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 /** 31 * ima_kernel_read - read file content 32 * 33 * This is a function for reading file content instead of kernel_read(). 34 * It does not perform locking checks to ensure it cannot be blocked. 35 * It does not perform security checks because it is irrelevant for IMA. 36 * 37 */ 38 static int ima_kernel_read(struct file *file, loff_t offset, 39 char *addr, unsigned long count) 40 { 41 mm_segment_t old_fs; 42 char __user *buf = addr; 43 ssize_t ret; 44 45 if (!(file->f_mode & FMODE_READ)) 46 return -EBADF; 47 if (!file->f_op->read && !file->f_op->aio_read) 48 return -EINVAL; 49 50 old_fs = get_fs(); 51 set_fs(get_ds()); 52 if (file->f_op->read) 53 ret = file->f_op->read(file, buf, count, &offset); 54 else 55 ret = do_sync_read(file, buf, count, &offset); 56 set_fs(old_fs); 57 return ret; 58 } 59 60 int ima_init_crypto(void) 61 { 62 long rc; 63 64 ima_shash_tfm = crypto_alloc_shash(hash_algo_name[ima_hash_algo], 0, 0); 65 if (IS_ERR(ima_shash_tfm)) { 66 rc = PTR_ERR(ima_shash_tfm); 67 pr_err("Can not allocate %s (reason: %ld)\n", 68 hash_algo_name[ima_hash_algo], rc); 69 return rc; 70 } 71 return 0; 72 } 73 74 static struct crypto_shash *ima_alloc_tfm(enum hash_algo algo) 75 { 76 struct crypto_shash *tfm = ima_shash_tfm; 77 int rc; 78 79 if (algo != ima_hash_algo && algo < HASH_ALGO__LAST) { 80 tfm = crypto_alloc_shash(hash_algo_name[algo], 0, 0); 81 if (IS_ERR(tfm)) { 82 rc = PTR_ERR(tfm); 83 pr_err("Can not allocate %s (reason: %d)\n", 84 hash_algo_name[algo], rc); 85 } 86 } 87 return tfm; 88 } 89 90 static void ima_free_tfm(struct crypto_shash *tfm) 91 { 92 if (tfm != ima_shash_tfm) 93 crypto_free_shash(tfm); 94 } 95 96 /* 97 * Calculate the MD5/SHA1 file digest 98 */ 99 static int ima_calc_file_hash_tfm(struct file *file, 100 struct ima_digest_data *hash, 101 struct crypto_shash *tfm) 102 { 103 loff_t i_size, offset = 0; 104 char *rbuf; 105 int rc, read = 0; 106 struct { 107 struct shash_desc shash; 108 char ctx[crypto_shash_descsize(tfm)]; 109 } desc; 110 111 desc.shash.tfm = tfm; 112 desc.shash.flags = 0; 113 114 hash->length = crypto_shash_digestsize(tfm); 115 116 rc = crypto_shash_init(&desc.shash); 117 if (rc != 0) 118 return rc; 119 120 i_size = i_size_read(file_inode(file)); 121 122 if (i_size == 0) 123 goto out; 124 125 rbuf = kzalloc(PAGE_SIZE, GFP_KERNEL); 126 if (!rbuf) 127 return -ENOMEM; 128 129 if (!(file->f_mode & FMODE_READ)) { 130 file->f_mode |= FMODE_READ; 131 read = 1; 132 } 133 134 while (offset < i_size) { 135 int rbuf_len; 136 137 rbuf_len = ima_kernel_read(file, offset, rbuf, PAGE_SIZE); 138 if (rbuf_len < 0) { 139 rc = rbuf_len; 140 break; 141 } 142 if (rbuf_len == 0) 143 break; 144 offset += rbuf_len; 145 146 rc = crypto_shash_update(&desc.shash, rbuf, rbuf_len); 147 if (rc) 148 break; 149 } 150 if (read) 151 file->f_mode &= ~FMODE_READ; 152 kfree(rbuf); 153 out: 154 if (!rc) 155 rc = crypto_shash_final(&desc.shash, hash->digest); 156 return rc; 157 } 158 159 int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash) 160 { 161 struct crypto_shash *tfm; 162 int rc; 163 164 tfm = ima_alloc_tfm(hash->algo); 165 if (IS_ERR(tfm)) 166 return PTR_ERR(tfm); 167 168 rc = ima_calc_file_hash_tfm(file, hash, tfm); 169 170 ima_free_tfm(tfm); 171 172 return rc; 173 } 174 175 /* 176 * Calculate the hash of template data 177 */ 178 static int ima_calc_field_array_hash_tfm(struct ima_field_data *field_data, 179 struct ima_template_desc *td, 180 int num_fields, 181 struct ima_digest_data *hash, 182 struct crypto_shash *tfm) 183 { 184 struct { 185 struct shash_desc shash; 186 char ctx[crypto_shash_descsize(tfm)]; 187 } desc; 188 int rc, i; 189 190 desc.shash.tfm = tfm; 191 desc.shash.flags = 0; 192 193 hash->length = crypto_shash_digestsize(tfm); 194 195 rc = crypto_shash_init(&desc.shash); 196 if (rc != 0) 197 return rc; 198 199 for (i = 0; i < num_fields; i++) { 200 u8 buffer[IMA_EVENT_NAME_LEN_MAX + 1] = { 0 }; 201 u8 *data_to_hash = field_data[i].data; 202 u32 datalen = field_data[i].len; 203 204 if (strcmp(td->name, IMA_TEMPLATE_IMA_NAME) != 0) { 205 rc = crypto_shash_update(&desc.shash, 206 (const u8 *) &field_data[i].len, 207 sizeof(field_data[i].len)); 208 if (rc) 209 break; 210 } else if (strcmp(td->fields[i]->field_id, "n") == 0) { 211 memcpy(buffer, data_to_hash, datalen); 212 data_to_hash = buffer; 213 datalen = IMA_EVENT_NAME_LEN_MAX + 1; 214 } 215 rc = crypto_shash_update(&desc.shash, data_to_hash, datalen); 216 if (rc) 217 break; 218 } 219 220 if (!rc) 221 rc = crypto_shash_final(&desc.shash, hash->digest); 222 223 return rc; 224 } 225 226 int ima_calc_field_array_hash(struct ima_field_data *field_data, 227 struct ima_template_desc *desc, int num_fields, 228 struct ima_digest_data *hash) 229 { 230 struct crypto_shash *tfm; 231 int rc; 232 233 tfm = ima_alloc_tfm(hash->algo); 234 if (IS_ERR(tfm)) 235 return PTR_ERR(tfm); 236 237 rc = ima_calc_field_array_hash_tfm(field_data, desc, num_fields, 238 hash, tfm); 239 240 ima_free_tfm(tfm); 241 242 return rc; 243 } 244 245 static void __init ima_pcrread(int idx, u8 *pcr) 246 { 247 if (!ima_used_chip) 248 return; 249 250 if (tpm_pcr_read(TPM_ANY_NUM, idx, pcr) != 0) 251 pr_err("Error Communicating to TPM chip\n"); 252 } 253 254 /* 255 * Calculate the boot aggregate hash 256 */ 257 static int __init ima_calc_boot_aggregate_tfm(char *digest, 258 struct crypto_shash *tfm) 259 { 260 u8 pcr_i[TPM_DIGEST_SIZE]; 261 int rc, i; 262 struct { 263 struct shash_desc shash; 264 char ctx[crypto_shash_descsize(tfm)]; 265 } desc; 266 267 desc.shash.tfm = tfm; 268 desc.shash.flags = 0; 269 270 rc = crypto_shash_init(&desc.shash); 271 if (rc != 0) 272 return rc; 273 274 /* cumulative sha1 over tpm registers 0-7 */ 275 for (i = TPM_PCR0; i < TPM_PCR8; i++) { 276 ima_pcrread(i, pcr_i); 277 /* now accumulate with current aggregate */ 278 rc = crypto_shash_update(&desc.shash, pcr_i, TPM_DIGEST_SIZE); 279 } 280 if (!rc) 281 crypto_shash_final(&desc.shash, digest); 282 return rc; 283 } 284 285 int __init ima_calc_boot_aggregate(struct ima_digest_data *hash) 286 { 287 struct crypto_shash *tfm; 288 int rc; 289 290 tfm = ima_alloc_tfm(hash->algo); 291 if (IS_ERR(tfm)) 292 return PTR_ERR(tfm); 293 294 hash->length = crypto_shash_digestsize(tfm); 295 rc = ima_calc_boot_aggregate_tfm(hash->digest, tfm); 296 297 ima_free_tfm(tfm); 298 299 return rc; 300 } 301