1/* $OpenBSD: bufec.c,v 1.1 2010/08/31 11:54:45 djm Exp $ */
2/*
3 * Copyright (c) 2010 Damien Miller <djm@mindrot.org>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18#include "includes.h"
19
20#ifdef OPENSSL_HAS_ECC
21
22#include <sys/types.h>
23
24#include <openssl/bn.h>
25#include <openssl/ec.h>
26
27#include <string.h>
28#include <stdarg.h>
29
30#include "xmalloc.h"
31#include "buffer.h"
32#include "log.h"
33#include "misc.h"
34
35/*
36 * Maximum supported EC GFp field length is 528 bits. SEC1 uncompressed
37 * encoding represents this as two bitstring points that should each
38 * be no longer than the field length, SEC1 specifies a 1 byte
39 * point type header.
40 * Being paranoid here may insulate us to parsing problems in
41 * EC_POINT_oct2point.
42 */
43#define BUFFER_MAX_ECPOINT_LEN ((528*2 / 8) + 1)
44
45/*
46 * Append an EC_POINT to the buffer as a string containing a SEC1 encoded
47 * uncompressed point. Fortunately OpenSSL handles the gory details for us.
48 */
49int
50buffer_put_ecpoint_ret(Buffer *buffer, const EC_GROUP *curve,
51    const EC_POINT *point)
52{
53	u_char *buf = NULL;
54	size_t len;
55	BN_CTX *bnctx;
56	int ret = -1;
57
58	/* Determine length */
59	if ((bnctx = BN_CTX_new()) == NULL)
60		fatal("%s: BN_CTX_new failed", __func__);
61	len = EC_POINT_point2oct(curve, point, POINT_CONVERSION_UNCOMPRESSED,
62	    NULL, 0, bnctx);
63	if (len > BUFFER_MAX_ECPOINT_LEN) {
64		error("%s: giant EC point: len = %lu (max %u)",
65		    __func__, (u_long)len, BUFFER_MAX_ECPOINT_LEN);
66		goto out;
67	}
68	/* Convert */
69	buf = xmalloc(len);
70	if (EC_POINT_point2oct(curve, point, POINT_CONVERSION_UNCOMPRESSED,
71	    buf, len, bnctx) != len) {
72		error("%s: EC_POINT_point2oct length mismatch", __func__);
73		goto out;
74	}
75	/* Append */
76	buffer_put_string(buffer, buf, len);
77	ret = 0;
78 out:
79	if (buf != NULL) {
80		bzero(buf, len);
81		xfree(buf);
82	}
83	BN_CTX_free(bnctx);
84	return ret;
85}
86
87void
88buffer_put_ecpoint(Buffer *buffer, const EC_GROUP *curve,
89    const EC_POINT *point)
90{
91	if (buffer_put_ecpoint_ret(buffer, curve, point) == -1)
92		fatal("%s: buffer error", __func__);
93}
94
95int
96buffer_get_ecpoint_ret(Buffer *buffer, const EC_GROUP *curve,
97    EC_POINT *point)
98{
99	u_char *buf;
100	u_int len;
101	BN_CTX *bnctx;
102	int ret = -1;
103
104	if ((buf = buffer_get_string_ret(buffer, &len)) == NULL) {
105		error("%s: invalid point", __func__);
106		return -1;
107	}
108	if ((bnctx = BN_CTX_new()) == NULL)
109		fatal("%s: BN_CTX_new failed", __func__);
110	if (len > BUFFER_MAX_ECPOINT_LEN) {
111		error("%s: EC_POINT too long: %u > max %u", __func__,
112		    len, BUFFER_MAX_ECPOINT_LEN);
113		goto out;
114	}
115	if (len == 0) {
116		error("%s: EC_POINT buffer is empty", __func__);
117		goto out;
118	}
119	if (buf[0] != POINT_CONVERSION_UNCOMPRESSED) {
120		error("%s: EC_POINT is in an incorrect form: "
121		    "0x%02x (want 0x%02x)", __func__, buf[0],
122		    POINT_CONVERSION_UNCOMPRESSED);
123		goto out;
124	}
125	if (EC_POINT_oct2point(curve, point, buf, len, bnctx) != 1) {
126		error("buffer_get_bignum2_ret: BN_bin2bn failed");
127		goto out;
128	}
129	/* EC_POINT_oct2point verifies that the point is on the curve for us */
130	ret = 0;
131 out:
132	BN_CTX_free(bnctx);
133	bzero(buf, len);
134	xfree(buf);
135	return ret;
136}
137
138void
139buffer_get_ecpoint(Buffer *buffer, const EC_GROUP *curve,
140    EC_POINT *point)
141{
142	if (buffer_get_ecpoint_ret(buffer, curve, point) == -1)
143		fatal("%s: buffer error", __func__);
144}
145
146#endif /* OPENSSL_HAS_ECC */
147