jail: reworks & cleanups
[project/procd.git] / jail / jail.c
index 2bba292..f8139b8 100644 (file)
 #include <libubox/uloop.h>
 
 #define STACK_SIZE     (1024 * 1024)
-#define OPT_ARGS       "P:S:n:r:w:psuldo"
+#define OPT_ARGS       "P:S:n:r:w:d:psulo"
+
+static struct {
+       char *path;
+       char *name;
+       char **jail_argv;
+       char *seccomp;
+       int procfs;
+       int ronly;
+       int sysfs;
+} opts;
 
 struct extra {
        struct list_head list;
@@ -125,7 +135,7 @@ static int mount_bind(const char *root, const char *path, const char *name, int
                return -1;
        }
 
-       if (readonly && mount(old, new, NULL, MS_BIND | MS_REMOUNT | MS_RDONLY, NULL)) {
+       if (readonly && mount(NULL, new, NULL, MS_BIND | MS_REMOUNT | MS_RDONLY, NULL)) {
                ERROR("failed to remount ro %s: %s\n", new, strerror(errno));
                return -1;
        }
@@ -135,80 +145,75 @@ static int mount_bind(const char *root, const char *path, const char *name, int
        return 0;
 }
 
-static int build_jail(const char *path)
+static int build_jail_fs()
 {
        struct library *l;
        struct extra *m;
-       int ret = 0;
 
-       mkdir(path, 0755);
-
-       if (mount("tmpfs", path, "tmpfs", MS_NOATIME, "mode=0755")) {
+       if (mount("tmpfs", opts.path, "tmpfs", MS_NOATIME, "mode=0755")) {
                ERROR("tmpfs mount failed %s\n", strerror(errno));
                return -1;
        }
 
-       avl_for_each_element(&libraries, l, avl)
-               if (mount_bind(path, l->path, l->name, 1, -1))
-                       return -1;
-
-       list_for_each_entry(m, &extras, list)
-               if (mount_bind(path, m->path, m->name, m->readonly, 0))
-                       return -1;
-
-       return ret;
-}
+       if (chdir(opts.path)) {
+               ERROR("failed to chdir() in the jail root\n");
+               return -1;
+       }
 
-static void _umount(const char *root, const char *path)
-{
-       char *buf = NULL;
+       avl_init(&libraries, avl_strcmp, false, NULL);
+       alloc_library_path("/lib64");
+       alloc_library_path("/lib");
+       alloc_library_path("/usr/lib");
+       load_ldso_conf("/etc/ld.so.conf");
 
-       if (asprintf(&buf, "%s%s", root, path) < 0) {
-               ERROR("failed to alloc umount buffer: %s\n", strerror(errno));
-       } else {
-               DEBUG("umount %s\n", buf);
-               umount(buf);
-               free(buf);
+       if (elf_load_deps(*opts.jail_argv)) {
+               ERROR("failed to load dependencies\n");
+               return -1;
        }
-}
 
-static int stop_jail(const char *root)
-{
-       struct library *l;
-       struct extra *m;
+       if (opts.seccomp && elf_load_deps("libpreload-seccomp.so")) {
+               ERROR("failed to load libpreload-seccomp.so\n");
+               return -1;
+       }
 
-       avl_for_each_element(&libraries, l, avl) {
-               char path[256];
-               char *p = l->path;
+       avl_for_each_element(&libraries, l, avl)
+               if (mount_bind(opts.path, l->path, l->name, 1, -1))
+                       return -1;
 
-               if (strstr(p, "local"))
-                       p = "/lib";
+       list_for_each_entry(m, &extras, list)
+               if (mount_bind(opts.path, m->path, m->name, m->readonly, 0))
+                       return -1;
 
-               snprintf(path, sizeof(path), "%s%s/%s", root, p, l->name);
-               DEBUG("umount %s\n", path);
-               umount(path);
+       char *mpoint;
+       if (asprintf(&mpoint, "%s/old", opts.path) < 0) {
+               ERROR("failed to alloc pivot path: %s\n", strerror(errno));
+               return -1;
        }
-
-       list_for_each_entry(m, &extras, list) {
-               char path[256];
-
-               snprintf(path, sizeof(path), "%s%s/%s", root, m->path, m->name);
-               DEBUG("umount %s\n", path);
-               umount(path);
+       mkdir_p(mpoint, 0755);
+       if (pivot_root(opts.path, mpoint) == -1) {
+               ERROR("pivot_root failed:%s\n", strerror(errno));
+               free(mpoint);
+               return -1;
        }
-
-       _umount(root, "/proc");
-       _umount(root, "/sys");
-
-       DEBUG("umount %s\n", root);
-       umount(root);
-       rmdir(root);
+       free(mpoint);
+       umount2("/old", MNT_DETACH);
+       rmdir("/old");
+       if (opts.procfs) {
+               mkdir("/proc", 0755);
+               mount("proc", "/proc", "proc", MS_NOATIME, 0);
+       }
+       if (opts.sysfs) {
+               mkdir("/sys", 0755);
+               mount("sysfs", "/sys", "sysfs", MS_NOATIME, 0);
+       }
+       if (opts.ronly)
+               mount(NULL, "/", NULL, MS_RDONLY | MS_REMOUNT, 0);
 
        return 0;
 }
 
 #define MAX_ENVP       8
-static char** build_envp(const char *seccomp, int debug)
+static char** build_envp(const char *seccomp)
 {
        static char *envp[MAX_ENVP];
        static char preload_var[64];
@@ -227,177 +232,77 @@ static char** build_envp(const char *seccomp, int debug)
                snprintf(preload_var, sizeof(preload_var), "LD_PRELOAD=%s", preload_lib);
                envp[count++] = preload_var;
        }
-       if (debug)
+       if (debug > 1)
                envp[count++] = debug_var;
 
        return envp;
 }
 
-static int spawn(const char *path, char **argv, const char *seccomp)
-{
-       pid_t pid = fork();
-
-       if (pid < 0) {
-               ERROR("failed to spawn %s: %s\n", *argv, strerror(errno));
-               return -1;
-       } else if (!pid) {
-               char **envp = build_envp(seccomp, 0);
-
-               INFO("spawning %s\n", *argv);
-               execve(*argv, argv, envp);
-               ERROR("failed to spawn child %s: %s\n", *argv, strerror(errno));
-               exit(-1);
-       }
-
-       return pid;
-}
-
-static int usage(void)
+static void usage(void)
 {
-       fprintf(stderr, "jail <options> -D <binary> <params ...>\n");
+       fprintf(stderr, "ujail <options> -- <binary> <params ...>\n");
        fprintf(stderr, "  -P <path>\tpath where the jail will be staged\n");
        fprintf(stderr, "  -S <file>\tseccomp filter\n");
        fprintf(stderr, "  -n <name>\tthe name of the jail\n");
        fprintf(stderr, "  -r <file>\treadonly files that should be staged\n");
        fprintf(stderr, "  -w <file>\twriteable files that should be staged\n");
-       fprintf(stderr, "  -p\t\tjail has /proc\t\n");
-       fprintf(stderr, "  -s\t\tjail has /sys\t\n");
-       fprintf(stderr, "  -l\t\tjail has /dev/log\t\n");
-       fprintf(stderr, "  -u\t\tjail has a ubus socket\t\n");
-
-       return -1;
+       fprintf(stderr, "  -d <num>\tshow debug log (increase num to increase verbosity)\n");
+       fprintf(stderr, "  -p\t\tjail has /proc\n");
+       fprintf(stderr, "  -s\t\tjail has /sys\n");
+       fprintf(stderr, "  -l\t\tjail has /dev/log\n");
+       fprintf(stderr, "  -u\t\tjail has a ubus socket\n");
+       fprintf(stderr, "  -o\t\tremont jail root (/) read only\n");
+       fprintf(stderr, "\nWarning: by default root inside the jail is the same\n\
+and he has the same powers as root outside the jail,\n\
+thus he can escape the jail and/or break stuff.\n\
+Please use an appropriate seccomp filter (-S) to restrict his powers\n");
 }
 
-static int child_running = 1;
-
-static void child_process_handler(struct uloop_process *c, int ret)
-{
-       INFO("child (%d) exited: %d\n", c->pid, ret);
-       uloop_end();
-       child_running = 0;
-}
-
-struct uloop_process child_process = {
-       .cb = child_process_handler,
-};
-
-static int spawn_child(void *arg)
+static int spawn_jail(void *arg)
 {
-       char *path = get_current_dir_name();
-       int procfs = 0, sysfs = 0;
-       char *seccomp = NULL;
-       char **argv = arg;
-       int argc = 0, ch;
-       char *mpoint;
-       int ronly = 0;
-
-       while (argv[argc])
-               argc++;
-
-       optind = 0;
-       while ((ch = getopt(argc, argv, OPT_ARGS)) != -1) {
-               switch (ch) {
-               case 'd':
-                       debug = 1;
-                       break;
-               case 'S':
-                       seccomp = optarg;
-                       break;
-               case 'p':
-                       procfs = 1;
-                       break;
-               case 'o':
-                       ronly = 1;
-                       break;
-               case 's':
-                       sysfs = 1;
-                       break;
-               case 'n':
-                       if (sethostname(optarg, strlen(optarg)))
-                               ERROR("failed to sethostname: %s\n", strerror(errno));
-                       break;
-               }
+       if (opts.name && sethostname(opts.name, strlen(opts.name))) {
+               ERROR("failed to sethostname: %s\n", strerror(errno));
        }
 
-       if (asprintf(&mpoint, "%s/old", path) < 0) {
-               ERROR("failed to alloc pivot path: %s\n", strerror(errno));
-               return -1;
-       }
-       mkdir_p(mpoint, 0755);
-       if (pivot_root(path, mpoint) == -1) {
-               ERROR("pivot_root failed:%s\n", strerror(errno));
-               return -1;
-       }
-       free(mpoint);
-       umount2("/old", MNT_DETACH);
-       rmdir("/old");
-       if (procfs) {
-               mkdir("/proc", 0755);
-               mount("proc", "/proc", "proc", MS_NOATIME, 0);
-       }
-       if (sysfs) {
-               mkdir("/sys", 0755);
-               mount("sysfs", "/sys", "sysfs", MS_NOATIME, 0);
+       if (build_jail_fs()) {
+               ERROR("failed to build jail fs");
+               exit(EXIT_FAILURE);
        }
-       if (ronly)
-               mount(NULL, "/", NULL, MS_RDONLY | MS_REMOUNT, 0);
 
-       uloop_init();
+       char **envp = build_envp(opts.seccomp);
+       if (!envp)
+               exit(EXIT_FAILURE);
 
-       child_process.pid = spawn(path, &argv[optind], seccomp);
-       uloop_process_add(&child_process);
-       uloop_run();
-       uloop_done();
-       if (child_running) {
-               kill(child_process.pid, SIGTERM);
-               waitpid(child_process.pid, NULL, 0);
-       }
+       //TODO: drop capabilities() here
+       //prctl(PR_CAPBSET_DROP, ..., 0, 0, 0);
 
-       return 0;
+       INFO("exec-ing %s\n", *opts.jail_argv);
+       execve(*opts.jail_argv, opts.jail_argv, envp);
+       //we get there only if execve fails
+       ERROR("failed to execve %s: %s\n", *opts.jail_argv, strerror(errno));
+       exit(EXIT_FAILURE);
 }
 
-static int namespace_running = 1;
+static int jail_running = 1;
+static int jail_return_code = 0;
 
-static void namespace_process_handler(struct uloop_process *c, int ret)
+static void jail_process_handler(struct uloop_process *c, int ret)
 {
-       INFO("namespace (%d) exited: %d\n", c->pid, ret);
+       if (WIFEXITED(ret)) {
+               jail_return_code = WEXITSTATUS(ret);
+               INFO("jail (%d) exited with exit: %d\n", c->pid, jail_return_code);
+       } else {
+               jail_return_code = WTERMSIG(ret);
+               INFO("jail (%d) exited with signal: %d\n", c->pid, jail_return_code);
+       }
+       jail_running = 0;
        uloop_end();
-       namespace_running = 0;
 }
 
-struct uloop_process namespace_process = {
-       .cb = namespace_process_handler,
+static struct uloop_process jail_process = {
+       .cb = jail_process_handler,
 };
 
-static void spawn_namespace(const char *path, int argc, char **argv)
-{
-       char *dir = get_current_dir_name();
-
-       uloop_init();
-       if (chdir(path)) {
-               ERROR("failed to chdir() into the jail\n");
-               return;
-       }
-       namespace_process.pid = clone(spawn_child,
-                       child_stack + STACK_SIZE,
-                       CLONE_NEWUTS | CLONE_NEWPID | CLONE_NEWNS | SIGCHLD, argv);
-
-       if (namespace_process.pid != -1) {
-               if (chdir(dir))
-                       ERROR("failed to chdir() out of the jail\n");
-               free(dir);
-               uloop_process_add(&namespace_process);
-               uloop_run();
-               uloop_done();
-               if (namespace_running) {
-                       kill(namespace_process.pid, SIGTERM);
-                       waitpid(namespace_process.pid, NULL, 0);
-               }
-       } else {
-               ERROR("failed to spawn namespace: %s\n", strerror(errno));
-       }
-}
-
 static void add_extra(char *name, int readonly)
 {
        struct extra *f;
@@ -419,16 +324,14 @@ static void add_extra(char *name, int readonly)
 int main(int argc, char **argv)
 {
        uid_t uid = getuid();
-       const char *name = NULL;
-       char *path = NULL;
-       struct stat s;
-       int ch, ret;
        char log[] = "/dev/log";
        char ubus[] = "/var/run/ubus.sock";
+       int ret = EXIT_SUCCESS;
+       int ch;
 
        if (uid) {
                ERROR("not root, aborting: %s\n", strerror(errno));
-               return -1;
+               return EXIT_FAILURE;
        }
 
        umask(022);
@@ -436,15 +339,27 @@ int main(int argc, char **argv)
        while ((ch = getopt(argc, argv, OPT_ARGS)) != -1) {
                switch (ch) {
                case 'd':
-                       debug = 1;
+                       debug = atoi(optarg);
+                       break;
+               case 'p':
+                       opts.procfs = 1;
+                       break;
+               case 'o':
+                       opts.ronly = 1;
+                       break;
+               case 's':
+                       opts.sysfs = 1;
+                       break;
+               case 'S':
+                       opts.seccomp = optarg;
+                       add_extra(optarg, 1);
                        break;
                case 'P':
-                       path = optarg;
+                       opts.path = optarg;
                        break;
                case 'n':
-                       name = optarg;
+                       opts.name = optarg;
                        break;
-               case 'S':
                case 'r':
                        add_extra(optarg, 1);
                        break;
@@ -460,46 +375,52 @@ int main(int argc, char **argv)
                }
        }
 
-       if (argc - optind < 1)
-               return usage();
-
-       if (!path && asprintf(&path, "/tmp/%s", basename(argv[optind])) == -1) {
-               ERROR("failed to set root path\n: %s", strerror(errno));
-               return -1;
+       //no <binary> param found
+       if (argc - optind < 1) {
+               usage();
+               return EXIT_FAILURE;
        }
 
-       if (!stat(path, &s)) {
-               ERROR("%s already exists: %s\n", path, strerror(errno));
-               return -1;
-       }
+       opts.jail_argv = &argv[optind];
 
-       if (name)
-               prctl(PR_SET_NAME, name, NULL, NULL, NULL);
+       if (opts.name)
+               prctl(PR_SET_NAME, opts.name, NULL, NULL, NULL);
 
-       avl_init(&libraries, avl_strcmp, false, NULL);
-       alloc_library_path("/lib64");
-       alloc_library_path("/lib");
-       alloc_library_path("/usr/lib");
-       load_ldso_conf("/etc/ld.so.conf");
-
-       if (elf_load_deps(argv[optind])) {
-               ERROR("failed to load dependencies\n");
-               return -1;
+       if (!opts.path && asprintf(&opts.path, "/tmp/%s", basename(*opts.jail_argv)) == -1) {
+               ERROR("failed to asprintf root path: %s\n", strerror(errno));
+               return EXIT_FAILURE;
        }
 
-       if (elf_load_deps("libpreload-seccomp.so")) {
-               ERROR("failed to load libpreload-seccomp.so\n");
-               return -1;
+       if (mkdir(opts.path, 0755)) {
+               ERROR("unable to create root path: %s (%s)\n", opts.path, strerror(errno));
+               return EXIT_FAILURE;
        }
 
-       ret = build_jail(path);
+       uloop_init();
+       jail_process.pid = clone(spawn_jail,
+                       child_stack + STACK_SIZE,
+                       CLONE_NEWUTS | CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWIPC | SIGCHLD, argv);
 
-       if (!ret)
-               spawn_namespace(path, argc, argv);
-       else
-               ERROR("failed to build jail\n");
+       if (jail_process.pid != -1) {
+               uloop_process_add(&jail_process);
+               uloop_run();
+               uloop_done();
+               if (jail_running) {
+                       kill(jail_process.pid, SIGTERM);
+                       waitpid(jail_process.pid, NULL, 0);
+               }
+       } else {
+               ERROR("failed to spawn namespace: %s\n", strerror(errno));
+               ret = EXIT_FAILURE;
+       }
 
-       stop_jail(path);
+       if (rmdir(opts.path)) {
+               ERROR("Unable to remove root path: %s (%s)\n", opts.path, strerror(errno));
+               ret = EXIT_FAILURE;
+       }
 
-       return ret;
+       if (ret)
+               return ret;
+
+       return jail_return_code;
 }