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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-14 19:33:32 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-14 19:33:32 +0000 |
commit | 8bb05ac73a5b448b339ce0bc8d396c82c459b47f (patch) | |
tree | 1fdda006866bca20d41cb206767ea5241e36852f /misc-utils/enosys.c | |
parent | Adding debian version 2.39.3-11. (diff) | |
download | util-linux-8bb05ac73a5b448b339ce0bc8d396c82c459b47f.tar.xz util-linux-8bb05ac73a5b448b339ce0bc8d396c82c459b47f.zip |
Merging upstream version 2.40.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'misc-utils/enosys.c')
-rw-r--r-- | misc-utils/enosys.c | 266 |
1 files changed, 266 insertions, 0 deletions
diff --git a/misc-utils/enosys.c b/misc-utils/enosys.c new file mode 100644 index 0000000..22096df --- /dev/null +++ b/misc-utils/enosys.c @@ -0,0 +1,266 @@ +/* + * Copyright (C) 2023 Thomas Weißschuh <thomas@t-8ch.de> + * + * 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 would 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 <stddef.h> +#include <stdbool.h> +#include <getopt.h> + +#include <linux/unistd.h> +#include <linux/filter.h> +#include <linux/seccomp.h> +#include <linux/audit.h> +#include <sys/prctl.h> +#include <sys/syscall.h> +#include <sys/ioctl.h> + +#include "c.h" +#include "exitcodes.h" +#include "nls.h" +#include "bitops.h" +#include "audit-arch.h" +#include "list.h" +#include "xalloc.h" +#include "strutils.h" + +#define IS_LITTLE_ENDIAN (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__) + +#define syscall_nr (offsetof(struct seccomp_data, nr)) +#define syscall_arch (offsetof(struct seccomp_data, arch)) +#define _syscall_arg(n) (offsetof(struct seccomp_data, args[n])) +#define syscall_arg_lower32(n) (_syscall_arg(n) + 4 * !IS_LITTLE_ENDIAN) +#define syscall_arg_upper32(n) (_syscall_arg(n) + 4 * IS_LITTLE_ENDIAN) + +static int set_seccomp_filter(const void *prog) +{ +#if defined(__NR_seccomp) && defined(SECCOMP_SET_MODE_FILTER) && defined(SECCOMP_FILTER_FLAG_SPEC_ALLOW) + if (!syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, SECCOMP_FILTER_FLAG_SPEC_ALLOW, prog)) + return 0; +#endif + + return prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, prog); +} + +struct syscall { + const char *const name; + long number; +}; + +/* When the alias arrays are empty the compiler emits -Wtype-limits warnings. + * Avoid those by going through this function. */ +static inline bool lt(size_t a, size_t b) +{ + return a < b; +} + +static const struct syscall syscalls[] = { +#define UL_SYSCALL(name, nr) { name, nr }, +#include "syscalls.h" +#undef UL_SYSCALL +}; + +static const struct syscall ioctls[] = { + { "FIOCLEX", FIOCLEX }, +}; + +static void __attribute__((__noreturn__)) usage(void) +{ + FILE *out = stdout; + + fputs(USAGE_HEADER, out); + fprintf(out, _(" %s [options] -- <command>\n"), program_invocation_short_name); + + fputs(USAGE_OPTIONS, out); + fputs(_(" -s, --syscall syscall to block\n"), out); + fputs(_(" -i, --ioctl ioctl to block\n"), out); + fputs(_(" -l, --list list known syscalls\n"), out); + + fputs(USAGE_SEPARATOR, out); + fprintf(out, USAGE_HELP_OPTIONS(25)); + + fprintf(out, USAGE_MAN_TAIL("enosys(1)")); + + exit(EXIT_SUCCESS); +} + +struct blocked_number { + struct list_head head; + long number; +}; + +int main(int argc, char **argv) +{ + int c; + size_t i; + bool found; + static const struct option longopts[] = { + { "syscall", required_argument, NULL, 's' }, + { "ioctl", required_argument, NULL, 'i' }, + { "list", no_argument, NULL, 'l' }, + { "list-ioctl", no_argument, NULL, 'm' }, + { "version", no_argument, NULL, 'V' }, + { "help", no_argument, NULL, 'h' }, + { 0 } + }; + + long blocked_number; + struct blocked_number *blocked; + struct list_head *loop_ctr; + struct list_head blocked_syscalls; + bool blocking_execve = false; + INIT_LIST_HEAD(&blocked_syscalls); + struct list_head blocked_ioctls; + INIT_LIST_HEAD(&blocked_ioctls); + + setlocale(LC_ALL, ""); + bindtextdomain(PACKAGE, LOCALEDIR); + textdomain(PACKAGE); + + while ((c = getopt_long (argc, argv, "+Vhs:i:lm", longopts, NULL)) != -1) { + switch (c) { + case 's': + found = 0; + for (i = 0; lt(i, ARRAY_SIZE(syscalls)); i++) { + if (strcmp(optarg, syscalls[i].name) == 0) { + blocked_number = syscalls[i].number; + found = 1; + break; + } + } + if (!found) + blocked_number = str2num_or_err( + optarg, 10, _("Unknown syscall"), 0, LONG_MAX); + + blocked = xmalloc(sizeof(*blocked)); + blocked->number = blocked_number; + list_add(&blocked->head, &blocked_syscalls); + if (blocked_number == __NR_execve) + blocking_execve = true; + + break; + case 'i': + found = 0; + for (i = 0; lt(i, ARRAY_SIZE(ioctls)); i++) { + if (strcmp(optarg, ioctls[i].name) == 0) { + blocked_number = ioctls[i].number; + found = 1; + break; + } + } + if (!found) + blocked_number = str2num_or_err( + optarg, 10, _("Unknown ioctl"), 0, LONG_MAX); + + blocked = xmalloc(sizeof(*blocked)); + blocked->number = blocked_number; + list_add(&blocked->head, &blocked_ioctls); + + break; + case 'l': + for (i = 0; lt(i, ARRAY_SIZE(syscalls)); i++) + printf("%5ld %s\n", syscalls[i].number, syscalls[i].name); + return EXIT_SUCCESS; + case 'm': + for (i = 0; lt(i, ARRAY_SIZE(ioctls)); i++) + printf("%5ld %s\n", ioctls[i].number, ioctls[i].name); + return EXIT_SUCCESS; + case 'V': + print_version(EXIT_SUCCESS); + case 'h': + usage(); + default: + errtryhelp(EXIT_FAILURE); + } + } + + if (optind >= argc) + errtryhelp(EXIT_FAILURE); + + struct sock_filter filter[BPF_MAXINSNS]; + struct sock_filter *f = filter; + +#define INSTR(_instruction) \ + if (f == &filter[ARRAY_SIZE(filter)]) \ + errx(EXIT_FAILURE, _("filter too big")); \ + *f++ = (struct sock_filter) _instruction + + INSTR(BPF_STMT(BPF_LD | BPF_W | BPF_ABS, syscall_arch)); + INSTR(BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, SECCOMP_ARCH_NATIVE, 1, 0)); + INSTR(BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_TRAP)); + + /* Blocking "execve" normally would also block our own call to + * it and the end of main. To distinguish between our execve + * and the execve to be blocked, compare the environ pointer. + * + * See https://lore.kernel.org/all/CAAnLoWnS74dK9Wq4EQ-uzQ0qCRfSK-dLqh+HCais-5qwDjrVzg@mail.gmail.com/ + */ + if (blocking_execve) { + INSTR(BPF_STMT(BPF_LD | BPF_W | BPF_ABS, syscall_nr)); + INSTR(BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_execve, 0, 5)); + INSTR(BPF_STMT(BPF_LD | BPF_W | BPF_ABS, syscall_arg_lower32(2))); + INSTR(BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, (uint64_t)(uintptr_t) environ, 0, 3)); + INSTR(BPF_STMT(BPF_LD | BPF_W | BPF_ABS, syscall_arg_upper32(2))); + INSTR(BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, (uint64_t)(uintptr_t) environ >> 32, 0, 1)); + INSTR(BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW)); + } + + INSTR(BPF_STMT(BPF_LD | BPF_W | BPF_ABS, syscall_nr)); + + list_for_each(loop_ctr, &blocked_syscalls) { + blocked = list_entry(loop_ctr, struct blocked_number, head); + + INSTR(BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, blocked->number, 0, 1)); + INSTR(BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ERRNO | ENOSYS)); + } + + if (!list_empty(&blocked_ioctls)) { + INSTR(BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_ioctl, 1, 0)); + INSTR(BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW)); + + list_for_each(loop_ctr, &blocked_ioctls) { + blocked = list_entry(loop_ctr, struct blocked_number, head); + + INSTR(BPF_STMT(BPF_LD | BPF_W | BPF_ABS, syscall_arg_lower32(1))); + INSTR(BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, (uint64_t) blocked->number, 0, 3)); + INSTR(BPF_STMT(BPF_LD | BPF_W | BPF_ABS, syscall_arg_upper32(1))); + INSTR(BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, (uint64_t) blocked->number >> 32, 0, 1)); + INSTR(BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ERRNO | ENOTTY)); + } + } + + INSTR(BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW)); + + struct sock_fprog prog = { + .len = f - filter, + .filter = filter, + }; + + /* *SET* below will return EINVAL when either the filter is invalid or + * seccomp is not supported. To distinguish those cases do a *GET* here + */ + if (prctl(PR_GET_SECCOMP) == -1 && errno == EINVAL) + err(EXIT_NOTSUPP, _("Seccomp non-functional")); + + if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) + err_nosys(EXIT_FAILURE, _("Could not run prctl(PR_SET_NO_NEW_PRIVS)")); + + if (set_seccomp_filter(&prog)) + err_nosys(EXIT_FAILURE, _("Could not seccomp filter")); + + if (execvp(argv[optind], argv + optind)) + err(EXIT_NOTSUPP, _("Could not exec")); +} |