1 /* 2 * ASN.1 DER parsing 3 * Copyright (c) 2006, Jouni Malinen <j@w1.fi> 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License version 2 as 7 * published by the Free Software Foundation. 8 * 9 * Alternatively, this software may be distributed under the terms of BSD 10 * license. 11 * 12 * See README and COPYING for more details. 13 */ 14 15 #include "includes.h" 16 17 #include "common.h" 18 #include "asn1.h" 19 20 int asn1_get_next(const u8 *buf, size_t len, struct asn1_hdr *hdr) 21 { 22 const u8 *pos, *end; 23 u8 tmp; 24 25 os_memset(hdr, 0, sizeof(*hdr)); 26 pos = buf; 27 end = buf + len; 28 29 hdr->identifier = *pos++; 30 hdr->class = hdr->identifier >> 6; 31 hdr->constructed = !!(hdr->identifier & (1 << 5)); 32 33 if ((hdr->identifier & 0x1f) == 0x1f) { 34 hdr->tag = 0; 35 do { 36 if (pos >= end) { 37 wpa_printf(MSG_DEBUG, "ASN.1: Identifier " 38 "underflow"); 39 return -1; 40 } 41 tmp = *pos++; 42 wpa_printf(MSG_MSGDUMP, "ASN.1: Extended tag data: " 43 "0x%02x", tmp); 44 hdr->tag = (hdr->tag << 7) | (tmp & 0x7f); 45 } while (tmp & 0x80); 46 } else 47 hdr->tag = hdr->identifier & 0x1f; 48 49 tmp = *pos++; 50 if (tmp & 0x80) { 51 if (tmp == 0xff) { 52 wpa_printf(MSG_DEBUG, "ASN.1: Reserved length " 53 "value 0xff used"); 54 return -1; 55 } 56 tmp &= 0x7f; /* number of subsequent octets */ 57 hdr->length = 0; 58 if (tmp > 4) { 59 wpa_printf(MSG_DEBUG, "ASN.1: Too long length field"); 60 return -1; 61 } 62 while (tmp--) { 63 if (pos >= end) { 64 wpa_printf(MSG_DEBUG, "ASN.1: Length " 65 "underflow"); 66 return -1; 67 } 68 hdr->length = (hdr->length << 8) | *pos++; 69 } 70 } else { 71 /* Short form - length 0..127 in one octet */ 72 hdr->length = tmp; 73 } 74 75 if (end < pos || hdr->length > (unsigned int) (end - pos)) { 76 wpa_printf(MSG_DEBUG, "ASN.1: Contents underflow"); 77 return -1; 78 } 79 80 hdr->payload = pos; 81 return 0; 82 } 83 84 85 int asn1_parse_oid(const u8 *buf, size_t len, struct asn1_oid *oid) 86 { 87 const u8 *pos, *end; 88 unsigned long val; 89 u8 tmp; 90 91 os_memset(oid, 0, sizeof(*oid)); 92 93 pos = buf; 94 end = buf + len; 95 96 while (pos < end) { 97 val = 0; 98 99 do { 100 if (pos >= end) 101 return -1; 102 tmp = *pos++; 103 val = (val << 7) | (tmp & 0x7f); 104 } while (tmp & 0x80); 105 106 if (oid->len >= ASN1_MAX_OID_LEN) { 107 wpa_printf(MSG_DEBUG, "ASN.1: Too long OID value"); 108 return -1; 109 } 110 if (oid->len == 0) { 111 /* 112 * The first octet encodes the first two object 113 * identifier components in (X*40) + Y formula. 114 * X = 0..2. 115 */ 116 oid->oid[0] = val / 40; 117 if (oid->oid[0] > 2) 118 oid->oid[0] = 2; 119 oid->oid[1] = val - oid->oid[0] * 40; 120 oid->len = 2; 121 } else 122 oid->oid[oid->len++] = val; 123 } 124 125 return 0; 126 } 127 128 129 int asn1_get_oid(const u8 *buf, size_t len, struct asn1_oid *oid, 130 const u8 **next) 131 { 132 struct asn1_hdr hdr; 133 134 if (asn1_get_next(buf, len, &hdr) < 0 || hdr.length == 0) 135 return -1; 136 137 if (hdr.class != ASN1_CLASS_UNIVERSAL || hdr.tag != ASN1_TAG_OID) { 138 wpa_printf(MSG_DEBUG, "ASN.1: Expected OID - found class %d " 139 "tag 0x%x", hdr.class, hdr.tag); 140 return -1; 141 } 142 143 *next = hdr.payload + hdr.length; 144 145 return asn1_parse_oid(hdr.payload, hdr.length, oid); 146 } 147 148 149 void asn1_oid_to_str(struct asn1_oid *oid, char *buf, size_t len) 150 { 151 char *pos = buf; 152 size_t i; 153 int ret; 154 155 if (len == 0) 156 return; 157 158 buf[0] = '\0'; 159 160 for (i = 0; i < oid->len; i++) { 161 ret = os_snprintf(pos, buf + len - pos, 162 "%s%lu", 163 i == 0 ? "" : ".", oid->oid[i]); 164 if (ret < 0 || ret >= buf + len - pos) 165 break; 166 pos += ret; 167 } 168 buf[len - 1] = '\0'; 169 } 170 171 172 static u8 rotate_bits(u8 octet) 173 { 174 int i; 175 u8 res; 176 177 res = 0; 178 for (i = 0; i < 8; i++) { 179 res <<= 1; 180 if (octet & 1) 181 res |= 1; 182 octet >>= 1; 183 } 184 185 return res; 186 } 187 188 189 unsigned long asn1_bit_string_to_long(const u8 *buf, size_t len) 190 { 191 unsigned long val = 0; 192 const u8 *pos = buf; 193 194 /* BER requires that unused bits are zero, so we can ignore the number 195 * of unused bits */ 196 pos++; 197 198 if (len >= 2) 199 val |= rotate_bits(*pos++); 200 if (len >= 3) 201 val |= ((unsigned long) rotate_bits(*pos++)) << 8; 202 if (len >= 4) 203 val |= ((unsigned long) rotate_bits(*pos++)) << 16; 204 if (len >= 5) 205 val |= ((unsigned long) rotate_bits(*pos++)) << 24; 206 if (len >= 6) 207 wpa_printf(MSG_DEBUG, "X509: %s - some bits ignored " 208 "(BIT STRING length %lu)", 209 __func__, (unsigned long) len); 210 211 return val; 212 } 213