Add support for the missing ciphertext stealing part of the XTS-AES specification, which permits inputs of any size >= the block size. Cc: Pascal van Leeuwen <pvanleeuwen@xxxxxxxxxxxxxx> Cc: Ondrej Mosnacek <omosnace@xxxxxxxxxx> Cc: Milan Broz <gmazyland@xxxxxxxxx> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> --- This is an alternative approach to Pascal's [0]: instead of instantiating a separate cipher to deal with the tail, invoke the same ECB skcipher used for the bulk of the data. [0] https://lore.kernel.org/linux-crypto/1565245094-8584-1-git-send-email-pvanleeuwen@xxxxxxxxxxxxxx/ crypto/xts.c | 148 +++++++++++++++++--- 1 file changed, 130 insertions(+), 18 deletions(-) diff --git a/crypto/xts.c b/crypto/xts.c index 11211003db7e..fc9edc6eb11e 100644 --- a/crypto/xts.c +++ b/crypto/xts.c @@ -34,6 +34,7 @@ struct xts_instance_ctx { struct rctx { le128 t; + struct scatterlist sg[2]; struct skcipher_request subreq; }; @@ -84,10 +85,11 @@ static int setkey(struct crypto_skcipher *parent, const u8 *key, * mutliple calls to the 'ecb(..)' instance, which usually would be slower than * just doing the gf128mul_x_ble() calls again. */ -static int xor_tweak(struct skcipher_request *req, bool second_pass) +static int xor_tweak(struct skcipher_request *req, bool second_pass, bool enc) { struct rctx *rctx = skcipher_request_ctx(req); struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); + const bool cts = (req->cryptlen % XTS_BLOCK_SIZE); const int bs = XTS_BLOCK_SIZE; struct skcipher_walk w; le128 t = rctx->t; @@ -109,6 +111,20 @@ static int xor_tweak(struct skcipher_request *req, bool second_pass) wdst = w.dst.virt.addr; do { + if (unlikely(cts) && + w.total - w.nbytes + avail < 2 * XTS_BLOCK_SIZE) { + if (!enc) { + if (second_pass) + rctx->t = t; + gf128mul_x_ble(&t, &t); + } + le128_xor(wdst, &t, wsrc); + if (enc && second_pass) + gf128mul_x_ble(&rctx->t, &t); + skcipher_walk_done(&w, avail - bs); + return 0; + } + le128_xor(wdst++, &t, wsrc++); gf128mul_x_ble(&t, &t); } while ((avail -= bs) >= bs); @@ -119,17 +135,70 @@ static int xor_tweak(struct skcipher_request *req, bool second_pass) return err; } -static int xor_tweak_pre(struct skcipher_request *req) +static int xor_tweak_pre(struct skcipher_request *req, bool enc) { - return xor_tweak(req, false); + return xor_tweak(req, false, enc); } -static int xor_tweak_post(struct skcipher_request *req) +static int xor_tweak_post(struct skcipher_request *req, bool enc) { - return xor_tweak(req, true); + return xor_tweak(req, true, enc); } -static void crypt_done(struct crypto_async_request *areq, int err) +static void cts_done(struct crypto_async_request *areq, int err) +{ + struct skcipher_request *req = areq->data; + le128 b; + + if (!err) { + struct rctx *rctx = skcipher_request_ctx(req); + + scatterwalk_map_and_copy(&b, rctx->sg, 0, XTS_BLOCK_SIZE, 0); + le128_xor(&b, &rctx->t, &b); + scatterwalk_map_and_copy(&b, rctx->sg, 0, XTS_BLOCK_SIZE, 1); + } + + skcipher_request_complete(req, err); +} + +static int cts_final(struct skcipher_request *req, + int (*crypt)(struct skcipher_request *req)) +{ + struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req)); + int offset = req->cryptlen & ~(XTS_BLOCK_SIZE - 1); + struct rctx *rctx = skcipher_request_ctx(req); + struct skcipher_request *subreq = &rctx->subreq; + int tail = req->cryptlen % XTS_BLOCK_SIZE; + struct scatterlist *sg; + le128 b[2]; + int err; + + sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - XTS_BLOCK_SIZE); + + scatterwalk_map_and_copy(b, sg, 0, XTS_BLOCK_SIZE, 0); + memcpy(b + 1, b, tail); + scatterwalk_map_and_copy(b, req->src, offset, tail, 0); + + le128_xor(b, &rctx->t, b); + + scatterwalk_map_and_copy(b, sg, 0, XTS_BLOCK_SIZE + tail, 1); + + skcipher_request_set_tfm(subreq, ctx->child); + skcipher_request_set_callback(subreq, req->base.flags, cts_done, req); + skcipher_request_set_crypt(subreq, sg, sg, XTS_BLOCK_SIZE, NULL); + + err = crypt(subreq); + if (err) + return err; + + scatterwalk_map_and_copy(b, sg, 0, XTS_BLOCK_SIZE, 0); + le128_xor(b, &rctx->t, b); + scatterwalk_map_and_copy(b, sg, 0, XTS_BLOCK_SIZE, 1); + + return 0; +} + +static void encrypt_done(struct crypto_async_request *areq, int err) { struct skcipher_request *req = areq->data; @@ -137,47 +206,90 @@ static void crypt_done(struct crypto_async_request *areq, int err) struct rctx *rctx = skcipher_request_ctx(req); rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP; - err = xor_tweak_post(req); + err = xor_tweak_post(req, true); + + if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) { + err = cts_final(req, crypto_skcipher_encrypt); + if (err == -EINPROGRESS) + return; + } } skcipher_request_complete(req, err); } -static void init_crypt(struct skcipher_request *req) +static void decrypt_done(struct crypto_async_request *areq, int err) +{ + struct skcipher_request *req = areq->data; + + if (!err) { + struct rctx *rctx = skcipher_request_ctx(req); + + rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP; + err = xor_tweak_post(req, false); + + if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) { + err = cts_final(req, crypto_skcipher_decrypt); + if (err == -EINPROGRESS) + return; + } + } + + skcipher_request_complete(req, err); +} + +static int init_crypt(struct skcipher_request *req, crypto_completion_t compl) { struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req)); struct rctx *rctx = skcipher_request_ctx(req); struct skcipher_request *subreq = &rctx->subreq; + if (req->cryptlen < XTS_BLOCK_SIZE) + return -EINVAL; + skcipher_request_set_tfm(subreq, ctx->child); - skcipher_request_set_callback(subreq, req->base.flags, crypt_done, req); + skcipher_request_set_callback(subreq, req->base.flags, compl, req); skcipher_request_set_crypt(subreq, req->dst, req->dst, - req->cryptlen, NULL); + req->cryptlen & ~(XTS_BLOCK_SIZE - 1), NULL); /* calculate first value of T */ crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv); + + return 0; } static int encrypt(struct skcipher_request *req) { struct rctx *rctx = skcipher_request_ctx(req); struct skcipher_request *subreq = &rctx->subreq; + int err; - init_crypt(req); - return xor_tweak_pre(req) ?: - crypto_skcipher_encrypt(subreq) ?: - xor_tweak_post(req); + err = init_crypt(req, encrypt_done) ?: + xor_tweak_pre(req, true) ?: + crypto_skcipher_encrypt(subreq) ?: + xor_tweak_post(req, true); + + if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0)) + return err; + + return cts_final(req, crypto_skcipher_encrypt); } static int decrypt(struct skcipher_request *req) { struct rctx *rctx = skcipher_request_ctx(req); struct skcipher_request *subreq = &rctx->subreq; + int err; + + err = init_crypt(req, decrypt_done) ?: + xor_tweak_pre(req, false) ?: + crypto_skcipher_decrypt(subreq) ?: + xor_tweak_post(req, false); + + if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0)) + return err; - init_crypt(req); - return xor_tweak_pre(req) ?: - crypto_skcipher_decrypt(subreq) ?: - xor_tweak_post(req); + return cts_final(req, crypto_skcipher_decrypt); } static int init_tfm(struct crypto_skcipher *tfm) -- 2.17.1
