FmpDevicePkg/FmpDxe/DetectTestKey.c

   1 /**  @file
   2   Detects if PcdFmpDevicePkcs7CertBufferXdr contains a test key.
   3
   4   Copyright (c) 2018, Intel Corporation. All rights reserved.<BR>
   5
   6   Redistribution and use in source and binary forms, with or without
   7   modification, are permitted provided that the following conditions are met:
   8   1. Redistributions of source code must retain the above copyright notice,
   9   this list of conditions and the following disclaimer.
  10   2. Redistributions in binary form must reproduce the above copyright notice,
  11   this list of conditions and the following disclaimer in the documentation
  12   and/or other materials provided with the distribution.
  13
  14   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
  15   ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  16   WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  17   IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  18   INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  19   BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  20   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  21   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
  22   OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  23   ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24
  25 **/
  26
  27 #include <PiDxe.h>
  28 #include <Library/DebugLib.h>
  29 #include <Library/BaseLib.h>
  30 #include <Library/BaseMemoryLib.h>
  31 #include <Library/PcdLib.h>
  32 #include <Library/MemoryAllocationLib.h>
  33 #include <Library/BaseCryptLib.h>
  34
  35 /**
  36   Check to see if any of the keys in PcdFmpDevicePkcs7CertBufferXdr matches
  37   the test key.  PcdFmpDeviceTestKeySha256Digest contains the SHA256 hash of
  38   the test key.  For each key in PcdFmpDevicePkcs7CertBufferXdr, compute the
  39   SHA256 hash and compare it to PcdFmpDeviceTestKeySha256Digest.  If the
  40   SHA256 hash matches or there is then error computing the SHA256 hash, then
  41   set PcdTestKeyUsed to TRUE.  Skip this check if PcdTestKeyUsed is already
  42   TRUE or PcdFmpDeviceTestKeySha256Digest is not exactly SHA256_DIGEST_SIZE
  43   bytes.
  44 **/
  45 VOID
  46 DetectTestKey (
  47   VOID
  48   )
  49 {
  50   BOOLEAN  TestKeyUsed;
  51   UINTN    PublicKeyDataLength;
  52   UINT8    *PublicKeyDataXdr;
  53   UINT8    *PublicKeyDataXdrEnd;
  54   VOID     *HashContext;
  55   UINT8    Digest[SHA256_DIGEST_SIZE];
  56
  57   //
  58   // If PcdFmpDeviceTestKeySha256Digest is not exacty SHA256_DIGEST_SIZE bytes,
  59   // then skip the test key detection.
  60   //
  61   if (PcdGetSize (PcdFmpDeviceTestKeySha256Digest) != SHA256_DIGEST_SIZE) {
  62     return;
  63   }
  64
  65   //
  66   // If PcdTestKeyUsed is already TRUE, then skip test key detection
  67   //
  68   TestKeyUsed = PcdGetBool (PcdTestKeyUsed);
  69   if (TestKeyUsed) {
  70     return;
  71   }
  72
  73   //
  74   // If PcdFmpDevicePkcs7CertBufferXdr is invalid, then skip test key detection
  75   //
  76   PublicKeyDataXdr    = PcdGetPtr (PcdFmpDevicePkcs7CertBufferXdr);
  77   PublicKeyDataXdrEnd = PublicKeyDataXdr + PcdGetSize (PcdFmpDevicePkcs7CertBufferXdr);
  78   if (PublicKeyDataXdr == NULL || PublicKeyDataXdr == PublicKeyDataXdrEnd) {
  79     return;
  80   }
  81
  82   //
  83   // Allocate hash context buffer required for SHA 256
  84   //
  85   HashContext = AllocatePool (Sha256GetContextSize ());
  86   if (HashContext == NULL) {
  87     TestKeyUsed = TRUE;
  88   }
  89
  90   //
  91   // Loop through all keys in PcdFmpDevicePkcs7CertBufferXdr
  92   //
  93   while (!TestKeyUsed && PublicKeyDataXdr < PublicKeyDataXdrEnd) {
  94     if (PublicKeyDataXdr + sizeof (UINT32) > PublicKeyDataXdrEnd) {
  95       //
  96       // Key data extends beyond end of PCD
  97       //
  98       break;
  99     }
 100     //
 101     // Read key length stored in big endian format
 102     //
 103     PublicKeyDataLength = SwapBytes32 (*(UINT32 *)(PublicKeyDataXdr));
 104     //
 105     // Point to the start of the key data
 106     //
 107     PublicKeyDataXdr += sizeof (UINT32);
 108     if (PublicKeyDataXdr + PublicKeyDataLength > PublicKeyDataXdrEnd) {
 109       //
 110       // Key data extends beyond end of PCD
 111       //
 112       break;
 113     }
 114
 115     //
 116     // Hash public key from PcdFmpDevicePkcs7CertBufferXdr using SHA256.
 117     // If error occurs computing SHA256, then assume test key is in use.
 118     //
 119     ZeroMem (Digest, SHA256_DIGEST_SIZE);
 120     if (!Sha256Init (HashContext)) {
 121       TestKeyUsed = TRUE;
 122       break;
 123     }
 124     if (!Sha256Update (HashContext, PublicKeyDataXdr, PublicKeyDataLength)) {
 125       TestKeyUsed = TRUE;
 126       break;
 127     }
 128     if (!Sha256Final (HashContext, Digest)) {
 129       TestKeyUsed = TRUE;
 130       break;
 131     }
 132
 133     //
 134     // Check if SHA256 hash of public key matches SHA256 hash of test key
 135     //
 136     if (CompareMem (Digest, PcdGetPtr (PcdFmpDeviceTestKeySha256Digest), SHA256_DIGEST_SIZE) == 0) {
 137       TestKeyUsed = TRUE;
 138       break;
 139     }
 140
 141     //
 142     // Point to start of next key
 143     //
 144     PublicKeyDataXdr += PublicKeyDataLength;
 145     PublicKeyDataXdr = (UINT8 *)ALIGN_POINTER (PublicKeyDataXdr, sizeof (UINT32));
 146   }
 147
 148   //
 149   // Free hash context buffer required for SHA 256
 150   //
 151   if (HashContext != NULL) {
 152     FreePool (HashContext);
 153     HashContext = NULL;
 154   }
 155
 156   //
 157   // If test key detected or an error occured checking for the test key, then
 158   // set PcdTestKeyUsed to TRUE.
 159   //
 160   if (TestKeyUsed) {
 161     DEBUG ((DEBUG_INFO, "FmpDxe: Test key detected in PcdFmpDevicePkcs7CertBufferXdr.\n"));
 162     PcdSetBoolS (PcdTestKeyUsed, TRUE);
 163   } else {
 164     DEBUG ((DEBUG_INFO, "FmpDxe: No test key detected in PcdFmpDevicePkcs7CertBufferXdr.\n"));
 165   }
 166 }