Support Keymaster 2 configuration and key upgrading
Bug: 27212248
Change-Id: I96bd9a442f4f535ba6ea44c9e81bcc1fee0ec471
diff --git a/KeyStorage.cpp b/KeyStorage.cpp
index 986f403..e6c91f5 100644
--- a/KeyStorage.cpp
+++ b/KeyStorage.cpp
@@ -23,6 +23,7 @@
#include <vector>
#include <errno.h>
+#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
@@ -66,6 +67,7 @@
static const std::string kStretchPrefix_scrypt = "scrypt ";
static const char* kFn_encrypted_key = "encrypted_key";
static const char* kFn_keymaster_key_blob = "keymaster_key_blob";
+static const char* kFn_keymaster_key_blob_upgraded = "keymaster_key_blob_upgraded";
static const char* kFn_salt = "salt";
static const char* kFn_secdiscardable = "secdiscardable";
static const char* kFn_stretching = "stretching";
@@ -122,8 +124,8 @@
return keymaster.generateKey(paramBuilder.build(), key);
}
-static keymaster::AuthorizationSetBuilder beginParams(const KeyAuthentication& auth,
- const std::string& appId) {
+static keymaster::AuthorizationSet beginParams(const KeyAuthentication& auth,
+ const std::string& appId) {
auto paramBuilder = keymaster::AuthorizationSetBuilder()
.Authorization(keymaster::TAG_BLOCK_MODE, KM_MODE_GCM)
.Authorization(keymaster::TAG_MAC_LENGTH, GCM_MAC_BYTES * 8)
@@ -133,45 +135,7 @@
LOG(DEBUG) << "Supplying auth token to Keymaster";
addStringParam(¶mBuilder, keymaster::TAG_AUTH_TOKEN, auth.token);
}
- return paramBuilder;
-}
-
-static bool encryptWithKeymasterKey(Keymaster& keymaster, const std::string& key,
- const KeyAuthentication& auth, const std::string& appId,
- const std::string& message, std::string* ciphertext) {
- auto params = beginParams(auth, appId).build();
- keymaster::AuthorizationSet outParams;
- auto opHandle = keymaster.begin(KM_PURPOSE_ENCRYPT, key, params, &outParams);
- if (!opHandle) return false;
- keymaster_blob_t nonceBlob;
- if (!outParams.GetTagValue(keymaster::TAG_NONCE, &nonceBlob)) {
- LOG(ERROR) << "GCM encryption but no nonce generated";
- return false;
- }
- // nonceBlob here is just a pointer into existing data, must not be freed
- std::string nonce(reinterpret_cast<const char*>(nonceBlob.data), nonceBlob.data_length);
- if (!checkSize("nonce", nonce.size(), GCM_NONCE_BYTES)) return false;
- std::string body;
- if (!opHandle.updateCompletely(message, &body)) return false;
-
- std::string mac;
- if (!opHandle.finishWithOutput(&mac)) return false;
- if (!checkSize("mac", mac.size(), GCM_MAC_BYTES)) return false;
- *ciphertext = nonce + body + mac;
- return true;
-}
-
-static bool decryptWithKeymasterKey(Keymaster& keymaster, const std::string& key,
- const KeyAuthentication& auth, const std::string& appId,
- const std::string& ciphertext, std::string* message) {
- auto nonce = ciphertext.substr(0, GCM_NONCE_BYTES);
- auto bodyAndMac = ciphertext.substr(GCM_NONCE_BYTES);
- auto params = addStringParam(beginParams(auth, appId), keymaster::TAG_NONCE, nonce).build();
- auto opHandle = keymaster.begin(KM_PURPOSE_DECRYPT, key, params);
- if (!opHandle) return false;
- if (!opHandle.updateCompletely(bodyAndMac, message)) return false;
- if (!opHandle.finish()) return false;
- return true;
+ return paramBuilder.build();
}
static bool readFileToString(const std::string& filename, std::string* result) {
@@ -190,6 +154,79 @@
return true;
}
+static KeymasterOperation begin(Keymaster& keymaster, const std::string& dir,
+ keymaster_purpose_t purpose,
+ const keymaster::AuthorizationSet &keyParams,
+ const keymaster::AuthorizationSet &opParams,
+ keymaster::AuthorizationSet* outParams) {
+ auto kmKeyPath = dir + "/" + kFn_keymaster_key_blob;
+ std::string kmKey;
+ if (!readFileToString(kmKeyPath, &kmKey)) return KeymasterOperation();
+ keymaster::AuthorizationSet inParams;
+ inParams.push_back(keyParams);
+ inParams.push_back(opParams);
+ for (;;) {
+ auto opHandle = keymaster.begin(purpose, kmKey, inParams, outParams);
+ if (opHandle) {
+ return opHandle;
+ }
+ if (opHandle.error() != KM_ERROR_KEY_REQUIRES_UPGRADE) return opHandle;
+ LOG(DEBUG) << "Upgrading key: " << dir;
+ std::string newKey;
+ if (!keymaster.upgradeKey(kmKey, keyParams, &newKey)) return KeymasterOperation();
+ auto newKeyPath = dir + "/" + kFn_keymaster_key_blob_upgraded;
+ if (!writeStringToFile(newKey, newKeyPath)) return KeymasterOperation();
+ if (rename(newKeyPath.c_str(), kmKeyPath.c_str()) != 0) {
+ PLOG(ERROR) << "Unable to move upgraded key to location: " << kmKeyPath;
+ return KeymasterOperation();
+ }
+ if (!keymaster.deleteKey(kmKey)) {
+ LOG(ERROR) << "Key deletion failed during upgrade, continuing anyway: " << dir;
+ }
+ kmKey = newKey;
+ LOG(INFO) << "Key upgraded: " << dir;
+ }
+}
+
+static bool encryptWithKeymasterKey(Keymaster& keymaster, const std::string& dir,
+ const keymaster::AuthorizationSet &keyParams,
+ const std::string& message, std::string* ciphertext) {
+ keymaster::AuthorizationSet opParams;
+ keymaster::AuthorizationSet outParams;
+ auto opHandle = begin(keymaster, dir, KM_PURPOSE_ENCRYPT, keyParams, opParams, &outParams);
+ if (!opHandle) return false;
+ keymaster_blob_t nonceBlob;
+ if (!outParams.GetTagValue(keymaster::TAG_NONCE, &nonceBlob)) {
+ LOG(ERROR) << "GCM encryption but no nonce generated";
+ return false;
+ }
+ // nonceBlob here is just a pointer into existing data, must not be freed
+ std::string nonce(reinterpret_cast<const char*>(nonceBlob.data), nonceBlob.data_length);
+ if (!checkSize("nonce", nonce.size(), GCM_NONCE_BYTES)) return false;
+ std::string body;
+ if (!opHandle.updateCompletely(message, &body)) return false;
+
+ std::string mac;
+ if (!opHandle.finish(&mac)) return false;
+ if (!checkSize("mac", mac.size(), GCM_MAC_BYTES)) return false;
+ *ciphertext = nonce + body + mac;
+ return true;
+}
+
+static bool decryptWithKeymasterKey(Keymaster& keymaster, const std::string& dir,
+ const keymaster::AuthorizationSet &keyParams,
+ const std::string& ciphertext, std::string* message) {
+ auto nonce = ciphertext.substr(0, GCM_NONCE_BYTES);
+ auto bodyAndMac = ciphertext.substr(GCM_NONCE_BYTES);
+ auto opParams = addStringParam(keymaster::AuthorizationSetBuilder(),
+ keymaster::TAG_NONCE, nonce).build();
+ auto opHandle = begin(keymaster, dir, KM_PURPOSE_DECRYPT, keyParams, opParams, nullptr);
+ if (!opHandle) return false;
+ if (!opHandle.updateCompletely(bodyAndMac, message)) return false;
+ if (!opHandle.finish(nullptr)) return false;
+ return true;
+}
+
static std::string getStretching() {
char paramstr[PROPERTY_VALUE_MAX];
@@ -273,8 +310,9 @@
std::string kmKey;
if (!generateKeymasterKey(keymaster, auth, appId, &kmKey)) return false;
if (!writeStringToFile(kmKey, dir + "/" + kFn_keymaster_key_blob)) return false;
+ auto keyParams = beginParams(auth, appId);
std::string encryptedKey;
- if (!encryptWithKeymasterKey(keymaster, kmKey, auth, appId, key, &encryptedKey)) return false;
+ if (!encryptWithKeymasterKey(keymaster, dir, keyParams, key, &encryptedKey)) return false;
if (!writeStringToFile(encryptedKey, dir + "/" + kFn_encrypted_key)) return false;
return true;
}
@@ -296,13 +334,12 @@
}
std::string appId;
if (!generateAppId(auth, stretching, salt, secdiscardable, &appId)) return false;
- std::string kmKey;
- if (!readFileToString(dir + "/" + kFn_keymaster_key_blob, &kmKey)) return false;
std::string encryptedMessage;
if (!readFileToString(dir + "/" + kFn_encrypted_key, &encryptedMessage)) return false;
Keymaster keymaster;
if (!keymaster) return false;
- return decryptWithKeymasterKey(keymaster, kmKey, auth, appId, encryptedMessage, key);
+ auto keyParams = beginParams(auth, appId);
+ return decryptWithKeymasterKey(keymaster, dir, keyParams, encryptedMessage, key);
}
static bool deleteKey(const std::string& dir) {
