decrypt: AOSP 10 requires the use of fscrypt
fscrypt aosp doc: https://source.android.com/security/encryption/file-based
kernel fscrypt doc: https://www.kernel.org/doc/html/v4.18/filesystems/fscrypt.html
This commit implements the ability for TWRP to use fscrypt to decrypt
files on the fscrypt implementation. It has been implemented mostly
in a new successor library to e4crypt called libtwrpfscrypt. Most of the
code was ported from AOSP vold.
Notable updates include:
- updated policy storage by libtar
- lookup of fbe policies by libtwrpfscrypt
- threaded keystore operations
Big thanks to Dees_Troy for the initial trailblazing
of encryption in TWRP.
Change-Id: I69cd2eba3693a9914e00213d4943229635d0cdae
diff --git a/crypto/fscrypt/KeyStorage.cpp b/crypto/fscrypt/KeyStorage.cpp
new file mode 100755
index 0000000..c68daa1
--- /dev/null
+++ b/crypto/fscrypt/KeyStorage.cpp
@@ -0,0 +1,598 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "KeyStorage.h"
+
+#include "Keymaster.h"
+#include "ScryptParameters.h"
+#include "Utils.h"
+#include "Checkpoint.h"
+
+#include <thread>
+#include <vector>
+
+#include <errno.h>
+#include <stdio.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <openssl/err.h>
+#include <openssl/evp.h>
+#include <openssl/sha.h>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/unique_fd.h>
+#include <android-base/properties.h>
+
+#include <cutils/properties.h>
+
+#include <hardware/hw_auth_token.h>
+#include <keymasterV4_0/authorization_set.h>
+#include <keymasterV4_0/keymaster_utils.h>
+
+extern "C" {
+
+#include "crypto_scrypt.h"
+}
+
+namespace android {
+namespace vold {
+
+const KeyAuthentication kEmptyAuthentication{"", ""};
+
+static constexpr size_t AES_KEY_BYTES = 32;
+static constexpr size_t GCM_NONCE_BYTES = 12;
+static constexpr size_t GCM_MAC_BYTES = 16;
+static constexpr size_t SALT_BYTES = 1 << 4;
+static constexpr size_t SECDISCARDABLE_BYTES = 1 << 14;
+static constexpr size_t STRETCHED_BYTES = 1 << 6;
+
+static constexpr uint32_t AUTH_TIMEOUT = 30; // Seconds
+
+static const char* kCurrentVersion = "1";
+static const char* kRmPath = "/system/bin/rm";
+static const char* kSecdiscardPath = "/system/bin/secdiscard";
+static const char* kStretch_none = "none";
+static const char* kStretch_nopassword = "nopassword";
+static const std::string kStretchPrefix_scrypt = "scrypt ";
+static const char* kHashPrefix_secdiscardable = "Android secdiscardable SHA512";
+static const char* kHashPrefix_keygen = "Android key wrapping key generation SHA512";
+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";
+static const char* kFn_version = "version";
+
+static bool checkSize(const std::string& kind, size_t actual, size_t expected) {
+ if (actual != expected) {
+ LOG(ERROR) << "Wrong number of bytes in " << kind << ", expected " << expected << " got "
+ << actual;
+ return false;
+ }
+ return true;
+}
+
+static void hashWithPrefix(char const* prefix, const std::string& tohash, std::string* res) {
+ SHA512_CTX c;
+
+ SHA512_Init(&c);
+ // Personalise the hashing by introducing a fixed prefix.
+ // Hashing applications should use personalization except when there is a
+ // specific reason not to; see section 4.11 of https://www.schneier.com/skein1.3.pdf
+ std::string hashingPrefix = prefix;
+ hashingPrefix.resize(SHA512_CBLOCK);
+ SHA512_Update(&c, hashingPrefix.data(), hashingPrefix.size());
+ SHA512_Update(&c, tohash.data(), tohash.size());
+ res->assign(SHA512_DIGEST_LENGTH, '\0');
+ SHA512_Final(reinterpret_cast<uint8_t*>(&(*res)[0]), &c);
+}
+
+static bool generateKeymasterKey(Keymaster& keymaster, const KeyAuthentication& auth,
+ const std::string& appId, std::string* key) {
+ auto paramBuilder = km::AuthorizationSetBuilder()
+ .AesEncryptionKey(AES_KEY_BYTES * 8)
+ .GcmModeMinMacLen(GCM_MAC_BYTES * 8)
+ .Authorization(km::TAG_APPLICATION_ID, km::support::blob2hidlVec(appId));
+ if (auth.token.empty()) {
+ LOG(DEBUG) << "Creating key that doesn't need auth token";
+ paramBuilder.Authorization(km::TAG_NO_AUTH_REQUIRED);
+ } else {
+ LOG(DEBUG) << "Auth token required for key";
+ if (auth.token.size() != sizeof(hw_auth_token_t)) {
+ LOG(ERROR) << "Auth token should be " << sizeof(hw_auth_token_t) << " bytes, was "
+ << auth.token.size() << " bytes";
+ return false;
+ }
+ const hw_auth_token_t* at = reinterpret_cast<const hw_auth_token_t*>(auth.token.data());
+ paramBuilder.Authorization(km::TAG_USER_SECURE_ID, at->user_id);
+ paramBuilder.Authorization(km::TAG_USER_AUTH_TYPE, km::HardwareAuthenticatorType::PASSWORD);
+ paramBuilder.Authorization(km::TAG_AUTH_TIMEOUT, AUTH_TIMEOUT);
+ }
+ return keymaster.generateKey(paramBuilder, key);
+}
+
+static std::pair<km::AuthorizationSet, km::HardwareAuthToken> beginParams(
+ const KeyAuthentication& auth, const std::string& appId) {
+ auto paramBuilder = km::AuthorizationSetBuilder()
+ .GcmModeMacLen(GCM_MAC_BYTES * 8)
+ .Authorization(km::TAG_APPLICATION_ID, km::support::blob2hidlVec(appId));
+ km::HardwareAuthToken authToken;
+ if (!auth.token.empty()) {
+ LOG(DEBUG) << "Supplying auth token to Keymaster";
+ authToken = km::support::hidlVec2AuthToken(km::support::blob2hidlVec(auth.token));
+ }
+ return {paramBuilder, authToken};
+}
+
+static bool readFileToString(const std::string& filename, std::string* result) {
+ if (!android::base::ReadFileToString(filename, result)) {
+ PLOG(ERROR) << "Failed to read from " << filename;
+ return false;
+ }
+ return true;
+}
+
+static bool readRandomBytesOrLog(size_t count, std::string* out) {
+ auto status = ReadRandomBytes(count, *out);
+ if (status != OK) {
+ LOG(ERROR) << "Random read failed with status: " << status;
+ return false;
+ }
+ return true;
+}
+
+bool createSecdiscardable(const std::string& filename, std::string* hash) {
+ std::string secdiscardable;
+ if (!readRandomBytesOrLog(SECDISCARDABLE_BYTES, &secdiscardable)) return false;
+ if (!writeStringToFile(secdiscardable, filename)) return false;
+ hashWithPrefix(kHashPrefix_secdiscardable, secdiscardable, hash);
+ return true;
+}
+
+bool readSecdiscardable(const std::string& filename, std::string* hash) {
+ std::string secdiscardable;
+ if (!readFileToString(filename, &secdiscardable)) return false;
+ hashWithPrefix(kHashPrefix_secdiscardable, secdiscardable, hash);
+ return true;
+}
+
+// static void deferedKmDeleteKey(const std::string& kmkey) {
+// while (!android::base::WaitForProperty("vold.checkpoint_committed", "1")) {
+// LOG(ERROR) << "Wait for boot timed out";
+// }
+// Keymaster keymaster;
+// if (!keymaster || !keymaster.deleteKey(kmkey)) {
+// LOG(ERROR) << "Defered Key deletion failed during upgrade";
+// }
+// }
+
+bool kmDeleteKey(Keymaster& keymaster, const std::string& kmKey) {
+ return true;
+ // bool needs_cp = cp_needsCheckpoint();
+
+ // if (needs_cp) {
+ // std::thread(deferedKmDeleteKey, kmKey).detach();
+ // LOG(INFO) << "Deferring Key deletion during upgrade";
+ // return true;
+ // } else {
+ // return keymaster.deleteKey(kmKey);
+ // }
+}
+
+static KeymasterOperation begin(Keymaster& keymaster, const std::string& dir,
+ km::KeyPurpose purpose, const km::AuthorizationSet& keyParams,
+ const km::AuthorizationSet& opParams,
+ const km::HardwareAuthToken& authToken,
+ km::AuthorizationSet* outParams, bool keepOld) {
+ auto kmKeyPath = dir + "/" + kFn_keymaster_key_blob;
+ std::string kmKey;
+ if (!readFileToString(kmKeyPath, &kmKey)) return KeymasterOperation();
+ km::AuthorizationSet inParams(keyParams);
+ inParams.append(opParams.begin(), opParams.end());
+ for (;;) {
+ auto opHandle = keymaster.begin(purpose, kmKey, inParams, authToken, outParams);
+ if (opHandle) {
+ return opHandle;
+ }
+ if (opHandle.errorCode() != km::ErrorCode::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 (!keepOld) {
+ // if (rename(newKeyPath.c_str(), kmKeyPath.c_str()) != 0) {
+ // PLOG(ERROR) << "Unable to move upgraded key to location: " << kmKeyPath;
+ // return KeymasterOperation();
+ // }
+ // if (!android::vold::FsyncDirectory(dir)) {
+ // LOG(ERROR) << "Key dir sync failed: " << dir;
+ // return KeymasterOperation();
+ // }
+ // if (!kmDeleteKey(keymaster, kmKey)) {
+ // LOG(ERROR) << "Key deletion failed during upgrade, continuing anyway: " << dir;
+ // }
+ // }
+ kmKey = newKey;
+ LOG(INFO) << "Key upgraded in memory: " << dir;
+ }
+}
+
+static bool encryptWithKeymasterKey(Keymaster& keymaster, const std::string& dir,
+ const km::AuthorizationSet& keyParams,
+ const km::HardwareAuthToken& authToken, const KeyBuffer& message,
+ std::string* ciphertext, bool keepOld) {
+ km::AuthorizationSet opParams;
+ km::AuthorizationSet outParams;
+ auto opHandle = begin(keymaster, dir, km::KeyPurpose::ENCRYPT, keyParams, opParams, authToken,
+ &outParams, keepOld);
+ if (!opHandle) return false;
+ auto nonceBlob = outParams.GetTagValue(km::TAG_NONCE);
+ if (!nonceBlob.isOk()) {
+ 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.value()[0]),
+ nonceBlob.value().size());
+ 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 km::AuthorizationSet& keyParams,
+ const km::HardwareAuthToken& authToken,
+ const std::string& ciphertext, KeyBuffer* message,
+ bool keepOld) {
+ auto nonce = ciphertext.substr(0, GCM_NONCE_BYTES);
+ auto bodyAndMac = ciphertext.substr(GCM_NONCE_BYTES);
+ auto opParams = km::AuthorizationSetBuilder().Authorization(km::TAG_NONCE,
+ km::support::blob2hidlVec(nonce));
+ auto opHandle = begin(keymaster, dir, km::KeyPurpose::DECRYPT, keyParams, opParams, authToken,
+ nullptr, keepOld);
+ if (!opHandle) return false;
+ if (!opHandle.updateCompletely(bodyAndMac, message)) return false;
+ if (!opHandle.finish(nullptr)) return false;
+ return true;
+}
+
+static std::string getStretching(const KeyAuthentication& auth) {
+ if (!auth.usesKeymaster()) {
+ return kStretch_none;
+ } else if (auth.secret.empty()) {
+ return kStretch_nopassword;
+ } else {
+ char paramstr[PROPERTY_VALUE_MAX];
+
+ property_get(SCRYPT_PROP, paramstr, SCRYPT_DEFAULTS);
+ return std::string() + kStretchPrefix_scrypt + paramstr;
+ }
+}
+
+static bool stretchingNeedsSalt(const std::string& stretching) {
+ return stretching != kStretch_nopassword && stretching != kStretch_none;
+}
+
+static bool stretchSecret(const std::string& stretching, const std::string& secret,
+ const std::string& salt, std::string* stretched) {
+ if (stretching == kStretch_nopassword) {
+ if (!secret.empty()) {
+ LOG(WARNING) << "Password present but stretching is nopassword";
+ // Continue anyway
+ }
+ stretched->clear();
+ } else if (stretching == kStretch_none) {
+ *stretched = secret;
+ } else if (std::equal(kStretchPrefix_scrypt.begin(), kStretchPrefix_scrypt.end(),
+ stretching.begin())) {
+ int Nf, rf, pf;
+ if (!parse_scrypt_parameters(stretching.substr(kStretchPrefix_scrypt.size()).c_str(), &Nf,
+ &rf, &pf)) {
+ LOG(ERROR) << "Unable to parse scrypt params in stretching: " << stretching;
+ return false;
+ }
+ stretched->assign(STRETCHED_BYTES, '\0');
+ if (crypto_scrypt(reinterpret_cast<const uint8_t*>(secret.data()), secret.size(),
+ reinterpret_cast<const uint8_t*>(salt.data()), salt.size(), 1 << Nf,
+ 1 << rf, 1 << pf, reinterpret_cast<uint8_t*>(&(*stretched)[0]),
+ stretched->size()) != 0) {
+ LOG(ERROR) << "scrypt failed with params: " << stretching;
+ return false;
+ }
+ } else {
+ LOG(ERROR) << "Unknown stretching type: " << stretching;
+ return false;
+ }
+ return true;
+}
+
+static bool generateAppId(const KeyAuthentication& auth, const std::string& stretching,
+ const std::string& salt, const std::string& secdiscardable_hash,
+ std::string* appId) {
+ std::string stretched;
+ if (!stretchSecret(stretching, auth.secret, salt, &stretched)) return false;
+ *appId = secdiscardable_hash + stretched;
+ return true;
+}
+
+static void logOpensslError() {
+ LOG(ERROR) << "Openssl error: " << ERR_get_error();
+}
+
+static bool encryptWithoutKeymaster(const std::string& preKey, const KeyBuffer& plaintext,
+ std::string* ciphertext) {
+ std::string key;
+ hashWithPrefix(kHashPrefix_keygen, preKey, &key);
+ key.resize(AES_KEY_BYTES);
+ if (!readRandomBytesOrLog(GCM_NONCE_BYTES, ciphertext)) return false;
+ auto ctx = std::unique_ptr<EVP_CIPHER_CTX, decltype(&::EVP_CIPHER_CTX_free)>(
+ EVP_CIPHER_CTX_new(), EVP_CIPHER_CTX_free);
+ if (!ctx) {
+ logOpensslError();
+ return false;
+ }
+ if (1 != EVP_EncryptInit_ex(ctx.get(), EVP_aes_256_gcm(), NULL,
+ reinterpret_cast<const uint8_t*>(key.data()),
+ reinterpret_cast<const uint8_t*>(ciphertext->data()))) {
+ logOpensslError();
+ return false;
+ }
+ ciphertext->resize(GCM_NONCE_BYTES + plaintext.size() + GCM_MAC_BYTES);
+ int outlen;
+ if (1 != EVP_EncryptUpdate(
+ ctx.get(), reinterpret_cast<uint8_t*>(&(*ciphertext)[0] + GCM_NONCE_BYTES),
+ &outlen, reinterpret_cast<const uint8_t*>(plaintext.data()), plaintext.size())) {
+ logOpensslError();
+ return false;
+ }
+ if (outlen != static_cast<int>(plaintext.size())) {
+ LOG(ERROR) << "GCM ciphertext length should be " << plaintext.size() << " was " << outlen;
+ return false;
+ }
+ if (1 != EVP_EncryptFinal_ex(
+ ctx.get(),
+ reinterpret_cast<uint8_t*>(&(*ciphertext)[0] + GCM_NONCE_BYTES + plaintext.size()),
+ &outlen)) {
+ logOpensslError();
+ return false;
+ }
+ if (outlen != 0) {
+ LOG(ERROR) << "GCM EncryptFinal should be 0, was " << outlen;
+ return false;
+ }
+ if (1 != EVP_CIPHER_CTX_ctrl(ctx.get(), EVP_CTRL_GCM_GET_TAG, GCM_MAC_BYTES,
+ reinterpret_cast<uint8_t*>(&(*ciphertext)[0] + GCM_NONCE_BYTES +
+ plaintext.size()))) {
+ logOpensslError();
+ return false;
+ }
+ return true;
+}
+
+static bool decryptWithoutKeymaster(const std::string& preKey, const std::string& ciphertext,
+ KeyBuffer* plaintext) {
+ if (ciphertext.size() < GCM_NONCE_BYTES + GCM_MAC_BYTES) {
+ LOG(ERROR) << "GCM ciphertext too small: " << ciphertext.size();
+ return false;
+ }
+ std::string key;
+ hashWithPrefix(kHashPrefix_keygen, preKey, &key);
+ key.resize(AES_KEY_BYTES);
+ auto ctx = std::unique_ptr<EVP_CIPHER_CTX, decltype(&::EVP_CIPHER_CTX_free)>(
+ EVP_CIPHER_CTX_new(), EVP_CIPHER_CTX_free);
+ if (!ctx) {
+ logOpensslError();
+ return false;
+ }
+ if (1 != EVP_DecryptInit_ex(ctx.get(), EVP_aes_256_gcm(), NULL,
+ reinterpret_cast<const uint8_t*>(key.data()),
+ reinterpret_cast<const uint8_t*>(ciphertext.data()))) {
+ logOpensslError();
+ return false;
+ }
+ *plaintext = KeyBuffer(ciphertext.size() - GCM_NONCE_BYTES - GCM_MAC_BYTES);
+ int outlen;
+ if (1 != EVP_DecryptUpdate(ctx.get(), reinterpret_cast<uint8_t*>(&(*plaintext)[0]), &outlen,
+ reinterpret_cast<const uint8_t*>(ciphertext.data() + GCM_NONCE_BYTES),
+ plaintext->size())) {
+ logOpensslError();
+ return false;
+ }
+ if (outlen != static_cast<int>(plaintext->size())) {
+ LOG(ERROR) << "GCM plaintext length should be " << plaintext->size() << " was " << outlen;
+ return false;
+ }
+ if (1 != EVP_CIPHER_CTX_ctrl(ctx.get(), EVP_CTRL_GCM_SET_TAG, GCM_MAC_BYTES,
+ const_cast<void*>(reinterpret_cast<const void*>(
+ ciphertext.data() + GCM_NONCE_BYTES + plaintext->size())))) {
+ logOpensslError();
+ return false;
+ }
+ if (1 != EVP_DecryptFinal_ex(ctx.get(),
+ reinterpret_cast<uint8_t*>(&(*plaintext)[0] + plaintext->size()),
+ &outlen)) {
+ logOpensslError();
+ return false;
+ }
+ if (outlen != 0) {
+ LOG(ERROR) << "GCM EncryptFinal should be 0, was " << outlen;
+ return false;
+ }
+ return true;
+}
+
+bool pathExists(const std::string& path) {
+ return access(path.c_str(), F_OK) == 0;
+}
+
+bool storeKey(const std::string& dir, const KeyAuthentication& auth, const KeyBuffer& key) {
+ if (TEMP_FAILURE_RETRY(mkdir(dir.c_str(), 0700)) == -1) {
+ PLOG(ERROR) << "key mkdir " << dir;
+ return false;
+ }
+ if (!writeStringToFile(kCurrentVersion, dir + "/" + kFn_version)) return false;
+ std::string secdiscardable_hash;
+ if (!createSecdiscardable(dir + "/" + kFn_secdiscardable, &secdiscardable_hash)) return false;
+ std::string stretching = getStretching(auth);
+ if (!writeStringToFile(stretching, dir + "/" + kFn_stretching)) return false;
+ std::string salt;
+ if (stretchingNeedsSalt(stretching)) {
+ if (ReadRandomBytes(SALT_BYTES, salt) != OK) {
+ LOG(ERROR) << "Random read failed";
+ return false;
+ }
+ if (!writeStringToFile(salt, dir + "/" + kFn_salt)) return false;
+ }
+ std::string appId;
+ if (!generateAppId(auth, stretching, salt, secdiscardable_hash, &appId)) return false;
+ std::string encryptedKey;
+ if (auth.usesKeymaster()) {
+ Keymaster keymaster;
+ if (!keymaster) return false;
+ std::string kmKey;
+ if (!generateKeymasterKey(keymaster, auth, appId, &kmKey)) return false;
+ if (!writeStringToFile(kmKey, dir + "/" + kFn_keymaster_key_blob)) return false;
+ km::AuthorizationSet keyParams;
+ km::HardwareAuthToken authToken;
+ std::tie(keyParams, authToken) = beginParams(auth, appId);
+ if (!encryptWithKeymasterKey(keymaster, dir, keyParams, authToken, key, &encryptedKey,
+ false))
+ return false;
+ } else {
+ if (!encryptWithoutKeymaster(appId, key, &encryptedKey)) return false;
+ }
+ if (!writeStringToFile(encryptedKey, dir + "/" + kFn_encrypted_key)) return false;
+ if (!FsyncDirectory(dir)) return false;
+ return true;
+}
+
+bool storeKeyAtomically(const std::string& key_path, const std::string& tmp_path,
+ const KeyAuthentication& auth, const KeyBuffer& key) {
+ if (pathExists(key_path)) {
+ LOG(ERROR) << "Already exists, cannot create key at: " << key_path;
+ return false;
+ }
+ if (pathExists(tmp_path)) {
+ LOG(DEBUG) << "Already exists, destroying: " << tmp_path;
+ destroyKey(tmp_path); // May be partially created so ignore errors
+ }
+ if (!storeKey(tmp_path, auth, key)) return false;
+ if (rename(tmp_path.c_str(), key_path.c_str()) != 0) {
+ PLOG(ERROR) << "Unable to move new key to location: " << key_path;
+ return false;
+ }
+ LOG(DEBUG) << "Created key: " << key_path;
+ return true;
+}
+
+bool retrieveKey(const std::string& dir, const KeyAuthentication& auth, KeyBuffer* key,
+ bool keepOld) {
+ std::string version;
+ if (!readFileToString(dir + "/" + kFn_version, &version)) return false;
+ if (version != kCurrentVersion) {
+ LOG(ERROR) << "Version mismatch, expected " << kCurrentVersion << " got " << version;
+ return false;
+ }
+ std::string secdiscardable_hash;
+ if (!readSecdiscardable(dir + "/" + kFn_secdiscardable, &secdiscardable_hash)) return false;
+ std::string stretching;
+ if (!readFileToString(dir + "/" + kFn_stretching, &stretching)) return false;
+ std::string salt;
+ if (stretchingNeedsSalt(stretching)) {
+ if (!readFileToString(dir + "/" + kFn_salt, &salt)) return false;
+ }
+ std::string appId;
+ if (!generateAppId(auth, stretching, salt, secdiscardable_hash, &appId)) return false;
+ std::string encryptedMessage;
+ if (!readFileToString(dir + "/" + kFn_encrypted_key, &encryptedMessage)) return false;
+ if (auth.usesKeymaster()) {
+ Keymaster keymaster;
+ if (!keymaster) return false;
+ km::AuthorizationSet keyParams;
+ km::HardwareAuthToken authToken;
+ std::tie(keyParams, authToken) = beginParams(auth, appId);
+ if (!decryptWithKeymasterKey(keymaster, dir, keyParams, authToken, encryptedMessage, key,
+ keepOld))
+ return false;
+ } else {
+ if (!decryptWithoutKeymaster(appId, encryptedMessage, key)) return false;
+ }
+ return true;
+}
+
+static bool deleteKey(const std::string& dir) {
+ std::string kmKey;
+ if (!readFileToString(dir + "/" + kFn_keymaster_key_blob, &kmKey)) return false;
+ Keymaster keymaster;
+ if (!keymaster) return false;
+ if (!keymaster.deleteKey(kmKey)) return false;
+ return true;
+}
+
+bool runSecdiscardSingle(const std::string& file) {
+ if (ForkExecvp(std::vector<std::string>{kSecdiscardPath, "--", file}) != 0) {
+ LOG(ERROR) << "secdiscard failed";
+ return false;
+ }
+ return true;
+}
+
+static bool recursiveDeleteKey(const std::string& dir) {
+ if (ForkExecvp(std::vector<std::string>{kRmPath, "-rf", dir}) != 0) {
+ LOG(ERROR) << "recursive delete failed";
+ return false;
+ }
+ return true;
+}
+
+bool destroyKey(const std::string& dir) {
+ bool success = true;
+ // Try each thing, even if previous things failed.
+ bool uses_km = pathExists(dir + "/" + kFn_keymaster_key_blob);
+ if (uses_km) {
+ success &= deleteKey(dir);
+ }
+ auto secdiscard_cmd = std::vector<std::string>{
+ kSecdiscardPath,
+ "--",
+ dir + "/" + kFn_encrypted_key,
+ dir + "/" + kFn_secdiscardable,
+ };
+ if (uses_km) {
+ secdiscard_cmd.emplace_back(dir + "/" + kFn_keymaster_key_blob);
+ }
+ if (ForkExecvp(secdiscard_cmd) != 0) {
+ LOG(ERROR) << "secdiscard failed";
+ success = false;
+ }
+ success &= recursiveDeleteKey(dir);
+ return success;
+}
+
+} // namespace vold
+} // namespace android