asn1.c
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00001 /*
00002  * ASN.1 DER parsing
00003  * Copyright (c) 2006, Jouni Malinen <j@w1.fi>
00004  *
00005  * This program is free software; you can redistribute it and/or modify
00006  * it under the terms of the GNU General Public License version 2 as
00007  * published by the Free Software Foundation.
00008  *
00009  * Alternatively, this software may be distributed under the terms of BSD
00010  * license.
00011  *
00012  * See README and COPYING for more details.
00013  */
00014 
00015 #include "includes.h"
00016 
00017 #include "common.h"
00018 #include "asn1.h"
00019 
00020 int asn1_get_next(const u8 *buf, size_t len, struct asn1_hdr *hdr)
00021 {
00022         const u8 *pos, *end;
00023         u8 tmp;
00024 
00025         os_memset(hdr, 0, sizeof(*hdr));
00026         pos = buf;
00027         end = buf + len;
00028 
00029         hdr->identifier = *pos++;
00030         hdr->class = hdr->identifier >> 6;
00031         hdr->constructed = !!(hdr->identifier & (1 << 5));
00032 
00033         if ((hdr->identifier & 0x1f) == 0x1f) {
00034                 hdr->tag = 0;
00035                 do {
00036                         if (pos >= end) {
00037                                 wpa_printf(MSG_DEBUG, "ASN.1: Identifier "
00038                                            "underflow");
00039                                 return -1;
00040                         }
00041                         tmp = *pos++;
00042                         wpa_printf(MSG_MSGDUMP, "ASN.1: Extended tag data: "
00043                                    "0x%02x", tmp);
00044                         hdr->tag = (hdr->tag << 7) | (tmp & 0x7f);
00045                 } while (tmp & 0x80);
00046         } else
00047                 hdr->tag = hdr->identifier & 0x1f;
00048 
00049         tmp = *pos++;
00050         if (tmp & 0x80) {
00051                 if (tmp == 0xff) {
00052                         wpa_printf(MSG_DEBUG, "ASN.1: Reserved length "
00053                                    "value 0xff used");
00054                         return -1;
00055                 }
00056                 tmp &= 0x7f; /* number of subsequent octets */
00057                 hdr->length = 0;
00058                 if (tmp > 4) {
00059                         wpa_printf(MSG_DEBUG, "ASN.1: Too long length field");
00060                         return -1;
00061                 }
00062                 while (tmp--) {
00063                         if (pos >= end) {
00064                                 wpa_printf(MSG_DEBUG, "ASN.1: Length "
00065                                            "underflow");
00066                                 return -1;
00067                         }
00068                         hdr->length = (hdr->length << 8) | *pos++;
00069                 }
00070         } else {
00071                 /* Short form - length 0..127 in one octet */
00072                 hdr->length = tmp;
00073         }
00074 
00075         if (end < pos || hdr->length > (unsigned int) (end - pos)) {
00076                 wpa_printf(MSG_DEBUG, "ASN.1: Contents underflow");
00077                 return -1;
00078         }
00079 
00080         hdr->payload = pos;
00081         return 0;
00082 }
00083 
00084 
00085 int asn1_parse_oid(const u8 *buf, size_t len, struct asn1_oid *oid)
00086 {
00087         const u8 *pos, *end;
00088         unsigned long val;
00089         u8 tmp;
00090 
00091         os_memset(oid, 0, sizeof(*oid));
00092 
00093         pos = buf;
00094         end = buf + len;
00095 
00096         while (pos < end) {
00097                 val = 0;
00098 
00099                 do {
00100                         if (pos >= end)
00101                                 return -1;
00102                         tmp = *pos++;
00103                         val = (val << 7) | (tmp & 0x7f);
00104                 } while (tmp & 0x80);
00105 
00106                 if (oid->len >= ASN1_MAX_OID_LEN) {
00107                         wpa_printf(MSG_DEBUG, "ASN.1: Too long OID value");
00108                         return -1;
00109                 }
00110                 if (oid->len == 0) {
00111                         /*
00112                          * The first octet encodes the first two object
00113                          * identifier components in (X*40) + Y formula.
00114                          * X = 0..2.
00115                          */
00116                         oid->oid[0] = val / 40;
00117                         if (oid->oid[0] > 2)
00118                                 oid->oid[0] = 2;
00119                         oid->oid[1] = val - oid->oid[0] * 40;
00120                         oid->len = 2;
00121                 } else
00122                         oid->oid[oid->len++] = val;
00123         }
00124 
00125         return 0;
00126 }
00127 
00128 
00129 int asn1_get_oid(const u8 *buf, size_t len, struct asn1_oid *oid,
00130                  const u8 **next)
00131 {
00132         struct asn1_hdr hdr;
00133 
00134         if (asn1_get_next(buf, len, &hdr) < 0 || hdr.length == 0)
00135                 return -1;
00136 
00137         if (hdr.class != ASN1_CLASS_UNIVERSAL || hdr.tag != ASN1_TAG_OID) {
00138                 wpa_printf(MSG_DEBUG, "ASN.1: Expected OID - found class %d "
00139                            "tag 0x%x", hdr.class, hdr.tag);
00140                 return -1;
00141         }
00142 
00143         *next = hdr.payload + hdr.length;
00144 
00145         return asn1_parse_oid(hdr.payload, hdr.length, oid);
00146 }
00147 
00148 
00149 void asn1_oid_to_str(struct asn1_oid *oid, char *buf, size_t len)
00150 {
00151         char *pos = buf;
00152         size_t i;
00153         int ret;
00154 
00155         if (len == 0)
00156                 return;
00157 
00158         buf[0] = '\0';
00159 
00160         for (i = 0; i < oid->len; i++) {
00161                 ret = os_snprintf(pos, buf + len - pos,
00162                                   "%s%lu",
00163                                   i == 0 ? "" : ".", oid->oid[i]);
00164                 if (ret < 0 || ret >= buf + len - pos)
00165                         break;
00166                 pos += ret;
00167         }
00168         buf[len - 1] = '\0';
00169 }
00170 
00171 
00172 static u8 rotate_bits(u8 octet)
00173 {
00174         int i;
00175         u8 res;
00176 
00177         res = 0;
00178         for (i = 0; i < 8; i++) {
00179                 res <<= 1;
00180                 if (octet & 1)
00181                         res |= 1;
00182                 octet >>= 1;
00183         }
00184 
00185         return res;
00186 }
00187 
00188 
00189 unsigned long asn1_bit_string_to_long(const u8 *buf, size_t len)
00190 {
00191         unsigned long val = 0;
00192         const u8 *pos = buf;
00193 
00194         /* BER requires that unused bits are zero, so we can ignore the number
00195          * of unused bits */
00196         pos++;
00197 
00198         if (len >= 2)
00199                 val |= rotate_bits(*pos++);
00200         if (len >= 3)
00201                 val |= ((unsigned long) rotate_bits(*pos++)) << 8;
00202         if (len >= 4)
00203                 val |= ((unsigned long) rotate_bits(*pos++)) << 16;
00204         if (len >= 5)
00205                 val |= ((unsigned long) rotate_bits(*pos++)) << 24;
00206         if (len >= 6)
00207                 wpa_printf(MSG_DEBUG, "X509: %s - some bits ignored "
00208                            "(BIT STRING length %lu)",
00209                            __func__, (unsigned long) len);
00210 
00211         return val;
00212 }


wpa_supplicant
Author(s): Package maintained by Blaise Gassend
autogenerated on Thu Apr 24 2014 15:34:33