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systemd/src/shared/acl-util.c

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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <sys/stat.h>
#include "acl-util.h"
#include "alloc-util.h"
#include "errno-util.h"
#include "extract-word.h"
#include "fd-util.h"
#include "log.h"
#include "string-util.h"
#include "strv.h"
#include "user-util.h"
#if HAVE_ACL
static void *libacl_dl = NULL;
DLSYM_PROTOTYPE(acl_add_perm);
DLSYM_PROTOTYPE(acl_calc_mask);
DLSYM_PROTOTYPE(acl_copy_entry);
DLSYM_PROTOTYPE(acl_create_entry);
DLSYM_PROTOTYPE(acl_delete_entry);
DLSYM_PROTOTYPE(acl_delete_perm);
DLSYM_PROTOTYPE(acl_dup);
DLSYM_PROTOTYPE(acl_entries);
DLSYM_PROTOTYPE(acl_extended_file);
DLSYM_PROTOTYPE(acl_free);
DLSYM_PROTOTYPE(acl_from_mode);
DLSYM_PROTOTYPE(acl_from_text);
DLSYM_PROTOTYPE(acl_get_entry);
DLSYM_PROTOTYPE(acl_get_fd);
DLSYM_PROTOTYPE(acl_get_file);
DLSYM_PROTOTYPE(acl_get_perm);
DLSYM_PROTOTYPE(acl_get_permset);
DLSYM_PROTOTYPE(acl_get_qualifier);
DLSYM_PROTOTYPE(acl_get_tag_type);
DLSYM_PROTOTYPE(acl_init);
DLSYM_PROTOTYPE(acl_set_fd);
DLSYM_PROTOTYPE(acl_set_file);
DLSYM_PROTOTYPE(acl_set_permset);
DLSYM_PROTOTYPE(acl_set_qualifier);
DLSYM_PROTOTYPE(acl_set_tag_type);
DLSYM_PROTOTYPE(acl_to_any_text);
int dlopen_libacl(void) {
ELF_NOTE_DLOPEN("acl",
"Support for file Access Control Lists (ACLs)",
ELF_NOTE_DLOPEN_PRIORITY_RECOMMENDED,
"libacl.so.1");
return dlopen_many_sym_or_warn(
&libacl_dl,
"libacl.so.1",
LOG_DEBUG,
DLSYM_ARG(acl_add_perm),
DLSYM_ARG(acl_calc_mask),
DLSYM_ARG(acl_copy_entry),
DLSYM_ARG(acl_create_entry),
DLSYM_ARG(acl_delete_entry),
DLSYM_ARG(acl_delete_perm),
DLSYM_ARG(acl_dup),
DLSYM_ARG(acl_entries),
DLSYM_ARG(acl_extended_file),
DLSYM_ARG(acl_free),
DLSYM_ARG(acl_from_mode),
DLSYM_ARG(acl_from_text),
DLSYM_ARG(acl_get_entry),
DLSYM_ARG(acl_get_fd),
DLSYM_ARG(acl_get_file),
DLSYM_ARG(acl_get_perm),
DLSYM_ARG(acl_get_permset),
DLSYM_ARG(acl_get_qualifier),
DLSYM_ARG(acl_get_tag_type),
DLSYM_ARG(acl_init),
DLSYM_ARG(acl_set_fd),
DLSYM_ARG(acl_set_file),
DLSYM_ARG(acl_set_permset),
DLSYM_ARG(acl_set_qualifier),
DLSYM_ARG(acl_set_tag_type),
DLSYM_ARG(acl_to_any_text));
}
int devnode_acl(int fd, uid_t uid) {
bool changed = false, found = false;
int r;
assert(fd >= 0);
r = dlopen_libacl();
if (r < 0)
return r;
_cleanup_(acl_freep) acl_t acl = NULL;
acl = sym_acl_get_file(FORMAT_PROC_FD_PATH(fd), ACL_TYPE_ACCESS);
if (!acl)
return -errno;
acl_entry_t entry;
for (r = sym_acl_get_entry(acl, ACL_FIRST_ENTRY, &entry);
r > 0;
r = sym_acl_get_entry(acl, ACL_NEXT_ENTRY, &entry)) {
acl_tag_t tag;
if (sym_acl_get_tag_type(entry, &tag) < 0)
return -errno;
if (tag != ACL_USER)
continue;
if (uid > 0) {
uid_t *u = sym_acl_get_qualifier(entry);
if (!u)
return -errno;
if (*u == uid) {
acl_permset_t permset;
if (sym_acl_get_permset(entry, &permset) < 0)
return -errno;
int rd = sym_acl_get_perm(permset, ACL_READ);
if (rd < 0)
return -errno;
int wt = sym_acl_get_perm(permset, ACL_WRITE);
if (wt < 0)
return -errno;
if (!rd || !wt) {
if (sym_acl_add_perm(permset, ACL_READ|ACL_WRITE) < 0)
return -errno;
changed = true;
}
found = true;
continue;
}
}
if (sym_acl_delete_entry(acl, entry) < 0)
return -errno;
changed = true;
}
if (r < 0)
return -errno;
if (!found && uid > 0) {
if (sym_acl_create_entry(&acl, &entry) < 0)
return -errno;
if (sym_acl_set_tag_type(entry, ACL_USER) < 0)
return -errno;
if (sym_acl_set_qualifier(entry, &uid) < 0)
return -errno;
acl_permset_t permset;
if (sym_acl_get_permset(entry, &permset) < 0)
return -errno;
if (sym_acl_add_perm(permset, ACL_READ|ACL_WRITE) < 0)
return -errno;
changed = true;
}
if (!changed)
return 0;
if (sym_acl_calc_mask(&acl) < 0)
return -errno;
if (sym_acl_set_file(FORMAT_PROC_FD_PATH(fd), ACL_TYPE_ACCESS, acl) < 0)
return -errno;
return 0;
}
static int acl_find_uid(acl_t acl, uid_t uid, acl_entry_t *ret_entry) {
acl_entry_t i;
int r;
assert(acl);
assert(uid_is_valid(uid));
assert(ret_entry);
for (r = sym_acl_get_entry(acl, ACL_FIRST_ENTRY, &i);
r > 0;
r = sym_acl_get_entry(acl, ACL_NEXT_ENTRY, &i)) {
acl_tag_t tag;
bool b;
if (sym_acl_get_tag_type(i, &tag) < 0)
return -errno;
if (tag != ACL_USER)
continue;
_cleanup_(acl_free_uid_tpp) uid_t *u = NULL;
u = sym_acl_get_qualifier(i);
if (!u)
return -errno;
b = *u == uid;
if (b) {
*ret_entry = i;
return 1;
}
}
if (r < 0)
return -errno;
*ret_entry = NULL;
return 0;
}
int calc_acl_mask_if_needed(acl_t *acl_p) {
acl_entry_t i;
int r;
bool need = false;
assert(acl_p);
for (r = sym_acl_get_entry(*acl_p, ACL_FIRST_ENTRY, &i);
r > 0;
r = sym_acl_get_entry(*acl_p, ACL_NEXT_ENTRY, &i)) {
acl_tag_t tag;
if (sym_acl_get_tag_type(i, &tag) < 0)
return -errno;
if (tag == ACL_MASK)
return 0;
if (IN_SET(tag, ACL_USER, ACL_GROUP))
need = true;
}
if (r < 0)
return -errno;
if (need && sym_acl_calc_mask(acl_p) < 0)
return -errno;
return need;
}
int add_base_acls_if_needed(acl_t *acl_p, const char *path) {
acl_entry_t i;
int r;
bool have_user_obj = false, have_group_obj = false, have_other = false;
struct stat st;
_cleanup_(acl_freep) acl_t basic = NULL;
assert(acl_p);
assert(path);
for (r = sym_acl_get_entry(*acl_p, ACL_FIRST_ENTRY, &i);
r > 0;
r = sym_acl_get_entry(*acl_p, ACL_NEXT_ENTRY, &i)) {
acl_tag_t tag;
if (sym_acl_get_tag_type(i, &tag) < 0)
return -errno;
if (tag == ACL_USER_OBJ)
have_user_obj = true;
else if (tag == ACL_GROUP_OBJ)
have_group_obj = true;
else if (tag == ACL_OTHER)
have_other = true;
if (have_user_obj && have_group_obj && have_other)
return 0;
}
if (r < 0)
return -errno;
if (stat(path, &st) < 0)
return -errno;
basic = sym_acl_from_mode(st.st_mode);
if (!basic)
return -errno;
for (r = sym_acl_get_entry(basic, ACL_FIRST_ENTRY, &i);
r > 0;
r = sym_acl_get_entry(basic, ACL_NEXT_ENTRY, &i)) {
acl_tag_t tag;
acl_entry_t dst;
if (sym_acl_get_tag_type(i, &tag) < 0)
return -errno;
if ((tag == ACL_USER_OBJ && have_user_obj) ||
(tag == ACL_GROUP_OBJ && have_group_obj) ||
(tag == ACL_OTHER && have_other))
continue;
r = sym_acl_create_entry(acl_p, &dst);
if (r < 0)
return -errno;
r = sym_acl_copy_entry(dst, i);
if (r < 0)
return -errno;
}
if (r < 0)
return -errno;
return 0;
}
int acl_search_groups(const char *path, char ***ret_groups) {
_cleanup_strv_free_ char **g = NULL;
_cleanup_(acl_freep) acl_t acl = NULL;
bool ret = false;
acl_entry_t entry;
int r;
assert(path);
r = dlopen_libacl();
if (r < 0)
return r;
acl = sym_acl_get_file(path, ACL_TYPE_DEFAULT);
if (!acl)
return -errno;
r = sym_acl_get_entry(acl, ACL_FIRST_ENTRY, &entry);
for (;;) {
_cleanup_(acl_free_gid_tpp) gid_t *gid = NULL;
acl_tag_t tag;
if (r < 0)
return -errno;
if (r == 0)
break;
if (sym_acl_get_tag_type(entry, &tag) < 0)
return -errno;
if (tag != ACL_GROUP)
goto next;
gid = sym_acl_get_qualifier(entry);
if (!gid)
return -errno;
if (in_gid(*gid) > 0) {
if (!ret_groups)
return true;
ret = true;
}
if (ret_groups) {
char *name;
name = gid_to_name(*gid);
if (!name)
return -ENOMEM;
r = strv_consume(&g, name);
if (r < 0)
return r;
}
next:
r = sym_acl_get_entry(acl, ACL_NEXT_ENTRY, &entry);
}
if (ret_groups)
*ret_groups = TAKE_PTR(g);
return ret;
}
int parse_acl(
const char *text,
acl_t *ret_acl_access,
acl_t *ret_acl_access_exec, /* extra rules to apply to inodes subject to uppercase X handling */
acl_t *ret_acl_default,
bool want_mask) {
_cleanup_strv_free_ char **a = NULL, **e = NULL, **d = NULL, **split = NULL;
_cleanup_(acl_freep) acl_t a_acl = NULL, e_acl = NULL, d_acl = NULL;
int r;
assert(text);
assert(ret_acl_access);
assert(ret_acl_access_exec);
assert(ret_acl_default);
split = strv_split(text, ",");
if (!split)
return -ENOMEM;
r = dlopen_libacl();
if (r < 0)
return r;
STRV_FOREACH(entry, split) {
_cleanup_strv_free_ char **entry_split = NULL;
_cleanup_free_ char *entry_join = NULL;
int n;
n = strv_split_full(&entry_split, *entry, ":", EXTRACT_DONT_COALESCE_SEPARATORS|EXTRACT_RETAIN_ESCAPE);
if (n < 0)
return n;
if (n < 3 || n > 4)
return -EINVAL;
string_replace_char(entry_split[n-1], 'X', 'x');
if (n == 4) {
if (!STR_IN_SET(entry_split[0], "default", "d"))
return -EINVAL;
entry_join = strv_join(entry_split + 1, ":");
if (!entry_join)
return -ENOMEM;
r = strv_consume(&d, TAKE_PTR(entry_join));
} else { /* n == 3 */
entry_join = strv_join(entry_split, ":");
if (!entry_join)
return -ENOMEM;
if (!streq(*entry, entry_join))
r = strv_consume(&e, TAKE_PTR(entry_join));
else
r = strv_consume(&a, TAKE_PTR(entry_join));
}
if (r < 0)
return r;
}
if (!strv_isempty(a)) {
_cleanup_free_ char *join = NULL;
join = strv_join(a, ",");
if (!join)
return -ENOMEM;
a_acl = sym_acl_from_text(join);
if (!a_acl)
return -errno;
if (want_mask) {
r = calc_acl_mask_if_needed(&a_acl);
if (r < 0)
return r;
}
}
if (!strv_isempty(e)) {
_cleanup_free_ char *join = NULL;
join = strv_join(e, ",");
if (!join)
return -ENOMEM;
e_acl = sym_acl_from_text(join);
if (!e_acl)
return -errno;
/* The mask must be calculated after deciding whether the execute bit should be set. */
}
if (!strv_isempty(d)) {
_cleanup_free_ char *join = NULL;
join = strv_join(d, ",");
if (!join)
return -ENOMEM;
d_acl = sym_acl_from_text(join);
if (!d_acl)
return -errno;
if (want_mask) {
r = calc_acl_mask_if_needed(&d_acl);
if (r < 0)
return r;
}
}
*ret_acl_access = TAKE_PTR(a_acl);
*ret_acl_access_exec = TAKE_PTR(e_acl);
*ret_acl_default = TAKE_PTR(d_acl);
return 0;
}
static int acl_entry_equal(acl_entry_t a, acl_entry_t b) {
acl_tag_t tag_a, tag_b;
if (sym_acl_get_tag_type(a, &tag_a) < 0)
return -errno;
if (sym_acl_get_tag_type(b, &tag_b) < 0)
return -errno;
if (tag_a != tag_b)
return false;
switch (tag_a) {
case ACL_USER_OBJ:
case ACL_GROUP_OBJ:
case ACL_MASK:
case ACL_OTHER:
/* can have only one of those */
return true;
case ACL_USER: {
_cleanup_(acl_free_uid_tpp) uid_t *uid_a = NULL, *uid_b = NULL;
uid_a = sym_acl_get_qualifier(a);
if (!uid_a)
return -errno;
uid_b = sym_acl_get_qualifier(b);
if (!uid_b)
return -errno;
return *uid_a == *uid_b;
}
case ACL_GROUP: {
_cleanup_(acl_free_gid_tpp) gid_t *gid_a = NULL, *gid_b = NULL;
gid_a = sym_acl_get_qualifier(a);
if (!gid_a)
return -errno;
gid_b = sym_acl_get_qualifier(b);
if (!gid_b)
return -errno;
return *gid_a == *gid_b;
}
default:
assert_not_reached();
}
}
static int find_acl_entry(acl_t acl, acl_entry_t entry, acl_entry_t *ret) {
acl_entry_t i;
int r;
for (r = sym_acl_get_entry(acl, ACL_FIRST_ENTRY, &i);
r > 0;
r = sym_acl_get_entry(acl, ACL_NEXT_ENTRY, &i)) {
r = acl_entry_equal(i, entry);
if (r < 0)
return r;
if (r > 0) {
if (ret)
*ret = i;
return 0;
}
}
if (r < 0)
return -errno;
return -ENOENT;
}
int acls_for_file(const char *path, acl_type_t type, acl_t acl, acl_t *ret) {
_cleanup_(acl_freep) acl_t applied = NULL;
acl_entry_t i;
int r;
assert(path);
r = dlopen_libacl();
if (r < 0)
return r;
applied = sym_acl_get_file(path, type);
if (!applied)
return -errno;
for (r = sym_acl_get_entry(acl, ACL_FIRST_ENTRY, &i);
r > 0;
r = sym_acl_get_entry(acl, ACL_NEXT_ENTRY, &i)) {
acl_entry_t j;
r = find_acl_entry(applied, i, &j);
if (r == -ENOENT) {
if (sym_acl_create_entry(&applied, &j) < 0)
return -errno;
} else if (r < 0)
return r;
if (sym_acl_copy_entry(j, i) < 0)
return -errno;
}
if (r < 0)
return -errno;
if (ret)
*ret = TAKE_PTR(applied);
return 0;
}
/* POSIX says that ACL_{READ,WRITE,EXECUTE} don't have to be bitmasks. But that is a natural thing to do and
* all extant implementations do it. Let's make sure that we fail verbosely in the (imho unlikely) scenario
* that we get a new implementation that does not satisfy this. */
assert_cc(!(ACL_READ & ACL_WRITE));
assert_cc(!(ACL_WRITE & ACL_EXECUTE));
assert_cc(!(ACL_EXECUTE & ACL_READ));
assert_cc((unsigned) ACL_READ == ACL_READ);
assert_cc((unsigned) ACL_WRITE == ACL_WRITE);
assert_cc((unsigned) ACL_EXECUTE == ACL_EXECUTE);
int fd_add_uid_acl_permission(
int fd,
uid_t uid,
unsigned mask) {
_cleanup_(acl_freep) acl_t acl = NULL;
acl_permset_t permset;
acl_entry_t entry;
int r;
/* Adds an ACL entry for the specified file to allow the indicated access to the specified
* user. Operates purely incrementally. */
assert(fd >= 0);
assert(uid_is_valid(uid));
r = dlopen_libacl();
if (r < 0)
return r;
acl = sym_acl_get_fd(fd);
if (!acl)
return -errno;
r = acl_find_uid(acl, uid, &entry);
if (r <= 0) {
if (sym_acl_create_entry(&acl, &entry) < 0 ||
sym_acl_set_tag_type(entry, ACL_USER) < 0 ||
sym_acl_set_qualifier(entry, &uid) < 0)
return -errno;
}
if (sym_acl_get_permset(entry, &permset) < 0)
return -errno;
if ((mask & ACL_READ) && sym_acl_add_perm(permset, ACL_READ) < 0)
return -errno;
if ((mask & ACL_WRITE) && sym_acl_add_perm(permset, ACL_WRITE) < 0)
return -errno;
if ((mask & ACL_EXECUTE) && sym_acl_add_perm(permset, ACL_EXECUTE) < 0)
return -errno;
r = calc_acl_mask_if_needed(&acl);
if (r < 0)
return r;
if (sym_acl_set_fd(fd, acl) < 0)
return -errno;
return 0;
}
int fd_acl_make_read_only(int fd) {
_cleanup_(acl_freep) acl_t acl = NULL;
bool changed = false;
acl_entry_t i;
int r;
assert(fd >= 0);
/* Safely drops all W bits from all relevant ACL entries of the file, without changing entries which
* are masked by the ACL mask */
r = dlopen_libacl();
if (r < 0)
goto maybe_fallback;
acl = sym_acl_get_fd(fd);
if (!acl) {
r = -errno;
goto maybe_fallback;
}
for (r = sym_acl_get_entry(acl, ACL_FIRST_ENTRY, &i);
r > 0;
r = sym_acl_get_entry(acl, ACL_NEXT_ENTRY, &i)) {
acl_permset_t permset;
acl_tag_t tag;
int b;
if (sym_acl_get_tag_type(i, &tag) < 0)
return -errno;
/* These three control the x bits overall (as ACL_MASK affects all remaining tags) */
if (!IN_SET(tag, ACL_USER_OBJ, ACL_MASK, ACL_OTHER))
continue;
if (sym_acl_get_permset(i, &permset) < 0)
return -errno;
b = sym_acl_get_perm(permset, ACL_WRITE);
if (b < 0)
return -errno;
if (b) {
if (sym_acl_delete_perm(permset, ACL_WRITE) < 0)
return -errno;
changed = true;
}
}
if (r < 0)
return -errno;
if (!changed)
return 0;
if (sym_acl_set_fd(fd, acl) < 0) {
r = -errno;
goto maybe_fallback;
}
return 1;
maybe_fallback:
if (!ERRNO_IS_NEG_NOT_SUPPORTED(r))
return r;
/* No ACLs? Then just update the regular mode_t */
return fd_acl_make_read_only_fallback(fd);
}
#endif
int fd_acl_make_read_only_fallback(int fd) {
struct stat st;
assert(fd >= 0);
if (fstat(fd, &st) < 0)
return -errno;
if ((st.st_mode & 0222) == 0)
return 0;
if (fchmod(fd, st.st_mode & 0555) < 0)
return -errno;
return 1;
}
int inode_type_can_acl(mode_t mode) {
return IN_SET(mode & S_IFMT, S_IFSOCK, S_IFREG, S_IFBLK, S_IFCHR, S_IFDIR, S_IFIFO);
}
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