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Commit a964f395 authored by Tycho Andersen's avatar Tycho Andersen Committed by James Morris
Browse files

big key: get rid of stack array allocation 

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: default avatarTycho Andersen <tycho@tycho.ws>
Reviewed-by: default avatarKees 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: default avatarJames Morris <james.morris@microsoft.com>
parent 5859cdf5

security/keys/big_key.c

+10 −1
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <keys/user-type.h>

#include <keys/big_key-type.h>

#include <crypto/aead.h>

#include <crypto/gcm.h>



struct big_key_buf {

	unsigned int		nr_pages;
@@ -85,6 +86,7 @@ struct key_type key_type_big_key = { 
 * Crypto names for big_key data authenticated encryption

 */

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
@@ -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

	 * 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);

	if (!aead_req)
@@ -425,6 +427,13 @@ static int __init big_key_init(void) 
		pr_err("Can't alloc crypto: %d\n", 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);

	if (ret < 0) {

		pr_err("Can't set crypto auth tag len: %d\n", ret);