Multiple vulnerabilities in RT-Thread ymodem utility

Hi,

I would like to report other potential vulnerabilities in the current version of RT-Thread. Please let me know if you plan to ask for a CVE ID in case the vulnerabilities are confirmed. I'm available if you need further clarifications.

Multiple potential vulnerabilities in RT-Thread ymodem utility

Summary

I spotted some potential vulnerabilities at the following locations in the RT-Thread ymodem utility source code:
https://github.com/RT-Thread/rt-thread/blob/master/components/utilities/ymodem/ry_sy.c#L149
https://github.com/RT-Thread/rt-thread/blob/master/components/utilities/ymodem/ry_sy.c#L205
https://github.com/RT-Thread/rt-thread/blob/master/components/utilities/ymodem/ry_sy.c#L225

Details

Unbounded rt_sprintf() in the _rym_send_begin() function could lead to a buffer overflow at the marked line:

static enum rym_code _rym_send_begin(
    struct rym_ctx *ctx,
    rt_uint8_t *buf,
    rt_size_t len)
{
    struct custom_ctx *cctx = (struct custom_ctx *)ctx;
    struct stat file_buf;
    char insert_0 = '\0';
    rt_err_t err;

    cctx->fd = open(cctx->fpath, O_RDONLY);
    if (cctx->fd < 0)
    {
        err = rt_get_errno();
        rt_kprintf("error open file: %d\n", err);
        return RYM_ERR_FILE;
    }
    rt_memset(buf, 0, len);
    err = stat(cctx->fpath, &file_buf);
    if (err != RT_EOK)
    {
        rt_kprintf("error open file.\n");
        return RYM_ERR_FILE;
    }

    const char *fdst = _get_path_lastname(cctx->fpath);
    if(fdst != cctx->fpath)
    {
        fdst = dfs_normalize_path(RT_NULL, fdst);
        if (fdst == RT_NULL)
        {
            return RYM_ERR_FILE;
        }
    }

    rt_sprintf((char *)buf, "%s%c%d", fdst, insert_0, file_buf.st_size); /* VULN: if we can make fdst large enough, there's no bound checking */

    return RYM_CODE_SOH;
}

Lack of NUL-termination in the rym_download_file() function at the marked line:

static rt_err_t rym_download_file(rt_device_t idev,const char *file_path)
{
    rt_err_t res;
    struct custom_ctx *ctx = rt_calloc(1, sizeof(*ctx));

    if (!ctx)
    {
        rt_kprintf("rt_malloc failed\n");
        return -RT_ENOMEM;
    }
    ctx->fd = -1;
    rt_strncpy(ctx->fpath, file_path, DFS_PATH_MAX); /* VULN: unterm if file_path is at least DFS_PATH_MAX bytes (comes from argv); it might cause infoleak or memory corruption */
    RT_ASSERT(idev);
    res = rym_recv_on_device(&ctx->parent, idev, RT_DEVICE_OFLAG_RDWR | RT_DEVICE_FLAG_INT_RX,
                             _rym_recv_begin, _rym_recv_data, _rym_recv_end, 1000);
    rt_free(ctx);

    return res;
}

Lack of NUL-termination in the rym_upload_file() function at the marked line:

static rt_err_t rym_upload_file(rt_device_t idev, const char *file_path)
{
    rt_err_t res = 0;

    struct custom_ctx *ctx = rt_calloc(1, sizeof(*ctx));
    if (!ctx)
    {
        rt_kprintf("rt_malloc failed\n");
        return -RT_ENOMEM;
    }
    ctx->fd = -1;
    rt_strncpy(ctx->fpath, file_path, DFS_PATH_MAX); /* VULN: unterm if file_path is at least DFS_PATH_MAX bytes (comes from argv); it might cause infoleak or memory corruption */
    RT_ASSERT(idev);
    res = rym_send_on_device(&ctx->parent, idev,
                             RT_DEVICE_OFLAG_RDWR | RT_DEVICE_FLAG_INT_RX,
                             _rym_send_begin, _rym_send_data, _rym_send_end, 1000);
    rt_free(ctx);

    return res;
}

Impact

If the unchecked input above is confirmed to be attacker-controlled and crossing a security boundary, the impact of the reported vulnerabilities could range from information leakage to denial of service, or even arbitrary code execution.

Start with components/utilities/ymodem/ry_sy.c at lines 149, 205, and 225, then trace the callers of _rym_send_begin(), rym_download_file(), and rym_upload_file(). Verify whether the reported inputs can reach these paths and reproduce the claimed overflow or unterminated-string behavior. Done means the three reported cases are confirmed or disproved and validated against the relevant ymodem flows.