Added sanity checks

remux.c

@@ -23,6 +23,7 @@ int main(int argc, char *argv[])
 	jobid = atoi(argv[1]);
 	path = mprintf("%s/%s", getenv(WORKER_RELEASED), jstr(jlookup(argv[4], "path"), ""));
 	tmp = mprintf("%s/.tmp-%i", getenv(WORKER_TMP), jobid);
+	overwrite_check(path);
 	ping_job(jobid, "running", 0);
 
 	demux = 0;
@@ -74,6 +75,9 @@ int main(int argc, char *argv[])
 	if (err = av_write_trailer(mux))
 		job_failed("Error writing trailer to temporary file", av_err2str(err));
 	avio_closep(&mux->pb);
+	if (!filesize(tmp))
+		job_failed("Sanity check failed: Output file is empty");
+	overwrite_check(path);
 	if (rename(tmp, path))
 		job_failed("Overwriting output file failed: %s", strerror(errno));
 	unlink(tmp);

thumbnail.c

@@ -98,6 +98,8 @@ int main(int argc, char *argv[])
 	if (err = av_write_trailer(mux))
 		job_failed("Error writing trailer to temporary file: %s", av_err2str(err));
 	avio_closep(&mux->pb);
+	if (!filesize(tmp))
+		job_failed("Sanity check failed: Output file is empty");
 	if (rename(tmp, dest))
 		job_failed("Overwriting output file failed: %s", strerror(errno));
 	unlink(tmp);

transcode.c

@@ -274,6 +274,7 @@ int main(int argc, char *argv[])
 	output = jlookup(argv[4], "output");
 	outpath = mprintf("%s/%s", getenv(WORKER_RELEASED), jstr(jlookup(output, "path"), ""));
 	tmppath = mprintf("%s/.tmp-%i", getenv(WORKER_TMP), jobid);
+	overwrite_check(outpath);
 
 	demux = 0;
 	opts = 0;
@@ -356,6 +357,9 @@ int main(int argc, char *argv[])
 	if (err = av_write_trailer(mux))
 		job_failed("Error writing trailer to temporary file", av_err2str(err));
 	avio_closep(&mux->pb);
+	if (!filesize(tmppath))
+		job_failed("Sanity check failed: Output file is empty");
+	overwrite_check(outpath);
 	if (rename(tmppath, outpath))
 		job_failed("Overwriting output file \"%s\" failed: %s", outpath, strerror(errno));
 	unlink(tmppath);

util.h

@@ -16,6 +16,7 @@ char *hashfile(char *path);
 double fileduration(char *path);
 size_t filesize(char *path);
 char *json_fileinfo(char *path);
+void overwrite_check(char *path);
 
 #define WORKER_APIKEY "WORKER_APIKEY"
 #define WORKER_APIBASE "WORKER_APIBASE"

util/overwrite_check.c

+#include <unistd.h>
+#include <sys/stat.h>
+
+#include "../util.h"
+
+void overwrite_check(char *path)
+{
+	struct stat s;
+	if (stat(path, &s) || !s.st_size)
+		return; /* We can overwrite non-existing or empty files */
+	if (s.st_uid != getuid())
+		job_failed("Refusing to overwrite output file \"%s\": File was not created by worker");
+}
+