[PATCH] Fix security issue when reading username and password

[Javier Martinez Canillas]

From: Hector Marco-Gisbert <address@hidden>

  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 <address@hidden>
Signed-off-by: Ismael Ripoll-Ripoll <address@hidden>
Signed-off-by: Javier Martinez Canillas <address@hidden>
---

 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)
            {
-- 
2.21.0