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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