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https://github.com/ilyakooo0/nix-bundle.git
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Merge pull request #41 from input-output-hk/escape-hatch
add an escape-hatch option to allow things like xdg-open to work inside the sandbox
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commit
113d8c6b42
@ -26,6 +26,10 @@
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using namespace std;
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#define err_exit(format, ...) { fprintf(stderr, format ": %s\n", ##__VA_ARGS__, strerror(errno)); exit(EXIT_FAILURE); }
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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[]);
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volatile uint8_t child_died = 0;
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int child_pid = 0;
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static void usage(const char *pname) {
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fprintf(stderr, "Usage: %s -n <nixpath> -- <command>\n", pname);
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@ -33,6 +37,7 @@ static void usage(const char *pname) {
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fprintf(stderr, "\t-m <src>:<src>\tmap src on the host to dest in the sandbox\n");
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fprintf(stderr, "\t-d\tdelete all default dir mappings, may break things\n");
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fprintf(stderr, "\t-p <var>\tpreserve the value of a variable across the -c clear\n");
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fprintf(stderr, "\t-e\tadd an /escape-hatch to the sandbox, and run (outside the sandbox) any strings written to it\n");
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exit(EXIT_FAILURE);
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}
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@ -91,8 +96,15 @@ struct DirMapping parseMapping(string input) {
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return (struct DirMapping){ src, dest };
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}
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static void handle_child_death(int signo, siginfo_t *info, void *context) {
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if ( (child_pid == 0) || (info->si_pid == child_pid) ) {
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child_died = 1;
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}
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}
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int main(int argc, char *argv[]) {
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uint8_t clear_env = 0;
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uint8_t enable_escape_hatch = 0;
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char *nixdir = NULL;
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list<struct DirMapping> dirMappings;
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list<struct SetEnv> envMappings;
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@ -111,11 +123,14 @@ int main(int argc, char *argv[]) {
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#undef x
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int opt;
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while ((opt = getopt(argc, argv, "cn:m:dp:")) != -1) {
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while ((opt = getopt(argc, argv, "cen:m:dp:")) != -1) {
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switch (opt) {
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case 'c':
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clear_env = 1;
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break;
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case 'e':
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enable_escape_hatch = 1;
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break;
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case 'n':
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// determine absolute directory for nix dir
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nixdir = realpath(optarg, NULL);
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@ -163,6 +178,62 @@ int main(int argc, char *argv[]) {
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err_exit("mkdtemp(%s)", template_);
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}
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int unrace[2];
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if (pipe(unrace)) {
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err_exit("pipe()");
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}
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struct sigaction handle_child;
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handle_child.sa_sigaction = handle_child_death;
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handle_child.sa_flags = SA_SIGINFO;
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struct sigaction old_handler;
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if (sigaction(SIGCHLD, &handle_child, &old_handler)) {
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err_exit("sigaction()");
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}
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int child;
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child = child_pid = fork();
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if (child < 0) {
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err_exit("fork()");
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} else if (child == 0) {
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sigaction(SIGCHLD, &old_handler, NULL);
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close(unrace[1]);
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char buf[10];
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read(unrace[0], buf, 10);
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close(unrace[0]);
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return child_proc(rootdir, nixdir, clear_env, dirMappings, envMappings, argv[optind], argv + optind);
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} else {
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close(unrace[0]);
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char fifopath[PATH_MAX];
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if (enable_escape_hatch) {
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snprintf(fifopath, PATH_MAX, "%s/escape-hatch", rootdir);
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mkfifo(fifopath, 0600);
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}
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close(unrace[1]);
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if (enable_escape_hatch) {
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char buffer[1024];
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while (!child_died) {
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int fd = open(fifopath, O_RDONLY);
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if (fd < 0) {
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if (errno == EINTR) continue;
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fprintf(stderr, "error opening escape-hatch: %s\n", strerror(errno));
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continue;
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}
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int size = read(fd, buffer, 1024);
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buffer[size] = 0;
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system(buffer);
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close(fd);
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}
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}
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int status;
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int ret = waitpid(child, &status, 0);
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return WEXITSTATUS(status);
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}
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}
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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[]) {
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// get uid, gid before going to new namespace
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uid_t uid = getuid();
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gid_t gid = getgid();
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@ -170,7 +241,7 @@ int main(int argc, char *argv[]) {
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// "unshare" into new namespace
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if (unshare(CLONE_NEWNS | CLONE_NEWUSER) < 0) {
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if (errno == EPERM) {
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fputs("Run the following as root to enable unprivileged namespace use:\nsysctl -w kernel.unprivileged_userns_clone=1 ; echo kernel.unprivileged_userns_clone=1 > /etc/sysctl.d/nix-user-chroot.conf\n\n", stderr);
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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);
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exit(EXIT_FAILURE);
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} else {
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err_exit("unshare()");
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@ -230,6 +301,6 @@ int main(int argc, char *argv[]) {
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}
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// execute the command
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execvp(argv[optind], argv + optind);
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err_exit("execvp(%s)", argv[optind]);
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execvp(executable, new_argv);
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err_exit("execvp(%s)", executable);
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}
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