mirror of
https://github.com/morgan9e/systemd
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bd1ae17833
This is preparation for #28891, which adds a bunch more helpers around "struct iovec", at which point this really deserves its own .c/.h file. The idea is that we sooner or later can consider "struct iovec" as an entirely generic mechanism to reference some binary blob, and is the go-to type for this purpose whenever we need one.
147 lines
4.2 KiB
C
147 lines
4.2 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#include <errno.h>
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#include <linux/audit.h>
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#include <linux/netlink.h>
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#include <stdio.h>
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#include <sys/socket.h>
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#include "alloc-util.h"
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#include "audit-util.h"
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#include "fd-util.h"
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#include "fileio.h"
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#include "iovec-util.h"
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#include "macro.h"
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#include "parse-util.h"
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#include "process-util.h"
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#include "socket-util.h"
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#include "user-util.h"
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int audit_session_from_pid(pid_t pid, uint32_t *id) {
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_cleanup_free_ char *s = NULL;
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const char *p;
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uint32_t u;
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int r;
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assert(id);
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/* We don't convert ENOENT to ESRCH here, since we can't
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* really distinguish between "audit is not available in the
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* kernel" and "the process does not exist", both which will
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* result in ENOENT. */
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p = procfs_file_alloca(pid, "sessionid");
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r = read_one_line_file(p, &s);
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if (r < 0)
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return r;
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r = safe_atou32(s, &u);
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if (r < 0)
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return r;
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if (!audit_session_is_valid(u))
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return -ENODATA;
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*id = u;
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return 0;
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}
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int audit_loginuid_from_pid(pid_t pid, uid_t *uid) {
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_cleanup_free_ char *s = NULL;
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const char *p;
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uid_t u;
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int r;
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assert(uid);
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p = procfs_file_alloca(pid, "loginuid");
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r = read_one_line_file(p, &s);
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if (r < 0)
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return r;
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r = parse_uid(s, &u);
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if (r == -ENXIO) /* the UID was -1 */
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return -ENODATA;
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if (r < 0)
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return r;
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*uid = u;
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return 0;
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}
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static int try_audit_request(int fd) {
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struct iovec iov;
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struct msghdr mh;
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ssize_t n;
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assert(fd >= 0);
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struct {
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struct nlmsghdr hdr;
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struct nlmsgerr err;
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} _packed_ msg = {
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.hdr.nlmsg_len = NLMSG_LENGTH(0),
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.hdr.nlmsg_type = AUDIT_GET_FEATURE,
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.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK,
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};
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iov = IOVEC_MAKE(&msg, msg.hdr.nlmsg_len);
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mh = (struct msghdr) {
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.msg_iov = &iov,
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.msg_iovlen = 1,
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};
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if (sendmsg(fd, &mh, MSG_NOSIGNAL) < 0)
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return -errno;
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iov.iov_len = sizeof(msg);
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n = recvmsg_safe(fd, &mh, 0);
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if (n < 0)
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return -errno;
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if (n != NLMSG_LENGTH(sizeof(struct nlmsgerr)))
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return -EIO;
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if (msg.hdr.nlmsg_type != NLMSG_ERROR)
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return -EINVAL;
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return msg.err.error;
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}
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bool use_audit(void) {
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static int cached_use = -1;
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int r;
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if (cached_use < 0) {
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int fd;
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fd = socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK, NETLINK_AUDIT);
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if (fd < 0) {
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cached_use = !IN_SET(errno, EAFNOSUPPORT, EPROTONOSUPPORT, EPERM);
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if (!cached_use)
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log_debug_errno(errno, "Won't talk to audit: %m");
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} else {
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/* If we try and use the audit fd but get -ECONNREFUSED, it is because
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* we are not in the initial user namespace, and the kernel does not
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* have support for audit outside of the initial user namespace
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* (see https://elixir.bootlin.com/linux/latest/C/ident/audit_netlink_ok).
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*
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* If we receive any other error, do not disable audit because we are not
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* sure that the error indicates that audit will not work in general. */
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r = try_audit_request(fd);
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if (r < 0) {
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cached_use = r != -ECONNREFUSED;
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log_debug_errno(r, cached_use ?
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"Failed to make request on audit fd, ignoring: %m" :
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"Won't talk to audit: %m");
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} else
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cached_use = true;
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safe_close(fd);
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}
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}
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return cached_use;
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}
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