mirror of https://github.com/msantos/xmppipe
sandbox: Linux seccomp syscall filter
Add a BPF seccomp syscall filter on Linux. Not enabled by default. To
compile:
XMPPIPE_SANDBOX=XMPPIPE_SANDBOX_SECCOMP make
The sandbox is derived from OpenSSH's seccomp sandbox by Will Drewry and
Kees Cook's tutorial on seccomp:
http://outflux.net/teach-seccomp/
pull/1/head
Michael Santos
7 years ago
parent
c346c863e4
commit
5917d03137
@ -0,0 +1,169 @@
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/* Copyright (c) 2017, Michael Santos <michael.santos@gmail.com>
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#ifdef XMPPIPE_SANDBOX_SECCOMP
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#include <stddef.h>
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#include <errno.h>
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#include <linux/unistd.h>
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#include <linux/audit.h>
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#include <linux/filter.h>
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#include <sys/prctl.h>
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#include <linux/seccomp.h>
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#include "xmppipe.h"
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/* macros from openssh-7.2/sandbox-seccomp-filter.c */
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/* Linux seccomp_filter sandbox */
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#define SECCOMP_FILTER_FAIL SECCOMP_RET_KILL
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/* Use a signal handler to emit violations when debugging */
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#ifdef SANDBOX_SECCOMP_FILTER_DEBUG
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# undef SECCOMP_FILTER_FAIL
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# define SECCOMP_FILTER_FAIL SECCOMP_RET_TRAP
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#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */
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/* Simple helpers to avoid manual errors (but larger BPF programs). */
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#define SC_DENY(_nr, _errno) \
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BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_ ## _nr, 0, 1), \
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BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ERRNO|(_errno))
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#define SC_ALLOW(_nr) \
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BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_ ## _nr, 0, 1), \
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BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW)
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#define SC_ALLOW_ARG(_nr, _arg_nr, _arg_val) \
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BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_ ## _nr, 0, 4), \
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/* load first syscall argument */ \
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BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
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offsetof(struct seccomp_data, args[(_arg_nr)])), \
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BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_arg_val), 0, 1), \
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BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW), \
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/* reload syscall number; all rules expect it in accumulator */ \
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BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
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offsetof(struct seccomp_data, nr))
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/*
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* http://outflux.net/teach-seccomp/
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* https://github.com/gebi/teach-seccomp
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*
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*/
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#define syscall_nr (offsetof(struct seccomp_data, nr))
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#define arch_nr (offsetof(struct seccomp_data, arch))
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#if defined(__i386__)
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# define SECCOMP_AUDIT_ARCH AUDIT_ARCH_I386
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#elif defined(__x86_64__)
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# define SECCOMP_AUDIT_ARCH AUDIT_ARCH_X86_64
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#elif defined(__arm__)
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# define SECCOMP_AUDIT_ARCH AUDIT_ARCH_ARM
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#elif defined(__aarch64__)
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# define SECCOMP_AUDIT_ARCH AUDIT_ARCH_AARCH64
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#else
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# warning "seccomp: unsupported platform"
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# define SECCOMP_AUDIT_ARCH 0
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#endif
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int
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xmppipe_sandbox_init(xmppipe_state_t *state)
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{
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struct sock_filter filter[] = {
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/* Ensure the syscall arch convention is as expected. */
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BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
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offsetof(struct seccomp_data, arch)),
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BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, SECCOMP_AUDIT_ARCH, 1, 0),
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BPF_STMT(BPF_RET+BPF_K, SECCOMP_FILTER_FAIL),
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/* Load the syscall number for checking. */
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BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
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offsetof(struct seccomp_data, nr)),
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/* Syscalls to non-fatally deny */
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#ifdef __NR_open
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SC_DENY(open, EACCES),
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#endif
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/* Syscalls to allow */
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#ifdef __NR_brk
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SC_ALLOW(brk),
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#endif
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#ifdef __NR_clock_gettime
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SC_ALLOW(clock_gettime),
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#endif
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#ifdef __NR_exit_group
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SC_ALLOW(exit_group),
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#endif
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#ifdef __NR_fcntl
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SC_ALLOW(fcntl),
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#endif
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#ifdef __NR_fcntl64
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SC_ALLOW(fcntl64),
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#endif
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#ifdef __NR_fstat
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SC_ALLOW(fstat),
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#endif
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#ifdef __NR_fstat64
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SC_ALLOW(fstat64),
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#endif
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#ifdef __NR_getppid
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SC_ALLOW(getppid),
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#endif
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#ifdef __NR_gettid
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SC_ALLOW(gettid),
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#endif
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#ifdef __NR_gettimeofday
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SC_ALLOW(gettimeofday),
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#endif
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#ifdef __NR_getuid32
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SC_ALLOW(getuid32),
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#endif
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#ifdef __NR_ioctl
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SC_ALLOW(ioctl),
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#endif
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#ifdef __NR_poll
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SC_ALLOW(poll),
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#endif
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#ifdef __NR_read
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SC_ALLOW(read),
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#endif
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#ifdef __NR__newselect
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SC_ALLOW(_newselect),
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#endif
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#ifdef __NR_select
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SC_ALLOW(select),
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#endif
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#ifdef __NR_stat64
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SC_ALLOW(stat64),
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#endif
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#ifdef __NR_write
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SC_ALLOW(write),
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#endif
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/* Default deny */
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BPF_STMT(BPF_RET+BPF_K, SECCOMP_FILTER_FAIL)
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};
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struct sock_fprog prog = {
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.len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
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.filter = filter,
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};
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if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) < 0)
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return -1;
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if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog))
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return -1;
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return 0;
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}
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#endif
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