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Diffstat (limited to 'crypto/ext4crypt/KeyStorage.cpp')
| -rw-r--r-- | crypto/ext4crypt/KeyStorage.cpp | 349 |
1 files changed, 349 insertions, 0 deletions
diff --git a/crypto/ext4crypt/KeyStorage.cpp b/crypto/ext4crypt/KeyStorage.cpp new file mode 100644 index 000000000..199520e9d --- /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(¶mBuilder, 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(¶mBuilder, keymaster::TAG_APPLICATION_ID, appId); + if (!auth.token.empty()) { + 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; +} + +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 |