From: Sam Hartman <hartmans@debian.org>
Date: Mon, 11 Sep 2023 14:00:42 -0600
Subject: update-motd

Provide a more dynamic MOTD, based on the short-lived update-motd project.

Authors: Dustin Kirkland <kirkland@canonical.com>

Last-Update: 2019-02-12
Forwarded: no
Bug-Ubuntu: https://bugs.launchpad.net/bugs/399071
---
 modules/pam_motd/pam_motd.8.xml | 11 +++++++++++
 modules/pam_motd/pam_motd.c     | 18 ++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/modules/pam_motd/pam_motd.8.xml b/modules/pam_motd/pam_motd.8.xml
index 2fc5310..8369779 100644
--- a/modules/pam_motd/pam_motd.8.xml
+++ b/modules/pam_motd/pam_motd.8.xml
@@ -112,6 +112,17 @@
           </para>
         </listitem>
       </varlistentry>
+      <varlistentry>
+        <term>
+          <option>noupdate</option>
+        </term>
+        <listitem>
+          <para>
+            Don't run the scripts in <filename>/etc/update-motd.d</filename>
+            to refresh the motd file.
+          </para>
+        </listitem>
+      </varlistentry>
     </variablelist>
     <para>
       When no options are given, the default behavior applies for both
diff --git a/modules/pam_motd/pam_motd.c b/modules/pam_motd/pam_motd.c
index 89b2595..e6ce874 100644
--- a/modules/pam_motd/pam_motd.c
+++ b/modules/pam_motd/pam_motd.c
@@ -387,6 +387,7 @@ int pam_sm_open_session(pam_handle_t *pamh, int flags,
 			int argc, const char **argv)
 {
     int retval = PAM_IGNORE;
+    int do_update = 1;
     const char *motd_path = NULL;
     char *motd_path_copy = NULL;
     size_t num_motd_paths = 0;
@@ -396,6 +397,7 @@ int pam_sm_open_session(pam_handle_t *pamh, int flags,
     size_t num_motd_dir_paths = 0;
     char **motd_dir_path_split = NULL;
     int report_missing;
+    struct stat st;
 
     if (flags & PAM_SILENT) {
 	return retval;
@@ -425,6 +427,9 @@ int pam_sm_open_session(pam_handle_t *pamh, int flags,
 			   "motd_dir= specification missing argument - ignored");
 	    }
 	}
+	else if (!strcmp(*argv,"noupdate")) {
+		do_update = 0;
+	}
 	else
 	    pam_syslog(pamh, LOG_ERR, "unknown option: %s", *argv);
     }
@@ -437,6 +442,19 @@ int pam_sm_open_session(pam_handle_t *pamh, int flags,
 	report_missing = 1;
     }
 
+    /* Run the update-motd dynamic motd scripts, outputting to /run/motd.dynamic.
+       This will be displayed only when calling pam_motd with
+       motd=/run/motd.dynamic; current /etc/pam.d/login and /etc/pam.d/sshd
+       display both this file and /etc/motd. */
+    if (do_update && (stat("/etc/update-motd.d", &st) == 0)
+        && S_ISDIR(st.st_mode))
+    {
+       mode_t old_mask = umask(0022);
+       if (!system("/usr/bin/env -i PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin run-parts --lsbsysinit /etc/update-motd.d > /run/motd.dynamic.new"))
+           rename("/run/motd.dynamic.new", "/run/motd.dynamic");
+       umask(old_mask);
+    }
+
     if (motd_path != NULL) {
 	motd_path_copy = strdup(motd_path);
     }