crypto: arm/aes-ce - implement ciphertext stealing for CBC

Instead of relying on the CTS template to wrap the accelerated CBC
skcipher, implement the ciphertext stealing part directly.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/arm/crypto/aes-ce-core.S

@@ -284,6 +284,91 @@ ENTRY(ce_aes_cbc_decrypt)
 	pop		{r4-r6, pc}
 ENDPROC(ce_aes_cbc_decrypt)
 
+
+	/*
+	 * ce_aes_cbc_cts_encrypt(u8 out[], u8 const in[], u32 const rk[],
+	 *			  int rounds, int bytes, u8 const iv[])
+	 * ce_aes_cbc_cts_decrypt(u8 out[], u8 const in[], u32 const rk[],
+	 *			  int rounds, int bytes, u8 const iv[])
+	 */
+
+ENTRY(ce_aes_cbc_cts_encrypt)
+	push		{r4-r6, lr}
+	ldrd		r4, r5, [sp, #16]
+
+	movw		ip, :lower16:.Lcts_permute_table
+	movt		ip, :upper16:.Lcts_permute_table
+	sub		r4, r4, #16
+	add		lr, ip, #32
+	add		ip, ip, r4
+	sub		lr, lr, r4
+	vld1.8		{q5}, [ip]
+	vld1.8		{q6}, [lr]
+
+	add		ip, r1, r4
+	vld1.8		{q0}, [r1]			@ overlapping loads
+	vld1.8		{q3}, [ip]
+
+	vld1.8		{q1}, [r5]			@ get iv
+	prepare_key	r2, r3
+
+	veor		q0, q0, q1			@ xor with iv
+	bl		aes_encrypt
+
+	vtbl.8		d4, {d0-d1}, d10
+	vtbl.8		d5, {d0-d1}, d11
+	vtbl.8		d2, {d6-d7}, d12
+	vtbl.8		d3, {d6-d7}, d13
+
+	veor		q0, q0, q1
+	bl		aes_encrypt
+
+	add		r4, r0, r4
+	vst1.8		{q2}, [r4]			@ overlapping stores
+	vst1.8		{q0}, [r0]
+
+	pop		{r4-r6, pc}
+ENDPROC(ce_aes_cbc_cts_encrypt)
+
+ENTRY(ce_aes_cbc_cts_decrypt)
+	push		{r4-r6, lr}
+	ldrd		r4, r5, [sp, #16]
+
+	movw		ip, :lower16:.Lcts_permute_table
+	movt		ip, :upper16:.Lcts_permute_table
+	sub		r4, r4, #16
+	add		lr, ip, #32
+	add		ip, ip, r4
+	sub		lr, lr, r4
+	vld1.8		{q5}, [ip]
+	vld1.8		{q6}, [lr]
+
+	add		ip, r1, r4
+	vld1.8		{q0}, [r1]			@ overlapping loads
+	vld1.8		{q1}, [ip]
+
+	vld1.8		{q3}, [r5]			@ get iv
+	prepare_key	r2, r3
+
+	bl		aes_decrypt
+
+	vtbl.8		d4, {d0-d1}, d10
+	vtbl.8		d5, {d0-d1}, d11
+	vtbx.8		d0, {d2-d3}, d12
+	vtbx.8		d1, {d2-d3}, d13
+
+	veor		q1, q1, q2
+	bl		aes_decrypt
+	veor		q0, q0, q3			@ xor with iv
+
+	add		r4, r0, r4
+	vst1.8		{q1}, [r4]			@ overlapping stores
+	vst1.8		{q0}, [r0]
+
+	pop		{r4-r6, pc}
+ENDPROC(ce_aes_cbc_cts_decrypt)
+
+
 	/*
 	 * aes_ctr_encrypt(u8 out[], u8 const in[], u32 const rk[], int rounds,
 	 *		   int blocks, u8 ctr[])

arch/arm/crypto/aes-ce-glue.c

@@ -35,6 +35,10 @@ asmlinkage void ce_aes_cbc_encrypt(u8 out[], u8 const in[], u32 const rk[],
 				   int rounds, int blocks, u8 iv[]);
 asmlinkage void ce_aes_cbc_decrypt(u8 out[], u8 const in[], u32 const rk[],
 				   int rounds, int blocks, u8 iv[]);
+asmlinkage void ce_aes_cbc_cts_encrypt(u8 out[], u8 const in[], u32 const rk[],
+				   int rounds, int bytes, u8 const iv[]);
+asmlinkage void ce_aes_cbc_cts_decrypt(u8 out[], u8 const in[], u32 const rk[],
+				   int rounds, int bytes, u8 const iv[]);
 
 asmlinkage void ce_aes_ctr_encrypt(u8 out[], u8 const in[], u32 const rk[],
 				   int rounds, int blocks, u8 ctr[]);
@@ -210,46 +214,180 @@ static int ecb_decrypt(struct skcipher_request *req)
 	return err;
 }
 
-static int cbc_encrypt(struct skcipher_request *req)
+static int cbc_encrypt_walk(struct skcipher_request *req,
+			    struct skcipher_walk *walk)
 {
 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 	struct crypto_aes_ctx *ctx = crypto_skcipher_ctx(tfm);
-	struct skcipher_walk walk;
 	unsigned int blocks;
+	int err = 0;
+
+	while ((blocks = (walk->nbytes / AES_BLOCK_SIZE))) {
+		kernel_neon_begin();
+		ce_aes_cbc_encrypt(walk->dst.virt.addr, walk->src.virt.addr,
+				   ctx->key_enc, num_rounds(ctx), blocks,
+				   walk->iv);
+		kernel_neon_end();
+		err = skcipher_walk_done(walk, walk->nbytes % AES_BLOCK_SIZE);
+	}
+	return err;
+}
+
+static int cbc_encrypt(struct skcipher_request *req)
+{
+	struct skcipher_walk walk;
 	int err;
 
 	err = skcipher_walk_virt(&walk, req, false);
+	if (err)
+		return err;
+	return cbc_encrypt_walk(req, &walk);
+}
 
-	while ((blocks = (walk.nbytes / AES_BLOCK_SIZE))) {
+static int cbc_decrypt_walk(struct skcipher_request *req,
+			    struct skcipher_walk *walk)
+{
+	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+	struct crypto_aes_ctx *ctx = crypto_skcipher_ctx(tfm);
+	unsigned int blocks;
+	int err = 0;
+
+	while ((blocks = (walk->nbytes / AES_BLOCK_SIZE))) {
 		kernel_neon_begin();
-		ce_aes_cbc_encrypt(walk.dst.virt.addr, walk.src.virt.addr,
-				   ctx->key_enc, num_rounds(ctx), blocks,
-				   walk.iv);
+		ce_aes_cbc_decrypt(walk->dst.virt.addr, walk->src.virt.addr,
+				   ctx->key_dec, num_rounds(ctx), blocks,
+				   walk->iv);
 		kernel_neon_end();
-		err = skcipher_walk_done(&walk, walk.nbytes % AES_BLOCK_SIZE);
+		err = skcipher_walk_done(walk, walk->nbytes % AES_BLOCK_SIZE);
 	}
 	return err;
 }
 
 static int cbc_decrypt(struct skcipher_request *req)
+{
+	struct skcipher_walk walk;
+	int err;
+
+	err = skcipher_walk_virt(&walk, req, false);
+	if (err)
+		return err;
+	return cbc_decrypt_walk(req, &walk);
+}
+
+static int cts_cbc_encrypt(struct skcipher_request *req)
 {
 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 	struct crypto_aes_ctx *ctx = crypto_skcipher_ctx(tfm);
+	int cbc_blocks = DIV_ROUND_UP(req->cryptlen, AES_BLOCK_SIZE) - 2;
+	struct scatterlist *src = req->src, *dst = req->dst;
+	struct scatterlist sg_src[2], sg_dst[2];
+	struct skcipher_request subreq;
 	struct skcipher_walk walk;
-	unsigned int blocks;
 	int err;
 
-	err = skcipher_walk_virt(&walk, req, false);
+	skcipher_request_set_tfm(&subreq, tfm);
+	skcipher_request_set_callback(&subreq, skcipher_request_flags(req),
+				      NULL, NULL);
+
+	if (req->cryptlen <= AES_BLOCK_SIZE) {
+		if (req->cryptlen < AES_BLOCK_SIZE)
+			return -EINVAL;
+		cbc_blocks = 1;
+	}
+
+	if (cbc_blocks > 0) {
+		skcipher_request_set_crypt(&subreq, req->src, req->dst,
+					   cbc_blocks * AES_BLOCK_SIZE,
+					   req->iv);
+
+		err = skcipher_walk_virt(&walk, &subreq, false) ?:
+		      cbc_encrypt_walk(&subreq, &walk);
+		if (err)
+			return err;
+
+		if (req->cryptlen == AES_BLOCK_SIZE)
+			return 0;
+
+		dst = src = scatterwalk_ffwd(sg_src, req->src, subreq.cryptlen);
+		if (req->dst != req->src)
+			dst = scatterwalk_ffwd(sg_dst, req->dst,
+					       subreq.cryptlen);
+	}
+
+	/* handle ciphertext stealing */
+	skcipher_request_set_crypt(&subreq, src, dst,
+				   req->cryptlen - cbc_blocks * AES_BLOCK_SIZE,
+				   req->iv);
+
+	err = skcipher_walk_virt(&walk, &subreq, false);
+	if (err)
+		return err;
 
-	while ((blocks = (walk.nbytes / AES_BLOCK_SIZE))) {
 	kernel_neon_begin();
-		ce_aes_cbc_decrypt(walk.dst.virt.addr, walk.src.virt.addr,
-				   ctx->key_dec, num_rounds(ctx), blocks,
+	ce_aes_cbc_cts_encrypt(walk.dst.virt.addr, walk.src.virt.addr,
+			       ctx->key_enc, num_rounds(ctx), walk.nbytes,
 			       walk.iv);
 	kernel_neon_end();
-		err = skcipher_walk_done(&walk, walk.nbytes % AES_BLOCK_SIZE);
+
+	return skcipher_walk_done(&walk, 0);
+}
+
+static int cts_cbc_decrypt(struct skcipher_request *req)
+{
+	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+	struct crypto_aes_ctx *ctx = crypto_skcipher_ctx(tfm);
+	int cbc_blocks = DIV_ROUND_UP(req->cryptlen, AES_BLOCK_SIZE) - 2;
+	struct scatterlist *src = req->src, *dst = req->dst;
+	struct scatterlist sg_src[2], sg_dst[2];
+	struct skcipher_request subreq;
+	struct skcipher_walk walk;
+	int err;
+
+	skcipher_request_set_tfm(&subreq, tfm);
+	skcipher_request_set_callback(&subreq, skcipher_request_flags(req),
+				      NULL, NULL);
+
+	if (req->cryptlen <= AES_BLOCK_SIZE) {
+		if (req->cryptlen < AES_BLOCK_SIZE)
+			return -EINVAL;
+		cbc_blocks = 1;
 	}
+
+	if (cbc_blocks > 0) {
+		skcipher_request_set_crypt(&subreq, req->src, req->dst,
+					   cbc_blocks * AES_BLOCK_SIZE,
+					   req->iv);
+
+		err = skcipher_walk_virt(&walk, &subreq, false) ?:
+		      cbc_decrypt_walk(&subreq, &walk);
+		if (err)
 			return err;
+
+		if (req->cryptlen == AES_BLOCK_SIZE)
+			return 0;
+
+		dst = src = scatterwalk_ffwd(sg_src, req->src, subreq.cryptlen);
+		if (req->dst != req->src)
+			dst = scatterwalk_ffwd(sg_dst, req->dst,
+					       subreq.cryptlen);
+	}
+
+	/* handle ciphertext stealing */
+	skcipher_request_set_crypt(&subreq, src, dst,
+				   req->cryptlen - cbc_blocks * AES_BLOCK_SIZE,
+				   req->iv);
+
+	err = skcipher_walk_virt(&walk, &subreq, false);
+	if (err)
+		return err;
+
+	kernel_neon_begin();
+	ce_aes_cbc_cts_decrypt(walk.dst.virt.addr, walk.src.virt.addr,
+			       ctx->key_dec, num_rounds(ctx), walk.nbytes,
+			       walk.iv);
+	kernel_neon_end();
+
+	return skcipher_walk_done(&walk, 0);
 }
 
 static int ctr_encrypt(struct skcipher_request *req)
@@ -486,6 +624,22 @@ static struct skcipher_alg aes_algs[] = { {
 	.setkey			= ce_aes_setkey,
 	.encrypt		= cbc_encrypt,
 	.decrypt		= cbc_decrypt,
+}, {
+	.base.cra_name		= "__cts(cbc(aes))",
+	.base.cra_driver_name	= "__cts-cbc-aes-ce",
+	.base.cra_priority	= 300,
+	.base.cra_flags		= CRYPTO_ALG_INTERNAL,
+	.base.cra_blocksize	= AES_BLOCK_SIZE,
+	.base.cra_ctxsize	= sizeof(struct crypto_aes_ctx),
+	.base.cra_module	= THIS_MODULE,
+
+	.min_keysize		= AES_MIN_KEY_SIZE,
+	.max_keysize		= AES_MAX_KEY_SIZE,
+	.ivsize			= AES_BLOCK_SIZE,
+	.walksize		= 2 * AES_BLOCK_SIZE,
+	.setkey			= ce_aes_setkey,
+	.encrypt		= cts_cbc_encrypt,
+	.decrypt		= cts_cbc_decrypt,
 }, {
 	.base.cra_name		= "__ctr(aes)",
 	.base.cra_driver_name	= "__ctr-aes-ce",