Michael Halcrow | 88bd6cc | 2015-04-12 00:55:06 -0400 | [diff] [blame] | 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 | |
| 20 | static 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 derivatio. |
| 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 | */ |
| 39 | static 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 | BUG_ON(req->base.data != &ecr); |
| 75 | wait_for_completion(&ecr.completion); |
| 76 | res = ecr.res; |
| 77 | } |
| 78 | |
| 79 | out: |
| 80 | if (req) |
| 81 | ablkcipher_request_free(req); |
| 82 | if (tfm) |
| 83 | crypto_free_ablkcipher(tfm); |
| 84 | return res; |
| 85 | } |
| 86 | |
| 87 | /** |
| 88 | * ext4_generate_encryption_key() - generates an encryption key |
| 89 | * @inode: The inode to generate the encryption key for. |
| 90 | */ |
| 91 | int ext4_generate_encryption_key(struct inode *inode) |
| 92 | { |
| 93 | struct ext4_inode_info *ei = EXT4_I(inode); |
| 94 | struct ext4_encryption_key *crypt_key = &ei->i_encryption_key; |
| 95 | char full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE + |
| 96 | (EXT4_KEY_DESCRIPTOR_SIZE * 2) + 1]; |
| 97 | struct key *keyring_key = NULL; |
| 98 | struct ext4_encryption_key *master_key; |
| 99 | struct ext4_encryption_context ctx; |
| 100 | struct user_key_payload *ukp; |
Theodore Ts'o | 6ddb244 | 2015-04-16 01:56:00 -0400 | [diff] [blame^] | 101 | struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); |
Michael Halcrow | 88bd6cc | 2015-04-12 00:55:06 -0400 | [diff] [blame] | 102 | int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION, |
| 103 | EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, |
| 104 | &ctx, sizeof(ctx)); |
| 105 | |
| 106 | if (res != sizeof(ctx)) { |
| 107 | if (res > 0) |
| 108 | res = -EINVAL; |
| 109 | goto out; |
| 110 | } |
| 111 | res = 0; |
| 112 | |
Theodore Ts'o | 6ddb244 | 2015-04-16 01:56:00 -0400 | [diff] [blame^] | 113 | if (S_ISREG(inode->i_mode)) |
| 114 | crypt_key->mode = ctx.contents_encryption_mode; |
| 115 | else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) |
| 116 | crypt_key->mode = ctx.filenames_encryption_mode; |
| 117 | else { |
| 118 | printk(KERN_ERR "ext4 crypto: Unsupported inode type.\n"); |
| 119 | BUG(); |
| 120 | } |
| 121 | crypt_key->size = ext4_encryption_key_size(crypt_key->mode); |
| 122 | BUG_ON(!crypt_key->size); |
| 123 | if (DUMMY_ENCRYPTION_ENABLED(sbi)) { |
| 124 | memset(crypt_key->raw, 0x42, EXT4_AES_256_XTS_KEY_SIZE); |
| 125 | goto out; |
| 126 | } |
Michael Halcrow | 88bd6cc | 2015-04-12 00:55:06 -0400 | [diff] [blame] | 127 | memcpy(full_key_descriptor, EXT4_KEY_DESC_PREFIX, |
| 128 | EXT4_KEY_DESC_PREFIX_SIZE); |
| 129 | sprintf(full_key_descriptor + EXT4_KEY_DESC_PREFIX_SIZE, |
| 130 | "%*phN", EXT4_KEY_DESCRIPTOR_SIZE, |
| 131 | ctx.master_key_descriptor); |
| 132 | full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE + |
| 133 | (2 * EXT4_KEY_DESCRIPTOR_SIZE)] = '\0'; |
| 134 | keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL); |
| 135 | if (IS_ERR(keyring_key)) { |
| 136 | res = PTR_ERR(keyring_key); |
| 137 | keyring_key = NULL; |
| 138 | goto out; |
| 139 | } |
| 140 | BUG_ON(keyring_key->type != &key_type_logon); |
| 141 | ukp = ((struct user_key_payload *)keyring_key->payload.data); |
| 142 | if (ukp->datalen != sizeof(struct ext4_encryption_key)) { |
| 143 | res = -EINVAL; |
| 144 | goto out; |
| 145 | } |
| 146 | master_key = (struct ext4_encryption_key *)ukp->data; |
Michael Halcrow | 88bd6cc | 2015-04-12 00:55:06 -0400 | [diff] [blame] | 147 | BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE != |
| 148 | EXT4_KEY_DERIVATION_NONCE_SIZE); |
| 149 | BUG_ON(master_key->size != EXT4_AES_256_XTS_KEY_SIZE); |
Michael Halcrow | 88bd6cc | 2015-04-12 00:55:06 -0400 | [diff] [blame] | 150 | res = ext4_derive_key_aes(ctx.nonce, master_key->raw, crypt_key->raw); |
| 151 | out: |
| 152 | if (keyring_key) |
| 153 | key_put(keyring_key); |
| 154 | if (res < 0) |
| 155 | crypt_key->mode = EXT4_ENCRYPTION_MODE_INVALID; |
| 156 | return res; |
| 157 | } |
| 158 | |
| 159 | int ext4_has_encryption_key(struct inode *inode) |
| 160 | { |
| 161 | struct ext4_inode_info *ei = EXT4_I(inode); |
| 162 | struct ext4_encryption_key *crypt_key = &ei->i_encryption_key; |
| 163 | |
| 164 | return (crypt_key->mode != EXT4_ENCRYPTION_MODE_INVALID); |
| 165 | } |