src/tls/asn1.c

   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 }