crypto: arm64/aes-ccm - Pass short inputs via stack buffer

In preparation for optimizing the CCM core asm code using permutation
vectors and overlapping loads and stores, ensure that inputs shorter
than the size of a AES block are passed via a buffer on the stack, in a
way that positions the data at the end of a 16 byte buffer. This removes
the need for the asm code to reason about a rare corner case where the
tail of the data cannot be read/written using a single NEON load/store
instruction.

While at it, tweak the copyright header and authorship to bring it up to
date.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 40 insertions, 17 deletions

diff --git a/arch/arm64/crypto/aes-ce-ccm-glue.c b/arch/arm64/crypto/aes-ce-ccm-glue.c
index b177ebea7d0911..4710e59075f5f0 100644
--- a/arch/arm64/crypto/aes-ce-ccm-glue.c
+++ b/arch/arm64/crypto/aes-ce-ccm-glue.c
@@ -1,8 +1,11 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /*
- * aes-ccm-glue.c - AES-CCM transform for ARMv8 with Crypto Extensions
+ * aes-ce-ccm-glue.c - AES-CCM transform for ARMv8 with Crypto Extensions
  *
- * Copyright (C) 2013 - 2017 Linaro Ltd <ard.biesheuvel@linaro.org>
+ * Copyright (C) 2013 - 2017 Linaro Ltd.
+ * Copyright (C) 2024 Google LLC
+ *
+ * Author: Ard Biesheuvel <ardb@kernel.org>
  */
 
 #include <asm/neon.h>
@@ -149,7 +152,7 @@ static int ccm_encrypt(struct aead_request *req)
 	struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead);
 	struct skcipher_walk walk;
 	u8 __aligned(8) mac[AES_BLOCK_SIZE];
-	u8 buf[AES_BLOCK_SIZE];
+	u8 orig_iv[AES_BLOCK_SIZE];
 	u32 len = req->cryptlen;
 	int err;
 
@@ -158,7 +161,7 @@ static int ccm_encrypt(struct aead_request *req)
 		return err;
 
 	/* preserve the original iv for the final round */
-	memcpy(buf, req->iv, AES_BLOCK_SIZE);
+	memcpy(orig_iv, req->iv, AES_BLOCK_SIZE);
 
 	err = skcipher_walk_aead_encrypt(&walk, req, false);
 	if (unlikely(err))
@@ -171,16 +174,26 @@ static int ccm_encrypt(struct aead_request *req)
 
 	do {
 		u32 tail = walk.nbytes % AES_BLOCK_SIZE;
+		const u8 *src = walk.src.virt.addr;
+		u8 *dst = walk.dst.virt.addr;
+		u8 buf[AES_BLOCK_SIZE];
 
 		if (walk.nbytes == walk.total)
 			tail = 0;
 
-		ce_aes_ccm_encrypt(walk.dst.virt.addr, walk.src.virt.addr,
-				   walk.nbytes - tail, ctx->key_enc,
-				   num_rounds(ctx), mac, walk.iv);
+		if (unlikely(walk.nbytes < AES_BLOCK_SIZE))
+			src = dst = memcpy(&buf[sizeof(buf) - walk.nbytes],
+					   src, walk.nbytes);
+
+		ce_aes_ccm_encrypt(dst, src, walk.nbytes - tail,
+				   ctx->key_enc, num_rounds(ctx),
+				   mac, walk.iv);
+
+		if (unlikely(walk.nbytes < AES_BLOCK_SIZE))
+			memcpy(walk.dst.virt.addr, dst, walk.nbytes);
 
 		if (walk.nbytes == walk.total)
-			ce_aes_ccm_final(mac, buf, ctx->key_enc, num_rounds(ctx));
+			ce_aes_ccm_final(mac, orig_iv, ctx->key_enc, num_rounds(ctx));
 
 		if (walk.nbytes) {
 			err = skcipher_walk_done(&walk, tail);
@@ -206,7 +219,7 @@ static int ccm_decrypt(struct aead_request *req)
 	unsigned int authsize = crypto_aead_authsize(aead);
 	struct skcipher_walk walk;
 	u8 __aligned(8) mac[AES_BLOCK_SIZE];
-	u8 buf[AES_BLOCK_SIZE];
+	u8 orig_iv[AES_BLOCK_SIZE];
 	u32 len = req->cryptlen - authsize;
 	int err;
 
@@ -215,7 +228,7 @@ static int ccm_decrypt(struct aead_request *req)
 		return err;
 
 	/* preserve the original iv for the final round */
-	memcpy(buf, req->iv, AES_BLOCK_SIZE);
+	memcpy(orig_iv, req->iv, AES_BLOCK_SIZE);
 
 	err = skcipher_walk_aead_decrypt(&walk, req, false);
 	if (unlikely(err))
@@ -228,16 +241,26 @@ static int ccm_decrypt(struct aead_request *req)
 
 	do {
 		u32 tail = walk.nbytes % AES_BLOCK_SIZE;
+		const u8 *src = walk.src.virt.addr;
+		u8 *dst = walk.dst.virt.addr;
+		u8 buf[AES_BLOCK_SIZE];
 
 		if (walk.nbytes == walk.total)
 			tail = 0;
 
-		ce_aes_ccm_decrypt(walk.dst.virt.addr, walk.src.virt.addr,
-				   walk.nbytes - tail, ctx->key_enc,
-				   num_rounds(ctx), mac, walk.iv);
+		if (unlikely(walk.nbytes < AES_BLOCK_SIZE))
+			src = dst = memcpy(&buf[sizeof(buf) - walk.nbytes],
+					   src, walk.nbytes);
+
+		ce_aes_ccm_decrypt(dst, src, walk.nbytes - tail,
+				   ctx->key_enc, num_rounds(ctx),
+				   mac, walk.iv);
+
+		if (unlikely(walk.nbytes < AES_BLOCK_SIZE))
+			memcpy(walk.dst.virt.addr, dst, walk.nbytes);
 
 		if (walk.nbytes == walk.total)
-			ce_aes_ccm_final(mac, buf, ctx->key_enc, num_rounds(ctx));
+			ce_aes_ccm_final(mac, orig_iv, ctx->key_enc, num_rounds(ctx));
 
 		if (walk.nbytes) {
 			err = skcipher_walk_done(&walk, tail);
@@ -250,11 +273,11 @@ static int ccm_decrypt(struct aead_request *req)
 		return err;
 
 	/* compare calculated auth tag with the stored one */
-	scatterwalk_map_and_copy(buf, req->src,
+	scatterwalk_map_and_copy(orig_iv, req->src,
 				 req->assoclen + req->cryptlen - authsize,
 				 authsize, 0);
 
-	if (crypto_memneq(mac, buf, authsize))
+	if (crypto_memneq(mac, orig_iv, authsize))
 		return -EBADMSG;
 	return 0;
 }
@@ -293,6 +316,6 @@ module_init(aes_mod_init);
 module_exit(aes_mod_exit);
 
 MODULE_DESCRIPTION("Synchronous AES in CCM mode using ARMv8 Crypto Extensions");
-MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
+MODULE_AUTHOR("Ard Biesheuvel <ardb@kernel.org>");
 MODULE_LICENSE("GPL v2");
 MODULE_ALIAS_CRYPTO("ccm(aes)");