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harden ffmpeg snapshot command formatting

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This commit is contained in:
YuLi
2026-07-24 16:10:46 -07:00
parent 36bad5ccf2
commit 03cb8e5b72
1 changed files with 36 additions and 29 deletions
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65
server/FFmpegSource.cpp
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@@ -449,6 +449,36 @@ static bool makeSnapAsync(const string &play_url, const string &save_path, float
#endif
static bool formatSnapCommand(const string &snap_template, const string &ffmpeg_bin, const string &play_url,
const string &save_path, string &command) {
if (!start_with(snap_template, "%s")) {
return false;
}
const string *values[] = { &ffmpeg_bin, &play_url, &save_path };
size_t placeholder_count = 0;
command.clear();
command.reserve(snap_template.size() + ffmpeg_bin.size() + play_url.size() + save_path.size());
for (size_t i = 0; i < snap_template.size(); ++i) {
if (snap_template[i] != '%') {
command.push_back(snap_template[i]);
continue;
}
if (++i >= snap_template.size()) {
return false;
}
if (snap_template[i] == '%') {
command.push_back('%');
continue;
}
if (snap_template[i] != 's' || placeholder_count >= 3) {
return false;
}
command.append(*values[placeholder_count++]);
}
return placeholder_count == 3;
}
void FFmpegSnap::makeSnap(bool async, const string &play_url, const string &save_path, float timeout_sec, const onSnap &cb) {
#if defined(ENABLE_FFMPEG)
if (async) {
@@ -461,35 +491,16 @@ void FFmpegSnap::makeSnap(bool async, const string &play_url, const string &save
GET_CONFIG(string, ffmpeg_bin, FFmpeg::kBin);
GET_CONFIG(string, ffmpeg_snap, FFmpeg::kSnap);
GET_CONFIG(string, ffmpeg_log, FFmpeg::kLog);
// The template is passed to snprintf and the resulting command is executed.
// Only accept the documented three string placeholders, with the executable
// as the first argument. This also rejects dangerous format specifiers such
// as %n and prevents a configured template from selecting another program.
size_t placeholder_count = 0;
bool valid_template = start_with(ffmpeg_snap, "%s");
for (size_t i = 0; valid_template && i < ffmpeg_snap.size(); ++i) {
if (ffmpeg_snap[i] != '%') {
continue;
}
if (++i >= ffmpeg_snap.size()) {
valid_template = false;
break;
}
if (ffmpeg_snap[i] == '%') {
continue;
}
if (ffmpeg_snap[i] != 's') {
valid_template = false;
break;
}
++placeholder_count;
}
if (!valid_template || placeholder_count != 3) {
string cmd;
if (!formatSnapCommand(ffmpeg_snap, File::absolutePath("", ffmpeg_bin), play_url, save_path, cmd)) {
cb(false, "invalid ffmpeg snap template: expected exactly three '%s' placeholders and no other format specifiers");
return;
}
// Capture the formatted command and log path by value. GET_CONFIG returns
// references whose contents may change on a concurrent configuration reload.
auto log_file = ffmpeg_log.empty() ? ffmpeg_log : File::absolutePath("", ffmpeg_log);
Ticker ticker;
WorkThreadPool::Instance().getPoller()->async([timeout_sec, play_url, save_path, cb, ticker]() {
WorkThreadPool::Instance().getPoller()->async([timeout_sec, save_path, cb, ticker, cmd, log_file]() {
auto elapsed_ms = ticker.elapsedTime();
if (elapsed_ms > timeout_sec * 1000) {
// 超时，后台线程负载太高，当代太久才启动该任务 [AUTO-TRANSLATED:815606d6]
@@ -497,11 +508,7 @@ void FFmpegSnap::makeSnap(bool async, const string &play_url, const string &save
cb(false, "wait work poller schedule snap task timeout");
return;
}
char cmd[2048] = { 0 };
snprintf(cmd, sizeof(cmd), ffmpeg_snap.data(), File::absolutePath("", ffmpeg_bin).data(), play_url.data(), save_path.data());
std::shared_ptr<Process> process = std::make_shared<Process>();
auto log_file = ffmpeg_log.empty() ? ffmpeg_log : File::absolutePath("", ffmpeg_log);
process->run(cmd, log_file);
// 定时器延时应该减去后台任务启动的延时 [AUTO-TRANSLATED:7d224687]