[FFmpeg-devel] [PATCH] avformat/dashdec: Fix urls with special characters in manifest (PR #20823)

[Hendi48 via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #20823 opened by Hendi48
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20823
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20823.patch

This fixes a long standing bug where URLs with multiple query parameters broke the DASH manifest parser. libxml2 will decode entities when fetching node content, but when setting it back with `xmlNodeSetContent`, it's the caller's responsibility to ensure special chars like ampersands are encoded.

Fixes trac https://trac.ffmpeg.org/ticket/7395


>From eb58d8deccff900f11e03874e64ed7632d28cd97 Mon Sep 17 00:00:00 2001
From: Hendi <hendi48@freenet.de>
Date: Sun, 2 Nov 2025 23:11:02 +0100
Subject: [PATCH] avformat/dashdec: Fix urls with special characters in
 manifest

This was especially a problem with ampersands, which occur
frequently as part of query parameters.
---
 libavformat/dashdec.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/libavformat/dashdec.c b/libavformat/dashdec.c
index 1f59d3a41c..9b52f24564 100644
--- a/libavformat/dashdec.c
+++ b/libavformat/dashdec.c
@@ -709,6 +709,7 @@ static int resolve_content_path(AVFormatContext *s, const char *url, int *max_ur
     char *path = NULL;
     char *mpdName = NULL;
     xmlNodePtr node = NULL;
+    xmlChar *escaped = NULL;
     char *baseurl = NULL;
     char *root_url = NULL;
     char *text = NULL;
@@ -780,7 +781,9 @@ static int resolve_content_path(AVFormatContext *s, const char *url, int *max_ur
     }
     root_url = (av_strcasecmp(baseurl, "")) ? baseurl : path;
     if (node) {
-        xmlNodeSetContent(node, root_url);
+        escaped = xmlEncodeSpecialChars(NULL, root_url);
+        xmlNodeSetContent(node, escaped);
+        free(escaped);
         updated = 1;
     }
 
@@ -814,8 +817,10 @@ static int resolve_content_path(AVFormatContext *s, const char *url, int *max_ur
                 memset(p + 1, 0, strlen(p));
             }
             av_strlcat(tmp_str, text + start, tmp_max_url_size);
-            xmlNodeSetContent(baseurl_nodes[i], tmp_str);
+            escaped = xmlEncodeSpecialChars(NULL, tmp_str);
+            xmlNodeSetContent(baseurl_nodes[i], escaped);
             updated = 1;
+            xmlFree(escaped);
             xmlFree(text);
         }
     }
-- 
2.49.1

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