mirror of
https://github.com/omar-polo/gmid.git
synced 2024-09-06 11:29:19 +02:00
this time targetting ABI level 3; partially based on how claudio@ handled it in rpki-client. Fun how this bit of code has come full circle (gmid inspired what I wrote for got, which inspired what was written for rpki-client, which has come back.)
286 lines
6.0 KiB
C
286 lines
6.0 KiB
C
/*
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* Copyright (c) 2021, 2023 Omar Polo <op@omarpolo.com>
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* Copyright (c) 2022 Claudio Jeker <claudio@openbsd.org>
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*
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* Permission to use, copy, modify, and 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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#include "gmid.h"
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#include "log.h"
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#if defined(__OpenBSD__)
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#include <unistd.h>
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void
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sandbox_main_process(void)
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{
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if (pledge("stdio rpath wpath cpath inet dns sendfd", NULL) == -1)
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fatal("pledge");
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}
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void
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sandbox_server_process(void)
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{
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if (pledge("stdio rpath inet unix dns recvfd", NULL) == -1)
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fatal("pledge");
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}
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void
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sandbox_crypto_process(void)
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{
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if (pledge("stdio recvfd", NULL) == -1)
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fatal("pledge");
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}
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void
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sandbox_logger_process(void)
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{
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if (pledge("stdio recvfd", NULL) == -1)
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fatal("pledge");
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}
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#elif HAVE_LANDLOCK
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#include <linux/landlock.h>
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#include <sys/prctl.h>
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#include <sys/syscall.h>
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#include <sys/types.h>
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#include <errno.h>
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/*
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* What's the deal with landlock? While distro with linux >= 5.13
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* have the struct declarations, libc wrappers are missing. The
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* sample landlock code provided by the authors includes these "shims"
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* in their example for the landlock API until libc provides them.
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*/
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#ifndef landlock_create_ruleset
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static inline int
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landlock_create_ruleset(const struct landlock_ruleset_attr *attr, size_t size,
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__u32 flags)
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{
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return syscall(__NR_landlock_create_ruleset, attr, size, flags);
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}
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#endif
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#ifndef landlock_add_rule
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static inline int
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landlock_add_rule(int ruleset_fd, enum landlock_rule_type type,
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const void *attr, __u32 flags)
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{
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return syscall(__NR_landlock_add_rule, ruleset_fd, type, attr, flags);
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}
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#endif
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#ifndef landlock_restrict_self
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static inline int
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landlock_restrict_self(int ruleset_fd, __u32 flags)
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{
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return syscall(__NR_landlock_restrict_self, ruleset_fd, flags);
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}
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#endif
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/*
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* Maybe we should ship with a full copy of the linux headers because
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* you never know...
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*/
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#ifndef LANDLOCK_ACCESS_FS_REFER
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#define LANDLOCK_ACCESS_FS_REFER (1ULL << 13)
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#endif
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#ifndef LANDLOCK_ACCESS_FS_TRUNCATE
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#define LANDLOCK_ACCESS_FS_TRUNCATE (1ULL << 14)
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#endif
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static int landlock_state;
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static int landlock_fd;
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/*
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* Initialize landlock, which is stupidly complicated.
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*/
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static int
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landlock_init(void)
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{
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struct landlock_ruleset_attr rattr = {
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/*
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* List all capabilities currently defined by landlock.
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* Failure in doing so will implicitly allow those actions
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* (i.e. omitting READ_FILE will allow to read _any_ file.)
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*/
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.handled_access_fs =
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LANDLOCK_ACCESS_FS_EXECUTE |
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LANDLOCK_ACCESS_FS_READ_FILE |
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LANDLOCK_ACCESS_FS_READ_DIR |
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LANDLOCK_ACCESS_FS_WRITE_FILE |
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LANDLOCK_ACCESS_FS_REMOVE_DIR |
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LANDLOCK_ACCESS_FS_REMOVE_FILE |
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LANDLOCK_ACCESS_FS_MAKE_CHAR |
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LANDLOCK_ACCESS_FS_MAKE_DIR |
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LANDLOCK_ACCESS_FS_MAKE_REG |
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LANDLOCK_ACCESS_FS_MAKE_SOCK |
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LANDLOCK_ACCESS_FS_MAKE_FIFO |
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LANDLOCK_ACCESS_FS_MAKE_BLOCK |
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LANDLOCK_ACCESS_FS_MAKE_SYM |
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LANDLOCK_ACCESS_FS_REFER |
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LANDLOCK_ACCESS_FS_TRUNCATE,
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};
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int fd, abi, saved_errno;
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if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1)
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return -1;
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abi = landlock_create_ruleset(NULL, 0, LANDLOCK_CREATE_RULESET_VERSION);
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if (abi == -1)
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return -1;
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if (abi < 2)
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rattr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_REFER;
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if (abi < 3)
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rattr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_TRUNCATE;
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landlock_state = 1;
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return landlock_create_ruleset(&rattr, sizeof(rattr), 0);
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}
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static int
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landlock_lock(void)
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{
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int saved_errno;
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if (landlock_restrict_self(landlock_fd, 0)) {
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saved_errno = errno;
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close(landlock_fd);
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errno = saved_errno;
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landlock_state = -1;
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return -1;
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}
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landlock_state = 2;
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close(landlock_fd);
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return 0;
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}
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static int
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landlock_unveil(const char *path, const char *permissions)
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{
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struct landlock_path_beneath_attr lpba;
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int fd, saved_errno;
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if (landlock_state == 0) {
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if ((landlock_fd = landlock_init()) == -1) {
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landlock_state = -1;
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/* this kernel doesn't have landlock built in */
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if (errno == ENOSYS || errno == EOPNOTSUPP)
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return 0;
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return -1;
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}
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}
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/* no landlock available */
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if (landlock_state == -1)
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return 0;
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if (path == NULL && permissions == NULL)
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return landlock_lock();
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if (path == NULL || permissions == NULL || landlock_state != 1) {
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errno = EINVAL;
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return -1;
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}
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if (!strcmp(permissions, "r")) {
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fd = open(path, O_PATH | O_CLOEXEC);
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if (fd == -1)
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return -1;
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lpba = (struct landlock_path_beneath_attr){
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.allowed_access =
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LANDLOCK_ACCESS_FS_READ_FILE |
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LANDLOCK_ACCESS_FS_READ_DIR,
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.parent_fd = fd,
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};
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if (landlock_add_rule(landlock_fd, LANDLOCK_RULE_PATH_BENEATH,
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&lpba, 0) == -1) {
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saved_errno = errno;
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close(fd);
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errno = saved_errno;
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return -1;
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}
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close(fd);
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}
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return 0;
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}
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void
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sandbox_main_process(void)
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{
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return;
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}
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void
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sandbox_server_process(void)
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{
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if (landlock_unveil("/", "r") == -1)
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fatal("landlock_unveil(/)");
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if (landlock_unveil(NULL, NULL) == -1)
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fatal("landlock_unveil(NULL, NULL)");
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}
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void
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sandbox_crypto_process(void)
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{
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/* contrary to unveil(2), this removes all fs access. */
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if (landlock_unveil(NULL, NULL) == -1)
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fatal("landlock_unveil(NULL, NULL)");
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}
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void
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sandbox_logger_process(void)
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{
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/* contrary to unveil(2), this removes all fs access. */
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if (landlock_unveil(NULL, NULL) == -1)
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fatal("landlock_unveil(NULL, NULL)");
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}
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#else
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void
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sandbox_main_process(void)
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{
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return;
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}
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void
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sandbox_server_process(void)
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{
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return;
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}
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void
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sandbox_crypto_process(void)
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{
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return;
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}
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void
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sandbox_logger_process(void)
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{
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return;
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}
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#endif
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