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systemd/src/shared/acl-util.c
Zbigniew Jędrzejewski-Szmek 04499a70fb Drop the text argument from assert_not_reached() 
In general we almost never hit those asserts in production code, so users see
them very rarely, if ever. But either way, we just need something that users
can pass to the developers.

We have quite a few of those asserts, and some have fairly nice messages, but
many are like "WTF?" or "???" or "unexpected something". The error that is
printed includes the file location, and function name. In almost all functions
there's at most one assert, so the function name alone is enough to identify
the failure for a developer. So we don't get much extra from the message, and
we might just as well drop them.

Dropping them makes our code a tiny bit smaller, and most importantly, improves
development experience by making it easy to insert such an assert in the code
without thinking how to phrase the argument.
2021-08-03 10:05:10 +02:00

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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <stdbool.h>
#include <sys/stat.h>
#include <sys/types.h>
#include "acl-util.h"
#include "alloc-util.h"
#include "string-util.h"
#include "strv.h"
#include "user-util.h"
#include "util.h"
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 = acl_get_entry(acl, ACL_FIRST_ENTRY, &i);
r > 0;
r = acl_get_entry(acl, ACL_NEXT_ENTRY, &i)) {
acl_tag_t tag;
uid_t *u;
bool b;
if (acl_get_tag_type(i, &tag) < 0)
return -errno;
if (tag != ACL_USER)
continue;
u = acl_get_qualifier(i);
if (!u)
return -errno;
b = *u == uid;
acl_free(u);
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 = acl_get_entry(*acl_p, ACL_FIRST_ENTRY, &i);
r > 0;
r = acl_get_entry(*acl_p, ACL_NEXT_ENTRY, &i)) {
acl_tag_t tag;
if (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 && 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);
for (r = acl_get_entry(*acl_p, ACL_FIRST_ENTRY, &i);
r > 0;
r = acl_get_entry(*acl_p, ACL_NEXT_ENTRY, &i)) {
acl_tag_t tag;
if (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;
r = stat(path, &st);
if (r < 0)
return -errno;
basic = acl_from_mode(st.st_mode);
if (!basic)
return -errno;
for (r = acl_get_entry(basic, ACL_FIRST_ENTRY, &i);
r > 0;
r = acl_get_entry(basic, ACL_NEXT_ENTRY, &i)) {
acl_tag_t tag;
acl_entry_t dst;
if (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 = acl_create_entry(acl_p, &dst);
if (r < 0)
return -errno;
r = 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);
acl = acl_get_file(path, ACL_TYPE_DEFAULT);
if (!acl)
return -errno;
r = 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 (acl_get_tag_type(entry, &tag) < 0)
return -errno;
if (tag != ACL_GROUP)
goto next;
gid = 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 = 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 *acl_access, acl_t *acl_default, bool want_mask) {
_cleanup_free_ char **a = NULL, **d = NULL; /* strings are not freed */
_cleanup_strv_free_ char **split = NULL;
char **entry;
int r = -EINVAL;
_cleanup_(acl_freep) acl_t a_acl = NULL, d_acl = NULL;
split = strv_split(text, ",");
if (!split)
return -ENOMEM;
STRV_FOREACH(entry, split) {
char *p;
p = STARTSWITH_SET(*entry, "default:", "d:");
if (p)
r = strv_push(&d, p);
else
r = strv_push(&a, *entry);
if (r < 0)
return r;
}
if (!strv_isempty(a)) {
_cleanup_free_ char *join = NULL;
join = strv_join(a, ",");
if (!join)
return -ENOMEM;
a_acl = 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(d)) {
_cleanup_free_ char *join = NULL;
join = strv_join(d, ",");
if (!join)
return -ENOMEM;
d_acl = 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;
}
}
*acl_access = TAKE_PTR(a_acl);
*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 (acl_get_tag_type(a, &tag_a) < 0)
return -errno;
if (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 = acl_get_qualifier(a);
if (!uid_a)
return -errno;
uid_b = 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 = acl_get_qualifier(a);
if (!gid_a)
return -errno;
gid_b = 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 *out) {
acl_entry_t i;
int r;
for (r = acl_get_entry(acl, ACL_FIRST_ENTRY, &i);
r > 0;
r = acl_get_entry(acl, ACL_NEXT_ENTRY, &i)) {
r = acl_entry_equal(i, entry);
if (r < 0)
return r;
if (r > 0) {
*out = i;
return 1;
}
}
if (r < 0)
return -errno;
return 0;
}
int acls_for_file(const char *path, acl_type_t type, acl_t new, acl_t *acl) {
_cleanup_(acl_freep) acl_t old;
acl_entry_t i;
int r;
old = acl_get_file(path, type);
if (!old)
return -errno;
for (r = acl_get_entry(new, ACL_FIRST_ENTRY, &i);
r > 0;
r = acl_get_entry(new, ACL_NEXT_ENTRY, &i)) {
acl_entry_t j;
r = find_acl_entry(old, i, &j);
if (r < 0)
return r;
if (r == 0)
if (acl_create_entry(&old, &j) < 0)
return -errno;
if (acl_copy_entry(j, i) < 0)
return -errno;
}
if (r < 0)
return -errno;
*acl = TAKE_PTR(old);
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));
acl = acl_get_fd(fd);
if (!acl)
return -errno;
r = acl_find_uid(acl, uid, &entry);
if (r <= 0) {
if (acl_create_entry(&acl, &entry) < 0 ||
acl_set_tag_type(entry, ACL_USER) < 0 ||
acl_set_qualifier(entry, &uid) < 0)
return -errno;
}
if (acl_get_permset(entry, &permset) < 0)
return -errno;
if ((mask & ACL_READ) && acl_add_perm(permset, ACL_READ) < 0)
return -errno;
if ((mask & ACL_WRITE) && acl_add_perm(permset, ACL_WRITE) < 0)
return -errno;
if ((mask & ACL_EXECUTE) && acl_add_perm(permset, ACL_EXECUTE) < 0)
return -errno;
r = calc_acl_mask_if_needed(&acl);
if (r < 0)
return r;
if (acl_set_fd(fd, acl) < 0)
return -errno;
return 0;
}
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