On Thu, Oct 26, 2023 at 11:19:18PM +0000, Justin Stitt wrote:
> strncpy() is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
>
> `extra` is clearly supposed to be NUL-terminated which is evident by the
> manual NUL-byte assignment as well as its immediate usage with strlen().
>
> Moreover, let's NUL-pad since there is deliberate effort (48 instances)
> made elsewhere to zero-out buffers in these getters and setters:
> 6050 | memset(local->config.nodeName, 0, sizeof(local->config.nodeName));
> 6130 | memset(local->config.rates, 0, 8);
> 6139 | memset(local->config.rates, 0, 8);
> 6414 | memset(key.key, 0, MAX_KEY_SIZE);
> 6497 | memset(extra, 0, 16);
> (to be clear, strncpy also NUL-padded -- we are matching that behavior)
>
> Considering the above, a suitable replacement is `strscpy_pad` due to
> the fact that it guarantees both NUL-termination and NUL-padding on the
> destination buffer.
>
> We can also replace the hard-coded size of "16" to IW_ESSID_MAX_SIZE
> because this function is a wext handler.
>
> In wext-core.c we have:
> static const struct iw_ioctl_description standard_ioctl[] = {
> ...
> [IW_IOCTL_IDX(SIOCGIWNICKN)] = {
> .header_type = IW_HEADER_TYPE_POINT,
> .token_size = 1,
> .max_tokens = IW_ESSID_MAX_SIZE,
> },
>
> So the buffer size is (strangely) IW_ESSID_MAX_SIZE
>
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@xxxxxxxxxxxxxxx
> Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>
Looks good; thanks!
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
--
Kees Cook
