system76-edk2/CryptoPkg/Library/BaseCryptLib/Pk/CryptAuthenticode.c

/** @file
  Authenticode Portable Executable Signature Verification over OpenSSL.

  Caution: This module requires additional review when modified.
  This library will have external input - signature (e.g. PE/COFF Authenticode).
  This external input must be validated carefully to avoid security issue like
  buffer overflow, integer overflow.

  AuthenticodeVerify() will get PE/COFF Authenticode and will do basic check for
  data structure.

Copyright (c) 2011 - 2020, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include "InternalCryptLib.h"

#include <openssl/objects.h>
#include <openssl/x509.h>
#include <openssl/pkcs7.h>

//
// OID ASN.1 Value for SPC_INDIRECT_DATA_OBJID
//
UINT8  mSpcIndirectOidValue[] = {
  0x2B, 0x06, 0x01, 0x04, 0x01, 0x82, 0x37, 0x02, 0x01, 0x04
};

/**
  Verifies the validity of a PE/COFF Authenticode Signature as described in "Windows
  Authenticode Portable Executable Signature Format".

  If AuthData is NULL, then return FALSE.
  If ImageHash is NULL, then return FALSE.

  Caution: This function may receive untrusted input.
  PE/COFF Authenticode is external input, so this function will do basic check for
  Authenticode data structure.

  @param[in]  AuthData     Pointer to the Authenticode Signature retrieved from signed
                           PE/COFF image to be verified.
  @param[in]  DataSize     Size of the Authenticode Signature in bytes.
  @param[in]  TrustedCert  Pointer to a trusted/root certificate encoded in DER, which
                           is used for certificate chain verification.
  @param[in]  CertSize     Size of the trusted certificate in bytes.
  @param[in]  ImageHash    Pointer to the original image file hash value. The procedure
                           for calculating the image hash value is described in Authenticode
                           specification.
  @param[in]  HashSize     Size of Image hash value in bytes.

  @retval  TRUE   The specified Authenticode Signature is valid.
  @retval  FALSE  Invalid Authenticode Signature.

**/
BOOLEAN
EFIAPI
AuthenticodeVerify (
  IN  CONST UINT8  *AuthData,
  IN  UINTN        DataSize,
  IN  CONST UINT8  *TrustedCert,
  IN  UINTN        CertSize,
  IN  CONST UINT8  *ImageHash,
  IN  UINTN        HashSize
  )
{
  BOOLEAN      Status;
  PKCS7        *Pkcs7;
  CONST UINT8  *Temp;
  CONST UINT8  *OrigAuthData;
  UINT8        *SpcIndirectDataContent;
  UINT8        Asn1Byte;
  UINTN        ContentSize;
  CONST UINT8  *SpcIndirectDataOid;

  //
  // Check input parameters.
  //
  if ((AuthData == NULL) || (TrustedCert == NULL) || (ImageHash == NULL)) {
    return FALSE;
  }

  if ((DataSize > INT_MAX) || (CertSize > INT_MAX) || (HashSize > INT_MAX)) {
    return FALSE;
  }

  Status       = FALSE;
  Pkcs7        = NULL;
  OrigAuthData = AuthData;

  //
  // Retrieve & Parse PKCS#7 Data (DER encoding) from Authenticode Signature
  //
  Temp  = AuthData;
  Pkcs7 = d2i_PKCS7 (NULL, &Temp, (int)DataSize);
  if (Pkcs7 == NULL) {
    goto _Exit;
  }

  //
  // Check if it's PKCS#7 Signed Data (for Authenticode Scenario)
  //
  if (!PKCS7_type_is_signed (Pkcs7) || PKCS7_get_detached (Pkcs7)) {
    goto _Exit;
  }

  //
  // NOTE: OpenSSL PKCS7 Decoder didn't work for Authenticode-format signed data due to
  //       some authenticode-specific structure. Use opaque ASN.1 string to retrieve
  //       PKCS#7 ContentInfo here.
  //
  SpcIndirectDataOid = OBJ_get0_data (Pkcs7->d.sign->contents->type);
  if ((OBJ_length (Pkcs7->d.sign->contents->type) != sizeof (mSpcIndirectOidValue)) ||
      (CompareMem (
         SpcIndirectDataOid,
         mSpcIndirectOidValue,
         sizeof (mSpcIndirectOidValue)
         ) != 0))
  {
    //
    // Un-matched SPC_INDIRECT_DATA_OBJID.
    //
    goto _Exit;
  }

  SpcIndirectDataContent = (UINT8 *)(Pkcs7->d.sign->contents->d.other->value.asn1_string->data);

  //
  // Retrieve the SEQUENCE data size from ASN.1-encoded SpcIndirectDataContent.
  //
  Asn1Byte = *(SpcIndirectDataContent + 1);

  if ((Asn1Byte & 0x80) == 0) {
    //
    // Short Form of Length Encoding (Length < 128)
    //
    ContentSize = (UINTN)(Asn1Byte & 0x7F);
    //
    // Skip the SEQUENCE Tag;
    //
    SpcIndirectDataContent += 2;
  } else if ((Asn1Byte & 0x81) == 0x81) {
    //
    // Long Form of Length Encoding (128 <= Length < 255, Single Octet)
    //
    ContentSize = (UINTN)(*(UINT8 *)(SpcIndirectDataContent + 2));
    //
    // Skip the SEQUENCE Tag;
    //
    SpcIndirectDataContent += 3;
  } else if ((Asn1Byte & 0x82) == 0x82) {
    //
    // Long Form of Length Encoding (Length > 255, Two Octet)
    //
    ContentSize = (UINTN)(*(UINT8 *)(SpcIndirectDataContent + 2));
    ContentSize = (ContentSize << 8) + (UINTN)(*(UINT8 *)(SpcIndirectDataContent + 3));
    //
    // Skip the SEQUENCE Tag;
    //
    SpcIndirectDataContent += 4;
  } else {
    goto _Exit;
  }

  //
  // Compare the original file hash value to the digest retrieve from SpcIndirectDataContent
  // defined in Authenticode
  // NOTE: Need to double-check HashLength here!
  //
  if (CompareMem (SpcIndirectDataContent + ContentSize - HashSize, ImageHash, HashSize) != 0) {
    //
    // Un-matched PE/COFF Hash Value
    //
    goto _Exit;
  }

  //
  // Verifies the PKCS#7 Signed Data in PE/COFF Authenticode Signature
  //
  Status = (BOOLEAN)Pkcs7Verify (OrigAuthData, DataSize, TrustedCert, CertSize, SpcIndirectDataContent, ContentSize);

_Exit:
  //
  // Release Resources
  //
  PKCS7_free (Pkcs7);

  return Status;
}