rd_safe.c revision 103423 
1/*
2 * Copyright (c) 1997 - 2002 Kungliga Tekniska H�gskolan
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
36RCSID("$Id: rd_safe.c,v 1.27 2002/09/04 16:26:05 joda Exp $");
37
38static krb5_error_code
39verify_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);
79out:
80    safe->cksum = c;
81    free (buf);
82    return ret;
83}
84
85krb5_error_code
86krb5_rd_safe(krb5_context context,
87	     krb5_auth_context auth_context,
88	     const krb5_data *inbuf,
89	     krb5_data *outbuf,
90	     /*krb5_replay_data*/ void *outdata)
91{
92  krb5_error_code ret;
93  KRB_SAFE safe;
94  size_t len;
95
96  ret = decode_KRB_SAFE (inbuf->data, inbuf->length, &safe, &len);
97  if (ret)
98      return ret;
99  if (safe.pvno != 5) {
100      ret = KRB5KRB_AP_ERR_BADVERSION;
101      krb5_clear_error_string (context);
102      goto failure;
103  }
104  if (safe.msg_type != krb_safe) {
105      ret = KRB5KRB_AP_ERR_MSG_TYPE;
106      krb5_clear_error_string (context);
107      goto failure;
108  }
109  if (!krb5_checksum_is_keyed(context, safe.cksum.cksumtype)
110      || !krb5_checksum_is_collision_proof(context, safe.cksum.cksumtype)) {
111      ret = KRB5KRB_AP_ERR_INAPP_CKSUM;
112      krb5_clear_error_string (context);
113      goto failure;
114  }
115
116  /* check sender address */
117
118  if (safe.safe_body.s_address
119      && auth_context->remote_address
120      && !krb5_address_compare (context,
121				auth_context->remote_address,
122				safe.safe_body.s_address)) {
123      ret = KRB5KRB_AP_ERR_BADADDR;
124      krb5_clear_error_string (context);
125      goto failure;
126  }
127
128  /* check receiver address */
129
130  if (safe.safe_body.r_address
131      && auth_context->local_address
132      && !krb5_address_compare (context,
133				auth_context->local_address,
134				safe.safe_body.r_address)) {
135      ret = KRB5KRB_AP_ERR_BADADDR;
136      krb5_clear_error_string (context);
137      goto failure;
138  }
139
140  /* check timestamp */
141  if (auth_context->flags & KRB5_AUTH_CONTEXT_DO_TIME) {
142      krb5_timestamp sec;
143
144      krb5_timeofday (context, &sec);
145
146      if (safe.safe_body.timestamp == NULL ||
147	  safe.safe_body.usec      == NULL ||
148	  abs(*safe.safe_body.timestamp - sec) > context->max_skew) {
149	  ret = KRB5KRB_AP_ERR_SKEW;
150	  krb5_clear_error_string (context);
151	  goto failure;
152      }
153  }
154  /* XXX - check replay cache */
155
156  /* check sequence number. since MIT krb5 cannot generate a sequence
157     number of zero but instead generates no sequence number, we accept that
158  */
159
160  if (auth_context->flags & KRB5_AUTH_CONTEXT_DO_SEQUENCE) {
161      if ((safe.safe_body.seq_number == NULL
162	   && auth_context->remote_seqnumber != 0)
163	  || (safe.safe_body.seq_number != NULL
164	      && *safe.safe_body.seq_number !=
165	      auth_context->remote_seqnumber)) {
166	  ret = KRB5KRB_AP_ERR_BADORDER;
167	  krb5_clear_error_string (context);
168	  goto failure;
169      }
170      auth_context->remote_seqnumber++;
171  }
172
173  ret = verify_checksum (context, auth_context, &safe);
174  if (ret)
175      goto failure;
176
177  outbuf->length = safe.safe_body.user_data.length;
178  outbuf->data   = malloc(outbuf->length);
179  if (outbuf->data == NULL) {
180      ret = ENOMEM;
181      krb5_set_error_string (context, "malloc: out of memory");
182      goto failure;
183  }
184  memcpy (outbuf->data, safe.safe_body.user_data.data, outbuf->length);
185  free_KRB_SAFE (&safe);
186  return 0;
187failure:
188  free_KRB_SAFE (&safe);
189  return ret;
190}
191