6ded19558a
Add the comments to address security problems in the Pkcs7Verify Protocol per UEFI 2.7 updates. The Pkcs7Verifier function VerifySignature() has problematic use cases where it might be used to unwittingly bypass security checks. The specific problem is that if the supplied hash is a different algorithm from the blacklist hash, the hash will be approved even if it should have been denied. The added comments place a strong warning about the problem. It is possible to use the protocol reliably, either by agreeing a hash to use for all time (like sha256) or by looping over all supported hashes when using the protocol. Cc: Chao Zhang <chao.b.zhang@intel.com> Cc: James Bottomley <James.Bottomley@HansenPartnership.com> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Qin Long <qin.long@intel.com> Reviewed-by: Chao Zhang <chao.b.zhang@intel.com>
230 lines
14 KiB
C
230 lines
14 KiB
C
/** @file
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EFI_PKCS7_VERIFY_PROTOCOL as defined in UEFI 2.5.
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The EFI_PKCS7_VERIFY_PROTOCOL is used to verify data signed using PKCS#7
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formatted authentication. The PKCS#7 data to be verified must be binary
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DER encoded.
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PKCS#7 is a general-purpose cryptographic standard (defined by RFC2315,
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available at http://tools.ietf.org/html/rfc2315).
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Copyright (c) 2015 - 2017, Intel Corporation. All rights reserved.<BR>
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This program and the accompanying materials are licensed and made available under
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the terms and conditions of the BSD License that accompanies this distribution.
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The full text of the license may be found at
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http://opensource.org/licenses/bsd-license.php.
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THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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**/
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#ifndef __EFI_PKCS7_VERIFY_PROTOCOL_H__
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#define __EFI_PKCS7_VERIFY_PROTOCOL_H__
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#include <Guid/ImageAuthentication.h>
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///
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/// Global ID for the PKCS7 Verification Protocol
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///
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#define EFI_PKCS7_VERIFY_PROTOCOL_GUID \
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{ \
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0x47889fb2, 0xd671, 0x4fab, {0xa0, 0xca, 0xdf, 0x0e, 0x44, 0xdf, 0x70, 0xd6 } \
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}
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typedef struct _EFI_PKCS7_VERIFY_PROTOCOL EFI_PKCS7_VERIFY_PROTOCOL;
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/**
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Processes a buffer containing binary DER-encoded PKCS7 signature.
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The signed data content may be embedded within the buffer or separated. Funtion
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verifies the signature of the content is valid and signing certificate was not
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revoked and is contained within a list of trusted signers.
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@param[in] This Pointer to EFI_PKCS7_VERIFY_PROTOCOL instance.
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@param[in] SignedData Points to buffer containing ASN.1 DER-encoded PKCS7
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signature.
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@param[in] SignedDataSize The size of SignedData buffer in bytes.
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@param[in] InData In case of detached signature, InData points to
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buffer containing the raw message data previously
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signed and to be verified by function. In case of
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SignedData containing embedded data, InData must be
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NULL.
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@param[in] InDataSize When InData is used, the size of InData buffer in
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bytes. When InData is NULL. This parameter must be
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0.
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@param[in] AllowedDb Pointer to a list of pointers to EFI_SIGNATURE_LIST
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structures. The list is terminated by a null
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pointer. The EFI_SIGNATURE_LIST structures contain
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lists of X.509 certificates of approved signers.
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Function recognizes signer certificates of type
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EFI_CERT_X509_GUID. Any hash certificate in AllowedDb
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list is ignored by this function. Function returns
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success if signer of the buffer is within this list
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(and not within RevokedDb). This parameter is
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required.
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@param[in] RevokedDb Optional pointer to a list of pointers to
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EFI_SIGNATURE_LIST structures. The list is terminated
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by a null pointer. List of X.509 certificates of
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revoked signers and revoked file hashes. Except as
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noted in description of TimeStampDb signature
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verification will always fail if the signer of the
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file or the hash of the data component of the buffer
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is in RevokedDb list. This list is optional and
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caller may pass Null or pointer to NULL if not
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required.
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@param[in] TimeStampDb Optional pointer to a list of pointers to
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EFI_SIGNATURE_LIST structures. The list is terminated
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by a null pointer. This parameter can be used to pass
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a list of X.509 certificates of trusted time stamp
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signers. This list is optional and caller must pass
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Null or pointer to NULL if not required.
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@param[out] Content On input, points to an optional caller-allocated
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buffer into which the function will copy the content
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portion of the file after verification succeeds.
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This parameter is optional and if NULL, no copy of
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content from file is performed.
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@param[in,out] ContentSize On input, points to the size in bytes of the optional
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buffer Content previously allocated by caller. On
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output, if the verification succeeds, the value
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referenced by ContentSize will contain the actual
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size of the content from signed file. If ContentSize
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indicates the caller-allocated buffer is too small
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to contain content, an error is returned, and
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ContentSize will be updated with the required size.
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This parameter must be 0 if Content is Null.
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@retval EFI_SUCCESS Content signature was verified against hash of
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content, the signer's certificate was not found in
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RevokedDb, and was found in AllowedDb or if in signer
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is found in both AllowedDb and RevokedDb, the
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signing was allowed by reference to TimeStampDb as
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described above, and no hash matching content hash
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was found in RevokedDb.
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@retval EFI_SECURITY_VIOLATION The SignedData buffer was correctly formatted but
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signer was in RevokedDb or not in AllowedDb. Also
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returned if matching content hash found in RevokedDb.
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@retval EFI_COMPROMISED_DATA Calculated hash differs from signed hash.
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@retval EFI_INVALID_PARAMETER SignedData is NULL or SignedDataSize is zero.
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AllowedDb is NULL.
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@retval EFI_INVALID_PARAMETER Content is not NULL and ContentSize is NULL.
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@retval EFI_ABORTED Unsupported or invalid format in TimeStampDb,
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RevokedDb or AllowedDb list contents was detected.
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@retval EFI_NOT_FOUND Content not found because InData is NULL and no
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content embedded in SignedData.
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@retval EFI_UNSUPPORTED The SignedData buffer was not correctly formatted
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for processing by the function.
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@retval EFI_UNSUPPORTED Signed data embedded in SignedData but InData is not
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NULL.
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@retval EFI_BUFFER_TOO_SMALL The size of buffer indicated by ContentSize is too
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small to hold the content. ContentSize updated to
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required size.
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**/
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typedef
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EFI_STATUS
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(EFIAPI *EFI_PKCS7_VERIFY_BUFFER) (
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IN EFI_PKCS7_VERIFY_PROTOCOL *This,
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IN VOID *SignedData,
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IN UINTN SignedDataSize,
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IN VOID *InData OPTIONAL,
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IN UINTN InDataSize,
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IN EFI_SIGNATURE_LIST **AllowedDb,
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IN EFI_SIGNATURE_LIST **RevokedDb OPTIONAL,
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IN EFI_SIGNATURE_LIST **TimeStampDb OPTIONAL,
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OUT VOID *Content OPTIONAL,
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IN OUT UINTN *ContentSize
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);
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/**
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Processes a buffer containing binary DER-encoded detached PKCS7 signature.
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The hash of the signed data content is calculated and passed by the caller. Function
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verifies the signature of the content is valid and signing certificate was not revoked
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and is contained within a list of trusted signers.
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Note: because this function uses hashes and the specification contains a variety of
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hash choices, you should be aware that the check against the RevokedDb list
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will improperly succeed if the signature is revoked using a different hash
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algorithm. For this reason, you should either cycle through all UEFI supported
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hashes to see if one is forbidden, or rely on a single hash choice only if the
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UEFI signature authority only signs and revokes with a single hash (at time
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of writing, this hash choice is SHA256).
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@param[in] This Pointer to EFI_PKCS7_VERIFY_PROTOCOL instance.
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@param[in] Signature Points to buffer containing ASN.1 DER-encoded PKCS
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detached signature.
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@param[in] SignatureSize The size of Signature buffer in bytes.
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@param[in] InHash InHash points to buffer containing the caller
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calculated hash of the data. The parameter may not
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be NULL.
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@param[in] InHashSize The size in bytes of InHash buffer.
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@param[in] AllowedDb Pointer to a list of pointers to EFI_SIGNATURE_LIST
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structures. The list is terminated by a null
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pointer. The EFI_SIGNATURE_LIST structures contain
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lists of X.509 certificates of approved signers.
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Function recognizes signer certificates of type
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EFI_CERT_X509_GUID. Any hash certificate in AllowedDb
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list is ignored by this function. Function returns
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success if signer of the buffer is within this list
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(and not within RevokedDb). This parameter is
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required.
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@param[in] RevokedDb Optional pointer to a list of pointers to
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EFI_SIGNATURE_LIST structures. The list is terminated
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by a null pointer. List of X.509 certificates of
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revoked signers and revoked file hashes. Signature
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verification will always fail if the signer of the
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file or the hash of the data component of the buffer
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is in RevokedDb list. This parameter is optional
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and caller may pass Null if not required.
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@param[in] TimeStampDb Optional pointer to a list of pointers to
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EFI_SIGNATURE_LIST structures. The list is terminated
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by a null pointer. This parameter can be used to pass
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a list of X.509 certificates of trusted time stamp
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counter-signers.
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@retval EFI_SUCCESS Signed hash was verified against caller-provided
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hash of content, the signer's certificate was not
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found in RevokedDb, and was found in AllowedDb or
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if in signer is found in both AllowedDb and
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RevokedDb, the signing was allowed by reference to
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TimeStampDb as described above, and no hash matching
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content hash was found in RevokedDb.
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@retval EFI_SECURITY_VIOLATION The SignedData buffer was correctly formatted but
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signer was in RevokedDb or not in AllowedDb. Also
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returned if matching content hash found in RevokedDb.
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@retval EFI_COMPROMISED_DATA Caller provided hash differs from signed hash. Or,
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caller and encrypted hash are different sizes.
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@retval EFI_INVALID_PARAMETER Signature is NULL or SignatureSize is zero. InHash
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is NULL or InHashSize is zero. AllowedDb is NULL.
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@retval EFI_ABORTED Unsupported or invalid format in TimeStampDb,
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RevokedDb or AllowedDb list contents was detected.
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@retval EFI_UNSUPPORTED The Signature buffer was not correctly formatted
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for processing by the function.
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**/
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typedef
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EFI_STATUS
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(EFIAPI *EFI_PKCS7_VERIFY_SIGNATURE) (
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IN EFI_PKCS7_VERIFY_PROTOCOL *This,
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IN VOID *Signature,
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IN UINTN SignatureSize,
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IN VOID *InHash,
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IN UINTN InHashSize,
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IN EFI_SIGNATURE_LIST **AllowedDb,
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IN EFI_SIGNATURE_LIST **RevokedDb OPTIONAL,
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IN EFI_SIGNATURE_LIST **TimeStampDb OPTIONAL
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);
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///
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/// The EFI_PKCS7_VERIFY_PROTOCOL is used to verify data signed using PKCS7
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/// structure. The PKCS7 data to be verified must be ASN.1 (DER) encoded.
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/// SHA256 must be supported as digest algorithm with RSA digest encryption.
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/// Support of other hash algorithms is optional.
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///
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struct _EFI_PKCS7_VERIFY_PROTOCOL {
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EFI_PKCS7_VERIFY_BUFFER VerifyBuffer;
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EFI_PKCS7_VERIFY_SIGNATURE VerifySignature;
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};
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extern EFI_GUID gEfiPkcs7VerifyProtocolGuid;
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#endif
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