Re: [edk2-devel] [PATCH] CryptoPkg/BaseCryptLib: fix NULL dereference (CVE-2019-14584)

["Wang, Jian J" <jian.j.wang@intel.com>]

Laszlo,


> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Laszlo Ersek
> Sent: Tuesday, October 20, 2020 3:13 AM
> To: devel@edk2.groups.io; Wang, Jian J <jian.j.wang@intel.com>
> Cc: Lu, XiaoyuX <xiaoyux.lu@intel.com>; Jiang, Guomin
> <guomin.jiang@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>
> Subject: Re: [edk2-devel] [PATCH] CryptoPkg/BaseCryptLib: fix NULL
> dereference (CVE-2019-14584)
> 
> On 10/16/20 07:14, Wang, Jian J wrote:
> > 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@intel.com>
> > Cc: Guomin Jiang <guomin.jiang@intel.com>
> > Cc: Jiewen Yao <jiewen.yao@intel.com>
> > Cc: Laszlo Ersek <lersek@redhat.com>
> > Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
> > Reviewed-by: Laszlo Ersek <lersek@redhat.com>
> > ---
> >  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
> >
> >  **/
> 
> It's probably best to bump the (C) date to 2020; if you must update the
> (C) line in the first place.
> 
> Otherwise, this patch seems identical to what I reviewed in
> <https://bugzilla.tianocore.org/show_bug.cgi?id=1914#c6>, so my R-b stands.
> 

Thanks for catching this. I'll update it before pushing.

Regards,
Jian

> Thanks
> Laszlo
> 
> > @@ -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;
> >    }
> >
> >
> 
> 
> 
> 
>