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SUSE:SLE-15-SP2:Update
shim-susesigned.16785
shim-bsc1177315-verify-eku-codesign.patch
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File shim-bsc1177315-verify-eku-codesign.patch of Package shim-susesigned.16785
From b27f96477647c0a055e97f1f9a9cffba354dad6f 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(). Signed-off-by: Gary Lin <glin@suse.com> --- Cryptlib/InternalCryptLib.h | 32 ++ Cryptlib/Library/BaseCryptLib.h | 40 +++ Cryptlib/Makefile | 1 + Cryptlib/Pk/CryptPkcs7Verify.c | 11 + Cryptlib/Pk/CryptPkcs7VerifyEku.c | 520 ++++++++++++++++++++++++++++++ 5 files changed, 604 insertions(+) create mode 100644 Cryptlib/Pk/CryptPkcs7VerifyEku.c diff --git a/Cryptlib/InternalCryptLib.h b/Cryptlib/InternalCryptLib.h index 8cccf72..026793f 100644 --- a/Cryptlib/InternalCryptLib.h +++ b/Cryptlib/InternalCryptLib.h @@ -33,4 +33,36 @@ 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 2aa5695..0147587 100644 --- a/Cryptlib/Makefile +++ b/Cryptlib/Makefile @@ -38,6 +38,7 @@ 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 cbd9669..b3ef356 100644 --- a/Cryptlib/Pk/CryptPkcs7Verify.c +++ b/Cryptlib/Pk/CryptPkcs7Verify.c @@ -30,6 +30,9 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. 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"; + BOOLEAN ca_warning; void @@ -812,6 +815,8 @@ Pkcs7Verify ( CONST UINT8 *Temp; UINTN SignedDataSize; BOOLEAN Wrapped; + CONST CHAR8 *Ekus[1]; + EFI_STATUS EFI_Status; // // Check input parameters. @@ -825,6 +830,7 @@ Pkcs7Verify ( DataBio = NULL; Cert = NULL; CertStore = NULL; + Ekus[0] = mOidCodeSign; // // Register & Initialize necessary digest algorithms for PKCS#7 Handling @@ -924,6 +930,11 @@ 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..d086886 --- /dev/null +++ b/Cryptlib/Pk/CryptPkcs7VerifyEku.c @@ -0,0 +1,520 @@ +/** @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 (SignerCert != NULL) { + X509_free (SignerCert); + } + + if (Pkcs7 != NULL) { + PKCS7_free (Pkcs7); + } + + return Status; +} + -- 2.28.0
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