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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <linux/audit.h>
#include <linux/netlink.h>
#include <stdio.h>
#include <sys/socket.h>
#include "alloc-util.h"
#include "audit-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "iovec-util.h"
#include "macro.h"
#include "parse-util.h"
#include "process-util.h"
#include "socket-util.h"
#include "user-util.h"
int audit_session_from_pid(pid_t pid, uint32_t *id) {
_cleanup_free_ char *s = NULL;
const char *p;
uint32_t u;
int r;
assert(id);
/* We don't convert ENOENT to ESRCH here, since we can't
* really distinguish between "audit is not available in the
* kernel" and "the process does not exist", both which will
* result in ENOENT. */
p = procfs_file_alloca(pid, "sessionid");
r = read_one_line_file(p, &s);
if (r < 0)
return r;
r = safe_atou32(s, &u);
if (r < 0)
return r;
if (!audit_session_is_valid(u))
return -ENODATA;
*id = u;
return 0;
}
int audit_loginuid_from_pid(pid_t pid, uid_t *uid) {
_cleanup_free_ char *s = NULL;
const char *p;
uid_t u;
int r;
assert(uid);
p = procfs_file_alloca(pid, "loginuid");
r = read_one_line_file(p, &s);
if (r < 0)
return r;
r = parse_uid(s, &u);
if (r == -ENXIO) /* the UID was -1 */
return -ENODATA;
if (r < 0)
return r;
*uid = u;
return 0;
}
static int try_audit_request(int fd) {
struct iovec iov;
struct msghdr mh;
ssize_t n;
assert(fd >= 0);
struct {
struct nlmsghdr hdr;
struct nlmsgerr err;
} _packed_ msg = {
.hdr.nlmsg_len = NLMSG_LENGTH(0),
.hdr.nlmsg_type = AUDIT_GET_FEATURE,
.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK,
};
iov = IOVEC_MAKE(&msg, msg.hdr.nlmsg_len);
mh = (struct msghdr) {
.msg_iov = &iov,
.msg_iovlen = 1,
};
if (sendmsg(fd, &mh, MSG_NOSIGNAL) < 0)
return -errno;
iov.iov_len = sizeof(msg);
n = recvmsg_safe(fd, &mh, 0);
if (n < 0)
return -errno;
if (n != NLMSG_LENGTH(sizeof(struct nlmsgerr)))
return -EIO;
if (msg.hdr.nlmsg_type != NLMSG_ERROR)
return -EINVAL;
return msg.err.error;
}
bool use_audit(void) {
static int cached_use = -1;
int r;
if (cached_use < 0) {
int fd;
fd = socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK, NETLINK_AUDIT);
if (fd < 0) {
cached_use = !IN_SET(errno, EAFNOSUPPORT, EPROTONOSUPPORT, EPERM);
if (!cached_use)
log_debug_errno(errno, "Won't talk to audit: %m");
} else {
/* If we try and use the audit fd but get -ECONNREFUSED, it is because
* we are not in the initial user namespace, and the kernel does not
* have support for audit outside of the initial user namespace
* (see https://elixir.bootlin.com/linux/latest/C/ident/audit_netlink_ok).
*
* If we receive any other error, do not disable audit because we are not
* sure that the error indicates that audit will not work in general. */
r = try_audit_request(fd);
if (r < 0) {
cached_use = r != -ECONNREFUSED;
log_debug_errno(r, cached_use ?
"Failed to make request on audit fd, ignoring: %m" :
"Won't talk to audit: %m");
} else
cached_use = true;
safe_close(fd);
}
}
return cached_use;
}
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