/* mpicoder.c  -  Coder for the external representation of MPIs * Copyright (C) 1998, 1999 Free Software Foundation, Inc. * * This file is part of GnuPG. * * GnuPG is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * GnuPG is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA */ #include "mpi-internal.h" #define DIM(v) (sizeof(v)/sizeof((v)[0]))#define MAX_EXTERN_MPI_BITS 16384 static uint8_t asn[15] =	/* Object ID is 1.3.14.3.2.26 */{ 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03,	0x02, 0x1a, 0x05, 0x00, 0x04, 0x14}; MPI do_encode_md(const void *sha_buffer, unsigned nbits){	int nframe = (nbits + 7) / 8;	uint8_t *frame, *fr_pt;	int i = 0, n;	size_t asnlen = DIM(asn);	MPI a = MPI_NULL; 	if (SHA1_DIGEST_LENGTH + asnlen + 4 > nframe)		pr_info("MPI: can't encode a %d bit MD into a %d bits frame\n",		       (int)(SHA1_DIGEST_LENGTH * 8), (int)nbits); 	/* We encode the MD in this way:	 *	 *       0  A PAD(n bytes)   0  ASN(asnlen bytes)  MD(len bytes)	 *	 * PAD consists of FF bytes.	 */	frame = kmalloc(nframe, GFP_KERNEL);	if (!frame)		return MPI_NULL;	n = 0;	frame[n++] = 0;	frame[n++] = 1;		/* block type */	i = nframe - SHA1_DIGEST_LENGTH - asnlen - 3; 	if (i <= 1) {		pr_info("MPI: message digest encoding failed\n");		kfree(frame);		return a;	} 	memset(frame + n, 0xff, i);	n += i;	frame[n++] = 0;	memcpy(frame + n, &asn, asnlen);	n += asnlen;	memcpy(frame + n, sha_buffer, SHA1_DIGEST_LENGTH);	n += SHA1_DIGEST_LENGTH; 	i = nframe;	fr_pt = frame; 	if (n != nframe) {		printk		    ("MPI: message digest encoding failed, frame length is wrong\n");		kfree(frame);		return a;	} 	a = mpi_alloc((nframe + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB);	mpi_set_buffer(a, frame, nframe, 0);	kfree(frame); 	return a;} MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread){	const uint8_t *buffer = xbuffer;	int i, j;	unsigned nbits, nbytes, nlimbs, nread = 0;	mpi_limb_t a;	MPI val = MPI_NULL; 	if (*ret_nread < 2)		goto leave;	nbits = buffer[0] << 8 | buffer[1]; 	if (nbits > MAX_EXTERN_MPI_BITS) {		pr_info("MPI: mpi too large (%u bits)\n", nbits);		goto leave;	}	buffer += 2;	nread = 2; 	nbytes = (nbits + 7) / 8;	nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;	val = mpi_alloc(nlimbs);	if (!val)		return MPI_NULL;	i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;	i %= BYTES_PER_MPI_LIMB;	val->nbits = nbits;	j = val->nlimbs = nlimbs;	val->sign = 0;	for (; j > 0; j--) {		a = 0;		for (; i < BYTES_PER_MPI_LIMB; i++) {			if (++nread > *ret_nread) {				printk				    ("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",				     nread, *ret_nread);				goto leave;			}			a <<= 8;			a |= *buffer++;		}		i = 0;		val->d[j - 1] = a;	} leave:	*ret_nread = nread;	return val;}EXPORT_SYMBOL_GPL(mpi_read_from_buffer); /**************** * Make an mpi from a character string. */int mpi_fromstr(MPI val, const char *str){	int hexmode = 0, sign = 0, prepend_zero = 0, i, j, c, c1, c2;	unsigned nbits, nbytes, nlimbs;	mpi_limb_t a; 	if (*str == '-') {		sign = 1;		str++;	}	if (*str == '0' && str[1] == 'x')		hexmode = 1;	else		return -EINVAL;	/* other bases are not yet supported */	str += 2; 	nbits = strlen(str) * 4;	if (nbits % 8)		prepend_zero = 1;	nbytes = (nbits + 7) / 8;	nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;	if (val->alloced < nlimbs)		if (!mpi_resize(val, nlimbs))			return -ENOMEM;	i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;	i %= BYTES_PER_MPI_LIMB;	j = val->nlimbs = nlimbs;	val->sign = sign;	for (; j > 0; j--) {		a = 0;		for (; i < BYTES_PER_MPI_LIMB; i++) {			if (prepend_zero) {				c1 = '0';				prepend_zero = 0;			} else				c1 = *str++;			assert(c1);			c2 = *str++;			assert(c2);			if (c1 >= '0' && c1 <= '9')				c = c1 - '0';			else if (c1 >= 'a' && c1 <= 'f')				c = c1 - 'a' + 10;			else if (c1 >= 'A' && c1 <= 'F')				c = c1 - 'A' + 10;			else {				mpi_clear(val);				return 1;			}			c <<= 4;			if (c2 >= '0' && c2 <= '9')				c |= c2 - '0';			else if (c2 >= 'a' && c2 <= 'f')				c |= c2 - 'a' + 10;			else if (c2 >= 'A' && c2 <= 'F')				c |= c2 - 'A' + 10;			else {				mpi_clear(val);				return 1;			}			a <<= 8;			a |= c;		}		i = 0; 		val->d[j - 1] = a;	} 	return 0;}EXPORT_SYMBOL_GPL(mpi_fromstr); /**************** * Special function to get the low 8 bytes from an mpi. * This can be used as a keyid; KEYID is an 2 element array. * Return the low 4 bytes. */u32 mpi_get_keyid(const MPI a, u32 *keyid){#if BYTES_PER_MPI_LIMB == 4	if (keyid) {		keyid[0] = a->nlimbs >= 2 ? a->d[1] : 0;		keyid[1] = a->nlimbs >= 1 ? a->d[0] : 0;	}	return a->nlimbs >= 1 ? a->d[0] : 0;#elif BYTES_PER_MPI_LIMB == 8	if (keyid) {		keyid[0] = a->nlimbs ? (u32) (a->d[0] >> 32) : 0;		keyid[1] = a->nlimbs ? (u32) (a->d[0] & 0xffffffff) : 0;	}	return a->nlimbs ? (u32) (a->d[0] & 0xffffffff) : 0;#else#error Make this function work with other LIMB sizes#endif} /**************** * Return an allocated buffer with the MPI (msb first). * NBYTES receives the length of this buffer. Caller must free the * return string (This function does return a 0 byte buffer with NBYTES * set to zero if the value of A is zero. If sign is not NULL, it will * be set to the sign of the A. */void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign){	uint8_t *p, *buffer;	mpi_limb_t alimb;	int i;	unsigned int n; 	if (sign)		*sign = a->sign;	*nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB;	if (!n)		n++;		/* avoid zero length allocation */	p = buffer = kmalloc(n, GFP_KERNEL);	if (!p)		return NULL; 	for (i = a->nlimbs - 1; i >= 0; i--) {		alimb = a->d[i];#if BYTES_PER_MPI_LIMB == 4		*p++ = alimb >> 24;		*p++ = alimb >> 16;		*p++ = alimb >> 8;		*p++ = alimb;#elif BYTES_PER_MPI_LIMB == 8		*p++ = alimb >> 56;		*p++ = alimb >> 48;		*p++ = alimb >> 40;		*p++ = alimb >> 32;		*p++ = alimb >> 24;		*p++ = alimb >> 16;		*p++ = alimb >> 8;		*p++ = alimb;#else#error please implement for this limb size.#endif	} 	/* this is sub-optimal but we need to do the shift operation	 * because the caller has to free the returned buffer */	for (p = buffer; !*p && *nbytes; p++, --*nbytes)		;	if (p != buffer)		memmove(buffer, p, *nbytes); 	return buffer;}EXPORT_SYMBOL_GPL(mpi_get_buffer); /**************** * Use BUFFER to update MPI. */int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign){	const uint8_t *buffer = xbuffer, *p;	mpi_limb_t alimb;	int nlimbs;	int i; 	nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;	if (RESIZE_IF_NEEDED(a, nlimbs) < 0)		return -ENOMEM;	a->sign = sign; 	for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {#if BYTES_PER_MPI_LIMB == 4		alimb = (mpi_limb_t) *p--;		alimb |= (mpi_limb_t) *p-- << 8;		alimb |= (mpi_limb_t) *p-- << 16;		alimb |= (mpi_limb_t) *p-- << 24;#elif BYTES_PER_MPI_LIMB == 8		alimb = (mpi_limb_t) *p--;		alimb |= (mpi_limb_t) *p-- << 8;		alimb |= (mpi_limb_t) *p-- << 16;		alimb |= (mpi_limb_t) *p-- << 24;		alimb |= (mpi_limb_t) *p-- << 32;		alimb |= (mpi_limb_t) *p-- << 40;		alimb |= (mpi_limb_t) *p-- << 48;		alimb |= (mpi_limb_t) *p-- << 56;#else#error please implement for this limb size.#endif		a->d[i++] = alimb;	}	if (p >= buffer) {#if BYTES_PER_MPI_LIMB == 4		alimb = *p--;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 8;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 16;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 24;#elif BYTES_PER_MPI_LIMB == 8		alimb = (mpi_limb_t) *p--;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 8;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 16;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 24;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 32;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 40;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 48;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 56;#else#error please implement for this limb size.#endif		a->d[i++] = alimb;	}	a->nlimbs = i; 	if (i != nlimbs) {		pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,		       nlimbs);		BUG();	}	return 0;}EXPORT_SYMBOL_GPL(mpi_set_buffer);