lib/krb5/rd_safe.c

   1 /*
   2  * Copyright (c) 1997 - 2003 Kungliga Tekniska Högskolan
   3  * (Royal Institute of Technology, Stockholm, Sweden).
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * 3. Neither the name of the Institute nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #include "krb5_locl.h"
  35
  36 static krb5_error_code
  37 verify_checksum(krb5_context context,
  38                 krb5_auth_context auth_context,
  39                 KRB_SAFE *safe)
  40 {
  41     krb5_error_code ret;
  42     u_char *buf;
  43     size_t buf_size;
  44     size_t len = 0;
  45     Checksum c;
  46     krb5_crypto crypto;
  47     krb5_keyblock *key;
  48
  49     c = safe->cksum;
  50     safe->cksum.cksumtype       = 0;
  51     safe->cksum.checksum.data   = NULL;
  52     safe->cksum.checksum.length = 0;
  53
  54     ASN1_MALLOC_ENCODE(KRB_SAFE, buf, buf_size, safe, &len, ret);
  55     if(ret)
  56         return ret;
  57     if(buf_size != len)
  58         krb5_abortx(context, "internal error in ASN.1 encoder");
  59
  60     if (auth_context->remote_subkey)
  61         key = auth_context->remote_subkey;
  62     else if (auth_context->local_subkey)
  63         key = auth_context->local_subkey;
  64     else
  65         key = auth_context->keyblock;
  66
  67     ret = krb5_crypto_init(context, key, 0, &crypto);
  68     if (ret)
  69         goto out;
  70     ret = krb5_verify_checksum (context,
  71                                 crypto,
  72                                 KRB5_KU_KRB_SAFE_CKSUM,
  73                                 buf + buf_size - len,
  74                                 len,
  75                                 &c);
  76     krb5_crypto_destroy(context, crypto);
  77 out:
  78     safe->cksum = c;
  79     free (buf);
  80     return ret;
  81 }
  82
  83 KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
  84 krb5_rd_safe(krb5_context context,
  85              krb5_auth_context auth_context,
  86              const krb5_data *inbuf,
  87              krb5_data *outbuf,
  88              krb5_replay_data *outdata)
  89 {
  90     krb5_error_code ret;
  91     KRB_SAFE safe;
  92     size_t len;
  93
  94     krb5_data_zero(outbuf);
  95
  96     if ((auth_context->flags &
  97          (KRB5_AUTH_CONTEXT_RET_TIME | KRB5_AUTH_CONTEXT_RET_SEQUENCE)))
  98     {
  99         if (outdata == NULL) {
 100             krb5_set_error_message(context, KRB5_RC_REQUIRED,
 101                                    N_("rd_safe: need outdata "
 102                                       "to return data", ""));
 103             return KRB5_RC_REQUIRED; /* XXX better error, MIT returns this */
 104         }
 105         /* if these fields are not present in the safe-part, silently
 106            return zero */
 107         memset(outdata, 0, sizeof(*outdata));
 108     }
 109
 110     ret = decode_KRB_SAFE (inbuf->data, inbuf->length, &safe, &len);
 111     if (ret)
 112         return ret;
 113     if (safe.pvno != 5) {
 114         ret = KRB5KRB_AP_ERR_BADVERSION;
 115         krb5_clear_error_message (context);
 116         goto failure;
 117     }
 118     if (safe.msg_type != krb_safe) {
 119         ret = KRB5KRB_AP_ERR_MSG_TYPE;
 120         krb5_clear_error_message (context);
 121         goto failure;
 122     }
 123     if (!krb5_checksum_is_keyed(context, safe.cksum.cksumtype)
 124         || !krb5_checksum_is_collision_proof(context, safe.cksum.cksumtype)) {
 125         ret = KRB5KRB_AP_ERR_INAPP_CKSUM;
 126         krb5_clear_error_message (context);
 127         goto failure;
 128     }
 129
 130     /* check sender address */
 131
 132     if (safe.safe_body.s_address
 133         && auth_context->remote_address
 134         && !krb5_address_compare (context,
 135                                   auth_context->remote_address,
 136                                   safe.safe_body.s_address)) {
 137         ret = KRB5KRB_AP_ERR_BADADDR;
 138         krb5_clear_error_message (context);
 139         goto failure;
 140     }
 141
 142     /* check receiver address */
 143
 144     if (safe.safe_body.r_address
 145         && auth_context->local_address
 146         && !krb5_address_compare (context,
 147                                   auth_context->local_address,
 148                                   safe.safe_body.r_address)) {
 149         ret = KRB5KRB_AP_ERR_BADADDR;
 150         krb5_clear_error_message (context);
 151         goto failure;
 152     }
 153
 154     /* check timestamp */
 155     if (auth_context->flags & KRB5_AUTH_CONTEXT_DO_TIME) {
 156         krb5_timestamp sec;
 157
 158         krb5_timeofday (context, &sec);
 159
 160         if (safe.safe_body.timestamp == NULL ||
 161             safe.safe_body.usec      == NULL ||
 162             abs(*safe.safe_body.timestamp - sec) > context->max_skew) {
 163             ret = KRB5KRB_AP_ERR_SKEW;
 164             krb5_clear_error_message (context);
 165             goto failure;
 166         }
 167     }
 168     /* XXX - check replay cache */
 169
 170     /* check sequence number. since MIT krb5 cannot generate a sequence
 171        number of zero but instead generates no sequence number, we accept that
 172     */
 173
 174     if (auth_context->flags & KRB5_AUTH_CONTEXT_DO_SEQUENCE) {
 175         if ((safe.safe_body.seq_number == NULL
 176              && auth_context->remote_seqnumber != 0)
 177             || (safe.safe_body.seq_number != NULL
 178                 && *safe.safe_body.seq_number !=
 179                 auth_context->remote_seqnumber)) {
 180             ret = KRB5KRB_AP_ERR_BADORDER;
 181             krb5_clear_error_message (context);
 182             goto failure;
 183         }
 184         auth_context->remote_seqnumber++;
 185     }
 186
 187     ret = verify_checksum (context, auth_context, &safe);
 188     if (ret)
 189         goto failure;
 190
 191     outbuf->length = safe.safe_body.user_data.length;
 192     outbuf->data   = malloc(outbuf->length);
 193     if (outbuf->data == NULL && outbuf->length != 0) {
 194         ret = krb5_enomem(context);
 195         krb5_data_zero(outbuf);
 196         goto failure;
 197     }
 198     memcpy (outbuf->data, safe.safe_body.user_data.data, outbuf->length);
 199
 200     if ((auth_context->flags &
 201          (KRB5_AUTH_CONTEXT_RET_TIME | KRB5_AUTH_CONTEXT_RET_SEQUENCE))) {
 202
 203         if(safe.safe_body.timestamp)
 204             outdata->timestamp = *safe.safe_body.timestamp;
 205         if(safe.safe_body.usec)
 206             outdata->usec = *safe.safe_body.usec;
 207         if(safe.safe_body.seq_number)
 208             outdata->seq = *safe.safe_body.seq_number;
 209     }
 210
 211   failure:
 212     free_KRB_SAFE (&safe);
 213     return ret;
 214 }