From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001

From: Darren Kenny <darren.kenny@oracle.com>

Date: Tue, 3 Nov 2020 16:43:37 +0000

Subject: [PATCH] libgcrypt/mpi: Fix possible unintended sign extension

The array of unsigned char gets promoted to a signed 32-bit int before

it is finally promoted to a size_t. There is the possibility that this

may result in the signed-bit being set for the intermediate signed

32-bit int. We should ensure that the promotion is to the correct type

before we bitwise-OR the values.

Fixes: CID 96697

Signed-off-by: Darren Kenny <darren.kenny@oracle.com>

Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

---

 grub-core/lib/libgcrypt/mpi/mpicoder.c | 2 +-

 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/grub-core/lib/libgcrypt/mpi/mpicoder.c b/grub-core/lib/libgcrypt/mpi/mpicoder.c

index a3435ed142a..7ecad27b23a 100644

--- a/grub-core/lib/libgcrypt/mpi/mpicoder.c

+++ b/grub-core/lib/libgcrypt/mpi/mpicoder.c

@@ -458,7 +458,7 @@ gcry_mpi_scan (struct gcry_mpi **ret_mpi, enum gcry_mpi_format format,

       if (len && len < 4)

         return gcry_error (GPG_ERR_TOO_SHORT);

-      n = (s[0] << 24 | s[1] << 16 | s[2] << 8 | s[3]);

+      n = ((size_t)s[0] << 24 | (size_t)s[1] << 16 | (size_t)s[2] << 8 | (size_t)s[3]);

       s += 4;

       if (len)

         len -= 4;