[FFmpeg-devel] [PATCH v1] fftools/ffplay: Resolve input file path before processing

[Appaji Chintimi]

Can you elaborate a bit more why this requires more changes? My
understanding is, to check for different cases and handle them differently:

1. "-" gets replaced with "fd:", and it's passed directly to
"input_filename" without resolving.
2. if the path contains "://", that too gets passed on without resolving it
further (handles http://, https://, ftp:// etc..)
3. Only after these two checks, resolve the "filename" and pass on to
"input_filename".

On Wed, 14 May 2025 at 23:40, Marton Balint <cus at passwd.hu> wrote:

>
>
> On Wed, 14 May 2025, Nicolas George wrote:
>
> > Appaji (HE12025-05-14):
> >> Fixes ticket: https://trac.ffmpeg.org/ticket/11574
> >>
> >> Signed-off-by: Appaji <appaji12368 at gmail.com>
> >> ---
> >>  fftools/ffplay.c | 13 +++++++++++--
> >>  1 file changed, 11 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/fftools/ffplay.c b/fftools/ffplay.c
> >> index 2a572fc3aa..42f0584b55 100644
> >> --- a/fftools/ffplay.c
> >> +++ b/fftools/ffplay.c
> >> @@ -27,6 +27,7 @@
> >>  #include "config_components.h"
> >>  #include <math.h>
> >>  #include <limits.h>
> >> +#include <stdlib.h>
> >>  #include <signal.h>
> >>  #include <stdint.h>
> >>
> >> @@ -3623,9 +3624,17 @@ static int opt_input_file(void *optctx, const
> char *filename)
> >>                  filename, input_filename);
> >>          return AVERROR(EINVAL);
> >>      }
> >> -    if (!strcmp(filename, "-"))
> >> +
> >> +    char resolved_path[PATH_MAX];
> >> +
> >> +    if (!realpath(filename, resolved_path)) {
> >> +        av_log(NULL, AV_LOG_FATAL, "Failed to resolve path for '%s':
> %s\n", filename, strerror(errno));
> >> +        return AVERROR(errno);
> >> +    }
> >> +
> >
> > Hi. Thanks for the patch. Did you test it with non-filenames arguments,
> > for example http://…?
> >
> >> +    if (!strcmp(resolved_path, "-"))
> >>          filename = "fd:";
> >
> > This should happen before resolution.
> >
> >> -    input_filename = av_strdup(filename);
> >> +    input_filename = av_strdup(resolved_path);
> >>      if (!input_filename)
> >>          return AVERROR(ENOMEM);
> >>
> >
> > On the whole, I think you are going at it wrong: you are only fixing
> > this for ffplay, not for ffprobe, ffmpeg and other applications built on
> > the libraries, and resolving the path can have side effects, for example
> > if you do not have permission on a parent of the current working
> > directory.
> >
> > IMO, the correct way would be to add a stat() early in the opening of
> > the file and test the device number. But that requires changing quite a
> > lot of things.
>
> Agreed. You should improve the probing function to fix the ticket, you can
> do a stat in v4l2_read_probe() in libavdevice/v4l2.c, check if it is a
> char device and try a V4L2 IOCTL on it to make sure it is a V4L2 device.
>
> Regards,
> Marton
>
> >
> > Regards,
> >
> > --
> >  Nicolas George
> > _______________________________________________
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> > ffmpeg-devel at ffmpeg.org
> > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
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