big key: get rid of stack array allocation (a964f395) · Commits · 戴 / test

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>

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);

Admin message