Increase the master key size to 256 bits
NIAP certification finds that the 128 bit key size is insufficient
and requires a 256 bit key size. This change increases the
size of new master keys to 256 bits. Any existing master keys are
not changed and continue to be supported.
A new BlobType, TYPE_MASTER_KEY_AES256, is used to signal when a
key is the new larger size.
Bug: 121272336
Test: (1) Ran Keystore CTS tests against Walleye.
(2) Created keys in build without change, moved to build
with change and verified old key could be loaded and
used. Also, a new key could be created with the
increased size and could be reloaded after a reboot.
Change-Id: If00331c303e6cc7bc95a2ab624d0e19bec4e587e
diff --git a/keystore/user_state.cpp b/keystore/user_state.cpp
index 6026227..bc3f6d9 100644
--- a/keystore/user_state.cpp
+++ b/keystore/user_state.cpp
@@ -142,7 +142,8 @@
ResponseCode UserState::writeMasterKey(const android::String8& pw) {
std::vector<uint8_t> passwordKey(MASTER_KEY_SIZE_BYTES);
generateKeyFromPassword(passwordKey, pw, mSalt);
- Blob masterKeyBlob(mMasterKey.data(), mMasterKey.size(), mSalt, sizeof(mSalt), TYPE_MASTER_KEY);
+ Blob masterKeyBlob(mMasterKey.data(), mMasterKey.size(), mSalt, sizeof(mSalt),
+ TYPE_MASTER_KEY_AES256);
auto lockedEntry = LockedKeyBlobEntry::get(mMasterKeyEntry);
return lockedEntry.writeBlobs(masterKeyBlob, {}, passwordKey, STATE_NO_ERROR);
}
@@ -171,7 +172,12 @@
salt = nullptr;
}
- std::vector<uint8_t> passwordKey(MASTER_KEY_SIZE_BYTES);
+ size_t masterKeySize = MASTER_KEY_SIZE_BYTES;
+ if (rawBlob.type == TYPE_MASTER_KEY) {
+ masterKeySize = SHA1_DIGEST_SIZE_BYTES;
+ }
+
+ std::vector<uint8_t> passwordKey(masterKeySize);
generateKeyFromPassword(passwordKey, pw, salt);
Blob masterKeyBlob, dummyBlob;
ResponseCode response;
@@ -180,7 +186,10 @@
if (response == ResponseCode::SYSTEM_ERROR) {
return response;
}
- if (response == ResponseCode::NO_ERROR && masterKeyBlob.getLength() == MASTER_KEY_SIZE_BYTES) {
+
+ size_t masterKeyBlobLength = static_cast<size_t>(masterKeyBlob.getLength());
+
+ if (response == ResponseCode::NO_ERROR && masterKeyBlobLength == masterKeySize) {
// If salt was missing, generate one and write a new master key file with the salt.
if (salt == nullptr) {
if (!generateSalt()) {