linux/arch/arm64/crypto/aes-ce-ccm-glue.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * aes-ccm-glue.c - AES-CCM transform for ARMv8 with Crypto Extensions
 *
 * Copyright (C) 2013 - 2017 Linaro Ltd <ard.biesheuvel@linaro.org>
 */

#include <asm/neon.h>
#include <asm/simd.h>
#include <asm/unaligned.h>
#include <crypto/aes.h>
#include <crypto/scatterwalk.h>
#include <crypto/internal/aead.h>
#include <crypto/internal/simd.h>
#include <crypto/internal/skcipher.h>
#include <linux/module.h>

#include "aes-ce-setkey.h"

static int num_rounds(struct crypto_aes_ctx *ctx)
{
	/*
	 * # of rounds specified by AES:
	 * 128 bit key		10 rounds
	 * 192 bit key		12 rounds
	 * 256 bit key		14 rounds
	 * => n byte key	=> 6 + (n/4) rounds
	 */
	return 6 + ctx->key_length / 4;
}

asmlinkage void ce_aes_ccm_auth_data(u8 mac[], u8 const in[], u32 abytes,
				     u32 *macp, u32 const rk[], u32 rounds);

asmlinkage void ce_aes_ccm_encrypt(u8 out[], u8 const in[], u32 cbytes,
				   u32 const rk[], u32 rounds, u8 mac[],
				   u8 ctr[]);

asmlinkage void ce_aes_ccm_decrypt(u8 out[], u8 const in[], u32 cbytes,
				   u32 const rk[], u32 rounds, u8 mac[],
				   u8 ctr[]);

asmlinkage void ce_aes_ccm_final(u8 mac[], u8 const ctr[], u32 const rk[],
				 u32 rounds);

static int ccm_setkey(struct crypto_aead *tfm, const u8 *in_key,
		      unsigned int key_len)
{
	struct crypto_aes_ctx *ctx = crypto_aead_ctx(tfm);
	int ret;

	ret = ce_aes_expandkey(ctx, in_key, key_len);
	if (!ret)
		return 0;

	tfm->base.crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
	return -EINVAL;
}

static int ccm_setauthsize(struct crypto_aead *tfm, unsigned int authsize)
{
	if ((authsize & 1) || authsize < 4)
		return -EINVAL;
	return 0;
}

static int ccm_init_mac(struct aead_request *req, u8 maciv[], u32 msglen)
{
	struct crypto_aead *aead = crypto_aead_reqtfm(req);
	__be32 *n = (__be32 *)&maciv[AES_BLOCK_SIZE - 8];
	u32 l = req->iv[0] + 1;

	/* verify that CCM dimension 'L' is set correctly in the IV */
	if (l < 2 || l > 8)
		return -EINVAL;

	/* verify that msglen can in fact be represented in L bytes */
	if (l < 4 && msglen >> (8 * l))
		return -EOVERFLOW;

	/*
	 * Even if the CCM spec allows L values of up to 8, the Linux cryptoapi
	 * uses a u32 type to represent msglen so the top 4 bytes are always 0.
	 */
	n[0] = 0;
	n[1] = cpu_to_be32(msglen);

	memcpy(maciv, req->iv, AES_BLOCK_SIZE - l);

	/*
	 * Meaning of byte 0 according to CCM spec (RFC 3610/NIST 800-38C)
	 * - bits 0..2	: max # of bytes required to represent msglen, minus 1
	 *                (already set by caller)
	 * - bits 3..5	: size of auth tag (1 => 4 bytes, 2 => 6 bytes, etc)
	 * - bit 6	: indicates presence of authenticate-only data
	 */
	maciv[0] |= (crypto_aead_authsize(aead) - 2) << 2;
	if (req->assoclen)
		maciv[0] |= 0x40;

	memset(&req->iv[AES_BLOCK_SIZE - l], 0, l);
	return 0;
}

static void ccm_update_mac(struct crypto_aes_ctx *key, u8 mac[], u8 const in[],
			   u32 abytes, u32 *macp)
{
	if (crypto_simd_usable()) {
		kernel_neon_begin();
		ce_aes_ccm_auth_data(mac, in, abytes, macp, key->key_enc,
				     num_rounds(key));
		kernel_neon_end();
	} else {
		if (*macp > 0 && *macp < AES_BLOCK_SIZE) {
			int added = min(abytes, AES_BLOCK_SIZE - *macp);

			crypto_xor(&mac[*macp], in, added);

			*macp += added;
			in += added;
			abytes -= added;
		}

		while (abytes >= AES_BLOCK_SIZE) {
			aes_encrypt(key, mac, mac);
			crypto_xor(mac, in, AES_BLOCK_SIZE);

			in += AES_BLOCK_SIZE;
			abytes -= AES_BLOCK_SIZE;
		}

		if (abytes > 0) {
			aes_encrypt(key, mac, mac);
			crypto_xor(mac, in, abytes);
			*macp = abytes;
		}
	}
}

static void ccm_calculate_auth_mac(struct aead_request *req, u8 mac[])
{
	struct crypto_aead *aead = crypto_aead_reqtfm(req);
	struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead);
	struct __packed { __be16 l; __be32 h; u16 len; } ltag;
	struct scatter_walk walk;
	u32 len = req->assoclen;
	u32 macp = 0;

	/* prepend the AAD with a length tag */
	if (len < 0xff00) {
		ltag.l = cpu_to_be16(len);
		ltag.len = 2;
	} else  {
		ltag.l = cpu_to_be16(0xfffe);
		put_unaligned_be32(len, &ltag.h);
		ltag.len = 6;
	}

	ccm_update_mac(ctx, mac, (u8 *)&ltag, ltag.len, &macp);
	scatterwalk_start(&walk, req->src);

	do {
		u32 n = scatterwalk_clamp(&walk, len);
		u8 *p;

		if (!n) {
			scatterwalk_start(&walk, sg_next(walk.sg));
			n = scatterwalk_clamp(&walk, len);
		}
		p = scatterwalk_map(&walk);
		ccm_update_mac(ctx, mac, p, n, &macp);
		len -= n;

		scatterwalk_unmap(p);
		scatterwalk_advance(&walk, n);
		scatterwalk_done(&walk, 0, len);
	} while (len);
}

static int ccm_crypt_fallback(struct skcipher_walk *walk, u8 mac[], u8 iv0[],
			      struct crypto_aes_ctx *ctx, bool enc)
{
	u8 buf[AES_BLOCK_SIZE];
	int err = 0;

	while (walk->nbytes) {
		int blocks = walk->nbytes / AES_BLOCK_SIZE;
		u32 tail = walk->nbytes % AES_BLOCK_SIZE;
		u8 *dst = walk->dst.virt.addr;
		u8 *src = walk->src.virt.addr;
		u32 nbytes = walk->nbytes;

		if (nbytes == walk->total && tail > 0) {
			blocks++;
			tail = 0;
		}

		do {
			u32 bsize = AES_BLOCK_SIZE;

			if (nbytes < AES_BLOCK_SIZE)
				bsize = nbytes;

			crypto_inc(walk->iv, AES_BLOCK_SIZE);
			aes_encrypt(ctx, buf, walk->iv);
			aes_encrypt(ctx, mac, mac);
			if (enc)
				crypto_xor(mac, src, bsize);
			crypto_xor_cpy(dst, src, buf, bsize);
			if (!enc)
				crypto_xor(mac, dst, bsize);
			dst += bsize;
			src += bsize;
			nbytes -= bsize;
		} while (--blocks);

		err = skcipher_walk_done(walk, tail);
	}

	if (!err) {
		aes_encrypt(ctx, buf, iv0);
		aes_encrypt(ctx, mac, mac);
		crypto_xor(mac, buf, AES_BLOCK_SIZE);
	}
	return err;
}

static int ccm_encrypt(struct aead_request *req)
{
	struct crypto_aead *aead = crypto_aead_reqtfm(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];
	u32 len = req->cryptlen;
	int err;

	err = ccm_init_mac(req, mac, len);
	if (err)
		return err;

	if (req->assoclen)
		ccm_calculate_auth_mac(req, mac);

	/* preserve the original iv for the final round */
	memcpy(buf, req->iv, AES_BLOCK_SIZE);

	err = skcipher_walk_aead_encrypt(&walk, req, false);

	if (crypto_simd_usable()) {
		while (walk.nbytes) {
			u32 tail = walk.nbytes % AES_BLOCK_SIZE;

			if (walk.nbytes == walk.total)
				tail = 0;

			kernel_neon_begin();
			ce_aes_ccm_encrypt(walk.dst.virt.addr,
					   walk.src.virt.addr,
					   walk.nbytes - tail, ctx->key_enc,
					   num_rounds(ctx), mac, walk.iv);
			kernel_neon_end();

			err = skcipher_walk_done(&walk, tail);
		}
		if (!err) {
			kernel_neon_begin();
			ce_aes_ccm_final(mac, buf, ctx->key_enc,
					 num_rounds(ctx));
			kernel_neon_end();
		}
	} else {
		err = ccm_crypt_fallback(&walk, mac, buf, ctx, true);
	}
	if (err)
		return err;

	/* copy authtag to end of dst */
	scatterwalk_map_and_copy(mac, req->dst, req->assoclen + req->cryptlen,
				 crypto_aead_authsize(aead), 1);

	return 0;
}

static int ccm_decrypt(struct aead_request *req)
{
	struct crypto_aead *aead = crypto_aead_reqtfm(req);
	struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead);
	unsigned int authsize = crypto_aead_authsize(aead);
	struct skcipher_walk walk;
	u8 __aligned(8) mac[AES_BLOCK_SIZE];
	u8 buf[AES_BLOCK_SIZE];
	u32 len = req->cryptlen - authsize;
	int err;

	err = ccm_init_mac(req, mac, len);
	if (err)
		return err;

	if (req->assoclen)
		ccm_calculate_auth_mac(req, mac);

	/* preserve the original iv for the final round */
	memcpy(buf, req->iv, AES_BLOCK_SIZE);

	err = skcipher_walk_aead_decrypt(&walk, req, false);

	if (crypto_simd_usable()) {
		while (walk.nbytes) {
			u32 tail = walk.nbytes % AES_BLOCK_SIZE;

			if (walk.nbytes == walk.total)
				tail = 0;

			kernel_neon_begin();
			ce_aes_ccm_decrypt(walk.dst.virt.addr,
					   walk.src.virt.addr,
					   walk.nbytes - tail, ctx->key_enc,
					   num_rounds(ctx), mac, walk.iv);
			kernel_neon_end();

			err = skcipher_walk_done(&walk, tail);
		}
		if (!err) {
			kernel_neon_begin();
			ce_aes_ccm_final(mac, buf, ctx->key_enc,
					 num_rounds(ctx));
			kernel_neon_end();
		}
	} else {
		err = ccm_crypt_fallback(&walk, mac, buf, ctx, false);
	}

	if (err)
		return err;

	/* compare calculated auth tag with the stored one */
	scatterwalk_map_and_copy(buf, req->src,
				 req->assoclen + req->cryptlen - authsize,
				 authsize, 0);

	if (crypto_memneq(mac, buf, authsize))
		return -EBADMSG;
	return 0;
}

static struct aead_alg ccm_aes_alg = {
	.base = {
		.cra_name		= "ccm(aes)",
		.cra_driver_name	= "ccm-aes-ce",
		.cra_priority		= 300,
		.cra_blocksize		= 1,
		.cra_ctxsize		= sizeof(struct crypto_aes_ctx),
		.cra_module		= THIS_MODULE,
	},
	.ivsize		= AES_BLOCK_SIZE,
	.chunksize	= AES_BLOCK_SIZE,
	.maxauthsize	= AES_BLOCK_SIZE,
	.setkey		= ccm_setkey,
	.setauthsize	= ccm_setauthsize,
	.encrypt	= ccm_encrypt,
	.decrypt	= ccm_decrypt,
};

static int __init aes_mod_init(void)
{
	if (!cpu_have_named_feature(AES))
		return -ENODEV;
	return crypto_register_aead(&ccm_aes_alg);
}

static void __exit aes_mod_exit(void)
{
	crypto_unregister_aead(&ccm_aes_alg);
}

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_LICENSE("GPL v2");
MODULE_ALIAS_CRYPTO("ccm(aes)");