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Message-Id: <20180424202639.19830-1-tycho@tycho.ws>
Date: Tue, 24 Apr 2018 14:26:37 -0600
From: Tycho Andersen <tycho@...ho.ws>
To: David Howells <dhowells@...hat.com>
Cc: keyrings@...r.kernel.org,
linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com,
Tycho Andersen <tycho@...ho.ws>,
James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>,
"Jason A . Donenfeld" <Jason@...c4.com>,
Eric Biggers <ebiggers3@...il.com>
Subject: [PATCH v3 1/3] 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: Tycho Andersen <tycho@...ho.ws>
CC: David Howells <dhowells@...hat.com>
CC: James Morris <jmorris@...ei.org>
CC: "Serge E. Hallyn" <serge@...lyn.com>
CC: Jason A. Donenfeld <Jason@...c4.com>
CC: Eric Biggers <ebiggers3@...il.com>
---
security/keys/big_key.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/security/keys/big_key.c b/security/keys/big_key.c
index 933623784ccd..2806e70d7f8f 100644
--- a/security/keys/big_key.c
+++ b/security/keys/big_key.c
@@ -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);
--
2.17.0
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