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/*
* Copyright (C) 2014-2020 Firejail Authors
*
* This file is part of firejail project
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "fseccomp.h"
#include "../include/seccomp.h"
#include <sys/personality.h>
#include <sys/syscall.h>
static void write_filter(const char *fname, size_t size, const void *filter) {
// save filter to file
int dst = open(fname, O_CREAT|O_WRONLY|O_TRUNC, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
if (dst < 0) {
fprintf(stderr, "Error fseccomp: cannot open %s file\n", fname);
exit(1);
}
size_t written = 0;
while (written < size) {
ssize_t rv = write(dst, (unsigned char *) filter + written, size - written);
if (rv == -1) {
fprintf(stderr, "Error fseccomp: cannot write %s file\n", fname);
exit(1);
}
written += rv;
}
close(dst);
}
// 32 bit arch filter installed on 64 bit architectures
void seccomp_secondary_32(const char *fname) {
// hardcoded syscall values
struct sock_filter filter[] = {
VALIDATE_ARCHITECTURE_32,
EXAMINE_SYSCALL,
BLACKLIST(21), // mount
BLACKLIST(52), // umount2
// todo: implement --allow-debuggers
BLACKLIST(26), // ptrace
BLACKLIST(283), // kexec_load
BLACKLIST(341), // name_to_handle_at
BLACKLIST(342), // open_by_handle_at
BLACKLIST(127), // create_module
BLACKLIST(128), // init_module
BLACKLIST(350), // finit_module
BLACKLIST(129), // delete_module
BLACKLIST(110), // iopl
BLACKLIST(101), // ioperm
BLACKLIST(289), // ioprio_set
BLACKLIST(87), // swapon
BLACKLIST(115), // swapoff
BLACKLIST(103), // syslog
BLACKLIST(347), // process_vm_readv
BLACKLIST(348), // process_vm_writev
BLACKLIST(135), // sysfs
BLACKLIST(149), // _sysctl
BLACKLIST(124), // adjtimex
BLACKLIST(343), // clock_adjtime
BLACKLIST(253), // lookup_dcookie
BLACKLIST(336), // perf_event_open
BLACKLIST(338), // fanotify_init
BLACKLIST(349), // kcmp
BLACKLIST(286), // add_key
BLACKLIST(287), // request_key
BLACKLIST(288), // keyctl
BLACKLIST(86), // uselib
BLACKLIST(51), // acct
BLACKLIST(123), // modify_ldt
BLACKLIST(217), // pivot_root
BLACKLIST(245), // io_setup
BLACKLIST(246), // io_destroy
BLACKLIST(247), // io_getevents
BLACKLIST(248), // io_submit
BLACKLIST(249), // io_cancel
BLACKLIST(257), // remap_file_pages
BLACKLIST(274), // mbind
// breaking Firefox nightly when playing youtube videos
// TODO: test again when firefox sandbox is finally released
// BLACKLIST(275), // get_mempolicy
BLACKLIST(276), // set_mempolicy
BLACKLIST(294), // migrate_pages
BLACKLIST(317), // move_pages
BLACKLIST(316), // vmsplice
BLACKLIST(61), // chroot
BLACKLIST(88), // reboot
BLACKLIST(169), // nfsservctl
BLACKLIST(130), // get_kernel_syms
RETURN_ALLOW
};
// save filter to file
write_filter(fname, sizeof(filter), filter);
}
#define jmp_from_to(from_addr, to_addr) ((to_addr) - (from_addr) - 1)
#if __BYTE_ORDER == __BIG_ENDIAN
#define MSW 0
#define LSW (sizeof(int))
#else
#define MSW (sizeof(int))
#define LSW 0
#endif
void seccomp_secondary_block(const char *fname) {
struct sock_filter filter[] = {
// block other architectures
VALIDATE_ARCHITECTURE_KILL,
EXAMINE_SYSCALL,
#if defined(__x86_64__)
// block x32
HANDLE_X32_KILL,
#endif
// block personality(2) where domain != PER_LINUX or 0xffffffff (query current personality)
// 0: if personality(2), continue to 1, else goto 7 (allow)
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, SYS_personality, 0, jmp_from_to(0, 7)),
// 1: get LSW of system call argument 0
BPF_STMT(BPF_LD + BPF_W + BPF_ABS, (offsetof(struct seccomp_data, args[0])) + LSW),
// 2: if LSW(arg0) == PER_LINUX, goto step 4, else continue to 3
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, PER_LINUX, jmp_from_to(2, 4), 0),
// 3: if LSW(arg0) == 0xffffffff, continue to 4, else goto 6 (kill)
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0xffffffff, 0, jmp_from_to(3, 6)),
// 4: get MSW of system call argument 0
BPF_STMT(BPF_LD + BPF_W + BPF_ABS, (offsetof(struct seccomp_data, args[0])) + MSW),
// 5: if MSW(arg0) == 0, goto 7 (allow) else continue to 6 (kill)
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, jmp_from_to(5, 7), 0),
// 6:
KILL_PROCESS,
// 7:
RETURN_ALLOW
};
// save filter to file
write_filter(fname, sizeof(filter), filter);
}
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