9 #include "fuse_config.h" 
   22 #include <sys/prctl.h> 
   23 #include <sys/syscall.h> 
   24 #include <linux/capability.h> 
   25 #include <linux/securebits.h> 
   27 #if !defined(SECBIT_KEEP_CAPS) && defined(SECURE_KEEP_CAPS) 
   28 #define SECBIT_KEEP_CAPS (issecure_mask(SECURE_KEEP_CAPS)) 
   30 #if !defined(SECBIT_KEEP_CAPS_LOCKED) && defined(SECURE_KEEP_CAPS_LOCKED) 
   31 #define SECBIT_KEEP_CAPS_LOCKED (issecure_mask(SECURE_KEEP_CAPS_LOCKED)) 
   33 #if !defined(SECBIT_NO_SETUID_FIXUP) && defined(SECURE_NO_SETUID_FIXUP) 
   34 #define SECBIT_NO_SETUID_FIXUP (issecure_mask(SECURE_NO_SETUID_FIXUP)) 
   36 #if !defined(SECBIT_NO_SETUID_FIXUP_LOCKED) && defined(SECURE_NO_SETUID_FIXUP_LOCKED) 
   37 #define SECBIT_NO_SETUID_FIXUP_LOCKED (issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)) 
   39 #if !defined(SECBIT_NOROOT) && defined(SECURE_NOROOT) 
   40 #define SECBIT_NOROOT (issecure_mask(SECURE_NOROOT)) 
   42 #if !defined(SECBIT_NOROOT_LOCKED) && defined(SECURE_NOROOT_LOCKED) 
   43 #define SECBIT_NOROOT_LOCKED (issecure_mask(SECURE_NOROOT_LOCKED)) 
   47 #ifndef PR_SET_NO_NEW_PRIVS 
   48 #define PR_SET_NO_NEW_PRIVS 38 
   53 static char *progname;
 
   55 static char *xstrdup(
const char *s)
 
   59                 fprintf(stderr, 
"%s: failed to allocate memory\n", progname);
 
   65 static void *xrealloc(
void *oldptr, 
size_t size)
 
   67         void *ptr = realloc(oldptr, size);
 
   69                 fprintf(stderr, 
"%s: failed to allocate memory\n", progname);
 
   75 static void add_arg(
char **cmdp, 
const char *opt)
 
   77         size_t optlen = strlen(opt);
 
   78         size_t cmdlen = *cmdp ? strlen(*cmdp) : 0;
 
   79         if (optlen >= (SIZE_MAX - cmdlen - 4)/4) {
 
   80                 fprintf(stderr, 
"%s: argument too long\n", progname);
 
   83         char *cmd = xrealloc(*cmdp, cmdlen + optlen * 4 + 4);
 
  104 static char *add_option(
const char *opt, 
char *options)
 
  106         int oldlen = options ? strlen(options) : 0;
 
  108         options = xrealloc(options, oldlen + 1 + strlen(opt) + 1);
 
  110                 strcpy(options, opt);
 
  112                 strcat(options, 
",");
 
  113                 strcat(options, opt);
 
  118 static int prepare_fuse_fd(
const char *mountpoint, 
const char* subtype,
 
  123         int subtype_len = strlen(subtype) + 9;
 
  124         char* options_copy = xrealloc(NULL, subtype_len);
 
  126         snprintf(options_copy, subtype_len, 
"subtype=%s", subtype);
 
  127         options_copy = add_option(options, options_copy);
 
  133         flags = fcntl(fuse_fd, F_GETFD);
 
  134         if (flags == -1 || fcntl(fuse_fd, F_SETFD, flags & ~FD_CLOEXEC) == 1) {
 
  135                 fprintf(stderr, 
"%s: Failed to clear CLOEXEC: %s\n",
 
  136                         progname, strerror(errno));
 
  144 static uint64_t get_capabilities(
void)
 
  150         struct __user_cap_header_struct header = {
 
  151                 .version = _LINUX_CAPABILITY_VERSION_3,
 
  154         struct __user_cap_data_struct data[2];
 
  155         memset(data, 0, 
sizeof(data));
 
  156         if (syscall(SYS_capget, &header, data) == -1) {
 
  157                 fprintf(stderr, 
"%s: Failed to get capabilities: %s\n",
 
  158                         progname, strerror(errno));
 
  162         return data[0].effective | ((uint64_t) data[1].effective << 32);
 
  165 static void set_capabilities(uint64_t caps)
 
  171         struct __user_cap_header_struct header = {
 
  172                 .version = _LINUX_CAPABILITY_VERSION_3,
 
  175         struct __user_cap_data_struct data[2];
 
  176         memset(data, 0, 
sizeof(data));
 
  177         data[0].effective = data[0].permitted = caps;
 
  178         data[1].effective = data[1].permitted = caps >> 32;
 
  179         if (syscall(SYS_capset, &header, data) == -1) {
 
  180                 fprintf(stderr, 
"%s: Failed to set capabilities: %s\n",
 
  181                         progname, strerror(errno));
 
  186 static void drop_and_lock_capabilities(
void)
 
  189         if (prctl(PR_SET_SECUREBITS,
 
  190                   SECBIT_KEEP_CAPS_LOCKED |
 
  191                   SECBIT_NO_SETUID_FIXUP |
 
  192                   SECBIT_NO_SETUID_FIXUP_LOCKED |
 
  194                   SECBIT_NOROOT_LOCKED) == -1) {
 
  195                 fprintf(stderr, 
"%s: Failed to set securebits %s\n",
 
  196                         progname, strerror(errno));
 
  202         for (cap = 0; ; cap++) {
 
  203                 int cap_status = prctl(PR_CAPBSET_READ, cap);
 
  204                 if (cap_status == 0) {
 
  207                 if (cap_status == -1 && errno == EINVAL) {
 
  211                 if (cap_status != 1) {
 
  213                                 "%s: Failed to get capability %u: %s\n",
 
  214                                 progname, cap, strerror(errno));
 
  217                 if (prctl(PR_CAPBSET_DROP, cap) == -1) {
 
  219                                 "%s: Failed to drop capability %u: %s\n",
 
  220                                 progname, cap, strerror(errno));
 
  228         if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1) {
 
  229                 fprintf(stderr, 
"%s: Failed to set no_new_privs: %s\n",
 
  230                         progname, strerror(errno));
 
  236 int main(
int argc, 
char *argv[])
 
  240         char *dup_source = NULL;
 
  241         const char *mountpoint;
 
  243         char *options = NULL;
 
  244         char *command = NULL;
 
  245         char *setuid_name = NULL;
 
  249         int pass_fuse_fd = 0;
 
  251         int drop_privileges = 0;
 
  252         char *dev_fd_mountpoint = NULL;
 
  255         basename = strrchr(argv[0], 
'/');
 
  261         if (strncmp(basename, 
"mount.fuse.", 11) == 0)
 
  262                 type = basename + 11;
 
  263         if (strncmp(basename, 
"mount.fuseblk.", 14) == 0)
 
  264                 type = basename + 14;
 
  266         if (type && !type[0])
 
  271                         "usage: %s %s destination [-t type] [-o opt[,opts...]]\n",
 
  272                         progname, type ? 
"source" : 
"type#[source]");
 
  280         mountpoint = argv[2];
 
  282         for (i = 3; i < argc; i++) {
 
  283                 if (strcmp(argv[i], 
"-v") == 0) {
 
  285                 } 
else if (strcmp(argv[i], 
"-t") == 0) {
 
  290                                         "%s: missing argument to option '-t'\n",
 
  295                         if (strncmp(type, 
"fuse.", 5) == 0)
 
  297                         else if (strncmp(type, 
"fuseblk.", 8) == 0)
 
  302                                         "%s: empty type given as argument to option '-t'\n",
 
  306                 } 
else  if (strcmp(argv[i], 
"-o") == 0) {
 
  313                         opts = xstrdup(argv[i]);
 
  314                         opt = strtok(opts, 
",");
 
  318                                 const char *ignore_opts[] = { 
"",
 
  327                                 if (strncmp(opt, 
"setuid=", 7) == 0) {
 
  328                                         setuid_name = xstrdup(opt + 7);
 
  330                                 } 
else if (strcmp(opt,
 
  331                                                   "drop_privileges") == 0) {
 
  336                                 for (j = 0; ignore_opts[j]; j++)
 
  337                                         if (strcmp(opt, ignore_opts[j]) == 0)
 
  341                                         if (strcmp(opt, 
"nodev") == 0)
 
  343                                         else if (strcmp(opt, 
"nosuid") == 0)
 
  346                                         options = add_option(opt, options);
 
  348                                 opt = strtok(NULL, 
",");
 
  354         if (drop_privileges) {
 
  355                 uint64_t required_caps = CAP_TO_MASK(CAP_SETPCAP) |
 
  356                                 CAP_TO_MASK(CAP_SYS_ADMIN);
 
  357                 if ((get_capabilities() & required_caps) != required_caps) {
 
  358                         fprintf(stderr, 
"%s: drop_privileges was requested, which launches the FUSE file system fully unprivileged. In order to do so %s must be run with privileges, please invoke with CAP_SYS_ADMIN and CAP_SETPCAP (e.g. as root).\n",
 
  365                 options = add_option(
"dev", options);
 
  367                 options = add_option(
"suid", options);
 
  371                         dup_source = xstrdup(source);
 
  373                         source = strchr(type, 
'#');
 
  377                                 fprintf(stderr, 
"%s: empty filesystem type\n",
 
  382                         fprintf(stderr, 
"%s: empty source\n", progname);
 
  387         if (setuid_name && setuid_name[0]) {
 
  389                 if (drop_privileges) {
 
  398                         if (prctl(PR_SET_SECUREBITS,
 
  400                                   SECBIT_NO_SETUID_FIXUP) == -1) {
 
  402                                         "%s: Failed to set securebits %s\n",
 
  403                                         progname, strerror(errno));
 
  409                 struct passwd *pwd = getpwnam(setuid_name);
 
  410                 if (!pwd || setgid(pwd->pw_gid) == -1 || setuid(pwd->pw_uid) == -1) {
 
  411                         fprintf(stderr, 
"%s: Failed to setuid to %s: %s\n",
 
  412                                 progname, setuid_name, strerror(errno));
 
  415         } 
else if (!getenv(
"HOME")) {
 
  417                 setenv(
"HOME", 
"/root", 0);
 
  421                 fuse_fd = prepare_fuse_fd(mountpoint, type, options);
 
  422                 dev_fd_mountpoint = xrealloc(NULL, 20);
 
  423                 snprintf(dev_fd_mountpoint, 20, 
"/dev/fd/%u", fuse_fd);
 
  424                 mountpoint = dev_fd_mountpoint;
 
  428         if (drop_privileges) {
 
  429                 drop_and_lock_capabilities();
 
  432         add_arg(&command, type);
 
  434                 add_arg(&command, source);
 
  435         add_arg(&command, mountpoint);
 
  437                 add_arg(&command, 
"-o");
 
  438                 add_arg(&command, options);
 
  442         free(dev_fd_mountpoint);
 
  446         execl(
"/bin/sh", 
"/bin/sh", 
"-c", command, NULL);
 
  447         fprintf(stderr, 
"%s: failed to execute /bin/sh: %s\n", progname,
 
int fuse_open_channel(const char *mountpoint, const char *options)