[sync] Fix decryption failure caused by missing user_key

components/sync/base/nigori.cc

Index: components/sync/base/nigori.cc
diff --git a/components/sync/base/nigori.cc b/components/sync/base/nigori.cc
index 03c61b23472a34410579a40e987186db3bcde1d8..ef9f7d6eeb728e4380c1ae122803f279163ad9a9 100644
--- a/components/sync/base/nigori.cc
+++ b/components/sync/base/nigori.cc
@@ -79,6 +79,11 @@ bool Nigori::InitByDerivation(const std::string& hostname,
   if (!user_salt->GetRawKey(&raw_user_salt))
     return false;
 
+  // Kuser = PBKDF2(P, Suser, Nuser, 16)
+  user_key_ = SymmetricKey::DeriveKeyFromPassword(
+      SymmetricKey::AES, password, raw_user_salt, kUserIterations,
+      kDerivedKeySizeInBits);

[pavely, 2017/04/10 21:27:29]

Could you keep DCHECK and return value check for InitByDerivation as it
generates nigori to be consumed by older clients. 

[Patrick Noland, 2017/04/10 23:43:06]

Done.

+
   // Kenc = PBKDF2(P, Suser, Nenc, 16)
   encryption_key_ = SymmetricKey::DeriveKeyFromPassword(
       SymmetricKey::AES, password, raw_user_salt, kEncryptionIterations,
@@ -94,8 +99,11 @@ bool Nigori::InitByDerivation(const std::string& hostname,
   return encryption_key_ && mac_key_;
 }
 
-bool Nigori::InitByImport(const std::string& encryption_key,
+bool Nigori::InitByImport(const std::string& user_key,
+                          const std::string& encryption_key,
                           const std::string& mac_key) {
+  user_key_ = SymmetricKey::Import(SymmetricKey::AES, user_key);

[pavely, 2017/04/10 21:27:29]

Could you add a comment here or in nigori.h explaining that user_key_ is not
used anywhere, but since legacy clients check for it we should keep it around.

[Patrick Noland, 2017/04/10 23:43:06]

Done.

+
   encryption_key_ = SymmetricKey::Import(SymmetricKey::AES, encryption_key);
   DCHECK(encryption_key_);
 
@@ -223,11 +231,14 @@ bool Nigori::Decrypt(const std::string& encrypted, std::string* value) const {
   return true;
 }
 
-bool Nigori::ExportKeys(std::string* encryption_key,
+bool Nigori::ExportKeys(std::string* user_key,
+                        std::string* encryption_key,
                         std::string* mac_key) const {
   DCHECK(encryption_key);
   DCHECK(mac_key);
 
+  user_key_->GetRawKey(user_key);
+
   return encryption_key_->GetRawKey(encryption_key) &&
          mac_key_->GetRawKey(mac_key);
 }