Re: [FFmpeg-devel] [PATCH v3 2/2] libavformat/vapoursynth: Update to API version 4, load library at runtime

[Stefan Oltmanns via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

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Am 28.07.24 um 15:15 schrieb Ramiro Polla:
>> +    void *vslibrary = NULL;
>> +#ifdef _WIN32
>> +    const HKEY hkeys[] = {HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE};
>> +    LONG r;
>> +    WCHAR vss_path[512];
>> +    DWORD buf_size = sizeof(vss_path) - 2;
>> +    char *vss_path_utf8;
>> +    int i;
>> +
>> +    for (i = 0; i < sizeof(hkeys); i++) {
>
> FF_ARRAY_ELEMS(hkeys)

fixed

>
>> +        if ((r = RegGetValueW(hkeys[i], L"SOFTWARE\\VapourSynth",
>> +                      L"VSScriptDLL", RRF_RT_REG_SZ, NULL,
>> +                      &vss_path, &buf_size)) == ERROR_SUCCESS)
>> +            break;
>> +    }
>> +    if (r == ERROR_SUCCESS && wchartoutf8(vss_path, &vss_path_utf8)
>> == 0) {
>> +        vslibrary = dlopen(vss_path_utf8, RTLD_NOW | RTLD_GLOBAL);
>
> I think calling win32_dlopen() with a full path will be problematic for
> systems without KB2533623. win32_dlopen() might need to be fixed in a
> separate patch.
>

Yes, win32_dlopen would need to check if a full path is already given
and if yes skip all the stuff to determine it's own and system32 path,
but instead just use the given parameter directly. To check if it's a
full path it should be enough to check if it either starts with "\??\"
(NT-style path) or if the second character is ":" (win32 style path).

But is this really is needed for an operating system that reached
support end over 4 years ago and does not have a security patch applied
released over 13 years ago?
I don't know what ffmpeg's exact policy is in this case, just asking.

Best regards
Stefan

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From dc396711d050c112b2ef6c37fdb67c4ec59c16a1 Mon Sep 17 00:00:00 2001
From: Stefan Oltmanns <stefan-oltmanns@gmx.net>
Date: Mon, 29 Jul 2024 05:12:31 +0200
Subject: [PATCH 2/2] avformat/vapoursynth: load library at runtime

Signed-off-by: Stefan Oltmanns <stefan-oltmanns@gmx.net>
---
 configure                 |  2 +-
 libavformat/vapoursynth.c | 65 +++++++++++++++++++++++++++++++++++++--
 2 files changed, 64 insertions(+), 3 deletions(-)

diff --git a/configure b/configure
index c50b5ad4b4..1b6670505a 100755
--- a/configure
+++ b/configure
@@ -7085,7 +7085,7 @@ enabled rkmpp             && { require_pkg_config rkmpp rockchip_mpp  rockchip/r
                                { enabled libdrm ||
                                  die "ERROR: rkmpp requires --enable-libdrm"; }
                              }
-enabled vapoursynth       && require_pkg_config vapoursynth "vapoursynth-script >= 55" VSScript4.h getVSScriptAPI
+enabled vapoursynth       && require_headers "vapoursynth/VSScript4.h vapoursynth/VapourSynth4.h"
 
 
 if enabled gcrypt; then
diff --git a/libavformat/vapoursynth.c b/libavformat/vapoursynth.c
index 26c9986138..0fa5affa63 100644
--- a/libavformat/vapoursynth.c
+++ b/libavformat/vapoursynth.c
@@ -25,7 +25,7 @@
 
 #include <limits.h>
 
-#include <VSScript4.h>
+#include <vapoursynth/VSScript4.h>
 
 #include "libavutil/avassert.h"
 #include "libavutil/avstring.h"
@@ -39,11 +39,26 @@
 #include "demux.h"
 #include "internal.h"
 
+/* Platform-specific directives. */
+#ifdef _WIN32
+  #include <windows.h>
+  #include "compat/w32dlfcn.h"
+  #include "libavutil/wchar_filename.h"
+  #undef EXTERN_C
+  #define VSSCRIPT_LIB "VSScript.dll"
+#else
+  #include <dlfcn.h>
+  #define VSSCRIPT_NAME "libvapoursynth-script"
+  #define VSSCRIPT_LIB VSSCRIPT_NAME SLIBSUF
+#endif
+
 struct VSState {
     const VSSCRIPTAPI *vssapi;
     VSScript *vss;
 };
 
+typedef const VSSCRIPTAPI *(*VSScriptGetAPIFunc)(int version);
+
 typedef struct VSContext {
     const AVClass *class;
 
@@ -51,6 +66,7 @@ typedef struct VSContext {
 
     const VSSCRIPTAPI *vssapi;
     const VSAPI *vsapi;
+    void *vslibrary;
 
     VSNode *outnode;
     int is_cfr;
@@ -70,6 +86,40 @@ static const AVOption options[] = {
     {NULL}
 };
 
+static av_cold void* vs_load_library(VSScriptGetAPIFunc *get_vssapi)
+{
+    void *vslibrary = NULL;
+#ifdef _WIN32
+    const HKEY hkeys[] = {HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE};
+    LONG r;
+    WCHAR vss_path[512];
+    DWORD buf_size = sizeof(vss_path) - 2;
+    char *vss_path_utf8;
+    int i;
+
+    for (i = 0; i < FF_ARRAY_ELEMS(hkeys); i++) {
+        if ((r = RegGetValueW(hkeys[i], L"SOFTWARE\\VapourSynth",
+                      L"VSScriptDLL", RRF_RT_REG_SZ, NULL,
+                      &vss_path, &buf_size)) == ERROR_SUCCESS)
+            break;
+    }
+    if (r == ERROR_SUCCESS && wchartoutf8(vss_path, &vss_path_utf8) == 0) {
+        vslibrary = dlopen(vss_path_utf8, RTLD_NOW | RTLD_GLOBAL);
+        av_free(vss_path_utf8);
+    }
+    else
+#endif
+    vslibrary = dlopen(VSSCRIPT_LIB, RTLD_NOW | RTLD_GLOBAL);
+
+    if (vslibrary != NULL) {
+        if (!(*get_vssapi = (VSScriptGetAPIFunc)dlsym(vslibrary, "getVSScriptAPI"))) {
+            dlclose(vslibrary);
+            return NULL;
+        }
+    }
+    return vslibrary;
+}
+
 static void free_vss_state(void *opaque, uint8_t *data)
 {
     struct VSState *vss = opaque;
@@ -91,6 +141,9 @@ static av_cold int read_close_vs(AVFormatContext *s)
     vs->vsapi = NULL;
     vs->outnode = NULL;
 
+    if (vs->vslibrary)
+        dlclose(vs->vslibrary);
+
     return 0;
 }
 
@@ -170,6 +223,7 @@ static av_cold int read_header_vs(AVFormatContext *s)
     AVStream *st;
     AVIOContext *pb = s->pb;
     VSContext *vs = s->priv_data;
+    VSScriptGetAPIFunc get_vssapi;
     int64_t sz = avio_size(pb);
     char *buf = NULL;
     char dummy;
@@ -178,7 +232,14 @@ static av_cold int read_header_vs(AVFormatContext *s)
     struct VSState *vss_state;
     int err = 0;
 
-    if (!(vs->vssapi = getVSScriptAPI(VSSCRIPT_API_VERSION))) {
+    if (!(vs->vslibrary = vs_load_library(&get_vssapi))) {
+        av_log(s, AV_LOG_ERROR, "Could not open " VSSCRIPT_LIB ". "
+                                "Check VapourSynth installation.\n");
+        err = AVERROR_EXTERNAL;
+        goto done;
+    }
+
+    if (!(vs->vssapi = get_vssapi(VSSCRIPT_API_VERSION))) {
         av_log(s, AV_LOG_ERROR, "Failed to initialize VSScript (possibly PYTHONPATH not set).\n");
         err = AVERROR_EXTERNAL;
         goto done;
-- 
2.34.1


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