avformat/mpjpeg: utilize MIME boundary value to detect start of new frame

This code is disabled by default so not to regress endpoints sending invalid MIME, but can be enabled via AVOption 'strict_mime_boundary'

Signed-off-by: Alex Agranovsky <alex@sighthound.com>

1 files changed, 69 insertions, 3 deletions

diff --git a/libavformat/mpjpegdec.c b/libavformat/mpjpegdec.c
index 9d5700ab6b..b644ee400f 100644
--- a/libavformat/mpjpegdec.c
+++ b/libavformat/mpjpegdec.c
@@ -20,6 +20,7 @@
  */
 
 #include "libavutil/avstring.h"
+#include "libavutil/opt.h"
 
 #include "avformat.h"
 #include "internal.h"
@@ -28,9 +29,11 @@
 
 
 typedef struct MPJPEGDemuxContext {
+    const AVClass *class;
     char       *boundary;
     char       *searchstr;
     int         searchstr_len;
+    int         strict_mime_boundary;
 } MPJPEGDemuxContext;
 
 
@@ -242,6 +245,41 @@ static int parse_multipart_header(AVIOContext *pb,
 }
 
 
+static char* mpjpeg_get_boundary(AVIOContext* pb)
+{
+    uint8_t *mime_type = NULL;
+    uint8_t *start;
+    uint8_t *end;
+    uint8_t *res = NULL;
+    int     len;
+
+    /* get MIME type, and skip to the first parameter */
+    av_opt_get(pb, "mime_type", AV_OPT_SEARCH_CHILDREN, &mime_type);
+    start = mime_type;
+    while (start != NULL && *start != '\0') {
+        start = strchr(start, ';');
+        if (start)
+            start = start+1;
+
+        while (av_isspace(*start))
+            start++;
+
+        if (!av_stristart(start, "boundary=", &start)) {
+            end = strchr(start, ';');
+            if (end)
+                len = end - start - 1;
+            else
+                len = strlen(start);
+            res = av_strndup(start, len);
+            break;
+        }
+    }
+
+    av_freep(&mime_type);
+    return res;
+}
+
+
 static int mpjpeg_read_packet(AVFormatContext *s, AVPacket *pkt)
 {
     int size;
@@ -249,8 +287,17 @@ static int mpjpeg_read_packet(AVFormatContext *s, AVPacket *pkt)
 
     MPJPEGDemuxContext *mpjpeg = s->priv_data;
     if (mpjpeg->boundary == NULL) {
-        mpjpeg->boundary = av_strdup("--");
-        mpjpeg->searchstr = av_strdup("\r\n--");
+        uint8_t* boundary = NULL;
+        if (mpjpeg->strict_mime_boundary) {
+            boundary = mpjpeg_get_boundary(s->pb);
+        }
+        if (boundary != NULL) {
+            mpjpeg->boundary = boundary;
+            mpjpeg->searchstr = av_asprintf( "\r\n%s\r\n", boundary );
+        } else {
+            mpjpeg->boundary = av_strdup("--");
+            mpjpeg->searchstr = av_strdup("\r\n--");
+        }
         if (!mpjpeg->boundary || !mpjpeg->searchstr) {
             av_freep(&mpjpeg->boundary);
             av_freep(&mpjpeg->searchstr);
@@ -309,6 +356,22 @@ static int mpjpeg_read_packet(AVFormatContext *s, AVPacket *pkt)
     return ret;
 }
 
+#define OFFSET(x) offsetof(MPJPEGDemuxContext, x)
+
+#define DEC AV_OPT_FLAG_DECODING_PARAM
+const AVOption mpjpeg_options[] = {
+    { "strict_mime_boundary",  "require MIME boundaries match", OFFSET(strict_mime_boundary), AV_OPT_TYPE_INT, {.i64 = 0}, 0, 1, DEC },
+    { NULL }
+};
+
+
+static const AVClass mpjpeg_demuxer_class = {
+    .class_name     = "MPJPEG demuxer",
+    .item_name      = av_default_item_name,
+    .option         = mpjpeg_options,
+    .version        = LIBAVUTIL_VERSION_INT,
+};
+
 AVInputFormat ff_mpjpeg_demuxer = {
     .name              = "mpjpeg",
     .long_name         = NULL_IF_CONFIG_SMALL("MIME multipart JPEG"),
@@ -318,5 +381,8 @@ AVInputFormat ff_mpjpeg_demuxer = {
     .read_probe        = mpjpeg_read_probe,
     .read_header       = mpjpeg_read_header,
     .read_packet       = mpjpeg_read_packet,
-    .read_close        = mpjpeg_read_close
+    .read_close        = mpjpeg_read_close,
+    .priv_class        = &mpjpeg_demuxer_class
 };
+
+