[PATCH 1/24] crypto: des_generic - Forbid 2-key in 3DES and add helpers

Herbert Xu
2019-04-11T08:50:59Z

This patch adds a requirement to the generic 3DES implementation
such that 2-key 3DES (K1 == K3) is no longer allowed in FIPS mode.

We will also provide helpers that may be used by drivers that
implement 3DES to make the same check.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

crypto/des_generic.c | 11 ++++-------
include/crypto/des.h | 43 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 47 insertions(+), 7 deletions(-)

diff --git a/crypto/des_generic.c b/crypto/des_generic.c
index 1e6621665dd9..ebec1fb08c45 100644
--- a/crypto/des_generic.c
+++ b/crypto/des_generic.c
@@ -862,14 +862,11 @@ static void des_decrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
int __des3_ede_setkey(u32 *expkey, u32 *flags, const u8 *key,
unsigned int keylen)
{
- const u32 *K = (const u32 *)key;
+ int err;

- if (unlikely(!((K[0] ^ K[2]) | (K[1] ^ K[3])) ||
- !((K[2] ^ K[4]) | (K[3] ^ K[5]))) &&
- (*flags & CRYPTO_TFM_REQ_FORBID_WEAK_KEYS)) {
- *flags |= CRYPTO_TFM_RES_WEAK_KEY;
- return -EINVAL;
- }
+ err = __des3_verify_key(flags, key);
+ if (unlikely(err))
+ return err;

des_ekey(expkey, key); expkey += DES_EXPKEY_WORDS; key += DES_KEY_SIZE;
dkey(expkey, key); expkey += DES_EXPKEY_WORDS; key += DES_KEY_SIZE;
diff --git a/include/crypto/des.h b/include/crypto/des.h
index d4094d58ac54..72c7c8e5a5a7 100644
--- a/include/crypto/des.h
+++ b/include/crypto/des.h
@@ -6,6 +6,11 @@
#ifndef __CRYPTO_DES_H
#define __CRYPTO_DES_H

+#include <crypto/skcipher.h>
+#include <linux/compiler.h>
+#include <linux/fips.h>
+#include <linux/string.h>
+
#define DES_KEY_SIZE 8
#define DES_EXPKEY_WORDS 32
#define DES_BLOCK_SIZE 8
@@ -14,6 +19,44 @@
#define DES3_EDE_EXPKEY_WORDS (3 * DES_EXPKEY_WORDS)
#define DES3_EDE_BLOCK_SIZE DES_BLOCK_SIZE

+static inline int __des3_verify_key(u32 *flags, const u8 *key)
+{
+ int err = -EINVAL;
+ u32 K[6];
+
+ memcpy(K, key, DES3_EDE_KEY_SIZE);
+
+ if (unlikely(!((K[0] ^ K[2]) | (K[1] ^ K[3])) ||
+ !((K[2] ^ K[4]) | (K[3] ^ K[5]))) &&
+ (fips_enabled ||
+ (*flags & CRYPTO_TFM_REQ_FORBID_WEAK_KEYS)))
+ goto bad;
+
+ if (unlikely(!((K[0] ^ K[4]) | (K[1] ^ K[5]))) && fips_enabled)
+ goto bad;
+
+ err = 0;
+
+out:
+ memzero_explicit(K, DES3_EDE_KEY_SIZE);
+
+ return err;
+
+bad:
+ *flags |= CRYPTO_TFM_RES_WEAK_KEY;
+ goto out;
+}
+
+static inline int des3_verify_key(struct crypto_skcipher *tfm, const u8 *key)
+{
+ u32 flags;
+ int err;
+
+ flags = crypto_skcipher_get_flags(tfm);
+ err = __des3_verify_key(&flags, key);
+ crypto_skcipher_set_flags(tfm, flags);
+ return err;
+}

extern unsigned long des_ekey(u32 *pe, const u8 *k);