crypto: arm64/aes-xctr - Add accelerated implementation of XCTR

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.pdfSigned-off-by: Nathan Huckleberry <nhuck@google.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/arm64/crypto/Kconfig

@@ -96,13 +96,13 @@ 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

arch/arm64/crypto/aes-glue.c

@@ -34,10 +34,11 @@
 #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
@@ -50,16 +51,18 @@ 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)");
@@ -89,6 +92,9 @@ 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[]);
 
+asmlinkage void aes_xctr_encrypt(u8 out[], u8 const in[], u32 const rk[],
+				 int rounds, int bytes, u8 ctr[], 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);
@@ -442,6 +448,44 @@ 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];
+
+		if (unlikely(nbytes < AES_BLOCK_SIZE))
+			src = dst = memcpy(buf + sizeof(buf) - nbytes,
+					   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, byte_ctr);
+		kernel_neon_end();
+
+		if (unlikely(nbytes < AES_BLOCK_SIZE))
+			memcpy(walk.dst.virt.addr,
+			       buf + sizeof(buf) - nbytes, nbytes);
+		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);
@@ -669,6 +713,22 @@ 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)",

arch/arm64/crypto/aes-modes.S

@@ -318,38 +318,60 @@ AES_FUNC_END(aes_cbc_cts_decrypt)
 	.byte		0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
 	.previous
 
-
 	/*
-	 * aes_ctr_encrypt(u8 out[], u8 const in[], u8 const rk[], int rounds,
-	 *		   int bytes, u8 ctr[])
+	 * This macro generates the code for CTR and XCTR mode.
 	 */
-
-AES_FUNC_START(aes_ctr_encrypt)
+.macro ctr_encrypt xctr
 	stp		x29, x30, [sp, #-16]!
 	mov		x29, sp
 
 	enc_prepare	w3, x2, x12
 	ld1		{vctr.16b}, [x5]
 
+	.if \xctr
+		umov		x12, vctr.d[0]
+		lsr		w11, w6, #4
+	.else
 		umov		x12, vctr.d[1] /* keep swabbed ctr in reg */
 		rev		x12, x12
+	.endif
 
-.LctrloopNx:
+.LctrloopNx\xctr:
 	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
-	adds		x12, x12, x7
 
+	.if \xctr
+		add		x11, x11, x7
+	.else
+		adds		x12, x12, x7
+	.endif
 	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		)
+	.if \xctr
+		sub		x6, x11, #MAX_STRIDE - 1
+		sub		x7, x11, #MAX_STRIDE - 2
+		sub		x8, x11, #MAX_STRIDE - 3
+		sub		x9, x11, #MAX_STRIDE - 4
+ST5(		sub		x10, x11, #MAX_STRIDE - 5	)
+		eor		x6, x6, x12
+		eor		x7, x7, x12
+		eor		x8, x8, x12
+		eor		x9, x9, x12
+ST5(		eor		x10, x10, x12			)
+		mov		v0.d[0], x6
+		mov		v1.d[0], x7
+		mov		v2.d[0], x8
+		mov		v3.d[0], x9
+ST5(		mov		v4.d[0], x10			)
+	.else
 		bcs		0f
-
 		.subsection	1
 		/* apply carry to outgoing counter */
 0:		umov		x8, vctr.d[0]
@@ -390,7 +412,8 @@ ST5(	sub		x10, x12, #MAX_STRIDE - 4	)
 ST5(		rev		x10, x10			)
 		mov		v3.d[1], x9
 ST5(		mov		v4.d[1], x10			)
-	tbnz		w4, #31, .Lctrtail
+	.endif
+	tbnz		w4, #31, .Lctrtail\xctr
 	ld1		{v5.16b-v7.16b}, [x1], #48
 ST4(	bl		aes_encrypt_block4x		)
 ST5(	bl		aes_encrypt_block5x		)
@@ -403,16 +426,17 @@ ST5(	ld1		{v5.16b-v6.16b}, [x1], #32	)
 ST5(	eor		v4.16b, v6.16b, v4.16b		)
 	st1		{v0.16b-v3.16b}, [x0], #64
 ST5(	st1		{v4.16b}, [x0], #16		)
-	cbz		w4, .Lctrout
-	b		.LctrloopNx
+	cbz		w4, .Lctrout\xctr
+	b		.LctrloopNx\xctr
 
-.Lctrout:
+.Lctrout\xctr:
+	.if !\xctr
 		st1		{vctr.16b}, [x5] /* return next CTR value */
+	.endif
 	ldp		x29, x30, [sp], #16
 	ret
 
-.Lctrtail:
-	/* XOR up to MAX_STRIDE * 16 - 1 bytes of in/output with v0 ... v3/v4 */
+.Lctrtail\xctr:
 	mov		x16, #16
 	ands		x6, x4, #0xf
 	csel		x13, x6, x16, ne
@@ -427,7 +451,7 @@ ST5(	csel		x14, x16, xzr, gt		)
 
 	adr_l		x12, .Lcts_permute_table
 	add		x12, x12, x13
-	ble		.Lctrtail1x
+	ble		.Lctrtail1x\xctr
 
 ST5(	ld1		{v5.16b}, [x1], x14		)
 	ld1		{v6.16b}, [x1], x15
@@ -459,9 +483,9 @@ ST5(	st1		{v5.16b}, [x0], x14		)
 	add		x13, x13, x0
 	st1		{v9.16b}, [x13]		// overlapping stores
 	st1		{v8.16b}, [x0]
-	b		.Lctrout
+	b		.Lctrout\xctr
 
-.Lctrtail1x:
+.Lctrtail1x\xctr:
 	sub		x7, x6, #16
 	csel		x6, x6, x7, eq
 	add		x1, x1, x6
@@ -476,9 +500,27 @@ ST5(	mov		v3.16b, v4.16b			)
 	eor		v5.16b, v5.16b, v3.16b
 	bif		v5.16b, v6.16b, v11.16b
 	st1		{v5.16b}, [x0]
-	b		.Lctrout
+	b		.Lctrout\xctr
+.endm
+
+	/*
+	 * aes_ctr_encrypt(u8 out[], u8 const in[], u8 const rk[], int rounds,
+	 *		   int bytes, u8 ctr[])
+	 */
+
+AES_FUNC_START(aes_ctr_encrypt)
+	ctr_encrypt 0
 AES_FUNC_END(aes_ctr_encrypt)
 
+	/*
+	 * aes_xctr_encrypt(u8 out[], u8 const in[], u8 const rk[], int rounds,
+	 *		   int bytes, u8 const iv[], int byte_ctr)
+	 */
+
+AES_FUNC_START(aes_xctr_encrypt)
+	ctr_encrypt 1
+AES_FUNC_END(aes_xctr_encrypt)
+
 
 	/*
 	 * aes_xts_encrypt(u8 out[], u8 const in[], u8 const rk1[], int rounds,