Subject: [RFC PATCH 5/7] crypto: arm64/aes-xctr: Add accelerated implementation of XCTR

From: Nathan Huckleberry <[email-masked]>
Date: Mon, 24 Jan 2022 19:44:20 -0600

Add hardware accelerated version of XCTR for ARM64 CPUs with ARMv8
Crypto Extension support.  This XCTR implementation is based on the CTR
implementation in aes-modes.S.

More information on XCTR can be found in
the HCTR2 paper: Length-preserving encryption with HCTR2:
https://eprint.iacr.org/2021/1441.pdf

Signed-off-by: Nathan Huckleberry <[email-masked]>
---
 arch/arm64/crypto/Kconfig     |   4 +-
 arch/arm64/crypto/aes-glue.c  |  70 ++++++++++++++++++-
 arch/arm64/crypto/aes-modes.S | 128 ++++++++++++++++++++++++++++++++++
 3 files changed, 198 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/crypto/Kconfig b/arch/arm64/crypto/Kconfig
index addfa413650b..cab469e279ec 100644
--- a/arch/arm64/crypto/Kconfig
+++ b/arch/arm64/crypto/Kconfig
@@ -84,13 +84,13 @@ config CRYPTO_AES_ARM64_CE_CCM
 	select CRYPTO_LIB_AES
 
 config CRYPTO_AES_ARM64_CE_BLK
-	tristate "AES in ECB/CBC/CTR/XTS modes using ARMv8 Crypto Extensions"
+	tristate "AES in ECB/CBC/CTR/XTS/XCTR modes using ARMv8 Crypto Extensions"
 	depends on KERNEL_MODE_NEON
 	select CRYPTO_SKCIPHER
 	select CRYPTO_AES_ARM64_CE
 
 config CRYPTO_AES_ARM64_NEON_BLK
-	tristate "AES in ECB/CBC/CTR/XTS modes using NEON instructions"
+	tristate "AES in ECB/CBC/CTR/XTS/XCTR modes using NEON instructions"
 	depends on KERNEL_MODE_NEON
 	select CRYPTO_SKCIPHER
 	select CRYPTO_LIB_AES
diff --git a/arch/arm64/crypto/aes-glue.c b/arch/arm64/crypto/aes-glue.c
index 30b7cc6a7079..377f8d8369fb 100644
--- a/arch/arm64/crypto/aes-glue.c
+++ b/arch/arm64/crypto/aes-glue.c
@@ -35,10 +35,11 @@
 #define aes_essiv_cbc_encrypt	ce_aes_essiv_cbc_encrypt
 #define aes_essiv_cbc_decrypt	ce_aes_essiv_cbc_decrypt
 #define aes_ctr_encrypt		ce_aes_ctr_encrypt
+#define aes_xctr_encrypt	ce_aes_xctr_encrypt
 #define aes_xts_encrypt		ce_aes_xts_encrypt
 #define aes_xts_decrypt		ce_aes_xts_decrypt
 #define aes_mac_update		ce_aes_mac_update
-MODULE_DESCRIPTION("AES-ECB/CBC/CTR/XTS using ARMv8 Crypto Extensions");
+MODULE_DESCRIPTION("AES-ECB/CBC/CTR/XTS/XCTR using ARMv8 Crypto Extensions");
 #else
 #define MODE			"neon"
 #define PRIO			200
@@ -52,16 +53,18 @@ MODULE_DESCRIPTION("AES-ECB/CBC/CTR/XTS using ARMv8 Crypto Extensions");
 #define aes_essiv_cbc_encrypt	neon_aes_essiv_cbc_encrypt
 #define aes_essiv_cbc_decrypt	neon_aes_essiv_cbc_decrypt
 #define aes_ctr_encrypt		neon_aes_ctr_encrypt
+#define aes_xctr_encrypt	neon_aes_xctr_encrypt
 #define aes_xts_encrypt		neon_aes_xts_encrypt
 #define aes_xts_decrypt		neon_aes_xts_decrypt
 #define aes_mac_update		neon_aes_mac_update
-MODULE_DESCRIPTION("AES-ECB/CBC/CTR/XTS using ARMv8 NEON");
+MODULE_DESCRIPTION("AES-ECB/CBC/CTR/XTS/XCTR using ARMv8 NEON");
 #endif
 #if defined(USE_V8_CRYPTO_EXTENSIONS) || !IS_ENABLED(CONFIG_CRYPTO_AES_ARM64_BS)
 MODULE_ALIAS_CRYPTO("ecb(aes)");
 MODULE_ALIAS_CRYPTO("cbc(aes)");
 MODULE_ALIAS_CRYPTO("ctr(aes)");
 MODULE_ALIAS_CRYPTO("xts(aes)");
+MODULE_ALIAS_CRYPTO("xctr(aes)");
 #endif
 MODULE_ALIAS_CRYPTO("cts(cbc(aes))");
 MODULE_ALIAS_CRYPTO("essiv(cbc(aes),sha256)");
@@ -91,6 +94,10 @@ asmlinkage void aes_cbc_cts_decrypt(u8 out[], u8 const in[], u32 const rk[],
 asmlinkage void aes_ctr_encrypt(u8 out[], u8 const in[], u32 const rk[],
 				int rounds, int bytes, u8 ctr[], u8 finalbuf[]);
 
+asmlinkage void aes_xctr_encrypt(u8 out[], u8 const in[], u32 const rk[],
+				 int rounds, int bytes, u8 ctr[], u8 finalbuf[],
+				 int byte_ctr);
+
 asmlinkage void aes_xts_encrypt(u8 out[], u8 const in[], u32 const rk1[],
 				int rounds, int bytes, u32 const rk2[], u8 iv[],
 				int first);
@@ -444,6 +451,49 @@ static int __maybe_unused essiv_cbc_decrypt(struct skcipher_request *req)
 	return err ?: cbc_decrypt_walk(req, &walk);
 }
 
+static int __maybe_unused xctr_encrypt(struct skcipher_request *req)
+{
+	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+	struct crypto_aes_ctx *ctx = crypto_skcipher_ctx(tfm);
+	int err, rounds = 6 + ctx->key_length / 4;
+	struct skcipher_walk walk;
+	unsigned int byte_ctr = 0;
+
+	err = skcipher_walk_virt(&walk, req, false);
+
+	while (walk.nbytes > 0) {
+		const u8 *src = walk.src.virt.addr;
+		unsigned int nbytes = walk.nbytes;
+		u8 *dst = walk.dst.virt.addr;
+		u8 buf[AES_BLOCK_SIZE];
+		unsigned int tail;
+
+		if (unlikely(nbytes < AES_BLOCK_SIZE))
+			src = memcpy(buf, src, nbytes);
+		else if (nbytes < walk.total)
+			nbytes &= ~(AES_BLOCK_SIZE - 1);
+
+		kernel_neon_begin();
+		aes_xctr_encrypt(dst, src, ctx->key_enc, rounds, nbytes,
+						 walk.iv, buf, byte_ctr);
+		kernel_neon_end();
+
+		tail = nbytes % (STRIDE * AES_BLOCK_SIZE);
+		if (tail > 0 && tail < AES_BLOCK_SIZE)
+			/*
+			 * The final partial block could not be returned using
+			 * an overlapping store, so it was passed via buf[]
+			 * instead.
+			 */
+			memcpy(dst + nbytes - tail, buf, tail);
+		byte_ctr += nbytes;
+
+		err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
+	}
+
+	return err;
+}
+
 static int __maybe_unused ctr_encrypt(struct skcipher_request *req)
 {
 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
@@ -676,6 +726,22 @@ static struct skcipher_alg aes_algs[] = { {
 	.setkey		= skcipher_aes_setkey,
 	.encrypt	= ctr_encrypt,
 	.decrypt	= ctr_encrypt,
+}, {
+	.base = {
+		.cra_name		= "xctr(aes)",
+		.cra_driver_name	= "xctr-aes-" MODE,
+		.cra_priority		= PRIO,
+		.cra_blocksize		= 1,
+		.cra_ctxsize		= sizeof(struct crypto_aes_ctx),
+		.cra_module		= THIS_MODULE,
+	},
+	.min_keysize	= AES_MIN_KEY_SIZE,
+	.max_keysize	= AES_MAX_KEY_SIZE,
+	.ivsize		= AES_BLOCK_SIZE,
+	.chunksize	= AES_BLOCK_SIZE,
+	.setkey		= skcipher_aes_setkey,
+	.encrypt	= xctr_encrypt,
+	.decrypt	= xctr_encrypt,
 }, {
 	.base = {
 		.cra_name		= "xts(aes)",
diff --git a/arch/arm64/crypto/aes-modes.S b/arch/arm64/crypto/aes-modes.S
index ff01f0167ba2..7128907f8190 100644
--- a/arch/arm64/crypto/aes-modes.S
+++ b/arch/arm64/crypto/aes-modes.S
@@ -471,6 +471,134 @@ ST5(	mov		v3.16b, v4.16b			)
 	b		.Lctrout
 AES_FUNC_END(aes_ctr_encrypt)
 
+    /*
+	 * aes_xctr_encrypt(u8 out[], u8 const in[], u8 const rk[], int rounds,
+	 *		   int bytes, u8 const ctr[], u8 finalbuf[], int byte_ctr)
+	 */
+
+AES_FUNC_START(aes_xctr_encrypt)
+	stp		x29, x30, [sp, #-16]!
+	mov		x29, sp
+
+	enc_prepare	w3, x2, x12
+	ld1		{vctr.16b}, [x5]
+
+	umov		x12, vctr.d[0]		/* keep ctr in reg */
+	lsr		x7, x7, #4
+	add		x11, x7, #1
+
+.LxctrloopNx:
+	add		w7, w4, #15
+	sub		w4, w4, #MAX_STRIDE << 4
+	lsr		w7, w7, #4
+	mov		w8, #MAX_STRIDE
+	cmp		w7, w8
+	csel		w7, w7, w8, lt
+	add		x11, x11, x7
+
+	mov		v0.16b, vctr.16b
+	mov		v1.16b, vctr.16b
+	mov		v2.16b, vctr.16b
+	mov		v3.16b, vctr.16b
+ST5(	mov		v4.16b, vctr.16b		)
+
+	sub		x7, x11, #MAX_STRIDE
+	eor		x7, x12, x7
+	ins		v0.d[0], x7
+	sub		x7, x11, #MAX_STRIDE - 1
+	sub		x8, x11, #MAX_STRIDE - 2
+	eor		x7, x7, x12
+	sub		x9, x11, #MAX_STRIDE - 3
+	mov		v1.d[0], x7
+	eor		x8, x8, x12
+	eor		x9, x9, x12
+ST5(	sub		x10, x11, #MAX_STRIDE - 4)
+	mov		v2.d[0], x8
+	eor		x10, x10, x12
+	mov		v3.d[0], x9
+ST5(	mov		v4.d[0], x10			)
+	tbnz		w4, #31, .Lxctrtail
+	ld1		{v5.16b-v7.16b}, [x1], #48
+ST4(	bl		aes_encrypt_block4x		)
+ST5(	bl		aes_encrypt_block5x		)
+	eor		v0.16b, v5.16b, v0.16b
+ST4(	ld1		{v5.16b}, [x1], #16		)
+	eor		v1.16b, v6.16b, v1.16b
+ST5(	ld1		{v5.16b-v6.16b}, [x1], #32	)
+	eor		v2.16b, v7.16b, v2.16b
+	eor		v3.16b, v5.16b, v3.16b
+ST5(	eor		v4.16b, v6.16b, v4.16b		)
+	st1		{v0.16b-v3.16b}, [x0], #64
+ST5(	st1		{v4.16b}, [x0], #16		)
+	cbz		w4, .Lxctrout
+	b		.LxctrloopNx
+
+.Lxctrout:
+	ldp		x29, x30, [sp], #16
+	ret
+
+.Lxctrtail:
+	/* XOR up to MAX_STRIDE * 16 - 1 bytes of in/output with v0 ... v3/v4 */
+	mov		x17, #16
+	ands		x13, x4, #0xf
+	csel		x13, x13, x17, ne
+
+ST5(	cmp		w4, #64 - (MAX_STRIDE << 4))
+ST5(	csel		x14, x17, xzr, gt		)
+	cmp		w4, #48 - (MAX_STRIDE << 4)
+	csel		x15, x17, xzr, gt
+	cmp		w4, #32 - (MAX_STRIDE << 4)
+	csel		x16, x17, xzr, gt
+	cmp		w4, #16 - (MAX_STRIDE << 4)
+	ble		.Lxctrtail1x
+
+ST5(	mov		v4.d[0], x10			)
+
+	adr_l		x12, .Lcts_permute_table
+	add		x12, x12, x13
+
+ST5(	ld1		{v5.16b}, [x1], x14		)
+	ld1		{v6.16b}, [x1], x15
+	ld1		{v7.16b}, [x1], x16
+
+ST4(	bl		aes_encrypt_block4x		)
+ST5(	bl		aes_encrypt_block5x		)
+
+	ld1		{v8.16b}, [x1], x13
+	ld1		{v9.16b}, [x1]
+	ld1		{v10.16b}, [x12]
+
+ST4(	eor		v6.16b, v6.16b, v0.16b		)
+ST4(	eor		v7.16b, v7.16b, v1.16b		)
+ST4(	tbl		v3.16b, {v3.16b}, v10.16b	)
+ST4(	eor		v8.16b, v8.16b, v2.16b		)
+ST4(	eor		v9.16b, v9.16b, v3.16b		)
+
+ST5(	eor		v5.16b, v5.16b, v0.16b		)
+ST5(	eor		v6.16b, v6.16b, v1.16b		)
+ST5(	tbl		v4.16b, {v4.16b}, v10.16b	)
+ST5(	eor		v7.16b, v7.16b, v2.16b		)
+ST5(	eor		v8.16b, v8.16b, v3.16b		)
+ST5(	eor		v9.16b, v9.16b, v4.16b		)
+
+ST5(	st1		{v5.16b}, [x0], x14		)
+	st1		{v6.16b}, [x0], x15
+	st1		{v7.16b}, [x0], x16
+	add		x13, x13, x0
+	st1		{v9.16b}, [x13]		// overlapping stores
+	st1		{v8.16b}, [x0]
+	b		.Lxctrout
+
+.Lxctrtail1x:
+	csel		x0, x0, x6, eq		// use finalbuf if less than a full block
+	ld1		{v5.16b}, [x1]
+ST5(	mov		v3.16b, v4.16b			)
+	encrypt_block	v3, w3, x2, x8, w7
+	eor		v5.16b, v5.16b, v3.16b
+	st1		{v5.16b}, [x0]
+	b		.Lxctrout
+AES_FUNC_END(aes_xctr_encrypt)
+
 
 	/*
 	 * aes_xts_encrypt(u8 out[], u8 const in[], u8 const rk1[], int rounds,
-- 
2.35.0.rc0.227.g00780c9af4-goog

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