[sync::nigori] Small cleanups to encryption code

Switched KeyDerivationParams to class (from struct) and defined
operator!= on it.

Removed a DCHECK which could theoretically trigger when the server sends
invalid data.

Merged some very similar tests for SyncEncryptionHandlerImpl.

Fixed some formatting.

Change-Id: Ia4d6a0baec984872c8c53cdc27bdd870aa3c9f57
Reviewed-on: https://chromium-review.googlesource.com/1236340
Commit-Queue: David Davidović <davidovic@google.com>
Reviewed-by: Marc Treib <treib@chromium.org>
Reviewed-by: vitaliii <vitaliii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594339}

components/sync/base/nigori.cc

@@ -100,8 +100,12 @@ bool KeyDerivationParams::operator==(const KeyDerivationParams& other) const {
          scrypt_salt_ == other.scrypt_salt_;
 }
 
+bool KeyDerivationParams::operator!=(const KeyDerivationParams& other) const {
+  return !(*this == other);
+}
+
 const std::string& KeyDerivationParams::scrypt_salt() const {
-  DCHECK(method_ == KeyDerivationMethod::SCRYPT_8192_8_11);
+  DCHECK_EQ(method_, KeyDerivationMethod::SCRYPT_8192_8_11);
   return scrypt_salt_;
 }
 

components/sync/base/nigori.h

@@ -20,7 +20,7 @@ namespace syncer {
 
 class Nigori;
 
-struct KeyDerivationParams {
+class KeyDerivationParams {
  public:
   static KeyDerivationParams CreateForPbkdf2();
   static KeyDerivationParams CreateForScrypt(const std::string& salt);
@@ -33,6 +33,7 @@ struct KeyDerivationParams {
   KeyDerivationParams(KeyDerivationParams&& other);
   KeyDerivationParams& operator=(const KeyDerivationParams& other);
   bool operator==(const KeyDerivationParams& other) const;
+  bool operator!=(const KeyDerivationParams& other) const;
 
  private:
   KeyDerivationParams(KeyDerivationMethod method,

components/sync/engine_impl/sync_encryption_handler_impl.cc

@@ -224,7 +224,6 @@ KeyDerivationMethod GetKeyDerivationMethodFromNigori(
 std::string GetScryptSaltFromNigori(const sync_pb::NigoriSpecifics& nigori) {
   DCHECK_EQ(nigori.custom_passphrase_key_derivation_method(),
             sync_pb::NigoriSpecifics::SCRYPT_8192_8_11);
-  DCHECK(nigori.has_custom_passphrase_key_derivation_salt());
   std::string decoded_salt;
   bool result = base::Base64Decode(
       nigori.custom_passphrase_key_derivation_salt(), &decoded_salt);
@@ -239,7 +238,6 @@ KeyDerivationParams GetKeyDerivationParamsFromNigori(
     case KeyDerivationMethod::PBKDF2_HMAC_SHA1_1003:
       return KeyDerivationParams::CreateForPbkdf2();
     case KeyDerivationMethod::SCRYPT_8192_8_11:
-      DCHECK(nigori.has_custom_passphrase_key_derivation_salt());
       return KeyDerivationParams::CreateForScrypt(
           GetScryptSaltFromNigori(nigori));
     case KeyDerivationMethod::UNSUPPORTED: