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-rw-r--r--src/login/pam_elogind.c28
1 files changed, 16 insertions, 12 deletions
diff --git a/src/login/pam_elogind.c b/src/login/pam_elogind.c
index 63cbbbc1d..bb6da2aac 100644
--- a/src/login/pam_elogind.c
+++ b/src/login/pam_elogind.c
@@ -381,28 +381,32 @@ _public_ PAM_EXTERN int pam_sm_open_session(
tty = strempty(tty);
if (strchr(tty, ':')) {
- /* A tty with a colon is usually an X11 display,
- * placed there to show up in utmp. We rearrange
- * things and don't pretend that an X display was a
- * tty. */
-
+ /* A tty with a colon is usually an X11 display, placed there to show up in utmp. We rearrange things
+ * and don't pretend that an X display was a tty. */
if (isempty(display))
display = tty;
tty = NULL;
+
} else if (streq(tty, "cron")) {
- /* cron has been setting PAM_TTY to "cron" for a very
- * long time and it probably shouldn't stop doing that
- * for compatibility reasons. */
+ /* cron is setting PAM_TTY to "cron" for some reason (the commit carries no information why, but
+ * probably because it wants to set it to something as pam_time/pam_access/… require PAM_TTY to be set
+ * (as they otherwise even try to update it!) — but cron doesn't actually allocate a TTY for its forked
+ * off processes.) */
type = "unspecified";
class = "background";
tty = NULL;
+
} else if (streq(tty, "ssh")) {
- /* ssh has been setting PAM_TTY to "ssh" for a very
- * long time and probably shouldn't stop doing that
- * for compatibility reasons. */
+ /* ssh has been setting PAM_TTY to "ssh" (for the same reason as cron does this, see above. For further
+ * details look for "PAM_TTY_KLUDGE" in the openssh sources). */
type ="tty";
class = "user";
- tty = NULL;
+ tty = NULL; /* This one is particularly sad, as this means that ssh sessions — even though usually
+ * associated with a pty — won't be tracked by their tty in logind. This is because ssh
+ * does the PAM session registration early for new connections, and registers a pty only
+ * much later (this is because it doesn't know yet if it needs one at all, as whether to
+ * register a pty or not is negotiated much later in the protocol). */
+
} else
/* Chop off leading /dev prefix that some clients specify, but others do not. */
tty = skip_dev_prefix(tty);