platform_system_core/gatekeeperd/gatekeeperd.cpp

/*
 * Copyright (C) 2015 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 "gatekeeperd"

#include "gatekeeperd.h"

#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <memory>

#include <KeyMintUtils.h>
#include <android-base/logging.h>
#include <android-base/properties.h>
#include <android/binder_ibinder.h>
#include <android/binder_manager.h>
#include <binder/IPCThreadState.h>
#include <binder/IServiceManager.h>
#include <binder/PermissionCache.h>
#include <gatekeeper/password_handle.h>  // for password_handle_t
#include <hardware/hw_auth_token.h>
#include <libgsi/libgsi.h>
#include <log/log.h>
#include <utils/String16.h>

#include <aidl/android/hardware/security/keymint/HardwareAuthToken.h>
#include <aidl/android/security/authorization/IKeystoreAuthorization.h>
#include <hidl/HidlSupport.h>

using android::sp;
using android::hardware::Return;
using android::hardware::gatekeeper::V1_0::GatekeeperResponse;
using android::hardware::gatekeeper::V1_0::GatekeeperStatusCode;

using AidlGatekeeperEnrollResp = aidl::android::hardware::gatekeeper::GatekeeperEnrollResponse;
using AidlGatekeeperVerifyResp = aidl::android::hardware::gatekeeper::GatekeeperVerifyResponse;

using GKResponseCode = ::android::service::gatekeeper::ResponseCode;
using ::aidl::android::hardware::security::keymint::HardwareAuthenticatorType;
using ::aidl::android::hardware::security::keymint::HardwareAuthToken;
using ::aidl::android::hardware::security::keymint::km_utils::authToken2AidlVec;
using ::aidl::android::security::authorization::IKeystoreAuthorization;

namespace android {

static const String16 KEYGUARD_PERMISSION("android.permission.ACCESS_KEYGUARD_SECURE_STORAGE");
static const String16 DUMP_PERMISSION("android.permission.DUMP");
constexpr const char gatekeeperServiceName[] = "android.hardware.gatekeeper.IGatekeeper/default";

GateKeeperProxy::GateKeeperProxy() {
    clear_state_if_needed_done = false;
    hw_device = IGatekeeper::getService();
    ::ndk::SpAIBinder ks2Binder(AServiceManager_getService(gatekeeperServiceName));
    aidl_hw_device = AidlIGatekeeper::fromBinder(ks2Binder);
    is_running_gsi = android::base::GetBoolProperty(android::gsi::kGsiBootedProp, false);

    if (!aidl_hw_device && !hw_device) {
        LOG(ERROR) << "Could not find Gatekeeper device, which makes me very sad.";
    }
}

void GateKeeperProxy::store_sid(uint32_t userId, uint64_t sid) {
    char filename[21];
    snprintf(filename, sizeof(filename), "%u", userId);
    int fd = open(filename, O_WRONLY | O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR);
    if (fd < 0) {
        ALOGE("could not open file: %s: %s", filename, strerror(errno));
        return;
    }
    write(fd, &sid, sizeof(sid));
    close(fd);
}

void GateKeeperProxy::clear_state_if_needed() {
    if (clear_state_if_needed_done) {
        return;
    }

    if (mark_cold_boot() && !is_running_gsi) {
        ALOGI("cold boot: clearing state");
        if (aidl_hw_device) {
            aidl_hw_device->deleteAllUsers();
        } else if (hw_device) {
            hw_device->deleteAllUsers([](const GatekeeperResponse&) {});
        }
    }

    clear_state_if_needed_done = true;
}

bool GateKeeperProxy::mark_cold_boot() {
    const char* filename = ".coldboot";
    if (access(filename, F_OK) == -1) {
        int fd = open(filename, O_WRONLY | O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR);
        if (fd < 0) {
            ALOGE("could not open file: %s : %s", filename, strerror(errno));
            return false;
        }
        close(fd);
        return true;
    }
    return false;
}

void GateKeeperProxy::maybe_store_sid(uint32_t userId, uint64_t sid) {
    char filename[21];
    snprintf(filename, sizeof(filename), "%u", userId);
    if (access(filename, F_OK) == -1) {
        store_sid(userId, sid);
    }
}

uint64_t GateKeeperProxy::read_sid(uint32_t userId) {
    char filename[21];
    uint64_t sid;
    snprintf(filename, sizeof(filename), "%u", userId);
    int fd = open(filename, O_RDONLY);
    if (fd < 0) return 0;
    read(fd, &sid, sizeof(sid));
    close(fd);
    return sid;
}

void GateKeeperProxy::clear_sid(uint32_t userId) {
    char filename[21];
    snprintf(filename, sizeof(filename), "%u", userId);
    if (remove(filename) < 0 && errno != ENOENT) {
        ALOGE("%s: could not remove file [%s], attempting 0 write", __func__, strerror(errno));
        store_sid(userId, 0);
    }
}

Status GateKeeperProxy::adjust_userId(uint32_t userId, uint32_t* hw_userId) {
    static constexpr uint32_t kGsiOffset = 1000000;
    if (userId >= kGsiOffset) {
        return Status::fromExceptionCode(Status::EX_ILLEGAL_ARGUMENT);
    }

    if ((aidl_hw_device == nullptr) && (hw_device == nullptr)) {
        return Status::fromExceptionCode(Status::EX_ILLEGAL_STATE);
    }

    if (is_running_gsi) {
        *hw_userId = userId + kGsiOffset;
        return Status::ok();
    }
    *hw_userId = userId;
    return Status::ok();
}

#define GK_ERROR *gkResponse = GKResponse::error(), Status::ok()

Status GateKeeperProxy::enroll(int32_t userId,
                               const std::optional<std::vector<uint8_t>>& currentPasswordHandle,
                               const std::optional<std::vector<uint8_t>>& currentPassword,
                               const std::vector<uint8_t>& desiredPassword,
                               GKResponse* gkResponse) {
    IPCThreadState* ipc = IPCThreadState::self();
    const int calling_pid = ipc->getCallingPid();
    const int calling_uid = ipc->getCallingUid();
    if (!PermissionCache::checkPermission(KEYGUARD_PERMISSION, calling_pid, calling_uid)) {
        return GK_ERROR;
    }

    // Make sure to clear any state from before factory reset as soon as a credential is
    // enrolled (which may happen during device setup).
    clear_state_if_needed();

    // need a desired password to enroll
    if (desiredPassword.size() == 0) return GK_ERROR;

    if (!aidl_hw_device && !hw_device) {
        LOG(ERROR) << "has no HAL to talk to";
        return GK_ERROR;
    }

    android::hardware::hidl_vec<uint8_t> curPwdHandle;
    android::hardware::hidl_vec<uint8_t> curPwd;

    if (currentPasswordHandle && currentPassword) {
        if (hw_device) {
            // Hidl Implementations expects passwordHandle to be in
            // gatekeeper::password_handle_t format.
            if (currentPasswordHandle->size() != sizeof(gatekeeper::password_handle_t)) {
                LOG(INFO) << "Password handle has wrong length";
                return GK_ERROR;
            }
        }
        curPwdHandle.setToExternal(const_cast<uint8_t*>(currentPasswordHandle->data()),
                                   currentPasswordHandle->size());
        curPwd.setToExternal(const_cast<uint8_t*>(currentPassword->data()),
                             currentPassword->size());
    }

    android::hardware::hidl_vec<uint8_t> newPwd;
    newPwd.setToExternal(const_cast<uint8_t*>(desiredPassword.data()), desiredPassword.size());

    uint32_t hw_userId = 0;
    Status result = adjust_userId(userId, &hw_userId);
    if (!result.isOk()) {
        return result;
    }

    uint64_t secureUserId = 0;
    if (aidl_hw_device) {
        // AIDL gatekeeper service
        AidlGatekeeperEnrollResp rsp;
        auto result = aidl_hw_device->enroll(hw_userId, curPwdHandle, curPwd, newPwd, &rsp);
        if (!result.isOk()) {
            LOG(ERROR) << "enroll transaction failed";
            return GK_ERROR;
        }
        if (rsp.statusCode >= AidlIGatekeeper::STATUS_OK) {
            *gkResponse = GKResponse::ok({rsp.data.begin(), rsp.data.end()});
            secureUserId = static_cast<uint64_t>(rsp.secureUserId);
        } else if (rsp.statusCode == AidlIGatekeeper::ERROR_RETRY_TIMEOUT && rsp.timeoutMs > 0) {
            *gkResponse = GKResponse::retry(rsp.timeoutMs);
        } else {
            *gkResponse = GKResponse::error();
        }
    } else if (hw_device) {
        // HIDL gatekeeper service
        Return<void> hwRes = hw_device->enroll(
                hw_userId, curPwdHandle, curPwd, newPwd,
                [&gkResponse](const GatekeeperResponse& rsp) {
                    if (rsp.code >= GatekeeperStatusCode::STATUS_OK) {
                        *gkResponse = GKResponse::ok({rsp.data.begin(), rsp.data.end()});
                    } else if (rsp.code == GatekeeperStatusCode::ERROR_RETRY_TIMEOUT &&
                               rsp.timeout > 0) {
                        *gkResponse = GKResponse::retry(rsp.timeout);
                    } else {
                        *gkResponse = GKResponse::error();
                    }
                });
        if (!hwRes.isOk()) {
            LOG(ERROR) << "enroll transaction failed";
            return GK_ERROR;
        }
        if (gkResponse->response_code() == GKResponseCode::OK) {
            if (gkResponse->payload().size() != sizeof(gatekeeper::password_handle_t)) {
                LOG(ERROR) << "HAL returned password handle of invalid length "
                           << gkResponse->payload().size();
                return GK_ERROR;
            }

            const gatekeeper::password_handle_t* handle =
                    reinterpret_cast<const gatekeeper::password_handle_t*>(
                            gkResponse->payload().data());
            secureUserId = handle->user_id;
        }
    }

    if (gkResponse->response_code() == GKResponseCode::OK && !gkResponse->should_reenroll()) {
        store_sid(userId, secureUserId);

        GKResponse verifyResponse;
        // immediately verify this password so we don't ask the user to enter it again
        // if they just created it.
        auto status = verify(userId, gkResponse->payload(), desiredPassword, &verifyResponse);
        if (!status.isOk() || verifyResponse.response_code() != GKResponseCode::OK) {
            LOG(ERROR) << "Failed to verify password after enrolling";
        }
    }

    return Status::ok();
}

Status GateKeeperProxy::verify(int32_t userId, const ::std::vector<uint8_t>& enrolledPasswordHandle,
                               const ::std::vector<uint8_t>& providedPassword,
                               GKResponse* gkResponse) {
    return verifyChallenge(userId, 0 /* challenge */, enrolledPasswordHandle, providedPassword,
                           gkResponse);
}

Status GateKeeperProxy::verifyChallenge(int32_t userId, int64_t challenge,
                                        const std::vector<uint8_t>& enrolledPasswordHandle,
                                        const std::vector<uint8_t>& providedPassword,
                                        GKResponse* gkResponse) {
    IPCThreadState* ipc = IPCThreadState::self();
    const int calling_pid = ipc->getCallingPid();
    const int calling_uid = ipc->getCallingUid();
    if (!PermissionCache::checkPermission(KEYGUARD_PERMISSION, calling_pid, calling_uid)) {
        return GK_ERROR;
    }

    // can't verify if we're missing either param
    if (enrolledPasswordHandle.size() == 0 || providedPassword.size() == 0) return GK_ERROR;

    if (!aidl_hw_device && !hw_device) {
        LOG(ERROR) << "has no HAL to talk to";
        return GK_ERROR;
    }

    if (hw_device) {
        // Hidl Implementations expects passwordHandle to be in gatekeeper::password_handle_t
        if (enrolledPasswordHandle.size() != sizeof(gatekeeper::password_handle_t)) {
            LOG(INFO) << "Password handle has wrong length";
            return GK_ERROR;
        }
    }

    uint32_t hw_userId = 0;
    Status result = adjust_userId(userId, &hw_userId);
    if (!result.isOk()) {
        return result;
    }

    android::hardware::hidl_vec<uint8_t> curPwdHandle;
    curPwdHandle.setToExternal(const_cast<uint8_t*>(enrolledPasswordHandle.data()),
                               enrolledPasswordHandle.size());
    android::hardware::hidl_vec<uint8_t> enteredPwd;
    enteredPwd.setToExternal(const_cast<uint8_t*>(providedPassword.data()),
                             providedPassword.size());

    uint64_t secureUserId = 0;
    if (aidl_hw_device) {
        // AIDL gatekeeper service
        AidlGatekeeperVerifyResp rsp;
        auto result = aidl_hw_device->verify(hw_userId, challenge, curPwdHandle, enteredPwd, &rsp);
        if (!result.isOk()) {
            LOG(ERROR) << "verify transaction failed";
            return GK_ERROR;
        }
        if (rsp.statusCode >= AidlIGatekeeper::STATUS_OK) {
            secureUserId = rsp.hardwareAuthToken.userId;
            // Serialize HardwareAuthToken to a vector as hw_auth_token_t.
            *gkResponse = GKResponse::ok(
                    authToken2AidlVec(rsp.hardwareAuthToken),
                    rsp.statusCode == AidlIGatekeeper::STATUS_REENROLL /* reenroll */);
        } else if (rsp.statusCode == AidlIGatekeeper::ERROR_RETRY_TIMEOUT) {
            *gkResponse = GKResponse::retry(rsp.timeoutMs);
        } else {
            *gkResponse = GKResponse::error();
        }
    } else if (hw_device) {
        // HIDL gatekeeper service
        Return<void> hwRes = hw_device->verify(
                hw_userId, challenge, curPwdHandle, enteredPwd,
                [&gkResponse](const GatekeeperResponse& rsp) {
                    if (rsp.code >= GatekeeperStatusCode::STATUS_OK) {
                        *gkResponse = GKResponse::ok(
                                {rsp.data.begin(), rsp.data.end()},
                                rsp.code == GatekeeperStatusCode::STATUS_REENROLL /* reenroll */);
                    } else if (rsp.code == GatekeeperStatusCode::ERROR_RETRY_TIMEOUT) {
                        *gkResponse = GKResponse::retry(rsp.timeout);
                    } else {
                        *gkResponse = GKResponse::error();
                    }
                });

        if (!hwRes.isOk()) {
            LOG(ERROR) << "verify transaction failed";
            return GK_ERROR;
        }
        const gatekeeper::password_handle_t* handle =
                reinterpret_cast<const gatekeeper::password_handle_t*>(
                        enrolledPasswordHandle.data());
        secureUserId = handle->user_id;
    }

    if (gkResponse->response_code() == GKResponseCode::OK) {
        if (gkResponse->payload().size() != 0) {
            // try to connect to IKeystoreAuthorization AIDL service first.
            AIBinder* authzAIBinder = AServiceManager_getService("android.security.authorization");
            ::ndk::SpAIBinder authzBinder(authzAIBinder);
            auto authzService = IKeystoreAuthorization::fromBinder(authzBinder);
            if (authzService) {
                if (gkResponse->payload().size() != sizeof(hw_auth_token_t)) {
                    LOG(ERROR) << "Incorrect size of AuthToken payload.";
                    return GK_ERROR;
                }

                const hw_auth_token_t* hwAuthToken =
                        reinterpret_cast<const hw_auth_token_t*>(gkResponse->payload().data());
                HardwareAuthToken authToken;

                authToken.timestamp.milliSeconds = betoh64(hwAuthToken->timestamp);
                authToken.challenge = hwAuthToken->challenge;
                authToken.userId = hwAuthToken->user_id;
                authToken.authenticatorId = hwAuthToken->authenticator_id;
                authToken.authenticatorType = static_cast<HardwareAuthenticatorType>(
                        betoh32(hwAuthToken->authenticator_type));
                authToken.mac.assign(&hwAuthToken->hmac[0], &hwAuthToken->hmac[32]);
                auto result = authzService->addAuthToken(authToken);
                if (!result.isOk()) {
                    LOG(ERROR) << "Failure in sending AuthToken to AuthorizationService.";
                    return GK_ERROR;
                }
            } else {
                LOG(ERROR) << "Cannot deliver auth token. Unable to communicate with "
                              "Keystore.";
                return GK_ERROR;
            }
        }

        maybe_store_sid(userId, secureUserId);
    }

    return Status::ok();
}

Status GateKeeperProxy::getSecureUserId(int32_t userId, int64_t* sid) {
    *sid = read_sid(userId);
    return Status::ok();
}

Status GateKeeperProxy::clearSecureUserId(int32_t userId) {
    IPCThreadState* ipc = IPCThreadState::self();
    const int calling_pid = ipc->getCallingPid();
    const int calling_uid = ipc->getCallingUid();
    if (!PermissionCache::checkPermission(KEYGUARD_PERMISSION, calling_pid, calling_uid)) {
        ALOGE("%s: permission denied for [%d:%d]", __func__, calling_pid, calling_uid);
        return Status::ok();
    }
    clear_sid(userId);

    uint32_t hw_userId = 0;
    Status result = adjust_userId(userId, &hw_userId);
    if (!result.isOk()) {
        return result;
    }

    if (aidl_hw_device) {
        aidl_hw_device->deleteUser(hw_userId);
    } else if (hw_device) {
        hw_device->deleteUser(hw_userId, [](const GatekeeperResponse&) {});
    }
    return Status::ok();
}

Status GateKeeperProxy::reportDeviceSetupComplete() {
    IPCThreadState* ipc = IPCThreadState::self();
    const int calling_pid = ipc->getCallingPid();
    const int calling_uid = ipc->getCallingUid();
    if (!PermissionCache::checkPermission(KEYGUARD_PERMISSION, calling_pid, calling_uid)) {
        ALOGE("%s: permission denied for [%d:%d]", __func__, calling_pid, calling_uid);
        return Status::ok();
    }

    clear_state_if_needed();
    return Status::ok();
}

status_t GateKeeperProxy::dump(int fd, const Vector<String16>&) {
    IPCThreadState* ipc = IPCThreadState::self();
    const int pid = ipc->getCallingPid();
    const int uid = ipc->getCallingUid();
    if (!PermissionCache::checkPermission(DUMP_PERMISSION, pid, uid)) {
        return PERMISSION_DENIED;
    }

    if (aidl_hw_device == nullptr && hw_device == nullptr) {
        const char* result = "Device not available";
        write(fd, result, strlen(result) + 1);
    } else {
        const char* result = "OK";
        write(fd, result, strlen(result) + 1);
    }

    return OK;
}
}  // namespace android