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/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* lib/krb5/krb/rd_safe.c - definition of krb5_rd_safe() */
/*
* Copyright 1990,1991,2007,2008 by the Massachusetts Institute of Technology.
* All Rights Reserved.
*
* Export of this software from the United States of America may
* require a specific license from the United States Government.
* It is the responsibility of any person or organization contemplating
* export to obtain such a license before exporting.
*
* WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
* distribute this software and its documentation for any purpose and
* without fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright notice and
* this permission notice appear in supporting documentation, and that
* the name of M.I.T. not be used in advertising or publicity pertaining
* to distribution of the software without specific, written prior
* permission. Furthermore if you modify this software you must label
* your software as modified software and not distribute it in such a
* fashion that it might be confused with the original M.I.T. software.
* M.I.T. makes no representations about the suitability of
* this software for any purpose. It is provided "as is" without express
* or implied warranty.
*/
#include "k5-int.h"
#include "int-proto.h"
#include "cleanup.h"
#include "auth_con.h"
/*
parses a KRB_SAFE message from inbuf, placing the integrity-protected user
data in *outbuf.
key specifies the key to be used for decryption of the message.
outbuf points to allocated storage which the caller should free when finished.
returns system errors, integrity errors
*/
static krb5_error_code
rd_safe_basic(krb5_context context, krb5_auth_context ac,
const krb5_data *inbuf, krb5_key key,
krb5_replay_data *replaydata, krb5_data *outbuf)
{
krb5_error_code retval;
krb5_safe * message;
krb5_data *safe_body = NULL;
krb5_checksum our_cksum, *his_cksum;
krb5_octet zero_octet = 0;
krb5_data *scratch;
krb5_boolean valid;
struct krb5_safe_with_body swb;
if (!krb5_is_krb_safe(inbuf))
return KRB5KRB_AP_ERR_MSG_TYPE;
if ((retval = decode_krb5_safe_with_body(inbuf, &message, &safe_body)))
return retval;
if (!krb5_c_valid_cksumtype(message->checksum->checksum_type)) {
retval = KRB5_PROG_SUMTYPE_NOSUPP;
goto cleanup;
}
if (!krb5_c_is_coll_proof_cksum(message->checksum->checksum_type) ||
!krb5_c_is_keyed_cksum(message->checksum->checksum_type)) {
retval = KRB5KRB_AP_ERR_INAPP_CKSUM;
goto cleanup;
}
retval = k5_privsafe_check_addrs(context, ac, message->s_address,
message->r_address);
if (retval)
goto cleanup;
/* verify the checksum */
/*
* In order to recreate what was checksummed, we regenerate the message
* without checksum and then have the cryptographic subsystem verify
* the checksum for us. This is because some checksum methods have
* a confounder encrypted as part of the checksum.
*/
his_cksum = message->checksum;
our_cksum.length = 0;
our_cksum.checksum_type = 0;
our_cksum.contents = &zero_octet;
message->checksum = &our_cksum;
swb.body = safe_body;
swb.safe = message;
retval = encode_krb5_safe_with_body(&swb, &scratch);
message->checksum = his_cksum;
if (retval)
goto cleanup;
retval = krb5_k_verify_checksum(context, key,
KRB5_KEYUSAGE_KRB_SAFE_CKSUM,
scratch, his_cksum, &valid);
(void) memset(scratch->data, 0, scratch->length);
krb5_free_data(context, scratch);
if (!valid) {
/*
* Checksum over only the KRB-SAFE-BODY, like RFC 1510 says, in
* case someone actually implements it correctly.
*/
retval = krb5_k_verify_checksum(context, key,
KRB5_KEYUSAGE_KRB_SAFE_CKSUM,
safe_body, his_cksum, &valid);
if (!valid) {
retval = KRB5KRB_AP_ERR_MODIFIED;
goto cleanup;
}
}
replaydata->timestamp = message->timestamp;
replaydata->usec = message->usec;
replaydata->seq = message->seq_number;
*outbuf = message->user_data;
message->user_data.data = NULL;
retval = 0;
cleanup:
krb5_free_safe(context, message);
krb5_free_data(context, safe_body);
return retval;
}
krb5_error_code KRB5_CALLCONV
krb5_rd_safe(krb5_context context, krb5_auth_context auth_context,
const krb5_data *inbuf, krb5_data *outbuf,
krb5_replay_data *outdata)
{
krb5_error_code retval;
krb5_key key;
krb5_replay_data replaydata;
if (((auth_context->auth_context_flags & KRB5_AUTH_CONTEXT_RET_TIME) ||
(auth_context->auth_context_flags & KRB5_AUTH_CONTEXT_RET_SEQUENCE)) &&
(outdata == NULL))
/* Need a better error */
return KRB5_RC_REQUIRED;
if ((auth_context->auth_context_flags & KRB5_AUTH_CONTEXT_DO_TIME) &&
(auth_context->remote_addr == NULL))
return KRB5_REMOTE_ADDR_REQUIRED;
if ((auth_context->auth_context_flags & KRB5_AUTH_CONTEXT_DO_TIME) &&
(auth_context->rcache == NULL))
return KRB5_RC_REQUIRED;
/* Get key */
if ((key = auth_context->recv_subkey) == NULL)
key = auth_context->key;
memset(&replaydata, 0, sizeof(replaydata));
retval = rd_safe_basic(context, auth_context, inbuf, key, &replaydata,
outbuf);
if (retval)
return retval;
if (auth_context->auth_context_flags & KRB5_AUTH_CONTEXT_DO_TIME) {
krb5_donot_replay replay;
if ((retval = krb5_check_clockskew(context, replaydata.timestamp)))
goto error;
if ((retval = krb5_gen_replay_name(context, auth_context->remote_addr,
"_safe", &replay.client)))
goto error;
replay.server = ""; /* XXX */
replay.msghash = NULL;
replay.cusec = replaydata.usec;
replay.ctime = replaydata.timestamp;
if ((retval = krb5_rc_store(context, auth_context->rcache, &replay))) {
free(replay.client);
goto error;
}
free(replay.client);
}
if (auth_context->auth_context_flags & KRB5_AUTH_CONTEXT_DO_SEQUENCE) {
if (!k5_privsafe_check_seqnum(context, auth_context, replaydata.seq)) {
retval = KRB5KRB_AP_ERR_BADORDER;
goto error;
}
auth_context->remote_seq_number++;
}
if ((auth_context->auth_context_flags & KRB5_AUTH_CONTEXT_RET_TIME) ||
(auth_context->auth_context_flags & KRB5_AUTH_CONTEXT_RET_SEQUENCE)) {
outdata->timestamp = replaydata.timestamp;
outdata->usec = replaydata.usec;
outdata->seq = replaydata.seq;
}
/* everything is ok - return data to the user */
return 0;
error:
free(outbuf->data);
return retval;
}
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