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 RCSID("$Id$");
  37
  38 static krb5_error_code
  39 verify_checksum(krb5_context context,
  40                 krb5_auth_context auth_context,
  41                 KRB_SAFE *safe)
  42 {
  43     krb5_error_code ret;
  44     u_char *buf;
  45     size_t buf_size;
  46     size_t len;
  47     Checksum c;
  48     krb5_crypto crypto;
  49     krb5_keyblock *key;
  50
  51     c = safe->cksum;
  52     safe->cksum.cksumtype       = 0;
  53     safe->cksum.checksum.data   = NULL;
  54     safe->cksum.checksum.length = 0;
  55
  56     ASN1_MALLOC_ENCODE(KRB_SAFE, buf, buf_size, safe, &len, ret);
  57     if(ret)
  58         return ret;
  59     if(buf_size != len)
  60         krb5_abortx(context, "internal error in ASN.1 encoder");
  61
  62     if (auth_context->remote_subkey)
  63         key = auth_context->remote_subkey;
  64     else if (auth_context->local_subkey)
  65         key = auth_context->local_subkey;
  66     else
  67         key = auth_context->keyblock;
  68
  69     ret = krb5_crypto_init(context, key, 0, &crypto);
  70     if (ret)
  71         goto out;
  72     ret = krb5_verify_checksum (context,
  73                                 crypto,
  74                                 KRB5_KU_KRB_SAFE_CKSUM,
  75                                 buf + buf_size - len,
  76                                 len,
  77                                 &c);
  78     krb5_crypto_destroy(context, crypto);
  79 out:
  80     safe->cksum = c;
  81     free (buf);
  82     return ret;
  83 }
  84
  85 krb5_error_code KRB5_LIB_FUNCTION
  86 krb5_rd_safe(krb5_context context,
  87              krb5_auth_context auth_context,
  88              const krb5_data *inbuf,
  89              krb5_data *outbuf,
  90              krb5_replay_data *outdata)
  91 {
  92     krb5_error_code ret;
  93     KRB_SAFE safe;
  94     size_t len;
  95
  96     if (outbuf)
  97         krb5_data_zero(outbuf);
  98
  99     if ((auth_context->flags &
 100          (KRB5_AUTH_CONTEXT_RET_TIME | KRB5_AUTH_CONTEXT_RET_SEQUENCE)) &&
 101         outdata == NULL) {
 102         krb5_set_error_string(context, "rd_safe: need outdata to return data");
 103         return KRB5_RC_REQUIRED; /* XXX better error, MIT returns this */
 104     }
 105
 106     ret = decode_KRB_SAFE (inbuf->data, inbuf->length, &safe, &len);
 107     if (ret)
 108         return ret;
 109     if (safe.pvno != 5) {
 110         ret = KRB5KRB_AP_ERR_BADVERSION;
 111         krb5_clear_error_string (context);
 112         goto failure;
 113     }
 114     if (safe.msg_type != krb_safe) {
 115         ret = KRB5KRB_AP_ERR_MSG_TYPE;
 116         krb5_clear_error_string (context);
 117         goto failure;
 118     }
 119     if (!krb5_checksum_is_keyed(context, safe.cksum.cksumtype)
 120         || !krb5_checksum_is_collision_proof(context, safe.cksum.cksumtype)) {
 121         ret = KRB5KRB_AP_ERR_INAPP_CKSUM;
 122         krb5_clear_error_string (context);
 123         goto failure;
 124     }
 125
 126     /* check sender address */
 127
 128     if (safe.safe_body.s_address
 129         && auth_context->remote_address
 130         && !krb5_address_compare (context,
 131                                   auth_context->remote_address,
 132                                   safe.safe_body.s_address)) {
 133         ret = KRB5KRB_AP_ERR_BADADDR;
 134         krb5_clear_error_string (context);
 135         goto failure;
 136     }
 137
 138     /* check receiver address */
 139
 140     if (safe.safe_body.r_address
 141         && auth_context->local_address
 142         && !krb5_address_compare (context,
 143                                   auth_context->local_address,
 144                                   safe.safe_body.r_address)) {
 145         ret = KRB5KRB_AP_ERR_BADADDR;
 146         krb5_clear_error_string (context);
 147         goto failure;
 148     }
 149
 150     /* check timestamp */
 151     if (auth_context->flags & KRB5_AUTH_CONTEXT_DO_TIME) {
 152         krb5_timestamp sec;
 153
 154         krb5_timeofday (context, &sec);
 155
 156         if (safe.safe_body.timestamp == NULL ||
 157             safe.safe_body.usec      == NULL ||
 158             abs(*safe.safe_body.timestamp - sec) > context->max_skew) {
 159             ret = KRB5KRB_AP_ERR_SKEW;
 160             krb5_clear_error_string (context);
 161             goto failure;
 162         }
 163     }
 164     /* XXX - check replay cache */
 165
 166     /* check sequence number. since MIT krb5 cannot generate a sequence
 167        number of zero but instead generates no sequence number, we accept that
 168     */
 169
 170     if (auth_context->flags & KRB5_AUTH_CONTEXT_DO_SEQUENCE) {
 171         if ((safe.safe_body.seq_number == NULL
 172              && auth_context->remote_seqnumber != 0)
 173             || (safe.safe_body.seq_number != NULL
 174                 && *safe.safe_body.seq_number !=
 175                 auth_context->remote_seqnumber)) {
 176             ret = KRB5KRB_AP_ERR_BADORDER;
 177             krb5_clear_error_string (context);
 178             goto failure;
 179         }
 180         auth_context->remote_seqnumber++;
 181     }
 182
 183     ret = verify_checksum (context, auth_context, &safe);
 184     if (ret)
 185         goto failure;
 186
 187     outbuf->length = safe.safe_body.user_data.length;
 188     outbuf->data   = malloc(outbuf->length);
 189     if (outbuf->data == NULL && outbuf->length != 0) {
 190         ret = ENOMEM;
 191         krb5_set_error_string (context, "malloc: out of memory");
 192         krb5_data_zero(outbuf);
 193         goto failure;
 194     }
 195     memcpy (outbuf->data, safe.safe_body.user_data.data, outbuf->length);
 196
 197     if ((auth_context->flags &
 198          (KRB5_AUTH_CONTEXT_RET_TIME | KRB5_AUTH_CONTEXT_RET_SEQUENCE))) {
 199         /* if these fields are not present in the safe-part, silently
 200            return zero */
 201         memset(outdata, 0, sizeof(*outdata));
 202         if(safe.safe_body.timestamp)
 203             outdata->timestamp = *safe.safe_body.timestamp;
 204         if(safe.safe_body.usec)
 205             outdata->usec = *safe.safe_body.usec;
 206         if(safe.safe_body.seq_number)
 207             outdata->seq = *safe.safe_body.seq_number;
 208     }
 209
 210   failure:
 211     free_KRB_SAFE (&safe);
 212     return ret;
 213 }