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/**
* Zero-Clause BSD
* ===============
*
* Copyright 2024 shtrophic <christoph@liebender.dev>
*
* Permission to use, copy, modify, and/or distribute this software for
* any purpose with or without fee is hereby granted.
*
* THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL
* WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE
* FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY
* DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
* AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
* OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
*/
/**
* Repository: https://git.sr.ht/~shtrophic/landloc.h
*/
/**
* Usage:
*
* Define a sandboxing function using the LL_BEGIN(...) and LL_END macros.
* the arguments of LL_BEGIN are the function's signature.
* Between those macros, implement your sandbox using LL_PATH() and LL_PORT() macros.
* Calling LL_PATH() and LL_PORT() anywhere else will not work.
* You may prepend `static` before LL_BEGIN to make the function static.
* You need (should) wrap your sandboxing code in another set of braces:
*
LL_BEGIN(my_sandbox_function, const char *rw_path) {
LL_PATH(rw_path, LANDLOCK_ACCESS_FS_READ_FILE | LANDLOCK_ACCESS_FS_READ_DIR | LANDLOCK_ACCESS_FS_EXECUTE);
LL_PORT(443, LANDLOCK_ACCESS_NET_CONNECT_TCP);
} LL_END
*
* Then, call it in your application's code.
*
int main(void) {
int status = my_sandbox_function("some/path");
if (status != 0) {
// error
}
}
*
* You may define LL_PRINTERR(fmt, ...) before including this header to enable debug output:
*
#define LL_PRINTERR(fmt, ...) fprintf(stderr, fmt "\n", __VA_ARGS__)
#include "landloc.h"
*/
#ifndef __LANDLOC_H__
#define __LANDLOC_H__
#ifndef __linux__
# error "no landlock without linux"
#endif
#include <linux/version.h>
#if LINUX_VERSION_CODE < KERNEL_VERSION(5, 13, 0)
# error "no landlock on kernels older than 5.13.0"
#endif
#include <unistd.h>
#include <linux/landlock.h>
#include <sys/syscall.h>
#include <sys/prctl.h>
#include <fcntl.h>
#ifndef O_PATH
# define O_PATH 010000000
#endif
#ifndef LL_PRINTERR
# define LL_PRINTERR(fmt, ...) (void)fmt;
#else
# include <string.h>
# include <errno.h>
#endif
#ifdef LANDLOCK_ACCESS_FS_REFER
# define LANDLOCK_ACCESS_FS_REFER_COMPAT LANDLOCK_ACCESS_FS_REFER
# define __LL_SWITCH_FS_REFER __rattr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_REFER_COMPAT
#else
# define LANDLOCK_ACCESS_FS_REFER_COMPAT 0
# define __LL_SWITCH_FS_REFER (void)0
#endif
#ifdef LANDLOCK_ACCESS_FS_TRUNCATE
# define LANDLOCK_ACCESS_FS_TRUNCATE_COMPAT LANDLOCK_ACCESS_FS_TRUNCATE
# define __LL_SWITCH_FS_TRUNCATE __rattr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_TRUNCATE_COMPAT
#else
# define LANDLOCK_ACCESS_FS_TRUNCATE_COMPAT 0
# define __LL_SWITCH_FS_TRUNCATE (void)0
#endif
#ifdef LANDLOCK_ACCESS_FS_IOCTL_DEV
# define LANDLOCK_ACCESS_FS_IOCTL_DEV_COMPAT LANDLOCK_ACCESS_FS_IOCTL_DEV
# define __LL_SWITCH_FS_IOCTL_DEV __rattr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV_COMPAT
#else
# define LANDLOCK_ACCESS_FS_IOCTL_DEV_COMPAT 0
# define __LL_SWITCH_FS_IOCTL_DEV (void)0
#endif
#define LL_FS_ALL (\
LANDLOCK_ACCESS_FS_EXECUTE |\
LANDLOCK_ACCESS_FS_WRITE_FILE |\
LANDLOCK_ACCESS_FS_READ_FILE |\
LANDLOCK_ACCESS_FS_READ_DIR |\
LANDLOCK_ACCESS_FS_REMOVE_DIR |\
LANDLOCK_ACCESS_FS_REMOVE_FILE |\
LANDLOCK_ACCESS_FS_MAKE_CHAR |\
LANDLOCK_ACCESS_FS_MAKE_DIR |\
LANDLOCK_ACCESS_FS_MAKE_REG |\
LANDLOCK_ACCESS_FS_MAKE_SOCK |\
LANDLOCK_ACCESS_FS_MAKE_FIFO |\
LANDLOCK_ACCESS_FS_MAKE_BLOCK |\
LANDLOCK_ACCESS_FS_MAKE_SYM |\
LANDLOCK_ACCESS_FS_REFER_COMPAT |\
LANDLOCK_ACCESS_FS_TRUNCATE_COMPAT |\
LANDLOCK_ACCESS_FS_IOCTL_DEV_COMPAT )
#if defined(LANDLOCK_ACCESS_NET_BIND_TCP) && defined(LANDLOCK_ACCESS_NET_CONNECT_TCP)
# define LL_HAVE_NET 1
# define LANDLOCK_ACCESS_NET_BIND_TCP_COMPAT LANDLOCK_ACCESS_NET_BIND_TCP
# define LANDLOCK_ACCESS_NET_CONNECT_TCP_COMPAT LANDLOCK_ACCESS_NET_CONNECT_TCP
# define LL_NET_ALL (LANDLOCK_ACCESS_NET_BIND_TCP_COMPAT | LANDLOCK_ACCESS_NET_CONNECT_TCP_COMPAT)
# define __LL_DECLARE_NET struct landlock_net_port_attr __nattr = {0}
# define __LL_INIT_NET __rattr.handled_access_net = LL_NET_ALL
# define __LL_SWITCH_NET do { __rattr.handled_access_net &= ~(LANDLOCK_ACCESS_NET_BIND_TCP | LANDLOCK_ACCESS_NET_CONNECT_TCP); } while (0)
#else
# define LL_HAVE_NET 0
# define LANDLOCK_ACCESS_NET_BIND_TCP_COMPAT 0
# define LANDLOCK_ACCESS_NET_CONNECT_TCP_COMPAT 0
# define LL_NET_ALL 0
# define __LL_DECLARE_NET (void)0
# define __LL_INIT_NET (void)0
# define __LL_SWITCH_NET (void)0
#endif
#define LL_BEGIN(function, ...) int function(__VA_ARGS__) {\
int ll_rule_fd, ll_abi;\
struct landlock_ruleset_attr __rattr = {0};\
struct landlock_path_beneath_attr __pattr = {0};\
__LL_DECLARE_NET;\
int __err = 0;\
__rattr.handled_access_fs = LL_FS_ALL;\
__LL_INIT_NET;\
ll_abi = (int)syscall(SYS_landlock_create_ruleset, NULL, 0, LANDLOCK_CREATE_RULESET_VERSION);\
switch (ll_abi) {\
case -1: return -1;\
case 1: __LL_SWITCH_FS_REFER; __attribute__((fallthrough));\
case 2: __LL_SWITCH_FS_TRUNCATE; __attribute__((fallthrough));\
case 3: __LL_SWITCH_NET; __attribute__((fallthrough));\
case 4: __LL_SWITCH_FS_IOCTL_DEV;\
default: break;\
}\
ll_rule_fd = (int)syscall(SYS_landlock_create_ruleset, &__rattr, sizeof(struct landlock_ruleset_attr), 0);\
if (-1 == ll_rule_fd) {\
LL_PRINTERR("landlock_create_ruleset: %s", strerror(errno));\
return -1;\
}
#define LL_END \
__err = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);\
if (-1 == __err) {\
LL_PRINTERR("set_no_new_privs: %s", strerror(errno));\
goto __close;\
}\
__err = (int)syscall(SYS_landlock_restrict_self, ll_rule_fd, 0);\
if (__err)\
LL_PRINTERR("landlock_restrict_self: %s", strerror(errno));\
__close: close(ll_rule_fd);\
return __err; }
#define LL_PATH(p, rules) do {\
const char *__path = (p);\
__pattr.allowed_access = (rules) & __rattr.handled_access_fs;\
if (__pattr.allowed_access != 0) {\
__pattr.parent_fd = open(__path, O_PATH | O_CLOEXEC);\
if (-1 == __pattr.parent_fd) {\
LL_PRINTERR("open(%s): %s", __path, strerror(errno));\
__err = -1;\
goto __close;\
}\
__err = (int)syscall(SYS_landlock_add_rule, ll_rule_fd, LANDLOCK_RULE_PATH_BENEATH, &__pattr, 0);\
if (__err) {\
LL_PRINTERR("landlock_add_rule(%s): %s", __path, strerror(errno));\
goto __close;\
}\
close(__pattr.parent_fd);\
}\
} while (0)
#if LL_HAVE_NET
#define LL_PORT(p, rules) do {\
unsigned short __port = (p);\
__nattr.allowed_access = (rules);\
if (ll_abi > 3 && __nattr.allowed_access != 0) {\
__nattr.port = __port;\
__err = (int)syscall(SYS_landlock_add_rule, ll_rule_fd, LANDLOCK_RULE_NET_PORT, &__nattr, 0);\
if (__err) {\
LL_PRINTERR("landlock_add_rule(%u): %s", __port, strerror(errno));\
goto __close;\
}\
}\
} while (0)
#else
#define LL_PORT(p, rules) do {\
unsigned short __port = (p);\
__u64 __rules = (rules);\
(void)__port;\
(void)__rules;\
} while (0)
#endif /* LL_HAVE_NET */
#endif /* __LANDLOC_H__ */
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