security/integrity/ima/ima_crypto.c

   1 /*
   2  * Copyright (C) 2005,2006,2007,2008 IBM Corporation
   3  *
   4  * Authors:
   5  * Mimi Zohar <zohar@us.ibm.com>
   6  * Kylene Hall <kjhall@us.ibm.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation, version 2 of the License.
  11  *
  12  * File: ima_crypto.c
  13  *      Calculates md5/sha1 file hash, template hash, boot-aggreate hash
  14  */
  15
  16 #include <linux/kernel.h>
  17 #include <linux/file.h>
  18 #include <linux/crypto.h>
  19 #include <linux/scatterlist.h>
  20 #include <linux/err.h>
  21 #include <linux/slab.h>
  22 #include <crypto/hash.h>
  23 #include <crypto/hash_info.h>
  24 #include "ima.h"
  25
  26 static struct crypto_shash *ima_shash_tfm;
  27
  28 int ima_init_crypto(void)
  29 {
  30         long rc;
  31
  32         ima_shash_tfm = crypto_alloc_shash(hash_algo_name[ima_hash_algo], 0, 0);
  33         if (IS_ERR(ima_shash_tfm)) {
  34                 rc = PTR_ERR(ima_shash_tfm);
  35                 pr_err("Can not allocate %s (reason: %ld)\n",
  36                        hash_algo_name[ima_hash_algo], rc);
  37                 return rc;
  38         }
  39         return 0;
  40 }
  41
  42 static struct crypto_shash *ima_alloc_tfm(enum hash_algo algo)
  43 {
  44         struct crypto_shash *tfm = ima_shash_tfm;
  45         int rc;
  46
  47         if (algo != ima_hash_algo && algo < HASH_ALGO__LAST) {
  48                 tfm = crypto_alloc_shash(hash_algo_name[algo], 0, 0);
  49                 if (IS_ERR(tfm)) {
  50                         rc = PTR_ERR(tfm);
  51                         pr_err("Can not allocate %s (reason: %d)\n",
  52                                hash_algo_name[algo], rc);
  53                 }
  54         }
  55         return tfm;
  56 }
  57
  58 static void ima_free_tfm(struct crypto_shash *tfm)
  59 {
  60         if (tfm != ima_shash_tfm)
  61                 crypto_free_shash(tfm);
  62 }
  63
  64 /*
  65  * Calculate the MD5/SHA1 file digest
  66  */
  67 static int ima_calc_file_hash_tfm(struct file *file,
  68                                   struct ima_digest_data *hash,
  69                                   struct crypto_shash *tfm)
  70 {
  71         loff_t i_size, offset = 0;
  72         char *rbuf;
  73         int rc, read = 0;
  74         struct {
  75                 struct shash_desc shash;
  76                 char ctx[crypto_shash_descsize(tfm)];
  77         } desc;
  78
  79         desc.shash.tfm = tfm;
  80         desc.shash.flags = 0;
  81
  82         hash->length = crypto_shash_digestsize(tfm);
  83
  84         rc = crypto_shash_init(&desc.shash);
  85         if (rc != 0)
  86                 return rc;
  87
  88         rbuf = kzalloc(PAGE_SIZE, GFP_KERNEL);
  89         if (!rbuf) {
  90                 rc = -ENOMEM;
  91                 goto out;
  92         }
  93         if (!(file->f_mode & FMODE_READ)) {
  94                 file->f_mode |= FMODE_READ;
  95                 read = 1;
  96         }
  97         i_size = i_size_read(file_inode(file));
  98         while (offset < i_size) {
  99                 int rbuf_len;
 100
 101                 rbuf_len = kernel_read(file, offset, rbuf, PAGE_SIZE);
 102                 if (rbuf_len < 0) {
 103                         rc = rbuf_len;
 104                         break;
 105                 }
 106                 if (rbuf_len == 0)
 107                         break;
 108                 offset += rbuf_len;
 109
 110                 rc = crypto_shash_update(&desc.shash, rbuf, rbuf_len);
 111                 if (rc)
 112                         break;
 113         }
 114         kfree(rbuf);
 115         if (!rc)
 116                 rc = crypto_shash_final(&desc.shash, hash->digest);
 117         if (read)
 118                 file->f_mode &= ~FMODE_READ;
 119 out:
 120         return rc;
 121 }
 122
 123 int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash)
 124 {
 125         struct crypto_shash *tfm;
 126         int rc;
 127
 128         tfm = ima_alloc_tfm(hash->algo);
 129         if (IS_ERR(tfm))
 130                 return PTR_ERR(tfm);
 131
 132         rc = ima_calc_file_hash_tfm(file, hash, tfm);
 133
 134         ima_free_tfm(tfm);
 135
 136         return rc;
 137 }
 138
 139 /*
 140  * Calculate the hash of a given buffer
 141  */
 142 int ima_calc_buffer_hash(const void *buf, int len, struct ima_digest_data *hash)
 143 {
 144         struct {
 145                 struct shash_desc shash;
 146                 char ctx[crypto_shash_descsize(ima_shash_tfm)];
 147         } desc;
 148
 149         desc.shash.tfm = ima_shash_tfm;
 150         desc.shash.flags = 0;
 151
 152         /* this function uses default algo */
 153         hash->algo = ima_hash_algo;
 154         hash->length = crypto_shash_digestsize(ima_shash_tfm);
 155
 156         return crypto_shash_digest(&desc.shash, buf, len, hash->digest);
 157 }
 158
 159 static void __init ima_pcrread(int idx, u8 *pcr)
 160 {
 161         if (!ima_used_chip)
 162                 return;
 163
 164         if (tpm_pcr_read(TPM_ANY_NUM, idx, pcr) != 0)
 165                 pr_err("IMA: Error Communicating to TPM chip\n");
 166 }
 167
 168 /*
 169  * Calculate the boot aggregate hash
 170  */
 171 int __init ima_calc_boot_aggregate(char *digest)
 172 {
 173         u8 pcr_i[TPM_DIGEST_SIZE];
 174         int rc, i;
 175         struct {
 176                 struct shash_desc shash;
 177                 char ctx[crypto_shash_descsize(ima_shash_tfm)];
 178         } desc;
 179
 180         desc.shash.tfm = ima_shash_tfm;
 181         desc.shash.flags = 0;
 182
 183         rc = crypto_shash_init(&desc.shash);
 184         if (rc != 0)
 185                 return rc;
 186
 187         /* cumulative sha1 over tpm registers 0-7 */
 188         for (i = TPM_PCR0; i < TPM_PCR8; i++) {
 189                 ima_pcrread(i, pcr_i);
 190                 /* now accumulate with current aggregate */
 191                 rc = crypto_shash_update(&desc.shash, pcr_i, TPM_DIGEST_SIZE);
 192         }
 193         if (!rc)
 194                 crypto_shash_final(&desc.shash, digest);
 195         return rc;
 196 }