vold: Support Storage keys for FBE
To prevent keys from being compromised if an attacker
acquires read access to kernel memory, some inline
encryption hardware supports protecting the keys in
hardware without software having access to or the
ability to set the plaintext keys. Instead, software
only sees "wrapped keys", which may differ on every boot.
'wrappedkey_v0' fileencryption flag is used to denote
that the device supports inline encryption hardware that
supports this feature. On such devices keymaster is used
to generate keys with STORAGE_KEY tag and export a
per-boot ephemerally wrapped storage key to install it in
the kernel.
The wrapped key framework in the linux kernel ensures the
wrapped key is provided to the inline encryption hardware
where it is unwrapped and the file contents key is derived
to encrypt contents without revealing the plaintext key in
the clear.
Test: FBE validation with Fscrypt v2 + inline crypt + wrapped
key changes kernel.
Bug: 147733587
Change-Id: I1f0de61b56534ec1df9baef075acb74bacd00758
diff --git a/Keymaster.cpp b/Keymaster.cpp
index abee9b2..c3f2912 100644
--- a/Keymaster.cpp
+++ b/Keymaster.cpp
@@ -138,6 +138,27 @@
return true;
}
+bool Keymaster::exportKey(const KeyBuffer& kmKey, std::string* key) {
+ auto kmKeyBlob = km::support::blob2hidlVec(std::string(kmKey.data(), kmKey.size()));
+ km::ErrorCode km_error;
+ auto hidlCb = [&](km::ErrorCode ret, const hidl_vec<uint8_t>& exportedKeyBlob) {
+ km_error = ret;
+ if (km_error != km::ErrorCode::OK) return;
+ if (key)
+ key->assign(reinterpret_cast<const char*>(&exportedKeyBlob[0]), exportedKeyBlob.size());
+ };
+ auto error = mDevice->exportKey(km::KeyFormat::RAW, kmKeyBlob, {}, {}, hidlCb);
+ if (!error.isOk()) {
+ LOG(ERROR) << "export_key failed: " << error.description();
+ return false;
+ }
+ if (km_error != km::ErrorCode::OK) {
+ LOG(ERROR) << "export_key failed, code " << int32_t(km_error);
+ return false;
+ }
+ return true;
+}
+
bool Keymaster::deleteKey(const std::string& key) {
auto keyBlob = km::support::blob2hidlVec(key);
auto error = mDevice->deleteKey(keyBlob);