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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  17
  18 #include <linux/kernel.h>
  19 #include <linux/file.h>
  20 #include <linux/crypto.h>
  21 #include <linux/scatterlist.h>
  22 #include <linux/err.h>
  23 #include <linux/slab.h>
  24 #include <crypto/hash.h>
  25 #include <crypto/hash_info.h>
  26 #include "ima.h"
  27
  28 static struct crypto_shash *ima_shash_tfm;
  29
  30 int ima_init_crypto(void)
  31 {
  32         long rc;
  33
  34         ima_shash_tfm = crypto_alloc_shash(hash_algo_name[ima_hash_algo], 0, 0);
  35         if (IS_ERR(ima_shash_tfm)) {
  36                 rc = PTR_ERR(ima_shash_tfm);
  37                 pr_err("Can not allocate %s (reason: %ld)\n",
  38                        hash_algo_name[ima_hash_algo], rc);
  39                 return rc;
  40         }
  41         return 0;
  42 }
  43
  44 static struct crypto_shash *ima_alloc_tfm(enum hash_algo algo)
  45 {
  46         struct crypto_shash *tfm = ima_shash_tfm;
  47         int rc;
  48
  49         if (algo != ima_hash_algo && algo < HASH_ALGO__LAST) {
  50                 tfm = crypto_alloc_shash(hash_algo_name[algo], 0, 0);
  51                 if (IS_ERR(tfm)) {
  52                         rc = PTR_ERR(tfm);
  53                         pr_err("Can not allocate %s (reason: %d)\n",
  54                                hash_algo_name[algo], rc);
  55                 }
  56         }
  57         return tfm;
  58 }
  59
  60 static void ima_free_tfm(struct crypto_shash *tfm)
  61 {
  62         if (tfm != ima_shash_tfm)
  63                 crypto_free_shash(tfm);
  64 }
  65
  66 /*
  67  * Calculate the MD5/SHA1 file digest
  68  */
  69 static int ima_calc_file_hash_tfm(struct file *file,
  70                                   struct ima_digest_data *hash,
  71                                   struct crypto_shash *tfm)
  72 {
  73         loff_t i_size, offset = 0;
  74         char *rbuf;
  75         int rc, read = 0;
  76         struct {
  77                 struct shash_desc shash;
  78                 char ctx[crypto_shash_descsize(tfm)];
  79         } desc;
  80
  81         desc.shash.tfm = tfm;
  82         desc.shash.flags = 0;
  83
  84         hash->length = crypto_shash_digestsize(tfm);
  85
  86         rc = crypto_shash_init(&desc.shash);
  87         if (rc != 0)
  88                 return rc;
  89
  90         i_size = i_size_read(file_inode(file));
  91
  92         if (i_size == 0)
  93                 goto out;
  94
  95         rbuf = kzalloc(PAGE_SIZE, GFP_KERNEL);
  96         if (!rbuf)
  97                 return -ENOMEM;
  98
  99         if (!(file->f_mode & FMODE_READ)) {
 100                 file->f_mode |= FMODE_READ;
 101                 read = 1;
 102         }
 103
 104         while (offset < i_size) {
 105                 int rbuf_len;
 106
 107                 rbuf_len = kernel_read(file, offset, rbuf, PAGE_SIZE);
 108                 if (rbuf_len < 0) {
 109                         rc = rbuf_len;
 110                         break;
 111                 }
 112                 if (rbuf_len == 0)
 113                         break;
 114                 offset += rbuf_len;
 115
 116                 rc = crypto_shash_update(&desc.shash, rbuf, rbuf_len);
 117                 if (rc)
 118                         break;
 119         }
 120         if (read)
 121                 file->f_mode &= ~FMODE_READ;
 122         kfree(rbuf);
 123 out:
 124         if (!rc)
 125                 rc = crypto_shash_final(&desc.shash, hash->digest);
 126         return rc;
 127 }
 128
 129 int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash)
 130 {
 131         struct crypto_shash *tfm;
 132         int rc;
 133
 134         tfm = ima_alloc_tfm(hash->algo);
 135         if (IS_ERR(tfm))
 136                 return PTR_ERR(tfm);
 137
 138         rc = ima_calc_file_hash_tfm(file, hash, tfm);
 139
 140         ima_free_tfm(tfm);
 141
 142         return rc;
 143 }
 144
 145 /*
 146  * Calculate the hash of template data
 147  */
 148 static int ima_calc_field_array_hash_tfm(struct ima_field_data *field_data,
 149                                          struct ima_template_desc *td,
 150                                          int num_fields,
 151                                          struct ima_digest_data *hash,
 152                                          struct crypto_shash *tfm)
 153 {
 154         struct {
 155                 struct shash_desc shash;
 156                 char ctx[crypto_shash_descsize(tfm)];
 157         } desc;
 158         int rc, i;
 159
 160         desc.shash.tfm = tfm;
 161         desc.shash.flags = 0;
 162
 163         hash->length = crypto_shash_digestsize(tfm);
 164
 165         rc = crypto_shash_init(&desc.shash);
 166         if (rc != 0)
 167                 return rc;
 168
 169         for (i = 0; i < num_fields; i++) {
 170                 u8 buffer[IMA_EVENT_NAME_LEN_MAX + 1] = { 0 };
 171                 u8 *data_to_hash = field_data[i].data;
 172                 u32 datalen = field_data[i].len;
 173
 174                 if (strcmp(td->name, IMA_TEMPLATE_IMA_NAME) != 0) {
 175                         rc = crypto_shash_update(&desc.shash,
 176                                                 (const u8 *) &field_data[i].len,
 177                                                 sizeof(field_data[i].len));
 178                         if (rc)
 179                                 break;
 180                 } else if (strcmp(td->fields[i]->field_id, "n") == 0) {
 181                         memcpy(buffer, data_to_hash, datalen);
 182                         data_to_hash = buffer;
 183                         datalen = IMA_EVENT_NAME_LEN_MAX + 1;
 184                 }
 185                 rc = crypto_shash_update(&desc.shash, data_to_hash, datalen);
 186                 if (rc)
 187                         break;
 188         }
 189
 190         if (!rc)
 191                 rc = crypto_shash_final(&desc.shash, hash->digest);
 192
 193         return rc;
 194 }
 195
 196 int ima_calc_field_array_hash(struct ima_field_data *field_data,
 197                               struct ima_template_desc *desc, int num_fields,
 198                               struct ima_digest_data *hash)
 199 {
 200         struct crypto_shash *tfm;
 201         int rc;
 202
 203         tfm = ima_alloc_tfm(hash->algo);
 204         if (IS_ERR(tfm))
 205                 return PTR_ERR(tfm);
 206
 207         rc = ima_calc_field_array_hash_tfm(field_data, desc, num_fields,
 208                                            hash, tfm);
 209
 210         ima_free_tfm(tfm);
 211
 212         return rc;
 213 }
 214
 215 static void __init ima_pcrread(int idx, u8 *pcr)
 216 {
 217         if (!ima_used_chip)
 218                 return;
 219
 220         if (tpm_pcr_read(TPM_ANY_NUM, idx, pcr) != 0)
 221                 pr_err("Error Communicating to TPM chip\n");
 222 }
 223
 224 /*
 225  * Calculate the boot aggregate hash
 226  */
 227 static int __init ima_calc_boot_aggregate_tfm(char *digest,
 228                                               struct crypto_shash *tfm)
 229 {
 230         u8 pcr_i[TPM_DIGEST_SIZE];
 231         int rc, i;
 232         struct {
 233                 struct shash_desc shash;
 234                 char ctx[crypto_shash_descsize(tfm)];
 235         } desc;
 236
 237         desc.shash.tfm = tfm;
 238         desc.shash.flags = 0;
 239
 240         rc = crypto_shash_init(&desc.shash);
 241         if (rc != 0)
 242                 return rc;
 243
 244         /* cumulative sha1 over tpm registers 0-7 */
 245         for (i = TPM_PCR0; i < TPM_PCR8; i++) {
 246                 ima_pcrread(i, pcr_i);
 247                 /* now accumulate with current aggregate */
 248                 rc = crypto_shash_update(&desc.shash, pcr_i, TPM_DIGEST_SIZE);
 249         }
 250         if (!rc)
 251                 crypto_shash_final(&desc.shash, digest);
 252         return rc;
 253 }
 254
 255 int __init ima_calc_boot_aggregate(struct ima_digest_data *hash)
 256 {
 257         struct crypto_shash *tfm;
 258         int rc;
 259
 260         tfm = ima_alloc_tfm(hash->algo);
 261         if (IS_ERR(tfm))
 262                 return PTR_ERR(tfm);
 263
 264         hash->length = crypto_shash_digestsize(tfm);
 265         rc = ima_calc_boot_aggregate_tfm(hash->digest, tfm);
 266
 267         ima_free_tfm(tfm);
 268
 269         return rc;
 270 }