ccm128.c: initial draft.

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#include <openssl/crypto.h>

#include "modes_lcl.h"

#include <string.h>

#ifndef MODES_DEBUG

# ifndef NDEBUG

#  define NDEBUG

# endif

#endif

#include <assert.h>

typedef struct {

	union { u8 c[16]; size_t s[16/sizeof(size_t)]; } nonce, cmac,

							 scratch, inp;

	u64 blocks;

	block128_f block;

	void *key;

} CCM128_CONTEXT;

/* First you setup M and L parameters and pass the key schedule */

void CRYPTO_ccm128_init(CCM128_CONTEXT *ctx,

	unsigned int M,unsigned int L,void *key)

{

	memset(ctx->nonce.c,0,sizeof(ctx->nonce.c));

	ctx->nonce.c[0] = ((u8)(L-1)&7) | (u8)(((M-2)/2)&7)<<3;

	ctx->blocks = 0;

	ctx->key = key;

}

/* !!! Following interfaces are to be called *once* per packet !!! */

/* Then you setup per-message nonce and pass the length of the message */

int CRYPTO_ccm128_setiv(CCM128_CONTEXT *ctx,

	const unsigned char *nonce,size_t nlen,size_t mlen)

{

	unsigned int L = ctx->nonce.c[0]&7;	/* the L parameter */

	if (nlen<(14-L)) return -1;		/* nonce is too short */

	if (sizeof(mlen)==8 && L>=3) {

		ctx->nonce.c[8]  = (u8)(mlen>>(56%(sizeof(mlen)*8)));

		ctx->nonce.c[9]  = (u8)(mlen>>(48%(sizeof(mlen)*8)));

		ctx->nonce.c[10] = (u8)(mlen>>(40%(sizeof(mlen)*8)));

		ctx->nonce.c[11] = (u8)(mlen>>(32%(sizeof(mlen)*8)));

	}

	else

		*((size_t *)&ctx->nonce.s[8]) = 0;

	ctx->nonce.c[12] = (u8)(mlen>>24);

	ctx->nonce.c[13] = (u8)(mlen>>16);

	ctx->nonce.c[14] = (u8)(mlen>>8);

	ctx->nonce.c[15] = (u8)mlen;

	ctx->nonce.c[0] &= ~0x40;	/* clear Adata flag */

	memcpy(&ctx->nonce.c[1],nonce,14-L);

	return 0;

}

/* Then you pass additional authentication data, this is optional */

void CRYPTO_ccm128_aad(CCM128_CONTEXT *ctx,

	const unsigned char *aad,size_t alen)

{	unsigned int i;

	if (alen==0) return;

	ctx->nonce.c[0] |= 0x40;	/* set Adata flag */

	(*ctx->block)(ctx->nonce.c,ctx->cmac.c,ctx->key),

	ctx->blocks++;

	if (alen<(0x10000-0x100)) {

		ctx->cmac.c[0] ^= (u8)(alen>>8);

		ctx->cmac.c[1] ^= (u8)alen;

		i=2;

	}

	else if (sizeof(alen)==8 && alen>=(size_t)1<<32) {

		ctx->cmac.c[0] ^= 0xFF;

		ctx->cmac.c[1] ^= 0xFF;

		ctx->cmac.c[2] ^= (u8)(alen>>(56%(sizeof(alen)*8)));

		ctx->cmac.c[3] ^= (u8)(alen>>(48%(sizeof(alen)*8)));

		ctx->cmac.c[4] ^= (u8)(alen>>(40%(sizeof(alen)*8)));

		ctx->cmac.c[5] ^= (u8)(alen>>(32%(sizeof(alen)*8)));

		ctx->cmac.c[6] ^= (u8)(alen>>24);

		ctx->cmac.c[7] ^= (u8)(alen>>16);

		ctx->cmac.c[8] ^= (u8)(alen>>8);

		ctx->cmac.c[9] ^= (u8)alen;

		i=10;

	}

	else {

		ctx->cmac.c[0] ^= 0xFF;

		ctx->cmac.c[1] ^= 0xFE;

		ctx->cmac.c[2] ^= (u8)(alen>>24);

		ctx->cmac.c[3] ^= (u8)(alen>>16);

		ctx->cmac.c[4] ^= (u8)(alen>>8);

		ctx->cmac.c[5] ^= (u8)alen;

		i=6;

	}

	do {

		for(;i<16 && alen;++i,++aad,--alen)

			ctx->cmac.c[i] ^= *aad;

		(*ctx->block)(ctx->cmac.c,ctx->cmac.c,ctx->key),

		ctx->blocks++;

		i=0;

	} while (alen);

}

/* Finally you encrypt or decrypt the message */

static void ctr128_inc(unsigned char *counter) {

	unsigned int n=16;

	u8  c;

	do {

		--n;

		c = counter[n];

		++c;

		counter[n] = c;

		if (c) return;

	} while (n);

}

int CRYPTO_ccm128_encrypt(CCM128_CONTEXT *ctx,

	const unsigned char *inp, unsigned char *out,

	size_t len)

{

	size_t		n;

	unsigned int	i;

	unsigned char	flags = ctx->nonce.c[0];

	if (!(flags&0x40))

		(*ctx->block)(ctx->nonce.c,ctx->cmac.c,ctx->key),

		ctx->blocks++;

	flags &= 7;	/* extract the L parameter */

	for (n=0,i=15-flags;i<15;++i) {

		n |= ctx->nonce.c[i]; ctx->nonce.c[i]=0;

		n <<= 8;

	}

	n |= ctx->nonce.c[15];	/* reconstructed length */

	ctx->nonce.c[15]=1;

	if (n!=len) return -1;	/* length mismatch */

	ctx->blocks += ((len+15)>>3)|1;

	if (ctx->blocks > (U64(1)<<61))	return -2; /* too much data */

	while (len>=16) {

#if defined(STRICT_ALIGNMENT)

		memcpy (ctx->inp.c,inp,16);

		for (i=0; i<16/sizeof(size_t); ++i)

			ctx->cmac.s[i] ^= ctx->inp.s[i];

#else

		for (i=0; i<16/sizeof(size_t); ++i)

			ctx->cmac.s[i] ^= ((size_t*)inp)[i];

#endif

		(*ctx->block)(ctx->cmac.c,ctx->cmac.c,ctx->key);

		(*ctx->block)(ctx->nonce.c,ctx->scratch.c,ctx->key);

		ctr128_inc(ctx->nonce.c);

#if defined(STRICT_ALIGNMENT)

		for (i=0; i<16/sizeof(size_t); ++i)

			ctx->inp.s[i] ^= ctx->scratch.s[i];

		memcpy(out,ctx->inp.c,16);

#else

		for (i=0; i<16/sizeof(size_t); ++i)

			((size_t*)out)[i] = ctx->scratch.s[i]^((size_t*)inp)[i];

#endif

		inp += 16;

		out += 16;

		len -= 16;

	}

	if (len) {

		for (i=0; i<len; ++i) ctx->cmac.c[i] ^= inp[i];

		(*ctx->block)(ctx->cmac.c,ctx->cmac.c,ctx->key);

		(*ctx->block)(ctx->nonce.c,ctx->scratch.c,ctx->key);

		for (i=0; i<len; ++i) out[i] = ctx->scratch.c[i]^inp[i];

	}

	for (i=15-flags;i<16;++i)

		ctx->nonce.c[i]=0;

	(*ctx->block)(ctx->nonce.c,ctx->scratch.c,ctx->key);

	for (i=0; i<16/sizeof(size_t); ++i)

		ctx->cmac.s[i] ^= ctx->scratch.s[i];

	return 0;

}

int CRYPTO_ccm128_decrypt(CCM128_CONTEXT *ctx,

	const unsigned char *inp, unsigned char *out,

	size_t len)

{

	size_t		n;

	unsigned int	i;

	unsigned char	flags = ctx->nonce.c[0];

	if (!(flags&0x40))

		(*ctx->block)(ctx->nonce.c,ctx->cmac.c,ctx->key);

	flags &= 7;	/* extract the L parameter */

	for (n=0,i=15-flags;i<15;++i) {

		n |= ctx->nonce.c[i]; ctx->nonce.c[i]=0;

		n <<= 8;

	}

	n |= ctx->nonce.c[15];	/* reconstructed length */

	ctx->nonce.c[15]=1;

	if (n!=len) return -1;

	while (len>=16) {

		(*ctx->block)(ctx->nonce.c,ctx->scratch.c,ctx->key);

		ctr128_inc(ctx->nonce.c);

#if defined(STRICT_ALIGNMENT)

		memcpy (ctx->inp.c,inp,16);

		for (i=0; i<16/sizeof(size_t); ++i)

			ctx->cmac.s[i] ^= (ctx->scratch.s[i] ^= ctx->inp.s[i]);

		memcpy (out,ctx->scratch,16);

#else

		for (i=0; i<16/sizeof(size_t); ++i)

			ctx->cmac.s[i] ^= ((size_t*)out)[i] = ctx->scratch.s[i]^((size_t*)inp)[i];

#endif

		(*ctx->block)(ctx->cmac.c,ctx->cmac.c,ctx->key);

		inp += 16;

		out += 16;

		len -= 16;

	}

	if (len) {

		(*ctx->block)(ctx->nonce.c,ctx->scratch.c,ctx->key);

		for (i=0; i<len; ++len)

			ctx->cmac.c[i] ^= (out[i] = ctx->scratch.c[i]^inp[i]);

		(*ctx->block)(ctx->cmac.c,ctx->cmac.c,ctx->key);

	}

	for (i=15-flags;i<16;++i)

		ctx->nonce.c[i]=0;

	(*ctx->block)(ctx->nonce.c,ctx->scratch.c,ctx->key);

	for (i=0; i<16/sizeof(size_t); ++i)

		ctx->cmac.s[i] ^= ctx->scratch.s[i];

	return 0;

}

size_t CRYPTO_ccm128_tag(CCM128_CONTEXT *ctx,unsigned char *tag,size_t len)

{	unsigned int M = (ctx->nonce.c[0]>>3)&7;	/* the M parameter */

	M *= 2; M += 2;

	if (len<M)	return 0;

	memcpy(tag,ctx->cmac.c,M);

	return M;

}