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(<digest>),cbc(<cipher>))". The cipher and
> hmac keys are wrapped in the same format used by authenc.c
>
> Signed-off-by: Cristian Stoica <cristian.stoica@xxxxxxxxxxxxx>
> ---
> 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(<digest>),cbc(<cipher>))".
> +
> + 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 <crypto/aead.h>
> +#include <crypto/internal/hash.h>
> +#include <crypto/internal/skcipher.h>
> +#include <crypto/authenc.h>
> +#include <crypto/scatterwalk.h>
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +
> +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
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