grub2: Fix CVE-2015-8370

This CVE is a culmination of multiple integer overflow issues that cause
multiple issues like Denial of Service and authentication bypass.

More info: https://nvd.nist.gov/vuln/detail/CVE-2015-8370

Taken from Fedora.

Signed-off-by: Rosen Penev <[email protected]>

package/boot/grub2/Makefile

@@ -11,7 +11,7 @@ include $(INCLUDE_DIR)/kernel.mk
 PKG_NAME:=grub
 PKG_CPE_ID:=cpe:/a:gnu:grub2
 PKG_VERSION:=2.02
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.xz
 PKG_SOURCE_URL:=@GNU/grub

package/boot/grub2/patches/300-CVE-2015-8370.patch

@@ -0,0 +1,44 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Hector Marco-Gisbert <[email protected]>
+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 <[email protected]>
+Signed-off-by: Ismael Ripoll-Ripoll <[email protected]>
+---
+ 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 ca334d5a40e..e6c78d16d39 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 6be678c0de1..c35ce972473 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)
+ 	    {