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Date: Mon, 9 Apr 2018 15:54:46 +0200
From: Salvatore Mesoraca <s.mesoraca16@...il.com>
To: linux-kernel@...r.kernel.org
Cc: kernel-hardening@...ts.openwall.com,
linux-crypto@...r.kernel.org,
"David S. Miller" <davem@...emloft.net>,
Herbert Xu <herbert@...dor.apana.org.au>,
Kees Cook <keescook@...omium.org>,
Salvatore Mesoraca <s.mesoraca16@...il.com>,
Eric Biggers <ebiggers3@...il.com>,
Laura Abbott <labbott@...hat.com>
Subject: [PATCH v2 1/2] crypto: api - laying defines and checks for statically allocated buffers
In preparation for the removal of VLAs[1] from crypto code.
We create 2 new compile-time constants: all ciphers implemented
in Linux have a block size less than or equal to 16 bytes and
the most demanding hw require 16 bytes alignment for the block
buffer.
We also enforce these limits in crypto_check_alg when a new
cipher is registered.
[1] http://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
Signed-off-by: Salvatore Mesoraca <s.mesoraca16@...il.com>
---
crypto/algapi.c | 10 ++++++++++
include/crypto/algapi.h | 8 ++++++++
2 files changed, 18 insertions(+)
diff --git a/crypto/algapi.c b/crypto/algapi.c
index 2a0271b..c0755cf 100644
--- a/crypto/algapi.c
+++ b/crypto/algapi.c
@@ -10,6 +10,7 @@
*
*/
+#include <crypto/algapi.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/fips.h>
@@ -59,6 +60,15 @@ static int crypto_check_alg(struct crypto_alg *alg)
if (alg->cra_blocksize > PAGE_SIZE / 8)
return -EINVAL;
+ if (!alg->cra_type && (alg->cra_flags & CRYPTO_ALG_TYPE_MASK) ==
+ CRYPTO_ALG_TYPE_CIPHER) {
+ if (alg->cra_alignmask > MAX_CIPHER_ALIGNMASK)
+ return -EINVAL;
+
+ if (alg->cra_blocksize > MAX_CIPHER_BLOCKSIZE)
+ return -EINVAL;
+ }
+
if (alg->cra_priority < 0)
return -EINVAL;
diff --git a/include/crypto/algapi.h b/include/crypto/algapi.h
index 1aba888..bd5e8cc 100644
--- a/include/crypto/algapi.h
+++ b/include/crypto/algapi.h
@@ -17,6 +17,14 @@
#include <linux/kernel.h>
#include <linux/skbuff.h>
+/*
+ * Maximum values for blocksize and alignmask, used to allocate
+ * static buffers that are big enough for any combination of
+ * ciphers and architectures.
+ */
+#define MAX_CIPHER_BLOCKSIZE 16
+#define MAX_CIPHER_ALIGNMASK 15
+
struct crypto_aead;
struct crypto_instance;
struct module;
--
1.9.1
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