contrib/wpa_supplicant-0.5.8/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
  19 #ifdef CONFIG_INTERNAL_X509
  20
  21 #include "asn1.h"
  22
  23 int asn1_get_next(const u8 *buf, size_t len, struct asn1_hdr *hdr)
  24 {
  25         const u8 *pos, *end;
  26         u8 tmp;
  27
  28         os_memset(hdr, 0, sizeof(*hdr));
  29         pos = buf;
  30         end = buf + len;
  31
  32         hdr->identifier = *pos++;
  33         hdr->class = hdr->identifier >> 6;
  34         hdr->constructed = !!(hdr->identifier & (1 << 5));
  35
  36         if ((hdr->identifier & 0x1f) == 0x1f) {
  37                 hdr->tag = 0;
  38                 do {
  39                         if (pos >= end) {
  40                                 wpa_printf(MSG_DEBUG, "ASN.1: Identifier "
  41                                            "underflow");
  42                                 return -1;
  43                         }
  44                         tmp = *pos++;
  45                         wpa_printf(MSG_MSGDUMP, "ASN.1: Extended tag data: "
  46                                    "0x%02x", tmp);
  47                         hdr->tag = (hdr->tag << 7) | (tmp & 0x7f);
  48                 } while (tmp & 0x80);
  49         } else
  50                 hdr->tag = hdr->identifier & 0x1f;
  51
  52         tmp = *pos++;
  53         if (tmp & 0x80) {
  54                 if (tmp == 0xff) {
  55                         wpa_printf(MSG_DEBUG, "ASN.1: Reserved length "
  56                                    "value 0xff used");
  57                         return -1;
  58                 }
  59                 tmp &= 0x7f; /* number of subsequent octets */
  60                 hdr->length = 0;
  61                 while (tmp--) {
  62                         if (pos >= end) {
  63                                 wpa_printf(MSG_DEBUG, "ASN.1: Length "
  64                                            "underflow");
  65                                 return -1;
  66                         }
  67                         hdr->length = (hdr->length << 8) | *pos++;
  68                 }
  69         } else {
  70                 /* Short form - length 0..127 in one octet */
  71                 hdr->length = tmp;
  72         }
  73
  74         if (pos + hdr->length > end) {
  75                 wpa_printf(MSG_DEBUG, "ASN.1: Contents underflow");
  76                 return -1;
  77         }
  78
  79         hdr->payload = pos;
  80         return 0;
  81 }
  82
  83
  84 int asn1_get_oid(const u8 *buf, size_t len, struct asn1_oid *oid,
  85                  const u8 **next)
  86 {
  87         struct asn1_hdr hdr;
  88         const u8 *pos, *end;
  89         unsigned long val;
  90         u8 tmp;
  91
  92         os_memset(oid, 0, sizeof(*oid));
  93
  94         if (asn1_get_next(buf, len, &hdr) < 0 || hdr.length == 0)
  95                 return -1;
  96
  97         if (hdr.class != ASN1_CLASS_UNIVERSAL || hdr.tag != ASN1_TAG_OID) {
  98                 wpa_printf(MSG_DEBUG, "ASN.1: Expected OID - found class %d "
  99                            "tag 0x%x", hdr.class, hdr.tag);
 100                 return -1;
 101         }
 102
 103         pos = hdr.payload;
 104         end = hdr.payload + hdr.length;
 105         *next = end;
 106
 107         while (pos < end) {
 108                 val = 0;
 109
 110                 do {
 111                         if (pos >= end)
 112                                 return -1;
 113                         tmp = *pos++;
 114                         val = (val << 7) | (tmp & 0x7f);
 115                 } while (tmp & 0x80);
 116
 117                 if (oid->len >= ASN1_MAX_OID_LEN) {
 118                         wpa_printf(MSG_DEBUG, "ASN.1: Too long OID value");
 119                         return -1;
 120                 }
 121                 if (oid->len == 0) {
 122                         /*
 123                          * The first octet encodes the first two object
 124                          * identifier components in (X*40) + Y formula.
 125                          * X = 0..2.
 126                          */
 127                         oid->oid[0] = val / 40;
 128                         if (oid->oid[0] > 2)
 129                                 oid->oid[0] = 2;
 130                         oid->oid[1] = val - oid->oid[0] * 40;
 131                         oid->len = 2;
 132                 } else
 133                         oid->oid[oid->len++] = val;
 134         }
 135
 136         return 0;
 137 }
 138
 139
 140 void asn1_oid_to_str(struct asn1_oid *oid, char *buf, size_t len)
 141 {
 142         char *pos = buf;
 143         size_t i;
 144         int ret;
 145
 146         if (len == 0)
 147                 return;
 148
 149         buf[0] = '\0';
 150
 151         for (i = 0; i < oid->len; i++) {
 152                 ret = os_snprintf(pos, buf + len - pos,
 153                                   "%s%lu",
 154                                   i == 0 ? "" : ".", oid->oid[i]);
 155                 if (ret < 0 || ret >= buf + len - pos)
 156                         break;
 157                 pos += ret;
 158         }
 159         buf[len - 1] = '\0';
 160 }
 161
 162
 163 static u8 rotate_bits(u8 octet)
 164 {
 165         int i;
 166         u8 res;
 167
 168         res = 0;
 169         for (i = 0; i < 8; i++) {
 170                 res <<= 1;
 171                 if (octet & 1)
 172                         res |= 1;
 173                 octet >>= 1;
 174         }
 175
 176         return res;
 177 }
 178
 179
 180 unsigned long asn1_bit_string_to_long(const u8 *buf, size_t len)
 181 {
 182         unsigned long val = 0;
 183         const u8 *pos = buf;
 184
 185         /* BER requires that unused bits are zero, so we can ignore the number
 186          * of unused bits */
 187         pos++;
 188
 189         if (len >= 2)
 190                 val |= rotate_bits(*pos++);
 191         if (len >= 3)
 192                 val |= ((unsigned long) rotate_bits(*pos++)) << 8;
 193         if (len >= 4)
 194                 val |= ((unsigned long) rotate_bits(*pos++)) << 16;
 195         if (len >= 5)
 196                 val |= ((unsigned long) rotate_bits(*pos++)) << 24;
 197         if (len >= 6)
 198                 wpa_printf(MSG_DEBUG, "X509: %s - some bits ignored "
 199                            "(BIT STRING length %lu)",
 200                            __func__, (unsigned long) len);
 201
 202         return val;
 203 }
 204
 205 #endif /* CONFIG_INTERNAL_X509 */