tyler.durden
/
audk
mirror of https://github.com/acidanthera/audk.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

SecurityPkg/AuthVariableLib: Check SHA-256 OID with ContentInfo present 

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4305

Based on whether the DER-encoded ContentInfo structure is present in
authenticated SetVariable payload or not, the SHA-256 OID can be
located at different places.

UEFI specification explicitly states the driver shall support both
cases, but the old code assumed ContentInfo was not present and
incorrectly rejected authenticated variable updates when it were
present.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Signed-off-by: Jan Bobek <jbobek@nvidia.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
This commit is contained in:
Jan Bobek 2023-01-23 05:53:48 +08:00 committed by mergify[bot]
parent 7afef31b2b
commit 37d3eb026a
1 changed files with 42 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
SecurityPkg/Library/AuthVariableLib/AuthService.c
View File

@ -1925,7 +1925,7 @@ VerifyTimeBasedPayload (
// SignedData.digestAlgorithms shall contain the digest algorithm used when preparing the
// signature. Only a digest algorithm of SHA-256 is accepted.
//
// According to PKCS#7 Definition:
// According to PKCS#7 Definition (https://www.rfc-editor.org/rfc/rfc2315):
// SignedData ::= SEQUENCE {
// version Version,
// digestAlgorithms DigestAlgorithmIdentifiers,
@ -1933,15 +1933,49 @@ VerifyTimeBasedPayload (
// .... }
// The DigestAlgorithmIdentifiers can be used to determine the hash algorithm
// in VARIABLE_AUTHENTICATION_2 descriptor.
// This field has the fixed offset (+13) and be calculated based on two bytes of length encoding.
// This field has the fixed offset (+13) or (+32) based on whether the DER-encoded
// ContentInfo structure is present or not, and can be calculated based on two
// bytes of length encoding.
//
// Both condition can be handled in WrapPkcs7Data() in CryptPkcs7VerifyCommon.c.
//
// See below examples:
//
// 1. Without ContentInfo
// 30 82 0c da // SEQUENCE (5 element) (3294 BYTES) -- SignedData
// 02 01 01 // INTEGER 1 -- Version
// 31 0f // SET (1 element) (15 BYTES) -- DigestAlgorithmIdentifiers
// 30 0d // SEQUENCE (2 element) (13 BYTES) -- AlgorithmIdentifier
// 06 09 // OBJECT-IDENTIFIER (9 BYTES) -- algorithm
// 60 86 48 01 65 03 04 02 01 // sha256 [2.16.840.1.101.3.4.2.1]
// 05 00 // NULL (0 BYTES) -- parameters
//
// Example from: https://uefi.org/revocationlistfile
//
// 2. With ContentInfo
// 30 82 05 90 // SEQUENCE (1424 BYTES) -- ContentInfo
// 06 09 // OBJECT-IDENTIFIER (9 BYTES) -- ContentType
// 2a 86 48 86 f7 0d 01 07 02 // signedData [1.2.840.113549.1.7.2]
// a0 82 05 81 // CONTEXT-SPECIFIC CONSTRUCTED TAG 0 (1409 BYTES) -- content
// 30 82 05 7d // SEQUENCE (1405 BYTES) -- SignedData
// 02 01 01 // INTEGER 1 -- Version
// 31 0f // SET (1 element) (15 BYTES) -- DigestAlgorithmIdentifiers
// 30 0d // SEQUENCE (13 BYTES) -- AlgorithmIdentifier
// 06 09 // OBJECT-IDENTIFIER (9 BYTES) -- algorithm
// 60 86 48 01 65 03 04 02 01 // sha256 [2.16.840.1.101.3.4.2.1]
// 05 00 // NULL (0 BYTES) -- parameters
//
// Example generated with: https://wiki.archlinux.org/title/Unified_Extensible_Firmware_Interface/Secure_Boot#Manual_process
//
if ((Attributes & EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS) != 0) {
if (SigDataSize >= (13 + sizeof (mSha256OidValue))) {
if (((*(SigData + 1) & TWO_BYTE_ENCODE) != TWO_BYTE_ENCODE) ||
(CompareMem (SigData + 13, &mSha256OidValue, sizeof (mSha256OidValue)) != 0))
{
return EFI_SECURITY_VIOLATION;
}
if ( ( (SigDataSize >= (13 + sizeof (mSha256OidValue)))
&& ( ((*(SigData + 1) & TWO_BYTE_ENCODE) != TWO_BYTE_ENCODE)
|| (CompareMem (SigData + 13, &mSha256OidValue, sizeof (mSha256OidValue)) != 0)))
&& ( (SigDataSize >= (32 + sizeof (mSha256OidValue)))
&& ( ((*(SigData + 20) & TWO_BYTE_ENCODE) != TWO_BYTE_ENCODE)
|| (CompareMem (SigData + 32, &mSha256OidValue, sizeof (mSha256OidValue)) != 0))))
{
return EFI_SECURITY_VIOLATION;
}
}