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 "IGateKeeperService.h"

#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <stdint.h>
#include <unistd.h>

#include <binder/IPCThreadState.h>
#include <binder/IServiceManager.h>
#include <binder/PermissionCache.h>
#include <gatekeeper/password_handle.h> // for password_handle_t
#include <hardware/gatekeeper.h>
#include <hardware/hw_auth_token.h>
#include <keystore/IKeystoreService.h>
#include <keystore/keystore.h> // For error code
#include <log/log.h>
#include <utils/Log.h>
#include <utils/String16.h>

#include "SoftGateKeeperDevice.h"
#include "IUserManager.h"

namespace android {

static const String16 KEYGUARD_PERMISSION("android.permission.ACCESS_KEYGUARD_SECURE_STORAGE");
static const String16 DUMP_PERMISSION("android.permission.DUMP");

class GateKeeperProxy : public BnGateKeeperService {
public:
    GateKeeperProxy() {
        int ret = hw_get_module_by_class(GATEKEEPER_HARDWARE_MODULE_ID, NULL, &module);
        device = NULL;

        if (ret < 0) {
            ALOGW("falling back to software GateKeeper");
            soft_device.reset(new SoftGateKeeperDevice());
        } else {
            ret = gatekeeper_open(module, &device);
            if (ret < 0)
                LOG_ALWAYS_FATAL_IF(ret < 0, "Unable to open GateKeeper HAL");
        }

        if (mark_cold_boot()) {
            ALOGI("cold boot: clearing state");
            if (device != NULL && device->delete_all_users != NULL) {
                device->delete_all_users(device);
            }
        }
    }

    virtual ~GateKeeperProxy() {
        if (device) gatekeeper_close(device);
    }

    void store_sid(uint32_t uid, uint64_t sid) {
        char filename[21];
        snprintf(filename, sizeof(filename), "%u", uid);
        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);
    }

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

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

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

    virtual int enroll(uint32_t uid,
            const uint8_t *current_password_handle, uint32_t current_password_handle_length,
            const uint8_t *current_password, uint32_t current_password_length,
            const uint8_t *desired_password, uint32_t desired_password_length,
            uint8_t **enrolled_password_handle, uint32_t *enrolled_password_handle_length) {
        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 PERMISSION_DENIED;
        }

        // need a desired password to enroll
        if (desired_password_length == 0) return -EINVAL;

        int ret;
        if (device) {
            const gatekeeper::password_handle_t *handle =
                    reinterpret_cast<const gatekeeper::password_handle_t *>(current_password_handle);

            if (handle != NULL && handle->version != 0 && !handle->hardware_backed) {
                // handle is being re-enrolled from a software version. HAL probably won't accept
                // the handle as valid, so we nullify it and enroll from scratch
                current_password_handle = NULL;
                current_password_handle_length = 0;
                current_password = NULL;
                current_password_length = 0;
            }

            ret = device->enroll(device, uid, current_password_handle, current_password_handle_length,
                    current_password, current_password_length,
                    desired_password, desired_password_length,
                    enrolled_password_handle, enrolled_password_handle_length);
        } else {
            ret = soft_device->enroll(uid,
                    current_password_handle, current_password_handle_length,
                    current_password, current_password_length,
                    desired_password, desired_password_length,
                    enrolled_password_handle, enrolled_password_handle_length);
        }

        if (ret == 0) {
            gatekeeper::password_handle_t *handle =
                    reinterpret_cast<gatekeeper::password_handle_t *>(*enrolled_password_handle);
            store_sid(uid, handle->user_id);
            bool rr;

            // immediately verify this password so we don't ask the user to enter it again
            // if they just created it.
            verify(uid, *enrolled_password_handle, sizeof(password_handle_t), desired_password,
                    desired_password_length, &rr);
        }

        return ret;
    }

    virtual int verify(uint32_t uid,
            const uint8_t *enrolled_password_handle, uint32_t enrolled_password_handle_length,
            const uint8_t *provided_password, uint32_t provided_password_length, bool *request_reenroll) {
        uint8_t *auth_token;
        uint32_t auth_token_length;
        return verifyChallenge(uid, 0, enrolled_password_handle, enrolled_password_handle_length,
                provided_password, provided_password_length,
                &auth_token, &auth_token_length, request_reenroll);
    }

    virtual int verifyChallenge(uint32_t uid, uint64_t challenge,
            const uint8_t *enrolled_password_handle, uint32_t enrolled_password_handle_length,
            const uint8_t *provided_password, uint32_t provided_password_length,
            uint8_t **auth_token, uint32_t *auth_token_length, bool *request_reenroll) {
        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 PERMISSION_DENIED;
        }

        // can't verify if we're missing either param
        if ((enrolled_password_handle_length | provided_password_length) == 0)
            return -EINVAL;

        int ret;
        if (device) {
            const gatekeeper::password_handle_t *handle =
                    reinterpret_cast<const gatekeeper::password_handle_t *>(enrolled_password_handle);
            // handle version 0 does not have hardware backed flag, and thus cannot be upgraded to
            // a HAL if there was none before
            if (handle->version == 0 || handle->hardware_backed) {
                ret = device->verify(device, uid, challenge,
                    enrolled_password_handle, enrolled_password_handle_length,
                    provided_password, provided_password_length, auth_token, auth_token_length,
                    request_reenroll);
            } else {
                // upgrade scenario, a HAL has been added to this device where there was none before
                SoftGateKeeperDevice soft_dev;
                ret = soft_dev.verify(uid, challenge,
                    enrolled_password_handle, enrolled_password_handle_length,
                    provided_password, provided_password_length, auth_token, auth_token_length,
                    request_reenroll);

                if (ret == 0) {
                    // success! re-enroll with HAL
                    *request_reenroll = true;
                }
            }
        } else {
            ret = soft_device->verify(uid, challenge,
                enrolled_password_handle, enrolled_password_handle_length,
                provided_password, provided_password_length, auth_token, auth_token_length,
                request_reenroll);
        }

        if (ret == 0 && *auth_token != NULL && *auth_token_length > 0) {
            // TODO: cache service?
            sp<IServiceManager> sm = defaultServiceManager();
            sp<IBinder> binder = sm->getService(String16("android.security.keystore"));
            sp<IKeystoreService> service = interface_cast<IKeystoreService>(binder);
            if (service != NULL) {
                status_t ret = service->addAuthToken(*auth_token, *auth_token_length);
                if (ret != ResponseCode::NO_ERROR) {
                    ALOGE("Falure sending auth token to KeyStore: %d", ret);
                }
            } else {
                ALOGE("Unable to communicate with KeyStore");
            }
        }

        if (ret == 0) {
            maybe_store_sid(uid, reinterpret_cast<const gatekeeper::password_handle_t *>(
                        enrolled_password_handle)->user_id);
        }

        return ret;
    }

    virtual uint64_t getSecureUserId(uint32_t uid) {
        uint64_t sid = read_sid(uid);
         if (sid == 0) {
            // might be a work profile, look up the parent
            sp<IServiceManager> sm = defaultServiceManager();
            sp<IBinder> binder = sm->getService(String16("user"));
            sp<IUserManager> um = interface_cast<IUserManager>(binder);
            int32_t parent = um->getCredentialOwnerProfile(uid);
            if (parent < 0) {
                return 0;
            } else if (parent != (int32_t) uid) {
                return read_sid(parent);
            }
        }
        return sid;

    }

    virtual void clearSecureUserId(uint32_t uid) {
        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;
        }
        clear_sid(uid);

        if (device != NULL && device->delete_user != NULL) {
            device->delete_user(device, uid);
        }
    }

    virtual status_t 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 (device == NULL) {
            const char *result = "Device not available";
            write(fd, result, strlen(result) + 1);
        } else {
            const char *result = "OK";
            write(fd, result, strlen(result) + 1);
        }

        return NO_ERROR;
    }

private:
    gatekeeper_device_t *device;
    UniquePtr<SoftGateKeeperDevice> soft_device;
    const hw_module_t *module;
};
}// namespace android

int main(int argc, char* argv[]) {
    ALOGI("Starting gatekeeperd...");
    if (argc < 2) {
        ALOGE("A directory must be specified!");
        return 1;
    }
    if (chdir(argv[1]) == -1) {
        ALOGE("chdir: %s: %s", argv[1], strerror(errno));
        return 1;
    }

    android::sp<android::IServiceManager> sm = android::defaultServiceManager();
    android::sp<android::GateKeeperProxy> proxy = new android::GateKeeperProxy();
    android::status_t ret = sm->addService(
            android::String16("android.service.gatekeeper.IGateKeeperService"), proxy);
    if (ret != android::OK) {
        ALOGE("Couldn't register binder service!");
        return -1;
    }

    /*
     * We're the only thread in existence, so we're just going to process
     * Binder transaction as a single-threaded program.
     */
    android::IPCThreadState::self()->joinThreadPool();
    return 0;
}