@@ -26,10 +26,6 @@
2626using namespace std;
2727
2828#define err_exit(format, ...) { fprintf(stderr, format ": %s\n", ##__VA_ARGS__, strerror(errno)); exit(EXIT_FAILURE); }
29−static int child_proc(const char *rootdir, const char *nixdir, uint8_t clear_env, list<struct DirMapping> dirMappings, list<struct SetEnv> envMappings, const char *executable, char * const new_argv[]);
30−
31−volatile uint8_t child_died = 0;
32−int child_pid = 0;
3329
3430static void usage(const char *pname) {
3531 fprintf(stderr, "Usage: %s -n <nixpath> -- <command>\n", pname);
@@ -37,7 +33,6 @@ static void usage(const char *pname) {
3733 fprintf(stderr, "\t-m <src>:<src>\tmap src on the host to dest in the sandbox\n");
3834 fprintf(stderr, "\t-d\tdelete all default dir mappings, may break things\n");
3935 fprintf(stderr, "\t-p <var>\tpreserve the value of a variable across the -c clear\n");
40− fprintf(stderr, "\t-e\tadd an /escape-hatch to the sandbox, and run (outside the sandbox) any strings written to it\n");
4136
4237 exit(EXIT_FAILURE);
4338}
@@ -96,15 +91,8 @@ struct DirMapping parseMapping(string input) {
9691 return (struct DirMapping){ src, dest };
9792}
9893
99−static void handle_child_death(int signo, siginfo_t *info, void *context) {
100− if ( (child_pid == 0) || (info->si_pid == child_pid) ) {
101− child_died = 1;
102− }
103−}
104−
10594int main(int argc, char *argv[]) {
10695 uint8_t clear_env = 0;
107− uint8_t enable_escape_hatch = 0;
10896 char *nixdir = NULL;
10997 list<struct DirMapping> dirMappings;
11098 list<struct SetEnv> envMappings;
@@ -117,20 +105,14 @@ int main(int argc, char *argv[]) {
117105 x("run");
118106 x("tmp");
119107 x("var");
120− x("etc");
121− x("usr");
122− x("home");
123− x("root");
124108#undef x
125109
126110 int opt;
127− while ((opt = getopt(argc, argv, "cen:m:dp:")) != -1) {
111+ while ((opt = getopt(argc, argv, "cn:m:dp:")) != -1) {
128112 switch (opt) {
129113 case 'c':
130114 clear_env = 1;
131− break;
132− case 'e':
133− enable_escape_hatch = 1;
115+ puts("clearing env");
134116 break;
135117 case 'n':
136118 // determine absolute directory for nix dir
@@ -179,74 +161,13 @@ int main(int argc, char *argv[]) {
179161 err_exit("mkdtemp(%s)", template_);
180162 }
181163
182− int unrace[2];
183−
184− if (pipe(unrace)) {
185− err_exit("pipe()");
186− }
187−
188− struct sigaction handle_child;
189− handle_child.sa_sigaction = handle_child_death;
190− handle_child.sa_flags = SA_SIGINFO;
191−
192− struct sigaction old_handler;
193− if (sigaction(SIGCHLD, &handle_child, &old_handler)) {
194− err_exit("sigaction()");
195− }
196−
197− int child;
198− child = child_pid = fork();
199− if (child < 0) {
200− err_exit("fork()");
201− } else if (child == 0) {
202− sigaction(SIGCHLD, &old_handler, NULL);
203− close(unrace[1]);
204− char buf[10];
205− read(unrace[0], buf, 10);
206− close(unrace[0]);
207− return child_proc(rootdir, nixdir, clear_env, dirMappings, envMappings, argv[optind], argv + optind);
208− } else {
209− close(unrace[0]);
210− char fifopath[PATH_MAX];
211− if (enable_escape_hatch) {
212− snprintf(fifopath, PATH_MAX, "%s/escape-hatch", rootdir);
213− mkfifo(fifopath, 0600);
214− }
215− close(unrace[1]);
216− if (enable_escape_hatch) {
217− char buffer[1024];
218− while (!child_died) {
219− int fd = open(fifopath, O_RDONLY);
220− if (fd < 0) {
221− if (errno == EINTR) continue;
222− fprintf(stderr, "error opening escape-hatch: %s\n", strerror(errno));
223− continue;
224− }
225− int size = read(fd, buffer, 1024);
226− buffer[size] = 0;
227− system(buffer);
228− close(fd);
229− }
230− }
231− int status;
232− int ret = waitpid(child, &status, 0);
233− return WEXITSTATUS(status);
234− }
235−}
236−
237−static int child_proc(const char *rootdir, const char *nixdir, uint8_t clear_env, list<struct DirMapping> dirMappings, list<struct SetEnv> envMappings, const char *executable, char * const new_argv[]) {
238164 // get uid, gid before going to new namespace
239165 uid_t uid = getuid();
240166 gid_t gid = getgid();
241167
242168 // "unshare" into new namespace
243169 if (unshare(CLONE_NEWNS | CLONE_NEWUSER) < 0) {
244− if (errno == EPERM) {
245− fputs("Run the following to enable unprivileged namespace use:\nsudo bash -c \"sysctl -w kernel.unprivileged_userns_clone=1 ; echo kernel.unprivileged_userns_clone=1 > /etc/sysctl.d/nix-user-chroot.conf\"\n\n", stderr);
246− exit(EXIT_FAILURE);
247− } else {
248− err_exit("unshare()");
249− }
170+ err_exit("unshare()");
250171 }
251172
252173 // add necessary system stuff to rootdir namespace
@@ -256,52 +177,57 @@ static int child_proc(const char *rootdir, const char *nixdir, uint8_t clear_env
256177 add_path(m.src, m.dest, rootdir);
257178 }
258179
259− // make sure nixdir exists
260− struct stat statbuf2;
261− if (stat(nixdir, &statbuf2) < 0) {
262− err_exit("stat(%s)", nixdir);
263− }
180+ char path_buf[PATH_MAX];
181+ snprintf(path_buf, sizeof(path_buf), "%s/tmp", rootdir);
182+ mkdir(path_buf, ~0);
183+ snprintf(path_buf, sizeof(path_buf), "%s/var", rootdir);
264184
265− char path_buf[PATH_MAX];
266− // mount /nix to new namespace
267− snprintf(path_buf, sizeof(path_buf), "%s/nix", rootdir);
268− mkdir(path_buf, statbuf2.st_mode & ~S_IFMT);
269− if (mount(nixdir, path_buf, "none", MS_BIND | MS_REC, NULL) < 0) {
270− err_exit("mount(%s, %s)", nixdir, path_buf);
271− }
185+ // make sure nixdir exists
186+ struct stat statbuf2;
187+ if (stat(nixdir, &statbuf2) < 0) {
188+ err_exit("stat(%s)", nixdir);
189+ }
272190
273− // fixes issue #1 where writing to /proc/self/gid_map fails
274− // see user_namespaces(7) for more documentation
275− int fd_setgroups = open("/proc/self/setgroups", O_WRONLY);
276− if (fd_setgroups > 0) {
277− write(fd_setgroups, "deny", 4);
278− close(fd_setgroups);
279− }
191+ // mount /nix to new namespace
192+ snprintf(path_buf, sizeof(path_buf), "%s/nix", rootdir);
193+ mkdir(path_buf, statbuf2.st_mode & ~S_IFMT);
194+ if (mount(nixdir, path_buf, "none", MS_BIND | MS_REC, NULL) < 0) {
195+ err_exit("mount(%s, %s)", nixdir, path_buf);
196+ }
197+
198+ // fixes issue #1 where writing to /proc/self/gid_map fails
199+ // see user_namespaces(7) for more documentation
200+ int fd_setgroups = open("/proc/self/setgroups", O_WRONLY);
201+ if (fd_setgroups > 0) {
202+ write(fd_setgroups, "deny", 4);
203+ }
280204
281− // map the original uid/gid in the new ns
282− char map_buf[1024];
283− snprintf(map_buf, sizeof(map_buf), "%d %d 1", uid, uid);
284− update_map(map_buf, "/proc/self/uid_map");
285− snprintf(map_buf, sizeof(map_buf), "%d %d 1", gid, gid);
286− update_map(map_buf, "/proc/self/gid_map");
205+ // map the original uid/gid in the new ns
206+ char map_buf[1024];
207+ snprintf(map_buf, sizeof(map_buf), "%d %d 1", uid, uid);
208+ update_map(map_buf, "/proc/self/uid_map");
209+ snprintf(map_buf, sizeof(map_buf), "%d %d 1", gid, gid);
210+ update_map(map_buf, "/proc/self/gid_map");
287211
288− // chroot to rootdir
289− if (chroot(rootdir) < 0) {
290− err_exit("chroot(%s)", rootdir);
291− }
212+ // chroot to rootdir
213+ if (chroot(rootdir) < 0) {
214+ err_exit("chroot(%s)", rootdir);
215+ }
292216
293− chdir("/");
217+ chdir("/");
294218
295219 if (clear_env) clearenv();
220+ setenv("NIX_PATH", NIX_PATH, 1);
221+ setenv("NIX_SSL_CERT_FILE", NIX_SSL_CERT_FILE, 1);
296222 setenv("PATH", ENV_PATH, 1);
297223
298224 for (list<struct SetEnv>::iterator it = envMappings.begin();
299− it != envMappings.end(); ++it) {
225+ it != envMappings.end(); ++it) {
300226 struct SetEnv e = *it;
301227 setenv(e.key.c_str(), e.value.c_str(), 1);
302228 }
303229
304230 // execute the command
305− execvp(executable, new_argv);
306− err_exit("execvp(%s)", executable);
231+ execvp(argv[optind], argv + optind);
232+ err_exit("execvp(%s)", argv[optind]);
307233}