1 /*
2 * ASN.1 DER parsing
3 * Copyright (c) 2006-2014, Jouni Malinen <j@w1.fi>
4 *
5 * This software may be distributed under the terms of the BSD license.
6 * See README for more details.
7 */
8
9 #include "includes.h"
10
11 #include "common.h"
12 #include "asn1.h"
13
14 struct asn1_oid asn1_sha1_oid = {
15 .oid = { 1, 3, 14, 3, 2, 26 },
16 .len = 6
17 };
18
19 struct asn1_oid asn1_sha256_oid = {
20 .oid = { 2, 16, 840, 1, 101, 3, 4, 2, 1 },
21 .len = 9
22 };
23
24
asn1_get_next(const u8 * buf,size_t len,struct asn1_hdr * hdr)25 int asn1_get_next(const u8 *buf, size_t len, struct asn1_hdr *hdr)
26 {
27 const u8 *pos, *end;
28 u8 tmp;
29
30 os_memset(hdr, 0, sizeof(*hdr));
31 pos = buf;
32 end = buf + len;
33
34 if (pos >= end) {
35 wpa_printf(MSG_DEBUG, "ASN.1: No room for Identifier");
36 return -1;
37 }
38 hdr->identifier = *pos++;
39 hdr->class = hdr->identifier >> 6;
40 hdr->constructed = !!(hdr->identifier & (1 << 5));
41
42 if ((hdr->identifier & 0x1f) == 0x1f) {
43 hdr->tag = 0;
44 do {
45 if (pos >= end) {
46 wpa_printf(MSG_DEBUG, "ASN.1: Identifier "
47 "underflow");
48 return -1;
49 }
50 tmp = *pos++;
51 wpa_printf(MSG_MSGDUMP, "ASN.1: Extended tag data: "
52 "0x%02x", tmp);
53 hdr->tag = (hdr->tag << 7) | (tmp & 0x7f);
54 } while (tmp & 0x80);
55 } else
56 hdr->tag = hdr->identifier & 0x1f;
57
58 if (pos >= end) {
59 wpa_printf(MSG_DEBUG, "ASN.1: No room for Length");
60 return -1;
61 }
62 tmp = *pos++;
63 if (tmp & 0x80) {
64 if (tmp == 0xff) {
65 wpa_printf(MSG_DEBUG, "ASN.1: Reserved length "
66 "value 0xff used");
67 return -1;
68 }
69 tmp &= 0x7f; /* number of subsequent octets */
70 hdr->length = 0;
71 if (tmp > 4) {
72 wpa_printf(MSG_DEBUG, "ASN.1: Too long length field");
73 return -1;
74 }
75 while (tmp--) {
76 if (pos >= end) {
77 wpa_printf(MSG_DEBUG, "ASN.1: Length "
78 "underflow");
79 return -1;
80 }
81 hdr->length = (hdr->length << 8) | *pos++;
82 }
83 } else {
84 /* Short form - length 0..127 in one octet */
85 hdr->length = tmp;
86 }
87
88 if (end < pos || hdr->length > (unsigned int) (end - pos)) {
89 wpa_printf(MSG_DEBUG, "ASN.1: Contents underflow");
90 return -1;
91 }
92
93 hdr->payload = pos;
94 return 0;
95 }
96
97
asn1_parse_oid(const u8 * buf,size_t len,struct asn1_oid * oid)98 int asn1_parse_oid(const u8 *buf, size_t len, struct asn1_oid *oid)
99 {
100 const u8 *pos, *end;
101 unsigned long val;
102 u8 tmp;
103
104 os_memset(oid, 0, sizeof(*oid));
105
106 pos = buf;
107 end = buf + len;
108
109 while (pos < end) {
110 val = 0;
111
112 do {
113 if (pos >= end)
114 return -1;
115 tmp = *pos++;
116 val = (val << 7) | (tmp & 0x7f);
117 } while (tmp & 0x80);
118
119 if (oid->len >= ASN1_MAX_OID_LEN) {
120 wpa_printf(MSG_DEBUG, "ASN.1: Too long OID value");
121 return -1;
122 }
123 if (oid->len == 0) {
124 /*
125 * The first octet encodes the first two object
126 * identifier components in (X*40) + Y formula.
127 * X = 0..2.
128 */
129 oid->oid[0] = val / 40;
130 if (oid->oid[0] > 2)
131 oid->oid[0] = 2;
132 oid->oid[1] = val - oid->oid[0] * 40;
133 oid->len = 2;
134 } else
135 oid->oid[oid->len++] = val;
136 }
137
138 return 0;
139 }
140
141
asn1_get_oid(const u8 * buf,size_t len,struct asn1_oid * oid,const u8 ** next)142 int asn1_get_oid(const u8 *buf, size_t len, struct asn1_oid *oid,
143 const u8 **next)
144 {
145 struct asn1_hdr hdr;
146
147 if (asn1_get_next(buf, len, &hdr) < 0 || hdr.length == 0)
148 return -1;
149
150 if (hdr.class != ASN1_CLASS_UNIVERSAL || hdr.tag != ASN1_TAG_OID) {
151 wpa_printf(MSG_DEBUG, "ASN.1: Expected OID - found class %d "
152 "tag 0x%x", hdr.class, hdr.tag);
153 return -1;
154 }
155
156 *next = hdr.payload + hdr.length;
157
158 return asn1_parse_oid(hdr.payload, hdr.length, oid);
159 }
160
161
asn1_oid_to_str(const struct asn1_oid * oid,char * buf,size_t len)162 void asn1_oid_to_str(const struct asn1_oid *oid, char *buf, size_t len)
163 {
164 char *pos = buf;
165 size_t i;
166 int ret;
167
168 if (len == 0)
169 return;
170
171 buf[0] = '\0';
172
173 for (i = 0; i < oid->len; i++) {
174 ret = os_snprintf(pos, buf + len - pos,
175 "%s%lu",
176 i == 0 ? "" : ".", oid->oid[i]);
177 if (os_snprintf_error(buf + len - pos, ret))
178 break;
179 pos += ret;
180 }
181 buf[len - 1] = '\0';
182 }
183
184
rotate_bits(u8 octet)185 static u8 rotate_bits(u8 octet)
186 {
187 int i;
188 u8 res;
189
190 res = 0;
191 for (i = 0; i < 8; i++) {
192 res <<= 1;
193 if (octet & 1)
194 res |= 1;
195 octet >>= 1;
196 }
197
198 return res;
199 }
200
201
asn1_bit_string_to_long(const u8 * buf,size_t len)202 unsigned long asn1_bit_string_to_long(const u8 *buf, size_t len)
203 {
204 unsigned long val = 0;
205 const u8 *pos = buf;
206
207 /* BER requires that unused bits are zero, so we can ignore the number
208 * of unused bits */
209 pos++;
210
211 if (len >= 2)
212 val |= rotate_bits(*pos++);
213 if (len >= 3)
214 val |= ((unsigned long) rotate_bits(*pos++)) << 8;
215 if (len >= 4)
216 val |= ((unsigned long) rotate_bits(*pos++)) << 16;
217 if (len >= 5)
218 val |= ((unsigned long) rotate_bits(*pos++)) << 24;
219 if (len >= 6)
220 wpa_printf(MSG_DEBUG, "X509: %s - some bits ignored "
221 "(BIT STRING length %lu)",
222 __func__, (unsigned long) len);
223
224 return val;
225 }
226
227
asn1_oid_equal(const struct asn1_oid * a,const struct asn1_oid * b)228 int asn1_oid_equal(const struct asn1_oid *a, const struct asn1_oid *b)
229 {
230 size_t i;
231
232 if (a->len != b->len)
233 return 0;
234
235 for (i = 0; i < a->len; i++) {
236 if (a->oid[i] != b->oid[i])
237 return 0;
238 }
239
240 return 1;
241 }
242