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/* $OpenBSD: bufec.c,v 1.1 2010/08/31 11:54:45 djm Exp $ */
/*
* Copyright (c) 2010 Damien Miller <djm@mindrot.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/types.h>
#include <openssl/bn.h>
#include <openssl/ec.h>
#include <string.h>
#include <stdarg.h>
#include "xmalloc.h"
#include "buffer.h"
#include "log.h"
#include "misc.h"
/*
* Maximum supported EC GFp field length is 528 bits. SEC1 uncompressed
* encoding represents this as two bitstring points that should each
* be no longer than the field length, SEC1 specifies a 1 byte
* point type header.
* Being paranoid here may insulate us to parsing problems in
* EC_POINT_oct2point.
*/
#define BUFFER_MAX_ECPOINT_LEN ((528*2 / 8) + 1)
/*
* Append an EC_POINT to the buffer as a string containing a SEC1 encoded
* uncompressed point. Fortunately OpenSSL handles the gory details for us.
*/
int
buffer_put_ecpoint_ret(Buffer *buffer, const EC_GROUP *curve,
const EC_POINT *point)
{
u_char *buf = NULL;
size_t len;
BN_CTX *bnctx;
int ret = -1;
/* Determine length */
if ((bnctx = BN_CTX_new()) == NULL)
fatal("%s: BN_CTX_new failed", __func__);
len = EC_POINT_point2oct(curve, point, POINT_CONVERSION_UNCOMPRESSED,
NULL, 0, bnctx);
if (len > BUFFER_MAX_ECPOINT_LEN) {
error("%s: giant EC point: len = %lu (max %u)",
__func__, (u_long)len, BUFFER_MAX_ECPOINT_LEN);
goto out;
}
/* Convert */
buf = xmalloc(len);
if (EC_POINT_point2oct(curve, point, POINT_CONVERSION_UNCOMPRESSED,
buf, len, bnctx) != len) {
error("%s: EC_POINT_point2oct length mismatch", __func__);
goto out;
}
/* Append */
buffer_put_string(buffer, buf, len);
ret = 0;
out:
if (buf != NULL) {
bzero(buf, len);
xfree(buf);
}
BN_CTX_free(bnctx);
return ret;
}
void
buffer_put_ecpoint(Buffer *buffer, const EC_GROUP *curve,
const EC_POINT *point)
{
if (buffer_put_ecpoint_ret(buffer, curve, point) == -1)
fatal("%s: buffer error", __func__);
}
int
buffer_get_ecpoint_ret(Buffer *buffer, const EC_GROUP *curve,
EC_POINT *point)
{
u_char *buf;
u_int len;
BN_CTX *bnctx;
int ret = -1;
if ((buf = buffer_get_string_ret(buffer, &len)) == NULL) {
error("%s: invalid point", __func__);
return -1;
}
if ((bnctx = BN_CTX_new()) == NULL)
fatal("%s: BN_CTX_new failed", __func__);
if (len > BUFFER_MAX_ECPOINT_LEN) {
error("%s: EC_POINT too long: %u > max %u", __func__,
len, BUFFER_MAX_ECPOINT_LEN);
goto out;
}
if (len == 0) {
error("%s: EC_POINT buffer is empty", __func__);
goto out;
}
if (buf[0] != POINT_CONVERSION_UNCOMPRESSED) {
error("%s: EC_POINT is in an incorrect form: "
"0x%02x (want 0x%02x)", __func__, buf[0],
POINT_CONVERSION_UNCOMPRESSED);
goto out;
}
if (EC_POINT_oct2point(curve, point, buf, len, bnctx) != 1) {
error("buffer_get_bignum2_ret: BN_bin2bn failed");
goto out;
}
/* EC_POINT_oct2point verifies that the point is on the curve for us */
ret = 0;
out:
BN_CTX_free(bnctx);
bzero(buf, len);
xfree(buf);
return ret;
}
void
buffer_get_ecpoint(Buffer *buffer, const EC_GROUP *curve,
EC_POINT *point)
{
if (buffer_get_ecpoint_ret(buffer, curve, point) == -1)
fatal("%s: buffer error", __func__);
}
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