diff options
author | Eric Biggers <ebiggers@google.com> | 2017-06-08 16:48:25 +0300 |
---|---|---|
committer | James Morris <james.l.morris@oracle.com> | 2017-06-09 06:29:47 +0300 |
commit | 64d107d3acca1565c39c044c459fd18f70943534 (patch) | |
tree | 3de8ea038fc4373d65160503fc039d26aa84b129 /security/keys | |
parent | 794b4bc292f5d31739d89c0202c54e7dc9bc3add (diff) | |
download | linux-64d107d3acca1565c39c044c459fd18f70943534.tar.xz |
KEYS: encrypted: fix race causing incorrect HMAC calculations
The encrypted-keys module was using a single global HMAC transform,
which could be rekeyed by multiple threads concurrently operating on
different keys, causing incorrect HMAC values to be calculated. Fix
this by allocating a new HMAC transform whenever we need to calculate a
HMAC. Also simplify things a bit by allocating the shash_desc's using
SHASH_DESC_ON_STACK() for both the HMAC and unkeyed hashes.
The following script reproduces the bug:
keyctl new_session
keyctl add user master "abcdefghijklmnop" @s
for i in $(seq 2); do
(
set -e
for j in $(seq 1000); do
keyid=$(keyctl add encrypted desc$i "new user:master 25" @s)
datablob="$(keyctl pipe $keyid)"
keyctl unlink $keyid > /dev/null
keyid=$(keyctl add encrypted desc$i "load $datablob" @s)
keyctl unlink $keyid > /dev/null
done
) &
done
Output with bug:
[ 439.691094] encrypted_key: bad hmac (-22)
add_key: Invalid argument
add_key: Invalid argument
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
Diffstat (limited to 'security/keys')
-rw-r--r-- | security/keys/encrypted-keys/encrypted.c | 115 |
1 files changed, 32 insertions, 83 deletions
diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c index 0f7b95de3b5f..702c80662069 100644 --- a/security/keys/encrypted-keys/encrypted.c +++ b/security/keys/encrypted-keys/encrypted.c @@ -54,13 +54,7 @@ static int blksize; #define MAX_DATA_SIZE 4096 #define MIN_DATA_SIZE 20 -struct sdesc { - struct shash_desc shash; - char ctx[]; -}; - -static struct crypto_shash *hashalg; -static struct crypto_shash *hmacalg; +static struct crypto_shash *hash_tfm; enum { Opt_err = -1, Opt_new, Opt_load, Opt_update @@ -320,53 +314,38 @@ error: return ukey; } -static struct sdesc *alloc_sdesc(struct crypto_shash *alg) -{ - struct sdesc *sdesc; - int size; - - size = sizeof(struct shash_desc) + crypto_shash_descsize(alg); - sdesc = kmalloc(size, GFP_KERNEL); - if (!sdesc) - return ERR_PTR(-ENOMEM); - sdesc->shash.tfm = alg; - sdesc->shash.flags = 0x0; - return sdesc; -} - -static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen, +static int calc_hash(struct crypto_shash *tfm, u8 *digest, const u8 *buf, unsigned int buflen) { - struct sdesc *sdesc; - int ret; + SHASH_DESC_ON_STACK(desc, tfm); + int err; - sdesc = alloc_sdesc(hmacalg); - if (IS_ERR(sdesc)) { - pr_info("encrypted_key: can't alloc %s\n", hmac_alg); - return PTR_ERR(sdesc); - } + desc->tfm = tfm; + desc->flags = 0; - ret = crypto_shash_setkey(hmacalg, key, keylen); - if (!ret) - ret = crypto_shash_digest(&sdesc->shash, buf, buflen, digest); - kfree(sdesc); - return ret; + err = crypto_shash_digest(desc, buf, buflen, digest); + shash_desc_zero(desc); + return err; } -static int calc_hash(u8 *digest, const u8 *buf, unsigned int buflen) +static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen, + const u8 *buf, unsigned int buflen) { - struct sdesc *sdesc; - int ret; + struct crypto_shash *tfm; + int err; - sdesc = alloc_sdesc(hashalg); - if (IS_ERR(sdesc)) { - pr_info("encrypted_key: can't alloc %s\n", hash_alg); - return PTR_ERR(sdesc); + tfm = crypto_alloc_shash(hmac_alg, 0, CRYPTO_ALG_ASYNC); + if (IS_ERR(tfm)) { + pr_err("encrypted_key: can't alloc %s transform: %ld\n", + hmac_alg, PTR_ERR(tfm)); + return PTR_ERR(tfm); } - ret = crypto_shash_digest(&sdesc->shash, buf, buflen, digest); - kfree(sdesc); - return ret; + err = crypto_shash_setkey(tfm, key, keylen); + if (!err) + err = calc_hash(tfm, digest, buf, buflen); + crypto_free_shash(tfm); + return err; } enum derived_key_type { ENC_KEY, AUTH_KEY }; @@ -394,7 +373,7 @@ static int get_derived_key(u8 *derived_key, enum derived_key_type key_type, memcpy(derived_buf + strlen(derived_buf) + 1, master_key, master_keylen); - ret = calc_hash(derived_key, derived_buf, derived_buf_len); + ret = calc_hash(hash_tfm, derived_key, derived_buf, derived_buf_len); kfree(derived_buf); return ret; } @@ -998,47 +977,17 @@ struct key_type key_type_encrypted = { }; EXPORT_SYMBOL_GPL(key_type_encrypted); -static void encrypted_shash_release(void) -{ - if (hashalg) - crypto_free_shash(hashalg); - if (hmacalg) - crypto_free_shash(hmacalg); -} - -static int __init encrypted_shash_alloc(void) +static int __init init_encrypted(void) { int ret; - hmacalg = crypto_alloc_shash(hmac_alg, 0, CRYPTO_ALG_ASYNC); - if (IS_ERR(hmacalg)) { - pr_info("encrypted_key: could not allocate crypto %s\n", - hmac_alg); - return PTR_ERR(hmacalg); + hash_tfm = crypto_alloc_shash(hash_alg, 0, CRYPTO_ALG_ASYNC); + if (IS_ERR(hash_tfm)) { + pr_err("encrypted_key: can't allocate %s transform: %ld\n", + hash_alg, PTR_ERR(hash_tfm)); + return PTR_ERR(hash_tfm); } - hashalg = crypto_alloc_shash(hash_alg, 0, CRYPTO_ALG_ASYNC); - if (IS_ERR(hashalg)) { - pr_info("encrypted_key: could not allocate crypto %s\n", - hash_alg); - ret = PTR_ERR(hashalg); - goto hashalg_fail; - } - - return 0; - -hashalg_fail: - crypto_free_shash(hmacalg); - return ret; -} - -static int __init init_encrypted(void) -{ - int ret; - - ret = encrypted_shash_alloc(); - if (ret < 0) - return ret; ret = aes_get_sizes(); if (ret < 0) goto out; @@ -1047,14 +996,14 @@ static int __init init_encrypted(void) goto out; return 0; out: - encrypted_shash_release(); + crypto_free_shash(hash_tfm); return ret; } static void __exit cleanup_encrypted(void) { - encrypted_shash_release(); + crypto_free_shash(hash_tfm); unregister_key_type(&key_type_encrypted); } |