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authorEthan Yonker <dees_troy@teamw.in>2016-12-07 20:55:01 +0100
committerDees Troy <dees_troy@teamw.in>2016-12-13 21:16:42 +0100
commitbd7492de28963b7e74e8e5d3f17ec9a5a287d9c3 (patch)
tree563c0c0d1edb2dcf81db4c4d0e39f49a37a894c9 /crypto/ext4crypt/KeyStorage.cpp
parentAdd boot slot support (diff)
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Diffstat (limited to 'crypto/ext4crypt/KeyStorage.cpp')
-rw-r--r--crypto/ext4crypt/KeyStorage.cpp349
1 files changed, 349 insertions, 0 deletions
diff --git a/crypto/ext4crypt/KeyStorage.cpp b/crypto/ext4crypt/KeyStorage.cpp
new file mode 100644
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--- /dev/null
+++ b/crypto/ext4crypt/KeyStorage.cpp
@@ -0,0 +1,349 @@
+/*
+ * 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 <vector>
+
+#include <errno.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <iostream>
+
+#include <openssl/sha.h>
+
+#include <android-base/file.h>
+//#include <android-base/logging.h>
+
+#include <cutils/properties.h>
+
+#include <hardware/hw_auth_token.h>
+
+#include <keymaster/authorization_set.h>
+
+extern "C" {
+
+#include "crypto_scrypt.h"
+}
+
+#define ERROR 1
+#define LOG(x) std::cout
+#define PLOG(x) std::cout
+
+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* kFn_encrypted_key = "encrypted_key";
+static const char* kFn_keymaster_key_blob = "keymaster_key_blob";
+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 std::string hashSecdiscardable(const std::string& secdiscardable) {
+ 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 secdiscardableHashingPrefix = "Android secdiscardable SHA512";
+ secdiscardableHashingPrefix.resize(SHA512_CBLOCK);
+ SHA512_Update(&c, secdiscardableHashingPrefix.data(), secdiscardableHashingPrefix.size());
+ SHA512_Update(&c, secdiscardable.data(), secdiscardable.size());
+ std::string res(SHA512_DIGEST_LENGTH, '\0');
+ SHA512_Final(reinterpret_cast<uint8_t*>(&res[0]), &c);
+ return res;
+}
+
+/*static bool generateKeymasterKey(Keymaster& keymaster, const KeyAuthentication& auth,
+ const std::string& appId, std::string* key) {
+ auto paramBuilder = keymaster::AuthorizationSetBuilder()
+ .AesEncryptionKey(AES_KEY_BYTES * 8)
+ .Authorization(keymaster::TAG_BLOCK_MODE, KM_MODE_GCM)
+ .Authorization(keymaster::TAG_MIN_MAC_LENGTH, GCM_MAC_BYTES * 8)
+ .Authorization(keymaster::TAG_PADDING, KM_PAD_NONE);
+ addStringParam(&paramBuilder, keymaster::TAG_APPLICATION_ID, appId);
+ if (auth.token.empty()) {
+ LOG(DEBUG) << "Creating key that doesn't need auth token";
+ paramBuilder.Authorization(keymaster::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(keymaster::TAG_USER_SECURE_ID, at->user_id);
+ paramBuilder.Authorization(keymaster::TAG_USER_AUTH_TYPE, HW_AUTH_PASSWORD);
+ paramBuilder.Authorization(keymaster::TAG_AUTH_TIMEOUT, AUTH_TIMEOUT);
+ }
+ return keymaster.generateKey(paramBuilder.build(), key);
+}*/
+
+static keymaster::AuthorizationSetBuilder 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)
+ .Authorization(keymaster::TAG_PADDING, KM_PAD_NONE);
+ addStringParam(&paramBuilder, keymaster::TAG_APPLICATION_ID, appId);
+ if (!auth.token.empty()) {
+ LOG(DEBUG) << "Supplying auth token to Keymaster";
+ addStringParam(&paramBuilder, 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;
+}
+
+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 writeStringToFile(const std::string& payload, const std::string& filename) {
+ if (!android::base::WriteStringToFile(payload, filename)) {
+ PLOG(ERROR) << "Failed to write to " << filename;
+ return false;
+ }
+ return true;
+}*/
+
+static std::string getStretching() {
+ 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,
+ std::string* appId) {
+ std::string stretched;
+ if (!stretchSecret(stretching, auth.secret, salt, &stretched)) return false;
+ *appId = hashSecdiscardable(secdiscardable) + stretched;
+ return true;
+}
+
+/*bool storeKey(const std::string& dir, const KeyAuthentication& auth, const std::string& 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;
+ if (ReadRandomBytes(SECDISCARDABLE_BYTES, secdiscardable) != OK) {
+ // TODO status_t plays badly with PLOG, fix it.
+ LOG(ERROR) << "Random read failed";
+ return false;
+ }
+ if (!writeStringToFile(secdiscardable, dir + "/" + kFn_secdiscardable)) return false;
+ std::string stretching = auth.secret.empty() ? kStretch_nopassword : getStretching();
+ 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, &appId)) return false;
+ 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;
+ std::string encryptedKey;
+ if (!encryptWithKeymasterKey(keymaster, kmKey, auth, appId, key, &encryptedKey)) return false;
+ if (!writeStringToFile(encryptedKey, dir + "/" + kFn_encrypted_key)) return false;
+ return true;
+}*/
+
+bool retrieveKey(const std::string& dir, const KeyAuthentication& auth, std::string* key) {
+ 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;
+ if (!readFileToString(dir + "/" + kFn_secdiscardable, &secdiscardable)) 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, &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);
+}
+
+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;
+}
+
+static bool secdiscardSecdiscardable(const std::string& dir) {
+ if (ForkExecvp(
+ std::vector<std::string>{kSecdiscardPath, "--", dir + "/" + kFn_secdiscardable}) != 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.
+ success &= deleteKey(dir);
+ success &= secdiscardSecdiscardable(dir);
+ success &= recursiveDeleteKey(dir);
+ return success;
+}
+
+} // namespace vold
+} // namespace android