From a172c880cb51f882a5dc999437e8b3a4f87630cc Mon Sep 17 00:00:00 2001 From: Roman Arutyunyan Date: Sat, 21 Feb 2026 12:04:36 +0400 Subject: [PATCH] Mp4: avoid zero size buffers in output. Previously, data validation checks did not cover the cases when the output contained empty buffers. Such buffers are considered illegal and produce "zero size buf in output" alerts. The change rejects the mp4 files which produce such alerts. Also, the change fixes possible buffer overread and overwrite that could happen while processing empty stco and co64 atoms, as reported by Pavel Kohout (Aisle Research) and Tim Becker. --- src/http/modules/ngx_http_mp4_module.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/src/http/modules/ngx_http_mp4_module.c b/src/http/modules/ngx_http_mp4_module.c index 445fab1cd..173d8ad54 100644 --- a/src/http/modules/ngx_http_mp4_module.c +++ b/src/http/modules/ngx_http_mp4_module.c @@ -901,8 +901,11 @@ ngx_http_mp4_process(ngx_http_mp4_file_t *mp4) } } - if (end_offset < start_offset) { - end_offset = start_offset; + if (end_offset <= start_offset) { + ngx_log_error(NGX_LOG_ERR, mp4->file.log, 0, + "no data between start time and end time in \"%s\"", + mp4->file.name.data); + return NGX_ERROR; } mp4->moov_size += 8; @@ -913,7 +916,7 @@ ngx_http_mp4_process(ngx_http_mp4_file_t *mp4) *prev = &mp4->mdat_atom; - if (start_offset > mp4->mdat_data.buf->file_last) { + if (start_offset >= mp4->mdat_data.buf->file_last) { ngx_log_error(NGX_LOG_ERR, mp4->file.log, 0, "start time is out mp4 mdat atom in \"%s\"", mp4->file.name.data); @@ -3444,7 +3447,7 @@ ngx_http_mp4_update_stsz_atom(ngx_http_mp4_file_t *mp4, if (data) { entries = trak->sample_sizes_entries; - if (trak->start_sample > entries) { + if (trak->start_sample >= entries) { ngx_log_error(NGX_LOG_ERR, mp4->file.log, 0, "start time is out mp4 stsz samples in \"%s\"", mp4->file.name.data); @@ -3619,7 +3622,7 @@ ngx_http_mp4_update_stco_atom(ngx_http_mp4_file_t *mp4, return NGX_ERROR; } - if (trak->start_chunk > trak->chunks) { + if (trak->start_chunk >= trak->chunks) { ngx_log_error(NGX_LOG_ERR, mp4->file.log, 0, "start time is out mp4 stco chunks in \"%s\"", mp4->file.name.data); @@ -3834,7 +3837,7 @@ ngx_http_mp4_update_co64_atom(ngx_http_mp4_file_t *mp4, return NGX_ERROR; } - if (trak->start_chunk > trak->chunks) { + if (trak->start_chunk >= trak->chunks) { ngx_log_error(NGX_LOG_ERR, mp4->file.log, 0, "start time is out mp4 co64 chunks in \"%s\"", mp4->file.name.data); -- 2.47.3