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big key: get rid of stack array allocation

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We're interested in getting rid of all of the stack allocated arrays in the
kernel [1]. This patch simply hardcodes the iv length to match that of the
hardcoded cipher.

[1]: https://lkml.org/lkml/2018/3/7/621

v2: hardcode the length of the nonce to be the GCM AES IV length, and do a
    sanity check in init(), Eric Biggers
v3: * remember to free big_key_aead when sanity check fails
    * define a constant for big key IV size so it can be changed along side
      the algorithm in the code

Signed-off-by: Tycho Andersen <tycho@tycho.ws>
Reviewed-by: Kees Cook <keescook@chromium.org>
CC: David Howells <dhowells@redhat.com>
CC: James Morris <jmorris@namei.org>
CC: "Serge E. Hallyn" <serge@hallyn.com>
CC: Jason A. Donenfeld <Jason@zx2c4.com>
CC: Eric Biggers <ebiggers3@gmail.com>
Signed-off-by: James Morris <james.morris@microsoft.com>
This commit is contained in:
Tycho Andersen 2018-04-24 14:26:37 -06:00 • committed by James Morris
parent 5859cdf550
commit a964f39561
1 changed files with 10 additions and 1 deletions
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11
security/keys/big_key.c
View file

@ -22,6 +22,7 @@
#include <keys/user-type.h> #include <keys/user-type.h>
#include <keys/big_key-type.h> #include <keys/big_key-type.h>
#include <crypto/aead.h> #include <crypto/aead.h>
#include <crypto/gcm.h>
struct big_key_buf { struct big_key_buf {
unsigned int nr_pages; unsigned int nr_pages;
@ -85,6 +86,7 @@ struct key_type key_type_big_key = {
* Crypto names for big_key data authenticated encryption * Crypto names for big_key data authenticated encryption
*/ */
static const char big_key_alg_name[] = "gcm(aes)"; static const char big_key_alg_name[] = "gcm(aes)";
#define BIG_KEY_IV_SIZE GCM_AES_IV_SIZE
/* /*
* Crypto algorithms for big_key data authenticated encryption * Crypto algorithms for big_key data authenticated encryption
@ -109,7 +111,7 @@ static int big_key_crypt(enum big_key_op op, struct big_key_buf *buf, size_t dat
* an .update function, so there's no chance we'll wind up reusing the * an .update function, so there's no chance we'll wind up reusing the
* key to encrypt updated data. Simply put: one key, one encryption. * key to encrypt updated data. Simply put: one key, one encryption.
*/ */
u8 zero_nonce[crypto_aead_ivsize(big_key_aead)]; u8 zero_nonce[BIG_KEY_IV_SIZE];
aead_req = aead_request_alloc(big_key_aead, GFP_KERNEL); aead_req = aead_request_alloc(big_key_aead, GFP_KERNEL);
if (!aead_req) if (!aead_req)
@ -425,6 +427,13 @@ static int __init big_key_init(void)
pr_err("Can't alloc crypto: %d\n", ret); pr_err("Can't alloc crypto: %d\n", ret);
return ret; return ret;
} }
if (unlikely(crypto_aead_ivsize(big_key_aead) != BIG_KEY_IV_SIZE)) {
WARN(1, "big key algorithm changed?");
ret = -EINVAL;
goto free_aead;
}
ret = crypto_aead_setauthsize(big_key_aead, ENC_AUTHTAG_SIZE); ret = crypto_aead_setauthsize(big_key_aead, ENC_AUTHTAG_SIZE);
if (ret < 0) { if (ret < 0) {
pr_err("Can't set crypto auth tag len: %d\n", ret); pr_err("Can't set crypto auth tag len: %d\n", ret);