source: heimdal/trunk/lib/krb5/rd_safe.c

/*
 * Copyright (c) 1997 - 2003 Kungliga Tekniska Högskolan
 * (Royal Institute of Technology, Stockholm, Sweden).
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "krb5_locl.h"

static krb5_error_code
verify_checksum(krb5_context context,
                krb5_auth_context auth_context,
                KRB_SAFE *safe)
{
    krb5_error_code ret;
    u_char *buf;
    size_t buf_size;
    size_t len = 0;
    Checksum c;
    krb5_crypto crypto;
    krb5_keyblock *key;

    c = safe->cksum;
    safe->cksum.cksumtype       = 0;
    safe->cksum.checksum.data   = NULL;
    safe->cksum.checksum.length = 0;

    ASN1_MALLOC_ENCODE(KRB_SAFE, buf, buf_size, safe, &len, ret);
    if(ret)
        return ret;
    if(buf_size != len)
        krb5_abortx(context, "internal error in ASN.1 encoder");

    if (auth_context->remote_subkey)
        key = auth_context->remote_subkey;
    else if (auth_context->local_subkey)
        key = auth_context->local_subkey;
    else
        key = auth_context->keyblock;

    ret = krb5_crypto_init(context, key, 0, &crypto);
    if (ret)
        goto out;
    ret = krb5_verify_checksum (context,
                                crypto,
                                KRB5_KU_KRB_SAFE_CKSUM,
                                buf + buf_size - len,
                                len,
                                &c);
    krb5_crypto_destroy(context, crypto);
out:
    safe->cksum = c;
    free (buf);
    return ret;
}

KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
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 ret;
    KRB_SAFE safe;
    size_t len;

    krb5_data_zero(outbuf);

    if ((auth_context->flags &
         (KRB5_AUTH_CONTEXT_RET_TIME | KRB5_AUTH_CONTEXT_RET_SEQUENCE)))
    {
        if (outdata == NULL) {
            krb5_set_error_message(context, KRB5_RC_REQUIRED,
                                   N_("rd_safe: need outdata "
                                      "to return data", ""));
            return KRB5_RC_REQUIRED; /* XXX better error, MIT returns this */
        }
        /* if these fields are not present in the safe-part, silently
           return zero */
        memset(outdata, 0, sizeof(*outdata));
    }

    ret = decode_KRB_SAFE (inbuf->data, inbuf->length, &safe, &len);
    if (ret)
        return ret;
    if (safe.pvno != 5) {
        ret = KRB5KRB_AP_ERR_BADVERSION;
        krb5_clear_error_message (context);
        goto failure;
    }
    if (safe.msg_type != krb_safe) {
        ret = KRB5KRB_AP_ERR_MSG_TYPE;
        krb5_clear_error_message (context);
        goto failure;
    }
    if (!krb5_checksum_is_keyed(context, safe.cksum.cksumtype)
        || !krb5_checksum_is_collision_proof(context, safe.cksum.cksumtype)) {
        ret = KRB5KRB_AP_ERR_INAPP_CKSUM;
        krb5_clear_error_message (context);
        goto failure;
    }

    /* check sender address */

    if (safe.safe_body.s_address
        && auth_context->remote_address
        && !krb5_address_compare (context,
                                  auth_context->remote_address,
                                  safe.safe_body.s_address)) {
        ret = KRB5KRB_AP_ERR_BADADDR;
        krb5_clear_error_message (context);
        goto failure;
    }

    /* check receiver address */

    if (safe.safe_body.r_address
        && auth_context->local_address
        && !krb5_address_compare (context,
                                  auth_context->local_address,
                                  safe.safe_body.r_address)) {
        ret = KRB5KRB_AP_ERR_BADADDR;
        krb5_clear_error_message (context);
        goto failure;
    }

    /* check timestamp */
    if (auth_context->flags & KRB5_AUTH_CONTEXT_DO_TIME) {
        krb5_timestamp sec;

        krb5_timeofday (context, &sec);

        if (safe.safe_body.timestamp == NULL ||
            safe.safe_body.usec      == NULL ||
            abs(*safe.safe_body.timestamp - sec) > context->max_skew) {
            ret = KRB5KRB_AP_ERR_SKEW;
            krb5_clear_error_message (context);
            goto failure;
        }
    }
    /* XXX - check replay cache */

    /* check sequence number. since MIT krb5 cannot generate a sequence
       number of zero but instead generates no sequence number, we accept that
    */

    if (auth_context->flags & KRB5_AUTH_CONTEXT_DO_SEQUENCE) {
        if ((safe.safe_body.seq_number == NULL
             && auth_context->remote_seqnumber != 0)
            || (safe.safe_body.seq_number != NULL
                && *safe.safe_body.seq_number !=
                auth_context->remote_seqnumber)) {
            ret = KRB5KRB_AP_ERR_BADORDER;
            krb5_clear_error_message (context);
            goto failure;
        }
        auth_context->remote_seqnumber++;
    }

    ret = verify_checksum (context, auth_context, &safe);
    if (ret)
        goto failure;

    outbuf->length = safe.safe_body.user_data.length;
    outbuf->data   = malloc(outbuf->length);
    if (outbuf->data == NULL && outbuf->length != 0) {
        ret = ENOMEM;
        krb5_set_error_message(context, ret, N_("malloc: out of memory", ""));
        krb5_data_zero(outbuf);
        goto failure;
    }
    memcpy (outbuf->data, safe.safe_body.user_data.data, outbuf->length);

    if ((auth_context->flags &
         (KRB5_AUTH_CONTEXT_RET_TIME | KRB5_AUTH_CONTEXT_RET_SEQUENCE))) {

        if(safe.safe_body.timestamp)
            outdata->timestamp = *safe.safe_body.timestamp;
        if(safe.safe_body.usec)
            outdata->usec = *safe.safe_body.usec;
        if(safe.safe_body.seq_number)
            outdata->seq = *safe.safe_body.seq_number;
    }

  failure:
    free_KRB_SAFE (&safe);
    return ret;
}