From: Eric Biggers <ebiggers@xxxxxxxxxx> In preparation for introducing v2 encryption policies which will find and derive encryption keys differently from the current v1 encryption policies, refactor the v1 policy-specific key setup code from keyinfo.c into keysetup_legacy.c. Then rename keyinfo.c to keysetup.c. Note: the code moved into keysetup_legacy.c includes the table of master keys referenced by v1 DIRECT_KEY policies. I've chosen to keep this table as-is rather than trying to replace it with using the filesystem-level keyring, since the latter would add more complexity than it would save especially given the requirement to continue to support the keys actually being provided in a process-subscribed keyring. However, to distinguish the structures in this table from the structures that will go in the filesystem-level keyring, I renamed them from 'struct fscrypt_master_key' to 'struct fscrypt_direct_key'. Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> --- fs/crypto/Makefile | 8 +- fs/crypto/fscrypt_private.h | 37 ++- fs/crypto/keyinfo.c | 595 ------------------------------------ fs/crypto/keysetup.c | 309 +++++++++++++++++++ fs/crypto/keysetup_legacy.c | 338 ++++++++++++++++++++ include/linux/fscrypt.h | 4 +- 6 files changed, 685 insertions(+), 606 deletions(-) delete mode 100644 fs/crypto/keyinfo.c create mode 100644 fs/crypto/keysetup.c create mode 100644 fs/crypto/keysetup_legacy.c diff --git a/fs/crypto/Makefile b/fs/crypto/Makefile index cb496989a6b6..75c0c29fcc62 100644 --- a/fs/crypto/Makefile +++ b/fs/crypto/Makefile @@ -1,4 +1,10 @@ obj-$(CONFIG_FS_ENCRYPTION) += fscrypto.o -fscrypto-y := crypto.o fname.o hooks.o keyinfo.o policy.o +fscrypto-y := crypto.o \ + fname.o \ + hooks.o \ + keysetup.o \ + keysetup_legacy.o \ + policy.o + fscrypto-$(CONFIG_BLOCK) += bio.o diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index ac24edfc297f..c5a8181fc26c 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -4,9 +4,8 @@ * * Copyright (C) 2015, Google, Inc. * - * This contains encryption key functions. - * - * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015. + * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar. + * Heavily modified since then. */ #ifndef _FSCRYPT_PRIVATE_H @@ -77,11 +76,10 @@ struct fscrypt_info { struct inode *ci_inode; /* - * If non-NULL, then this inode uses a master key directly rather than a - * derived key, and ci_ctfm will equal ci_master_key->mk_ctfm. - * Otherwise, this inode uses a derived key. + * If non-NULL, then encryption is done using the master key directly + * and ci_ctfm will equal ci_direct_key->dk_ctfm. */ - struct fscrypt_master_key *ci_master_key; + struct fscrypt_direct_key *ci_direct_key; /* fields from the fscrypt_context */ u8 ci_data_mode; @@ -161,7 +159,7 @@ extern bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len, u32 max_len, u32 *encrypted_len_ret); -/* keyinfo.c */ +/* keysetup.c */ struct fscrypt_mode { const char *friendly_name; @@ -172,6 +170,29 @@ struct fscrypt_mode { bool needs_essiv; }; +static inline bool +fscrypt_mode_supports_direct_key(const struct fscrypt_mode *mode) +{ + return mode->ivsize >= offsetofend(union fscrypt_iv, nonce); +} + +extern struct crypto_skcipher * +fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key, + const struct inode *inode); + +extern int fscrypt_set_derived_key(struct fscrypt_info *ci, + const u8 *derived_key); + extern void __exit fscrypt_essiv_cleanup(void); +/* keysetup_legacy.c */ + +extern void fscrypt_put_direct_key(struct fscrypt_direct_key *dk); + +extern int fscrypt_setup_v1_file_key(struct fscrypt_info *ci, + const u8 *raw_master_key); + +extern int fscrypt_setup_v1_file_key_via_subscribed_keyrings( + struct fscrypt_info *ci); + #endif /* _FSCRYPT_PRIVATE_H */ diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c deleted file mode 100644 index 6c1e675d4eef..000000000000 --- a/fs/crypto/keyinfo.c +++ /dev/null @@ -1,595 +0,0 @@ -// SPDX-License-Identifier: GPL-2.0 -/* - * key management facility for FS encryption support. - * - * Copyright (C) 2015, Google, Inc. - * - * This contains encryption key functions. - * - * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015. - */ - -#include <keys/user-type.h> -#include <linux/hashtable.h> -#include <linux/scatterlist.h> -#include <linux/ratelimit.h> -#include <crypto/aes.h> -#include <crypto/algapi.h> -#include <crypto/sha.h> -#include <crypto/skcipher.h> -#include "fscrypt_private.h" - -static struct crypto_shash *essiv_hash_tfm; - -/* Table of keys referenced by DIRECT_KEY policies */ -static DEFINE_HASHTABLE(fscrypt_master_keys, 6); /* 6 bits = 64 buckets */ -static DEFINE_SPINLOCK(fscrypt_master_keys_lock); - -/* - * Key derivation function. This generates the derived key by encrypting the - * master key with AES-128-ECB using the inode's nonce as the AES key. - * - * The master key must be at least as long as the derived key. If the master - * key is longer, then only the first 'derived_keysize' bytes are used. - */ -static int derive_key_aes(const u8 *master_key, - const struct fscrypt_context *ctx, - u8 *derived_key, unsigned int derived_keysize) -{ - int res = 0; - struct skcipher_request *req = NULL; - DECLARE_CRYPTO_WAIT(wait); - 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, - crypto_req_done, &wait); - res = crypto_skcipher_setkey(tfm, ctx->nonce, sizeof(ctx->nonce)); - if (res < 0) - goto out; - - sg_init_one(&src_sg, master_key, derived_keysize); - sg_init_one(&dst_sg, derived_key, derived_keysize); - skcipher_request_set_crypt(req, &src_sg, &dst_sg, derived_keysize, - NULL); - res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait); -out: - skcipher_request_free(req); - crypto_free_skcipher(tfm); - return res; -} - -/* - * Search the current task's subscribed keyrings for a "logon" key with - * description prefix:descriptor, and if found acquire a read lock on it and - * return a pointer to its validated payload in *payload_ret. - */ -static struct key * -find_and_lock_process_key(const char *prefix, - const u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE], - unsigned int min_keysize, - const struct fscrypt_key **payload_ret) -{ - char *description; - struct key *key; - const struct user_key_payload *ukp; - const struct fscrypt_key *payload; - - description = kasprintf(GFP_NOFS, "%s%*phN", prefix, - FSCRYPT_KEY_DESCRIPTOR_SIZE, descriptor); - if (!description) - return ERR_PTR(-ENOMEM); - - key = request_key(&key_type_logon, description, NULL); - kfree(description); - if (IS_ERR(key)) - return key; - - down_read(&key->sem); - ukp = user_key_payload_locked(key); - - if (!ukp) /* was the key revoked before we acquired its semaphore? */ - goto invalid; - - payload = (const struct fscrypt_key *)ukp->data; - - if (ukp->datalen != sizeof(struct fscrypt_key) || - payload->size < 1 || payload->size > FSCRYPT_MAX_KEY_SIZE) { - fscrypt_warn(NULL, - "key with description '%s' has invalid payload", - key->description); - goto invalid; - } - - if (payload->size < min_keysize) { - fscrypt_warn(NULL, - "key with description '%s' is too short (got %u bytes, need %u+ bytes)", - key->description, payload->size, min_keysize); - goto invalid; - } - - *payload_ret = payload; - return key; - -invalid: - up_read(&key->sem); - key_put(key); - return ERR_PTR(-ENOKEY); -} - -static struct fscrypt_mode available_modes[] = { - [FSCRYPT_MODE_AES_256_XTS] = { - .friendly_name = "AES-256-XTS", - .cipher_str = "xts(aes)", - .keysize = 64, - .ivsize = 16, - }, - [FSCRYPT_MODE_AES_256_CTS] = { - .friendly_name = "AES-256-CTS-CBC", - .cipher_str = "cts(cbc(aes))", - .keysize = 32, - .ivsize = 16, - }, - [FSCRYPT_MODE_AES_128_CBC] = { - .friendly_name = "AES-128-CBC", - .cipher_str = "cbc(aes)", - .keysize = 16, - .ivsize = 16, - .needs_essiv = true, - }, - [FSCRYPT_MODE_AES_128_CTS] = { - .friendly_name = "AES-128-CTS-CBC", - .cipher_str = "cts(cbc(aes))", - .keysize = 16, - .ivsize = 16, - }, - [FSCRYPT_MODE_ADIANTUM] = { - .friendly_name = "Adiantum", - .cipher_str = "adiantum(xchacha12,aes)", - .keysize = 32, - .ivsize = 32, - }, -}; - -static struct fscrypt_mode * -select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode) -{ - if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) { - fscrypt_warn(inode->i_sb, - "inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)", - inode->i_ino, ci->ci_data_mode, - ci->ci_filename_mode); - return ERR_PTR(-EINVAL); - } - - if (S_ISREG(inode->i_mode)) - return &available_modes[ci->ci_data_mode]; - - if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) - return &available_modes[ci->ci_filename_mode]; - - WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n", - inode->i_ino, (inode->i_mode & S_IFMT)); - return ERR_PTR(-EINVAL); -} - -/* Find the master key, then derive the inode's actual encryption key */ -static int find_and_derive_key(const struct inode *inode, - const struct fscrypt_context *ctx, - u8 *derived_key, const struct fscrypt_mode *mode) -{ - struct key *key; - const struct fscrypt_key *payload; - int err; - - key = find_and_lock_process_key(FSCRYPT_KEY_DESC_PREFIX, - ctx->master_key_descriptor, - mode->keysize, &payload); - if (key == ERR_PTR(-ENOKEY) && inode->i_sb->s_cop->key_prefix) { - key = find_and_lock_process_key(inode->i_sb->s_cop->key_prefix, - ctx->master_key_descriptor, - mode->keysize, &payload); - } - if (IS_ERR(key)) - return PTR_ERR(key); - - if (ctx->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { - if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) { - fscrypt_warn(inode->i_sb, - "direct key mode not allowed with %s", - mode->friendly_name); - err = -EINVAL; - } else if (ctx->contents_encryption_mode != - ctx->filenames_encryption_mode) { - fscrypt_warn(inode->i_sb, - "direct key mode not allowed with different contents and filenames modes"); - err = -EINVAL; - } else { - memcpy(derived_key, payload->raw, mode->keysize); - err = 0; - } - } else { - err = derive_key_aes(payload->raw, ctx, derived_key, - mode->keysize); - } - up_read(&key->sem); - key_put(key); - return err; -} - -/* Allocate and key a symmetric cipher object for the given encryption mode */ -static struct crypto_skcipher * -allocate_skcipher_for_mode(struct fscrypt_mode *mode, const u8 *raw_key, - const struct inode *inode) -{ - struct crypto_skcipher *tfm; - int err; - - tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0); - if (IS_ERR(tfm)) { - fscrypt_warn(inode->i_sb, - "error allocating '%s' transform for inode %lu: %ld", - mode->cipher_str, inode->i_ino, PTR_ERR(tfm)); - return tfm; - } - if (unlikely(!mode->logged_impl_name)) { - /* - * fscrypt performance can vary greatly depending on which - * crypto algorithm implementation is used. Help people debug - * performance problems by logging the ->cra_driver_name the - * first time a mode is used. Note that multiple threads can - * race here, but it doesn't really matter. - */ - mode->logged_impl_name = true; - pr_info("fscrypt: %s using implementation \"%s\"\n", - mode->friendly_name, - crypto_skcipher_alg(tfm)->base.cra_driver_name); - } - crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY); - err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize); - if (err) - goto err_free_tfm; - - return tfm; - -err_free_tfm: - crypto_free_skcipher(tfm); - return ERR_PTR(err); -} - -/* Master key referenced by DIRECT_KEY policy */ -struct fscrypt_master_key { - struct hlist_node mk_node; - refcount_t mk_refcount; - const struct fscrypt_mode *mk_mode; - struct crypto_skcipher *mk_ctfm; - u8 mk_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; - u8 mk_raw[FSCRYPT_MAX_KEY_SIZE]; -}; - -static void free_master_key(struct fscrypt_master_key *mk) -{ - if (mk) { - crypto_free_skcipher(mk->mk_ctfm); - kzfree(mk); - } -} - -static void put_master_key(struct fscrypt_master_key *mk) -{ - if (!refcount_dec_and_lock(&mk->mk_refcount, &fscrypt_master_keys_lock)) - return; - hash_del(&mk->mk_node); - spin_unlock(&fscrypt_master_keys_lock); - - free_master_key(mk); -} - -/* - * Find/insert the given master key into the fscrypt_master_keys table. If - * found, it is returned with elevated refcount, and 'to_insert' is freed if - * non-NULL. If not found, 'to_insert' is inserted and returned if it's - * non-NULL; otherwise NULL is returned. - */ -static struct fscrypt_master_key * -find_or_insert_master_key(struct fscrypt_master_key *to_insert, - const u8 *raw_key, const struct fscrypt_mode *mode, - const struct fscrypt_info *ci) -{ - unsigned long hash_key; - struct fscrypt_master_key *mk; - - /* - * Careful: to avoid potentially leaking secret key bytes via timing - * information, we must key the hash table by descriptor rather than by - * raw key, and use crypto_memneq() when comparing raw keys. - */ - - BUILD_BUG_ON(sizeof(hash_key) > FSCRYPT_KEY_DESCRIPTOR_SIZE); - memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key)); - - spin_lock(&fscrypt_master_keys_lock); - hash_for_each_possible(fscrypt_master_keys, mk, mk_node, hash_key) { - if (memcmp(ci->ci_master_key_descriptor, mk->mk_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0) - continue; - if (mode != mk->mk_mode) - continue; - if (crypto_memneq(raw_key, mk->mk_raw, mode->keysize)) - continue; - /* using existing tfm with same (descriptor, mode, raw_key) */ - refcount_inc(&mk->mk_refcount); - spin_unlock(&fscrypt_master_keys_lock); - free_master_key(to_insert); - return mk; - } - if (to_insert) - hash_add(fscrypt_master_keys, &to_insert->mk_node, hash_key); - spin_unlock(&fscrypt_master_keys_lock); - return to_insert; -} - -/* Prepare to encrypt directly using the master key in the given mode */ -static struct fscrypt_master_key * -fscrypt_get_master_key(const struct fscrypt_info *ci, struct fscrypt_mode *mode, - const u8 *raw_key, const struct inode *inode) -{ - struct fscrypt_master_key *mk; - int err; - - /* Is there already a tfm for this key? */ - mk = find_or_insert_master_key(NULL, raw_key, mode, ci); - if (mk) - return mk; - - /* Nope, allocate one. */ - mk = kzalloc(sizeof(*mk), GFP_NOFS); - if (!mk) - return ERR_PTR(-ENOMEM); - refcount_set(&mk->mk_refcount, 1); - mk->mk_mode = mode; - mk->mk_ctfm = allocate_skcipher_for_mode(mode, raw_key, inode); - if (IS_ERR(mk->mk_ctfm)) { - err = PTR_ERR(mk->mk_ctfm); - mk->mk_ctfm = NULL; - goto err_free_mk; - } - memcpy(mk->mk_descriptor, ci->ci_master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE); - memcpy(mk->mk_raw, raw_key, mode->keysize); - - return find_or_insert_master_key(mk, raw_key, mode, ci); - -err_free_mk: - free_master_key(mk); - return ERR_PTR(err); -} - -static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt) -{ - struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm); - - /* init hash transform on demand */ - if (unlikely(!tfm)) { - struct crypto_shash *prev_tfm; - - tfm = crypto_alloc_shash("sha256", 0, 0); - if (IS_ERR(tfm)) { - fscrypt_warn(NULL, - "error allocating SHA-256 transform: %ld", - PTR_ERR(tfm)); - return PTR_ERR(tfm); - } - prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm); - if (prev_tfm) { - crypto_free_shash(tfm); - tfm = prev_tfm; - } - } - - { - SHASH_DESC_ON_STACK(desc, tfm); - desc->tfm = tfm; - desc->flags = 0; - - return crypto_shash_digest(desc, key, keysize, salt); - } -} - -static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key, - int keysize) -{ - int err; - struct crypto_cipher *essiv_tfm; - u8 salt[SHA256_DIGEST_SIZE]; - - essiv_tfm = crypto_alloc_cipher("aes", 0, 0); - if (IS_ERR(essiv_tfm)) - return PTR_ERR(essiv_tfm); - - ci->ci_essiv_tfm = essiv_tfm; - - err = derive_essiv_salt(raw_key, keysize, salt); - if (err) - goto out; - - /* - * Using SHA256 to derive the salt/key will result in AES-256 being - * used for IV generation. File contents encryption will still use the - * configured keysize (AES-128) nevertheless. - */ - err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt)); - if (err) - goto out; - -out: - memzero_explicit(salt, sizeof(salt)); - return err; -} - -void __exit fscrypt_essiv_cleanup(void) -{ - crypto_free_shash(essiv_hash_tfm); -} - -/* - * Given the encryption mode and key (normally the derived key, but for - * DIRECT_KEY mode it's the master key), set up the inode's symmetric cipher - * transform object(s). - */ -static int setup_crypto_transform(struct fscrypt_info *ci, - struct fscrypt_mode *mode, - const u8 *raw_key, const struct inode *inode) -{ - struct fscrypt_master_key *mk; - struct crypto_skcipher *ctfm; - int err; - - if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { - mk = fscrypt_get_master_key(ci, mode, raw_key, inode); - if (IS_ERR(mk)) - return PTR_ERR(mk); - ctfm = mk->mk_ctfm; - } else { - mk = NULL; - ctfm = allocate_skcipher_for_mode(mode, raw_key, inode); - if (IS_ERR(ctfm)) - return PTR_ERR(ctfm); - } - ci->ci_master_key = mk; - ci->ci_ctfm = ctfm; - - if (mode->needs_essiv) { - /* ESSIV implies 16-byte IVs which implies !DIRECT_KEY */ - WARN_ON(mode->ivsize != AES_BLOCK_SIZE); - WARN_ON(ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY); - - err = init_essiv_generator(ci, raw_key, mode->keysize); - if (err) { - fscrypt_warn(inode->i_sb, - "error initializing ESSIV generator for inode %lu: %d", - inode->i_ino, err); - return err; - } - } - return 0; -} - -static void put_crypt_info(struct fscrypt_info *ci) -{ - if (!ci) - return; - - if (ci->ci_master_key) { - put_master_key(ci->ci_master_key); - } else { - crypto_free_skcipher(ci->ci_ctfm); - crypto_free_cipher(ci->ci_essiv_tfm); - } - kmem_cache_free(fscrypt_info_cachep, ci); -} - -int fscrypt_get_encryption_info(struct inode *inode) -{ - struct fscrypt_info *crypt_info; - struct fscrypt_context ctx; - struct fscrypt_mode *mode; - u8 *raw_key = NULL; - int res; - - if (inode->i_crypt_info) - return 0; - - res = fscrypt_initialize(inode->i_sb->s_cop->flags); - if (res) - return res; - - res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); - if (res < 0) { - if (!fscrypt_dummy_context_enabled(inode) || - IS_ENCRYPTED(inode)) - return res; - /* Fake up a context for an unencrypted directory */ - memset(&ctx, 0, sizeof(ctx)); - ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; - ctx.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS; - ctx.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS; - memset(ctx.master_key_descriptor, 0x42, - FSCRYPT_KEY_DESCRIPTOR_SIZE); - } else if (res != sizeof(ctx)) { - return -EINVAL; - } - - if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) - return -EINVAL; - - if (ctx.flags & ~FSCRYPT_POLICY_FLAGS_VALID) - return -EINVAL; - - crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS); - if (!crypt_info) - return -ENOMEM; - - crypt_info->ci_inode = inode; - - crypt_info->ci_flags = ctx.flags; - crypt_info->ci_data_mode = ctx.contents_encryption_mode; - crypt_info->ci_filename_mode = ctx.filenames_encryption_mode; - memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE); - memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); - - mode = select_encryption_mode(crypt_info, inode); - if (IS_ERR(mode)) { - res = PTR_ERR(mode); - goto out; - } - WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE); - crypt_info->ci_mode = mode; - - /* - * This cannot be a stack buffer because it may be passed to the - * scatterlist crypto API as part of key derivation. - */ - res = -ENOMEM; - raw_key = kmalloc(mode->keysize, GFP_NOFS); - if (!raw_key) - goto out; - - res = find_and_derive_key(inode, &ctx, raw_key, mode); - if (res) - goto out; - - res = setup_crypto_transform(crypt_info, mode, raw_key, inode); - if (res) - goto out; - - if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL) - crypt_info = NULL; -out: - if (res == -ENOKEY) - res = 0; - put_crypt_info(crypt_info); - kzfree(raw_key); - return res; -} -EXPORT_SYMBOL(fscrypt_get_encryption_info); - -void fscrypt_put_encryption_info(struct inode *inode) -{ - put_crypt_info(inode->i_crypt_info); - inode->i_crypt_info = NULL; -} -EXPORT_SYMBOL(fscrypt_put_encryption_info); diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c new file mode 100644 index 000000000000..898a82d5ff3c --- /dev/null +++ b/fs/crypto/keysetup.c @@ -0,0 +1,309 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Key setup facility for FS encryption support. + * + * Copyright (C) 2015, Google, Inc. + * + * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar. + * Heavily modified since then. + */ + +#include <crypto/aes.h> +#include <crypto/sha.h> +#include <crypto/skcipher.h> +#include <linux/key.h> + +#include "fscrypt_private.h" + +static struct crypto_shash *essiv_hash_tfm; + +static struct fscrypt_mode available_modes[] = { + [FSCRYPT_MODE_AES_256_XTS] = { + .friendly_name = "AES-256-XTS", + .cipher_str = "xts(aes)", + .keysize = 64, + .ivsize = 16, + }, + [FSCRYPT_MODE_AES_256_CTS] = { + .friendly_name = "AES-256-CTS-CBC", + .cipher_str = "cts(cbc(aes))", + .keysize = 32, + .ivsize = 16, + }, + [FSCRYPT_MODE_AES_128_CBC] = { + .friendly_name = "AES-128-CBC", + .cipher_str = "cbc(aes)", + .keysize = 16, + .ivsize = 16, + .needs_essiv = true, + }, + [FSCRYPT_MODE_AES_128_CTS] = { + .friendly_name = "AES-128-CTS-CBC", + .cipher_str = "cts(cbc(aes))", + .keysize = 16, + .ivsize = 16, + }, + [FSCRYPT_MODE_ADIANTUM] = { + .friendly_name = "Adiantum", + .cipher_str = "adiantum(xchacha12,aes)", + .keysize = 32, + .ivsize = 32, + }, +}; + +static struct fscrypt_mode * +select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode) +{ + if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) { + fscrypt_warn(inode->i_sb, + "inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)", + inode->i_ino, ci->ci_data_mode, + ci->ci_filename_mode); + return ERR_PTR(-EINVAL); + } + + if (S_ISREG(inode->i_mode)) + return &available_modes[ci->ci_data_mode]; + + if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) + return &available_modes[ci->ci_filename_mode]; + + WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n", + inode->i_ino, (inode->i_mode & S_IFMT)); + return ERR_PTR(-EINVAL); +} + +/* Create a symmetric cipher object for the given encryption mode and key */ +struct crypto_skcipher *fscrypt_allocate_skcipher(struct fscrypt_mode *mode, + const u8 *raw_key, + const struct inode *inode) +{ + struct crypto_skcipher *tfm; + int err; + + tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0); + if (IS_ERR(tfm)) { + fscrypt_warn(inode->i_sb, + "error allocating '%s' transform for inode %lu: %ld", + mode->cipher_str, inode->i_ino, PTR_ERR(tfm)); + return tfm; + } + if (unlikely(!mode->logged_impl_name)) { + /* + * fscrypt performance can vary greatly depending on which + * crypto algorithm implementation is used. Help people debug + * performance problems by logging the ->cra_driver_name the + * first time a mode is used. Note that multiple threads can + * race here, but it doesn't really matter. + */ + mode->logged_impl_name = true; + pr_info("fscrypt: %s using implementation \"%s\"\n", + mode->friendly_name, + crypto_skcipher_alg(tfm)->base.cra_driver_name); + } + crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY); + err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize); + if (err) + goto err_free_tfm; + + return tfm; + +err_free_tfm: + crypto_free_skcipher(tfm); + return ERR_PTR(err); +} + +static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt) +{ + struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm); + + /* init hash transform on demand */ + if (unlikely(!tfm)) { + struct crypto_shash *prev_tfm; + + tfm = crypto_alloc_shash("sha256", 0, 0); + if (IS_ERR(tfm)) { + fscrypt_warn(NULL, + "error allocating SHA-256 transform: %ld", + PTR_ERR(tfm)); + return PTR_ERR(tfm); + } + prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm); + if (prev_tfm) { + crypto_free_shash(tfm); + tfm = prev_tfm; + } + } + + { + SHASH_DESC_ON_STACK(desc, tfm); + desc->tfm = tfm; + desc->flags = 0; + + return crypto_shash_digest(desc, key, keysize, salt); + } +} + +static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key, + int keysize) +{ + int err; + struct crypto_cipher *essiv_tfm; + u8 salt[SHA256_DIGEST_SIZE]; + + if (WARN_ON(ci->ci_mode->ivsize != AES_BLOCK_SIZE)) + return -EINVAL; + + essiv_tfm = crypto_alloc_cipher("aes", 0, 0); + if (IS_ERR(essiv_tfm)) + return PTR_ERR(essiv_tfm); + + ci->ci_essiv_tfm = essiv_tfm; + + err = derive_essiv_salt(raw_key, keysize, salt); + if (err) + goto out; + + /* + * Using SHA256 to derive the salt/key will result in AES-256 being + * used for IV generation. File contents encryption will still use the + * configured keysize (AES-128) nevertheless. + */ + err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt)); + if (err) + goto out; + +out: + memzero_explicit(salt, sizeof(salt)); + return err; +} + +void __exit fscrypt_essiv_cleanup(void) +{ + crypto_free_shash(essiv_hash_tfm); +} + +/* Given the per-file key, set up the file's crypto transform object(s) */ +int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key) +{ + struct fscrypt_mode *mode = ci->ci_mode; + struct crypto_skcipher *ctfm; + int err; + + ctfm = fscrypt_allocate_skcipher(mode, derived_key, ci->ci_inode); + if (IS_ERR(ctfm)) + return PTR_ERR(ctfm); + + ci->ci_ctfm = ctfm; + + if (mode->needs_essiv) { + err = init_essiv_generator(ci, derived_key, mode->keysize); + if (err) { + fscrypt_warn(ci->ci_inode->i_sb, + "error initializing ESSIV generator for inode %lu: %d", + ci->ci_inode->i_ino, err); + return err; + } + } + return 0; +} + +/* + * Find the master key, then set up the inode's actual encryption key. + */ +static int setup_file_encryption_key(struct fscrypt_info *ci) +{ + return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); +} + +static void put_crypt_info(struct fscrypt_info *ci) +{ + if (!ci) + return; + + if (ci->ci_direct_key) { + fscrypt_put_direct_key(ci->ci_direct_key); + } else { + crypto_free_skcipher(ci->ci_ctfm); + crypto_free_cipher(ci->ci_essiv_tfm); + } + kmem_cache_free(fscrypt_info_cachep, ci); +} + +int fscrypt_get_encryption_info(struct inode *inode) +{ + struct fscrypt_info *crypt_info; + struct fscrypt_context ctx; + struct fscrypt_mode *mode; + int res; + + if (inode->i_crypt_info) + return 0; + + res = fscrypt_initialize(inode->i_sb->s_cop->flags); + if (res) + return res; + + res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); + if (res < 0) { + if (!fscrypt_dummy_context_enabled(inode) || + IS_ENCRYPTED(inode)) + return res; + /* Fake up a context for an unencrypted directory */ + memset(&ctx, 0, sizeof(ctx)); + ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; + ctx.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS; + ctx.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS; + memset(ctx.master_key_descriptor, 0x42, + FSCRYPT_KEY_DESCRIPTOR_SIZE); + } else if (res != sizeof(ctx)) { + return -EINVAL; + } + + if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) + return -EINVAL; + + if (ctx.flags & ~FSCRYPT_POLICY_FLAGS_VALID) + return -EINVAL; + + crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS); + if (!crypt_info) + return -ENOMEM; + + crypt_info->ci_inode = inode; + + crypt_info->ci_flags = ctx.flags; + crypt_info->ci_data_mode = ctx.contents_encryption_mode; + crypt_info->ci_filename_mode = ctx.filenames_encryption_mode; + memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor, + FSCRYPT_KEY_DESCRIPTOR_SIZE); + memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); + + mode = select_encryption_mode(crypt_info, inode); + if (IS_ERR(mode)) { + res = PTR_ERR(mode); + goto out; + } + WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE); + crypt_info->ci_mode = mode; + + res = setup_file_encryption_key(crypt_info); + if (res) + goto out; + + if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL) + crypt_info = NULL; +out: + if (res == -ENOKEY) + res = 0; + put_crypt_info(crypt_info); + return res; +} +EXPORT_SYMBOL(fscrypt_get_encryption_info); + +void fscrypt_put_encryption_info(struct inode *inode) +{ + put_crypt_info(inode->i_crypt_info); + inode->i_crypt_info = NULL; +} +EXPORT_SYMBOL(fscrypt_put_encryption_info); diff --git a/fs/crypto/keysetup_legacy.c b/fs/crypto/keysetup_legacy.c new file mode 100644 index 000000000000..585d7e31e8f4 --- /dev/null +++ b/fs/crypto/keysetup_legacy.c @@ -0,0 +1,338 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Key setup for v1 encryption policies + * + * Copyright 2015, 2019 Google LLC + */ + +/* + * This file implements compatibility functions for the original encryption + * policy version ("v1"), including: + * + * - Deriving per-file keys using the AES-128-ECB based KDF + * (rather than the new method of using HKDF-SHA512) + * + * - Retrieving fscrypt master keys from process-subscribed keyrings + * (rather than the new method of using a filesystem-level keyring) + * + * - Handling policies with the DIRECT_KEY flag set using a master key table + * (rather than the new method of implementing DIRECT_KEY with per-mode keys + * managed alongside the master keys in the filesystem-level keyring) + */ + +#include <crypto/algapi.h> +#include <crypto/skcipher.h> +#include <keys/user-type.h> +#include <linux/hashtable.h> +#include <linux/scatterlist.h> + +#include "fscrypt_private.h" + +/* Table of keys referenced by DIRECT_KEY policies */ +static DEFINE_HASHTABLE(fscrypt_direct_keys, 6); /* 6 bits = 64 buckets */ +static DEFINE_SPINLOCK(fscrypt_direct_keys_lock); + +/* + * Legacy key derivation function. This generates the derived key by encrypting + * the master key with AES-128-ECB using the nonce as the AES key. This + * provides a unique derived key with sufficient entropy for each inode. + * However, it's nonstandard, non-extensible, doesn't evenly distribute the + * entropy from the master key, and is trivially reversible: an attacker who + * compromises a derived key can "decrypt" it to get back to the master key, + * then derive any other key. For all new code, use HKDF instead. + * + * The master key must be at least as long as the derived key. If the master + * key is longer, then only the first 'derived_keysize' bytes are used. + */ +static int derive_key_aes(const u8 *master_key, + const u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE], + u8 *derived_key, unsigned int derived_keysize) +{ + int res = 0; + struct skcipher_request *req = NULL; + DECLARE_CRYPTO_WAIT(wait); + 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, + crypto_req_done, &wait); + res = crypto_skcipher_setkey(tfm, nonce, FS_KEY_DERIVATION_NONCE_SIZE); + if (res < 0) + goto out; + + sg_init_one(&src_sg, master_key, derived_keysize); + sg_init_one(&dst_sg, derived_key, derived_keysize); + skcipher_request_set_crypt(req, &src_sg, &dst_sg, derived_keysize, + NULL); + res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait); +out: + skcipher_request_free(req); + crypto_free_skcipher(tfm); + return res; +} + +/* + * Search the current task's subscribed keyrings for a "logon" key with + * description prefix:descriptor, and if found acquire a read lock on it and + * return a pointer to its validated payload in *payload_ret. + */ +static struct key * +find_and_lock_process_key(const char *prefix, + const u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE], + unsigned int min_keysize, + const struct fscrypt_key **payload_ret) +{ + char *description; + struct key *key; + const struct user_key_payload *ukp; + const struct fscrypt_key *payload; + + description = kasprintf(GFP_NOFS, "%s%*phN", prefix, + FSCRYPT_KEY_DESCRIPTOR_SIZE, descriptor); + if (!description) + return ERR_PTR(-ENOMEM); + + key = request_key(&key_type_logon, description, NULL); + kfree(description); + if (IS_ERR(key)) + return key; + + down_read(&key->sem); + ukp = user_key_payload_locked(key); + + if (!ukp) /* was the key revoked before we acquired its semaphore? */ + goto invalid; + + payload = (const struct fscrypt_key *)ukp->data; + + if (ukp->datalen != sizeof(struct fscrypt_key) || + payload->size < 1 || payload->size > FSCRYPT_MAX_KEY_SIZE) { + fscrypt_warn(NULL, + "key with description '%s' has invalid payload", + key->description); + goto invalid; + } + + if (payload->size < min_keysize) { + fscrypt_warn(NULL, + "key with description '%s' is too short (got %u bytes, need %u+ bytes)", + key->description, payload->size, min_keysize); + goto invalid; + } + + *payload_ret = payload; + return key; + +invalid: + up_read(&key->sem); + key_put(key); + return ERR_PTR(-ENOKEY); +} + +/* Master key referenced by DIRECT_KEY policy */ +struct fscrypt_direct_key { + struct hlist_node dk_node; + refcount_t dk_refcount; + const struct fscrypt_mode *dk_mode; + struct crypto_skcipher *dk_ctfm; + u8 dk_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; + u8 dk_raw[FSCRYPT_MAX_KEY_SIZE]; +}; + +static void free_direct_key(struct fscrypt_direct_key *dk) +{ + if (dk) { + crypto_free_skcipher(dk->dk_ctfm); + kzfree(dk); + } +} + +void fscrypt_put_direct_key(struct fscrypt_direct_key *dk) +{ + if (!refcount_dec_and_lock(&dk->dk_refcount, &fscrypt_direct_keys_lock)) + return; + hash_del(&dk->dk_node); + spin_unlock(&fscrypt_direct_keys_lock); + + free_direct_key(dk); +} + +/* + * Find/insert the given key into the fscrypt_direct_keys table. If found, it + * is returned with elevated refcount, and 'to_insert' is freed if non-NULL. If + * not found, 'to_insert' is inserted and returned if it's non-NULL; otherwise + * NULL is returned. + */ +static struct fscrypt_direct_key * +find_or_insert_direct_key(struct fscrypt_direct_key *to_insert, + const u8 *raw_key, const struct fscrypt_info *ci) +{ + unsigned long hash_key; + struct fscrypt_direct_key *dk; + + /* + * Careful: to avoid potentially leaking secret key bytes via timing + * information, we must key the hash table by descriptor rather than by + * raw key, and use crypto_memneq() when comparing raw keys. + */ + + BUILD_BUG_ON(sizeof(hash_key) > FSCRYPT_KEY_DESCRIPTOR_SIZE); + memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key)); + + spin_lock(&fscrypt_direct_keys_lock); + hash_for_each_possible(fscrypt_direct_keys, dk, dk_node, hash_key) { + if (memcmp(ci->ci_master_key_descriptor, dk->dk_descriptor, + FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0) + continue; + if (ci->ci_mode != dk->dk_mode) + continue; + if (crypto_memneq(raw_key, dk->dk_raw, ci->ci_mode->keysize)) + continue; + /* using existing tfm with same (descriptor, mode, raw_key) */ + refcount_inc(&dk->dk_refcount); + spin_unlock(&fscrypt_direct_keys_lock); + free_direct_key(to_insert); + return dk; + } + if (to_insert) + hash_add(fscrypt_direct_keys, &to_insert->dk_node, hash_key); + spin_unlock(&fscrypt_direct_keys_lock); + return to_insert; +} + +/* Prepare to encrypt directly using the master key in the given mode */ +static struct fscrypt_direct_key * +fscrypt_get_direct_key(const struct fscrypt_info *ci, const u8 *raw_key) +{ + struct fscrypt_direct_key *dk; + int err; + + /* Is there already a tfm for this key? */ + dk = find_or_insert_direct_key(NULL, raw_key, ci); + if (dk) + return dk; + + /* Nope, allocate one. */ + dk = kzalloc(sizeof(*dk), GFP_NOFS); + if (!dk) + return ERR_PTR(-ENOMEM); + refcount_set(&dk->dk_refcount, 1); + dk->dk_mode = ci->ci_mode; + dk->dk_ctfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key, + ci->ci_inode); + if (IS_ERR(dk->dk_ctfm)) { + err = PTR_ERR(dk->dk_ctfm); + dk->dk_ctfm = NULL; + goto err_free_dk; + } + memcpy(dk->dk_descriptor, ci->ci_master_key_descriptor, + FSCRYPT_KEY_DESCRIPTOR_SIZE); + memcpy(dk->dk_raw, raw_key, ci->ci_mode->keysize); + + return find_or_insert_direct_key(dk, raw_key, ci); + +err_free_dk: + free_direct_key(dk); + return ERR_PTR(err); +} + +/* v1 policy, DIRECT_KEY: use the master key directly */ +static int setup_v1_file_key_direct(struct fscrypt_info *ci, + const u8 *raw_master_key) +{ + const struct fscrypt_mode *mode = ci->ci_mode; + struct fscrypt_direct_key *dk; + + if (!fscrypt_mode_supports_direct_key(mode)) { + fscrypt_warn(ci->ci_inode->i_sb, + "direct key flag not allowed with %s", + mode->friendly_name); + return -EINVAL; + } + + if (ci->ci_data_mode != ci->ci_filename_mode) { + fscrypt_warn(ci->ci_inode->i_sb, + "direct key flag not allowed with different contents and filenames modes"); + return -EINVAL; + } + + /* ESSIV implies 16-byte IVs which implies !DIRECT_KEY */ + if (WARN_ON(mode->needs_essiv)) + return -EINVAL; + + dk = fscrypt_get_direct_key(ci, raw_master_key); + if (IS_ERR(dk)) + return PTR_ERR(dk); + ci->ci_direct_key = dk; + ci->ci_ctfm = dk->dk_ctfm; + return 0; +} + +/* v1 policy, !DIRECT_KEY: derive the file's encryption key */ +static int setup_v1_file_key_derived(struct fscrypt_info *ci, + const u8 *raw_master_key) +{ + u8 *derived_key; + int err; + + /* + * This cannot be a stack buffer because it will be passed to the + * scatterlist crypto API during derive_key_aes(). + */ + derived_key = kmalloc(ci->ci_mode->keysize, GFP_NOFS); + if (!derived_key) + return -ENOMEM; + + err = derive_key_aes(raw_master_key, ci->ci_nonce, + derived_key, ci->ci_mode->keysize); + if (err) + goto out; + + err = fscrypt_set_derived_key(ci, derived_key); +out: + kzfree(derived_key); + return err; +} + +int fscrypt_setup_v1_file_key(struct fscrypt_info *ci, const u8 *raw_master_key) +{ + if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) + return setup_v1_file_key_direct(ci, raw_master_key); + else + return setup_v1_file_key_derived(ci, raw_master_key); +} + +int fscrypt_setup_v1_file_key_via_subscribed_keyrings(struct fscrypt_info *ci) +{ + struct key *key; + const struct fscrypt_key *payload; + int err; + + key = find_and_lock_process_key(FSCRYPT_KEY_DESC_PREFIX, + ci->ci_master_key_descriptor, + ci->ci_mode->keysize, &payload); + if (key == ERR_PTR(-ENOKEY) && ci->ci_inode->i_sb->s_cop->key_prefix) { + key = find_and_lock_process_key(ci->ci_inode->i_sb->s_cop->key_prefix, + ci->ci_master_key_descriptor, + ci->ci_mode->keysize, &payload); + } + if (IS_ERR(key)) + return PTR_ERR(key); + + err = fscrypt_setup_v1_file_key(ci, payload->raw); + up_read(&key->sem); + key_put(key); + return err; +} diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index 8b1e44421497..5afb9fc13ef4 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -112,7 +112,7 @@ extern int fscrypt_ioctl_get_policy(struct file *, void __user *); extern int fscrypt_has_permitted_context(struct inode *, struct inode *); extern int fscrypt_inherit_context(struct inode *, struct inode *, void *, bool); -/* keyinfo.c */ +/* keysetup.c */ extern int fscrypt_get_encryption_info(struct inode *); extern void fscrypt_put_encryption_info(struct inode *); @@ -312,7 +312,7 @@ static inline int fscrypt_inherit_context(struct inode *parent, return -EOPNOTSUPP; } -/* keyinfo.c */ +/* keysetup.c */ static inline int fscrypt_get_encryption_info(struct inode *inode) { return -EOPNOTSUPP; -- 2.20.1
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