keep-fd option (#4845)

contrib/vim/syntax/firejail.vim

@@ -51,7 +51,7 @@ syn match fjVar /\v\$\{(CFG|DESKTOP|DOCUMENTS|DOWNLOADS|HOME|MUSIC|PATH|PICTURES
 " Generate list with: { rg -o 'strn?cmp\(ptr, "([^"]+) "' -r '$1' src/firejail/profile.c; echo private-lib; } | grep -vEx '(include|ignore|caps\.drop|caps\.keep|protocol|seccomp|seccomp\.drop|seccomp\.keep|env|rmenv|net|ip)' | sort -u | tr $'\n' '|' # private-lib is special-cased in the code and doesn't match the regex; grep-ed patterns are handled later with 'syn match nextgroup=' directives (except for include which is special-cased as a fjCommandNoCond keyword)
 syn match fjCommand /\v(bind|blacklist|blacklist-nolog|cgroup|cpu|defaultgw|dns|hostname|hosts-file|ip6|iprange|join-or-start|mac|mkdir|mkfile|mtu|name|netfilter|netfilter6|netmask|nice|noblacklist|noexec|nowhitelist|overlay-named|private|private-bin|private-cwd|private-etc|private-home|private-lib|private-opt|private-srv|read-only|read-write|rlimit-as|rlimit-cpu|rlimit-fsize|rlimit-nofile|rlimit-nproc|rlimit-sigpending|timeout|tmpfs|veth-name|whitelist|xephyr-screen) / skipwhite contained
 " Generate list with: rg -o 'strn?cmp\(ptr, "([^ "]*[^ ])"' -r '$1' src/firejail/profile.c | grep -vEx '(include|rlimit|quiet)' | sed -e 's/\./\\./' | sort -u | tr $'\n' '|' # include/rlimit are false positives, quiet is special-cased below
-syn match fjCommand /\v(allow-debuggers|allusers|apparmor|caps|deterministic-exit-code|deterministic-shutdown|disable-mnt|ipc-namespace|keep-config-pulse|keep-dev-shm|keep-var-tmp|machine-id|memory-deny-write-execute|netfilter|no3d|noautopulse|nodbus|nodvd|nogroups|noinput|nonewprivs|noprinters|noroot|nosound|notv|nou2f|novideo|overlay|overlay-tmpfs|private|private-cache|private-cwd|private-dev|private-lib|private-tmp|seccomp|seccomp\.32|seccomp\.block-secondary|tracelog|writable-etc|writable-run-user|writable-var|writable-var-log|x11)$/ contained
+syn match fjCommand /\v(allow-debuggers|allusers|apparmor|caps|deterministic-exit-code|deterministic-shutdown|disable-mnt|ipc-namespace|keep-config-pulse|keep-dev-shm|keep-fd|keep-var-tmp|machine-id|memory-deny-write-execute|netfilter|no3d|noautopulse|nodbus|nodvd|nogroups|noinput|nonewprivs|noprinters|noroot|nosound|notv|nou2f|novideo|overlay|overlay-tmpfs|private|private-cache|private-cwd|private-dev|private-lib|private-tmp|seccomp|seccomp\.32|seccomp\.block-secondary|tracelog|writable-etc|writable-run-user|writable-var|writable-var-log|x11)$/ contained
 syn match fjCommand /ignore / nextgroup=fjCommand,fjCommandNoCond skipwhite contained
 syn match fjCommand /caps\.drop / nextgroup=fjCapability,fjAll skipwhite contained
 syn match fjCommand /caps\.keep / nextgroup=fjCapability skipwhite contained

src/firejail/dbus.c

@@ -298,10 +298,10 @@ void dbus_proxy_start(void) {
  errExit("fork");
  if (dbus_proxy_pid == 0) {
  // close open files
- int keep_list[2];
- keep_list[0] = status_pipe[1];
- keep_list[1] = args_pipe[0];
- close_all(keep_list, ARRAY_SIZE(keep_list));
+ int keep[2];
+ keep[0] = status_pipe[1];
+ keep[1] = args_pipe[0];
+ close_all(keep, ARRAY_SIZE(keep));
 
  if (arg_dbus_log_file != NULL) {
  int output_fd = creat(arg_dbus_log_file, 0666);

src/firejail/firejail.h

@@ -161,6 +161,7 @@ typedef struct config_t {
 
 #define MAX_PROFILE_IGNORE 32
  char *profile_ignore[MAX_PROFILE_IGNORE];
+ char *keep_fd; // inherit file descriptors to sandbox
  char *chrootdir; // chroot directory
  char *home_private; // private home directory
  char *home_private_keep; // keep list for private home directory
@@ -352,6 +353,7 @@ extern int arg_nou2f; // --nou2f
 extern int arg_noinput; // --noinput
 extern int arg_deterministic_exit_code; // always exit with first child's exit status
 extern int arg_deterministic_shutdown; // shut down the sandbox if first child dies
+extern int arg_keep_fd_all; // inherit all file descriptors to sandbox
 
 typedef enum {
  DBUS_POLICY_ALLOW, // Allow unrestricted access to the bus

src/firejail/join.c

@@ -569,11 +569,6 @@ void join(pid_t pid, int argc, char **argv, int index) {
  dbus_set_system_bus_env();
 #endif
 
- // set nice and rlimits
- if (arg_nice)
- set_nice(cfg.nice);
- set_rlimits();
-
  start_application(0, shfd, NULL);
 
  __builtin_unreachable();

src/firejail/main.c

@@ -149,6 +149,7 @@ int arg_nou2f = 0; // --nou2f
 int arg_noinput = 0; // --noinput
 int arg_deterministic_exit_code = 0; // always exit with first child's exit status
 int arg_deterministic_shutdown = 0; // shut down the sandbox if first child dies
+int arg_keep_fd_all = 0; // inherit all file descriptors to sandbox
 DbusPolicy arg_dbus_user = DBUS_POLICY_ALLOW; // --dbus-user
 DbusPolicy arg_dbus_system = DBUS_POLICY_ALLOW; // --dbus-system
 const char *arg_dbus_log_file = NULL;
@@ -1862,6 +1863,14 @@ int main(int argc, char **argv, char **envp) {
  }
  profile_add_ignore(argv[i] + 9);
  }
+ else if (strncmp(argv[i], "--keep-fd=", 10) == 0) {
+ if (strcmp(argv[i] + 10, "all") == 0)
+ arg_keep_fd_all = 1;
+ else {
+ const char *add = argv[i] + 10;
+ profile_list_augment(&cfg.keep_fd, add);
+ }
+ }
 #ifdef HAVE_CHROOT
  else if (strncmp(argv[i], "--chroot=", 9) == 0) {
  if (checkcfg(CFG_CHROOT)) {

src/firejail/profile.c

@@ -290,6 +290,15 @@ int profile_check_line(char *ptr, int lineno, const char *fname) {
  return 0;
  }
 
+ if (strncmp(ptr, "keep-fd ", 8) == 0) {
+ if (strcmp(ptr + 8, "all") == 0)
+ arg_keep_fd_all = 1;
+ else {
+ const char *add = ptr + 8;
+ profile_list_augment(&cfg.keep_fd, add);
+ }
+ return 0;
+ }
  if (strncmp(ptr, "xephyr-screen ", 14) == 0) {
 #ifdef HAVE_X11
  if (checkcfg(CFG_X11)) {

src/firejail/sandbox.c

@@ -399,12 +399,28 @@ static int monitor_application(pid_t app_pid) {
  return arg_deterministic_exit_code ? app_status : status;
 }
 
+
 static void print_time(void) {
  float delta = timetrace_end();
  fmessage("Child process initialized in %.02f ms\n", delta);
 }
 
 
+int *build_keep_fd_array(size_t *sz) {
+ if (!cfg.keep_fd) {
+ *sz = 0;
+ return NULL;
+ }
+
+ int *rv = str_to_int_array(cfg.keep_fd, sz);
+ if (!rv) {
+ fprintf(stderr, "Error: invalid keep-fd option\n");
+ exit(1);
+ }
+ return rv;
+}
+
+
 // check execute permissions for the program
 // this is done typically by the shell
 // we are here because of --shell=none
@@ -461,10 +477,27 @@ static int ok_to_run(const char *program) {
  return 0;
 }
 
+
 void start_application(int no_sandbox, int fd, char *set_sandbox_status) {
- // set environment
- if (no_sandbox == 0)
+ if (no_sandbox == 0) {
+ // don't leak open file descriptors
+ if (!arg_keep_fd_all) {
+ size_t sz;
+ int *keep = build_keep_fd_array(&sz);
+ close_all(keep, sz);
+ if (keep)
+ free(keep);
+ }
+
+ // set nice and rlimits
+ if (arg_nice)
+ set_nice(cfg.nice);
+ set_rlimits();
+
  env_defaults();
+ }
+
+ // set environment
  env_apply_all();
 
  // restore original umask
@@ -1252,12 +1285,6 @@ int sandbox(void* sandbox_arg) {
 #ifdef HAVE_APPARMOR
  set_apparmor();
 #endif
-
- // set nice and rlimits
- if (arg_nice)
- set_nice(cfg.nice);
- set_rlimits();
-
  start_application(0, -1, set_sandbox_status);
  }
 

src/firejail/usage.c

@@ -119,6 +119,7 @@ static char *usage_str =
  " --join-or-start=name|pid - join the sandbox or start a new one.\n"
  " --keep-config-pulse - disable automatic ~/.config/pulse init.\n"
  " --keep-dev-shm - /dev/shm directory is untouched (even with --private-dev).\n"
+ " --keep-fd - inherit open file descriptors to sandbox.\n"
  " --keep-var-tmp - /var/tmp directory is untouched.\n"
  " --list - list all sandboxes.\n"
 #ifdef HAVE_FILE_TRANSFER

src/include/common.h

@@ -142,4 +142,5 @@ int pid_proc_cmdline_x11_xpra_xephyr(const pid_t pid);
 int pid_hidepid(void);
 void warn_dumpable(void);
 const char *gnu_basename(const char *path);
+int *str_to_int_array(const char *str, size_t *sz);
 #endif

src/lib/common.c

@@ -31,6 +31,7 @@
 #include <dirent.h>
 #include <string.h>
 #include <time.h>
+#include <limits.h>
 #include "../include/common.h"
 #define BUFLEN 4096
 
@@ -320,6 +321,55 @@ const char *gnu_basename(const char *path) {
  return last_slash+1;
 }
 
+// takes string with comma separated int values, returns int array
+int *str_to_int_array(const char *str, size_t *sz) {
+ assert(str && sz);
+
+ size_t curr_sz = 0;
+ size_t arr_sz = 16;
+ int *rv = malloc(arr_sz * sizeof(int));
+ if (!rv)
+ errExit("malloc");
+
+ char *dup = strdup(str);
+ if (!dup)
+ errExit("strdup");
+ char *tok = strtok(dup, ",");
+ if (!tok) {
+ free(dup);
+ free(rv);
+ goto errout;
+ }
+
+ while (tok) {
+ char *end;
+ long val = strtol(tok, &end, 10);
+ if (end == tok || *end != '\0' || val < INT_MIN || val > INT_MAX) {
+ free(dup);
+ free(rv);
+ goto errout;
+ }
+
+ if (curr_sz == arr_sz) {
+ arr_sz *= 2;
+ rv = realloc(rv, arr_sz * sizeof(int));
+ if (!rv)
+ errExit("realloc");
+ }
+ rv[curr_sz++] = val;
+
+ tok = strtok(NULL, ",");
+ }
+ free(dup);
+
+ *sz = curr_sz;
+ return rv;
+
+errout:
+ *sz = 0;
+ return NULL;
+}
+
 //**************************
 // time trace based on getticks function
 //**************************

src/man/firejail-profile.txt

@@ -724,6 +724,11 @@ env CFLAGS="-W -Wall -Werror"
 .TP
 \fBipc-namespace
 Enable IPC namespace.
+
+.TP
+\fBkeep-fd
+Inherit open file descriptors to sandbox.
+
 .TP
 \fBname sandboxname
 Set sandbox name. Example:

src/man/firejail.txt

@@ -1103,6 +1103,26 @@ Example:
 .br
 $ firejail --keep-dev-shm --private-dev
 
+.TP
+\fB\-\-keep-fd=all
+Inherit all open file descriptors to the sandbox. By default only file descriptors 0, 1 and 2 are inherited to the sandbox, and all other file descriptors are closed.
+.br
+
+.br
+Example:
+.br
+$ firejail --keep-fd=all
+
+.TP
+\fB\-\-keep-fd=file_descriptor
+Don't close specified open file descriptors. By default only file descriptors 0, 1 and 2 are inherited to the sandbox, and all other file descriptors are closed.
+.br
+
+.br
+Example:
+.br
+$ firejail --keep-fd=3,4,5
+
 .TP
 \fB\-\-keep-var-tmp
 /var/tmp directory is untouched.

src/zsh_completion/_firejail.in

@@ -104,6 +104,7 @@ _firejail_args=(
  '--join-or-start=-[join the sandbox or start a new one name|pid]: :_all_firejails'
  '--keep-config-pulse[disable automatic ~/.config/pulse init]'
  '--keep-dev-shm[/dev/shm directory is untouched (even with --private-dev)]'
+ '--keep-fd[inherit open file descriptors to sandbox]'
  '--keep-var-tmp[/var/tmp directory is untouched]'
  '--machine-id[spoof /etc/machine-id with a random id]'
  '--memory-deny-write-execute[seccomp filter to block attempts to create memory mappings that are both writable and executable]'