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/*
* SPDX-License-Identifier: GPL-2.0-or-later
*
* 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.
*
* Copyright (C) 2023 Thomas Weißschuh <thomas@t-8ch.de>
*/
#include <sys/prctl.h>
#include <sys/syscall.h>
#include <linux/landlock.h>
#include "setpriv-landlock.h"
#include "strutils.h"
#include "xalloc.h"
#include "nls.h"
#include "c.h"
#ifndef HAVE_LANDLOCK_CREATE_RULESET
static inline int landlock_create_ruleset(
const struct landlock_ruleset_attr *attr,
size_t size, uint32_t flags)
{
return syscall(__NR_landlock_create_ruleset, attr, size, flags);
}
#endif
#ifndef HAVE_LANDLOCK_ADD_RULE
static inline int landlock_add_rule(
int ruleset_fd, enum landlock_rule_type rule_type,
const void *rule_attr, uint32_t flags)
{
return syscall(__NR_landlock_add_rule, ruleset_fd, rule_type,
rule_attr, flags);
}
#endif
#ifndef HAVE_LANDLOCK_RESTRICT_SELF
static inline int landlock_restrict_self(int ruleset_fd, uint32_t flags)
{
return syscall(__NR_landlock_restrict_self, ruleset_fd, flags);
}
#endif
#define SETPRIV_EXIT_PRIVERR 127 /* how we exit when we fail to set privs */
struct landlock_rule_entry {
struct list_head head;
enum landlock_rule_type rule_type;
union {
struct landlock_path_beneath_attr path_beneath_attr;
};
};
static const struct {
unsigned long long value;
const char *type;
} landlock_access_fs[] = {
{ LANDLOCK_ACCESS_FS_EXECUTE, "execute" },
{ LANDLOCK_ACCESS_FS_WRITE_FILE, "write-file" },
{ LANDLOCK_ACCESS_FS_READ_FILE, "read-file" },
{ LANDLOCK_ACCESS_FS_READ_DIR, "read-dir" },
{ LANDLOCK_ACCESS_FS_REMOVE_DIR, "remove-dir" },
{ LANDLOCK_ACCESS_FS_REMOVE_FILE, "remove-file" },
{ LANDLOCK_ACCESS_FS_MAKE_CHAR, "make-char" },
{ LANDLOCK_ACCESS_FS_MAKE_DIR, "make-dir" },
{ LANDLOCK_ACCESS_FS_MAKE_REG, "make-reg" },
{ LANDLOCK_ACCESS_FS_MAKE_SOCK, "make-sock" },
{ LANDLOCK_ACCESS_FS_MAKE_FIFO, "make-fifo" },
{ LANDLOCK_ACCESS_FS_MAKE_BLOCK, "make-block" },
{ LANDLOCK_ACCESS_FS_MAKE_SYM, "make-sym" },
#ifdef LANDLOCK_ACCESS_FS_REFER
{ LANDLOCK_ACCESS_FS_REFER, "refer" },
#endif
#ifdef LANDLOCK_ACCESS_FS_TRUNCATE
{ LANDLOCK_ACCESS_FS_TRUNCATE, "truncate" },
#endif
};
static long landlock_access_to_mask(const char *str, size_t len)
{
size_t i;
for (i = 0; i < ARRAY_SIZE(landlock_access_fs); i++)
if (strncmp(landlock_access_fs[i].type, str, len) == 0)
return landlock_access_fs[i].value;
return -1;
}
static uint64_t parse_landlock_fs_access(const char *list)
{
unsigned long r = 0;
size_t i;
/* without argument, match all */
if (list[0] == '\0') {
for (i = 0; i < ARRAY_SIZE(landlock_access_fs); i++)
r |= landlock_access_fs[i].value;
} else {
if (string_to_bitmask(list, &r, landlock_access_to_mask))
errx(EXIT_FAILURE,
_("could not parse landlock fs access: %s"), list);
}
return r;
}
void parse_landlock_access(struct setpriv_landlock_opts *opts, const char *str)
{
const char *type;
size_t i;
if (strcmp(str, "fs") == 0) {
for (i = 0; i < ARRAY_SIZE(landlock_access_fs); i++)
opts->access_fs |= landlock_access_fs[i].value;
return;
}
type = startswith(str, "fs:");
if (type)
opts->access_fs |= parse_landlock_fs_access(type);
}
void parse_landlock_rule(struct setpriv_landlock_opts *opts, const char *str)
{
struct landlock_rule_entry *rule = xmalloc(sizeof(*rule));
const char *accesses, *path;
char *accesses_part;
int parent_fd;
accesses = startswith(str, "path-beneath:");
if (!accesses)
errx(EXIT_FAILURE, _("invalid landlock rule: %s"), str);
path = strchr(accesses, ':');
if (!path)
errx(EXIT_FAILURE, _("invalid landlock rule: %s"), str);
rule->rule_type = LANDLOCK_RULE_PATH_BENEATH;
accesses_part = xstrndup(accesses, path - accesses);
rule->path_beneath_attr.allowed_access = parse_landlock_fs_access(accesses_part);
free(accesses_part);
path++;
parent_fd = open(path, O_RDONLY | O_PATH | O_CLOEXEC);
if (parent_fd == -1)
err(EXIT_FAILURE, _("could not open file for landlock: %s"), path);
rule->path_beneath_attr.parent_fd = parent_fd;
list_add(&rule->head, &opts->rules);
}
void init_landlock_opts(struct setpriv_landlock_opts *opts)
{
INIT_LIST_HEAD(&opts->rules);
}
void do_landlock(const struct setpriv_landlock_opts *opts)
{
struct landlock_rule_entry *rule;
struct list_head *entry;
int fd, ret;
if (!opts->access_fs)
return;
const struct landlock_ruleset_attr ruleset_attr = {
.handled_access_fs = opts->access_fs,
};
fd = landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
if (fd == -1)
err(SETPRIV_EXIT_PRIVERR, _("landlock_create_ruleset failed"));
list_for_each(entry, &opts->rules) {
rule = list_entry(entry, struct landlock_rule_entry, head);
assert(rule->rule_type == LANDLOCK_RULE_PATH_BENEATH);
ret = landlock_add_rule(fd, rule->rule_type, &rule->path_beneath_attr, 0);
if (ret == -1)
err(SETPRIV_EXIT_PRIVERR, _("adding landlock rule failed"));
}
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1)
err(SETPRIV_EXIT_PRIVERR, _("disallow granting new privileges for landlock failed"));
if (landlock_restrict_self(fd, 0) == -1)
err(SETPRIV_EXIT_PRIVERR, _("landlock_restrict_self faild"));
}
void usage_setpriv(FILE *out)
{
size_t i;
fprintf(out, "\n");
fprintf(out, _("Landlock accesses:\n"));
fprintf(out, " Access: fs\n");
fprintf(out, " Rule types: path-beneath\n");
fprintf(out, " Rules: ");
for (i = 0; i < ARRAY_SIZE(landlock_access_fs); i++) {
fprintf(out, "%s", landlock_access_fs[i].type);
if (i == ARRAY_SIZE(landlock_access_fs) - 1)
fprintf(out, "\n");
else
fprintf(out, ",");
}
}
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