| /* |
| * linux/fs/ext4/crypto_key.c |
| * |
| * Copyright (C) 2015, Google, Inc. |
| * |
| * This contains encryption key functions for ext4 |
| * |
| * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015. |
| */ |
| |
| #include <keys/encrypted-type.h> |
| #include <keys/user-type.h> |
| #include <linux/random.h> |
| #include <linux/scatterlist.h> |
| #include <uapi/linux/keyctl.h> |
| |
| #include "ext4.h" |
| #include "xattr.h" |
| |
| static void derive_crypt_complete(struct crypto_async_request *req, int rc) |
| { |
| struct ext4_completion_result *ecr = req->data; |
| |
| if (rc == -EINPROGRESS) |
| return; |
| |
| ecr->res = rc; |
| complete(&ecr->completion); |
| } |
| |
| /** |
| * ext4_derive_key_aes() - Derive a key using AES-128-ECB |
| * @deriving_key: Encryption key used for derivation. |
| * @source_key: Source key to which to apply derivation. |
| * @derived_key: Derived key. |
| * |
| * Return: Zero on success; non-zero otherwise. |
| */ |
| static int ext4_derive_key_aes(char deriving_key[EXT4_AES_128_ECB_KEY_SIZE], |
| char source_key[EXT4_AES_256_XTS_KEY_SIZE], |
| char derived_key[EXT4_AES_256_XTS_KEY_SIZE]) |
| { |
| int res = 0; |
| struct ablkcipher_request *req = NULL; |
| DECLARE_EXT4_COMPLETION_RESULT(ecr); |
| struct scatterlist src_sg, dst_sg; |
| struct crypto_ablkcipher *tfm = crypto_alloc_ablkcipher("ecb(aes)", 0, |
| 0); |
| |
| if (IS_ERR(tfm)) { |
| res = PTR_ERR(tfm); |
| tfm = NULL; |
| goto out; |
| } |
| crypto_ablkcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY); |
| req = ablkcipher_request_alloc(tfm, GFP_NOFS); |
| if (!req) { |
| res = -ENOMEM; |
| goto out; |
| } |
| ablkcipher_request_set_callback(req, |
| CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, |
| derive_crypt_complete, &ecr); |
| res = crypto_ablkcipher_setkey(tfm, deriving_key, |
| EXT4_AES_128_ECB_KEY_SIZE); |
| if (res < 0) |
| goto out; |
| sg_init_one(&src_sg, source_key, EXT4_AES_256_XTS_KEY_SIZE); |
| sg_init_one(&dst_sg, derived_key, EXT4_AES_256_XTS_KEY_SIZE); |
| ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, |
| EXT4_AES_256_XTS_KEY_SIZE, NULL); |
| res = crypto_ablkcipher_encrypt(req); |
| if (res == -EINPROGRESS || res == -EBUSY) { |
| BUG_ON(req->base.data != &ecr); |
| wait_for_completion(&ecr.completion); |
| res = ecr.res; |
| } |
| |
| out: |
| if (req) |
| ablkcipher_request_free(req); |
| if (tfm) |
| crypto_free_ablkcipher(tfm); |
| return res; |
| } |
| |
| void ext4_free_crypt_info(struct ext4_crypt_info *ci) |
| { |
| if (!ci) |
| return; |
| |
| if (ci->ci_keyring_key) |
| key_put(ci->ci_keyring_key); |
| crypto_free_ablkcipher(ci->ci_ctfm); |
| kmem_cache_free(ext4_crypt_info_cachep, ci); |
| } |
| |
| void ext4_free_encryption_info(struct inode *inode, |
| struct ext4_crypt_info *ci) |
| { |
| struct ext4_inode_info *ei = EXT4_I(inode); |
| struct ext4_crypt_info *prev; |
| |
| if (ci == NULL) |
| ci = ACCESS_ONCE(ei->i_crypt_info); |
| if (ci == NULL) |
| return; |
| prev = cmpxchg(&ei->i_crypt_info, ci, NULL); |
| if (prev != ci) |
| return; |
| |
| ext4_free_crypt_info(ci); |
| } |
| |
| int _ext4_get_encryption_info(struct inode *inode) |
| { |
| struct ext4_inode_info *ei = EXT4_I(inode); |
| struct ext4_crypt_info *crypt_info; |
| char full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE + |
| (EXT4_KEY_DESCRIPTOR_SIZE * 2) + 1]; |
| struct key *keyring_key = NULL; |
| struct ext4_encryption_key *master_key; |
| struct ext4_encryption_context ctx; |
| const struct user_key_payload *ukp; |
| struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); |
| struct crypto_ablkcipher *ctfm; |
| const char *cipher_str; |
| char raw_key[EXT4_MAX_KEY_SIZE]; |
| char mode; |
| int res; |
| |
| if (!ext4_read_workqueue) { |
| res = ext4_init_crypto(); |
| if (res) |
| return res; |
| } |
| |
| retry: |
| crypt_info = ACCESS_ONCE(ei->i_crypt_info); |
| if (crypt_info) { |
| if (!crypt_info->ci_keyring_key || |
| key_validate(crypt_info->ci_keyring_key) == 0) |
| return 0; |
| ext4_free_encryption_info(inode, crypt_info); |
| goto retry; |
| } |
| |
| res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION, |
| EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, |
| &ctx, sizeof(ctx)); |
| if (res < 0) { |
| if (!DUMMY_ENCRYPTION_ENABLED(sbi)) |
| return res; |
| ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS; |
| ctx.filenames_encryption_mode = |
| EXT4_ENCRYPTION_MODE_AES_256_CTS; |
| ctx.flags = 0; |
| } else if (res != sizeof(ctx)) |
| return -EINVAL; |
| res = 0; |
| |
| crypt_info = kmem_cache_alloc(ext4_crypt_info_cachep, GFP_KERNEL); |
| if (!crypt_info) |
| return -ENOMEM; |
| |
| crypt_info->ci_flags = ctx.flags; |
| crypt_info->ci_data_mode = ctx.contents_encryption_mode; |
| crypt_info->ci_filename_mode = ctx.filenames_encryption_mode; |
| crypt_info->ci_ctfm = NULL; |
| crypt_info->ci_keyring_key = NULL; |
| memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor, |
| sizeof(crypt_info->ci_master_key)); |
| if (S_ISREG(inode->i_mode)) |
| mode = crypt_info->ci_data_mode; |
| else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) |
| mode = crypt_info->ci_filename_mode; |
| else |
| BUG(); |
| switch (mode) { |
| case EXT4_ENCRYPTION_MODE_AES_256_XTS: |
| cipher_str = "xts(aes)"; |
| break; |
| case EXT4_ENCRYPTION_MODE_AES_256_CTS: |
| cipher_str = "cts(cbc(aes))"; |
| break; |
| default: |
| printk_once(KERN_WARNING |
| "ext4: unsupported key mode %d (ino %u)\n", |
| mode, (unsigned) inode->i_ino); |
| res = -ENOKEY; |
| goto out; |
| } |
| if (DUMMY_ENCRYPTION_ENABLED(sbi)) { |
| memset(raw_key, 0x42, EXT4_AES_256_XTS_KEY_SIZE); |
| goto got_key; |
| } |
| memcpy(full_key_descriptor, EXT4_KEY_DESC_PREFIX, |
| EXT4_KEY_DESC_PREFIX_SIZE); |
| sprintf(full_key_descriptor + EXT4_KEY_DESC_PREFIX_SIZE, |
| "%*phN", EXT4_KEY_DESCRIPTOR_SIZE, |
| ctx.master_key_descriptor); |
| full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE + |
| (2 * EXT4_KEY_DESCRIPTOR_SIZE)] = '\0'; |
| keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL); |
| if (IS_ERR(keyring_key)) { |
| res = PTR_ERR(keyring_key); |
| keyring_key = NULL; |
| goto out; |
| } |
| crypt_info->ci_keyring_key = keyring_key; |
| BUG_ON(keyring_key->type != &key_type_logon); |
| ukp = user_key_payload(keyring_key); |
| if (ukp->datalen != sizeof(struct ext4_encryption_key)) { |
| res = -EINVAL; |
| goto out; |
| } |
| master_key = (struct ext4_encryption_key *)ukp->data; |
| BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE != |
| EXT4_KEY_DERIVATION_NONCE_SIZE); |
| BUG_ON(master_key->size != EXT4_AES_256_XTS_KEY_SIZE); |
| res = ext4_derive_key_aes(ctx.nonce, master_key->raw, |
| raw_key); |
| if (res) |
| goto out; |
| got_key: |
| ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0); |
| if (!ctfm || IS_ERR(ctfm)) { |
| res = ctfm ? PTR_ERR(ctfm) : -ENOMEM; |
| printk(KERN_DEBUG |
| "%s: error %d (inode %u) allocating crypto tfm\n", |
| __func__, res, (unsigned) inode->i_ino); |
| goto out; |
| } |
| crypt_info->ci_ctfm = ctfm; |
| crypto_ablkcipher_clear_flags(ctfm, ~0); |
| crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm), |
| CRYPTO_TFM_REQ_WEAK_KEY); |
| res = crypto_ablkcipher_setkey(ctfm, raw_key, |
| ext4_encryption_key_size(mode)); |
| if (res) |
| goto out; |
| memzero_explicit(raw_key, sizeof(raw_key)); |
| if (cmpxchg(&ei->i_crypt_info, NULL, crypt_info) != NULL) { |
| ext4_free_crypt_info(crypt_info); |
| goto retry; |
| } |
| return 0; |
| |
| out: |
| if (res == -ENOKEY) |
| res = 0; |
| ext4_free_crypt_info(crypt_info); |
| memzero_explicit(raw_key, sizeof(raw_key)); |
| return res; |
| } |
| |
| int ext4_has_encryption_key(struct inode *inode) |
| { |
| struct ext4_inode_info *ei = EXT4_I(inode); |
| |
| return (ei->i_crypt_info != NULL); |
| } |