Re: [FFmpeg-devel] [PATCH] Percent-encode URL paths in HLS playlists

[Marton Balint <cus@passwd.hu>]

On Fri, 23 May 2025, Timothy Allen via ffmpeg-devel wrote:

> This commit closes trac ticket 10679.

And what if the M3U8 is referencing absolute URLs with scheme? Or is using 
a data URI? Or if it is a local DOS path? What if the URL is already 
percent encoded?

This issue is not trivial to fix, so I really meant it when I wrote that 
its worth checking what heuristics other software is using for this issue.

Thanks,
Marton

>
> Signed-off-by: Timothy Allen <tim@treehouse.org.za>
> ---
> libavformat/hls.c |  9 +++++++++
> libavformat/url.c | 35 +++++++++++++++++++++++++++++++++++
> libavformat/url.h |  9 +++++++++
> 3 files changed, 53 insertions(+)
>
> diff --git a/libavformat/hls.c b/libavformat/hls.c
> index c7b655c83c..49436d8184 100644
> --- a/libavformat/hls.c
> +++ b/libavformat/hls.c
> @@ -1021,6 +1021,15 @@ static int parse_playlist(HLSContext *c, const char *url,
>                     seg->key = NULL;
>                 }
>
> +                ff_percent_encode_url(tmp_str, sizeof(tmp_str), line);
> +                if (!tmp_str[0]) {
> +                    ret = AVERROR_INVALIDDATA;
> +                    if (seg->key)
> +                        av_free(seg->key);
> +                    av_free(seg);
> +                    goto fail;
> +                }
> +                strcpy(line, av_strdup(tmp_str));
>                 ff_make_absolute_url(tmp_str, sizeof(tmp_str), url, line);
>                 if (!tmp_str[0]) {
>                     ret = AVERROR_INVALIDDATA;
> diff --git a/libavformat/url.c b/libavformat/url.c
> index d5dd6a4666..69d68d4248 100644
> --- a/libavformat/url.c
> +++ b/libavformat/url.c
> @@ -324,6 +324,41 @@ int ff_make_absolute_url(char *buf, int size, const char *base,
>     return ff_make_absolute_url2(buf, size, base, rel, HAVE_DOS_PATHS);
> }
>
> +int ff_percent_encode_url(char *buf, int size, const char *url)
> +{
> +    const char *hex = "0123456789abcdef";
> +
> +    av_assert0(url);
> +
> +    int p = 0;
> +    int len = strlen(url);
> +    for (int i = 0; i < len; i++) {
> +        if (i + 1 < len && ':' == url[i] && '/' == url[i+1])
> +            buf[p++] = url[i];
> +        else if (('a' <= url[i] && url[i] <= 'z')
> +          || ('A' <= url[i] && url[i] <= 'Z')
> +          || ('0' <= url[i] && url[i] <= '9')
> +          || '/' == url[i] || '.' == url[i] || '~' == url[i]
> +          || '-' == url[i] || '_' == url[i] || '+' == url[i]
> +          || '?' == url[i] || '=' == url[i] || '&' == url[i]
> +          || '#' == url[i])
> +        {
> +            buf[p++] = url[i];
> +        } else if (' ' == url[i])
> +        {
> +            buf[p++] = '+';
> +        } else
> +        {
> +            buf[p++] = '%';
> +            buf[p++] = hex[url[i] >> 4];
> +            buf[p++] = hex[url[i] & 15];
> +            }
> +    }
> +    buf[p] = '\0';
> +
> +    return 0;
> +}
> +
> AVIODirEntry *ff_alloc_dir_entry(void)
> {
>     AVIODirEntry *entry = av_mallocz(sizeof(AVIODirEntry));
> diff --git a/libavformat/url.h b/libavformat/url.h
> index 0784d77b64..85f94f06ce 100644
> --- a/libavformat/url.h
> +++ b/libavformat/url.h
> @@ -331,6 +331,15 @@ int ff_make_absolute_url2(char *buf, int size, const char *base,
> int ff_make_absolute_url(char *buf, int size, const char *base,
>                          const char *rel);
>
> +/**
> + * Percent-encode a URL, to avoid it being incorrectly parsed.
> + *
> + * @param buf the buffer where output absolute url is written
> + * @param size the size of buf
> + * @param url the url to encode
> + */
> +int ff_percent_encode_url(char *buf, int size, const char *url);
> +
> /**
>  * Allocate directory entry with default values.
>  *
> -- 
> 2.43.0
>
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