
-    EXPECT_FALSE(EncryptInternal(CreateAesCbcAlgorithm(iv),
-                                 key,
-                                 plain_text.data(),
-                                 plain_text.size(),
-                                 &output));
+    EXPECT_FALSE(EncryptInternal(
+        CreateAesCbcAlgorithm(iv), key, input.data(), input.size(), &output));
+    EXPECT_FALSE(DecryptInternal(
+        CreateAesCbcAlgorithm(iv), key, input.data(), input.size(), &output));
   }
 
   // Use an invalid |iv| (more than 16 bytes)
   {
-    std::vector<uint8> plain_text(33);
+    std::vector<uint8> input(32);
     std::vector<uint8> iv(17);
-    EXPECT_FALSE(EncryptInternal(CreateAesCbcAlgorithm(iv),
-                                 key,
-                                 plain_text.data(),
-                                 plain_text.size(),
-                                 &output));
+    EXPECT_FALSE(EncryptInternal(
+        CreateAesCbcAlgorithm(iv), key, input.data(), input.size(), &output));
+    EXPECT_FALSE(DecryptInternal(
+        CreateAesCbcAlgorithm(iv), key, input.data(), input.size(), &output));
   }
 
   // Give an input that is too large (would cause integer overflow when
   // narrowing to an int).
   {
     std::vector<uint8> iv(16);
 
     // Pretend the input is large. Don't pass data pointer as NULL in case that
     // is special cased; the implementation shouldn't actually dereference the
     // data.
-    const unsigned char* plain_text = iv.data();
-    unsigned plain_text_len = INT_MAX - 3;
+    const unsigned char* input = iv.data();
+    unsigned input_len = INT_MAX - 3;
 
     EXPECT_FALSE(EncryptInternal(
-        CreateAesCbcAlgorithm(iv), key, plain_text, plain_text_len, &output));
+        CreateAesCbcAlgorithm(iv), key, input, input_len, &output));
+    EXPECT_FALSE(DecryptInternal(
+        CreateAesCbcAlgorithm(iv), key, input, input_len, &output));
   }
 
   // Fail importing the key (too few bytes specified)
   {
     WebKit::WebCryptoKeyType type;
     scoped_ptr<WebKit::WebCryptoKeyHandle> handle;
 
     std::vector<uint8> key_raw(1);
     std::vector<uint8> iv(16);
 
@@ skipping 92 matching lines @@
     WebKit::WebCryptoKey key = ImportSecretKeyFromRawHexString(
         test.key,
         CreateAlgorithm(WebKit::WebCryptoAlgorithmIdAesCbc),
         WebKit::WebCryptoKeyUsageEncrypt | WebKit::WebCryptoKeyUsageDecrypt);
 
     std::vector<uint8> plain_text = HexStringToBytes(test.plain_text);
     std::vector<uint8> iv = HexStringToBytes(test.iv);
 
     WebKit::WebArrayBuffer output;
 
+    // Test encryption.
     EXPECT_TRUE(EncryptInternal(CreateAesCbcAlgorithm(iv),
                                 key,
                                 plain_text.data(),
                                 plain_text.size(),
                                 &output));
+    ExpectArrayBufferMatchesHex(test.cipher_text, output);
 
-    ExpectArrayBufferMatchesHex(test.cipher_text, output);
+    // Test decryption.
+    std::vector<uint8> cipher_text = HexStringToBytes(test.cipher_text);
+    EXPECT_TRUE(DecryptInternal(CreateAesCbcAlgorithm(iv),
+                                key,
+                                cipher_text.data(),
+                                cipher_text.size(),
+                                &output));
+    ExpectArrayBufferMatchesHex(test.plain_text, output);
+
+    const unsigned kAesCbcBlockSize = 16;
+
+    // Decrypt with a padding error by stripping the last block. This also ends
+    // up testing decryption over empty cipher text.
+    if (cipher_text.size() >= kAesCbcBlockSize) {
+      EXPECT_FALSE(DecryptInternal(CreateAesCbcAlgorithm(iv),

[Ryan Sleevi, 2013/09/25 20:36:14]

This reminds me: There should be a test for Encrypt with a 0 byte input buffer.
This is legal, and is used to 'randomize' the padding (since it effectively ends
up encrypting the IV).

[eroman, 2013/09/25 20:39:13]

The last test vector in AesCbcSampleSets does that (search for EmptyEncrypt). Is
this different from what you had in mind?

[Ryan Sleevi, 2013/09/25 20:41:05]

D'oh. Missed that. Yup.

+                                   key,
+                                   cipher_text.data(),
+                                   cipher_text.size() - kAesCbcBlockSize,
+                                   &output));
+    }
+
+    // Decrypt cipher text which is not block-aligned, by stripping a few bytes
+    // off the cipher text.
+    if (cipher_text.size() > 3) {
+      EXPECT_FALSE(DecryptInternal(CreateAesCbcAlgorithm(iv),
+                                   key,
+                                   cipher_text.data(),
+                                   cipher_text.size() - 3,
+                                   &output));
+    }
   }
 }
 
 }  // namespace content