CVE-2016-6515: Denial of service via very long passwords (#1364936)

related to user enumeration.

Upstream: https://github.com/openssh/openssh-portable/commit/fcd135c9df

openssh-7.2p2-user-enumeration.patch

@@ -212,4 +212,44 @@ index 451de78..465b5a7 100644
  	if (sshpam_err == PAM_SUCCESS && authctxt->valid) {
  		debug("PAM: password authentication accepted for %.100s",
  		    authctxt->user);
+From fcd135c9df440bcd2d5870405ad3311743d78d97 Mon Sep 17 00:00:00 2001
+From: "dtucker@openbsd.org" <dtucker@openbsd.org>
+Date: Thu, 21 Jul 2016 01:39:35 +0000
+Subject: [PATCH] upstream commit
+
+Skip passwords longer than 1k in length so clients can't
+easily DoS sshd by sending very long passwords, causing it to spend CPU
+hashing them. feedback djm@, ok markus@.
+
+Brought to our attention by tomas.kuthan at oracle.com, shilei-c at
+360.cn and coredump at autistici.org
+
+Upstream-ID: d0af7d4a2190b63ba1d38eec502bc4be0be9e333
+---
+ auth-passwd.c | 7 ++++++-
+ 1 file changed, 6 insertions(+), 1 deletion(-)
+
+diff --git a/auth-passwd.c b/auth-passwd.c
+index 530b5d4..996c2cf 100644
+--- a/auth-passwd.c
++++ b/auth-passwd.c
+@@ -66,6 +66,8 @@ extern login_cap_t *lc;
+ #define DAY		(24L * 60 * 60) /* 1 day in seconds */
+ #define TWO_WEEKS	(2L * 7 * DAY)	/* 2 weeks in seconds */
+ 
++#define MAX_PASSWORD_LEN	1024
++
+ void
+ disable_forwarding(void)
+ {
+@@ -87,6 +89,9 @@ auth_password(Authctxt *authctxt, const char *password)
+ 	static int expire_checked = 0;
+ #endif
+ 
++	if (strlen(password) > MAX_PASSWORD_LEN)
++		return 0;
++
+ #ifndef HAVE_CYGWIN
+ 	if (pw->pw_uid == 0 && options.permit_root_login != PERMIT_YES)
+ 		ok = 0;