From 563344438270aa0743c7b9bc0b55618dd21f8be7 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Thu, 3 Jan 2019 20:16:12 -0800 Subject: crypto: ofb - fix handling partial blocks and make thread-safe Fix multiple bugs in the OFB implementation: 1. It stored the per-request state 'cnt' in the tfm context, which can be used by multiple threads concurrently (e.g. via AF_ALG). 2. It didn't support messages not a multiple of the block cipher size, despite being a stream cipher. 3. It didn't set cra_blocksize to 1 to indicate it is a stream cipher. To fix these, set the 'chunksize' property to the cipher block size to guarantee that when walking through the scatterlist, a partial block can only occur at the end. Then change the implementation to XOR a block at a time at first, then XOR the partial block at the end if needed. This is the same way CTR and CFB are implemented. As a bonus, this also improves performance in most cases over the current approach. Fixes: 6ca6d5d18294 ("crypto: ofb - add output feedback mode") Cc: # v4.20+ Cc: Gilad Ben-Yossef Signed-off-by: Eric Biggers Reviewed-by: Gilad Ben-Yossef Signed-off-by: Herbert Xu --- crypto/ofb.c | 91 ++++++++++++++++++++++++------------------------------------ 1 file changed, 37 insertions(+), 54 deletions(-) (limited to 'crypto/ofb.c') diff --git a/crypto/ofb.c b/crypto/ofb.c index 88663170..cab0b809 100644 --- a/crypto/ofb.c +++ b/crypto/ofb.c @@ -5,9 +5,6 @@ * * Copyright (C) 2018 ARM Limited or its affiliates. * All rights reserved. - * - * Based loosely on public domain code gleaned from libtomcrypt - * (https://github.com/libtom/libtomcrypt). */ #include @@ -21,7 +18,6 @@ struct crypto_ofb_ctx { struct crypto_cipher *child; - int cnt; }; @@ -41,58 +37,40 @@ static int crypto_ofb_setkey(struct crypto_skcipher *parent, const u8 *key, return err; } -static int crypto_ofb_encrypt_segment(struct crypto_ofb_ctx *ctx, - struct skcipher_walk *walk, - struct crypto_cipher *tfm) +static int crypto_ofb_crypt(struct skcipher_request *req) { - int bsize = crypto_cipher_blocksize(tfm); - int nbytes = walk->nbytes; - - u8 *src = walk->src.virt.addr; - u8 *dst = walk->dst.virt.addr; - u8 *iv = walk->iv; - - do { - if (ctx->cnt == bsize) { - if (nbytes < bsize) - break; - crypto_cipher_encrypt_one(tfm, iv, iv); - ctx->cnt = 0; - } - *dst = *src ^ iv[ctx->cnt]; - src++; - dst++; - ctx->cnt++; - } while (--nbytes); - return nbytes; -} - -static int crypto_ofb_encrypt(struct skcipher_request *req) -{ - struct skcipher_walk walk; struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); - unsigned int bsize; struct crypto_ofb_ctx *ctx = crypto_skcipher_ctx(tfm); - struct crypto_cipher *child = ctx->child; - int ret = 0; + struct crypto_cipher *cipher = ctx->child; + const unsigned int bsize = crypto_cipher_blocksize(cipher); + struct skcipher_walk walk; + int err; - bsize = crypto_cipher_blocksize(child); - ctx->cnt = bsize; + err = skcipher_walk_virt(&walk, req, false); - ret = skcipher_walk_virt(&walk, req, false); + while (walk.nbytes >= bsize) { + const u8 *src = walk.src.virt.addr; + u8 *dst = walk.dst.virt.addr; + u8 * const iv = walk.iv; + unsigned int nbytes = walk.nbytes; - while (walk.nbytes) { - ret = crypto_ofb_encrypt_segment(ctx, &walk, child); - ret = skcipher_walk_done(&walk, ret); - } + do { + crypto_cipher_encrypt_one(cipher, iv, iv); + crypto_xor_cpy(dst, src, iv, bsize); + dst += bsize; + src += bsize; + } while ((nbytes -= bsize) >= bsize); - return ret; -} + err = skcipher_walk_done(&walk, nbytes); + } -/* OFB encrypt and decrypt are identical */ -static int crypto_ofb_decrypt(struct skcipher_request *req) -{ - return crypto_ofb_encrypt(req); + if (walk.nbytes) { + crypto_cipher_encrypt_one(cipher, walk.iv, walk.iv); + crypto_xor_cpy(walk.dst.virt.addr, walk.src.virt.addr, walk.iv, + walk.nbytes); + err = skcipher_walk_done(&walk, 0); + } + return err; } static int crypto_ofb_init_tfm(struct crypto_skcipher *tfm) @@ -165,13 +143,18 @@ static int crypto_ofb_create(struct crypto_template *tmpl, struct rtattr **tb) if (err) goto err_drop_spawn; + /* OFB mode is a stream cipher. */ + inst->alg.base.cra_blocksize = 1; + + /* + * To simplify the implementation, configure the skcipher walk to only + * give a partial block at the very end, never earlier. + */ + inst->alg.chunksize = alg->cra_blocksize; + inst->alg.base.cra_priority = alg->cra_priority; - inst->alg.base.cra_blocksize = alg->cra_blocksize; inst->alg.base.cra_alignmask = alg->cra_alignmask; - /* We access the data as u32s when xoring. */ - inst->alg.base.cra_alignmask |= __alignof__(u32) - 1; - inst->alg.ivsize = alg->cra_blocksize; inst->alg.min_keysize = alg->cra_cipher.cia_min_keysize; inst->alg.max_keysize = alg->cra_cipher.cia_max_keysize; @@ -182,8 +165,8 @@ static int crypto_ofb_create(struct crypto_template *tmpl, struct rtattr **tb) inst->alg.exit = crypto_ofb_exit_tfm; inst->alg.setkey = crypto_ofb_setkey; - inst->alg.encrypt = crypto_ofb_encrypt; - inst->alg.decrypt = crypto_ofb_decrypt; + inst->alg.encrypt = crypto_ofb_crypt; + inst->alg.decrypt = crypto_ofb_crypt; inst->free = crypto_ofb_free; -- cgit v1.2.3 From 4a9a6c703f04833f758d854556bc41efc6ba082f Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Thu, 3 Jan 2019 20:16:20 -0800 Subject: crypto: ofb - convert to skcipher_alloc_instance_simple() The OFB template just wraps a single block cipher algorithm, so simplify it by converting it to use skcipher_alloc_instance_simple(). Cc: Gilad Ben-Yossef Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu --- crypto/ofb.c | 119 ++++------------------------------------------------------- 1 file changed, 7 insertions(+), 112 deletions(-) (limited to 'crypto/ofb.c') diff --git a/crypto/ofb.c b/crypto/ofb.c index cab0b809..34b6e1f4 100644 --- a/crypto/ofb.c +++ b/crypto/ofb.c @@ -13,35 +13,11 @@ #include #include #include -#include -#include - -struct crypto_ofb_ctx { - struct crypto_cipher *child; -}; - - -static int crypto_ofb_setkey(struct crypto_skcipher *parent, const u8 *key, - unsigned int keylen) -{ - struct crypto_ofb_ctx *ctx = crypto_skcipher_ctx(parent); - struct crypto_cipher *child = ctx->child; - int err; - - crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK); - crypto_cipher_set_flags(child, crypto_skcipher_get_flags(parent) & - CRYPTO_TFM_REQ_MASK); - err = crypto_cipher_setkey(child, key, keylen); - crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(child) & - CRYPTO_TFM_RES_MASK); - return err; -} static int crypto_ofb_crypt(struct skcipher_request *req) { struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); - struct crypto_ofb_ctx *ctx = crypto_skcipher_ctx(tfm); - struct crypto_cipher *cipher = ctx->child; + struct crypto_cipher *cipher = skcipher_cipher_simple(tfm); const unsigned int bsize = crypto_cipher_blocksize(cipher); struct skcipher_walk walk; int err; @@ -73,75 +49,15 @@ static int crypto_ofb_crypt(struct skcipher_request *req) return err; } -static int crypto_ofb_init_tfm(struct crypto_skcipher *tfm) -{ - struct skcipher_instance *inst = skcipher_alg_instance(tfm); - struct crypto_spawn *spawn = skcipher_instance_ctx(inst); - struct crypto_ofb_ctx *ctx = crypto_skcipher_ctx(tfm); - struct crypto_cipher *cipher; - - cipher = crypto_spawn_cipher(spawn); - if (IS_ERR(cipher)) - return PTR_ERR(cipher); - - ctx->child = cipher; - return 0; -} - -static void crypto_ofb_exit_tfm(struct crypto_skcipher *tfm) -{ - struct crypto_ofb_ctx *ctx = crypto_skcipher_ctx(tfm); - - crypto_free_cipher(ctx->child); -} - -static void crypto_ofb_free(struct skcipher_instance *inst) -{ - crypto_drop_skcipher(skcipher_instance_ctx(inst)); - kfree(inst); -} - static int crypto_ofb_create(struct crypto_template *tmpl, struct rtattr **tb) { struct skcipher_instance *inst; - struct crypto_attr_type *algt; - struct crypto_spawn *spawn; struct crypto_alg *alg; - u32 mask; int err; - err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER); - if (err) - return err; - - inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL); - if (!inst) - return -ENOMEM; - - algt = crypto_get_attr_type(tb); - err = PTR_ERR(algt); - if (IS_ERR(algt)) - goto err_free_inst; - - mask = CRYPTO_ALG_TYPE_MASK | - crypto_requires_off(algt->type, algt->mask, - CRYPTO_ALG_NEED_FALLBACK); - - alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, mask); - err = PTR_ERR(alg); - if (IS_ERR(alg)) - goto err_free_inst; - - spawn = skcipher_instance_ctx(inst); - err = crypto_init_spawn(spawn, alg, skcipher_crypto_instance(inst), - CRYPTO_ALG_TYPE_MASK); - crypto_mod_put(alg); - if (err) - goto err_free_inst; - - err = crypto_inst_setname(skcipher_crypto_instance(inst), "ofb", alg); - if (err) - goto err_drop_spawn; + inst = skcipher_alloc_instance_simple(tmpl, tb, &alg); + if (IS_ERR(inst)) + return PTR_ERR(inst); /* OFB mode is a stream cipher. */ inst->alg.base.cra_blocksize = 1; @@ -152,36 +68,15 @@ static int crypto_ofb_create(struct crypto_template *tmpl, struct rtattr **tb) */ inst->alg.chunksize = alg->cra_blocksize; - inst->alg.base.cra_priority = alg->cra_priority; - inst->alg.base.cra_alignmask = alg->cra_alignmask; - - inst->alg.ivsize = alg->cra_blocksize; - inst->alg.min_keysize = alg->cra_cipher.cia_min_keysize; - inst->alg.max_keysize = alg->cra_cipher.cia_max_keysize; - - inst->alg.base.cra_ctxsize = sizeof(struct crypto_ofb_ctx); - - inst->alg.init = crypto_ofb_init_tfm; - inst->alg.exit = crypto_ofb_exit_tfm; - - inst->alg.setkey = crypto_ofb_setkey; inst->alg.encrypt = crypto_ofb_crypt; inst->alg.decrypt = crypto_ofb_crypt; - inst->free = crypto_ofb_free; - err = skcipher_register_instance(tmpl, inst); if (err) - goto err_drop_spawn; + inst->free(inst); -out: + crypto_mod_put(alg); return err; - -err_drop_spawn: - crypto_drop_spawn(spawn); -err_free_inst: - kfree(inst); - goto out; } static struct crypto_template crypto_ofb_tmpl = { @@ -204,5 +99,5 @@ module_init(crypto_ofb_module_init); module_exit(crypto_ofb_module_exit); MODULE_LICENSE("GPL"); -MODULE_DESCRIPTION("OFB block cipher algorithm"); +MODULE_DESCRIPTION("OFB block cipher mode of operation"); MODULE_ALIAS_CRYPTO("ofb"); -- cgit v1.2.3