[FFmpeg-devel] [PATCH] avformat/hlsenc: hold old key info when append list

[Steven Liu]

2017-05-03 9:49 GMT+08:00 Aaron Levinson <alevinsn at aracnet.com>:

> On 4/27/2017 7:21 PM, Steven Liu wrote:
>
>> 2017-04-26 7:30 GMT+08:00 Steven Liu <lq at chinaffmpeg.org>:
>>
>> fix ticket id: #6353
>>>
>>> Signed-off-by: Steven Liu <lq at chinaffmpeg.org>
>>> ---
>>>  libavformat/hlsenc.c | 24 ++++++++++++++++++++++++
>>>  1 file changed, 24 insertions(+)
>>>
>>> diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
>>> index 27c8e3355d..3ec0f330fb 100644
>>> --- a/libavformat/hlsenc.c
>>> +++ b/libavformat/hlsenc.c
>>> @@ -810,6 +810,7 @@ static int parse_playlist(AVFormatContext *s, const
>>> char *url)
>>>      int64_t new_start_pos;
>>>      char line[1024];
>>>      const char *ptr;
>>> +    const char *end;
>>>
>>>      if ((ret = ffio_open_whitelist(&in, url, AVIO_FLAG_READ,
>>>                                     &s->interrupt_callback, NULL,
>>> @@ -842,6 +843,29 @@ static int parse_playlist(AVFormatContext *s, const
>>> char *url)
>>>          } else if (av_strstart(line, "#EXTINF:", &ptr)) {
>>>              is_segment = 1;
>>>              hls->duration = atof(ptr);
>>> +        } else if (av_stristart(line, "#EXT-X-KEY:", &ptr)) {
>>> +            ptr = av_stristr(line, "URI=\"");
>>> +            if (ptr) {
>>> +                ptr += strlen("URI=\"");
>>> +                end = av_stristr(ptr, ",");
>>> +                if (end) {
>>> +                    av_strlcpy(hls->key_uri, ptr, end - ptr);
>>> +                } else {
>>> +                    av_strlcpy(hls->key_uri, ptr, sizeof(hls->key_uri));
>>>
>>
> I know that this patch has already been applied (although it didn't get
> any reviews on the ML), but I think that there are some issues with it.
> First, it seems that both av_strlcpy() cases above will copy the
> terminating '\"' character into hls->key_uri.  Perhaps that won't cause an
> issue in practice, but it is likely not the intended result.  Second, with
> both av_strlcpy() calls that use a length of end - ptr, this could in
> theory result in a buffer overrun depending on how long the URI is, since
> the destination buffers have a fixed size.  This issue is prevented in the
> second call to av_strlcpy(), since it uses sizeof(hls->key_uri), but it is
> a potential issue with the first calls (note that this comment applies to
> the IV=0x code below).  If you want to use av_strlcpy(), either make sure
> that end - ptr is less than or equal to sizeof(hls->key_uri) or do
> something like *end = 0 first and then use av_strlcpy(hls->key_uri, ptr,
> sizeof(hls->key_uri)).
>
> In addition, based on the EXT-X-KEY example at
> https://developer.apple.com/library/content/technotes/tn2288/_index.html
> , it would appear that an EXT-X-KEY declaration may span multiple lines.
> Your solution will not work properly in this case.
>
Hi Aaron,
     I think the libavformat/hls.c maybe have the same problem, because
both of hlsenc and hls use  read_chomp_line to read one line,
     that need check the '\' tail a line, and read the next line into a
buffer, that maybe better, is that right?

>
> Aaron Levinson
>
> +                }
>>> +            }
>>> +
>>> +            ptr = av_stristr(line, "IV=0x");
>>> +            if (ptr) {
>>> +                ptr += strlen("IV=0x");
>>> +                end = av_stristr(ptr, ",");
>>> +                if (end) {
>>> +                    av_strlcpy(hls->iv_string, ptr, end - ptr);
>>> +                } else {
>>> +                    av_strlcpy(hls->iv_string, ptr,
>>> sizeof(hls->iv_string));
>>> +                }
>>> +            }
>>> +
>>>          } else if (av_strstart(line, "#", NULL)) {
>>>              continue;
>>>          } else if (line[0]) {
>>> --
>>> 2.11.0 (Apple Git-81)
>>>
>>>
>>> Applied!
>>
>>
>> Thanks
>>
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