Re: [PATCH] CryptoPkg/BaseCryptLib: fix NULL dereference (CVE-2019-14584)


Yao, Jiewen
 

Reviewed-by: Jiewen Yao <Jiewen.yao@...>

-----Original Message-----
From: Wang, Jian J <jian.j.wang@...>
Sent: Friday, October 16, 2020 1:15 PM
To: devel@edk2.groups.io
Cc: Lu, XiaoyuX <xiaoyux.lu@...>; Jiang, Guomin
<guomin.jiang@...>; Yao, Jiewen <jiewen.yao@...>; Laszlo
Ersek <lersek@...>
Subject: [PATCH] CryptoPkg/BaseCryptLib: fix NULL dereference (CVE-2019-
14584)

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1914



AuthenticodeVerify() calls OpenSSLs d2i_PKCS7() API to parse asn encoded

signed authenticode pkcs#7 data. when this successfully returns, a type

check is done by calling PKCS7_type_is_signed() and then

Pkcs7->d.sign->contents->type is used. It is possible to construct an asn1

blob that successfully decodes and have d2i_PKCS7() return a valid pointer

and have PKCS7_type_is_signed() also return success but have Pkcs7->d.sign

be a NULL pointer.



Looking at how PKCS7_verify() [inside of OpenSSL] implements checking for

pkcs7 structs it does the following:

- call PKCS7_type_is_signed()

- call PKCS7_get_detached()

Looking into how PKCS7_get_detatched() is implemented, it checks to see if

p7->d.sign is NULL or if p7->d.sign->contents->d.ptr is NULL.



As such, the fix is to do the same as OpenSSL after calling d2i_PKCS7().

- Add call to PKS7_get_detached() to existing error handling



Cc: Xiaoyu Lu <xiaoyux.lu@...>

Cc: Guomin Jiang <guomin.jiang@...>

Cc: Jiewen Yao <jiewen.yao@...>

Cc: Laszlo Ersek <lersek@...>
Signed-off-by: Jian J Wang <jian.j.wang@...>

Reviewed-by: Laszlo Ersek <lersek@...>
---
CryptoPkg/Library/BaseCryptLib/Pk/CryptAuthenticode.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/CryptoPkg/Library/BaseCryptLib/Pk/CryptAuthenticode.c
b/CryptoPkg/Library/BaseCryptLib/Pk/CryptAuthenticode.c
index 2772b1e2be..ae0ee61fb6 100644
--- a/CryptoPkg/Library/BaseCryptLib/Pk/CryptAuthenticode.c
+++ b/CryptoPkg/Library/BaseCryptLib/Pk/CryptAuthenticode.c
@@ -9,7 +9,7 @@
AuthenticodeVerify() will get PE/COFF Authenticode and will do basic check
for

data structure.



-Copyright (c) 2011 - 2015, Intel Corporation. All rights reserved.<BR>

+Copyright (c) 2011 - 2019, Intel Corporation. All rights reserved.<BR>

SPDX-License-Identifier: BSD-2-Clause-Patent



**/

@@ -100,7 +100,7 @@ AuthenticodeVerify (
//

// Check if it's PKCS#7 Signed Data (for Authenticode Scenario)

//

- if (!PKCS7_type_is_signed (Pkcs7)) {

+ if (!PKCS7_type_is_signed (Pkcs7) || PKCS7_get_detached (Pkcs7)) {

goto _Exit;

}



--
2.19.0.windows.1

Join devel@edk2.groups.io to automatically receive all group messages.