Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 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 | #include <sys/types.h> |
| 18 | |
| 19 | #include <openssl/bn.h> |
| 20 | #include <openssl/ec.h> |
| 21 | |
| 22 | #include <string.h> |
| 23 | #include <stdarg.h> |
| 24 | |
| 25 | #include "xmalloc.h" |
| 26 | #include "buffer.h" |
| 27 | #include "log.h" |
| 28 | #include "misc.h" |
| 29 | |
| 30 | /* |
| 31 | * Maximum supported EC GFp field length is 528 bits. SEC1 uncompressed |
| 32 | * encoding represents this as two bitstring points that should each |
| 33 | * be no longer than the field length, SEC1 specifies a 1 byte |
| 34 | * point type header. |
| 35 | * Being paranoid here may insulate us to parsing problems in |
| 36 | * EC_POINT_oct2point. |
| 37 | */ |
| 38 | #define BUFFER_MAX_ECPOINT_LEN ((528*2 / 8) + 1) |
| 39 | |
| 40 | /* |
| 41 | * Append an EC_POINT to the buffer as a string containing a SEC1 encoded |
| 42 | * uncompressed point. Fortunately OpenSSL handles the gory details for us. |
| 43 | */ |
| 44 | int |
| 45 | buffer_put_ecpoint_ret(Buffer *buffer, const EC_GROUP *curve, |
| 46 | const EC_POINT *point) |
| 47 | { |
| 48 | u_char *buf = NULL; |
| 49 | size_t len; |
| 50 | BN_CTX *bnctx; |
| 51 | int ret = -1; |
| 52 | |
| 53 | /* Determine length */ |
| 54 | if ((bnctx = BN_CTX_new()) == NULL) |
| 55 | fatal("%s: BN_CTX_new failed", __func__); |
| 56 | len = EC_POINT_point2oct(curve, point, POINT_CONVERSION_UNCOMPRESSED, |
| 57 | NULL, 0, bnctx); |
| 58 | if (len > BUFFER_MAX_ECPOINT_LEN) { |
| 59 | error("%s: giant EC point: len = %lu (max %u)", |
| 60 | __func__, (u_long)len, BUFFER_MAX_ECPOINT_LEN); |
| 61 | goto out; |
| 62 | } |
| 63 | /* Convert */ |
| 64 | buf = xmalloc(len); |
| 65 | if (EC_POINT_point2oct(curve, point, POINT_CONVERSION_UNCOMPRESSED, |
| 66 | buf, len, bnctx) != len) { |
| 67 | error("%s: EC_POINT_point2oct length mismatch", __func__); |
| 68 | goto out; |
| 69 | } |
| 70 | /* Append */ |
| 71 | buffer_put_string(buffer, buf, len); |
| 72 | ret = 0; |
| 73 | out: |
| 74 | if (buf != NULL) { |
| 75 | bzero(buf, len); |
| 76 | xfree(buf); |
| 77 | } |
| 78 | BN_CTX_free(bnctx); |
| 79 | return ret; |
| 80 | } |
| 81 | |
| 82 | void |
| 83 | buffer_put_ecpoint(Buffer *buffer, const EC_GROUP *curve, |
| 84 | const EC_POINT *point) |
| 85 | { |
| 86 | if (buffer_put_ecpoint_ret(buffer, curve, point) == -1) |
| 87 | fatal("%s: buffer error", __func__); |
| 88 | } |
| 89 | |
| 90 | int |
| 91 | buffer_get_ecpoint_ret(Buffer *buffer, const EC_GROUP *curve, |
| 92 | EC_POINT *point) |
| 93 | { |
| 94 | u_char *buf; |
| 95 | u_int len; |
| 96 | BN_CTX *bnctx; |
| 97 | int ret = -1; |
| 98 | |
| 99 | if ((buf = buffer_get_string_ret(buffer, &len)) == NULL) { |
| 100 | error("%s: invalid point", __func__); |
| 101 | return -1; |
| 102 | } |
| 103 | if ((bnctx = BN_CTX_new()) == NULL) |
| 104 | fatal("%s: BN_CTX_new failed", __func__); |
| 105 | if (len > BUFFER_MAX_ECPOINT_LEN) { |
| 106 | error("%s: EC_POINT too long: %u > max %u", __func__, |
| 107 | len, BUFFER_MAX_ECPOINT_LEN); |
| 108 | goto out; |
| 109 | } |
| 110 | if (len == 0) { |
| 111 | error("%s: EC_POINT buffer is empty", __func__); |
| 112 | goto out; |
| 113 | } |
| 114 | if (buf[0] != POINT_CONVERSION_UNCOMPRESSED) { |
| 115 | error("%s: EC_POINT is in an incorrect form: " |
| 116 | "0x%02x (want 0x%02x)", __func__, buf[0], |
| 117 | POINT_CONVERSION_UNCOMPRESSED); |
| 118 | goto out; |
| 119 | } |
| 120 | if (EC_POINT_oct2point(curve, point, buf, len, bnctx) != 1) { |
| 121 | error("buffer_get_bignum2_ret: BN_bin2bn failed"); |
| 122 | goto out; |
| 123 | } |
| 124 | /* EC_POINT_oct2point verifies that the point is on the curve for us */ |
| 125 | ret = 0; |
| 126 | out: |
| 127 | BN_CTX_free(bnctx); |
| 128 | bzero(buf, len); |
| 129 | xfree(buf); |
| 130 | return ret; |
| 131 | } |
| 132 | |
| 133 | void |
| 134 | buffer_get_ecpoint(Buffer *buffer, const EC_GROUP *curve, |
| 135 | EC_POINT *point) |
| 136 | { |
| 137 | if (buffer_get_ecpoint_ret(buffer, curve, point) == -1) |
| 138 | fatal("%s: buffer error", __func__); |
| 139 | } |
| 140 | |