diff options
| -rw-r--r-- | crypto/Makefile | 7 | ||||
| -rw-r--r-- | crypto/asymmetric_keys/rsa.c | 5 | ||||
| -rw-r--r-- | crypto/authenc.c | 6 | ||||
| -rw-r--r-- | crypto/authencesn.c | 8 | ||||
| -rw-r--r-- | crypto/ccm.c | 4 | ||||
| -rw-r--r-- | crypto/gcm.c | 2 | ||||
| -rw-r--r-- | crypto/memneq.c | 138 | ||||
| -rw-r--r-- | include/crypto/algapi.h | 18 |
8 files changed, 174 insertions, 14 deletions
diff --git a/crypto/Makefile b/crypto/Makefile index 580af97..d6a401c 100644 --- a/crypto/Makefile +++ b/crypto/Makefile @@ -2,8 +2,13 @@ # Cryptographic API # +# memneq MUST be built with -Os or -O0 to prevent early-return optimizations +# that will defeat memneq's actual purpose to prevent timing attacks. +CFLAGS_REMOVE_memneq.o := -O1 -O2 -O3 +CFLAGS_memneq.o := -Os + obj-$(CONFIG_CRYPTO) += crypto.o -crypto-y := api.o cipher.o compress.o +crypto-y := api.o cipher.o compress.o memneq.o obj-$(CONFIG_CRYPTO_WORKQUEUE) += crypto_wq.o diff --git a/crypto/asymmetric_keys/rsa.c b/crypto/asymmetric_keys/rsa.c index 4a6a069..1912b9b 100644 --- a/crypto/asymmetric_keys/rsa.c +++ b/crypto/asymmetric_keys/rsa.c @@ -13,6 +13,7 @@ #include <linux/module.h> #include <linux/kernel.h> #include <linux/slab.h> +#include <crypto/algapi.h> #include "public_key.h" MODULE_LICENSE("GPL"); @@ -189,12 +190,12 @@ static int RSA_verify(const u8 *H, const u8 *EM, size_t k, size_t hash_size, } } - if (memcmp(asn1_template, EM + T_offset, asn1_size) != 0) { + if (crypto_memneq(asn1_template, EM + T_offset, asn1_size) != 0) { kleave(" = -EBADMSG [EM[T] ASN.1 mismatch]"); return -EBADMSG; } - if (memcmp(H, EM + T_offset + asn1_size, hash_size) != 0) { + if (crypto_memneq(H, EM + T_offset + asn1_size, hash_size) != 0) { kleave(" = -EKEYREJECTED [EM[T] hash mismatch]"); return -EKEYREJECTED; } diff --git a/crypto/authenc.c b/crypto/authenc.c index ffce19d..2b3f4ab 100644 --- a/crypto/authenc.c +++ b/crypto/authenc.c @@ -188,7 +188,7 @@ static void authenc_verify_ahash_update_done(struct crypto_async_request *areq, scatterwalk_map_and_copy(ihash, areq_ctx->sg, areq_ctx->cryptlen, authsize, 0); - err = memcmp(ihash, ahreq->result, authsize) ? -EBADMSG : 0; + err = crypto_memneq(ihash, ahreq->result, authsize) ? -EBADMSG : 0; if (err) goto out; @@ -227,7 +227,7 @@ static void authenc_verify_ahash_done(struct crypto_async_request *areq, scatterwalk_map_and_copy(ihash, areq_ctx->sg, areq_ctx->cryptlen, authsize, 0); - err = memcmp(ihash, ahreq->result, authsize) ? -EBADMSG : 0; + err = crypto_memneq(ihash, ahreq->result, authsize) ? -EBADMSG : 0; if (err) goto out; @@ -462,7 +462,7 @@ static int crypto_authenc_verify(struct aead_request *req, ihash = ohash + authsize; scatterwalk_map_and_copy(ihash, areq_ctx->sg, areq_ctx->cryptlen, authsize, 0); - return memcmp(ihash, ohash, authsize) ? -EBADMSG : 0; + return crypto_memneq(ihash, ohash, authsize) ? -EBADMSG : 0; } static int crypto_authenc_iverify(struct aead_request *req, u8 *iv, diff --git a/crypto/authencesn.c b/crypto/authencesn.c index ab53762..c569d58 100644 --- a/crypto/authencesn.c +++ b/crypto/authencesn.c @@ -247,7 +247,7 @@ static void authenc_esn_verify_ahash_update_done(struct crypto_async_request *ar scatterwalk_map_and_copy(ihash, areq_ctx->sg, areq_ctx->cryptlen, authsize, 0); - err = memcmp(ihash, ahreq->result, authsize) ? -EBADMSG : 0; + err = crypto_memneq(ihash, ahreq->result, authsize) ? -EBADMSG : 0; if (err) goto out; @@ -296,7 +296,7 @@ static void authenc_esn_verify_ahash_update_done2(struct crypto_async_request *a scatterwalk_map_and_copy(ihash, areq_ctx->sg, areq_ctx->cryptlen, authsize, 0); - err = memcmp(ihash, ahreq->result, authsize) ? -EBADMSG : 0; + err = crypto_memneq(ihash, ahreq->result, authsize) ? -EBADMSG : 0; if (err) goto out; @@ -336,7 +336,7 @@ static void authenc_esn_verify_ahash_done(struct crypto_async_request *areq, scatterwalk_map_and_copy(ihash, areq_ctx->sg, areq_ctx->cryptlen, authsize, 0); - err = memcmp(ihash, ahreq->result, authsize) ? -EBADMSG : 0; + err = crypto_memneq(ihash, ahreq->result, authsize) ? -EBADMSG : 0; if (err) goto out; @@ -568,7 +568,7 @@ static int crypto_authenc_esn_verify(struct aead_request *req) ihash = ohash + authsize; scatterwalk_map_and_copy(ihash, areq_ctx->sg, areq_ctx->cryptlen, authsize, 0); - return memcmp(ihash, ohash, authsize) ? -EBADMSG : 0; + return crypto_memneq(ihash, ohash, authsize) ? -EBADMSG : 0; } static int crypto_authenc_esn_iverify(struct aead_request *req, u8 *iv, diff --git a/crypto/ccm.c b/crypto/ccm.c index 499c917..3e05499 100644 --- a/crypto/ccm.c +++ b/crypto/ccm.c @@ -363,7 +363,7 @@ static void crypto_ccm_decrypt_done(struct crypto_async_request *areq, if (!err) { err = crypto_ccm_auth(req, req->dst, cryptlen); - if (!err && memcmp(pctx->auth_tag, pctx->odata, authsize)) + if (!err && crypto_memneq(pctx->auth_tag, pctx->odata, authsize)) err = -EBADMSG; } aead_request_complete(req, err); @@ -422,7 +422,7 @@ static int crypto_ccm_decrypt(struct aead_request *req) return err; /* verify */ - if (memcmp(authtag, odata, authsize)) + if (crypto_memneq(authtag, odata, authsize)) return -EBADMSG; return err; diff --git a/crypto/gcm.c b/crypto/gcm.c index 43e1fb0..b4f0179 100644 --- a/crypto/gcm.c +++ b/crypto/gcm.c @@ -582,7 +582,7 @@ static int crypto_gcm_verify(struct aead_request *req, crypto_xor(auth_tag, iauth_tag, 16); scatterwalk_map_and_copy(iauth_tag, req->src, cryptlen, authsize, 0); - return memcmp(iauth_tag, auth_tag, authsize) ? -EBADMSG : 0; + return crypto_memneq(iauth_tag, auth_tag, authsize) ? -EBADMSG : 0; } static void gcm_decrypt_done(struct crypto_async_request *areq, int err) diff --git a/crypto/memneq.c b/crypto/memneq.c new file mode 100644 index 0000000..cd01622 --- /dev/null +++ b/crypto/memneq.c @@ -0,0 +1,138 @@ +/* + * Constant-time equality testing of memory regions. + * + * Authors: + * + * James Yonan <james@openvpn.net> + * Daniel Borkmann <dborkman@redhat.com> + * + * This file is provided under a dual BSD/GPLv2 license. When using or + * redistributing this file, you may do so under either license. + * + * GPL LICENSE SUMMARY + * + * Copyright(c) 2013 OpenVPN Technologies, Inc. All rights reserved. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of version 2 of the GNU General Public License as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA. + * The full GNU General Public License is included in this distribution + * in the file called LICENSE.GPL. + * + * BSD LICENSE + * + * Copyright(c) 2013 OpenVPN Technologies, Inc. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * * Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * * Neither the name of OpenVPN Technologies nor the names of its + * contributors may be used to endorse or promote products derived + * from this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT + * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include <crypto/algapi.h> + +#ifndef __HAVE_ARCH_CRYPTO_MEMNEQ + +/* Generic path for arbitrary size */ +static inline unsigned long +__crypto_memneq_generic(const void *a, const void *b, size_t size) +{ + unsigned long neq = 0; + +#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) + while (size >= sizeof(unsigned long)) { + neq |= *(unsigned long *)a ^ *(unsigned long *)b; + a += sizeof(unsigned long); + b += sizeof(unsigned long); + size -= sizeof(unsigned long); + } +#endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */ + while (size > 0) { + neq |= *(unsigned char *)a ^ *(unsigned char *)b; + a += 1; + b += 1; + size -= 1; + } + return neq; +} + +/* Loop-free fast-path for frequently used 16-byte size */ +static inline unsigned long __crypto_memneq_16(const void *a, const void *b) +{ +#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS + if (sizeof(unsigned long) == 8) + return ((*(unsigned long *)(a) ^ *(unsigned long *)(b)) + | (*(unsigned long *)(a+8) ^ *(unsigned long *)(b+8))); + else if (sizeof(unsigned int) == 4) + return ((*(unsigned int *)(a) ^ *(unsigned int *)(b)) + | (*(unsigned int *)(a+4) ^ *(unsigned int *)(b+4)) + | (*(unsigned int *)(a+8) ^ *(unsigned int *)(b+8)) + | (*(unsigned int *)(a+12) ^ *(unsigned int *)(b+12))); + else +#endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */ + return ((*(unsigned char *)(a) ^ *(unsigned char *)(b)) + | (*(unsigned char *)(a+1) ^ *(unsigned char *)(b+1)) + | (*(unsigned char *)(a+2) ^ *(unsigned char *)(b+2)) + | (*(unsigned char *)(a+3) ^ *(unsigned char *)(b+3)) + | (*(unsigned char *)(a+4) ^ *(unsigned char *)(b+4)) + | (*(unsigned char *)(a+5) ^ *(unsigned char *)(b+5)) + | (*(unsigned char *)(a+6) ^ *(unsigned char *)(b+6)) + | (*(unsigned char *)(a+7) ^ *(unsigned char *)(b+7)) + | (*(unsigned char *)(a+8) ^ *(unsigned char *)(b+8)) + | (*(unsigned char *)(a+9) ^ *(unsigned char *)(b+9)) + | (*(unsigned char *)(a+10) ^ *(unsigned char *)(b+10)) + | (*(unsigned char *)(a+11) ^ *(unsigned char *)(b+11)) + | (*(unsigned char *)(a+12) ^ *(unsigned char *)(b+12)) + | (*(unsigned char *)(a+13) ^ *(unsigned char *)(b+13)) + | (*(unsigned char *)(a+14) ^ *(unsigned char *)(b+14)) + | (*(unsigned char *)(a+15) ^ *(unsigned char *)(b+15))); +} + +/* Compare two areas of memory without leaking timing information, + * and with special optimizations for common sizes. Users should + * not call this function directly, but should instead use + * crypto_memneq defined in crypto/algapi.h. + */ +noinline unsigned long __crypto_memneq(const void *a, const void *b, + size_t size) +{ + switch (size) { + case 16: + return __crypto_memneq_16(a, b); + default: + return __crypto_memneq_generic(a, b, size); + } +} +EXPORT_SYMBOL(__crypto_memneq); + +#endif /* __HAVE_ARCH_CRYPTO_MEMNEQ */ diff --git a/include/crypto/algapi.h b/include/crypto/algapi.h index 418d270..e73c19e 100644 --- a/include/crypto/algapi.h +++ b/include/crypto/algapi.h @@ -386,5 +386,21 @@ static inline int crypto_requires_sync(u32 type, u32 mask) return (type ^ CRYPTO_ALG_ASYNC) & mask & CRYPTO_ALG_ASYNC; } -#endif /* _CRYPTO_ALGAPI_H */ +noinline unsigned long __crypto_memneq(const void *a, const void *b, size_t size); + +/** + * crypto_memneq - Compare two areas of memory without leaking + * timing information. + * + * @a: One area of memory + * @b: Another area of memory + * @size: The size of the area. + * + * Returns 0 when data is equal, 1 otherwise. + */ +static inline int crypto_memneq(const void *a, const void *b, size_t size) +{ + return __crypto_memneq(a, b, size) != 0UL ? 1 : 0; +} +#endif /* _CRYPTO_ALGAPI_H */ |
