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shim
shim-bsc1177315-verify-eku-codesign.patch
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File shim-bsc1177315-verify-eku-codesign.patch of Package shim
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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