From: Andy Lutomirski Subject: Re: [PATCH 1/2] crypto: add support for TLS 1.0 record encryption Date: Thu, 31 Jul 2014 13:01:27 -0700 Message-ID: <53DAA097.90005@amacapital.net> References: <1406626353-23309-1-git-send-email-cristian.stoica@freescale.com> <1406626353-23309-2-git-send-email-cristian.stoica@freescale.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: davem@davemloft.net, linux-kernel@vger.kernel.org To: Cristian Stoica , herbert@gondor.apana.org.au, linux-crypto@vger.kernel.org Return-path: Received: from mail-pd0-f175.google.com ([209.85.192.175]:53214 "EHLO mail-pd0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751818AbaGaUBa (ORCPT ); Thu, 31 Jul 2014 16:01:30 -0400 Received: by mail-pd0-f175.google.com with SMTP id r10so4073835pdi.6 for ; Thu, 31 Jul 2014 13:01:30 -0700 (PDT) In-Reply-To: <1406626353-23309-2-git-send-email-cristian.stoica@freescale.com> Sender: linux-crypto-owner@vger.kernel.org List-ID: On 07/29/2014 02:32 AM, Cristian Stoica wrote: > This patch adds kernel support for encryption/decryption of TLS 1.0 > records using block ciphers. Implementation is similar to authenc in > the sense that the base algorithms (AES, SHA1) are combined in a > template to produce TLS encapsulation frames. The composite algorithm > will be called "tls10(hmac(),cbc())". The cipher and > hmac keys are wrapped in the same format used by authenc.c > > Signed-off-by: Cristian Stoica > --- > crypto/Kconfig | 20 ++ > crypto/Makefile | 1 + > crypto/authenc.c | 5 +- > crypto/tls.c | 528 +++++++++++++++++++++++++++++++++++++++++++++++ > include/crypto/authenc.h | 3 + > 5 files changed, 555 insertions(+), 2 deletions(-) > create mode 100644 crypto/tls.c > > diff --git a/crypto/Kconfig b/crypto/Kconfig > index 6345c47..54cc843 100644 > --- a/crypto/Kconfig > +++ b/crypto/Kconfig > @@ -212,6 +212,26 @@ config CRYPTO_SEQIV > This IV generator generates an IV based on a sequence number by > xoring it with a salt. This algorithm is mainly useful for CTR > > +config CRYPTO_TLS > + tristate "TLS support" > + select CRYPTO_AUTHENC > + select CRYPTO_AEAD > + select CRYPTO_BLKCIPHER > + select CRYPTO_MANAGER > + select CRYPTO_HASH > + help > + Support for TLS record encryption and decryption > + > + This module adds support for encryption/decryption of TLS frames > + using blockcipher algorithms. The resulting algorithm is called > + "tls10(hmac(),cbc())". > + > + By default, the generic base algorithms are used (e.g. aes-generic, > + sha1-generic), but hardware accelerated versions will be used > + automatically if available. > + User-space applications (OpenSSL, GnuTLS) can offload TLS operations > + through AF_ALG or cryptodev interfaces > + > comment "Block modes" > > config CRYPTO_CBC > diff --git a/crypto/Makefile b/crypto/Makefile > index cfa57b3..16088d1 100644 > --- a/crypto/Makefile > +++ b/crypto/Makefile > @@ -85,6 +85,7 @@ obj-$(CONFIG_CRYPTO_CRC32C) += crc32c_generic.o > obj-$(CONFIG_CRYPTO_CRC32) += crc32.o > obj-$(CONFIG_CRYPTO_CRCT10DIF) += crct10dif_common.o crct10dif_generic.o > obj-$(CONFIG_CRYPTO_AUTHENC) += authenc.o authencesn.o > +obj-$(CONFIG_CRYPTO_TLS) += tls.o > obj-$(CONFIG_CRYPTO_LZO) += lzo.o > obj-$(CONFIG_CRYPTO_LZ4) += lz4.o > obj-$(CONFIG_CRYPTO_LZ4HC) += lz4hc.o > diff --git a/crypto/authenc.c b/crypto/authenc.c > index e122355..7f6c65d 100644 > --- a/crypto/authenc.c > +++ b/crypto/authenc.c > @@ -82,8 +82,8 @@ int crypto_authenc_extractkeys(struct crypto_authenc_keys *keys, const u8 *key, > } > EXPORT_SYMBOL_GPL(crypto_authenc_extractkeys); > > -static int crypto_authenc_setkey(struct crypto_aead *authenc, const u8 *key, > - unsigned int keylen) > +int crypto_authenc_setkey(struct crypto_aead *authenc, const u8 *key, > + unsigned int keylen) > { > struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc); > struct crypto_ahash *auth = ctx->auth; > @@ -118,6 +118,7 @@ badkey: > crypto_aead_set_flags(authenc, CRYPTO_TFM_RES_BAD_KEY_LEN); > goto out; > } > +EXPORT_SYMBOL_GPL(crypto_authenc_setkey); > > static void authenc_geniv_ahash_update_done(struct crypto_async_request *areq, > int err) > diff --git a/crypto/tls.c b/crypto/tls.c > new file mode 100644 > index 0000000..b6aedcd > --- /dev/null > +++ b/crypto/tls.c > @@ -0,0 +1,528 @@ > +/* > + * Copyright 2014 Freescale Semiconductor, Inc. > + * > + * This program is free software; you can redistribute it and/or modify it > + * under the terms of the GNU General Public License as published by the Free > + * Software Foundation; either version 2 of the License, or (at your option) > + * any later version. > + */ > + > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +struct tls_instance_ctx { > + struct crypto_ahash_spawn auth; > + struct crypto_skcipher_spawn enc; > +}; > + > +struct crypto_tls_ctx { > + unsigned int reqoff; > + struct crypto_ahash *auth; > + struct crypto_ablkcipher *enc; > +}; > + > +struct tls_request_ctx { > + /* > + * cryptlen holds the payload length in the case of encryption or > + * payload_len + icv_len + padding_len in case of decryption > + */ > + unsigned int cryptlen; > + /* working space for partial results */ > + struct scatterlist icv[2]; > + struct scatterlist cipher[2]; > + char tail[]; > +}; > + > +struct async_op { > + struct completion completion; > + int err; > +}; > + > +static void tls_async_op_done(struct crypto_async_request *req, int err) > +{ > + struct async_op *areq = req->data; > + > + if (err == -EINPROGRESS) > + return; > + > + areq->err = err; > + complete(&areq->completion); > +} > + > +/** > + * crypto_tls_genicv - Calculate hmac digest for a TLS record > + * @hash: (output) buffer to save the digest into > + * @src: (input) scatterlist with the payload data > + * @srclen: (input) size of the payload data > + * @req: (input) aead request (with pointers to associated data) > + **/ > +static int crypto_tls_genicv(u8 *hash, struct scatterlist *src, > + unsigned int srclen, struct aead_request *req) > +{ > + struct crypto_aead *tls = crypto_aead_reqtfm(req); > + struct crypto_tls_ctx *ctx = crypto_aead_ctx(tls); > + struct tls_request_ctx *treq_ctx = aead_request_ctx(req); > + struct scatterlist *assoc = req->assoc; > + struct scatterlist *icv = treq_ctx->icv; > + struct async_op ahash_op; > + struct ahash_request *ahreq = (void *)(treq_ctx->tail + ctx->reqoff); > + unsigned int flags = CRYPTO_TFM_REQ_MAY_SLEEP; > + int err = -EBADMSG; > + > + /* > + * Bail out as we have only two maneuvering scatterlists in icv. Check > + * also if the request assoc len matches the scatterlist len > + */ > + if (!req->assoclen || !sg_is_last(assoc) || > + req->assoclen != assoc->length) > + return err; > + > + /* > + * Prepend associated data to the source scatterlist. If the source is > + * empty, use directly the associated data scatterlist > + */ > + if (srclen) { > + sg_init_table(icv, 2); > + sg_set_page(icv, sg_page(assoc), assoc->length, assoc->offset); > + scatterwalk_sg_chain(icv, 2, src); > + } else { > + icv = assoc; > + } > + srclen += assoc->length; > + > + init_completion(&ahash_op.completion); > + > + /* the hash transform to be executed comes from the original request */ > + ahash_request_set_tfm(ahreq, ctx->auth); > + /* prepare the hash request with input data and result pointer */ > + ahash_request_set_crypt(ahreq, icv, hash, srclen); > + /* set the notifier for when the async hash function returns */ > + ahash_request_set_callback(ahreq, aead_request_flags(req) & flags, > + tls_async_op_done, &ahash_op); > + > + /* Calculate the digest on the given data. The result is put in hash */ > + err = crypto_ahash_digest(ahreq); > + if (err == -EINPROGRESS) { > + err = wait_for_completion_interruptible(&ahash_op.completion); > + if (!err) > + err = ahash_op.err; > + } > + > + return err; > +} > + > +/** > + * crypto_tls_gen_padicv - Calculate and pad hmac digest for a TLS record > + * @hash: (output) buffer to save the digest and padding into > + * @phashlen: (output) the size of digest + padding > + * @req: (input) aead request > + **/ > +static int crypto_tls_gen_padicv(u8 *hash, unsigned int *phashlen, > + struct aead_request *req) > +{ > + struct crypto_aead *tls = crypto_aead_reqtfm(req); > + unsigned int hash_size = crypto_aead_authsize(tls); > + unsigned int block_size = crypto_aead_blocksize(tls); > + unsigned int srclen = req->cryptlen + hash_size; > + unsigned int padlen; > + int err; > + > + err = crypto_tls_genicv(hash, req->src, req->cryptlen, req); > + if (err) > + goto out; > + > + /* add padding after digest */ > + padlen = block_size - (srclen % block_size); > + memset(hash + hash_size, padlen - 1, padlen); > + > + *phashlen = hash_size + padlen; > +out: > + return err; > +} > + > +static int crypto_tls_encrypt(struct aead_request *req) > +{ > + struct crypto_aead *tls = crypto_aead_reqtfm(req); > + struct crypto_tls_ctx *ctx = crypto_aead_ctx(tls); > + struct tls_request_ctx *treq_ctx = aead_request_ctx(req); > + > + unsigned int cryptlen, phashlen; > + struct scatterlist *cipher = treq_ctx->cipher; > + struct scatterlist *sg, *src_last = NULL; > + int err; > + /* > + * The hash and the cipher are applied at different times and their > + * requests can use the same memory space without interference > + */ > + struct ablkcipher_request *abreq = (void *)(treq_ctx->tail + > + ctx->reqoff); > + /* > + * The hash result is saved at the beginning of the tls request and is > + * aligned as required by the hash transform. Enough space was > + * allocated in crypto_tls_init_tfm to accomodate the difference. The > + * requests themselves start later at treq_ctx->tail + ctx->reqoff so > + * the result is not overwritten by the second (cipher) request > + */ > + u8 *hash = treq_ctx->tail; > + > + hash = (u8 *)ALIGN((unsigned long)hash + > + crypto_ahash_alignmask(ctx->auth), > + crypto_ahash_alignmask(ctx->auth) + 1); > + > + /* > + * STEP 1: create ICV together with necessary padding > + */ > + err = crypto_tls_gen_padicv(hash, &phashlen, req); > + if (err) > + return err; > + > + /* > + * STEP 2: Hash and padding are combined with the payload > + * depending on the form it arrives. Scatter tables must have at least > + * one page of data before chaining with another table and can't have > + * an empty data page. The following code addresses these requirements. > + * > + * For same-destination, hash is copied directly after the > + * payload since the buffers must have enough space for encryption. > + * For different destination there are several casess to check. > + * If the payload is empty, only the hash is encrypted, otherwise the > + * payload scatterlist is merged with the hash. A special merging case > + * is when the payload has only one page of data. In that case the > + * payload page is moved to another scatterlist and prepared there for > + * encryption. > + */ > + > + if (req->src == req->dst) { > + scatterwalk_map_and_copy(hash, req->src, req->cryptlen, > + phashlen, 1); > + } else { > + if (req->cryptlen) { > + sg_init_table(cipher, 2); > + sg_set_buf(cipher + 1, hash, phashlen); > + if (sg_is_last(req->src)) { > + sg_set_page(cipher, sg_page(req->src), > + req->src->length, req->src->offset); > + req->src = cipher; > + } else { > + for (sg = req->src; sg; sg = sg_next(sg)) > + src_last = sg; > + sg_set_page(cipher, sg_page(src_last), > + src_last->length, src_last->offset); > + scatterwalk_sg_chain(src_last, 1, cipher); > + } > + } else { > + sg_init_one(req->src, hash, phashlen); > + } > + } > + > + /* > + * STEP 3: encrypt the frame and return the result > + */ > + cryptlen = req->cryptlen + phashlen; > + ablkcipher_request_set_tfm(abreq, ctx->enc); > + ablkcipher_request_set_crypt(abreq, req->src, req->dst, cryptlen, > + req->iv); > + /* set the callback for encryption request termination */ > + ablkcipher_request_set_callback(abreq, aead_request_flags(req), > + req->base.complete, req->base.data); > + /* > + * Apply the cipher transform. The result will be in req->dst when the > + * asynchronuous call terminates > + */ > + err = crypto_ablkcipher_encrypt(abreq); > + > + return err; > +} > + > +static int crypto_tls_decrypt(struct aead_request *req) > +{ > + struct crypto_aead *tls = crypto_aead_reqtfm(req); > + struct crypto_tls_ctx *ctx = crypto_aead_ctx(tls); > + struct tls_request_ctx *treq_ctx = aead_request_ctx(req); > + struct scatterlist *assoc = req->assoc; > + unsigned int cryptlen = req->cryptlen; > + unsigned int hash_size = crypto_aead_authsize(tls); > + unsigned int block_size = crypto_aead_blocksize(tls); > + struct ablkcipher_request *abreq = (void *)(treq_ctx->tail + > + ctx->reqoff); > + u8 padding[255]; /* padding can be 0-255 bytes */ > + u8 pad_size; > + u16 *len_field; > + u8 *ihash, *hash = treq_ctx->tail; > + > + int paderr = 0; > + int err = -EINVAL; > + int i; > + struct async_op ciph_op; > + > + /* > + * Rule out bad packets. The input packet length must be at least one > + * byte more than the hash_size > + */ > + if (cryptlen <= hash_size || cryptlen % block_size) > + goto out; > + > + /* > + * Step 1 - Decrypt the source > + */ > + init_completion(&ciph_op.completion); > + > + ablkcipher_request_set_tfm(abreq, ctx->enc); > + ablkcipher_request_set_callback(abreq, aead_request_flags(req), > + tls_async_op_done, &ciph_op); > + ablkcipher_request_set_crypt(abreq, req->src, req->dst, cryptlen, > + req->iv); > + err = crypto_ablkcipher_decrypt(abreq); > + if (err == -EINPROGRESS) { > + err = wait_for_completion_interruptible(&ciph_op.completion); > + if (!err) > + err = ciph_op.err; > + } > + if (err) > + goto out; > + > + /* > + * Step 2 - Verify padding > + * Retrieve the last byte of the payload; this is the padding size > + */ > + cryptlen -= 1; > + scatterwalk_map_and_copy(&pad_size, req->dst, cryptlen, 1, 0); > + > + /* RFC recommendation to defend against timing attacks is to continue > + * with hash calculation even if the padding is incorrect */ > + if (cryptlen < pad_size + hash_size) { > + pad_size = 0; > + paderr = -EBADMSG; > + } > + cryptlen -= pad_size; > + scatterwalk_map_and_copy(padding, req->dst, cryptlen, pad_size, 0); > + > + /* Padding content must be equal with pad_size. We verify it all */ > + for (i = 0; i < pad_size; i++) > + if (padding[i] != pad_size) > + paderr = -EBADMSG; > + > + /* > + * Step 3 - Verify hash > + * Align the digest result as required by the hash transform. Enough > + * space was allocated in crypto_tls_init_tfm > + */ > + hash = (u8 *)ALIGN((unsigned long)hash + > + crypto_ahash_alignmask(ctx->auth), > + crypto_ahash_alignmask(ctx->auth) + 1); > + /* > + * Two bytes at the end of the associated data make the length field. > + * It must be updated with the length of the cleartext message before > + * the hash is calculated. > + */ > + len_field = sg_virt(assoc) + assoc->length - 2; > + cryptlen -= hash_size; > + *len_field = htons(cryptlen); > + > + /* This is the hash from the decrypted packet. Save it for later */ > + ihash = hash + hash_size; > + scatterwalk_map_and_copy(ihash, req->dst, cryptlen, hash_size, 0); > + > + /* Now compute and compare our ICV with the one from the packet */ > + err = crypto_tls_genicv(hash, req->dst, cryptlen, req); > + if (!err) > + err = crypto_memneq(hash, ihash, hash_size) ? -EBADMSG : 0; This looks like it's vulnerable to the Lucky 13 attack. --Andy