5.0-stable review patch. If anyone has any objections, please let me know.
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From: Eric Biggers ebiggers@google.com
commit b3e3e2db7de4a1ffe8845876c3520b866cd48de1 upstream.
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: e497c51896b3 ("crypto: ofb - add output feedback mode") Cc: stable@vger.kernel.org # v4.20+ Cc: Gilad Ben-Yossef gilad@benyossef.com Signed-off-by: Eric Biggers ebiggers@google.com Reviewed-by: Gilad Ben-Yossef gilad@benyossef.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- crypto/ofb.c | 91 ++++++++++++++++++++++--------------------------------- crypto/testmgr.h | 28 +++++++++++++++- 2 files changed, 63 insertions(+), 56 deletions(-)
--- 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 <crypto/algapi.h> @@ -21,7 +18,6 @@
struct crypto_ofb_ctx { struct crypto_cipher *child; - int cnt; };
@@ -41,58 +37,40 @@ static int crypto_ofb_setkey(struct cryp return err; }
-static int crypto_ofb_encrypt_segment(struct crypto_ofb_ctx *ctx, - struct skcipher_walk *walk, - struct crypto_cipher *tfm) -{ - 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) +static int crypto_ofb_crypt(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; + + do { + crypto_cipher_encrypt_one(cipher, iv, iv); + crypto_xor_cpy(dst, src, iv, bsize); + dst += bsize; + src += bsize; + } while ((nbytes -= bsize) >= bsize);
- while (walk.nbytes) { - ret = crypto_ofb_encrypt_segment(ctx, &walk, child); - ret = skcipher_walk_done(&walk, ret); + err = skcipher_walk_done(&walk, nbytes); }
- return ret; -} - -/* 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 cryp 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 cryp 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;
--- a/crypto/testmgr.h +++ b/crypto/testmgr.h @@ -16681,8 +16681,7 @@ static const struct cipher_testvec aes_c };
static const struct cipher_testvec aes_ofb_tv_template[] = { - /* From NIST Special Publication 800-38A, Appendix F.5 */ - { + { /* From NIST Special Publication 800-38A, Appendix F.5 */ .key = "\x2b\x7e\x15\x16\x28\xae\xd2\xa6" "\xab\xf7\x15\x88\x09\xcf\x4f\x3c", .klen = 16, @@ -16705,6 +16704,31 @@ static const struct cipher_testvec aes_o "\x30\x4c\x65\x28\xf6\x59\xc7\x78" "\x66\xa5\x10\xd9\xc1\xd6\xae\x5e", .len = 64, + .also_non_np = 1, + .np = 2, + .tap = { 31, 33 }, + }, { /* > 16 bytes, not a multiple of 16 bytes */ + .key = "\x2b\x7e\x15\x16\x28\xae\xd2\xa6" + "\xab\xf7\x15\x88\x09\xcf\x4f\x3c", + .klen = 16, + .iv = "\x00\x01\x02\x03\x04\x05\x06\x07" + "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f", + .ptext = "\x6b\xc1\xbe\xe2\x2e\x40\x9f\x96" + "\xe9\x3d\x7e\x11\x73\x93\x17\x2a" + "\xae", + .ctext = "\x3b\x3f\xd9\x2e\xb7\x2d\xad\x20" + "\x33\x34\x49\xf8\xe8\x3c\xfb\x4a" + "\x77", + .len = 17, + }, { /* < 16 bytes */ + .key = "\x2b\x7e\x15\x16\x28\xae\xd2\xa6" + "\xab\xf7\x15\x88\x09\xcf\x4f\x3c", + .klen = 16, + .iv = "\x00\x01\x02\x03\x04\x05\x06\x07" + "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f", + .ptext = "\x6b\xc1\xbe\xe2\x2e\x40\x9f", + .ctext = "\x3b\x3f\xd9\x2e\xb7\x2d\xad", + .len = 7, } };