[openssh-commits] [openssh] 02/09: upstream: add a random amount of time (up to 4 seconds) to the

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djm pushed a commit to branch master
in repository openssh.

commit 487faaed8f3bb9ffb19e8f807a3da72895b16421
Author: dlg at openbsd.org <dlg at openbsd.org>
AuthorDate: Wed Jul 31 12:00:18 2024 +0000

    upstream: add a random amount of time (up to 4 seconds) to the
    
    grace login time.
    
    ok deraadt@ djm@
    
    OpenBSD-Commit-ID: abd3c57aaa5861517529b322df79b6be35ee67f4
---
 sshd-session.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/sshd-session.c b/sshd-session.c
index 1060ff7d..d089f10d 100644
--- a/sshd-session.c
+++ b/sshd-session.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshd-session.c,v 1.5 2024/07/08 03:04:34 djm Exp $ */
+/* $OpenBSD: sshd-session.c,v 1.6 2024/07/31 12:00:18 dlg Exp $ */
 /*
  * SSH2 implementation:
  * Privilege Separation:
@@ -882,6 +882,7 @@ main(int ac, char **av)
 	struct connection_info *connection_info = NULL;
 	sigset_t sigmask;
 	uint64_t timing_secret = 0;
+	struct itimerval itv;
 
 	sigemptyset(&sigmask);
 	sigprocmask(SIG_SETMASK, &sigmask, NULL);
@@ -1276,8 +1277,17 @@ main(int ac, char **av)
 	 * are about to discover the bug.
 	 */
 	ssh_signal(SIGALRM, grace_alarm_handler);
-	if (!debug_flag)
-		alarm(options.login_grace_time);
+	if (!debug_flag && options.login_grace_time > 0) {
+		int ujitter = arc4random_uniform(4 * 1000000);
+
+		timerclear(&itv.it_interval);
+		itv.it_value.tv_sec = options.login_grace_time;
+		itv.it_value.tv_sec += ujitter / 1000000;
+		itv.it_value.tv_usec = ujitter % 1000000; 
+
+		if (setitimer(ITIMER_REAL, &itv, NULL) == -1)
+			fatal("login grace time setitimer failed");
+	}
 
 	if ((r = kex_exchange_identification(ssh, -1,
 	    options.version_addendum)) != 0)
@@ -1321,7 +1331,10 @@ main(int ac, char **av)
 	 * Cancel the alarm we set to limit the time taken for
 	 * authentication.
 	 */
-	alarm(0);
+	timerclear(&itv.it_interval);
+	timerclear(&itv.it_value);
+	if (setitimer(ITIMER_REAL, &itv, NULL) == -1)
+		fatal("login grace time clear failed");
 	ssh_signal(SIGALRM, SIG_DFL);
 	authctxt->authenticated = 1;
 	if (startup_pipe != -1) {

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