1/* 2 * linux/fs/ext4/crypto_key.c 3 * 4 * Copyright (C) 2015, Google, Inc. 5 * 6 * This contains encryption key functions for ext4 7 * 8 * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015. 9 */ 10 11#include <keys/encrypted-type.h> 12#include <keys/user-type.h> 13#include <linux/random.h> 14#include <linux/scatterlist.h> 15#include <uapi/linux/keyctl.h> 16 17#include "ext4.h" 18#include "xattr.h" 19 20static void derive_crypt_complete(struct crypto_async_request *req, int rc) 21{ 22 struct ext4_completion_result *ecr = req->data; 23 24 if (rc == -EINPROGRESS) 25 return; 26 27 ecr->res = rc; 28 complete(&ecr->completion); 29} 30 31/** 32 * ext4_derive_key_aes() - Derive a key using AES-128-ECB 33 * @deriving_key: Encryption key used for derivation. 34 * @source_key: Source key to which to apply derivation. 35 * @derived_key: Derived key. 36 * 37 * Return: Zero on success; non-zero otherwise. 38 */ 39static int ext4_derive_key_aes(char deriving_key[EXT4_AES_128_ECB_KEY_SIZE], 40 char source_key[EXT4_AES_256_XTS_KEY_SIZE], 41 char derived_key[EXT4_AES_256_XTS_KEY_SIZE]) 42{ 43 int res = 0; 44 struct ablkcipher_request *req = NULL; 45 DECLARE_EXT4_COMPLETION_RESULT(ecr); 46 struct scatterlist src_sg, dst_sg; 47 struct crypto_ablkcipher *tfm = crypto_alloc_ablkcipher("ecb(aes)", 0, 48 0); 49 50 if (IS_ERR(tfm)) { 51 res = PTR_ERR(tfm); 52 tfm = NULL; 53 goto out; 54 } 55 crypto_ablkcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY); 56 req = ablkcipher_request_alloc(tfm, GFP_NOFS); 57 if (!req) { 58 res = -ENOMEM; 59 goto out; 60 } 61 ablkcipher_request_set_callback(req, 62 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, 63 derive_crypt_complete, &ecr); 64 res = crypto_ablkcipher_setkey(tfm, deriving_key, 65 EXT4_AES_128_ECB_KEY_SIZE); 66 if (res < 0) 67 goto out; 68 sg_init_one(&src_sg, source_key, EXT4_AES_256_XTS_KEY_SIZE); 69 sg_init_one(&dst_sg, derived_key, EXT4_AES_256_XTS_KEY_SIZE); 70 ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, 71 EXT4_AES_256_XTS_KEY_SIZE, NULL); 72 res = crypto_ablkcipher_encrypt(req); 73 if (res == -EINPROGRESS || res == -EBUSY) { 74 wait_for_completion(&ecr.completion); 75 res = ecr.res; 76 } 77 78out: 79 if (req) 80 ablkcipher_request_free(req); 81 if (tfm) 82 crypto_free_ablkcipher(tfm); 83 return res; 84} 85 86void ext4_free_crypt_info(struct ext4_crypt_info *ci) 87{ 88 if (!ci) 89 return; 90 91 if (ci->ci_keyring_key) 92 key_put(ci->ci_keyring_key); 93 crypto_free_ablkcipher(ci->ci_ctfm); 94 kmem_cache_free(ext4_crypt_info_cachep, ci); 95} 96 97void ext4_free_encryption_info(struct inode *inode, 98 struct ext4_crypt_info *ci) 99{ 100 struct ext4_inode_info *ei = EXT4_I(inode); 101 struct ext4_crypt_info *prev; 102 103 if (ci == NULL) 104 ci = ACCESS_ONCE(ei->i_crypt_info); 105 if (ci == NULL) 106 return; 107 prev = cmpxchg(&ei->i_crypt_info, ci, NULL); 108 if (prev != ci) 109 return; 110 111 ext4_free_crypt_info(ci); 112} 113 114int _ext4_get_encryption_info(struct inode *inode) 115{ 116 struct ext4_inode_info *ei = EXT4_I(inode); 117 struct ext4_crypt_info *crypt_info; 118 char full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE + 119 (EXT4_KEY_DESCRIPTOR_SIZE * 2) + 1]; 120 struct key *keyring_key = NULL; 121 struct ext4_encryption_key *master_key; 122 struct ext4_encryption_context ctx; 123 const struct user_key_payload *ukp; 124 struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); 125 struct crypto_ablkcipher *ctfm; 126 const char *cipher_str; 127 char raw_key[EXT4_MAX_KEY_SIZE]; 128 char mode; 129 int res; 130 131 if (!ext4_read_workqueue) { 132 res = ext4_init_crypto(); 133 if (res) 134 return res; 135 } 136 137retry: 138 crypt_info = ACCESS_ONCE(ei->i_crypt_info); 139 if (crypt_info) { 140 if (!crypt_info->ci_keyring_key || 141 key_validate(crypt_info->ci_keyring_key) == 0) 142 return 0; 143 ext4_free_encryption_info(inode, crypt_info); 144 goto retry; 145 } 146 147 res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION, 148 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, 149 &ctx, sizeof(ctx)); 150 if (res < 0) { 151 if (!DUMMY_ENCRYPTION_ENABLED(sbi)) 152 return res; 153 ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS; 154 ctx.filenames_encryption_mode = 155 EXT4_ENCRYPTION_MODE_AES_256_CTS; 156 ctx.flags = 0; 157 } else if (res != sizeof(ctx)) 158 return -EINVAL; 159 res = 0; 160 161 crypt_info = kmem_cache_alloc(ext4_crypt_info_cachep, GFP_KERNEL); 162 if (!crypt_info) 163 return -ENOMEM; 164 165 crypt_info->ci_flags = ctx.flags; 166 crypt_info->ci_data_mode = ctx.contents_encryption_mode; 167 crypt_info->ci_filename_mode = ctx.filenames_encryption_mode; 168 crypt_info->ci_ctfm = NULL; 169 crypt_info->ci_keyring_key = NULL; 170 memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor, 171 sizeof(crypt_info->ci_master_key)); 172 if (S_ISREG(inode->i_mode)) 173 mode = crypt_info->ci_data_mode; 174 else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) 175 mode = crypt_info->ci_filename_mode; 176 else 177 BUG(); 178 switch (mode) { 179 case EXT4_ENCRYPTION_MODE_AES_256_XTS: 180 cipher_str = "xts(aes)"; 181 break; 182 case EXT4_ENCRYPTION_MODE_AES_256_CTS: 183 cipher_str = "cts(cbc(aes))"; 184 break; 185 default: 186 printk_once(KERN_WARNING 187 "ext4: unsupported key mode %d (ino %u)\n", 188 mode, (unsigned) inode->i_ino); 189 res = -ENOKEY; 190 goto out; 191 } 192 if (DUMMY_ENCRYPTION_ENABLED(sbi)) { 193 memset(raw_key, 0x42, EXT4_AES_256_XTS_KEY_SIZE); 194 goto got_key; 195 } 196 memcpy(full_key_descriptor, EXT4_KEY_DESC_PREFIX, 197 EXT4_KEY_DESC_PREFIX_SIZE); 198 sprintf(full_key_descriptor + EXT4_KEY_DESC_PREFIX_SIZE, 199 "%*phN", EXT4_KEY_DESCRIPTOR_SIZE, 200 ctx.master_key_descriptor); 201 full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE + 202 (2 * EXT4_KEY_DESCRIPTOR_SIZE)] = '\0'; 203 keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL); 204 if (IS_ERR(keyring_key)) { 205 res = PTR_ERR(keyring_key); 206 keyring_key = NULL; 207 goto out; 208 } 209 crypt_info->ci_keyring_key = keyring_key; 210 if (keyring_key->type != &key_type_logon) { 211 printk_once(KERN_WARNING 212 "ext4: key type must be logon\n"); 213 res = -ENOKEY; 214 goto out; 215 } 216 down_read(&keyring_key->sem); 217 ukp = user_key_payload(keyring_key); 218 if (ukp->datalen != sizeof(struct ext4_encryption_key)) { 219 res = -EINVAL; 220 up_read(&keyring_key->sem); 221 goto out; 222 } 223 master_key = (struct ext4_encryption_key *)ukp->data; 224 BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE != 225 EXT4_KEY_DERIVATION_NONCE_SIZE); 226 if (master_key->size != EXT4_AES_256_XTS_KEY_SIZE) { 227 printk_once(KERN_WARNING 228 "ext4: key size incorrect: %d\n", 229 master_key->size); 230 res = -ENOKEY; 231 up_read(&keyring_key->sem); 232 goto out; 233 } 234 res = ext4_derive_key_aes(ctx.nonce, master_key->raw, 235 raw_key); 236 up_read(&keyring_key->sem); 237 if (res) 238 goto out; 239got_key: 240 ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0); 241 if (!ctfm || IS_ERR(ctfm)) { 242 res = ctfm ? PTR_ERR(ctfm) : -ENOMEM; 243 printk(KERN_DEBUG 244 "%s: error %d (inode %u) allocating crypto tfm\n", 245 __func__, res, (unsigned) inode->i_ino); 246 goto out; 247 } 248 crypt_info->ci_ctfm = ctfm; 249 crypto_ablkcipher_clear_flags(ctfm, ~0); 250 crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm), 251 CRYPTO_TFM_REQ_WEAK_KEY); 252 res = crypto_ablkcipher_setkey(ctfm, raw_key, 253 ext4_encryption_key_size(mode)); 254 if (res) 255 goto out; 256 memzero_explicit(raw_key, sizeof(raw_key)); 257 if (cmpxchg(&ei->i_crypt_info, NULL, crypt_info) != NULL) { 258 ext4_free_crypt_info(crypt_info); 259 goto retry; 260 } 261 return 0; 262 263out: 264 if (res == -ENOKEY) 265 res = 0; 266 ext4_free_crypt_info(crypt_info); 267 memzero_explicit(raw_key, sizeof(raw_key)); 268 return res; 269} 270 271int ext4_has_encryption_key(struct inode *inode) 272{ 273 struct ext4_inode_info *ei = EXT4_I(inode); 274 275 return (ei->i_crypt_info != NULL); 276} 277