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Diffstat (limited to '')
| -rw-r--r-- | src/seccomp.c | 290 |
1 files changed, 290 insertions, 0 deletions
diff --git a/src/seccomp.c b/src/seccomp.c new file mode 100644 index 0000000..87d4c49 --- /dev/null +++ b/src/seccomp.c @@ -0,0 +1,290 @@ +/* + * 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 1.25 2022/12/26 18:57:29 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(utimes); + 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 |