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-rw-r--r--src/basic/audit-util.c146
1 files changed, 146 insertions, 0 deletions
diff --git a/src/basic/audit-util.c b/src/basic/audit-util.c
new file mode 100644
index 0000000..bf96e08
--- /dev/null
+++ b/src/basic/audit-util.c
@@ -0,0 +1,146 @@
+/* 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;
+}