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/*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice immediately at the beginning of the file, without modification,
* this list of conditions, and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* libseccomp hooks.
*/
#include "file.h"
#ifndef lint
FILE_RCSID("@(#)$File: seccomp.c,v 1.24 2022/09/24 20:30:13 christos Exp $")
#endif /* lint */
#if HAVE_LIBSECCOMP
#include <seccomp.h> /* libseccomp */
#include <sys/prctl.h> /* prctl */
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <termios.h>
#include <fcntl.h>
#include <stdlib.h>
#include <errno.h>
#define DENY_RULE(call) \
do \
if (seccomp_rule_add (ctx, SCMP_ACT_KILL, SCMP_SYS(call), 0) == -1) \
goto out; \
while (/*CONSTCOND*/0)
#define ALLOW_RULE(call) \
do \
if (seccomp_rule_add (ctx, SCMP_ACT_ALLOW, SCMP_SYS(call), 0) == -1) \
goto out; \
while (/*CONSTCOND*/0)
#define ALLOW_IOCTL_RULE(param) \
do \
if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(ioctl), 1, \
SCMP_CMP(1, SCMP_CMP_EQ, (scmp_datum_t)param, \
(scmp_datum_t)0)) == -1) \
goto out; \
while (/*CONSTCOND*/0)
static scmp_filter_ctx ctx;
int
enable_sandbox_basic(void)
{
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1)
return -1;
if (prctl(PR_SET_DUMPABLE, 0, 0, 0, 0) == -1)
return -1;
// initialize the filter
ctx = seccomp_init(SCMP_ACT_ALLOW);
if (ctx == NULL)
return 1;
DENY_RULE(_sysctl);
DENY_RULE(acct);
DENY_RULE(add_key);
DENY_RULE(adjtimex);
DENY_RULE(chroot);
DENY_RULE(clock_adjtime);
DENY_RULE(create_module);
DENY_RULE(delete_module);
DENY_RULE(fanotify_init);
DENY_RULE(finit_module);
DENY_RULE(get_kernel_syms);
DENY_RULE(get_mempolicy);
DENY_RULE(init_module);
DENY_RULE(io_cancel);
DENY_RULE(io_destroy);
DENY_RULE(io_getevents);
DENY_RULE(io_setup);
DENY_RULE(io_submit);
DENY_RULE(ioperm);
DENY_RULE(iopl);
DENY_RULE(ioprio_set);
DENY_RULE(kcmp);
#ifdef __NR_kexec_file_load
DENY_RULE(kexec_file_load);
#endif
DENY_RULE(kexec_load);
DENY_RULE(keyctl);
DENY_RULE(lookup_dcookie);
DENY_RULE(mbind);
DENY_RULE(nfsservctl);
DENY_RULE(migrate_pages);
DENY_RULE(modify_ldt);
DENY_RULE(mount);
DENY_RULE(move_pages);
DENY_RULE(name_to_handle_at);
DENY_RULE(open_by_handle_at);
DENY_RULE(perf_event_open);
DENY_RULE(pivot_root);
DENY_RULE(process_vm_readv);
DENY_RULE(process_vm_writev);
DENY_RULE(ptrace);
DENY_RULE(reboot);
DENY_RULE(remap_file_pages);
DENY_RULE(request_key);
DENY_RULE(set_mempolicy);
DENY_RULE(swapoff);
DENY_RULE(swapon);
DENY_RULE(sysfs);
DENY_RULE(syslog);
DENY_RULE(tuxcall);
DENY_RULE(umount2);
DENY_RULE(uselib);
DENY_RULE(vmsplice);
// blocking dangerous syscalls that file should not need
DENY_RULE (execve);
DENY_RULE (socket);
// ...
// applying filter...
if (seccomp_load (ctx) == -1)
goto out;
// free ctx after the filter has been loaded into the kernel
seccomp_release(ctx);
return 0;
out:
seccomp_release(ctx);
return -1;
}
int
enable_sandbox_full(void)
{
// prevent child processes from getting more priv e.g. via setuid,
// capabilities, ...
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1)
return -1;
if (prctl(PR_SET_DUMPABLE, 0, 0, 0, 0) == -1)
return -1;
// initialize the filter
ctx = seccomp_init(SCMP_ACT_KILL);
if (ctx == NULL)
return -1;
ALLOW_RULE(access);
ALLOW_RULE(brk);
ALLOW_RULE(close);
ALLOW_RULE(dup2);
ALLOW_RULE(exit);
ALLOW_RULE(exit_group);
#ifdef __NR_faccessat
ALLOW_RULE(faccessat);
#endif
ALLOW_RULE(fcntl);
ALLOW_RULE(fcntl64);
#ifdef __NR_fstat
ALLOW_RULE(fstat);
#endif
ALLOW_RULE(fstat64);
#ifdef __NR_fstatat64
ALLOW_RULE(fstatat64);
#endif
ALLOW_RULE(futex);
ALLOW_RULE(getdents);
#ifdef __NR_getdents64
ALLOW_RULE(getdents64);
#endif
#ifdef FIONREAD
// called in src/compress.c under sread
ALLOW_IOCTL_RULE(FIONREAD);
#endif
#ifdef TIOCGWINSZ
// musl libc may call ioctl TIOCGWINSZ on stdout
ALLOW_IOCTL_RULE(TIOCGWINSZ);
#endif
#ifdef TCGETS
// glibc may call ioctl TCGETS on stdout on physical terminal
ALLOW_IOCTL_RULE(TCGETS);
#endif
ALLOW_RULE(lseek);
ALLOW_RULE(_llseek);
ALLOW_RULE(lstat);
ALLOW_RULE(lstat64);
ALLOW_RULE(madvise);
ALLOW_RULE(mmap);
ALLOW_RULE(mmap2);
ALLOW_RULE(mprotect);
ALLOW_RULE(mremap);
ALLOW_RULE(munmap);
#ifdef __NR_newfstatat
ALLOW_RULE(newfstatat);
#endif
ALLOW_RULE(open);
ALLOW_RULE(openat);
ALLOW_RULE(pread64);
ALLOW_RULE(read);
ALLOW_RULE(readlink);
#ifdef __NR_readlinkat
ALLOW_RULE(readlinkat);
#endif
ALLOW_RULE(rt_sigaction);
ALLOW_RULE(rt_sigprocmask);
ALLOW_RULE(rt_sigreturn);
ALLOW_RULE(select);
ALLOW_RULE(stat);
ALLOW_RULE(statx);
ALLOW_RULE(stat64);
ALLOW_RULE(sysinfo);
ALLOW_RULE(umask); // Used in file_pipe2file()
ALLOW_RULE(getpid); // Used by glibc in file_pipe2file()
ALLOW_RULE(unlink);
ALLOW_RULE(write);
ALLOW_RULE(writev);
#if 0
// needed by valgrind
ALLOW_RULE(gettid);
ALLOW_RULE(rt_sigtimedwait);
#endif
#if 0
/* special restrictions for socket, only allow AF_UNIX/AF_LOCAL */
if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 1,
SCMP_CMP(0, SCMP_CMP_EQ, AF_UNIX)) == -1)
goto out;
if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 1,
SCMP_CMP(0, SCMP_CMP_EQ, AF_LOCAL)) == -1)
goto out;
/* special restrictions for open, prevent opening files for writing */
if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(open), 1,
SCMP_CMP(1, SCMP_CMP_MASKED_EQ, O_WRONLY | O_RDWR, 0)) == -1)
goto out;
if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EACCES), SCMP_SYS(open), 1,
SCMP_CMP(1, SCMP_CMP_MASKED_EQ, O_WRONLY, O_WRONLY)) == -1)
goto out;
if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EACCES), SCMP_SYS(open), 1,
SCMP_CMP(1, SCMP_CMP_MASKED_EQ, O_RDWR, O_RDWR)) == -1)
goto out;
/* allow stderr */
if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(write), 1,
SCMP_CMP(0, SCMP_CMP_EQ, 2)) == -1)
goto out;
#endif
// applying filter...
if (seccomp_load(ctx) == -1)
goto out;
// free ctx after the filter has been loaded into the kernel
seccomp_release(ctx);
return 0;
out:
// something went wrong
seccomp_release(ctx);
return -1;
}
#endif
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