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fscrypt: rename fscrypt_master_key to fscrypt_direct_key

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In preparation for introducing a filesystem-level keyring which will
contain fscrypt master keys, rename the existing 'struct
fscrypt_master_key' to 'struct fscrypt_direct_key'.  This is the
structure in the existing table of master keys that's maintained to
deduplicate the crypto transforms for v1 DIRECT_KEY policies.

I've chosen to keep this table as-is rather than make it automagically
add/remove the keys to/from the filesystem-level keyring, since that
would add a lot of extra complexity to the filesystem-level keyring.

Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers 2019-08-04 19:35:45 -07:00
parent 59dc6a8e1f
commit a828daabb2
2 changed files with 68 additions and 69 deletions
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7
fs/crypto/fscrypt_private.h
View File

@ -77,11 +77,10 @@ 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;

130
fs/crypto/keyinfo.c
View File

@ -21,8 +21,8 @@
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);
static DEFINE_HASHTABLE(fscrypt_direct_keys, 6); /* 6 bits = 64 buckets */
static DEFINE_SPINLOCK(fscrypt_direct_keys_lock);
/*
* Key derivation function. This generates the derived key by encrypting the
@ -273,46 +273,46 @@ err_free_tfm:
}
/* 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];
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_master_key(struct fscrypt_master_key *mk)
static void free_direct_key(struct fscrypt_direct_key *dk)
{
if (mk) {
crypto_free_skcipher(mk->mk_ctfm);
kzfree(mk);
if (dk) {
crypto_free_skcipher(dk->dk_ctfm);
kzfree(dk);
}
}
static void put_master_key(struct fscrypt_master_key *mk)
static void put_direct_key(struct fscrypt_direct_key *dk)
{
if (!refcount_dec_and_lock(&mk->mk_refcount, &fscrypt_master_keys_lock))
if (!refcount_dec_and_lock(&dk->dk_refcount, &fscrypt_direct_keys_lock))
return;
hash_del(&mk->mk_node);
spin_unlock(&fscrypt_master_keys_lock);
hash_del(&dk->dk_node);
spin_unlock(&fscrypt_direct_keys_lock);
free_master_key(mk);
free_direct_key(dk);
}
/*
* 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.
* 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_master_key *
find_or_insert_master_key(struct fscrypt_master_key *to_insert,
static struct fscrypt_direct_key *
find_or_insert_direct_key(struct fscrypt_direct_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;
struct fscrypt_direct_key *dk;
/*
* Careful: to avoid potentially leaking secret key bytes via timing
@ -323,60 +323,60 @@ find_or_insert_master_key(struct fscrypt_master_key *to_insert,
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,
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 (mode != mk->mk_mode)
if (mode != dk->dk_mode)
continue;
if (crypto_memneq(raw_key, mk->mk_raw, mode->keysize))
if (crypto_memneq(raw_key, dk->dk_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;
refcount_inc(&dk->dk_refcount);
spin_unlock(&fscrypt_direct_keys_lock);
free_direct_key(to_insert);
return dk;
}
if (to_insert)
hash_add(fscrypt_master_keys, &to_insert->mk_node, hash_key);
spin_unlock(&fscrypt_master_keys_lock);
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_master_key *
fscrypt_get_master_key(const struct fscrypt_info *ci, struct fscrypt_mode *mode,
static struct fscrypt_direct_key *
fscrypt_get_direct_key(const struct fscrypt_info *ci, struct fscrypt_mode *mode,
const u8 *raw_key, const struct inode *inode)
{
struct fscrypt_master_key *mk;
struct fscrypt_direct_key *dk;
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;
dk = find_or_insert_direct_key(NULL, raw_key, mode, ci);
if (dk)
return dk;
/* Nope, allocate one. */
mk = kzalloc(sizeof(*mk), GFP_NOFS);
if (!mk)
dk = kzalloc(sizeof(*dk), GFP_NOFS);
if (!dk)
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;
refcount_set(&dk->dk_refcount, 1);
dk->dk_mode = mode;
dk->dk_ctfm = allocate_skcipher_for_mode(mode, raw_key, inode);
if (IS_ERR(dk->dk_ctfm)) {
err = PTR_ERR(dk->dk_ctfm);
dk->dk_ctfm = NULL;
goto err_free_dk;
}
memcpy(mk->mk_descriptor, ci->ci_master_key_descriptor,
memcpy(dk->dk_descriptor, ci->ci_master_key_descriptor,
FSCRYPT_KEY_DESCRIPTOR_SIZE);
memcpy(mk->mk_raw, raw_key, mode->keysize);
memcpy(dk->dk_raw, raw_key, mode->keysize);
return find_or_insert_master_key(mk, raw_key, mode, ci);
return find_or_insert_direct_key(dk, raw_key, mode, ci);
err_free_mk:
free_master_key(mk);
err_free_dk:
free_direct_key(dk);
return ERR_PTR(err);
}
@ -455,22 +455,22 @@ 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 fscrypt_direct_key *dk;
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;
dk = fscrypt_get_direct_key(ci, mode, raw_key, inode);
if (IS_ERR(dk))
return PTR_ERR(dk);
ctfm = dk->dk_ctfm;
} else {
mk = NULL;
dk = 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_direct_key = dk;
ci->ci_ctfm = ctfm;
if (mode->needs_essiv) {
@ -494,8 +494,8 @@ static void put_crypt_info(struct fscrypt_info *ci)
if (!ci)
return;
if (ci->ci_master_key) {
put_master_key(ci->ci_master_key);
if (ci->ci_direct_key) {
put_direct_key(ci->ci_direct_key);
} else {
crypto_free_skcipher(ci->ci_ctfm);
crypto_free_cipher(ci->ci_essiv_tfm);