1 /* 2 * ASN.1 DER parsing 3 * Copyright (c) 2006-2014, Jouni Malinen <j (at) 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 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 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 } 132 133 134 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 } 152 153 154 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 } 175 176 177 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 } 192 193 194 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 } 218 219 220 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
