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shim/shim-bsc1177315-verify-eku-codesign.patch

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From 6ff890bf0af9d37acc6ea8ad64f597060e8bb143 Mon Sep 17 00:00:00 2001
From: Gary Lin <glin@suse.com>
Date: Wed, 14 Oct 2020 14:31:12 +0800
Subject: [PATCH] Enforce EKU CodeSign extension check
Per NIAP OS_PP, the signer certificate of the UEFI image has to contain
"CodeSign" extension in its Extended Key Usage(EKU).
This commit borrows VerifyEKUsInPkcs7Signature() from edk2 and enforces
the CodeSign check in Pkcs7Verify().
+ Also merged the buffer use-after-free fix (*)
(*) https://bugzilla.tianocore.org/show_bug.cgi?id=2459
Signed-off-by: Gary Lin <glin@suse.com>
---
Cryptlib/InternalCryptLib.h | 32 ++
Cryptlib/Library/BaseCryptLib.h | 40 +++
Cryptlib/Makefile | 1 +
Cryptlib/Pk/CryptPkcs7Verify.c | 10 +
Cryptlib/Pk/CryptPkcs7VerifyEku.c | 516 ++++++++++++++++++++++++++++++
5 files changed, 599 insertions(+)
create mode 100644 Cryptlib/Pk/CryptPkcs7VerifyEku.c
diff --git a/Cryptlib/InternalCryptLib.h b/Cryptlib/InternalCryptLib.h
index e9a4c20..8c9a2a4 100644
--- a/Cryptlib/InternalCryptLib.h
+++ b/Cryptlib/InternalCryptLib.h
@@ -30,5 +30,37 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
#define OBJ_length(o) ((o)->length)
#endif
+/**
+ Check input P7Data is a wrapped ContentInfo structure or not. If not construct
+ a new structure to wrap P7Data.
+
+ Caution: This function may receive untrusted input.
+ UEFI Authenticated Variable is external input, so this function will do basic
+ check for PKCS#7 data structure.
+
+ @param[in] P7Data Pointer to the PKCS#7 message to verify.
+ @param[in] P7Length Length of the PKCS#7 message in bytes.
+ @param[out] WrapFlag If TRUE P7Data is a ContentInfo structure, otherwise
+ return FALSE.
+ @param[out] WrapData If return status of this function is TRUE:
+ 1) when WrapFlag is TRUE, pointer to P7Data.
+ 2) when WrapFlag is FALSE, pointer to a new ContentInfo
+ structure. It's caller's responsibility to free this
+ buffer.
+ @param[out] WrapDataSize Length of ContentInfo structure in bytes.
+
+ @retval TRUE The operation is finished successfully.
+ @retval FALSE The operation is failed due to lack of resources.
+
+**/
+BOOLEAN
+WrapPkcs7Data (
+ IN CONST UINT8 *P7Data,
+ IN UINTN P7Length,
+ OUT BOOLEAN *WrapFlag,
+ OUT UINT8 **WrapData,
+ OUT UINTN *WrapDataSize
+ );
+
#endif
diff --git a/Cryptlib/Library/BaseCryptLib.h b/Cryptlib/Library/BaseCryptLib.h
index 2df8bd2..ed482d3 100644
--- a/Cryptlib/Library/BaseCryptLib.h
+++ b/Cryptlib/Library/BaseCryptLib.h
@@ -2403,6 +2403,46 @@ Pkcs7Verify (
IN UINTN DataLength
);
+/**
+ This function receives a PKCS#7 formatted signature blob,
+ looks for the EKU SEQUENCE blob, and if found then looks
+ for all the required EKUs. This function was created so that
+ the Surface team can cut down on the number of Certificate
+ Authorities (CA's) by checking EKU's on leaf signers for
+ a specific product. This prevents one product's certificate
+ from signing another product's firmware or unlock blobs.
+
+ Note that this function does not validate the certificate chain.
+ That needs to be done before using this function.
+
+ @param[in] Pkcs7Signature The PKCS#7 signed information content block. An array
+ containing the content block with both the signature,
+ the signer's certificate, and any necessary intermediate
+ certificates.
+ @param[in] Pkcs7SignatureSize Number of bytes in Pkcs7Signature.
+ @param[in] RequiredEKUs Array of null-terminated strings listing OIDs of
+ required EKUs that must be present in the signature.
+ @param[in] RequiredEKUsSize Number of elements in the RequiredEKUs string array.
+ @param[in] RequireAllPresent If this is TRUE, then all of the specified EKU's
+ must be present in the leaf signer. If it is
+ FALSE, then we will succeed if we find any
+ of the specified EKU's.
+
+ @retval EFI_SUCCESS The required EKUs were found in the signature.
+ @retval EFI_INVALID_PARAMETER A parameter was invalid.
+ @retval EFI_NOT_FOUND One or more EKU's were not found in the signature.
+
+**/
+EFI_STATUS
+EFIAPI
+VerifyEKUsInPkcs7Signature (
+ IN CONST UINT8 *Pkcs7Signature,
+ IN CONST UINT32 SignatureSize,
+ IN CONST CHAR8 *RequiredEKUs[],
+ IN CONST UINT32 RequiredEKUsSize,
+ IN BOOLEAN RequireAllPresent
+ );
+
/**
Extracts the attached content from a PKCS#7 signed data if existed. The input signed
data could be wrapped in a ContentInfo structure.
diff --git a/Cryptlib/Makefile b/Cryptlib/Makefile
index 18a33b1..a1d8b02 100644
--- a/Cryptlib/Makefile
+++ b/Cryptlib/Makefile
@@ -41,6 +41,7 @@ OBJS = Hash/CryptMd4Null.o \
Pk/CryptRsaExtNull.o \
Pk/CryptPkcs7SignNull.o \
Pk/CryptPkcs7Verify.o \
+ Pk/CryptPkcs7VerifyEku.o \
Pk/CryptDhNull.o \
Pk/CryptTs.o \
Pk/CryptX509.o \
diff --git a/Cryptlib/Pk/CryptPkcs7Verify.c b/Cryptlib/Pk/CryptPkcs7Verify.c
index 09895d8..da15be2 100644
--- a/Cryptlib/Pk/CryptPkcs7Verify.c
+++ b/Cryptlib/Pk/CryptPkcs7Verify.c
@@ -29,6 +29,8 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
#include <openssl/pkcs7.h>
UINT8 mOidValue[9] = { 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x07, 0x02 };
+/* EKU CodeSign */
+CHAR8 mOidCodeSign[] = "1.3.6.1.5.5.7.3.3";
#if 1
#if OPENSSL_VERSION_NUMBER < 0x10100000L
@@ -846,6 +848,8 @@ Pkcs7Verify (
CONST UINT8 *Temp;
UINTN SignedDataSize;
BOOLEAN Wrapped;
+ CONST CHAR8 *Ekus[1];
+ EFI_STATUS EFI_Status;
//
// Check input parameters.
@@ -859,6 +863,7 @@ Pkcs7Verify (
DataBio = NULL;
Cert = NULL;
CertStore = NULL;
+ Ekus[0] = mOidCodeSign;
//
// Register & Initialize necessary digest algorithms for PKCS#7 Handling
@@ -958,6 +963,11 @@ Pkcs7Verify (
//
X509_STORE_set_purpose (CertStore, X509_PURPOSE_ANY);
+ EFI_Status = VerifyEKUsInPkcs7Signature(P7Data, P7Length, Ekus, 1, TRUE);
+ if (EFI_Status != EFI_SUCCESS) {
+ goto _Exit;
+ }
+
//
// Verifies the PKCS#7 signedData structure
//
diff --git a/Cryptlib/Pk/CryptPkcs7VerifyEku.c b/Cryptlib/Pk/CryptPkcs7VerifyEku.c
new file mode 100644
index 0000000..2c172e2
--- /dev/null
+++ b/Cryptlib/Pk/CryptPkcs7VerifyEku.c
@@ -0,0 +1,516 @@
+/** @file
+ This module verifies that Enhanced Key Usages (EKU's) are present within
+ a PKCS7 signature blob using OpenSSL.
+
+ Copyright (C) Microsoft Corporation. All Rights Reserved.
+ Copyright (c) 2019, Intel Corporation. All rights reserved.<BR>
+
+ SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Base.h>
+#include "InternalCryptLib.h"
+#include <openssl/x509v3.h>
+#include <openssl/asn1.h>
+#include <openssl/x509.h>
+#include <openssl/bio.h>
+#include <openssl/x509.h>
+#include <openssl/pkcs7.h>
+#include <openssl/bn.h>
+#include <openssl/x509_vfy.h>
+#include <openssl/pem.h>
+#include <openssl/evp.h>
+#include <openssl/asn1.h>
+
+/**
+ This function will return the leaf signer certificate in a chain. This is
+ required because certificate chains are not guaranteed to have the
+ certificates in the order that they were issued.
+
+ A typical certificate chain looks like this:
+
+
+ ----------------------------
+ | Root |
+ ----------------------------
+ ^
+ |
+ ----------------------------
+ | Policy CA | <-- Typical Trust Anchor.
+ ----------------------------
+ ^
+ |
+ ----------------------------
+ | Issuing CA |
+ ----------------------------
+ ^
+ |
+ -----------------------------
+ / End-Entity (leaf) signer / <-- Bottom certificate.
+ ----------------------------- EKU: "1.3.6.1.4.1.311.76.9.21.1"
+ (Firmware Signing)
+
+
+ @param[in] CertChain Certificate chain.
+
+ @param[out] SignerCert Last certificate in the chain. For PKCS7 signatures,
+ this will be the end-entity (leaf) signer cert.
+
+ @retval EFI_SUCCESS The required EKUs were found in the signature.
+ @retval EFI_INVALID_PARAMETER A parameter was invalid.
+ @retval EFI_NOT_FOUND The number of signers found was not 1.
+
+**/
+EFI_STATUS
+GetSignerCertificate (
+ IN CONST PKCS7 *CertChain,
+ OUT X509 **SignerCert
+ )
+{
+ EFI_STATUS Status;
+ STACK_OF(X509) *Signers;
+ INT32 NumberSigners;
+
+ Status = EFI_SUCCESS;
+ Signers = NULL;
+ NumberSigners = 0;
+
+ if (CertChain == NULL || SignerCert == NULL) {
+ Status = EFI_INVALID_PARAMETER;
+ goto Exit;
+ }
+
+ //
+ // Get the signers from the chain.
+ //
+ Signers = PKCS7_get0_signers ((PKCS7*) CertChain, NULL, PKCS7_BINARY);
+ if (Signers == NULL) {
+ //
+ // Fail to get signers form PKCS7
+ //
+ Status = EFI_INVALID_PARAMETER;
+ goto Exit;
+ }
+
+ //
+ // There should only be one signer in the PKCS7 stack.
+ //
+ NumberSigners = sk_X509_num (Signers);
+ if (NumberSigners != 1) {
+ //
+ // The number of singers should have been 1
+ //
+ Status = EFI_NOT_FOUND;
+ goto Exit;
+ }
+
+ *SignerCert = sk_X509_value (Signers, 0);
+
+Exit:
+ //
+ // Release Resources
+ //
+ if (Signers != NULL) {
+ sk_X509_free (Signers);
+ }
+
+ return Status;
+}
+
+
+/**
+ Determines if the specified EKU represented in ASN1 form is present
+ in a given certificate.
+
+ @param[in] Cert The certificate to check.
+
+ @param[in] Asn1ToFind The EKU to look for.
+
+ @retval EFI_SUCCESS We successfully identified the signing type.
+ @retval EFI_INVALID_PARAMETER A parameter was invalid.
+ @retval EFI_NOT_FOUND One or more EKU's were not found in the signature.
+
+**/
+EFI_STATUS
+IsEkuInCertificate (
+ IN CONST X509 *Cert,
+ IN ASN1_OBJECT *Asn1ToFind
+ )
+{
+ EFI_STATUS Status;
+ X509 *ClonedCert;
+ X509_EXTENSION *Extension;
+ EXTENDED_KEY_USAGE *Eku;
+ INT32 ExtensionIndex;
+ INTN NumExtensions;
+ ASN1_OBJECT *Asn1InCert;
+ INTN Index;
+
+ Status = EFI_NOT_FOUND;
+ ClonedCert = NULL;
+ Extension = NULL;
+ Eku = NULL;
+ ExtensionIndex = -1;
+ NumExtensions = 0;
+ Asn1InCert = NULL;
+
+ if (Cert == NULL || Asn1ToFind == NULL) {
+ Status = EFI_INVALID_PARAMETER;
+ goto Exit;
+ }
+
+ //
+ // Clone the certificate. This is required because the Extension API's
+ // only work once per instance of an X509 object.
+ //
+ ClonedCert = X509_dup ((X509*)Cert);
+ if (ClonedCert == NULL) {
+ //
+ // Fail to duplicate cert.
+ //
+ Status = EFI_INVALID_PARAMETER;
+ goto Exit;
+ }
+
+ //
+ // Look for the extended key usage.
+ //
+ ExtensionIndex = X509_get_ext_by_NID (ClonedCert, NID_ext_key_usage, -1);
+
+ if (ExtensionIndex < 0) {
+ //
+ // Fail to find 'NID_ext_key_usage' in Cert.
+ //
+ goto Exit;
+ }
+
+ Extension = X509_get_ext (ClonedCert, ExtensionIndex);
+ if (Extension == NULL) {
+ //
+ // Fail to get Extension form cert.
+ //
+ goto Exit;
+ }
+
+ Eku = (EXTENDED_KEY_USAGE*)X509V3_EXT_d2i (Extension);
+ if (Eku == NULL) {
+ //
+ // Fail to get Eku from extension.
+ //
+ goto Exit;
+ }
+
+ NumExtensions = sk_ASN1_OBJECT_num (Eku);
+
+ //
+ // Now loop through the extensions, looking for the specified Eku.
+ //
+ for (Index = 0; Index < NumExtensions; Index++) {
+ Asn1InCert = sk_ASN1_OBJECT_value (Eku, (INT32)Index);
+ if (Asn1InCert == NULL) {
+ //
+ // Fail to get ASN object from Eku.
+ //
+ goto Exit;
+ }
+
+ if (OBJ_cmp(Asn1InCert, Asn1ToFind) == 0) {
+ //
+ // Found Eku in certificate.
+ //
+ Status = EFI_SUCCESS;
+ goto Exit;
+ }
+ }
+
+Exit:
+
+ //
+ // Release Resources
+ //
+ if (ClonedCert != NULL) {
+ X509_free (ClonedCert);
+ }
+
+ if (Eku != NULL) {
+ sk_ASN1_OBJECT_pop_free (Eku, ASN1_OBJECT_free);
+ }
+
+ return Status;
+}
+
+
+/**
+ Determines if the specified EKUs are present in a signing certificate.
+
+ @param[in] SignerCert The certificate to check.
+ @param[in] RequiredEKUs The EKUs to look for.
+ @param[in] RequiredEKUsSize The number of EKUs
+ @param[in] RequireAllPresent If TRUE, then all the specified EKUs
+ must be present in the certificate.
+
+ @retval EFI_SUCCESS We successfully identified the signing type.
+ @retval EFI_INVALID_PARAMETER A parameter was invalid.
+ @retval EFI_NOT_FOUND One or more EKU's were not found in the signature.
+**/
+EFI_STATUS
+CheckEKUs(
+ IN CONST X509 *SignerCert,
+ IN CONST CHAR8 *RequiredEKUs[],
+ IN CONST UINT32 RequiredEKUsSize,
+ IN BOOLEAN RequireAllPresent
+ )
+{
+ EFI_STATUS Status;
+ ASN1_OBJECT *Asn1ToFind;
+ UINT32 NumEkusFound;
+ UINT32 Index;
+
+ Status = EFI_NOT_FOUND;
+ Asn1ToFind = NULL;
+ NumEkusFound = 0;
+
+ if (SignerCert == NULL || RequiredEKUs == NULL || RequiredEKUsSize == 0) {
+ Status = EFI_INVALID_PARAMETER;
+ goto Exit;
+ }
+
+ for (Index = 0; Index < RequiredEKUsSize; Index++) {
+ //
+ // Finding required EKU in cert.
+ //
+ if (Asn1ToFind != NULL) {
+ ASN1_OBJECT_free(Asn1ToFind);
+ Asn1ToFind = NULL;
+ }
+
+ Asn1ToFind = OBJ_txt2obj (RequiredEKUs[Index], 0);
+ if (Asn1ToFind == NULL) {
+ //
+ // Fail to convert required EKU to ASN1.
+ //
+ Status = EFI_INVALID_PARAMETER;
+ goto Exit;
+ }
+
+ Status = IsEkuInCertificate (SignerCert, Asn1ToFind);
+ if (Status == EFI_SUCCESS) {
+ NumEkusFound++;
+ if (!RequireAllPresent) {
+ //
+ // Found at least one, so we are done.
+ //
+ goto Exit;
+ }
+ } else {
+ //
+ // Fail to find Eku in cert
+ break;
+ }
+ }
+
+Exit:
+
+ if (Asn1ToFind != NULL) {
+ ASN1_OBJECT_free(Asn1ToFind);
+ }
+
+ if (RequireAllPresent &&
+ NumEkusFound == RequiredEKUsSize) {
+ //
+ // Found all required EKUs in certificate.
+ //
+ Status = EFI_SUCCESS;
+ }
+
+ return Status;
+}
+
+/**
+ This function receives a PKCS#7 formatted signature blob,
+ looks for the EKU SEQUENCE blob, and if found then looks
+ for all the required EKUs. This function was created so that
+ the Surface team can cut down on the number of Certificate
+ Authorities (CA's) by checking EKU's on leaf signers for
+ a specific product. This prevents one product's certificate
+ from signing another product's firmware or unlock blobs.
+
+ Note that this function does not validate the certificate chain.
+ That needs to be done before using this function.
+
+ @param[in] Pkcs7Signature The PKCS#7 signed information content block. An array
+ containing the content block with both the signature,
+ the signer's certificate, and any necessary intermediate
+ certificates.
+ @param[in] Pkcs7SignatureSize Number of bytes in Pkcs7Signature.
+ @param[in] RequiredEKUs Array of null-terminated strings listing OIDs of
+ required EKUs that must be present in the signature.
+ @param[in] RequiredEKUsSize Number of elements in the RequiredEKUs string array.
+ @param[in] RequireAllPresent If this is TRUE, then all of the specified EKU's
+ must be present in the leaf signer. If it is
+ FALSE, then we will succeed if we find any
+ of the specified EKU's.
+
+ @retval EFI_SUCCESS The required EKUs were found in the signature.
+ @retval EFI_INVALID_PARAMETER A parameter was invalid.
+ @retval EFI_NOT_FOUND One or more EKU's were not found in the signature.
+
+**/
+EFI_STATUS
+EFIAPI
+VerifyEKUsInPkcs7Signature (
+ IN CONST UINT8 *Pkcs7Signature,
+ IN CONST UINT32 SignatureSize,
+ IN CONST CHAR8 *RequiredEKUs[],
+ IN CONST UINT32 RequiredEKUsSize,
+ IN BOOLEAN RequireAllPresent
+ )
+{
+ EFI_STATUS Status;
+ PKCS7 *Pkcs7;
+ STACK_OF(X509) *CertChain;
+ INT32 SignatureType;
+ INT32 NumberCertsInSignature;
+ X509 *SignerCert;
+ UINT8 *SignedData;
+ UINT8 *Temp;
+ UINTN SignedDataSize;
+ BOOLEAN IsWrapped;
+ BOOLEAN Ok;
+
+ Status = EFI_SUCCESS;
+ Pkcs7 = NULL;
+ CertChain = NULL;
+ SignatureType = 0;
+ NumberCertsInSignature = 0;
+ SignerCert = NULL;
+ SignedData = NULL;
+ SignedDataSize = 0;
+ IsWrapped = FALSE;
+ Ok = FALSE;
+
+ //
+ //Validate the input parameters.
+ //
+ if (Pkcs7Signature == NULL ||
+ SignatureSize == 0 ||
+ RequiredEKUs == NULL ||
+ RequiredEKUsSize == 0) {
+ Status = EFI_INVALID_PARAMETER;
+ goto Exit;
+ }
+
+ if (RequiredEKUsSize == 1) {
+ RequireAllPresent = TRUE;
+ }
+
+ //
+ // Wrap the PKCS7 data if needed.
+ //
+ Ok = WrapPkcs7Data (Pkcs7Signature,
+ SignatureSize,
+ &IsWrapped,
+ &SignedData,
+ &SignedDataSize);
+ if (!Ok) {
+ //
+ // Fail to Wrap the PKCS7 data.
+ //
+ Status = EFI_INVALID_PARAMETER;
+ goto Exit;
+ }
+
+ Temp = SignedData;
+
+ //
+ // Create the PKCS7 object.
+ //
+ Pkcs7 = d2i_PKCS7 (NULL, (const unsigned char **)&Temp, (INT32)SignedDataSize);
+ if (Pkcs7 == NULL) {
+ //
+ // Fail to read PKCS7 data.
+ //
+ Status = EFI_INVALID_PARAMETER;
+ goto Exit;
+ }
+
+ //
+ // Get the certificate chain.
+ //
+ SignatureType = OBJ_obj2nid (Pkcs7->type);
+ switch (SignatureType) {
+ case NID_pkcs7_signed:
+ if (Pkcs7->d.sign != NULL) {
+ CertChain = Pkcs7->d.sign->cert;
+ }
+ break;
+ case NID_pkcs7_signedAndEnveloped:
+ if (Pkcs7->d.signed_and_enveloped != NULL) {
+ CertChain = Pkcs7->d.signed_and_enveloped->cert;
+ }
+ break;
+ default:
+ break;
+ }
+
+ //
+ // Ensure we have a certificate stack
+ //
+ if (CertChain == NULL) {
+ //
+ // Fail to get the certificate stack from signature.
+ //
+ Status = EFI_INVALID_PARAMETER;
+ goto Exit;
+ }
+
+ //
+ // Find out how many certificates were in the PKCS7 signature.
+ //
+ NumberCertsInSignature = sk_X509_num (CertChain);
+
+ if (NumberCertsInSignature == 0) {
+ //
+ // Fail to find any certificates in signature.
+ //
+ Status = EFI_INVALID_PARAMETER;
+ goto Exit;
+ }
+
+ //
+ // Get the leaf signer.
+ //
+ Status = GetSignerCertificate (Pkcs7, &SignerCert);
+ if (Status != EFI_SUCCESS || SignerCert == NULL) {
+ //
+ // Fail to get the end-entity leaf signer certificate.
+ //
+ Status = EFI_INVALID_PARAMETER;
+ goto Exit;
+ }
+
+ Status = CheckEKUs (SignerCert, RequiredEKUs, RequiredEKUsSize, RequireAllPresent);
+ if (Status != EFI_SUCCESS) {
+ goto Exit;
+ }
+
+Exit:
+
+ //
+ // Release Resources
+ //
+ // If the signature was not wrapped, then the call to WrapData() will allocate
+ // the data and add a header to it
+ //
+ if (!IsWrapped && SignedData) {
+ free (SignedData);
+ }
+
+ if (Pkcs7 != NULL) {
+ PKCS7_free (Pkcs7);
+ }
+
+ return Status;
+}
+
--
2.29.2
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