From 0e7aa6bf9e0a7a91136353a3d6fe6a90d2047fc0 Mon Sep 17 00:00:00 2001
From: Yi Li <yi1.li@intel.com>
Date: Mon, 26 Sep 2022 08:24:33 +0800
Subject: [PATCH] CryptoPkg: Fix pem heap-buffer-overflow due to BIO_snprintf()

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4075

Fake BIO_snprintf() does not actually print anything to buf,
it should return -1 as error.
0 will be considered a correct return value, the consumer may think that
the buf is valid and parse the buffer.
please refer to bugzilla link for details.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Xiaoyu Lu <xiaoyu1.lu@intel.com>
Cc: Guomin Jiang <guomin.jiang@intel.com>

Signed-off-by: Yi Li <yi1.li@intel.com>
Reviewed-by: Jiewen Yao <Jiewen.yao@intel.com>
---
 CryptoPkg/Library/BaseCryptLib/SysCall/CrtWrapper.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/CryptoPkg/Library/BaseCryptLib/SysCall/CrtWrapper.c b/CryptoPkg/Library/BaseCryptLib/SysCall/CrtWrapper.c
index c1fc33538f..b65d29485b 100644
--- a/CryptoPkg/Library/BaseCryptLib/SysCall/CrtWrapper.c
+++ b/CryptoPkg/Library/BaseCryptLib/SysCall/CrtWrapper.c
@@ -494,7 +494,9 @@ BIO_snprintf (
   ...
   )
 {
-  return 0;
+  // Because the function does not actually print anything to buf, it returns -1 as error.
+  // Otherwise, the consumer may think that the buf is valid and parse the buffer.
+  return -1;
 }
 
 #ifdef __GNUC__