platform_system_security/keystore/keystore_utils.cpp

/*
 * 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.
 */

#define LOG_TAG "keystore"

#include "keystore_utils.h"

#include <errno.h>
#include <string.h>
#include <unistd.h>

#include <log/log.h>
#include <private/android_filesystem_config.h>
#include <private/android_logger.h>

#include <log/log_event_list.h>

#include <keystore/keymaster_types.h>
#include <keystore/keystore_client.h>

#include <android-base/logging.h>
#include <android-base/unique_fd.h>

#include "blob.h"

size_t readFully(int fd, uint8_t* data, size_t size) {
    size_t remaining = size;
    while (remaining > 0) {
        ssize_t n = TEMP_FAILURE_RETRY(read(fd, data, remaining));
        if (n <= 0) {
            return size - remaining;
        }
        data += n;
        remaining -= n;
    }
    return size;
}

size_t writeFully(int fd, uint8_t* data, size_t size) {
    size_t remaining = size;
    while (remaining > 0) {
        ssize_t n = TEMP_FAILURE_RETRY(write(fd, data, remaining));
        if (n < 0) {
            ALOGW("write failed: %s", strerror(errno));
            return size - remaining;
        }
        data += n;
        remaining -= n;
    }
    if (TEMP_FAILURE_RETRY(fsync(fd)) == -1) {
        ALOGW("fsync failed: %s", strerror(errno));
        return -1;
    }
    return size;
}

std::string getContainingDirectory(const std::string& filename) {
    std::string containing_dir;
    size_t last_pos;
    size_t pos = std::string::npos;

    __builtin_add_overflow(filename.size(), -1, &last_pos);

    // strip all trailing '/'
    while ((pos = filename.find_last_of('/', last_pos)) == last_pos && pos != 0) {
        --last_pos;
    }

    if (pos == 0) {
        containing_dir = "/";
    } else if (pos == std::string::npos) {
        containing_dir = ".";
    } else {
        containing_dir = filename.substr(0, pos);
    }

    return containing_dir;
}

void fsyncDirectory(const std::string& path) {
    android::base::unique_fd dir_fd(TEMP_FAILURE_RETRY(open(path.c_str(), O_DIRECTORY | O_RDONLY)));

    if (dir_fd < 0) {
        LOG(WARNING) << "Could not open dir: " << path << " error: " << strerror(errno);
        return;
    }

    if (TEMP_FAILURE_RETRY(fsync(dir_fd)) == -1) {
        LOG(WARNING) << "Failed to fsync the directory " << path << " error: " << strerror(errno);
    }

    return;
}

void add_legacy_key_authorizations(int keyType, keystore::AuthorizationSet* params) {
    using namespace keystore;
    params->push_back(TAG_PURPOSE, KeyPurpose::SIGN);
    params->push_back(TAG_PURPOSE, KeyPurpose::VERIFY);
    params->push_back(TAG_PURPOSE, KeyPurpose::ENCRYPT);
    params->push_back(TAG_PURPOSE, KeyPurpose::DECRYPT);
    params->push_back(TAG_PADDING, PaddingMode::NONE);
    if (keyType == EVP_PKEY_RSA) {
        params->push_back(TAG_PADDING, PaddingMode::RSA_PKCS1_1_5_SIGN);
        params->push_back(TAG_PADDING, PaddingMode::RSA_PKCS1_1_5_ENCRYPT);
        params->push_back(TAG_PADDING, PaddingMode::RSA_PSS);
        params->push_back(TAG_PADDING, PaddingMode::RSA_OAEP);
    }
    params->push_back(TAG_DIGEST, Digest::NONE);
    params->push_back(TAG_DIGEST, Digest::MD5);
    params->push_back(TAG_DIGEST, Digest::SHA1);
    params->push_back(TAG_DIGEST, Digest::SHA_2_224);
    params->push_back(TAG_DIGEST, Digest::SHA_2_256);
    params->push_back(TAG_DIGEST, Digest::SHA_2_384);
    params->push_back(TAG_DIGEST, Digest::SHA_2_512);
    params->push_back(TAG_NO_AUTH_REQUIRED);
    params->push_back(TAG_ORIGINATION_EXPIRE_DATETIME, LLONG_MAX);
    params->push_back(TAG_USAGE_EXPIRE_DATETIME, LLONG_MAX);
    params->push_back(TAG_ACTIVE_DATETIME, 0);
}

uid_t get_app_id(uid_t uid) {
    return uid % AID_USER;
}

uid_t get_user_id(uid_t uid) {
    return uid / AID_USER;
}

void log_key_integrity_violation(const char* name, uid_t uid) {
    if (!__android_log_security()) return;
    android_log_event_list(SEC_TAG_KEY_INTEGRITY_VIOLATION)
        << name << int32_t(uid) << LOG_ID_SECURITY;
}

namespace keystore {

hidl_vec<uint8_t> blob2hidlVec(const Blob& blob) {
    hidl_vec<uint8_t> result(blob.getValue(), blob.getValue() + blob.getLength());
    return result;
}

SecurityLevel flagsToSecurityLevel(int32_t flags) {
    switch (flags & (KEYSTORE_FLAG_FALLBACK | KEYSTORE_FLAG_STRONGBOX)) {
    case KEYSTORE_FLAG_FALLBACK:
    // treating Strongbox flag as "don't care" if Fallback is set
    case (KEYSTORE_FLAG_FALLBACK | KEYSTORE_FLAG_STRONGBOX):
        return SecurityLevel::SOFTWARE;
    case KEYSTORE_FLAG_STRONGBOX:
        return SecurityLevel::STRONGBOX;
    default:
        return SecurityLevel::TRUSTED_ENVIRONMENT;
    }
}

uint32_t securityLevelToFlags(SecurityLevel secLevel) {
    switch (secLevel) {
    case SecurityLevel::SOFTWARE:
        return KEYSTORE_FLAG_FALLBACK;
    case SecurityLevel::STRONGBOX:
        return KEYSTORE_FLAG_STRONGBOX;
    default:
        return 0;
    }
}

}  // namespace keystore