Ignore Crypto-Key header values that do not have "dh" values

This aligns Chrome with the latest change to the webpush-encryption
specification: https://github.com/webpush-wg/webpush-encryption/pull/7

BUG=

Review-Url: https://codereview.chromium.org/2114703002
Cr-Commit-Position: refs/heads/master@{#403264}

components/gcm_driver/crypto/gcm_encryption_provider.cc

@@ -150,7 +150,29 @@ void GCMEncryptionProvider::DecryptMessage(
     return;
   }
 
-  if (crypto_key_header_iterator.dh().empty()) {
+  // Ignore values that don't include the "dh" property. When using VAPID, it is
+  // valid for the application server to supply multiple values.
+  while (crypto_key_header_iterator.dh().empty() &&
+         crypto_key_header_iterator.GetNext()) {}
+
+  bool valid_crypto_key_header = false;
+  std::string dh;
+
+  if (!crypto_key_header_iterator.dh().empty()) {
+    dh = crypto_key_header_iterator.dh();
+    valid_crypto_key_header = true;
+
+    // Guard against the "dh" property being included more than once.
+    while (crypto_key_header_iterator.GetNext()) {
+      if (crypto_key_header_iterator.dh().empty())
+        continue;
+
+      valid_crypto_key_header = false;
+      break;
+    }
+  }
+
+  if (!valid_crypto_key_header) {
     DLOG(ERROR) << "Invalid values supplied in the Crypto-Key header";
     callback.Run(DECRYPTION_RESULT_INVALID_CRYPTO_KEY_HEADER,
                  IncomingMessage());
@@ -164,8 +186,7 @@ void GCMEncryptionProvider::DecryptMessage(
                       base::Bind(&GCMEncryptionProvider::DecryptMessageWithKey,
                                  weak_ptr_factory_.GetWeakPtr(), message,
                                  callback, encryption_header_iterator.salt(),
-                                 crypto_key_header_iterator.dh(),
-                                 encryption_header_iterator.rs()));
+                                 dh, encryption_header_iterator.rs()));
 }
 
 void GCMEncryptionProvider::DidGetEncryptionInfo(

components/gcm_driver/crypto/gcm_encryption_provider_unittest.cc

@@ -40,7 +40,15 @@ const char kInvalidEncryptionHeader[] = "keyid";
 const char kValidCryptoKeyHeader[] =
     "keyid=foo;dh=BL_UGhfudEkXMUd4U4-D4nP5KHxKjQHsW6j88ybbehXM7fqi1OMFefDUEi0eJ"
     "vsKfyVBWYkQjH-lSPJKxjAyslg";
+const char kValidThreeValueCryptoKeyHeader[] =
+    "keyid=foo,keyid=bar,keyid=baz;dh=BL_UGhfudEkXMUd4U4-D4nP5KHxKjQHsW6j88ybbe"
+    "hXM7fqi1OMFefDUEi0eJvsKfyVBWYkQjH-lSPJKxjAyslg";
+
 const char kInvalidCryptoKeyHeader[] = "keyid";
+const char kInvalidThreeValueCryptoKeyHeader[] =
+    "keyid=foo,dh=BL_UGhfudEkXMUd4U4-D4nP5KHxKjQHsW6j88ybbehXM7fqi1OMFefDUEi0eJ"
+    "vsKfyVBWYkQjH-lSPJKxjAyslg,keyid=baz,dh=BL_UGhfudEkXMUd4U4-D4nP5KHxKjQHsW6"
+    "j88ybbehXM7fqi1OMFefDUEi0eJvsKfyVBWYkQjH-lSPJKxjAyslg";
 
 }  // namespace
 
@@ -204,7 +212,7 @@ TEST_F(GCMEncryptionProviderTest, VerifiesEncryptionHeaderParsing) {
 }
 
 TEST_F(GCMEncryptionProviderTest, VerifiesCryptoKeyHeaderParsing) {
-  // The Encryption-Key header must be parsable and contain valid values.
+  // The Crypto-Key header must be parsable and contain valid values.
   // Note that this is more extensively tested in EncryptionHeaderParsersTest.
 
   IncomingMessage invalid_message;
@@ -217,7 +225,7 @@ TEST_F(GCMEncryptionProviderTest, VerifiesCryptoKeyHeaderParsing) {
             decryption_result());
 
   IncomingMessage valid_message;
-  valid_message.data["encryption"] = kInvalidEncryptionHeader;
+  valid_message.data["encryption"] = kValidEncryptionHeader;
   valid_message.data["crypto-key"] = kValidCryptoKeyHeader;
   valid_message.raw_data = "foo";
 
@@ -226,6 +234,34 @@ TEST_F(GCMEncryptionProviderTest, VerifiesCryptoKeyHeaderParsing) {
             decryption_result());
 }
 
+TEST_F(GCMEncryptionProviderTest, VerifiesCryptoKeyHeaderParsingThirdValue) {
+  // The Crypto-Key header must be parsable and contain valid values, in which
+  // values will be ignored unless they contain a "dh" property.
+
+  IncomingMessage valid_message;
+  valid_message.data["encryption"] = kValidEncryptionHeader;
+  valid_message.data["crypto-key"] = kValidThreeValueCryptoKeyHeader;
+  valid_message.raw_data = "foo";
+
+  ASSERT_NO_FATAL_FAILURE(Decrypt(valid_message));
+  EXPECT_NE(GCMEncryptionProvider::DECRYPTION_RESULT_INVALID_CRYPTO_KEY_HEADER,
+            decryption_result());
+}
+
+TEST_F(GCMEncryptionProviderTest, VerifiesCryptoKeyHeaderSingleDhEntry) {
+  // The Crypto-Key header must include at most one value that contains the
+  // "dh" property. Having more than once occurrence is forbidden.
+
+  IncomingMessage valid_message;
+  valid_message.data["encryption"] = kValidEncryptionHeader;
+  valid_message.data["crypto-key"] = kInvalidThreeValueCryptoKeyHeader;
+  valid_message.raw_data = "foo";
+
+  ASSERT_NO_FATAL_FAILURE(Decrypt(valid_message));
+  EXPECT_EQ(GCMEncryptionProvider::DECRYPTION_RESULT_INVALID_CRYPTO_KEY_HEADER,
+            decryption_result());
+}
+
 TEST_F(GCMEncryptionProviderTest, VerifiesExistingKeys) {
   // When both headers are valid, the encryption keys still must be known to
   // the GCM key store before the message can be decrypted.