编写自己的CA和TA与逆向

参考内容《手机安全和可信应用开发》
https://note.youdao.com/s/MTlG4c1w

介绍

TA的全称是Trust Application，即可信任应用程序。 CA的全称是Client Applicant，即客户端应用程序。 TA运行在OP-TEE的用户空间， CA运行在REE侧。 CA执行时代入特定的UUID和命令ID参数就能实现请求特定TA执行特定操作的需求，并将执行结果返回给CA。通过CA对TA的调用可实现在REE侧对安全设备和安全资源的操作。普通用户无法知道TA的具体实现，例如操作使用了什么算法、操作了哪些资源、获取了哪些数据等，这也就确保了相关资源和数据的安全。

编写自己的第一个TA程序

在这里插入图片描述
Android.mk是安卓编译,
host/main.c==>CA:共五步：1.初始化上下文；2.打开会话；3.发送命令和参数；4.关闭会话；5.结束上下文。
hello_world_ta.c==>TA，分别对应CA五步的入口操作

CA


int main(void)
{
//1.--------------------------------------------------------------------------------------------    
    res = TEEC_InitializeContext(NULL, &ctx);
    if (res != TEEC_SUCCESS)
        errx(1, "TEEC_InitializeContext failed with code 0x%x", res);
//2.--------------------------------------------------------------------------------------------
    res = TEEC_OpenSession(&ctx, &sess, &uuid,
                   TEEC_LOGIN_PUBLIC, NULL, NULL, &err_origin);
    if (res != TEEC_SUCCESS)
        errx(1, "TEEC_Opensession failed with code 0x%x origin 0x%x",
            res, err_origin);
//3.--------------------------------------------------------------------------------------------    
    memset(&op, 0, sizeof(op));

    op.paramTypes = TEEC_PARAM_TYPES(TEEC_VALUE_INOUT, TEEC_NONE,
                     TEEC_NONE, TEEC_NONE);
    op.params[0].value.a = 42;

    printf("Invoking TA to increment %d\n", op.params[0].value.a);
    res = TEEC_InvokeCommand(&sess, TA_HELLO_WORLD_CMD_INC_VALUE, &op,
                 &err_origin);command 
    if (res != TEEC_SUCCESS)
        errx(1, "TEEC_InvokeCommand failed with code 0x%x origin 0x%x",
            res, err_origin);
    printf("TA incremented value to %d\n", op.params[0].value.a);
//4.---------------------------------------------------------------------------------------------
    TEEC_CloseSession(&sess);
//5.--------------------------------------------------------------------------------------------
    TEEC_FinalizeContext(&ctx);

    return 0;
}

TA


TEE_Result TA_CreateEntryPoint(void)
{
    DMSG("has been called");

    return TEE_SUCCESS;
}


void TA_DestroyEntryPoint(void)
{
    DMSG("has been called");
}


TEE_Result TA_OpenSessionEntryPoint(uint32_t param_types,
        TEE_Param __maybe_unused params[4],
        void __maybe_unused **sess_ctx)
{
    uint32_t exp_param_types = TEE_PARAM_TYPES(TEE_PARAM_TYPE_NONE,
                           TEE_PARAM_TYPE_NONE,
                           TEE_PARAM_TYPE_NONE,
                           TEE_PARAM_TYPE_NONE);

    DMSG("has been called");

    if (param_types != exp_param_types)
        return TEE_ERROR_BAD_PARAMETERS;

    (void)&params;
    (void)&sess_ctx;


    IMSG("Hello 0xCC!\n");


    return TEE_SUCCESS;
}


void TA_CloseSessionEntryPoint(void __maybe_unused *sess_ctx)
{
    (void)&sess_ctx; /* Unused parameter */
    IMSG("Goodbye! 0xCC \n");
}

static TEE_Result inc_value(uint32_t param_types,
    TEE_Param params[4])
{
    uint32_t exp_param_types = TEE_PARAM_TYPES(TEE_PARAM_TYPE_VALUE_INOUT,
                           TEE_PARAM_TYPE_NONE,
                           TEE_PARAM_TYPE_NONE,
                           TEE_PARAM_TYPE_NONE);

    DMSG("has been called");

    if (param_types != exp_param_types)
        return TEE_ERROR_BAD_PARAMETERS;

    IMSG("Got value: %u from NW", params[0].value.a);
    params[0].value.a += 10;  ///42+10 = 52
    IMSG("Increase value to: %u", params[0].value.a);

    return TEE_SUCCESS;
}

static TEE_Result dec_value(uint32_t param_types,
    TEE_Param params[4])
{
    uint32_t exp_param_types = TEE_PARAM_TYPES(TEE_PARAM_TYPE_VALUE_INOUT,
                           TEE_PARAM_TYPE_NONE,
                           TEE_PARAM_TYPE_NONE,
                           TEE_PARAM_TYPE_NONE);

    DMSG("has been called");

    if (param_types != exp_param_types)
        return TEE_ERROR_BAD_PARAMETERS;

    IMSG("Got value: %u from NW", params[0].value.a);
    params[0].value.a--;
    IMSG("Decrease value to: %u", params[0].value.a);

    return TEE_SUCCESS;
}

TEE_Result TA_InvokeCommandEntryPoint(void __maybe_unused *sess_ctx,
            uint32_t cmd_id,
            uint32_t param_types, TEE_Param params[4])
{
    (void)&sess_ctx; /* Unused parameter */

    switch (cmd_id) {
    case TA_HELLO_0xCC_CMD_INC_VALUE:
        return inc_value(param_types, params);
    case TA_HELLO_0xCC_CMD_DEC_VALUE:
        return dec_value(param_types, params);
    default:
        return TEE_ERROR_BAD_PARAMETERS;
    }
}

TA属性说明


#ifndef USER_TA_HEADER_DEFINES_H
#define USER_TA_HEADER_DEFINES_H

/* To get the TA UUID definition */
#include <hello_0xcc_ta.h>

#define TA_UUID                TA_HELLO_0xCC_UUID
TA识别号
/*
 * TA properties: multi-instance TA, no specific attribute
 * TA_FLAG_EXEC_DDR is meaningless but mandated.
 */
#define TA_FLAGS            TA_FLAG_EXEC_DDR
表示TA是否支持多个会话实例
/* Provisioned stack size */
#define TA_STACK_SIZE            (2 * 1024)
TA运行时栈大小
/* Provisioned heap size for TEE_Malloc() and friends */
#define TA_DATA_SIZE            (32 * 1024)
TA运行时堆空间大小 TEE_Malloc就是从这个空间中分配
/* The gpd.ta.version property */
#define TA_VERSION    "1.0"
版本信息
/* The gpd.ta.description property */
#define TA_DESCRIPTION    "Example of OP-TEE Hello 0xCC Trusted Application"
TA的描述字段
/* Extra properties */
#define TA_CURRENT_TA_EXT_PROPERTIES \
    { "org.linaro.optee.examples.hello_world.property1", \
    USER_TA_PROP_TYPE_STRING, \
        "Some string" }, \
    { "org.linaro.optee.examples.hello_world.property2", \
    USER_TA_PROP_TYPE_U32, &(const uint32_t){ 0x0010 } }
通过宏定义描述gp.ta.description和gp.ta.version
#endif /* USER_TA_HEADER_DEFINES_H */