snmpksm.c

snmp up 2

        }

        retcode = krb5_auth_con_setrcache(kcontext, auth_context, rcache);

        if (retcode) {
            DEBUGMSGTL(("ksm", "krb5_auth_con_setrcache failed: %s\n",
                        error_message(retcode)));
            retval = SNMPERR_KRB5;
            snmp_set_detail(error_message(retcode));
            goto error;
        }

        retcode = krb5_rd_req(kcontext, &auth_context, &ap_req, NULL,
                              NULL, &flags, &ticket);

        krb5_auth_con_setrcache(kcontext, auth_context, NULL);

        if (retcode) {
            DEBUGMSGTL(("ksm", "krb5_rd_req() failed: %s\n",
                        error_message(retcode)));
            retval = SNMPERR_KRB5;
            snmp_set_detail(error_message(retcode));
            goto error;
        }

        retcode =
            krb5_unparse_name(kcontext, ticket->enc_part2->client, &cname);

        if (retcode == 0) {
            DEBUGMSGTL(("ksm", "KSM authenticated principal name: %s\n",
                        cname));
            free(cname);
        }

        /*
         * Check to make sure AP_OPTS_MUTUAL_REQUIRED was set
         */

        if (!(flags & AP_OPTS_MUTUAL_REQUIRED)) {
            DEBUGMSGTL(("ksm",
                        "KSM MUTUAL_REQUIRED not set in request!\n"));
            retval = SNMPERR_KRB5;
            snmp_set_detail("MUTUAL_REQUIRED not set in message");
            goto error;
        }

        retcode =
            krb5_auth_con_getremotesubkey(kcontext, auth_context, &subkey);

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

    } else if (ap_req.length && (ap_req.data[0] == 0x6f ||
                                 ap_req.data[0] == 0x4f)) {
        /*
         * Looks like a response; let's see if we've got that auth_context
         * in our cache.
         */

        krb5_ap_rep_enc_part *repl = NULL;

        response = 1;

        entry = ksm_get_cache(parms->pdu->msgid);

        if (!entry) {
            DEBUGMSGTL(("ksm",
                        "KSM: Unable to find auth_context for PDU with "
                        "message ID of %ld\n", parms->pdu->msgid));
            retval = SNMPERR_KRB5;
            goto error;
        }

        auth_context = entry->auth_context;

        /*
         * In that case, let's call the rd_rep function
         */

        retcode = krb5_rd_rep(kcontext, auth_context, &ap_req, &repl);

        if (repl)
            krb5_free_ap_rep_enc_part(kcontext, repl);

        if (retcode) {
            DEBUGMSGTL(("ksm", "KSM: krb5_rd_rep() failed: %s\n",
                        error_message(retcode)));
            retval = SNMPERR_KRB5;
            goto error;
        }

        DEBUGMSGTL(("ksm", "KSM: krb5_rd_rep() decoded successfully.\n"));

        retcode =
            krb5_auth_con_getlocalsubkey(kcontext, auth_context, &subkey);

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

    } else {
        DEBUGMSGTL(("ksm", "Unknown Kerberos message type (%02x)\n",
                    ap_req.data[0]));
        retval = SNMPERR_KRB5;
        snmp_set_detail("Unknown Kerberos message type");
        goto error;
    }

#ifdef MIT_NEW_CRYPTO
    input.data = (char *) parms->wholeMsg;
    input.length = parms->wholeMsgLen;

    retcode =
        krb5_c_verify_checksum(kcontext, subkey, KSM_KEY_USAGE_CHECKSUM,
                               &input, &checksum, &valid);
#else                           /* MIT_NEW_CRYPTO */
    retcode = krb5_verify_checksum(kcontext, cksumtype, &checksum,
                                   parms->wholeMsg, parms->wholeMsgLen,
                                   (krb5_pointer) subkey->contents,
                                   subkey->length);
#endif                          /* MIT_NEW_CRYPTO */

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

    /*
     * Don't ask me why they didn't simply return an error, but we have
     * to check to see if "valid" is false.
     */

#ifdef MIT_NEW_CRYPTO
    if (!valid) {
        DEBUGMSGTL(("ksm", "Computed checksum did not match supplied "
                    "checksum!\n"));
        retval = SNMPERR_KRB5;
        snmp_set_detail
            ("Computed checksum did not match supplied checksum");
        goto error;
    }
#endif                          /* MIT_NEW_CRYPTO */

    /*
     * Handle an encrypted PDU.  Note that it's an OCTET_STRING of the
     * output of whatever Kerberos cryptosystem you're using (defined by
     * the encryption type).  Note that this is NOT the EncryptedData
     * sequence - it's what goes in the "cipher" field of EncryptedData.
     */

    if (parms->secLevel == SNMP_SEC_LEVEL_AUTHPRIV) {

        if ((current = asn_parse_sequence(current, &length, &type,
                                          (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                           ASN_OCTET_STR), "ksm pdu")) ==
            NULL) {
            DEBUGMSGTL(("ksm", "KSM sPDU octet decoding failed\n"));
            retval = SNMPERR_ASN_PARSE_ERR;
            goto error;
        }

        /*
         * The PDU is now pointed at by "current", and the length is in
         * "length".
         */

        DEBUGMSGTL(("ksm", "KSM starting sPDU decode\n"));

        /*
         * We need to set up a blank initialization vector for the decryption.
         * 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);

#ifndef MIT_NEW_CRYPTO

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

        retcode = krb5_process_key(kcontext, &eblock, subkey);

        if (retcode) {
            DEBUGMSGTL(("ksm", "KSM key post-processing failed: %s\n",
                        error_message(retcode)));
            snmp_set_detail(error_message(retcode));
            retval = SNMPERR_KRB5;
            goto error;
        }
#endif                          /* !MIT_NEW_CRYPTO */

        if (length > *parms->scopedPduLen) {
            DEBUGMSGTL(("ksm", "KSM not enough room - have %d bytes to "
                        "decrypt but only %d bytes available\n", length,
                        *parms->scopedPduLen));
            retval = SNMPERR_TOO_LONG;
#ifndef MIT_NEW_CRYPTO
            krb5_finish_key(kcontext, &eblock);
#endif                          /* ! MIT_NEW_CRYPTO */
            goto error;
        }
#ifdef MIT_NEW_CRYPTO
        in_crypt.ciphertext.data = (char *) current;
        in_crypt.ciphertext.length = length;
        in_crypt.enctype = subkey->enctype;
        output.data = (char *) *parms->scopedPdu;
        output.length = *parms->scopedPduLen;

        retcode =
            krb5_c_decrypt(kcontext, subkey, KSM_KEY_USAGE_ENCRYPTION,
                           &ivector, &in_crypt, &output);
#else                           /* MIT_NEW_CRYPTO */

        retcode = krb5_decrypt(kcontext, (krb5_pointer) current,
                               *parms->scopedPdu, length, &eblock,
                               ivector.data);

        krb5_finish_key(kcontext, &eblock);

#endif                          /* MIT_NEW_CRYPTO */

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

        *parms->scopedPduLen = length;

    } else {
        /*
         * Clear PDU
         */

        *parms->scopedPdu = current;
        *parms->scopedPduLen =
            parms->wholeMsgLen - (current - parms->wholeMsg);
    }

    /*
     * A HUGE GROSS HACK
     */

    *parms->maxSizeResponse = parms->maxMsgSize - 200;

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

    /*
     * Set the secName to the right value (a hack for now).  But that's
     * only used for when we're processing a request, not a response.
     */

    if (!response) {

        retcode = krb5_unparse_name(kcontext, ticket->enc_part2->client,
                                    &cname);

        if (retcode) {
            DEBUGMSGTL(("ksm", "KSM krb5_unparse_name failed: %s\n",
                        error_message(retcode)));
            snmp_set_detail(error_message(retcode));
            retval = SNMPERR_KRB5;
            goto error;
        }

        if (strlen(cname) > *parms->secNameLen + 1) {
            DEBUGMSGTL(("ksm",
                        "KSM: Principal length (%d) is too long (%d)\n",
                        strlen(cname), parms->secNameLen));
            retval = SNMPERR_TOO_LONG;
            free(cname);
            goto error;
        }

        strcpy(parms->secName, cname);
        *parms->secNameLen = strlen(cname);

        free(cname);

        /*
         * Also, if we're not a response, keep around our auth_context so we
         * can encode the reply message correctly
         */

        ksm_state = SNMP_MALLOC_STRUCT(ksm_secStateRef);

        if (!ksm_state) {
            DEBUGMSGTL(("ksm", "KSM unable to malloc memory for "
                        "ksm_secStateRef\n"));
            retval = SNMPERR_MALLOC;
            goto error;
        }

        ksm_state->auth_context = auth_context;
        auth_context = NULL;
        ksm_state->cksumtype = cksumtype;

        *parms->secStateRef = ksm_state;
    } else {

        /*
         * We _still_ have to set the secName in process_in_msg().  Do
         * that now with what we were passed in before (we cached it,
         * remember?)
         */

        memcpy(parms->secName, entry->secName, entry->secNameLen);
        *parms->secNameLen = entry->secNameLen;
    }

    /*
     * Just in case
     */

    parms->secEngineID = (u_char *) "";
    *parms->secEngineIDLen = 0;

    auth_context = NULL;        /* So we don't try to free it on success */

  error:
    if (retval == SNMPERR_ASN_PARSE_ERR &&
        snmp_increment_statistic(STAT_SNMPINASNPARSEERRS) == 0)
        DEBUGMSGTL(("ksm", "Failed to increment statistics.\n"));

    if (subkey)
        krb5_free_keyblock(kcontext, subkey);

    if (checksum.contents)
        free(checksum.contents);

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

    if (ticket)
        krb5_free_ticket(kcontext, ticket);

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

    if (ap_req.data)
        free(ap_req.data);

    return retval;
}