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      1 /* Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
      2  * Use of this source code is governed by a BSD-style license that can be
      3  * found in the LICENSE file.
      4  *
      5  * Functions for updating the TPM state with the status of boot path.
      6  */
      7 
      8 #include "sysincludes.h"
      9 
     10 #include "tlcl.h"
     11 #include "tpm_bootmode.h"
     12 #include "utility.h"
     13 #include "vboot_api.h"
     14 
     15 /* TPM PCRs to use for storing boot mode measurements. */
     16 #define BOOT_MODE_PCR 0
     17 #define HWID_DIGEST_PCR 1
     18 
     19 /*
     20  * Input digests for PCR extend.
     21  * These are calculated as:
     22  *    SHA1("|Developer_Mode||Recovery_Mode||Keyblock_Mode|").
     23  * Developer_Mode can be 0 or 1.
     24  * Recovery_Mode can be 0 or 1.
     25  * Keyblock flags are defined in vboot_struct.h
     26  *
     27  * We map them to Keyblock_Mode as follows:
     28  *   -----------------------------------------
     29  *   Keyblock Flags            | Keyblock Mode
     30  *   -----------------------------------------
     31  *   6 (Dev-signed firmware)   |     2
     32  *   7 Normal-signed firmware  |     1
     33  *   (anything else)           |     0
     34  */
     35 
     36 const char* kBootStateSHA1Digests[] = {
     37 	/* SHA1("\x00\x00\x00") */
     38 	"\x29\xe2\xdc\xfb\xb1\x6f\x63\xbb\x02\x54\xdf\x75\x85\xa1\x5b\xb6"
     39 	"\xfb\x5e\x92\x7d",
     40 
     41 	/* SHA1("\x00\x00\x01") */
     42 	"\x25\x47\xcc\x73\x6e\x95\x1f\xa4\x91\x98\x53\xc4\x3a\xe8\x90\x86"
     43 	"\x1a\x3b\x32\x64",
     44 
     45 	/* SHA1("\x00\x00\x02") */
     46 	"\x1e\xf6\x24\x48\x2d\x62\x0e\x43\xe6\xd3\x4d\xa1\xaf\xe4\x62\x67"
     47 	"\xfc\x69\x5d\x9b",
     48 
     49 	/* SHA1("\x00\x01\x00") */
     50 	"\x62\x57\x18\x91\x21\x5b\x4e\xfc\x1c\xea\xb7\x44\xce\x59\xdd\x0b"
     51 	"\x66\xea\x6f\x73",
     52 
     53 	/* SHA1("\x00\x01\x01") */
     54 	"\xee\xe4\x47\xed\xc7\x9f\xea\x1c\xa7\xc7\xd3\x4e\x46\x32\x61\xcd"
     55 	"\xa4\xba\x33\x9e",
     56 
     57 	/* SHA1("\x00\x01\x02") */
     58 	"\x0c\x7a\x62\x3f\xd2\xbb\xc0\x5b\x06\x42\x3b\xe3\x59\xe4\x02\x1d"
     59 	"\x36\xe7\x21\xad",
     60 
     61 	/* SHA1("\x01\x00\x00") */
     62 	"\x95\x08\xe9\x05\x48\xb0\x44\x0a\x4a\x61\xe5\x74\x3b\x76\xc1\xe3"
     63 	"\x09\xb2\x3b\x7f",
     64 
     65 	/* SHA1("\x01\x00\x01") */
     66 	"\xc4\x2a\xc1\xc4\x6f\x1d\x4e\x21\x1c\x73\x5c\xc7\xdf\xad\x4f\xf8"
     67 	"\x39\x11\x10\xe9",
     68 
     69 	/* SHA1("\x01\x00\x02") */
     70 	"\xfa\x01\x0d\x26\x64\xcc\x5b\x3b\x82\xee\x48\x8f\xe2\xb9\xf5\x0f"
     71 	"\x49\x32\xeb\x8f",
     72 
     73 	/* SHA1("\x01\x01\x00") */
     74 	"\x47\xec\x8d\x98\x36\x64\x33\xdc\x00\x2e\x77\x21\xc9\xe3\x7d\x50"
     75 	"\x67\x54\x79\x37",
     76 
     77 	/* SHA1("\x01\x01\x01") */
     78 	"\x28\xd8\x6c\x56\xb3\xbf\x26\xd2\x36\x56\x9b\x8d\xc8\xc3\xf9\x1f"
     79 	"\x32\xf4\x7b\xc7",
     80 
     81 	/* SHA1("\x01\x01\x02") */
     82 	"\x12\xa3\x40\xd7\x89\x7f\xe7\x13\xfc\x8f\x02\xac\x53\x65\xb8\x6e"
     83 	"\xbf\x35\x31\x78",
     84 };
     85 
     86 #define MAX_BOOT_STATE_INDEX (sizeof(kBootStateSHA1Digests)/sizeof(char *))
     87 
     88 /*
     89  * Used for PCR extend when the passed-in boot state is invalid or if there is
     90  * an internal error.
     91  */
     92 const uint8_t kBootInvalidSHA1Digest[] = {
     93 	"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
     94 	"\xff\xff\xff\xff"
     95 };
     96 
     97 /**
     98  * Given the boot state, return the correct SHA1 digest index for TPMExtend
     99  * in kBootStateSHA1Digests[].
    100  */
    101 static int GetBootStateIndex(int dev_mode, int rec_mode,
    102                              uint64_t keyblock_flags)
    103 {
    104 	int index = 0;
    105 
    106 	/*
    107 	 * Convert keyblock flags into keyblock mode which we use to index into
    108 	 * kBootStateSHA1Digest[].
    109 	 */
    110 	switch(keyblock_flags) {
    111 	case 6:
    112 		/*
    113 		 * KEY_BLOCK_FLAG_RECOVERY_0 | KEY_BLOCK_FLAG_DEVELOPER_1
    114 		 *
    115 		 * Developer firmware. */
    116 		index = 2;
    117 		break;
    118 	case 7:
    119 		/*
    120 		 * KEY_BLOCK_FLAG_RECOVERY_0 | KEY_BLOCK_FLAG_DEVELOPER_0
    121 		 * | KEY_BLOCK_FLAGS_DEVELOPER_1
    122 		 */
    123 		index = 1;
    124 		break;
    125 	default:
    126 		/* Any other keyblock flags. */
    127 		index = 0;
    128 	};
    129 
    130 	if (rec_mode)
    131 		index += 3;
    132 	if (dev_mode)
    133 		index += 6;
    134 	return index;
    135 }
    136 
    137 uint32_t SetTPMBootModeState(int developer_mode, int recovery_mode,
    138 			     uint64_t fw_keyblock_flags,
    139 			     GoogleBinaryBlockHeader *gbb)
    140 {
    141 	uint32_t result0, result1 = 0;
    142 	const uint8_t *in_digest = NULL;
    143 	uint8_t out_digest[20];  /* For PCR extend output. */
    144 	int digest_index = GetBootStateIndex(developer_mode, recovery_mode,
    145 					     fw_keyblock_flags);
    146 
    147 	if (digest_index >= 0 && digest_index < MAX_BOOT_STATE_INDEX) {
    148 		in_digest = (const uint8_t*)
    149 			kBootStateSHA1Digests[digest_index];
    150 	} else {
    151 		/* Internal out of bounds error. */
    152 		in_digest = kBootInvalidSHA1Digest;
    153 	}
    154 
    155 	result0 = TlclExtend(BOOT_MODE_PCR, in_digest, out_digest);
    156 	VBDEBUG(("TPM: SetTPMBootModeState boot mode PCR%d result %d\n",
    157 		 BOOT_MODE_PCR, result0));
    158 
    159 	/* Extend the HWID Digest into PCR1 (GBB v1.2 and later only) */
    160 	if (gbb && gbb->minor_version >= 2) {
    161 		result1 = TlclExtend(HWID_DIGEST_PCR, gbb->hwid_digest,
    162 				     out_digest);
    163 		VBDEBUG(("TPM: SetTPMBootModeState HWID PCR%d result %d\n",
    164 			 HWID_DIGEST_PCR, result1));
    165 	}
    166 
    167 	/* The caller only looks for nonzero results, not error codes. */
    168 	return result0 || result1;
    169 }
    170