radsecproxy.c

/*
 * Copyright (C) 2006-2009 Stig Venaas <venaas@uninett.no>
 * Copyright (C) 2010,2011,2012 NORDUnet A/S
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 */

/* Code contributions from:
 *
 * Arne Schwabe <schwabe at uni-paderborn.de>
 * Maja Wolniewicz <mgw@umk.pl>
 * Simon Leinen <simon.leinen@switch.ch>
 * Stefan Winter <stefan.winter@restena.lu>
 */

/* For UDP there is one server instance consisting of udpserverrd and udpserverth
 *              rd is responsible for init and launching wr
 * For TLS there is a server instance that launches tlsserverrd for each TLS peer
 *          each tlsserverrd launches tlsserverwr
 * For each UDP/TLS peer there is clientrd and clientwr, clientwr is responsible
 *          for init and launching rd
 *
 * serverrd will receive a request, processes it and puts it in the requestq of
 *          the appropriate clientwr
 * clientwr monitors its requestq and sends requests
 * clientrd looks for responses, processes them and puts them in the replyq of
 *          the peer the request came from
 * serverwr monitors its reply and sends replies
 *
 * In addition to the main thread, we have:
 * If UDP peers are configured, there will be 2 + 2 * #peers UDP threads
 * If TLS peers are configured, there will initially be 2 * #peers TLS threads
 * For each TLS peer connecting to us there will be 2 more TLS threads
 *       This is only for connected peers
 * Example: With 3 UDP peers and 30 TLS peers, there will be a max of
 *          1 + (2 + 2 * 3) + (2 * 30) + (2 * 30) = 129 threads
 */

/* Bugs:
 * May segfault when dtls connections go down? More testing needed
 * Remove expired stuff from clients request list?
 * Multiple outgoing connections if not enough IDs? (multiple servers per conf?)
 * Useful for TCP accounting? Now we require separate server config for alt port
 */

#include <signal.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#ifdef SYS_SOLARIS9
#include <fcntl.h>
#endif
#include <sys/time.h>
#include <sys/types.h>
#include <ctype.h>
#include <sys/wait.h>
#include <arpa/inet.h>
#include <regex.h>
#include <libgen.h>
#include <pthread.h>
#include <errno.h>
#include <assert.h>
#include <openssl/ssl.h>
#include <openssl/rand.h>
#include <openssl/err.h>
#include <openssl/md5.h>
#include "debug.h"
#include "hash.h"
#include "util.h"
#include "hostport.h"
#include "radsecproxy.h"
#include "udp.h"
#include "tcp.h"
#include "tls.h"
#include "dtls.h"
#if defined(WANT_FTICKS)
#include "fticks.h"
#endif

static struct options options;
static struct list *clconfs, *srvconfs;
static struct list *realms;
static struct hash *rewriteconfs;

static pthread_mutex_t *ssl_locks = NULL;
static long *ssl_lock_count;
extern int optind;
extern char *optarg;
static const struct protodefs *protodefs[RAD_PROTOCOUNT];

/* minimum required declarations to avoid reordering code */
struct realm *adddynamicrealmserver(struct realm *realm, char *id);
int dynamicconfig(struct server *server);
int confserver_cb(struct gconffile **cf, void *arg, char *block, char *opt, char *val);
void freerealm(struct realm *realm);
void freeclsrvconf(struct clsrvconf *conf);
void freerq(struct request *rq);
void freerqoutdata(struct rqout *rqout);
void rmclientrq(struct request *rq, uint8_t id);

static const struct protodefs *(*protoinits[])(uint8_t) = { udpinit, tlsinit, tcpinit, dtlsinit };

uint8_t protoname2int(const char *name) {
    uint8_t i;

    for (i = 0; i < RAD_PROTOCOUNT; i++)
	if (protodefs[i] && protodefs[i]->name && !strcasecmp(protodefs[i]->name, name))
	    return i;
    return 255;
}

/* callbacks for making OpenSSL thread safe */
unsigned long ssl_thread_id() {
    return (unsigned long)pthread_self();
}

void ssl_locking_callback(int mode, int type, const char *file, int line) {
    if (mode & CRYPTO_LOCK) {
	pthread_mutex_lock(&ssl_locks[type]);
	ssl_lock_count[type]++;
    } else
	pthread_mutex_unlock(&ssl_locks[type]);
}

/* returns 1 if the len first bits are equal, else 0 */
int prefixmatch(void *a1, void *a2, uint8_t len) {
    static uint8_t mask[] = { 0, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe };
    uint8_t r, l = len / 8;
    if (l && memcmp(a1, a2, l))
	return 0;
    r = len % 8;
    if (!r)
	return 1;
    return (((uint8_t *)a1)[l] & mask[r]) == (((uint8_t *)a2)[l] & mask[r]);
}

/* returns next config with matching address, or NULL */
struct clsrvconf *find_conf(uint8_t type, struct sockaddr *addr, struct list *confs, struct list_node **cur, uint8_t server_p) {
    struct list_node *entry;
    struct clsrvconf *conf;

    for (entry = (cur && *cur ? list_next(*cur) : list_first(confs)); entry; entry = list_next(entry)) {
	conf = (struct clsrvconf *)entry->data;
	if (conf->type == type && addressmatches(conf->hostports, addr, server_p)) {
	    if (cur)
		*cur = entry;
	    return conf;
	}
    }
    return NULL;
}

struct clsrvconf *find_clconf(uint8_t type, struct sockaddr *addr, struct list_node **cur) {
    return find_conf(type, addr, clconfs, cur, 0);
}

struct clsrvconf *find_srvconf(uint8_t type, struct sockaddr *addr, struct list_node **cur) {
    return find_conf(type, addr, srvconfs, cur, 1);
}

/* returns next config of given type, or NULL */
struct clsrvconf *find_clconf_type(uint8_t type, struct list_node **cur) {
    struct list_node *entry;
    struct clsrvconf *conf;

    for (entry = (cur && *cur ? list_next(*cur) : list_first(clconfs)); entry; entry = list_next(entry)) {
	conf = (struct clsrvconf *)entry->data;
	if (conf->type == type) {
	    if (cur)
		*cur = entry;
	    return conf;
	}
    }
    return NULL;
}

struct gqueue *newqueue() {
    struct gqueue *q;

    q = malloc(sizeof(struct gqueue));
    if (!q)
	debugx(1, DBG_ERR, "malloc failed");
    q->entries = list_create();
    if (!q->entries)
	debugx(1, DBG_ERR, "malloc failed");
    pthread_mutex_init(&q->mutex, NULL);
    pthread_cond_init(&q->cond, NULL);
    return q;
}

void removequeue(struct gqueue *q) {
    struct list_node *entry;

    if (!q)
	return;
    pthread_mutex_lock(&q->mutex);
    for (entry = list_first(q->entries); entry; entry = list_next(entry))
	freerq((struct request *)entry);
    list_destroy(q->entries);
    pthread_cond_destroy(&q->cond);
    pthread_mutex_unlock(&q->mutex);
    pthread_mutex_destroy(&q->mutex);
    free(q);
}

void freebios(struct gqueue *q) {
    BIO *bio;

    pthread_mutex_lock(&q->mutex);
    while ((bio = (BIO *)list_shift(q->entries)))
	BIO_free(bio);
    pthread_mutex_unlock(&q->mutex);
    removequeue(q);
}

struct client *addclient(struct clsrvconf *conf, uint8_t lock) {
    struct client *new = malloc(sizeof(struct client));

    if (!new) {
	debug(DBG_ERR, "malloc failed");
	return NULL;
    }

    if (lock)
	pthread_mutex_lock(conf->lock);
    if (!conf->clients) {
	conf->clients = list_create();
	if (!conf->clients) {
	    if (lock)
		pthread_mutex_unlock(conf->lock);
	    debug(DBG_ERR, "malloc failed");
	    return NULL;
	}
    }

    memset(new, 0, sizeof(struct client));
    new->conf = conf;
    if (conf->pdef->addclient)
	conf->pdef->addclient(new);
    else
	new->replyq = newqueue();
    list_push(conf->clients, new);
    if (lock)
	pthread_mutex_unlock(conf->lock);
    return new;
}

void removeclientrqs_sendrq_freeserver_lock(uint8_t wantlock) {
    static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;

    if (wantlock)
	pthread_mutex_lock(&lock);
    else
	pthread_mutex_unlock(&lock);
}

void removeclientrqs(struct client *client) {
    struct request *rq;
    struct rqout *rqout;
    int i;

    removeclientrqs_sendrq_freeserver_lock(1);
    for (i = 0; i < MAX_REQUESTS; i++) {
	rq = client->rqs[i];
	if (!rq)
	    continue;
	if (rq->to) {
	    rqout = rq->to->requests + rq->newid;
	    pthread_mutex_lock(rqout->lock);
	    if (rqout->rq == rq) /* still pointing to our request */
		freerqoutdata(rqout);
	    pthread_mutex_unlock(rqout->lock);
	}
	freerq(rq);
    }
    removeclientrqs_sendrq_freeserver_lock(0);
}

void removelockedclient(struct client *client) {
    struct clsrvconf *conf;

    conf = client->conf;
    if (conf->clients) {
	removeclientrqs(client);
	removequeue(client->replyq);
	list_removedata(conf->clients, client);
	free(client->addr);
	free(client);
    }
}

void removeclient(struct client *client) {
    struct clsrvconf *conf;

    if (!client)
	return;

    conf = client->conf;
    pthread_mutex_lock(conf->lock);
    removelockedclient(client);
    pthread_mutex_unlock(conf->lock);
}

void freeserver(struct server *server, uint8_t destroymutex) {
    struct rqout *rqout, *end;

    if (!server)
	return;

    removeclientrqs_sendrq_freeserver_lock(1);
    if (server->requests) {
	rqout = server->requests;
	for (end = rqout + MAX_REQUESTS; rqout < end; rqout++) {
	    if (rqout->rq)
		rqout->rq->to = NULL;
	    freerqoutdata(rqout);
	    pthread_mutex_destroy(rqout->lock);
	    free(rqout->lock);
	}
	free(server->requests);
    }
    if (server->rbios)
	freebios(server->rbios);
    free(server->dynamiclookuparg);
    if (server->ssl) {
#if defined ENABLE_EXPERIMENTAL_DYNDISC
        if (server->sock >= 0)
            close(server->sock);
#endif
        SSL_free(server->ssl);
    }
    if (destroymutex) {
	pthread_mutex_destroy(&server->lock);
	pthread_cond_destroy(&server->newrq_cond);
	pthread_mutex_destroy(&server->newrq_mutex);
    }
    removeclientrqs_sendrq_freeserver_lock(0);
    free(server);
}

int addserver(struct clsrvconf *conf) {
    int i;

    if (conf->servers) {
	debug(DBG_ERR, "addserver: currently works with just one server per conf");
	return 0;
    }
    conf->servers = malloc(sizeof(struct server));
    if (!conf->servers) {
	debug(DBG_ERR, "malloc failed");
	return 0;
    }
    memset(conf->servers, 0, sizeof(struct server));
    conf->servers->conf = conf;

#ifdef RADPROT_DTLS
    if (conf->type == RAD_DTLS)
	conf->servers->rbios = newqueue();
#endif
    conf->pdef->setsrcres();

    conf->servers->sock = -1;
    if (conf->pdef->addserverextra)
	conf->pdef->addserverextra(conf);

    conf->servers->requests = calloc(MAX_REQUESTS, sizeof(struct rqout));
    if (!conf->servers->requests) {
	debug(DBG_ERR, "malloc failed");
	goto errexit;
    }
    for (i = 0; i < MAX_REQUESTS; i++) {
	conf->servers->requests[i].lock = malloc(sizeof(pthread_mutex_t));
	if (!conf->servers->requests[i].lock) {
	    debug(DBG_ERR, "malloc failed");
	    goto errexit;
	}
	if (pthread_mutex_init(conf->servers->requests[i].lock, NULL)) {
	    debugerrno(errno, DBG_ERR, "mutex init failed");
	    free(conf->servers->requests[i].lock);
	    conf->servers->requests[i].lock = NULL;
	    goto errexit;
	}
    }
    if (pthread_mutex_init(&conf->servers->lock, NULL)) {
	debugerrno(errno, DBG_ERR, "mutex init failed");
	goto errexit;
    }
    conf->servers->newrq = 0;
    if (pthread_mutex_init(&conf->servers->newrq_mutex, NULL)) {
	debugerrno(errno, DBG_ERR, "mutex init failed");
	pthread_mutex_destroy(&conf->servers->lock);
	goto errexit;
    }
    if (pthread_cond_init(&conf->servers->newrq_cond, NULL)) {
	debugerrno(errno, DBG_ERR, "mutex init failed");
	pthread_mutex_destroy(&conf->servers->newrq_mutex);
	pthread_mutex_destroy(&conf->servers->lock);
	goto errexit;
    }

    return 1;

errexit:
    freeserver(conf->servers, 0);
    conf->servers = NULL;
    return 0;
}

unsigned char *attrget(unsigned char *attrs, int length, uint8_t type) {
    while (length > 1) {
	if (ATTRTYPE(attrs) == type)
	    return attrs;
	length -= ATTRLEN(attrs);
	attrs += ATTRLEN(attrs);
    }
    return NULL;
}

struct request *newrqref(struct request *rq) {
    if (rq)
	rq->refcount++;
    return rq;
}

void freerq(struct request *rq) {
    if (!rq)
	return;
    debug(DBG_DBG, "freerq: called with refcount %d", rq->refcount);
    if (--rq->refcount)
	return;
    if (rq->origusername)
	free(rq->origusername);
    if (rq->buf)
	free(rq->buf);
    if (rq->replybuf)
	free(rq->replybuf);
    if (rq->msg)
	radmsg_free(rq->msg);
    free(rq);
}

void freerqoutdata(struct rqout *rqout) {
    if (!rqout)
	return;
    if (rqout->rq) {
	if (rqout->rq->buf) {
	    free(rqout->rq->buf);
	    rqout->rq->buf = NULL;
	}
	freerq(rqout->rq);
	rqout->rq = NULL;
    }
    rqout->tries = 0;
    memset(&rqout->expiry, 0, sizeof(struct timeval));
}

void sendrq(struct request *rq) {
    int i, start;
    struct server *to;

    removeclientrqs_sendrq_freeserver_lock(1);
    to = rq->to;
    if (!to)
	goto errexit;

    start = to->conf->statusserver ? 1 : 0;
    pthread_mutex_lock(&to->newrq_mutex);
    if (start && rq->msg->code == RAD_Status_Server) {
	pthread_mutex_lock(to->requests[0].lock);
	if (to->requests[0].rq) {
	    pthread_mutex_unlock(to->requests[0].lock);
	    debug(DBG_INFO, "sendrq: status server already in queue, dropping request");
	    goto errexit;
	}
	i = 0;
    } else {
	if (!to->nextid)
	    to->nextid = start;
	/* might simplify if only try nextid, might be ok */
	for (i = to->nextid; i < MAX_REQUESTS; i++) {
	    if (!to->requests[i].rq) {
		pthread_mutex_lock(to->requests[i].lock);
		if (!to->requests[i].rq)
		    break;
		pthread_mutex_unlock(to->requests[i].lock);
	    }
	}
	if (i == MAX_REQUESTS) {
	    for (i = start; i < to->nextid; i++) {
		if (!to->requests[i].rq) {
		    pthread_mutex_lock(to->requests[i].lock);
		    if (!to->requests[i].rq)
			break;
		    pthread_mutex_unlock(to->requests[i].lock);
		}
	    }
	    if (i == to->nextid) {
		debug(DBG_INFO, "sendrq: no room in queue, dropping request");
		goto errexit;
	    }
	}
    }
    rq->newid = (uint8_t)i;
    rq->msg->id = (uint8_t)i;
    rq->buf = radmsg2buf(rq->msg, (uint8_t *)to->conf->secret);
    if (!rq->buf) {
	pthread_mutex_unlock(to->requests[i].lock);
	debug(DBG_ERR, "sendrq: radmsg2buf failed");
	goto errexit;
    }

    debug(DBG_DBG, "sendrq: inserting packet with id %d in queue for %s", i, to->conf->name);
    to->requests[i].rq = rq;
    pthread_mutex_unlock(to->requests[i].lock);
    if (i >= start) /* i is not reserved for statusserver */
	to->nextid = i + 1;

    if (!to->newrq) {
	to->newrq = 1;
	debug(DBG_DBG, "sendrq: signalling client writer");
	pthread_cond_signal(&to->newrq_cond);
    }

    pthread_mutex_unlock(&to->newrq_mutex);
    removeclientrqs_sendrq_freeserver_lock(0);
    return;

errexit:
    if (rq->from)
	rmclientrq(rq, rq->msg->id);
    freerq(rq);
    pthread_mutex_unlock(&to->newrq_mutex);
    removeclientrqs_sendrq_freeserver_lock(0);
}

void sendreply(struct request *rq) {
    uint8_t first;
    struct client *to = rq->from;

    if (!rq->replybuf)
	rq->replybuf = radmsg2buf(rq->msg, (uint8_t *)to->conf->secret);
    radmsg_free(rq->msg);
    rq->msg = NULL;
    if (!rq->replybuf) {
	freerq(rq);
	debug(DBG_ERR, "sendreply: radmsg2buf failed");
	return;
    }

    pthread_mutex_lock(&to->replyq->mutex);
    first = list_first(to->replyq->entries) == NULL;

    if (!list_push(to->replyq->entries, rq)) {
	pthread_mutex_unlock(&to->replyq->mutex);
	freerq(rq);
	debug(DBG_ERR, "sendreply: malloc failed");
	return;
    }

    if (first) {
	debug(DBG_DBG, "signalling server writer");
	pthread_cond_signal(&to->replyq->cond);
    }
    pthread_mutex_unlock(&to->replyq->mutex);
}

int pwdcrypt(char encrypt_flag, uint8_t *in, uint8_t len, char *shared, uint8_t sharedlen, uint8_t *auth) {
    static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
    static unsigned char first = 1;
    static EVP_MD_CTX mdctx;
    unsigned char hash[EVP_MAX_MD_SIZE], *input;
    unsigned int md_len;
    uint8_t i, offset = 0, out[128];

    pthread_mutex_lock(&lock);
    if (first) {
	EVP_MD_CTX_init(&mdctx);
	first = 0;
    }

    input = auth;
    for (;;) {
	if (!EVP_DigestInit_ex(&mdctx, EVP_md5(), NULL) ||
	    !EVP_DigestUpdate(&mdctx, (uint8_t *)shared, sharedlen) ||
	    !EVP_DigestUpdate(&mdctx, input, 16) ||
	    !EVP_DigestFinal_ex(&mdctx, hash, &md_len) ||
	    md_len != 16) {
	    pthread_mutex_unlock(&lock);
	    return 0;
	}
	for (i = 0; i < 16; i++)
	    out[offset + i] = hash[i] ^ in[offset + i];
	if (encrypt_flag)
	    input = out + offset;
	else
	    input = in + offset;
	offset += 16;
	if (offset == len)
	    break;
    }
    memcpy(in, out, len);
    pthread_mutex_unlock(&lock);
    return 1;
}

int msmppencrypt(uint8_t *text, uint8_t len, uint8_t *shared, uint8_t sharedlen, uint8_t *auth, uint8_t *salt) {
    static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
    static unsigned char first = 1;
    static EVP_MD_CTX mdctx;
    unsigned char hash[EVP_MAX_MD_SIZE];
    unsigned int md_len;
    uint8_t i, offset;

    pthread_mutex_lock(&lock);
    if (first) {
	EVP_MD_CTX_init(&mdctx);
	first = 0;
    }

#if 0
    printfchars(NULL, "msppencrypt auth in", "%02x ", auth, 16);
    printfchars(NULL, "msppencrypt salt in", "%02x ", salt, 2);
    printfchars(NULL, "msppencrypt in", "%02x ", text, len);
#endif

    if (!EVP_DigestInit_ex(&mdctx, EVP_md5(), NULL) ||
	!EVP_DigestUpdate(&mdctx, shared, sharedlen) ||
	!EVP_DigestUpdate(&mdctx, auth, 16) ||
	!EVP_DigestUpdate(&mdctx, salt, 2) ||
	!EVP_DigestFinal_ex(&mdctx, hash, &md_len)) {
	pthread_mutex_unlock(&lock);
	return 0;
    }

#if 0
    printfchars(NULL, "msppencrypt hash", "%02x ", hash, 16);
#endif

    for (i = 0; i < 16; i++)
	text[i] ^= hash[i];

    for (offset = 16; offset < len; offset += 16) {
#if 0
	printf("text + offset - 16 c(%d): ", offset / 16);
	printfchars(NULL, NULL, "%02x ", text + offset - 16, 16);
#endif
	if (!EVP_DigestInit_ex(&mdctx, EVP_md5(), NULL) ||
	    !EVP_DigestUpdate(&mdctx, shared, sharedlen) ||
	    !EVP_DigestUpdate(&mdctx, text + offset - 16, 16) ||
	    !EVP_DigestFinal_ex(&mdctx, hash, &md_len) ||
	    md_len != 16) {
	    pthread_mutex_unlock(&lock);
	    return 0;
	}
#if 0
	printfchars(NULL, "msppencrypt hash", "%02x ", hash, 16);
#endif

	for (i = 0; i < 16; i++)
	    text[offset + i] ^= hash[i];
    }

#if 0
    printfchars(NULL, "msppencrypt out", "%02x ", text, len);
#endif

    pthread_mutex_unlock(&lock);
    return 1;
}

int msmppdecrypt(uint8_t *text, uint8_t len, uint8_t *shared, uint8_t sharedlen, uint8_t *auth, uint8_t *salt) {
    static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
    static unsigned char first = 1;
    static EVP_MD_CTX mdctx;
    unsigned char hash[EVP_MAX_MD_SIZE];
    unsigned int md_len;
    uint8_t i, offset;
    char plain[255];

    pthread_mutex_lock(&lock);
    if (first) {
	EVP_MD_CTX_init(&mdctx);
	first = 0;
    }

#if 0
    printfchars(NULL, "msppdecrypt auth in", "%02x ", auth, 16);
    printfchars(NULL, "msppdecrypt salt in", "%02x ", salt, 2);
    printfchars(NULL, "msppdecrypt in", "%02x ", text, len);
#endif

    if (!EVP_DigestInit_ex(&mdctx, EVP_md5(), NULL) ||
	!EVP_DigestUpdate(&mdctx, shared, sharedlen) ||
	!EVP_DigestUpdate(&mdctx, auth, 16) ||
	!EVP_DigestUpdate(&mdctx, salt, 2) ||
	!EVP_DigestFinal_ex(&mdctx, hash, &md_len)) {
	pthread_mutex_unlock(&lock);
	return 0;
    }

#if 0
    printfchars(NULL, "msppdecrypt hash", "%02x ", hash, 16);
#endif

    for (i = 0; i < 16; i++)
	plain[i] = text[i] ^ hash[i];

    for (offset = 16; offset < len; offset += 16) {
#if 0
	printf("text + offset - 16 c(%d): ", offset / 16);
	printfchars(NULL, NULL, "%02x ", text + offset - 16, 16);
#endif
	if (!EVP_DigestInit_ex(&mdctx, EVP_md5(), NULL) ||
	    !EVP_DigestUpdate(&mdctx, shared, sharedlen) ||
	    !EVP_DigestUpdate(&mdctx, text + offset - 16, 16) ||
	    !EVP_DigestFinal_ex(&mdctx, hash, &md_len) ||
	    md_len != 16) {
	    pthread_mutex_unlock(&lock);
	    return 0;
	}
#if 0
	printfchars(NULL, "msppdecrypt hash", "%02x ", hash, 16);
#endif

	for (i = 0; i < 16; i++)
	    plain[offset + i] = text[offset + i] ^ hash[i];
    }

    memcpy(text, plain, len);
#if 0
    printfchars(NULL, "msppdecrypt out", "%02x ", text, len);
#endif

    pthread_mutex_unlock(&lock);
    return 1;
}

struct realm *newrealmref(struct realm *r) {
    if (r)
	r->refcount++;
    return r;
}

/* returns with lock on realm */
struct realm *id2realm(struct list *realmlist, char *id) {
    struct list_node *entry;
    struct realm *realm, *subrealm;

    /* need to do locking for subrealms and check subrealm timers */
    for (entry = list_first(realmlist); entry; entry = list_next(entry)) {
	realm = (struct realm *)entry->data;
	if (!regexec(&realm->regex, id, 0, NULL, 0)) {
	    pthread_mutex_lock(&realm->mutex);
	    if (realm->subrealms) {
		subrealm = id2realm(realm->subrealms, id);
		if (subrealm) {
		    pthread_mutex_unlock(&realm->mutex);
		    return subrealm;
		}
	    }
	    return newrealmref(realm);
	}
    }
    return NULL;
}

int hasdynamicserver(struct list *srvconfs) {
    struct list_node *entry;

    for (entry = list_first(srvconfs); entry; entry = list_next(entry))
#if defined ENABLE_EXPERIMENTAL_DYNDISC
        if (((struct clsrvconf *)entry->data)->dynamiclookupcommand
            || ((struct clsrvconf *)entry->data)->servers->in_use)
#else
        if (((struct clsrvconf *)entry->data)->dynamiclookupcommand)
#endif
	    return 1;
    return 0;
}

/* helper function, only used by removeserversubrealms() */
void _internal_removeserversubrealms(struct list *realmlist, struct clsrvconf *srv) {
    struct list_node *entry, *entry2;
    struct realm *realm;

    for (entry = list_first(realmlist); entry;) {
	realm = newrealmref((struct realm *)entry->data);
	pthread_mutex_lock(&realm->mutex);
	entry = list_next(entry);

	if (realm->srvconfs) {
	    for (entry2 = list_first(realm->srvconfs); entry2; entry2 = list_next(entry2))
		if (entry2->data == srv)
		    freerealm(realm);
	    list_removedata(realm->srvconfs, srv);
	}
	if (realm->accsrvconfs) {
	    for (entry2 = list_first(realm->accsrvconfs); entry2; entry2 = list_next(entry2))
		if (entry2->data == srv)
		    freerealm(realm);
	    list_removedata(realm->accsrvconfs, srv);
	}

	/* remove subrealm if no dynamic servers left */
	if (!hasdynamicserver(realm->srvconfs) && !hasdynamicserver(realm->accsrvconfs)) {
	    while (list_shift(realm->srvconfs))
		freerealm(realm);
	    list_destroy(realm->srvconfs);
	    realm->srvconfs = NULL;
	    while (list_shift(realm->accsrvconfs))
		freerealm(realm);
	    list_destroy(realm->accsrvconfs);
	    realm->accsrvconfs = NULL;
	    list_removedata(realmlist, realm);
	}
	pthread_mutex_unlock(&realm->mutex);
	freerealm(realm);
    }
}

void removeserversubrealms(struct list *realmlist, struct clsrvconf *srv) {
    struct list_node *entry;
    struct realm *realm;

    for (entry = list_first(realmlist); entry; entry = list_next(entry)) {
	realm = (struct realm *)entry->data;
	pthread_mutex_lock(&realm->mutex);
	if (realm->subrealms) {
	    _internal_removeserversubrealms(realm->subrealms, srv);
	    if (!list_first(realm->subrealms)) {
		list_destroy(realm->subrealms);
		realm->subrealms = NULL;
	    }
	}
	pthread_mutex_unlock(&realm->mutex);
    }
}

int attrvalidate(unsigned char *attrs, int length) {
    while (length > 1) {
	if (ATTRLEN(attrs) < 2) {
	    debug(DBG_INFO, "attrvalidate: invalid attribute length %d", ATTRLEN(attrs));
	    return 0;
	}
	length -= ATTRLEN(attrs);
	if (length < 0) {
	    debug(DBG_INFO, "attrvalidate: attribute length %d exceeds packet length", ATTRLEN(attrs));
	    return 0;
	}
	attrs += ATTRLEN(attrs);
    }
    if (length)
	debug(DBG_INFO, "attrvalidate: malformed packet? remaining byte after last attribute");
    return 1;
}

int pwdrecrypt(uint8_t *pwd, uint8_t len, char *oldsecret, char *newsecret, uint8_t *oldauth, uint8_t *newauth) {
    if (len < 16 || len > 128 || len % 16) {
	debug(DBG_WARN, "pwdrecrypt: invalid password length");
	return 0;
    }

    if (!pwdcrypt(0, pwd, len, oldsecret, strlen(oldsecret), oldauth)) {
	debug(DBG_WARN, "pwdrecrypt: cannot decrypt password");
	return 0;
    }
#ifdef DEBUG
    printfchars(NULL, "pwdrecrypt: password", "%02x ", pwd, len);
#endif
    if (!pwdcrypt(1, pwd, len, newsecret, strlen(newsecret), newauth)) {
	debug(DBG_WARN, "pwdrecrypt: cannot encrypt password");
	return 0;
    }
    return 1;
}

int msmpprecrypt(uint8_t *msmpp, uint8_t len, char *oldsecret, char *newsecret, uint8_t *oldauth, uint8_t *newauth) {
    if (len < 18)
	return 0;
    if (!msmppdecrypt(msmpp + 2, len - 2, (uint8_t *)oldsecret, strlen(oldsecret), oldauth, msmpp)) {
	debug(DBG_WARN, "msmpprecrypt: failed to decrypt msppe key");
	return 0;
    }
    if (!msmppencrypt(msmpp + 2, len - 2, (uint8_t *)newsecret, strlen(newsecret), newauth, msmpp)) {
	debug(DBG_WARN, "msmpprecrypt: failed to encrypt msppe key");
	return 0;
    }
    return 1;
}

int msmppe(unsigned char *attrs, int length, uint8_t type, char *attrtxt, struct request *rq,
	   char *oldsecret, char *newsecret) {
    unsigned char *attr;

    for (attr = attrs; (attr = attrget(attr, length - (attr - attrs), type)); attr += ATTRLEN(attr)) {
	debug(DBG_DBG, "msmppe: Got %s", attrtxt);
	if (!msmpprecrypt(ATTRVAL(attr), ATTRVALLEN(attr), oldsecret, newsecret, rq->buf + 4, rq->rqauth))
	    return 0;
    }
    return 1;
}

int findvendorsubattr(uint32_t *attrs, uint32_t vendor, uint32_t subattr) {
    if (!attrs)
	return 0;

    for (; attrs[0]; attrs += 2)
	if (attrs[0] == vendor && attrs[1] == subattr)
	    return 1;
    return 0;
}

/* returns 1 if entire element is to be removed, else 0 */
int dovendorrewriterm(struct tlv *attr, uint32_t *removevendorattrs) {
    uint8_t alen, sublen;
    uint32_t vendor;
    uint8_t *subattrs;

    if (!removevendorattrs)
	return 0;

    memcpy(&vendor, attr->v, 4);
    vendor = ntohl(vendor);
    while (*removevendorattrs && *removevendorattrs != vendor)
	removevendorattrs += 2;
    if (!*removevendorattrs)
	return 0;

    if (findvendorsubattr(removevendorattrs, vendor, 256))
	return 1; /* remove entire vendor attribute */

    sublen = attr->l - 4;
    subattrs = attr->v + 4;