/* * 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 <crypto/skcipher.h> #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 skcipher_request *req = NULL; DECLARE_EXT4_COMPLETION_RESULT(ecr); struct scatterlist src_sg, dst_sg; struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0); if (IS_ERR(tfm)) { res = PTR_ERR(tfm); tfm = NULL; goto out; } crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY); req = skcipher_request_alloc(tfm, GFP_NOFS); if (!req) { res = -ENOMEM; goto out; } skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, derive_crypt_complete, &ecr); res = crypto_skcipher_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); skcipher_request_set_crypt(req, &src_sg, &dst_sg, EXT4_AES_256_XTS_KEY_SIZE, NULL); res = crypto_skcipher_encrypt(req); if (res == -EINPROGRESS || res == -EBUSY) { wait_for_completion(&ecr.completion); res = ecr.res; } out: skcipher_request_free(req); crypto_free_skcipher(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_skcipher(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_skcipher *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; if (keyring_key->type != &key_type_logon) { printk_once(KERN_WARNING "ext4: key type must be logon\n"); res = -ENOKEY; goto out; } down_read(&keyring_key->sem); ukp = user_key_payload(keyring_key); if (ukp->datalen != sizeof(struct ext4_encryption_key)) { res = -EINVAL; up_read(&keyring_key->sem); goto out; } master_key = (struct ext4_encryption_key *)ukp->data; BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE != EXT4_KEY_DERIVATION_NONCE_SIZE); if (master_key->size != EXT4_AES_256_XTS_KEY_SIZE) { printk_once(KERN_WARNING "ext4: key size incorrect: %d\n", master_key->size); res = -ENOKEY; up_read(&keyring_key->sem); goto out; } res = ext4_derive_key_aes(ctx.nonce, master_key->raw, raw_key); up_read(&keyring_key->sem); if (res) goto out; got_key: ctfm = crypto_alloc_skcipher(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_skcipher_clear_flags(ctfm, ~0); crypto_tfm_set_flags(crypto_skcipher_tfm(ctfm), CRYPTO_TFM_REQ_WEAK_KEY); res = crypto_skcipher_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); }