Пример #1
0
krb5_error_code
gss_krb5int_make_seal_token_v3 (krb5_context context,
                                krb5_gss_ctx_id_rec *ctx,
                                const gss_buffer_desc * message,
                                gss_buffer_t token,
                                int conf_req_flag, int toktype)
{
    size_t bufsize = 16;
    unsigned char *outbuf = 0;
    krb5_error_code err;
    int key_usage;
    unsigned char acceptor_flag;
    const gss_buffer_desc *message2 = message;
#ifdef CFX_EXERCISE
    size_t rrc;
#endif
    size_t ec;
    unsigned short tok_id;
    krb5_checksum sum;
    krb5_key key;
    krb5_cksumtype cksumtype;

    acceptor_flag = ctx->initiate ? 0 : FLAG_SENDER_IS_ACCEPTOR;
    key_usage = (toktype == KG_TOK_WRAP_MSG
                 ? (ctx->initiate
                    ? KG_USAGE_INITIATOR_SEAL
                    : KG_USAGE_ACCEPTOR_SEAL)
                 : (ctx->initiate
                    ? KG_USAGE_INITIATOR_SIGN
                    : KG_USAGE_ACCEPTOR_SIGN));
    if (ctx->have_acceptor_subkey) {
        key = ctx->acceptor_subkey;
        cksumtype = ctx->acceptor_subkey_cksumtype;
    } else {
        key = ctx->subkey;
        cksumtype = ctx->cksumtype;
    }
    assert(key != NULL);

#ifdef CFX_EXERCISE
    {
        static int initialized = 0;
        if (!initialized) {
            srand(time(0));
            initialized = 1;
        }
    }
#endif

    if (toktype == KG_TOK_WRAP_MSG && conf_req_flag) {
        krb5_data plain;
        krb5_enc_data cipher;
        size_t ec_max;

        /* 300: Adds some slop.  */
        if (SIZE_MAX - 300 < message->length)
            return ENOMEM;
        ec_max = SIZE_MAX - message->length - 300;
        if (ec_max > 0xffff)
            ec_max = 0xffff;
#ifdef CFX_EXERCISE
        /* For testing only.  For performance, always set ec = 0.  */
        ec = ec_max & rand();
#else
        ec = 0;
#endif
        plain.length = message->length + 16 + ec;
        plain.data = malloc(message->length + 16 + ec);
        if (plain.data == NULL)
            return ENOMEM;

        /* Get size of ciphertext.  */
        bufsize = 16 + krb5_encrypt_size (plain.length, key->keyblock.enctype);
        /* Allocate space for header plus encrypted data.  */
        outbuf = gssalloc_malloc(bufsize);
        if (outbuf == NULL) {
            free(plain.data);
            return ENOMEM;
        }

        /* TOK_ID */
        store_16_be(KG2_TOK_WRAP_MSG, outbuf);
        /* flags */
        outbuf[2] = (acceptor_flag
                     | (conf_req_flag ? FLAG_WRAP_CONFIDENTIAL : 0)
                     | (ctx->have_acceptor_subkey ? FLAG_ACCEPTOR_SUBKEY : 0));
        /* filler */
        outbuf[3] = 0xff;
        /* EC */
        store_16_be(ec, outbuf+4);
        /* RRC */
        store_16_be(0, outbuf+6);
        store_64_be(ctx->seq_send, outbuf+8);

        memcpy(plain.data, message->value, message->length);
        if (ec != 0)
            memset(plain.data + message->length, 'x', ec);
        memcpy(plain.data + message->length + ec, outbuf, 16);

        cipher.ciphertext.data = (char *)outbuf + 16;
        cipher.ciphertext.length = bufsize - 16;
        cipher.enctype = key->keyblock.enctype;
        err = krb5_k_encrypt(context, key, key_usage, 0, &plain, &cipher);
        zap(plain.data, plain.length);
        free(plain.data);
        plain.data = 0;
        if (err)
            goto error;

        /* Now that we know we're returning a valid token....  */
        ctx->seq_send++;

#ifdef CFX_EXERCISE
        rrc = rand() & 0xffff;
        if (gss_krb5int_rotate_left(outbuf+16, bufsize-16,
                                    (bufsize-16) - (rrc % (bufsize - 16))))
            store_16_be(rrc, outbuf+6);
        /* If the rotate fails, don't worry about it.  */
#endif
    } else if (toktype == KG_TOK_WRAP_MSG && !conf_req_flag) {
        krb5_data plain;
        size_t cksumsize;

        /* Here, message is the application-supplied data; message2 is
           what goes into the output token.  They may be the same, or
           message2 may be empty (for MIC).  */

        tok_id = KG2_TOK_WRAP_MSG;

    wrap_with_checksum:
        plain.length = message->length + 16;
        plain.data = malloc(message->length + 16);
        if (plain.data == NULL)
            return ENOMEM;

        err = krb5_c_checksum_length(context, cksumtype, &cksumsize);
        if (err)
            goto error;

        assert(cksumsize <= 0xffff);

        bufsize = 16 + message2->length + cksumsize;
        outbuf = gssalloc_malloc(bufsize);
        if (outbuf == NULL) {
            free(plain.data);
            plain.data = 0;
            err = ENOMEM;
            goto error;
        }

        /* TOK_ID */
        store_16_be(tok_id, outbuf);
        /* flags */
        outbuf[2] = (acceptor_flag
                     | (ctx->have_acceptor_subkey ? FLAG_ACCEPTOR_SUBKEY : 0));
        /* filler */
        outbuf[3] = 0xff;
        if (toktype == KG_TOK_WRAP_MSG) {
            /* Use 0 for checksum calculation, substitute
               checksum length later.  */
            /* EC */
            store_16_be(0, outbuf+4);
            /* RRC */
            store_16_be(0, outbuf+6);
        } else {
            /* MIC and DEL store 0xFF in EC and RRC.  */
            store_16_be(0xffff, outbuf+4);
            store_16_be(0xffff, outbuf+6);
        }
        store_64_be(ctx->seq_send, outbuf+8);

        memcpy(plain.data, message->value, message->length);
        memcpy(plain.data + message->length, outbuf, 16);

        /* Fill in the output token -- data contents, if any, and
           space for the checksum.  */
        if (message2->length)
            memcpy(outbuf + 16, message2->value, message2->length);

        sum.contents = outbuf + 16 + message2->length;
        sum.length = cksumsize;

        err = krb5_k_make_checksum(context, cksumtype, key,
                                   key_usage, &plain, &sum);
        zap(plain.data, plain.length);
        free(plain.data);
        plain.data = 0;
        if (err) {
            zap(outbuf,bufsize);
            goto error;
        }
        if (sum.length != cksumsize)
            abort();
        memcpy(outbuf + 16 + message2->length, sum.contents, cksumsize);
        krb5_free_checksum_contents(context, &sum);
        sum.contents = 0;
        /* Now that we know we're actually generating the token...  */
        ctx->seq_send++;

        if (toktype == KG_TOK_WRAP_MSG) {
#ifdef CFX_EXERCISE
            rrc = rand() & 0xffff;
            /* If the rotate fails, don't worry about it.  */
            if (gss_krb5int_rotate_left(outbuf+16, bufsize-16,
                                        (bufsize-16) - (rrc % (bufsize - 16))))
                store_16_be(rrc, outbuf+6);
#endif
            /* Fix up EC field.  */
            store_16_be(cksumsize, outbuf+4);
        } else {
            store_16_be(0xffff, outbuf+6);
        }
    } else if (toktype == KG_TOK_MIC_MSG) {
        tok_id = KG2_TOK_MIC_MSG;
        message2 = &empty_message;
        goto wrap_with_checksum;
    } else if (toktype == KG_TOK_DEL_CTX) {
        tok_id = KG2_TOK_DEL_CTX;
        message = message2 = &empty_message;
        goto wrap_with_checksum;
    } else
        abort();

    token->value = outbuf;
    token->length = bufsize;
    return 0;

error:
    gssalloc_free(outbuf);
    token->value = NULL;
    token->length = 0;
    return err;
}
Пример #2
0
int
ksm_rgenerate_out_msg(struct snmp_secmod_outgoing_params *parms)
{
    krb5_auth_context auth_context = NULL;
    krb5_error_code retcode;
    krb5_ccache     cc = NULL;
    int             retval = SNMPERR_SUCCESS;
    krb5_data       outdata, ivector;
    krb5_keyblock  *subkey = NULL;
#ifdef MIT_NEW_CRYPTO
    krb5_data       input;
    krb5_enc_data   output;
    unsigned int    numcksumtypes;
    krb5_cksumtype  *cksumtype_array;
#else                           /* MIT_NEW_CRYPTO */
    krb5_encrypt_block eblock;
#endif                          /* MIT_NEW_CRYPTO */
    size_t          blocksize, encrypted_length;
    unsigned char  *encrypted_data = NULL;
    int             zero = 0, i;
    u_char         *cksum_pointer, *endp = *parms->wholeMsg;
    krb5_cksumtype  cksumtype;
    krb5_checksum   pdu_checksum;
    u_char         **wholeMsg = parms->wholeMsg;
    size_t	   *offset = parms->wholeMsgOffset, seq_offset;
    struct ksm_secStateRef *ksm_state = (struct ksm_secStateRef *)
        parms->secStateRef;
    int rc;

    DEBUGMSGTL(("ksm", "Starting KSM processing\n"));

    outdata.length = 0;
    outdata.data = NULL;
    ivector.length = 0;
    ivector.data = NULL;
    pdu_checksum.contents = NULL;

    if (!ksm_state) {
        /*
         * If we don't have a ksm_state, then we're a request.  Get a
         * credential cache and build a ap_req.
         */
        retcode = krb5_cc_default(kcontext, &cc);

        if (retcode) {
            DEBUGMSGTL(("ksm", "KSM: krb5_cc_default failed: %s\n",
                        error_message(retcode)));
            snmp_set_detail(error_message(retcode));
            retval = SNMPERR_KRB5;
            goto error;
        }

        DEBUGMSGTL(("ksm", "KSM: Set credential cache successfully\n"));

        /*
         * This seems odd, since we don't need this until later (or earlier,
         * depending on how you look at it), but because the most likely
         * errors are Kerberos at this point, I'll get this now to save
         * time not encoding the rest of the packet.
         *
         * Also, we need the subkey to encrypt the PDU (if required).
         */

        retcode =
            krb5_mk_req(kcontext, &auth_context,
                        AP_OPTS_MUTUAL_REQUIRED | AP_OPTS_USE_SUBKEY,
                        (char *) service_name, parms->session->peername, NULL,
                        cc, &outdata);

        if (retcode) {
            DEBUGMSGTL(("ksm", "KSM: krb5_mk_req failed: %s\n",
                        error_message(retcode)));
            snmp_set_detail(error_message(retcode));
            retval = SNMPERR_KRB5;
            goto error;
        }

	DEBUGMSGTL(("ksm", "KSM: ticket retrieved successfully for \"%s/%s\" "
		    "(may not be actual ticket sname)\n", service_name,
		    parms->session->peername));

    } else {

        /*
         * Grab the auth_context from our security state reference
         */

        auth_context = ksm_state->auth_context;

        /*
         * Bundle up an AP_REP.  Note that we do this only when we
         * have a security state reference (which means we're in an agent
         * and we're sending a response).
         */

        DEBUGMSGTL(("ksm", "KSM: Starting reply processing.\n"));

        retcode = krb5_mk_rep(kcontext, auth_context, &outdata);

        if (retcode) {
            DEBUGMSGTL(("ksm", "KSM: krb5_mk_rep failed: %s\n",
                        error_message(retcode)));
            snmp_set_detail(error_message(retcode));
            retval = SNMPERR_KRB5;
            goto error;
        }

        DEBUGMSGTL(("ksm", "KSM: Finished with krb5_mk_rep()\n"));
    }

    /*
     * If we have to encrypt the PDU, do that now
     */

    if (parms->secLevel == SNMP_SEC_LEVEL_AUTHPRIV) {

        DEBUGMSGTL(("ksm", "KSM: Starting PDU encryption.\n"));

        /*
         * It's weird -
         *
         * If we're on the manager, it's a local subkey (because that's in
         * our AP_REQ)
         *
         * If we're on the agent, it's a remote subkey (because that comes
         * FROM the received AP_REQ).
         */

        if (ksm_state)
            retcode = krb5_auth_con_getremotesubkey(kcontext, auth_context,
                                                    &subkey);
        else
            retcode = krb5_auth_con_getlocalsubkey(kcontext, auth_context,
                                                   &subkey);

        if (retcode) {
            DEBUGMSGTL(("ksm",
                        "KSM: krb5_auth_con_getlocalsubkey failed: %s\n",
                        error_message(retcode)));
            snmp_set_detail(error_message(retcode));
            retval = SNMPERR_KRB5;
            goto error;
        }

        /*
         * Note that here we need to handle different things between the
         * old and new crypto APIs.  First, we need to get the final encrypted
         * length of the PDU.
         */

#ifdef MIT_NEW_CRYPTO
        retcode = krb5_c_encrypt_length(kcontext, subkey->enctype,
                                        parms->scopedPduLen,
                                        &encrypted_length);

        if (retcode) {
            DEBUGMSGTL(("ksm",
                        "Encryption length calculation failed: %s\n",
                        error_message(retcode)));
            snmp_set_detail(error_message(retcode));
            retval = SNMPERR_KRB5;
            goto error;
        }
#else                           /* MIT_NEW_CRYPTO */

        krb5_use_enctype(kcontext, &eblock, subkey->enctype);
        retcode = krb5_process_key(kcontext, &eblock, subkey);

        if (retcode) {
            DEBUGMSGTL(("ksm", "krb5_process_key failed: %s\n",
                        error_message(retcode)));
            snmp_set_detail(error_message(retcode));
            retval = SNMPERR_KRB5;
            goto error;
        }

        encrypted_length = krb5_encrypt_size(parms->scopedPduLen,
                                             eblock.crypto_entry);
#endif                          /* MIT_NEW_CRYPTO */

        encrypted_data = malloc(encrypted_length);

        if (!encrypted_data) {
            DEBUGMSGTL(("ksm",
                        "KSM: Unable to malloc %d bytes for encrypt "
                        "buffer: %s\n", parms->scopedPduLen,
                        strerror(errno)));
            retval = SNMPERR_MALLOC;
#ifndef MIT_NEW_CRYPTO
            krb5_finish_key(kcontext, &eblock);
#endif                          /* ! MIT_NEW_CRYPTO */

            goto error;
        }

        /*
         * We need to set up a blank initialization vector for the encryption.
         * Use a block of all zero's (which is dependent on the block size
         * of the encryption method).
         */

#ifdef MIT_NEW_CRYPTO

        retcode = krb5_c_block_size(kcontext, subkey->enctype, &blocksize);

        if (retcode) {
            DEBUGMSGTL(("ksm",
                        "Unable to determine crypto block size: %s\n",
                        error_message(retcode)));
            snmp_set_detail(error_message(retcode));
            retval = SNMPERR_KRB5;
            goto error;
        }
#else                           /* MIT_NEW_CRYPTO */

        blocksize =
            krb5_enctype_array[subkey->enctype]->system->block_length;

#endif                          /* MIT_NEW_CRYPTO */

        ivector.data = malloc(blocksize);

        if (!ivector.data) {
            DEBUGMSGTL(("ksm", "Unable to allocate %d bytes for ivector\n",
                        blocksize));
            retval = SNMPERR_MALLOC;
            goto error;
        }

        ivector.length = blocksize;
        memset(ivector.data, 0, blocksize);

        /*
         * Finally!  Do the encryption!
         */

#ifdef MIT_NEW_CRYPTO

        input.data = (char *) parms->scopedPdu;
        input.length = parms->scopedPduLen;
        output.ciphertext.data = (char *) encrypted_data;
        output.ciphertext.length = encrypted_length;

        retcode =
            krb5_c_encrypt(kcontext, subkey, KSM_KEY_USAGE_ENCRYPTION,
                           &ivector, &input, &output);

#else                           /* MIT_NEW_CRYPTO */

        retcode = krb5_encrypt(kcontext, (krb5_pointer) parms->scopedPdu,
                               (krb5_pointer) encrypted_data,
                               parms->scopedPduLen, &eblock, ivector.data);

        krb5_finish_key(kcontext, &eblock);

#endif                          /* MIT_NEW_CRYPTO */

        if (retcode) {
            DEBUGMSGTL(("ksm", "KSM: krb5_encrypt failed: %s\n",
                        error_message(retcode)));
            retval = SNMPERR_KRB5;
            snmp_set_detail(error_message(retcode));
            goto error;
        }

	*offset = 0;

        rc = asn_realloc_rbuild_string(wholeMsg, parms->wholeMsgLen,
                                             offset, 1,
                                             (u_char) (ASN_UNIVERSAL |
                                                       ASN_PRIMITIVE |
                                                       ASN_OCTET_STR),
                                             encrypted_data,
                                             encrypted_length);

        if (rc == 0) {
            DEBUGMSGTL(("ksm", "Building encrypted payload failed.\n"));
            retval = SNMPERR_TOO_LONG;
            goto error;
        }

        DEBUGMSGTL(("ksm", "KSM: Encryption complete.\n"));

    } else {
        /*
         * Plaintext PDU (not encrypted)
         */

        if (*parms->wholeMsgLen < parms->scopedPduLen) {
            DEBUGMSGTL(("ksm", "Not enough room for plaintext PDU.\n"));
            retval = SNMPERR_TOO_LONG;
            goto error;
        }
    }

    /*
     * Start encoding the msgSecurityParameters
     *
     * For now, use 0 for the response hint
     */

    DEBUGMSGTL(("ksm", "KSM: scopedPdu added to payload\n"));

    seq_offset = *offset;

    rc = asn_realloc_rbuild_int(wholeMsg, parms->wholeMsgLen,
                                      offset, 1,
                                      (u_char) (ASN_UNIVERSAL |
                                                ASN_PRIMITIVE |
                                                ASN_INTEGER),
                                      (long *) &zero, sizeof(zero));

    if (rc == 0) {
        DEBUGMSGTL(("ksm", "Building ksm security parameters failed.\n"));
        retval = SNMPERR_TOO_LONG;
        goto error;
    }

    rc = asn_realloc_rbuild_string(wholeMsg, parms->wholeMsgLen,
                                         offset, 1,
                                         (u_char) (ASN_UNIVERSAL |
                                                   ASN_PRIMITIVE |
                                                   ASN_OCTET_STR),
                                         (u_char *) outdata.data,
                                         outdata.length);

    if (rc == 0) {
        DEBUGMSGTL(("ksm", "Building ksm AP_REQ failed.\n"));
        retval = SNMPERR_TOO_LONG;
        goto error;
    }

    /*
     * Now, we need to pick the "right" checksum algorithm.  For old
     * crypto, just pick CKSUMTYPE_RSA_MD5_DES; for new crypto, pick
     * one of the "approved" ones.
     */

#ifdef MIT_NEW_CRYPTO
    retcode = krb5_c_keyed_checksum_types(kcontext, subkey->enctype,
                                          &numcksumtypes, &cksumtype_array);

    if (retcode) {
	DEBUGMSGTL(("ksm", "Unable to find appropriate keyed checksum: %s\n",
		    error_message(retcode)));
	snmp_set_detail(error_message(retcode));
        retval = SNMPERR_KRB5;
        goto error;
    }

    if (numcksumtypes <= 0) {
	DEBUGMSGTL(("ksm", "We received a list of zero cksumtypes for this "
		    "enctype (%d)\n", subkey->enctype));
	snmp_set_detail("No valid checksum type for this encryption type");
	retval = SNMPERR_KRB5;
	goto error;
    }

    /*
     * It's not clear to me from the API which checksum you're supposed
     * to support, so I'm taking a guess at the first one
     */

    cksumtype = cksumtype_array[0];

    krb5_free_cksumtypes(kcontext, cksumtype_array);

    DEBUGMSGTL(("ksm", "KSM: Choosing checksum type of %d (subkey type "
		"of %d)\n", cksumtype, subkey->enctype));

    retcode = krb5_c_checksum_length(kcontext, cksumtype, &blocksize);

    if (retcode) {
        DEBUGMSGTL(("ksm", "Unable to determine checksum length: %s\n",
                    error_message(retcode)));
        snmp_set_detail(error_message(retcode));
        retval = SNMPERR_KRB5;
        goto error;
    }

    pdu_checksum.length = blocksize;

#else /* MIT_NEW_CRYPTO */
    if (ksm_state)
        cksumtype = ksm_state->cksumtype;
    else
	cksumtype = CKSUMTYPE_RSA_MD5_DES;

    if (!is_keyed_cksum(cksumtype)) {
        DEBUGMSGTL(("ksm", "Checksum type %d is not a keyed checksum\n",
                    cksumtype));
        snmp_set_detail("Checksum is not a keyed checksum");
        retval = SNMPERR_KRB5;
        goto error;
    }

    if (!is_coll_proof_cksum(cksumtype)) {
        DEBUGMSGTL(("ksm", "Checksum type %d is not a collision-proof "
                    "checksum\n", cksumtype));
        snmp_set_detail("Checksum is not a collision-proof checksum");
        retval = SNMPERR_KRB5;
        goto error;
    }

    pdu_checksum.length = krb5_checksum_size(kcontext, cksumtype);
    pdu_checksum.checksum_type = cksumtype;

#endif /* MIT_NEW_CRYPTO */

    /*
     * Note that here, we're just leaving blank space for the checksum;
     * we remember where that is, and we'll fill it in later.
     */

    *offset += pdu_checksum.length;
    memset(*wholeMsg + *parms->wholeMsgLen - *offset, 0, pdu_checksum.length);

    cksum_pointer = *wholeMsg + *parms->wholeMsgLen - *offset;

    rc = asn_realloc_rbuild_header(wholeMsg, parms->wholeMsgLen,
                                         parms->wholeMsgOffset, 1,
                                         (u_char) (ASN_UNIVERSAL |
                                                   ASN_PRIMITIVE |
                                                   ASN_OCTET_STR),
                                         pdu_checksum.length);

    if (rc == 0) {
        DEBUGMSGTL(("ksm", "Building ksm security parameters failed.\n"));
        retval = SNMPERR_TOO_LONG;
        goto error;
    }

    rc = asn_realloc_rbuild_int(wholeMsg, parms->wholeMsgLen,
                                      parms->wholeMsgOffset, 1,
                                      (u_char) (ASN_UNIVERSAL |
                                                ASN_PRIMITIVE |
                                                ASN_OCTET_STR),
                                      (long *) &cksumtype,
                                      sizeof(cksumtype));

    if (rc == 0) {
        DEBUGMSGTL(("ksm", "Building ksm security parameters failed.\n"));
        retval = SNMPERR_TOO_LONG;
        goto error;
    }

    rc = asn_realloc_rbuild_sequence(wholeMsg, parms->wholeMsgLen,
                                           parms->wholeMsgOffset, 1,
                                           (u_char) (ASN_SEQUENCE |
                                                     ASN_CONSTRUCTOR),
                                           *offset - seq_offset);

    if (rc == 0) {
        DEBUGMSGTL(("ksm", "Building ksm security parameters failed.\n"));
        retval = SNMPERR_TOO_LONG;
        goto error;
    }

    rc = asn_realloc_rbuild_header(wholeMsg, parms->wholeMsgLen,
                                         parms->wholeMsgOffset, 1,
                                         (u_char) (ASN_UNIVERSAL |
                                                   ASN_PRIMITIVE |
                                                   ASN_OCTET_STR),
                                         *offset - seq_offset);

    if (rc == 0) {
        DEBUGMSGTL(("ksm", "Building ksm security parameters failed.\n"));
        retval = SNMPERR_TOO_LONG;
        goto error;
    }

    DEBUGMSGTL(("ksm", "KSM: Security parameter encoding completed\n"));

    /*
     * We're done with the KSM security parameters - now we do the global
     * header and wrap up the whole PDU.
     */

    if (*parms->wholeMsgLen < parms->globalDataLen) {
        DEBUGMSGTL(("ksm", "Building global data failed.\n"));
        retval = SNMPERR_TOO_LONG;
        goto error;
    }

    *offset += parms->globalDataLen;
    memcpy(*wholeMsg + *parms->wholeMsgLen - *offset,
	   parms->globalData, parms->globalDataLen);

    rc = asn_realloc_rbuild_sequence(wholeMsg, parms->wholeMsgLen,
                                           offset, 1,
                                           (u_char) (ASN_SEQUENCE |
                                                     ASN_CONSTRUCTOR),
                                           *offset);

    if (rc == 0) {
        DEBUGMSGTL(("ksm", "Building master packet sequence.\n"));
        retval = SNMPERR_TOO_LONG;
        goto error;
    }

    DEBUGMSGTL(("ksm", "KSM: PDU master packet encoding complete.\n"));

    /*
     * Now we need to checksum the entire PDU (since it's built).
     */

    pdu_checksum.contents = malloc(pdu_checksum.length);

    if (!pdu_checksum.contents) {
        DEBUGMSGTL(("ksm", "Unable to malloc %d bytes for checksum\n",
                    pdu_checksum.length));
        retval = SNMPERR_MALLOC;
        goto error;
    }

    /*
     * If we didn't encrypt the packet, we haven't yet got the subkey.
     * Get that now.
     */

    if (!subkey) {
        if (ksm_state)
            retcode = krb5_auth_con_getremotesubkey(kcontext, auth_context,
                                                    &subkey);
        else
            retcode = krb5_auth_con_getlocalsubkey(kcontext, auth_context,
                                                   &subkey);
        if (retcode) {
            DEBUGMSGTL(("ksm", "krb5_auth_con_getlocalsubkey failed: %s\n",
                        error_message(retcode)));
            snmp_set_detail(error_message(retcode));
            retval = SNMPERR_KRB5;
            goto error;
        }
    }
#ifdef MIT_NEW_CRYPTO

    input.data = (char *) (*wholeMsg + *parms->wholeMsgLen - *offset);
    input.length = *offset;
        retcode = krb5_c_make_checksum(kcontext, cksumtype, subkey,
                                       KSM_KEY_USAGE_CHECKSUM, &input,
                                       &pdu_checksum);

#else                           /* MIT_NEW_CRYPTO */

    retcode = krb5_calculate_checksum(kcontext, cksumtype, *wholeMsg +
				      *parms->wholeMsgLen - *offset,
                                      *offset,
                                      (krb5_pointer) subkey->contents,
                                      subkey->length, &pdu_checksum);

#endif                          /* MIT_NEW_CRYPTO */

    if (retcode) {
        DEBUGMSGTL(("ksm", "Calculate checksum failed: %s\n",
                    error_message(retcode)));
        retval = SNMPERR_KRB5;
        snmp_set_detail(error_message(retcode));
        goto error;
    }

    DEBUGMSGTL(("ksm", "KSM: Checksum calculation complete.\n"));

    memcpy(cksum_pointer, pdu_checksum.contents, pdu_checksum.length);

    DEBUGMSGTL(("ksm", "KSM: Writing checksum of %d bytes at offset %d\n",
                pdu_checksum.length, cksum_pointer - (*wholeMsg + 1)));

    DEBUGMSGTL(("ksm", "KSM: Checksum:"));

    for (i = 0; i < pdu_checksum.length; i++)
        DEBUGMSG(("ksm", " %02x",
                  (unsigned int) pdu_checksum.contents[i]));

    DEBUGMSG(("ksm", "\n"));

    /*
     * If we're _not_ called as part of a response (null ksm_state),
     * then save the auth_context for later using our cache routines.
     */

    if (!ksm_state) {
        if ((retval = ksm_insert_cache(parms->pdu->msgid, auth_context,
                                       (u_char *) parms->secName,
                                       parms->secNameLen)) !=
            SNMPERR_SUCCESS)
            goto error;
        auth_context = NULL;
    }

    DEBUGMSGTL(("ksm", "KSM processing complete!\n"));

  error:

    if (pdu_checksum.contents)
#ifdef MIT_NEW_CRYPTO
        krb5_free_checksum_contents(kcontext, &pdu_checksum);
#else                           /* MIT_NEW_CRYPTO */
        free(pdu_checksum.contents);
#endif                          /* MIT_NEW_CRYPTO */

    if (ivector.data)
        free(ivector.data);

    if (subkey)
        krb5_free_keyblock(kcontext, subkey);

    if (encrypted_data)
        free(encrypted_data);

    if (cc)
        krb5_cc_close(kcontext, cc);

    if (auth_context && !ksm_state)
        krb5_auth_con_free(kcontext, auth_context);

    return retval;
}