src/lib/krb5/krb/rd_safe.c

   1 /* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
   2 /* lib/krb5/krb/rd_safe.c - krb5_rd_safe() */
   3 /*
   4  * Copyright 1990,1991,2007,2008,2019 by the Massachusetts Institute of
   5  * Technology.  All Rights Reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * * Redistributions of source code must retain the above copyright
  12  *   notice, this list of conditions and the following disclaimer.
  13  *
  14  * * Redistributions in binary form must reproduce the above copyright
  15  *   notice, this list of conditions and the following disclaimer in
  16  *   the documentation and/or other materials provided with the
  17  *   distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  20  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  21  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  22  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  23  * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  24  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  25  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  26  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  28  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  29  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  30  * OF THE POSSIBILITY OF SUCH DAMAGE.
  31  */
  32
  33 #include "k5-int.h"
  34 #include "int-proto.h"
  35 #include "auth_con.h"
  36
  37 /*
  38  * Unmarshal a KRB-SAFE message from der_krbsafe, placing the
  39  * integrity-protected user data in *userdata_out, replay data in *rdata_out,
  40  * and checksum in *cksum_out.  The caller should free *userdata_out and
  41  * *cksum_out when finished.
  42  */
  43 static krb5_error_code
  44 read_krbsafe(krb5_context context, krb5_auth_context ac,
  45              const krb5_data *der_krbsafe, krb5_key key,
  46              krb5_replay_data *rdata_out, krb5_data *userdata_out,
  47              krb5_checksum **cksum_out)
  48 {
  49     krb5_error_code ret;
  50     krb5_safe *krbsafe;
  51     krb5_data *safe_body = NULL, *der_zerosafe = NULL;
  52     krb5_checksum zero_cksum, *safe_cksum = NULL;
  53     krb5_octet zero_octet = 0;
  54     krb5_boolean valid;
  55     struct krb5_safe_with_body swb;
  56
  57     *userdata_out = empty_data();
  58     *cksum_out = NULL;
  59     if (!krb5_is_krb_safe(der_krbsafe))
  60         return KRB5KRB_AP_ERR_MSG_TYPE;
  61
  62     ret = decode_krb5_safe_with_body(der_krbsafe, &krbsafe, &safe_body);
  63     if (ret)
  64         return ret;
  65
  66     if (!krb5_c_valid_cksumtype(krbsafe->checksum->checksum_type)) {
  67         ret = KRB5_PROG_SUMTYPE_NOSUPP;
  68         goto cleanup;
  69     }
  70     if (!krb5_c_is_coll_proof_cksum(krbsafe->checksum->checksum_type) ||
  71         !krb5_c_is_keyed_cksum(krbsafe->checksum->checksum_type)) {
  72         ret = KRB5KRB_AP_ERR_INAPP_CKSUM;
  73         goto cleanup;
  74     }
  75
  76     ret = k5_privsafe_check_addrs(context, ac, krbsafe->s_address,
  77                                   krbsafe->r_address);
  78     if (ret)
  79         goto cleanup;
  80
  81     /* Regenerate the KRB-SAFE message without the checksum.  Save the message
  82      * checksum to verify. */
  83     safe_cksum = krbsafe->checksum;
  84     zero_cksum.length = 0;
  85     zero_cksum.checksum_type = 0;
  86     zero_cksum.contents = &zero_octet;
  87     krbsafe->checksum = &zero_cksum;
  88     swb.body = safe_body;
  89     swb.safe = krbsafe;
  90     ret = encode_krb5_safe_with_body(&swb, &der_zerosafe);
  91     krbsafe->checksum = NULL;
  92     if (ret)
  93         goto cleanup;
  94
  95     /* Verify the checksum over the re-encoded message. */
  96     ret = krb5_k_verify_checksum(context, key, KRB5_KEYUSAGE_KRB_SAFE_CKSUM,
  97                                  der_zerosafe, safe_cksum, &valid);
  98     if (!valid) {
  99         /* Checksum over only the KRB-SAFE-BODY as specified in RFC 1510. */
 100         ret = krb5_k_verify_checksum(context, key,
 101                                      KRB5_KEYUSAGE_KRB_SAFE_CKSUM,
 102                                      safe_body, safe_cksum, &valid);
 103         if (!valid) {
 104             ret = KRB5KRB_AP_ERR_MODIFIED;
 105             goto cleanup;
 106         }
 107     }
 108
 109     rdata_out->timestamp = krbsafe->timestamp;
 110     rdata_out->usec = krbsafe->usec;
 111     rdata_out->seq = krbsafe->seq_number;
 112
 113     *userdata_out = krbsafe->user_data;
 114     krbsafe->user_data.data = NULL;
 115
 116     *cksum_out = safe_cksum;
 117     safe_cksum = NULL;
 118
 119 cleanup:
 120     zapfreedata(der_zerosafe);
 121     krb5_free_data(context, safe_body);
 122     krb5_free_safe(context, krbsafe);
 123     krb5_free_checksum(context, safe_cksum);
 124     return ret;
 125 }
 126
 127 krb5_error_code KRB5_CALLCONV
 128 krb5_rd_safe(krb5_context context, krb5_auth_context authcon,
 129              const krb5_data *inbuf, krb5_data *userdata_out,
 130              krb5_replay_data *rdata_out)
 131 {
 132     krb5_error_code ret;
 133     krb5_key key;
 134     krb5_replay_data rdata;
 135     krb5_data userdata = empty_data();
 136     krb5_checksum *cksum;
 137     const krb5_int32 flags = authcon->auth_context_flags;
 138
 139     *userdata_out = empty_data();
 140
 141     if (((flags & KRB5_AUTH_CONTEXT_RET_TIME) ||
 142          (flags & KRB5_AUTH_CONTEXT_RET_SEQUENCE)) && rdata_out == NULL)
 143         return KRB5_RC_REQUIRED;
 144
 145     key = (authcon->recv_subkey != NULL) ? authcon->recv_subkey : authcon->key;
 146     memset(&rdata, 0, sizeof(rdata));
 147     ret = read_krbsafe(context, authcon, inbuf, key, &rdata, &userdata,
 148                        &cksum);
 149     if (ret)
 150         goto cleanup;
 151
 152     ret = k5_privsafe_check_replay(context, authcon, &rdata, NULL, cksum);
 153     if (ret)
 154         goto cleanup;
 155
 156     if (flags & KRB5_AUTH_CONTEXT_DO_SEQUENCE) {
 157         if (!k5_privsafe_check_seqnum(context, authcon, rdata.seq)) {
 158             ret = KRB5KRB_AP_ERR_BADORDER;
 159             goto cleanup;
 160         }
 161         authcon->remote_seq_number++;
 162     }
 163
 164     if ((flags & KRB5_AUTH_CONTEXT_RET_TIME) ||
 165         (flags & KRB5_AUTH_CONTEXT_RET_SEQUENCE)) {
 166         rdata_out->timestamp = rdata.timestamp;
 167         rdata_out->usec = rdata.usec;
 168         rdata_out->seq = rdata.seq;
 169     }
 170
 171     *userdata_out = userdata;
 172     userdata = empty_data();
 173
 174 cleanup:
 175     krb5_free_data_contents(context, &userdata);
 176     krb5_free_checksum(context, cksum);
 177     return ret;
 178 }