bufec.c 3.87 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146
/* $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 "includes.h"

#ifdef OPENSSL_HAS_ECC

#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__);
}

#endif /* OPENSSL_HAS_ECC */