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/* See LICENSE file for copyright and license details. */
#define _GNU_SOURCE
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/wait.h>
#include "mount.c"
#ifndef MNTRUN_VERSION
#define MNTRUN_VERSION "(unknown)"
#endif
#define USAGE "usage: mntrun [-dhv] [-b source dest] [[-o|-m] upperdir lowerdir workdir mountpoint] command\n"
static inline int checkflag(char *arg, char f) {
return arg && (arg[0] == '-' && arg[1] == f && arg[2] == '\0');
}
int namespace_main(void *data) {
uid_t uid = getuid();
gid_t gid = getgid();
int verbose = 0;
char **argv = data;
if(checkflag(argv[0], 'h')) {
fputs(USAGE, stderr);
return EXIT_SUCCESS;
}
if(checkflag(argv[0], 'v')) {
puts("mntrun " MNTRUN_VERSION);
return EXIT_SUCCESS;
}
if(checkflag(argv[0], 'd')) {
verbose = 1;
argv ++;
}
/* Jump back here over-and-over until all mount directives are parsed. */
do_mounts:
if(checkflag(argv[0], 'b')) {
if(!argv[1] || !argv[2]) goto exit_usage;
if(mount_bind(argv[1], argv[2]) == -1) {
if(errno) fprintf(stderr, "Failed to bind '%s' to '%s': %s\n", argv[1], argv[2], strerror(errno));
return EXIT_FAILURE;
}
argv += 3;
goto do_mounts;
}
int merge = 0;
if(checkflag(argv[0], 'o') || (merge = checkflag(argv[0], 'm'))) {
char *type_str = merge ? "merge" : "overlay";
if(!argv[1] || !argv[2] || !argv[3] || !argv[4]) goto exit_usage;
if(verbose) printf("[%s]\n\tlower=%s\n\tupper=%s\n\twork=%s\n\tmount=%s\n", type_str, argv[1], argv[2], argv[3], argv[4]);
char *lowers = argv[1];
if(merge) {
lowers = malloc(strlen(argv[4]) + 1 + strlen(argv[1]));
sprintf(lowers, "%s:%s", argv[4], argv[1]);
}
if(mount_overlay(uid, gid, lowers, argv[2], argv[3], argv[4]) == -1) {
if(errno) fprintf(stderr, "Failed to mount %s on '%s': %s\n", type_str, argv[4], strerror(errno));
return EXIT_FAILURE;
}
argv += 5;
if(merge) {
free(lowers);
merge = 0;
}
goto do_mounts;
}
/* Check if a command was specified */
if(!argv[0]) goto exit_usage;
setuid(uid);
/* These next lines take the remaining values in `argv` and join them with spaces in `command`. */
int charc;
for(int i = 0; argv[i]; i ++) charc += strlen(argv[i]);
char *command = malloc(charc + 1);
command[0] = '\0';
for(int i = 0; argv[i]; i ++) {
strcat(command, " ");
strcat(command, argv[i]);
}
int status = system(command);
if(status == -1) {
perror("system");
return EXIT_FAILURE;
}
return status;
exit_usage:
fputs(USAGE, stderr);
return EXIT_FAILURE;
}
int main(int argc, char **argv) {
#define STACK_SIZE 1024 * 1024
char *stack = malloc(STACK_SIZE);
pid_t pid = clone(namespace_main, stack + STACK_SIZE, CLONE_NEWNS | SIGCHLD, argv + 1);
if(pid == -1) {
perror("Failed to create a new mount namespace");
return EXIT_FAILURE;
}
int wstatus;
if (waitpid(pid, &wstatus, 0) == -1) {
/* The only error which may occurs is EINTR, but I'm not 100% sure. */
perror("waitpid");
return EXIT_FAILURE;
}
return WEXITSTATUS(wstatus);
}
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