From 2ed8b79098cf76287c519d781a14c7983ab7e4f7 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Tue, 3 Sep 2019 09:43:36 -0700 Subject: [PATCH] crypto: arm/aes-neonbs - implement ciphertext stealing for XTS Update the AES-XTS implementation based on NEON instructions so that it can deal with inputs whose size is not a multiple of the cipher block size. This is part of the original XTS specification, but was never implemented before in the Linux kernel. Signed-off-by: Ard Biesheuvel Signed-off-by: Herbert Xu --- arch/arm/crypto/aes-neonbs-core.S | 16 +++++-- arch/arm/crypto/aes-neonbs-glue.c | 69 +++++++++++++++++++++++++++---- 2 files changed, 72 insertions(+), 13 deletions(-) diff --git a/arch/arm/crypto/aes-neonbs-core.S b/arch/arm/crypto/aes-neonbs-core.S index bb75918e4984..cfaed4e67535 100644 --- a/arch/arm/crypto/aes-neonbs-core.S +++ b/arch/arm/crypto/aes-neonbs-core.S @@ -889,9 +889,9 @@ ENDPROC(aesbs_ctr_encrypt) /* * aesbs_xts_encrypt(u8 out[], u8 const in[], u8 const rk[], int rounds, - * int blocks, u8 iv[]) + * int blocks, u8 iv[], int reorder_last_tweak) * aesbs_xts_decrypt(u8 out[], u8 const in[], u8 const rk[], int rounds, - * int blocks, u8 iv[]) + * int blocks, u8 iv[], int reorder_last_tweak) */ __xts_prepare8: vld1.8 {q14}, [r7] // load iv @@ -944,17 +944,25 @@ __xts_prepare8: vld1.8 {q7}, [r1]! next_tweak q14, q12, q15, q13 - veor q7, q7, q12 +THUMB( itt le ) + W(cmple) r8, #0 + ble 1f +0: veor q7, q7, q12 vst1.8 {q12}, [r4, :128] -0: vst1.8 {q14}, [r7] // store next iv + vst1.8 {q14}, [r7] // store next iv bx lr + +1: vswp q12, q14 + b 0b ENDPROC(__xts_prepare8) .macro __xts_crypt, do8, o0, o1, o2, o3, o4, o5, o6, o7 push {r4-r8, lr} mov r5, sp // preserve sp ldrd r6, r7, [sp, #24] // get blocks and iv args + ldr r8, [sp, #32] // reorder final tweak? + rsb r8, r8, #1 sub ip, sp, #128 // make room for 8x tweak bic ip, ip, #0xf // align sp to 16 bytes mov sp, ip diff --git a/arch/arm/crypto/aes-neonbs-glue.c b/arch/arm/crypto/aes-neonbs-glue.c index 9000d0796d5e..e85839a8aaeb 100644 --- a/arch/arm/crypto/aes-neonbs-glue.c +++ b/arch/arm/crypto/aes-neonbs-glue.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include @@ -37,9 +38,9 @@ asmlinkage void aesbs_ctr_encrypt(u8 out[], u8 const in[], u8 const rk[], int rounds, int blocks, u8 ctr[], u8 final[]); asmlinkage void aesbs_xts_encrypt(u8 out[], u8 const in[], u8 const rk[], - int rounds, int blocks, u8 iv[]); + int rounds, int blocks, u8 iv[], int); asmlinkage void aesbs_xts_decrypt(u8 out[], u8 const in[], u8 const rk[], - int rounds, int blocks, u8 iv[]); + int rounds, int blocks, u8 iv[], int); struct aesbs_ctx { int rounds; @@ -53,6 +54,7 @@ struct aesbs_cbc_ctx { struct aesbs_xts_ctx { struct aesbs_ctx key; + struct crypto_cipher *cts_tfm; struct crypto_cipher *tweak_tfm; }; @@ -291,6 +293,9 @@ static int aesbs_xts_setkey(struct crypto_skcipher *tfm, const u8 *in_key, return err; key_len /= 2; + err = crypto_cipher_setkey(ctx->cts_tfm, in_key, key_len); + if (err) + return err; err = crypto_cipher_setkey(ctx->tweak_tfm, in_key + key_len, key_len); if (err) return err; @@ -302,7 +307,13 @@ static int xts_init(struct crypto_tfm *tfm) { struct aesbs_xts_ctx *ctx = crypto_tfm_ctx(tfm); + ctx->cts_tfm = crypto_alloc_cipher("aes", 0, 0); + if (IS_ERR(ctx->cts_tfm)) + return PTR_ERR(ctx->cts_tfm); + ctx->tweak_tfm = crypto_alloc_cipher("aes", 0, 0); + if (IS_ERR(ctx->tweak_tfm)) + crypto_free_cipher(ctx->cts_tfm); return PTR_ERR_OR_ZERO(ctx->tweak_tfm); } @@ -312,17 +323,34 @@ static void xts_exit(struct crypto_tfm *tfm) struct aesbs_xts_ctx *ctx = crypto_tfm_ctx(tfm); crypto_free_cipher(ctx->tweak_tfm); + crypto_free_cipher(ctx->cts_tfm); } -static int __xts_crypt(struct skcipher_request *req, +static int __xts_crypt(struct skcipher_request *req, bool encrypt, void (*fn)(u8 out[], u8 const in[], u8 const rk[], - int rounds, int blocks, u8 iv[])) + int rounds, int blocks, u8 iv[], int)) { struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); struct aesbs_xts_ctx *ctx = crypto_skcipher_ctx(tfm); + int tail = req->cryptlen % AES_BLOCK_SIZE; + struct skcipher_request subreq; + u8 buf[2 * AES_BLOCK_SIZE]; struct skcipher_walk walk; int err; + if (req->cryptlen < AES_BLOCK_SIZE) + return -EINVAL; + + if (unlikely(tail)) { + skcipher_request_set_tfm(&subreq, tfm); + skcipher_request_set_callback(&subreq, + skcipher_request_flags(req), + NULL, NULL); + skcipher_request_set_crypt(&subreq, req->src, req->dst, + req->cryptlen - tail, req->iv); + req = &subreq; + } + err = skcipher_walk_virt(&walk, req, true); if (err) return err; @@ -331,30 +359,53 @@ static int __xts_crypt(struct skcipher_request *req, while (walk.nbytes >= AES_BLOCK_SIZE) { unsigned int blocks = walk.nbytes / AES_BLOCK_SIZE; + int reorder_last_tweak = !encrypt && tail > 0; - if (walk.nbytes < walk.total) + if (walk.nbytes < walk.total) { blocks = round_down(blocks, walk.stride / AES_BLOCK_SIZE); + reorder_last_tweak = 0; + } kernel_neon_begin(); fn(walk.dst.virt.addr, walk.src.virt.addr, ctx->key.rk, - ctx->key.rounds, blocks, walk.iv); + ctx->key.rounds, blocks, walk.iv, reorder_last_tweak); kernel_neon_end(); err = skcipher_walk_done(&walk, walk.nbytes - blocks * AES_BLOCK_SIZE); } - return err; + if (err || likely(!tail)) + return err; + + /* handle ciphertext stealing */ + scatterwalk_map_and_copy(buf, req->dst, req->cryptlen - AES_BLOCK_SIZE, + AES_BLOCK_SIZE, 0); + memcpy(buf + AES_BLOCK_SIZE, buf, tail); + scatterwalk_map_and_copy(buf, req->src, req->cryptlen, tail, 0); + + crypto_xor(buf, req->iv, AES_BLOCK_SIZE); + + if (encrypt) + crypto_cipher_encrypt_one(ctx->cts_tfm, buf, buf); + else + crypto_cipher_decrypt_one(ctx->cts_tfm, buf, buf); + + crypto_xor(buf, req->iv, AES_BLOCK_SIZE); + + scatterwalk_map_and_copy(buf, req->dst, req->cryptlen - AES_BLOCK_SIZE, + AES_BLOCK_SIZE + tail, 1); + return 0; } static int xts_encrypt(struct skcipher_request *req) { - return __xts_crypt(req, aesbs_xts_encrypt); + return __xts_crypt(req, true, aesbs_xts_encrypt); } static int xts_decrypt(struct skcipher_request *req) { - return __xts_crypt(req, aesbs_xts_decrypt); + return __xts_crypt(req, false, aesbs_xts_decrypt); } static struct skcipher_alg aes_algs[] = { {