#
# This is to fix a keyboard-interactive authentication brute force
# vulnerability (MaxAuthTries bypass). A CVE number (CVE-2015-5600) has been
# reserved for this problem, but not officially issued yet. This fix came from
# OpenSSH upstream, which will be included in the future OpenSSH 7.0p1 release.
# When we upgrade OpenSSH to 7.0 in the future, we will remove this patch.
#
--- orig/auth2-chall.c	Fri Jul 24 17:36:37 2015
+++ new/auth2-chall.c	Fri Jul 24 17:47:21 2015
@@ -83,6 +83,7 @@
 	void *ctxt;
 	KbdintDevice *device;
 	u_int nreq;
+        u_int devices_done;
 };
 
 #ifdef USE_PAM
@@ -169,11 +170,15 @@
 		if (len == 0)
 			break;
 		for (i = 0; devices[i]; i++) {
-			if (!auth2_method_allowed(authctxt,
+			if ((kbdintctxt->devices_done & (1 << i)) != 0 ||
+			    !auth2_method_allowed(authctxt,
 			    "keyboard-interactive", devices[i]->name))
 				continue;
-			if (strncmp(kbdintctxt->devices, devices[i]->name, len) == 0)
+			if (strncmp(kbdintctxt->devices, devices[i]->name,
+			    len) == 0) {
 				kbdintctxt->device = devices[i];
+				kbdintctxt->devices_done |= 1 << i;
+			}
 		}
 		t = kbdintctxt->devices;
 		kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL;