-----Original Message-----
From: Jan Bobek <jbobek@...>
Sent: Tuesday, January 17, 2023 6:30 AM
To: Yao, Jiewen <jiewen.yao@...>
Cc: devel@edk2.groups.io; Jeff Brasen <jbrasen@...>; Girish
Mahadevan <gmahadevan@...>; Wang, Jian J
<jian.j.wang@...>; Xu, Min M <min.m.xu@...>
Subject: Re: [edk2-devel] [PATCH 1/1] SecurityPkg/AuthVariableLib: Check
SHA-256 OID with ContentInfo present

Hi
That is good catch!
My apology to miss it before.

1) Please file a bugzilla (https://bugzilla.tianocore.org/) to record the issue

and associate to the patch.

Filed bug 4305 [1]. Sorry for the delay, I didn't get my bugzilla
credentials until late last week.

2) Would you please share with us that how you discover the issue?
For example, any real use case to include ContentInfo? If yes, please share

a URL.

Or this is just a purely spec compliance fix ?

3) Please describe how you validate the fix.
If possible, would you please share your test case?

I believe both of these answered / included in the bug description.

4) Since the new code is handling ContentInfo structure is present, I believe

we need also check if the ContentInfo structure is valid.

For example:
============
c SignedData.contentInfo.contentType shall be set to id-data
d SignedData.contentInfo.content shall be absent
============
What do you think?

I think you're talking about the ContentInfo structure that's part of
the SignedData structure, but the real problem is with ContentInfo
structure that _wraps_ the SignedData structure. More info in the bug
description.

Also, is it customary to continue the discussion here on edk2-devel or
in the bug comments on bugzilla?

-Jan

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

-----Original Message-----
From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Jan
Bobek via groups.io
Sent: Wednesday, January 4, 2023 6:30 AM
To: devel@edk2.groups.io
Cc: Jeff Brasen <jbrasen@...>; Girish Mahadevan
<gmahadevan@...>; Jan Bobek <jbobek@...>; Yao, Jiewen
<jiewen.yao@...>; Wang, Jian J <jian.j.wang@...>; Xu, Min M
<min.m.xu@...>
Subject: Re: [edk2-devel] [PATCH 1/1] SecurityPkg/AuthVariableLib: Check
SHA-256 OID with ContentInfo present

Anothing ping. Comments/reviews/merge highly appreciated.

Thank you,
-Jan

Jan Bobek writes:

Ping. Can I get a review and/or some comments on this patch, please?

Thanks,
-Jan

Jan Bobek writes:

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@...>
Cc: Jian J Wang <jian.j.wang@...>
Cc: Min Xu <min.m.xu@...>
Signed-off-by: Jan Bobek <jbobek@...>
---
.../Library/AuthVariableLib/AuthService.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/SecurityPkg/Library/AuthVariableLib/AuthService.c

b/SecurityPkg/Library/AuthVariableLib/AuthService.c

index 054ee4d1d988..de8baccab410 100644
--- a/SecurityPkg/Library/AuthVariableLib/AuthService.c
+++ b/SecurityPkg/Library/AuthVariableLib/AuthService.c
@@ -1933,15 +1933,19 @@ 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.
//
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;
}
}

Ping. Can I get a review and/or some comments on this patch, please?

Thanks,
-Jan

Jan Bobek writes:

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@...>
Cc: Jian J Wang <jian.j.wang@...>
Cc: Min Xu <min.m.xu@...>
Signed-off-by: Jan Bobek <jbobek@...>
---
.../Library/AuthVariableLib/AuthService.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/SecurityPkg/Library/AuthVariableLib/AuthService.c b/SecurityPkg/Library/AuthVariableLib/AuthService.c
index 054ee4d1d988..de8baccab410 100644
--- a/SecurityPkg/Library/AuthVariableLib/AuthService.c
+++ b/SecurityPkg/Library/AuthVariableLib/AuthService.c
@@ -1933,15 +1933,19 @@ 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.
//
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;
}
}

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@...>
Cc: Jian J Wang <jian.j.wang@...>
Cc: Min Xu <min.m.xu@...>
Signed-off-by: Jan Bobek <jbobek@...>
---
.../Library/AuthVariableLib/AuthService.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/SecurityPkg/Library/AuthVariableLib/AuthService.c b/SecurityPkg/Library/AuthVariableLib/AuthService.c
index 054ee4d1d988..de8baccab410 100644
--- a/SecurityPkg/Library/AuthVariableLib/AuthService.c
+++ b/SecurityPkg/Library/AuthVariableLib/AuthService.c
@@ -1933,15 +1933,19 @@ 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.
//
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;
}
}