krb5/os/locate_kdc.c

	locate_kdc.c revision 5e01956f3000408c2a2c5a08c8d0acf2c2a9d8ee
/*
 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*
 * lib/krb5/os/locate_kdc.c
 *
 * Copyright 1990,2000,2001,2002,2003,2004,2006 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.
 *
 *
 * get socket addresses for KDC.
 */

/*
 * Solaris Kerberos
 * Re-factored the following routines to get a clear separation of locating
 * KDC entries (krb5.conf/DNS-SRVrecs) versus mapping them to net addresses
 * to allow us to output better error msgs:
 *   krb5int_locate_server
 *   prof_locate_server
 *   dns_locate_server
 *   krb5_locate_srv_conf_1 (removed)
 *   krb5_locate_srv_dns_1  (removed)
 *   prof_hostnames2netaddrs (new)
 *   hostlist2str (new)
 *   dns_hostnames2netaddrs (new)
 *   dnslist2str (new)
 * Also, for the profile get_master==1 case, the algorithm has been
 * simplified to just do a profile_get_values on "admin_server" and
 * not try to match those against "kdc" entries (does not seem necessary
 * and the DNS-SRVrecs code does not do that).
 */

#include "fake-addrinfo.h"
#include "k5-int.h"
#include "os-proto.h"
#include <stdio.h>
#ifdef KRB5_DNS_LOOKUP
#ifdef WSHELPER
#include <wshelper.h>
#else /* WSHELPER */
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <resolv.h>
#include <netdb.h>
#endif /* WSHELPER */
#ifndef T_SRV
#define T_SRV 33
#endif /* T_SRV */
#include <syslog.h>
#include <locale.h>

/* for old Unixes and friends ... */
#ifndef MAXHOSTNAMELEN
#define MAXHOSTNAMELEN 64
#endif

#define MAX_DNS_NAMELEN (15*(MAXHOSTNAMELEN + 1)+1)

/* Solaris Kerberos: default to dns lookup for the KDC but not the realm */
#define DEFAULT_LOOKUP_KDC 1
#define DEFAULT_LOOKUP_REALM 0

static int
maybe_use_dns (krb5_context context, const char *name, int defalt)
{
    krb5_error_code code;
    char * value = NULL;
    int use_dns = 0;

    code = profile_get_string(context->profile, "libdefaults",
                              name, 0, 0, &value);
    if (value == 0 && code == 0)
    code = profile_get_string(context->profile, "libdefaults",
                  "dns_fallback", 0, 0, &value);
    if (code)
        return defalt;

    if (value == 0)
    return defalt;

    use_dns = _krb5_conf_boolean(value);
    profile_release_string(value);
    return use_dns;
}

int
_krb5_use_dns_kdc(krb5_context context)
{
    return maybe_use_dns (context, "dns_lookup_kdc", DEFAULT_LOOKUP_KDC);
}

int
_krb5_use_dns_realm(krb5_context context)
{
    return maybe_use_dns (context, "dns_lookup_realm", DEFAULT_LOOKUP_REALM);
}

#endif /* KRB5_DNS_LOOKUP */

int
krb5int_grow_addrlist (struct addrlist *lp, int nmore)
{
    int i;
    int newspace = lp->space + nmore;
    size_t newsize = newspace * sizeof (*lp->addrs);
    void *newaddrs;

    newaddrs = realloc (lp->addrs, newsize);
    if (newaddrs == NULL)
    return errno;
    lp->addrs = newaddrs;
    for (i = lp->space; i < newspace; i++) {
    lp->addrs[i].ai = NULL;
    lp->addrs[i].freefn = NULL;
    lp->addrs[i].data = NULL;
    }
    lp->space = newspace;
    return 0;
}
#define grow_list krb5int_grow_addrlist

/* Free up everything pointed to by the addrlist structure, but don't
   free the structure itself.  */
void
krb5int_free_addrlist (struct addrlist *lp)
{
    int i;
    for (i = 0; i < lp->naddrs; i++)
    if (lp->addrs[i].freefn)
        (lp->addrs[i].freefn)(lp->addrs[i].data);
    free (lp->addrs);
    lp->addrs = NULL;
    lp->naddrs = lp->space = 0;
}
#define free_list krb5int_free_addrlist

static int translate_ai_error (int err)
{
    switch (err) {
    case 0:
    return 0;
    case EAI_BADFLAGS:
    case EAI_FAMILY:
    case EAI_SOCKTYPE:
    case EAI_SERVICE:
    /* All of these indicate bad inputs to getaddrinfo.  */
    return EINVAL;
    case EAI_AGAIN:
    /* Translate to standard errno code.  */
    return EAGAIN;
    case EAI_MEMORY:
    /* Translate to standard errno code.  */
    return ENOMEM;
#ifdef EAI_ADDRFAMILY
    case EAI_ADDRFAMILY:
#endif
#if defined(EAI_NODATA) && EAI_NODATA != EAI_NONAME
    case EAI_NODATA:
#endif
    case EAI_NONAME:
    /* Name not known or no address data, but no error.  Do
       nothing more.  */
    return 0;
#ifdef EAI_OVERFLOW
    case EAI_OVERFLOW:
    /* An argument buffer overflowed.  */
    return EINVAL;      /* XXX */
#endif
#ifdef EAI_SYSTEM
    case EAI_SYSTEM:
    /* System error, obviously.  */
    return errno;
#endif
    default:
    /* An error code we haven't handled?  */
    return EINVAL;
    }
}

/* Solaris Kerberos: want dbg messages to syslog */
#include <stdarg.h>
static inline void Tprintf(const char *fmt, ...)
{
#ifdef TEST
    va_list ap;
    char err_str[2048];

    va_start(ap, fmt);
    vsnprintf(err_str, sizeof (err_str), fmt, args);
    syslog(LOG_DEBUG, err_str);
    va_end(ap);
#endif
}

#if 0
extern void krb5int_debug_fprint(const char *, ...);
#define dprint krb5int_debug_fprint
#define print_addrlist krb5int_print_addrlist
extern void print_addrlist (const struct addrlist *a);
#else
static inline void dprint(const char *fmt, ...) { }
static inline void print_addrlist(const struct addrlist *a) { }
#endif

static int add_addrinfo_to_list (struct addrlist *lp, struct addrinfo *a,
                 void (*freefn)(void *), void *data)
{
    int err;

    dprint("\tadding %p=%A to %p (naddrs=%d space=%d)\n", a, a, lp,
       lp->naddrs, lp->space);

    if (lp->naddrs == lp->space) {
    err = grow_list (lp, 1);
    if (err) {
        Tprintf ("grow_list failed %d\n", err);
        return err;
    }
    }
    Tprintf("setting element %d\n", lp->naddrs);
    lp->addrs[lp->naddrs].ai = a;
    lp->addrs[lp->naddrs].freefn = freefn;
    lp->addrs[lp->naddrs].data = data;
    lp->naddrs++;
    Tprintf ("\tcount is now %d: ", lp->naddrs);
    print_addrlist(lp);
    Tprintf("\n");
    return 0;
}

#define add_host_to_list krb5int_add_host_to_list

static void call_freeaddrinfo(void *data)
{
    /* Strict interpretation of the C standard says we can't assume
       that the ABI for f(void*) and f(struct foo *) will be
       compatible.  Use this stub just to be paranoid.  */
    freeaddrinfo(data);
}

int
krb5int_add_host_to_list (struct addrlist *lp, const char *hostname,
              int port, int secport,
              int socktype, int family)
{
    struct addrinfo *addrs, *a, *anext, hint;
    int err;
    char portbuf[10], secportbuf[10];
    void (*freefn)(void *);

    Tprintf ("adding hostname %s, ports %d,%d, family %d, socktype %d\n",
         hostname, ntohs (port), ntohs (secport),
         family, socktype);

    memset(&hint, 0, sizeof(hint));
    hint.ai_family = family;
    hint.ai_socktype = socktype;
#ifdef AI_NUMERICSERV
    hint.ai_flags = AI_NUMERICSERV;
#endif
    sprintf(portbuf, "%d", ntohs(port));
    sprintf(secportbuf, "%d", ntohs(secport));
    err = getaddrinfo (hostname, portbuf, &hint, &addrs);
    if (err) {
    Tprintf ("\tgetaddrinfo(\"%s\", \"%s\", ...)\n\treturns %d: %s\n",
         hostname, portbuf, err, gai_strerror (err));
    return translate_ai_error (err);
    }
    freefn = call_freeaddrinfo;
    anext = 0;
    for (a = addrs; a != 0 && err == 0; a = anext, freefn = 0) {
    anext = a->ai_next;
    err = add_addrinfo_to_list (lp, a, freefn, a);
    }
    if (err || secport == 0)
    goto egress;
    if (socktype == 0)
    socktype = SOCK_DGRAM;
    else if (socktype != SOCK_DGRAM)
    goto egress;
    hint.ai_family = AF_INET;
    err = getaddrinfo (hostname, secportbuf, &hint, &addrs);
    if (err) {
    err = translate_ai_error (err);
    goto egress;
    }
    freefn = call_freeaddrinfo;
    for (a = addrs; a != 0 && err == 0; a = anext, freefn = 0) {
    anext = a->ai_next;
    err = add_addrinfo_to_list (lp, a, freefn, a);
    }
egress:
    /* Solaris Kerberos */
    if (anext)
    freeaddrinfo (anext);
    return err;
}

#include <locate_plugin.h>

#if TARGET_OS_MAC
static const char *objdirs[] = { KRB5_PLUGIN_BUNDLE_DIR, LIBDIR "/krb5/plugins/libkrb5", NULL }; /* should be a list */
#else
static const char *objdirs[] = { LIBDIR "/krb5/plugins/libkrb5", NULL };
#endif

struct module_callback_data {
    int out_of_mem;
    struct addrlist *lp;
};

static int
module_callback (void *cbdata, int socktype, struct sockaddr *sa)
{
    struct module_callback_data *d = cbdata;
    struct {
    struct addrinfo ai;
    union {
        struct sockaddr_in sin;
        struct sockaddr_in6 sin6;
    } u;
    } *x;

    if (socktype != SOCK_STREAM && socktype != SOCK_DGRAM)
    return 0;
    if (sa->sa_family != AF_INET && sa->sa_family != AF_INET6)
    return 0;
    x = malloc (sizeof (*x));
    if (x == 0) {
    d->out_of_mem = 1;
    return 1;
    }
    memset(x, 0, sizeof (*x));
    x->ai.ai_addr = (struct sockaddr *) &x->u;
    x->ai.ai_socktype = socktype;
    x->ai.ai_family = sa->sa_family;
    if (sa->sa_family == AF_INET) {
    x->u.sin = *(struct sockaddr_in *)sa;
    x->ai.ai_addrlen = sizeof(struct sockaddr_in);
    }
    if (sa->sa_family == AF_INET6) {
    x->u.sin6 = *(struct sockaddr_in6 *)sa;
    x->ai.ai_addrlen = sizeof(struct sockaddr_in6);
    }
    if (add_addrinfo_to_list (d->lp, &x->ai, free, x) != 0) {
    /* Assumes only error is ENOMEM.  */
    d->out_of_mem = 1;
    return 1;
    }
    return 0;
}

static krb5_error_code
module_locate_server (krb5_context ctx, const krb5_data *realm,
              struct addrlist *addrlist,
              enum locate_service_type svc, int socktype, int family)
{
    struct krb5plugin_service_locate_result *res = NULL;
    krb5_error_code code;
    struct krb5plugin_service_locate_ftable *vtbl = NULL;
    void **ptrs;
    int i;
    struct module_callback_data cbdata = { 0, };

    Tprintf("in module_locate_server\n");
    cbdata.lp = addrlist;
    if (!PLUGIN_DIR_OPEN (&ctx->libkrb5_plugins)) {

    code = krb5int_open_plugin_dirs (objdirs, NULL, &ctx->libkrb5_plugins,
                     &ctx->err);
    if (code)
        return KRB5_PLUGIN_NO_HANDLE;
    }

    code = krb5int_get_plugin_dir_data (&ctx->libkrb5_plugins,
                    "service_locator", &ptrs, &ctx->err);
    if (code) {
    Tprintf("error looking up plugin symbols: %s\n",
        krb5_get_error_message(ctx, code));
    return KRB5_PLUGIN_NO_HANDLE;
    }

    for (i = 0; ptrs[i]; i++) {
    void *blob;

    vtbl = ptrs[i];
    Tprintf("element %d is %p\n", i, ptrs[i]);

    /* For now, don't keep the plugin data alive.  For long-lived
       contexts, it may be desirable to change that later.  */
    code = vtbl->init(ctx, &blob);
    if (code)
        continue;

    code = vtbl->lookup(blob, svc, realm->data, socktype, family,
                module_callback, &cbdata);
    vtbl->fini(blob);
    if (code == KRB5_PLUGIN_NO_HANDLE) {
        /* Module passes, keep going.  */
        /* XXX */
        Tprintf("plugin doesn't handle this realm (KRB5_PLUGIN_NO_HANDLE)\n");
        continue;
    }
    if (code != 0) {
        /* Module encountered an actual error.  */
        Tprintf("plugin lookup routine returned error %d: %s\n",
            code, error_message(code));
        krb5int_free_plugin_dir_data (ptrs);
        return code;
    }
    break;
    }
    if (ptrs[i] == NULL) {
    Tprintf("ran off end of plugin list\n");
    krb5int_free_plugin_dir_data (ptrs);
    return KRB5_PLUGIN_NO_HANDLE;
    }
    Tprintf("stopped with plugin #%d, res=%p\n", i, res);

    /* Got something back, yippee.  */
    Tprintf("now have %d addrs in list %p\n", addrlist->naddrs, addrlist);
    print_addrlist(addrlist);
    krb5int_free_plugin_dir_data (ptrs);
    return 0;
}

static krb5_error_code
prof_locate_server (krb5_context context, const krb5_data *realm,
            char ***hostlist,
            enum locate_service_type svc)
{
    const char  *realm_srv_names[4];
    char **hl, *host, *profname;
    krb5_error_code code;
    int i, j, count;

    *hostlist = NULL;  /* default - indicate no KDCs found */

    switch (svc) {
    case locate_service_kdc:
    profname = "kdc";
    break;
    case locate_service_master_kdc:
        profname = "master_kdc";
    break;
    case locate_service_kadmin:
    profname = "admin_server";
    break;
    case locate_service_krb524:
    profname = "krb524_server";
    break;
    case locate_service_kpasswd:
    profname = "kpasswd_server";
    break;
    default:
    return EINVAL;
    }

    if ((host = malloc(realm->length + 1)) == NULL)
    return ENOMEM;

    (void) strncpy(host, realm->data, realm->length);
    host[realm->length] = '\0';
    hl = 0;

    realm_srv_names[0] = "realms";
    realm_srv_names[1] = host;
    realm_srv_names[2] = profname;
    realm_srv_names[3] = 0;

    code = profile_get_values(context->profile, realm_srv_names, &hl);
    if (code) {
    Tprintf ("config file lookup failed: %s\n",
         error_message(code));
        if (code == PROF_NO_SECTION || code == PROF_NO_RELATION)
        code = KRB5_REALM_UNKNOWN;
    krb5_xfree(host);
    return code;
     }
    krb5_xfree(host);

    *hostlist = hl;

    return 0;
}

static krb5_error_code
dns_locate_server (krb5_context context, const krb5_data *realm,
        struct srv_dns_entry **dns_list_head,
        enum locate_service_type svc, int socktype, int family)
{
    const char *dnsname;
    int use_dns = _krb5_use_dns_kdc(context);
    krb5_error_code code;
    struct srv_dns_entry *head = NULL;

    *dns_list_head = NULL; /* default: indicate we have found no KDCs */

    if (!use_dns)
    return KRB5_PLUGIN_NO_HANDLE;

    switch (svc) {
    case locate_service_kdc:
    dnsname = "_kerberos";
    break;
    case locate_service_master_kdc:
    dnsname = "_kerberos-master";
    break;
    case locate_service_kadmin:
    dnsname = "_kerberos-adm";
    break;
    case locate_service_krb524:
    dnsname = "_krb524";
    break;
    case locate_service_kpasswd:
    dnsname = "_kpasswd";
    break;
    default:
    return KRB5_PLUGIN_NO_HANDLE;
    }

    code = 0;
    if (socktype == SOCK_DGRAM || socktype == 0) {
    code = krb5int_make_srv_query_realm(realm, dnsname, "_udp", &head);
    if (code)
        Tprintf("dns udp lookup returned error %d\n", code);
    }
    if ((socktype == SOCK_STREAM || socktype == 0) && code == 0) {
    code = krb5int_make_srv_query_realm(realm, dnsname, "_tcp", &head);
    if (code)
        Tprintf("dns tcp lookup returned error %d\n", code);
    }

    if (head == NULL)
    return 0;

    /* Check for the "." case indicating no support.  */
    if (head->next == 0 && head->host[0] == 0) {
    free(head->host);
    free(head);
    return KRB5_ERR_NO_SERVICE;
    }

    /*
     * Okay!  Now we've got a linked list of entries sorted by
     * priority.  Return it so later we can map hostnames to net addresses.
     */
    *dns_list_head = head;

    return 0;
}

/*
 * Given the list of hostnames of KDCs found in DNS SRV recs, lets go
 * thru NSS (name svc switch) to get the net addrs.
 */
static krb5_error_code
dns_hostnames2netaddrs(
    struct srv_dns_entry *head,
    enum locate_service_type svc,
    int socktype,
    int family,
    struct addrlist *addrlist)
{
    struct srv_dns_entry *entry = NULL, *next;
    krb5_error_code code;

    Tprintf ("walking answer list:\n");
    for (entry = head; entry != NULL; entry = entry->next) {
    code = 0;
    if (socktype)
        code = add_host_to_list (addrlist, entry->host,
                    htons (entry->port), 0,
                    socktype, family);
    else {
        (void) add_host_to_list (addrlist, entry->host,
                    htons (entry->port), 0,
                    SOCK_DGRAM, family);

        code = add_host_to_list (addrlist, entry->host,
                    htons (entry->port), 0,
                    SOCK_STREAM, family);
    }
        if (code) {
        Tprintf("  fail add_host code=%d %s\n", code, entry->host);
        }
    }
    Tprintf ("[end]\n");

    return code;
}

/*
 * Given the DNS SRV recs list, return a string of all the hosts like so:
 *     "fqdn0[,fqdn1][,fqdnN]"
 */
static char *
dnslist2str(struct srv_dns_entry *dns_list_head)
{
    struct srv_dns_entry *head = dns_list_head;
    struct srv_dns_entry *entry = NULL, *next;
    unsigned int size = 0, c = 0, buf_size;
    char *s = NULL;

    for (entry = head; entry; entry = entry->next, c++) {
        size += strlen(entry->host);
    }
    if (!c)
        return NULL;

    /* hostnames + commas + NULL */
    buf_size = size + (c - 1) + 1;
    s = malloc(buf_size);
    if (!s)
        return NULL;

    (void) strlcpy(s, head->host, buf_size);
    for (entry = head->next; entry; entry = entry->next) {
        (void) strlcat(s, ",", buf_size);
        (void) strlcat(s, entry->host, buf_size);
    }

    return s;
}

/*
 * Given the profile hostlist, return a string of all the hosts like so:
 *     "fqdn0[,fqdn1][,fqdnN]"
 */
static char *
hostlist2str(char **hostlist)
{
    unsigned int c = 0, size = 0, buf_size;
    char **hl = hostlist, *s = NULL;

    while (hl && *hl) {
        size += strlen(*hl);
        hl++;
        c++;
    }
    if (!c)
        return NULL;

    /* hostnames + commas + NULL */
    buf_size = size + (c - 1) + 1;
    s = malloc(buf_size);
    if (!s)
        return NULL;

    hl = hostlist;
    (void) strlcpy(s, *hl, buf_size);
    hl++;
    while (hl && *hl) {
        (void) strlcat(s, ",", buf_size);
        (void) strlcat(s, *hl, buf_size);
        hl++;
    }

    return s;
}

/*
 * Take the profile KDC list and return a list of net addrs.
 */
static krb5_error_code
prof_hostnames2netaddrs(
    char **hostlist,
    enum locate_service_type svc,
    int socktype,
    int family,
    struct addrlist *addrlist) /* output */
{
    int udpport  = 0 , sec_udpport = 0;
    int code, i;
    struct servent *serv;

    int count = 0;
    while (hostlist && hostlist[count])
        count++;
    if (count == 0) {
        return 0;
    }

    switch (svc) {
    case locate_service_kdc:
    case locate_service_master_kdc:
    /* We used to use /etc/services for these, but enough systems
       have old, crufty, wrong settings that this is probably
       better.  */
    udpport = htons(KRB5_DEFAULT_PORT);
    sec_udpport = htons(KRB5_DEFAULT_SEC_PORT);
    break;
    case locate_service_kadmin:
    udpport = htons(DEFAULT_KADM5_PORT);
    break;
    case locate_service_krb524:
    serv = getservbyname(KRB524_SERVICE, "udp");
    udpport = serv ? serv->s_port : htons (KRB524_PORT);
    break;
    case locate_service_kpasswd:
    udpport = htons(DEFAULT_KPASSWD_PORT);
    break;
    default:
    return EINVAL;
    }

    for (i=0; hostlist[i]; i++) {
    int p1, p2;
    char *cp, *port, *host;

    host = hostlist[i];
    /*
     * Strip off excess whitespace
     */
    cp = strchr(host, ' ');
    if (cp)
        *cp = 0;
    cp = strchr(host, '\t');
    if (cp)
        *cp = 0;
    port = strchr(host, ':');
    if (port) {
        *port = 0;
        port++;
    }

    if (port) {
        unsigned long l;
#ifdef HAVE_STROUL
        char *endptr;
        l = strtoul (port, &endptr, 10);
        if (endptr == NULL || *endptr != 0)
        return EINVAL;
#else
        l = atoi (port);
#endif
        /* L is unsigned, don't need to check <0.  */
        if (l == 0 || l > 65535)
        return EINVAL;
        p1 = htons (l);
        p2 = 0;
    } else {
        p1 = udpport;
        p2 = sec_udpport;
    }


    if (socktype != 0) {
        code = add_host_to_list (addrlist, hostlist[i], p1, p2,
                     socktype, family);
    } else {
        code = add_host_to_list (addrlist, hostlist[i], p1, p2,
                     SOCK_DGRAM, family);
        if (code == 0)
        code = add_host_to_list (addrlist, hostlist[i], p1, p2,
                     SOCK_STREAM, family);
    }
    }

    return code;
}

/*
 * Wrapper function for the various backends
 */

krb5_error_code
krb5int_locate_server (krb5_context context, const krb5_data *realm,
               struct addrlist *addrlist,
               enum locate_service_type svc,
               int socktype, int family)
{
    krb5_error_code code;
    struct addrlist al = ADDRLIST_INIT;
    char **hostlist = NULL;
    struct srv_dns_entry *dns_list_head = NULL;

    *addrlist = al;

    code = module_locate_server(context, realm, &al, svc, socktype, family);
    Tprintf("module_locate_server returns %d\n", code);
    if (code == KRB5_PLUGIN_NO_HANDLE) {
    /*
     * We always try the local file before DNS.  Note that there
     * is no way to indicate "service not available" via the
     * config file.
     */
    code = prof_locate_server(context, realm, &hostlist, svc);

    /*
     * Solaris Kerberos:
     * If kpasswd_server has not been configured and dns_lookup_kdc -
     * dns_fallback are not configured then admin_server should
     * be inferred, per krb5.conf(4).
     */
    if (code && svc == locate_service_kpasswd &&
        !maybe_use_dns(context, "dns_lookup_kdc", 0)) {
        code = prof_locate_server(context, realm, &hostlist,
            locate_service_kadmin);
    }

#ifdef KRB5_DNS_LOOKUP
    /*
     * Solaris Kerberos:
     * There is no point in trying to locate the KDC in DNS if "realm"
     * is empty.
     */
    /* Try DNS for all profile errors?  */
    if (code && !krb5_is_referral_realm(realm)) {
        krb5_error_code code2;
        code2 = dns_locate_server(context, realm, &dns_list_head,
                    svc, socktype, family);

        if (code2 != KRB5_PLUGIN_NO_HANDLE)
        code = code2;
    }
#endif /* KRB5_DNS_LOOKUP */

    /* We could put more heuristics here, like looking up a hostname
       of "kerberos."+REALM, etc.  */
    }

    if (code != 0) {
    if (al.space)
        free_list (&al);
    if (hostlist)
        profile_free_list(hostlist);
    if (dns_list_head)
        krb5int_free_srv_dns_data(dns_list_head);

    return code;
    }

    /*
     * At this point we have no errors, let's check to see if we have
     * any KDC entries from krb5.conf or DNS.
     */
    if (!hostlist && !dns_list_head) {
    switch(svc) {
    case locate_service_master_kdc:
        krb5_set_error_message(context,
                KRB5_REALM_CANT_RESOLVE,
                dgettext(TEXT_DOMAIN,
                    "Cannot find a master KDC entry in krb5.conf(4) or DNS Service Location records for realm '%.*s'"),
                realm->length, realm->data);
        break;
    case locate_service_kadmin:
        krb5_set_error_message(context,
                KRB5_REALM_CANT_RESOLVE,
                dgettext(TEXT_DOMAIN,
                    "Cannot find a kadmin KDC entry in krb5.conf(4) or DNS Service Location records for realm '%.*s'"),
                realm->length, realm->data);
        break;
    case locate_service_kpasswd:
        krb5_set_error_message(context,
                KRB5_REALM_CANT_RESOLVE,
                dgettext(TEXT_DOMAIN,
                    "Cannot find a kpasswd KDC entry in krb5.conf(4) or DNS Service Location records for realm '%.*s'"),
                realm->length, realm->data);
        break;
    default:      /*  locate_service_kdc: */
        krb5_set_error_message(context,
                    KRB5_REALM_CANT_RESOLVE,
                    dgettext(TEXT_DOMAIN,
                        "Cannot find any KDC entries in krb5.conf(4) or DNS Service Location records for realm '%.*s'"),
                    realm->length, realm->data);

    }
    return KRB5_REALM_CANT_RESOLVE;
    }

    /* We have KDC entries, let see if we can get their net addrs. */
    if (hostlist)
    code = prof_hostnames2netaddrs(hostlist, svc,
                    socktype, family, &al);
    else if (dns_list_head)
    code = dns_hostnames2netaddrs(dns_list_head, svc,
                    socktype, family, &al);
    if (code) {
    if (hostlist)
        profile_free_list(hostlist);
    if (dns_list_head)
        krb5int_free_srv_dns_data(dns_list_head);
    return code;
    }

    /*
     * Solaris Kerberos:
     * If an entry for _kerberos-master. does not exist (checked for
     * above) but _kpasswd. does then treat that as an entry for the
     * master KDC (but use port 88 not the kpasswd port). MS AD creates
     * kpasswd entries by default in DNS.
     */
    if (!dns_list_head && svc == locate_service_master_kdc &&
    al.naddrs == 0) {

    /* Look for _kpasswd._tcp|udp */
    code = dns_locate_server(context, realm, &dns_list_head,
                locate_service_kpasswd, socktype, family);

    if (code == 0 && dns_list_head) {
        int i;
        struct addrinfo *a;

        code = dns_hostnames2netaddrs(dns_list_head, svc,
                    socktype, family, &al);

        /* Set the port to 88 instead of the kpasswd port */
        if (code == 0 && al.naddrs > 0) {
        for (i = 0; i < al.naddrs; i++) {
            if (al.addrs[i].ai->ai_family == AF_INET)
            for (a = al.addrs[i].ai; a != NULL; a = a->ai_next)
                ((struct sockaddr_in *)a->ai_addr)->sin_port =
                htons(KRB5_DEFAULT_PORT);

            if (al.addrs[i].ai->ai_family == AF_INET6)
            for (a = al.addrs[i].ai; a != NULL; a = a->ai_next)
                 ((struct sockaddr_in6 *)a->ai_addr)->sin6_port =
                    htons(KRB5_DEFAULT_PORT);
        }
        }
    }
    }

    /* No errors so far, lets see if we have KDC net addrs */
    if (al.naddrs == 0) {
    char *hostlist_str = NULL, *dnslist_str  = NULL;
    if (al.space)
        free_list (&al);

    if (hostlist) {
        hostlist_str = hostlist2str(hostlist);
        krb5_set_error_message(context, KRB5_REALM_CANT_RESOLVE,
                dgettext(TEXT_DOMAIN,
                    "Cannot resolve network address for KDCs '%s' specified in krb5.conf(4) for realm %.*s"),
                hostlist_str ? hostlist_str : "unknown",
                realm->length, realm->data);
        if (hostlist_str)
        free(hostlist_str);
    } else if (dns_list_head) {
        dnslist_str = dnslist2str(dns_list_head);
        krb5_set_error_message(context, KRB5_REALM_CANT_RESOLVE,
                dgettext(TEXT_DOMAIN,
                    "Cannot resolve network address for KDCs '%s' discovered via DNS Service Location records for realm '%.*s'"),
                dnslist_str ? dnslist_str : "unknown",
                realm->length, realm->data);
        if (dnslist_str)
            free(dnslist_str);
    }

    if (hostlist)
        profile_free_list(hostlist);
    if (dns_list_head)
        krb5int_free_srv_dns_data(dns_list_head);

    return KRB5_REALM_CANT_RESOLVE;
    }

    if (hostlist)
        profile_free_list(hostlist);
    if (dns_list_head)
        krb5int_free_srv_dns_data(dns_list_head);

    *addrlist = al;
    return 0;
}

krb5_error_code
krb5_locate_kdc(krb5_context context, const krb5_data *realm,
        struct addrlist *addrlist,
        int get_masters, int socktype, int family)
{
    return krb5int_locate_server(context, realm, addrlist,
                 (get_masters
                  ? locate_service_master_kdc
                  : locate_service_kdc),
                 socktype, family);
}

/*
 * Solaris Kerberos: for backward compat.  Avoid using this
 * function!
 */
krb5_error_code
krb5_get_servername(krb5_context context,
    const krb5_data *realm,
    const char *name, const char *proto,
    char *srvhost,
    unsigned short *port)
{
    krb5_error_code code = KRB5_REALM_UNKNOWN;

#ifdef KRB5_DNS_LOOKUP
    {
    int use_dns = _krb5_use_dns_kdc(context);

    if (use_dns) {
        struct srv_dns_entry *head = NULL;

        code = krb5int_make_srv_query_realm(realm, name, proto, &head);
        if (code)
        return (code);

        if (head == NULL)
        return KRB5_REALM_CANT_RESOLVE;

        *port = head->port;
        (void) strlcpy(srvhost, head->host, MAX_DNS_NAMELEN);

#ifdef DEBUG
        fprintf (stderr, "krb5_get_servername svrhost %s, port %d\n",
        srvhost, *port);
#endif
        krb5int_free_srv_dns_data(head);
    }
    }
#endif /* KRB5_DNS_LOOKUP */

    return (code);
}