[FFmpeg-devel] [PATCH v2 1/2] avformat/url: check double dot is not to parent directory

[Zlomek, Josef]

Hi Steven,

It is better but still not correct. Consider this test:

test("http://server/foo/bar",
"a/b/../c/d/../e../.../..f/g../h../other/url/a.mp3/...");
It should give "
http://server/foo/bar/a/c/e../.../..f/g../h../other/url/a.mp3/...".

I think the best would be to use strtok(p, "/") to split the path into the
components and for each ".." component remove the previous one (if there
are some still).

Best regards,
Josef

On Sat, Jul 25, 2020 at 4:45 AM Steven Liu <lq at chinaffmpeg.org> wrote:

> fix ticket: 8814
> if get ".." in the url, check next byte and lead byte by double dot,
> it there have no '/' and not root node, it is not used go to directory ".."
>
> Signed-off-by: Steven Liu <lq at chinaffmpeg.org>
> ---
>  libavformat/url.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/libavformat/url.c b/libavformat/url.c
> index 20463a6674..35f27fe3ca 100644
> --- a/libavformat/url.c
> +++ b/libavformat/url.c
> @@ -97,6 +97,18 @@ static void trim_double_dot_url(char *buf, const char
> *rel, int size)
>      /* set new current position if the root node is changed */
>      p = root;
>      while (p && (node = strstr(p, ".."))) {
> +        if (strlen(node) > 2 && node[2] != '/') {
> +            node = strstr(node + 1, "..");
> +            if (!node)
> +                break;
> +        }
> +
> +        if (p != node && p[node - p - 1] != '/') {
> +            node = strstr(node + 1, "..");
> +            if (!node)
> +                break;
> +        }
> +
>          av_strlcat(tmp_path, p, node - p + strlen(tmp_path));
>          p = node + 3;
>          sep = strrchr(tmp_path, '/');
> --
> 2.25.0
>
>
>
>
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-- 
Josef Zlomek