Re: [PATCH 2/2] url: do not allow %00 to represent NULL in URLs

["René Scharfe" <l.s.r@web.de>]

Am 03.06.19 um 22:45 schrieb Matthew DeVore:
> There is no reason to allow %00 to terminate a string, so do not allow it.
> Otherwise, we end up returning arbitrary content in the string (that which is
> after the %00) which is effectively hidden from callers and can escape sanity
> checks and validation, and possible be used in tandem with a security
> vulnerability to introduce a payload.

It's a bit hard to see with the (extended, but still) limited context,
but url_decode_internal() effectively returns a NUL-terminated string,
even though it does use a strbuf parameter named "out" for temporary
storage.  So callers really have no use for decoded NULs, and this
change thus makes sense to me.

>
> Signed-off-by: Matthew DeVore <matvore@google.com>
> ---
>  url.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/url.c b/url.c
> index c0bb4e23c3..cf791cb139 100644
> --- a/url.c
> +++ b/url.c
> @@ -41,21 +41,21 @@ static char *url_decode_internal(const char **query, int len,
>  		if (!c)
>  			break;
>  		if (stop_at && strchr(stop_at, c)) {
>  			q++;
>  			len--;
>  			break;
>  		}
>
>  		if (c == '%' && len >= 3) {
>  			int val = hex2chr(q + 1);
> -			if (0 <= val) {
> +			if (0 < val) {
>  				strbuf_addch(out, val);
>  				q += 3;
>  				len -= 3;
>  				continue;
>  			}
>  		}
>
>  		if (decode_plus && c == '+')
>  			strbuf_addch(out, ' ');
>  		else
>