platform/generic-arm64/smc_service_access_policy.c

/*
 * Copyright (c) 2019 Google Inc. All rights reserved
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files
 * (the "Software"), to deal in the Software without restriction,
 * including without limitation the rights to use, copy, modify, merge,
 * publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#include <err.h>
#include <interface/smc/smc.h>
#include <lib/smc/smc_test.h>
#include <lib/trusty/trusty_app.h>
#include <services/smc/acl.h>
#include <stdbool.h>
#include <string.h>
#include <uapi/trusty_uuid.h>

/* SMC test UUID : {3c321776-548e-4978-b676-843cbf1073e5} */
static struct uuid smc_test_uuid = {
        0x3c321776,
        0x548e,
        0x4978,
        {0xb6, 0x76, 0x84, 0x3c, 0xbf, 0x10, 0x73, 0xe5},
};

static bool equal_uuid(const struct uuid* a, const struct uuid* b) {
    return memcmp(a, b, sizeof(struct uuid)) == 0;
}

static int smc_test_access_policy(uint32_t smc_nr) {
    /*
     * SMC_FC_ECHO_ONE_ARG and SMC_FC64_ECHO_ONE_ARG used to test that we
     * can limit access to smcs.
     */
    if (smc_nr == SMC_FC_ECHO_ONE_ARG || smc_nr == SMC_FC64_ECHO_ONE_ARG)
        return ERR_ACCESS_DENIED;

    /* SMC test has unrestricted access to all other SMCs. */
    return NO_ERROR;
}

static int default_access_policy(uint32_t smc_nr) {
    return ERR_ACCESS_DENIED;
}

static int smc_test_request_check(uint32_t smc_nr,
                                  const struct uuid* uuid,
                                  const struct smc_msg* request) {
    if ((smc_nr == SMC_FC_ECHO_THREE_ARGS ||
         smc_nr == SMC_FC64_ECHO_THREE_ARGS) &&
        request->params[1] != SMC_ACCESS_CONTROL_ALLOW_ARGS) {
        /*
         * SMC_FC64_ECHO_THREE_ARGS is used to test that we can validate the
         * arguments of a smcall.
         */
        if (request->params[1] == SMC_ACCESS_CONTROL_VALIDATE_ARGS) {
            /*
             * If first param is SMC_ACCESS_CONTROL_VALIDATE_ARGS, second param
             * must be a physical address that requesting app prepared for dma.
             */
            paddr_t paddr = request->params[2];
            if (!paddr || !trusty_uuid_dma_is_allowed(uuid, paddr)) {
                return ERR_INVALID_ARGS;
            }
            return NO_ERROR;
        }
        return ERR_INVALID_ARGS;
    }

    /* SMC test is allowed to make any other request. */
    return NO_ERROR;
}

static int default_request_check(uint32_t smc_nr,
                                 const struct uuid* uuid,
                                 const struct smc_msg* request) {
    return ERR_ACCESS_DENIED;
}

void smc_load_access_policy(const struct uuid* uuid,
                            struct smc_access_policy* policy) {
    /* On QEMU builds, only SMC test can have access to SMC service. */
    if (equal_uuid(uuid, &smc_test_uuid)) {
        policy->check_access = smc_test_access_policy;
        policy->check_request = smc_test_request_check;
        return;
    }
    policy->check_access = default_access_policy;
    policy->check_request = default_request_check;
}