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 hdr->identifier = *pos++;
35 hdr->class = hdr->identifier >> 6;
36 hdr->constructed = !!(hdr->identifier & (1 << 5));
37
38 if ((hdr->identifier & 0x1f) == 0x1f) {
39 hdr->tag = 0;
40 do {
41 if (pos >= end) {
42 wpa_printf(MSG_DEBUG, "ASN.1: Identifier "
43 "underflow");
44 return -1;
45 }
46 tmp = *pos++;
47 wpa_printf(MSG_MSGDUMP, "ASN.1: Extended tag data: "
48 "0x%02x", tmp);
49 hdr->tag = (hdr->tag << 7) | (tmp & 0x7f);
50 } while (tmp & 0x80);
51 } else
52 hdr->tag = hdr->identifier & 0x1f;
53
54 tmp = *pos++;
55 if (tmp & 0x80) {
56 if (tmp == 0xff) {
57 wpa_printf(MSG_DEBUG, "ASN.1: Reserved length "
58 "value 0xff used");
59 return -1;
60 }
61 tmp &= 0x7f; /* number of subsequent octets */
62 hdr->length = 0;
63 if (tmp > 4) {
64 wpa_printf(MSG_DEBUG, "ASN.1: Too long length field");
65 return -1;
66 }
67 while (tmp--) {
68 if (pos >= end) {
69 wpa_printf(MSG_DEBUG, "ASN.1: Length "
70 "underflow");
71 return -1;
72 }
73 hdr->length = (hdr->length << 8) | *pos++;
74 }
75 } else {
76 /* Short form - length 0..127 in one octet */
77 hdr->length = tmp;
78 }
79
80 if (end < pos || hdr->length > (unsigned int) (end - pos)) {
81 wpa_printf(MSG_DEBUG, "ASN.1: Contents underflow");
82 return -1;
83 }
84
85 hdr->payload = pos;
86 return 0;
87 }
88
89
asn1_parse_oid(const u8 * buf,size_t len,struct asn1_oid * oid)90 int asn1_parse_oid(const u8 *buf, size_t len, struct asn1_oid *oid)
91 {
92 const u8 *pos, *end;
93 unsigned long val;
94 u8 tmp;
95
96 os_memset(oid, 0, sizeof(*oid));
97
98 pos = buf;
99 end = buf + len;
100
101 while (pos < end) {
102 val = 0;
103
104 do {
105 if (pos >= end)
106 return -1;
107 tmp = *pos++;
108 val = (val << 7) | (tmp & 0x7f);
109 } while (tmp & 0x80);
110
111 if (oid->len >= ASN1_MAX_OID_LEN) {
112 wpa_printf(MSG_DEBUG, "ASN.1: Too long OID value");
113 return -1;
114 }
115 if (oid->len == 0) {
116 /*
117 * The first octet encodes the first two object
118 * identifier components in (X*40) + Y formula.
119 * X = 0..2.
120 */
121 oid->oid[0] = val / 40;
122 if (oid->oid[0] > 2)
123 oid->oid[0] = 2;
124 oid->oid[1] = val - oid->oid[0] * 40;
125 oid->len = 2;
126 } else
127 oid->oid[oid->len++] = val;
128 }
129
130 return 0;
131 }
132
133
asn1_get_oid(const u8 * buf,size_t len,struct asn1_oid * oid,const u8 ** next)134 int asn1_get_oid(const u8 *buf, size_t len, struct asn1_oid *oid,
135 const u8 **next)
136 {
137 struct asn1_hdr hdr;
138
139 if (asn1_get_next(buf, len, &hdr) < 0 || hdr.length == 0)
140 return -1;
141
142 if (hdr.class != ASN1_CLASS_UNIVERSAL || hdr.tag != ASN1_TAG_OID) {
143 wpa_printf(MSG_DEBUG, "ASN.1: Expected OID - found class %d "
144 "tag 0x%x", hdr.class, hdr.tag);
145 return -1;
146 }
147
148 *next = hdr.payload + hdr.length;
149
150 return asn1_parse_oid(hdr.payload, hdr.length, oid);
151 }
152
153
asn1_oid_to_str(const struct asn1_oid * oid,char * buf,size_t len)154 void asn1_oid_to_str(const struct asn1_oid *oid, char *buf, size_t len)
155 {
156 char *pos = buf;
157 size_t i;
158 int ret;
159
160 if (len == 0)
161 return;
162
163 buf[0] = '\0';
164
165 for (i = 0; i < oid->len; i++) {
166 ret = os_snprintf(pos, buf + len - pos,
167 "%s%lu",
168 i == 0 ? "" : ".", oid->oid[i]);
169 if (os_snprintf_error(buf + len - pos, ret))
170 break;
171 pos += ret;
172 }
173 buf[len - 1] = '\0';
174 }
175
176
rotate_bits(u8 octet)177 static u8 rotate_bits(u8 octet)
178 {
179 int i;
180 u8 res;
181
182 res = 0;
183 for (i = 0; i < 8; i++) {
184 res <<= 1;
185 if (octet & 1)
186 res |= 1;
187 octet >>= 1;
188 }
189
190 return res;
191 }
192
193
asn1_bit_string_to_long(const u8 * buf,size_t len)194 unsigned long asn1_bit_string_to_long(const u8 *buf, size_t len)
195 {
196 unsigned long val = 0;
197 const u8 *pos = buf;
198
199 /* BER requires that unused bits are zero, so we can ignore the number
200 * of unused bits */
201 pos++;
202
203 if (len >= 2)
204 val |= rotate_bits(*pos++);
205 if (len >= 3)
206 val |= ((unsigned long) rotate_bits(*pos++)) << 8;
207 if (len >= 4)
208 val |= ((unsigned long) rotate_bits(*pos++)) << 16;
209 if (len >= 5)
210 val |= ((unsigned long) rotate_bits(*pos++)) << 24;
211 if (len >= 6)
212 wpa_printf(MSG_DEBUG, "X509: %s - some bits ignored "
213 "(BIT STRING length %lu)",
214 __func__, (unsigned long) len);
215
216 return val;
217 }
218
219
asn1_oid_equal(const struct asn1_oid * a,const struct asn1_oid * b)220 int asn1_oid_equal(const struct asn1_oid *a, const struct asn1_oid *b)
221 {
222 size_t i;
223
224 if (a->len != b->len)
225 return 0;
226
227 for (i = 0; i < a->len; i++) {
228 if (a->oid[i] != b->oid[i])
229 return 0;
230 }
231
232 return 1;
233 }
234