From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Hector Marco-Gisbert <hecmargi@upv.es>
Date: Fri, 13 Nov 2015 16:21:09 +0100
Subject: [PATCH] Fix security issue when reading username and password

  This patch fixes two integer underflows at:
    * grub-core/lib/crypto.c
    * grub-core/normal/auth.c

Resolves: CVE-2015-8370

Signed-off-by: Hector Marco-Gisbert <hecmargi@upv.es>
Signed-off-by: Ismael Ripoll-Ripoll <iripoll@disca.upv.es>
---
 grub-core/lib/crypto.c  | 2 +-
 grub-core/normal/auth.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/grub-core/lib/crypto.c b/grub-core/lib/crypto.c
index ca334d5a4..e6c78d16d 100644
--- a/grub-core/lib/crypto.c
+++ b/grub-core/lib/crypto.c
@@ -468,7 +468,7 @@ grub_password_get (char buf[], unsigned buf_size)
 	  break;
 	}
 
-      if (key == '\b')
+      if (key == '\b' && cur_len)
 	{
 	  if (cur_len)
 	    cur_len--;
diff --git a/grub-core/normal/auth.c b/grub-core/normal/auth.c
index 6be678c0d..c35ce9724 100644
--- a/grub-core/normal/auth.c
+++ b/grub-core/normal/auth.c
@@ -172,7 +172,7 @@ grub_username_get (char buf[], unsigned buf_size)
 	  break;
 	}
 
-      if (key == GRUB_TERM_BACKSPACE)
+      if (key == GRUB_TERM_BACKSPACE && cur_len)
 	{
 	  if (cur_len)
 	    {