#tmux #read #only #session this setuid executable allows you to connect other people's sessions as a readonly viewer

tmux.readonly.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>

#include <dlfcn.h>
#include <dirent.h>

int main(int argc, char **argv) {
	if(argc < 2) {
		printf(
			"Usage: %s <uid> [socket_name]\n"
			"Example: %s 2214 mysock\n"
			"\t'mysock' may be omitted (uses 'default')\n",
			argv[0], argv[0], NULL
		);
		return 1;
	}
	char buf[1024];
	struct stat fstat;
	stat(argv[0], &fstat);
	if(setuid(fstat.st_uid)) {
		//printf("Error: %s\n", strerror(errno));
		perror("Error (setuid)");
	};
	snprintf(buf, sizeof(buf), "/tmp/tmux-%d/%s",
		(argc > 1) ? atoi(argv[1]) : fstat.st_uid,
		(argc > 2) ? argv[2]       : "default",
		NULL
	);
	//execlp("tmux", "tmux.readonly", "-S", buf, "attach", "-r", NULL);
	char **args = (char**) calloc(6 + argc, sizeof(char*));
//	printf("argc: %d\n", argc);
	args[0] = "tmux";
	args[1] = "tmux.readonly";
	args[2] = "-S";
	args[3] = buf;
	args[4] = "attach";
	args[5] = "-r";
	if(argc > 2) memcpy(args+6, argv+3, sizeof(char*) * (argc-2));
//	for(char **arg=args; arg && *arg; arg++) printf("%s\n", *arg);
	execvp(args[0], args+1);
	return 0;
}