system/dlzexternal/driver.c

/*
 * Copyright (C) 2011-2017  Internet Systems Consortium, Inc. ("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

/*
 * This provides a very simple example of an external loadable DLZ
 * driver, with update support.
 */

#include <config.h>

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>

#include <isc/log.h>
#include <isc/result.h>
#include <isc/string.h>
#include <isc/types.h>
#include <isc/util.h>

#include <dns/types.h>
#include <dns/dlz_dlopen.h>

#include "driver.h"

#ifdef WIN32
#define STRTOK_R(a, b, c)   strtok_s(a, b, c)
#elif defined(_REENTRANT)
#define STRTOK_R(a, b, c)       strtok_r(a, b, c)
#else
#define STRTOK_R(a, b, c)       strtok(a, b)
#endif

#define CHECK(x) \
    do { \
        result = (x); \
        if (result != ISC_R_SUCCESS) \
            goto failure; \
    } while (0)

/* For this simple example, use fixed sized strings */
struct record {
    char name[100];
    char type[10];
    char data[200];
    dns_ttl_t ttl;
};

#define MAX_RECORDS 100

typedef void log_t(int level, const char *fmt, ...);

struct dlz_example_data {
    char *zone_name;

    /* An example driver doesn't need good memory management :-) */
    struct record current[MAX_RECORDS];
    struct record adds[MAX_RECORDS];
    struct record deletes[MAX_RECORDS];

    isc_boolean_t transaction_started;

    /* Helper functions from the dlz_dlopen driver */
    log_t *log;
    dns_sdlz_putrr_t *putrr;
    dns_sdlz_putnamedrr_t *putnamedrr;
    dns_dlz_writeablezone_t *writeable_zone;
};

static isc_boolean_t
single_valued(const char *type) {
    const char *single[] = { "soa", "cname", NULL };
    int i;

    for (i = 0; single[i]; i++) {
        if (strcasecmp(single[i], type) == 0) {
            return (ISC_TRUE);
        }
    }
    return (ISC_FALSE);
}

/*
 * Add a record to a list
 */
static isc_result_t
add_name(struct dlz_example_data *state, struct record *list,
     const char *name, const char *type, dns_ttl_t ttl, const char *data)
{
    int i;
    isc_boolean_t single = single_valued(type);
    int first_empty = -1;

    for (i = 0; i < MAX_RECORDS; i++) {
        if (first_empty == -1 && strlen(list[i].name) == 0U) {
            first_empty = i;
        }
        if (strcasecmp(list[i].name, name) != 0)
            continue;
        if (strcasecmp(list[i].type, type) != 0)
            continue;
        if (!single && strcasecmp(list[i].data, data) != 0)
            continue;
        break;
    }
    if (i == MAX_RECORDS && first_empty != -1) {
        i = first_empty;
    }
    if (i == MAX_RECORDS) {
        if (state->log != NULL)
            state->log(ISC_LOG_ERROR,
                   "dlz_example: out of record space");
        return (ISC_R_FAILURE);
    }

    if (strlen(name) >= sizeof(list[i].name) ||
        strlen(type) >= sizeof(list[i].type) ||
        strlen(data) >= sizeof(list[i].data))
        return (ISC_R_NOSPACE);

    strncpy(list[i].name, name, sizeof(list[i].name));
    list[i].name[sizeof(list[i].name) - 1] = '\0';

    strncpy(list[i].type, type, sizeof(list[i].type));
    list[i].type[sizeof(list[i].type) - 1] = '\0';

    strncpy(list[i].data, data, sizeof(list[i].data));
    list[i].data[sizeof(list[i].data) - 1] = '\0';

    list[i].ttl = ttl;

    return (ISC_R_SUCCESS);
}

/*
 * Delete a record from a list
 */
static isc_result_t
del_name(struct dlz_example_data *state, struct record *list,
     const char *name, const char *type, dns_ttl_t ttl,
     const char *data)
{
    int i;

    UNUSED(state);

    for (i = 0; i < MAX_RECORDS; i++) {
        if (strcasecmp(name, list[i].name) == 0 &&
            strcasecmp(type, list[i].type) == 0 &&
            strcasecmp(data, list[i].data) == 0 &&
            ttl == list[i].ttl) {
            break;
        }
    }
    if (i == MAX_RECORDS) {
        return (ISC_R_NOTFOUND);
    }
    memset(&list[i], 0, sizeof(struct record));
    return (ISC_R_SUCCESS);
}

static isc_result_t
fmt_address(isc_sockaddr_t *addr, char *buffer, size_t size) {
    char addr_buf[100];
    const char *ret;
    isc_uint16_t port = 0;

    switch (addr->type.sa.sa_family) {
    case AF_INET:
        port = ntohs(addr->type.sin.sin_port);
        ret = inet_ntop(AF_INET, &addr->type.sin.sin_addr, addr_buf,
                sizeof(addr_buf));
        break;
    case AF_INET6:
        port = ntohs(addr->type.sin6.sin6_port);
        ret = inet_ntop(AF_INET6, &addr->type.sin6.sin6_addr, addr_buf,
                sizeof(addr_buf));
        break;
    default:
        return (ISC_R_FAILURE);
    }

    if (ret == NULL)
        return (ISC_R_FAILURE);

    snprintf(buffer, size, "%s#%u", addr_buf, port);
    return (ISC_R_SUCCESS);
}

/*
 * Return the version of the API
 */
int
dlz_version(unsigned int *flags) {
    UNUSED(flags);
    return (DLZ_DLOPEN_VERSION);
}

/*
 * Remember a helper function from the bind9 dlz_dlopen driver
 */
static void
b9_add_helper(struct dlz_example_data *state,
          const char *helper_name, void *ptr)
{
    if (strcmp(helper_name, "log") == 0)
        state->log = (log_t *)ptr;
    if (strcmp(helper_name, "putrr") == 0)
        state->putrr = (dns_sdlz_putrr_t *)ptr;
    if (strcmp(helper_name, "putnamedrr") == 0)
        state->putnamedrr = (dns_sdlz_putnamedrr_t *)ptr;
    if (strcmp(helper_name, "writeable_zone") == 0)
        state->writeable_zone = (dns_dlz_writeablezone_t *)ptr;
}

/*
 * Called to initialize the driver
 */
isc_result_t
dlz_create(const char *dlzname, unsigned int argc, char *argv[],
       void **dbdata, ...)
{
    struct dlz_example_data *state;
    const char *helper_name;
    va_list ap;
    char soa_data[1024];
    const char *extra;
    isc_result_t result;
    int n;

    UNUSED(dlzname);

    state = calloc(1, sizeof(struct dlz_example_data));
    if (state == NULL)
        return (ISC_R_NOMEMORY);

    /* Fill in the helper functions */
    va_start(ap, dbdata);
    while ((helper_name = va_arg(ap, const char *)) != NULL) {
        b9_add_helper(state, helper_name, va_arg(ap, void *));
    }
    va_end(ap);

    if (argc < 2 || argv[1][0] == '\0') {
        if (state->log != NULL)
            state->log(ISC_LOG_ERROR,
                   "dlz_example: please specify a zone name");
        dlz_destroy(state);
        return (ISC_R_FAILURE);
    }

    /* Ensure zone name is absolute */
    state->zone_name = malloc(strlen(argv[1]) + 2);
    if (state->zone_name == NULL) {
        free(state);
        return (ISC_R_NOMEMORY);
    }
    if (argv[1][strlen(argv[1]) - 1] == '.')
        strcpy(state->zone_name, argv[1]);
    else
        sprintf(state->zone_name, "%s.", argv[1]);

    if (strcmp(state->zone_name, ".") == 0)
        extra = ".root";
    else
        extra = ".";

    n = sprintf(soa_data, "%s hostmaster%s%s 123 900 600 86400 3600",
            state->zone_name, extra, state->zone_name);

    if (n < 0)
        CHECK(ISC_R_FAILURE);
    if ((unsigned)n >= sizeof(soa_data))
        CHECK(ISC_R_NOSPACE);

    add_name(state, &state->current[0], state->zone_name,
         "soa", 3600, soa_data);
    add_name(state, &state->current[0], state->zone_name,
         "ns", 3600, state->zone_name);
    add_name(state, &state->current[0], state->zone_name,
         "a", 1800, "10.53.0.1");

    if (state->log != NULL)
        state->log(ISC_LOG_INFO, "dlz_example: started for zone %s",
               state->zone_name);

    *dbdata = state;
    return (ISC_R_SUCCESS);

 failure:
    free(state);
    return (result);

}

/*
 * Shut down the backend
 */
void
dlz_destroy(void *dbdata) {
    struct dlz_example_data *state = (struct dlz_example_data *)dbdata;

    if (state->log != NULL)
        state->log(ISC_LOG_INFO,
               "dlz_example: shutting down zone %s",
               state->zone_name);
    free(state->zone_name);
    free(state);
}

/*
 * See if we handle a given zone
 */
isc_result_t
dlz_findzonedb(void *dbdata, const char *name,
       dns_clientinfomethods_t *methods,
       dns_clientinfo_t *clientinfo)
{
    struct dlz_example_data *state = (struct dlz_example_data *)dbdata;
    isc_sockaddr_t *src;
    char addrbuf[100];
    char absolute[1024];

    strcpy(addrbuf, "unknown");
    if (methods != NULL &&
        methods->sourceip != NULL &&
        methods->version - methods->age <= DNS_CLIENTINFOMETHODS_VERSION &&
        DNS_CLIENTINFOMETHODS_VERSION <= methods->version)
    {
        methods->sourceip(clientinfo, &src);
        fmt_address(src, addrbuf, sizeof(addrbuf));
    }

    state->log(ISC_LOG_INFO,
           "dlz_example: dlz_findzonedb called with name '%s' "
           "in zone DB '%s' from %s",
           name, state->zone_name, addrbuf);

    /*
     * Returning ISC_R_NOTFOUND will cause the query logic to
     * check the database for parent names, looking for zone cuts.
     *
     * Returning ISC_R_NOMORE prevents the query logic from doing
     * this; it will move onto the next database after a single query.
     */
    if (strcasecmp(name, "test.example.com") == 0)
        return (ISC_R_NOMORE);

    /*
     * For example.net, only return ISC_R_NOMORE when queried
     * from 10.53.0.1.
     */
    if (strcasecmp(name, "test.example.net") == 0 &&
        strncmp(addrbuf, "10.53.0.1", 9) == 0)
        return (ISC_R_NOMORE);

    /*
     * For bigcname.domain, return success so it appears to be
     * the zone origin; this regression tests a bug in which
     * zone origin nodes could fail to return SERVFAIL to the client.
     */
    if (strcasecmp(name, "bigcname.domain") == 0)
        return (ISC_R_SUCCESS);

    /*
     * Return success if we have an exact match between the
     * zone name and the qname
     */
    if (strcasecmp(state->zone_name, name) == 0)
        return (ISC_R_SUCCESS);

    snprintf(absolute, sizeof(absolute), "%s.", name);
    if (strcasecmp(state->zone_name, absolute) == 0)
        return (ISC_R_SUCCESS);

    return (ISC_R_NOTFOUND);
}

/*
 * Look up one record in the sample database.
 *
 * If the queryname is "source-addr", send back a TXT record containing
 * the address of the client, to test the use of 'methods' and 'clientinfo'
 *
 * If the queryname is "too-long", send back a TXT record that's too long
 * to process; this should result in a SERVFAIL when queried.
 */
isc_result_t
dlz_lookup(const char *zone, const char *name, void *dbdata,
       dns_sdlzlookup_t *lookup, dns_clientinfomethods_t *methods,
       dns_clientinfo_t *clientinfo)
{
    isc_result_t result;
    struct dlz_example_data *state = (struct dlz_example_data *)dbdata;
    isc_boolean_t found = ISC_FALSE;
    void *dbversion = NULL;
    isc_sockaddr_t *src;
    char full_name[256];
    char buf[512];
    static char last[256] = { 0 };
    static int count = 0;
    int i;

    UNUSED(zone);

    if (state->putrr == NULL)
        return (ISC_R_NOTIMPLEMENTED);

    if (strcmp(name, "@") == 0) {
        strncpy(full_name, state->zone_name, 255);
        full_name[255] = '\0';
    } else if (strcmp(state->zone_name, ".") == 0)
        snprintf(full_name, 255, "%s.", name);
    else
        snprintf(full_name, 255, "%s.%s", name, state->zone_name);

    /*
     * For test purposes, log all calls to dlz_lookup()
     */
    if (strncasecmp(full_name, last, 255) == 0)
        count++;
    else {
        count = 1;
        strncpy(last, full_name, 255);
    }
    state->log(ISC_LOG_INFO, "lookup #%d for %s", count, full_name);

    /*
     * If we need to know the database version (as set in
     * the 'newversion' dlz function) we can pick it up from the
     * clientinfo.
     *
     * This allows a lookup to query the correct version of the DNS
     * data, if the DLZ can differentiate between versions.
     *
     * For example, if a new database transaction is created by
     * 'newversion', the lookup should query within the same
     * transaction scope if it can.
     *
     * If the DLZ only operates on 'live' data, then version
     * wouldn't necessarily be needed.
     */
    if (clientinfo != NULL &&
        clientinfo->version >= DNS_CLIENTINFO_VERSION) {
        dbversion = clientinfo->dbversion;
        if (dbversion != NULL && *(isc_boolean_t *)dbversion)
            state->log(ISC_LOG_INFO,
                   "dlz_example: lookup against live "
                   "transaction");
    }

    if (strcmp(name, "source-addr") == 0) {
        strcpy(buf, "unknown");
        if (methods != NULL &&
            methods->sourceip != NULL &&
            (methods->version - methods->age <=
             DNS_CLIENTINFOMETHODS_VERSION) &&
            DNS_CLIENTINFOMETHODS_VERSION <= methods->version)
        {
            methods->sourceip(clientinfo, &src);
            fmt_address(src, buf, sizeof(buf));
        }

        state->log(ISC_LOG_INFO,
               "dlz_example: lookup connection from %s", buf);

        found = ISC_TRUE;
        result = state->putrr(lookup, "TXT", 0, buf);
        if (result != ISC_R_SUCCESS)
            return (result);
    }

    if (strcmp(name, "too-long") == 0 ||
        strcmp(zone, "bigcname.domain") == 0)
    {
        for (i = 0; i < 511; i++)
            buf[i] = 'x';
        buf[i] = '\0';
        found = ISC_TRUE;
        result = state->putrr(lookup, "TXT", 0, buf);
        if (result != ISC_R_SUCCESS)
            return (result);
    }

    /* Tests for DLZ redirection zones */
    if (strcmp(name, "*") == 0 && strcmp(zone, ".") == 0) {
        result = state->putrr(lookup, "A", 0, "100.100.100.2");
        found = ISC_TRUE;
        if (result != ISC_R_SUCCESS)
            return (result);
    }

    if (strcmp(name, "long.name.is.not.there") == 0 &&
        strcmp(zone, ".") == 0)
    {
        result = state->putrr(lookup, "A", 0, "100.100.100.3");
        found = ISC_TRUE;
        if (result != ISC_R_SUCCESS)
            return (result);
    }

    /* Answer from current records */
    for (i = 0; i < MAX_RECORDS; i++) {
        if (strcasecmp(state->current[i].name, full_name) == 0) {
            found = ISC_TRUE;
            result = state->putrr(lookup, state->current[i].type,
                          state->current[i].ttl,
                          state->current[i].data);
            if (result != ISC_R_SUCCESS)
                return (result);
        }
    }

    if (!found)
        return (ISC_R_NOTFOUND);

    return (ISC_R_SUCCESS);
}


/*
 * See if a zone transfer is allowed
 */
isc_result_t
dlz_allowzonexfr(void *dbdata, const char *name, const char *client) {
    UNUSED(client);

    /* Just say yes for all our zones */
    return (dlz_findzonedb(dbdata, name, NULL, NULL));
}

/*
 * Perform a zone transfer
 */
isc_result_t
dlz_allnodes(const char *zone, void *dbdata, dns_sdlzallnodes_t *allnodes) {
    struct dlz_example_data *state = (struct dlz_example_data *)dbdata;
    int i;

    UNUSED(zone);

    if (state->putnamedrr == NULL)
        return (ISC_R_NOTIMPLEMENTED);

    for (i = 0; i < MAX_RECORDS; i++) {
        isc_result_t result;
        if (strlen(state->current[i].name) == 0U) {
            continue;
        }
        result = state->putnamedrr(allnodes, state->current[i].name,
                       state->current[i].type,
                       state->current[i].ttl,
                       state->current[i].data);
        if (result != ISC_R_SUCCESS)
            return (result);
    }

    return (ISC_R_SUCCESS);
}


/*
 * Start a transaction
 */
isc_result_t
dlz_newversion(const char *zone, void *dbdata, void **versionp) {
    struct dlz_example_data *state = (struct dlz_example_data *)dbdata;

    if (state->transaction_started) {
        if (state->log != NULL)
            state->log(ISC_LOG_INFO,
                   "dlz_example: transaction already "
                   "started for zone %s", zone);
        return (ISC_R_FAILURE);
    }

    state->transaction_started = ISC_TRUE;
    *versionp = (void *) &state->transaction_started;

    return (ISC_R_SUCCESS);
}

/*
 * End a transaction
 */
void
dlz_closeversion(const char *zone, isc_boolean_t commit,
         void *dbdata, void **versionp)
{
    struct dlz_example_data *state = (struct dlz_example_data *)dbdata;

    if (!state->transaction_started) {
        if (state->log != NULL)
            state->log(ISC_LOG_INFO, "dlz_example: transaction not "
                   "started for zone %s", zone);
        *versionp = NULL;
        return;
    }

    state->transaction_started = ISC_FALSE;

    *versionp = NULL;

    if (commit) {
        int i;
        if (state->log != NULL)
            state->log(ISC_LOG_INFO, "dlz_example: committing "
                   "transaction on zone %s", zone);
        for (i = 0; i < MAX_RECORDS; i++) {
            if (strlen(state->deletes[i].name) > 0U) {
                (void)del_name(state, &state->current[0],
                           state->deletes[i].name,
                           state->deletes[i].type,
                           state->deletes[i].ttl,
                           state->deletes[i].data);
            }
        }
        for (i = 0; i < MAX_RECORDS; i++) {
            if (strlen(state->adds[i].name) > 0U) {
                (void)add_name(state, &state->current[0],
                           state->adds[i].name,
                           state->adds[i].type,
                           state->adds[i].ttl,
                           state->adds[i].data);
            }
        }
    } else {
        if (state->log != NULL)
            state->log(ISC_LOG_INFO, "dlz_example: cancelling "
                   "transaction on zone %s", zone);
    }
    memset(state->adds, 0, sizeof(state->adds));
    memset(state->deletes, 0, sizeof(state->deletes));
}


/*
 * Configure a writeable zone
 */
isc_result_t
dlz_configure(dns_view_t *view, dns_dlzdb_t *dlzdb, void *dbdata) {
    struct dlz_example_data *state = (struct dlz_example_data *)dbdata;
    isc_result_t result;

    if (state->log != NULL)
        state->log(ISC_LOG_INFO, "dlz_example: starting configure");

    if (state->writeable_zone == NULL) {
        if (state->log != NULL)
            state->log(ISC_LOG_INFO, "dlz_example: no "
                   "writeable_zone method available");
        return (ISC_R_FAILURE);
    }

    result = state->writeable_zone(view, dlzdb, state->zone_name);
    if (result != ISC_R_SUCCESS) {
        if (state->log != NULL)
            state->log(ISC_LOG_ERROR, "dlz_example: failed to "
                   "configure zone %s", state->zone_name);
        return (result);
    }

    if (state->log != NULL)
        state->log(ISC_LOG_INFO, "dlz_example: configured writeable "
               "zone %s", state->zone_name);
    return (ISC_R_SUCCESS);
}

/*
 * Authorize a zone update
 */
isc_boolean_t
dlz_ssumatch(const char *signer, const char *name, const char *tcpaddr,
         const char *type, const char *key, isc_uint32_t keydatalen,
         unsigned char *keydata, void *dbdata)
{
    struct dlz_example_data *state = (struct dlz_example_data *)dbdata;

    UNUSED(tcpaddr);
    UNUSED(type);
    UNUSED(key);
    UNUSED(keydatalen);
    UNUSED(keydata);

    if (strncmp(name, "deny.", 5) == 0) {
        if (state->log != NULL)
            state->log(ISC_LOG_INFO, "dlz_example: denying update "
                   "of name=%s by %s", name, signer);
        return (ISC_FALSE);
    }
    if (state->log != NULL)
        state->log(ISC_LOG_INFO, "dlz_example: allowing update of "
               "name=%s by %s", name, signer);
    return (ISC_TRUE);
}


static isc_result_t
modrdataset(struct dlz_example_data *state, const char *name,
        const char *rdatastr, struct record *list)
{
    char *full_name, *dclass, *type, *data, *ttlstr, *buf;
    char absolute[1024];
    isc_result_t result;
#if defined(WIN32) || defined(_REENTRANT)
    char *saveptr = NULL;
#endif

    buf = strdup(rdatastr);
    if (buf == NULL)
        return (ISC_R_FAILURE);

    /*
     * The format is:
     * FULLNAME\tTTL\tDCLASS\tTYPE\tDATA
     *
     * The DATA field is space separated, and is in the data format
     * for the type used by dig
     */

    full_name = STRTOK_R(buf, "\t", &saveptr);
    if (full_name == NULL)
        goto error;

    ttlstr = STRTOK_R(NULL, "\t", &saveptr);
    if (ttlstr == NULL)
        goto error;

    dclass = STRTOK_R(NULL, "\t", &saveptr);
    if (dclass == NULL)
        goto error;

    type = STRTOK_R(NULL, "\t", &saveptr);
    if (type == NULL)
        goto error;

    data = STRTOK_R(NULL, "\t", &saveptr);
    if (data == NULL)
        goto error;

    if (name[strlen(name) - 1] != '.') {
        snprintf(absolute, sizeof(absolute), "%s.", name);
        name = absolute;
    }

    result = add_name(state, list, name, type,
              strtoul(ttlstr, NULL, 10), data);
    free(buf);
    return (result);

 error:
    free(buf);
    return (ISC_R_FAILURE);
}


isc_result_t
dlz_addrdataset(const char *name, const char *rdatastr,
        void *dbdata, void *version)
{
    struct dlz_example_data *state = (struct dlz_example_data *)dbdata;

    if (version != (void *) &state->transaction_started)
        return (ISC_R_FAILURE);

    if (state->log != NULL)
        state->log(ISC_LOG_INFO, "dlz_example: adding rdataset %s '%s'",
               name, rdatastr);

    return (modrdataset(state, name, rdatastr, &state->adds[0]));
}

isc_result_t
dlz_subrdataset(const char *name, const char *rdatastr,
        void *dbdata, void *version)
{
    struct dlz_example_data *state = (struct dlz_example_data *)dbdata;

    if (version != (void *) &state->transaction_started)
        return (ISC_R_FAILURE);

    if (state->log != NULL)
        state->log(ISC_LOG_INFO, "dlz_example: subtracting rdataset "
               "%s '%s'", name, rdatastr);

    return (modrdataset(state, name, rdatastr, &state->deletes[0]));
}

isc_result_t
dlz_delrdataset(const char *name, const char *type,
        void *dbdata, void *version)
{
    struct dlz_example_data *state = (struct dlz_example_data *)dbdata;

    if (version != (void *) &state->transaction_started)
        return (ISC_R_FAILURE);

    if (state->log != NULL)
        state->log(ISC_LOG_INFO, "dlz_example: deleting rdataset %s "
               "of type %s", name, type);

    return (ISC_R_SUCCESS);
}