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
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
|
/* Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
This program 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 3 of the License, or
(at your option) any later version.
This program 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, see <http://www.gnu.org/licenses/>.
*/
#include <stdbool.h>
#include "libdnssec/shared/bignum.h"
#include "libdnssec/binary.h"
#include "libdnssec/error.h"
#include "libdnssec/sign/der.h"
#include "libdnssec/shared/binary_wire.h"
/*
* In fact, this is a very tiny subset of ASN.1 encoding format implementation,
* which is necessary for the purpose of DNSSEC.
*
* References: RFC 3279 (X.509 PKI), X.690, RFC 6605 (ECDSA), RFC8080 (EDDSA)
*
* Dss-Sig-Value ::= SEQUENCE { r INTEGER, s INTEGER }
*/
#define ASN1_TYPE_SEQUENCE 0x30
#define ASN1_TYPE_INTEGER 0x02
#define ASN1_MAX_SIZE 127
/*!
* Check if the next object has a given type.
*/
static bool asn1_expect_type(wire_ctx_t *wire, uint8_t type)
{
assert(wire);
return (wire_ctx_available(wire) >= 1 && wire_ctx_read_u8(wire) == type);
}
/*!
* Decode the size of the object (only short format is supported).
*/
static int asn1_decode_size(wire_ctx_t *wire, size_t *size)
{
assert(wire);
assert(size);
if (wire_ctx_available(wire) < 1) {
return DNSSEC_MALFORMED_DATA;
}
uint8_t byte = wire_ctx_read_u8(wire);
if (byte & 0x80) {
// long form, we do not need it for DNSSEC
return DNSSEC_NOT_IMPLEMENTED_ERROR;
}
*size = byte;
return DNSSEC_EOK;
}
/*!
* Decode an unsigned integer object.
*/
static int asn1_decode_integer(wire_ctx_t *wire, dnssec_binary_t *_value)
{
assert(wire);
assert(_value);
if (!asn1_expect_type(wire, ASN1_TYPE_INTEGER)) {
return DNSSEC_MALFORMED_DATA;
}
size_t size;
int result = asn1_decode_size(wire, &size);
if (result != DNSSEC_EOK) {
return result;
}
if (size == 0 || size > wire_ctx_available(wire)) {
return DNSSEC_MALFORMED_DATA;
}
dnssec_binary_t value = { .data = wire->position, .size = size };
wire->position += size;
// skip leading zeroes (unless equal to zero)
while (value.size > 1 && value.data[0] == 0) {
value.data += 1;
value.size -= 1;
}
*_value = value;
return DNSSEC_EOK;
}
/*!
* Encode object header (type and length).
*/
static void asn1_write_header(wire_ctx_t *wire, uint8_t type, size_t length)
{
assert(wire);
assert(length < ASN1_MAX_SIZE);
wire_ctx_write_u8(wire, type);
wire_ctx_write_u8(wire, length);
}
/*!
* Encode unsigned integer object.
*/
static void asn1_write_integer(wire_ctx_t *wire, size_t integer_size,
const dnssec_binary_t *integer)
{
assert(wire);
assert(integer);
assert(integer->data);
asn1_write_header(wire, ASN1_TYPE_INTEGER, integer_size);
bignum_write(wire, integer_size, integer);
}
/*!
* Decode signature parameters from X.509 ECDSA signature.
*/
int dss_sig_value_decode(const dnssec_binary_t *der,
dnssec_binary_t *r, dnssec_binary_t *s)
{
if (!der || !der->data || !r || !s) {
return DNSSEC_EINVAL;
}
wire_ctx_t wire = binary_init(der);
size_t size;
int result;
// decode the sequence
if (!asn1_expect_type(&wire, ASN1_TYPE_SEQUENCE)) {
return DNSSEC_MALFORMED_DATA;
}
result = asn1_decode_size(&wire, &size);
if (result != DNSSEC_EOK) {
return result;
}
if (size != wire_ctx_available(&wire)) {
return DNSSEC_MALFORMED_DATA;
}
// decode the 'r' and 's' values
dnssec_binary_t der_r;
result = asn1_decode_integer(&wire, &der_r);
if (result != DNSSEC_EOK) {
return result;
}
dnssec_binary_t der_s;
result = asn1_decode_integer(&wire, &der_s);
if (result != DNSSEC_EOK) {
return result;
}
if (wire_ctx_available(&wire) != 0) {
return DNSSEC_MALFORMED_DATA;
}
*r = der_r;
*s = der_s;
return DNSSEC_EOK;
}
/*!
* Encode signature parameters from X.509 ECDSA signature.
*/
int dss_sig_value_encode(const dnssec_binary_t *r, const dnssec_binary_t *s,
dnssec_binary_t *der)
{
if (!r || !r->data || !s || !s->data || !der) {
return DNSSEC_EINVAL;
}
size_t r_size = bignum_size_s(r);
size_t s_size = bignum_size_s(s);
// check supported inputs range
if (r_size > ASN1_MAX_SIZE || s_size > ASN1_MAX_SIZE) {
return DNSSEC_NOT_IMPLEMENTED_ERROR;
}
size_t seq_size = 2 + r_size + 2 + s_size;
if (seq_size > ASN1_MAX_SIZE) {
return DNSSEC_NOT_IMPLEMENTED_ERROR;
}
// encode result
size_t total_size = 2 + seq_size;
dnssec_binary_t _der = { 0 };
if (dnssec_binary_alloc(&_der, total_size)) {
return DNSSEC_ENOMEM;
}
wire_ctx_t wire = binary_init(&_der);
asn1_write_header(&wire, ASN1_TYPE_SEQUENCE, seq_size);
asn1_write_integer(&wire, r_size, r);
asn1_write_integer(&wire, s_size, s);
assert(wire_ctx_available(&wire) == 0);
*der = _der;
return DNSSEC_EOK;
}
|
