radsecproxy.c

/*
 * Copyright (C) 2006-2008 Stig Venaas <venaas@uninett.no>
 *
 * 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.
 */

/* 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 peer and 30 TLS peers, there will be a max of
 *          1 + (2 + 2 * 3) + (2 * 30) + (2 * 30) = 129 threads
*/

#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 <sys/select.h>
#include <ctype.h>
#include <sys/wait.h>
#include <arpa/inet.h>
#include <regex.h>
#include <libgen.h>
#include <pthread.h>
#include <openssl/ssl.h>
#include <openssl/rand.h>
#include <openssl/err.h>
#include <openssl/md5.h>
#include <openssl/hmac.h>
#include <openssl/x509v3.h>
#include "debug.h"
#include "list.h"
#include "util.h"
#include "gconfig.h"
#include "radsecproxy.h"

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

static struct addrinfo *srcudpres = NULL;
static struct addrinfo *srctcpres = NULL;

static struct replyq *udp_server_replyq = NULL;
static int udp_client4_sock = -1;
static int udp_client6_sock = -1;
static pthread_mutex_t *ssl_locks;
static long *ssl_lock_count;
extern int optind;
extern char *optarg;

/* minimum required declarations to avoid reordering code */
void adddynamicrealmserver(struct realm *realm, struct clsrvconf *conf, 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 freerqdata(struct request *rq);
void *udpserverrd(void *arg);
void *tlslistener(void *arg);
void *tcplistener(void *arg);

static const struct protodefs protodefs[] = {
    {   "udp", /* UDP, assuming RAD_UDP defined as 0 */
	NULL, /* secretdefault */
	SOCK_DGRAM, /* socktype */
	"1812", /* portdefault */
	REQUEST_RETRY_COUNT, /* retrycountdefault */
	10, /* retrycountmax */
	REQUEST_RETRY_INTERVAL, /* retryintervaldefault */
	60, /* retryintervalmax */
	udpserverrd
    },
    {   "tls", /* TLS, assuming RAD_TLS defined as 1 */
	"mysecret", /* secretdefault */
	SOCK_STREAM, /* socktype */
	"2083", /* portdefault */
	0, /* retrycountdefault */
	0, /* retrycountmax */
	REQUEST_RETRY_INTERVAL * REQUEST_RETRY_COUNT, /* retryintervaldefault */
	60, /* retryintervalmax */
	tlslistener
    },
    {   "tcp", /* TCP, assuming RAD_TCP defined as 2 */
	NULL, /* secretdefault */
	SOCK_STREAM, /* socktype */
	"1812", /* portdefault */
	0, /* retrycountdefault */
	0, /* retrycountmax */
	REQUEST_RETRY_INTERVAL * REQUEST_RETRY_COUNT, /* retryintervaldefault */
	60, /* retryintervalmax */
	tcplistener
    },
    {   NULL
    }
};

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

    for (i = 0; protodefs[i].name && strcasecmp(protodefs[i].name, name); i++);
    return i;
}
    
/* 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]);
}

static int pem_passwd_cb(char *buf, int size, int rwflag, void *userdata) {
    int pwdlen = strlen(userdata);
    if (rwflag != 0 || pwdlen > size) /* not for decryption or too large */
	return 0;
    memcpy(buf, userdata, pwdlen);
    return pwdlen;
}

static int verify_cb(int ok, X509_STORE_CTX *ctx) {
  char buf[256];
  X509 *err_cert;
  int err, depth;

  err_cert = X509_STORE_CTX_get_current_cert(ctx);
  err = X509_STORE_CTX_get_error(ctx);
  depth = X509_STORE_CTX_get_error_depth(ctx);

  if (depth > MAX_CERT_DEPTH) {
      ok = 0;
      err = X509_V_ERR_CERT_CHAIN_TOO_LONG;
      X509_STORE_CTX_set_error(ctx, err);
  }

  if (!ok) {
      X509_NAME_oneline(X509_get_subject_name(err_cert), buf, 256);
      debug(DBG_WARN, "verify error: num=%d:%s:depth=%d:%s", err, X509_verify_cert_error_string(err), depth, buf);

      switch (err) {
      case X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT:
	  X509_NAME_oneline(X509_get_issuer_name(ctx->current_cert), buf, 256);
	  debug(DBG_WARN, "\tIssuer=%s", buf);
	  break;
      case X509_V_ERR_CERT_NOT_YET_VALID:
      case X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD:
	  debug(DBG_WARN, "\tCertificate not yet valid");
	  break;
      case X509_V_ERR_CERT_HAS_EXPIRED:
	  debug(DBG_WARN, "Certificate has expired");
	  break;
      case X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD:
	  debug(DBG_WARN, "Certificate no longer valid (after notAfter)");
	  break;
      }
  }
#ifdef DEBUG  
  printf("certificate verify returns %d\n", ok);
#endif  
  return ok;
}

int resolvepeer(struct clsrvconf *conf, int ai_flags) {
    struct addrinfo hints, *addrinfo, *res;
    char *slash, *s;
    int plen;

    slash = conf->host ? strchr(conf->host, '/') : NULL;
    if (slash) {
	s = slash + 1;
	if (!*s) {
	    debug(DBG_WARN, "resolvepeer: prefix length must be specified after the / in %s", conf->host);
	    return 0;
	}
	for (; *s; s++)
	    if (*s < '0' || *s > '9') {
		debug(DBG_WARN, "resolvepeer: %s in %s is not a valid prefix length", slash + 1, conf->host);
		return 0;
	    }
	plen = atoi(slash + 1);
	if (plen < 0 || plen > 128) {
	    debug(DBG_WARN, "resolvepeer: %s in %s is not a valid prefix length", slash + 1, conf->host);
	    return 0;
	}
	*slash = '\0';
    }
    memset(&hints, 0, sizeof(hints));
    hints.ai_socktype = conf->pdef->socktype;
    hints.ai_family = AF_UNSPEC;
    hints.ai_flags = ai_flags;
    if (!conf->host && !conf->port) {
	/* getaddrinfo() doesn't like host and port to be NULL */
	if (getaddrinfo(conf->host, conf->pdef->portdefault, &hints, &addrinfo)) {
	    debug(DBG_WARN, "resolvepeer: can't resolve (null) port (null)");
	    return 0;
	}
	for (res = addrinfo; res; res = res->ai_next) {
	    switch (res->ai_family) {
	    case AF_INET:
		((struct sockaddr_in *)res->ai_addr)->sin_port = 0;
		break;
	    case AF_INET6:
		((struct sockaddr_in6 *)res->ai_addr)->sin6_port = 0;
		break;
	    }
	}
    } else {
	if (slash)
	    hints.ai_flags |= AI_NUMERICHOST;
	if (getaddrinfo(conf->host, conf->port, &hints, &addrinfo)) {
	    debug(DBG_WARN, "resolvepeer: can't resolve %s port %s", conf->host ? conf->host : "(null)", conf->port ? conf->port : "(null)");
	    return 0;
	}
	if (slash) {
	    *slash = '/';
	    switch (addrinfo->ai_family) {
	    case AF_INET:
		if (plen > 32) {
		    debug(DBG_WARN, "resolvepeer: prefix length must be <= 32 in %s", conf->host);
		    freeaddrinfo(addrinfo);
		    return 0;
		}
		break;
	    case AF_INET6:
		break;
	    default:
		debug(DBG_WARN, "resolvepeer: prefix must be IPv4 or IPv6 in %s", conf->host);
		freeaddrinfo(addrinfo);
		return 0;
	    }
	    conf->prefixlen = plen;
	} else
	    conf->prefixlen = 255;
    }
    if (conf->addrinfo)
	freeaddrinfo(conf->addrinfo);
    conf->addrinfo = addrinfo;
    return 1;
}	  

int bindtoaddr(struct addrinfo *addrinfo, int family, int reuse, int v6only) {
    int s, on = 1;
    struct addrinfo *res;
    
    for (res = addrinfo; res; res = res->ai_next) {
	if (family != AF_UNSPEC && family != res->ai_family)
	    continue;
        s = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
        if (s < 0) {
            debug(DBG_WARN, "bindtoaddr: socket failed");
            continue;
        }
	if (reuse)
	    setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
#ifdef IPV6_V6ONLY
	if (v6only)
	    setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, &on, sizeof(on));
#endif		

	if (!bind(s, res->ai_addr, res->ai_addrlen))
	    return s;
	debug(DBG_WARN, "bindtoaddr: bind failed");
        close(s);
    }
    return -1;
}	  

char *parsehostport(char *s, struct clsrvconf *conf, char *default_port) {
    char *p, *field;
    int ipv6 = 0;

    p = s;
    /* allow literal addresses and port, e.g. [2001:db8::1]:1812 */
    if (*p == '[') {
	p++;
	field = p;
	for (; *p && *p != ']' && *p != ' ' && *p != '\t' && *p != '\n'; p++);
	if (*p != ']')
	    debugx(1, DBG_ERR, "no ] matching initial [");
	ipv6 = 1;
    } else {
	field = p;
	for (; *p && *p != ':' && *p != ' ' && *p != '\t' && *p != '\n'; p++);
    }
    if (field == p)
	debugx(1, DBG_ERR, "missing host/address");

    conf->host = stringcopy(field, p - field);
    if (ipv6) {
	p++;
	if (*p && *p != ':' && *p != ' ' && *p != '\t' && *p != '\n')
	    debugx(1, DBG_ERR, "unexpected character after ]");
    }
    if (*p == ':') {
	    /* port number or service name is specified */;
	    field = ++p;
	    for (; *p && *p != ' ' && *p != '\t' && *p != '\n'; p++);
	    if (field == p)
		debugx(1, DBG_ERR, "syntax error, : but no following port");
	    conf->port = stringcopy(field, p - field);
    } else
	conf->port = default_port ? stringcopy(default_port, 0) : NULL;
    return p;
}

struct clsrvconf *resolve_hostport(uint8_t type, char *lconf, char *default_port) {
    struct clsrvconf *conf;

    conf = malloc(sizeof(struct clsrvconf));
    if (!conf)
	debugx(1, DBG_ERR, "malloc failed");
    memset(conf, 0, sizeof(struct clsrvconf));
    conf->type = type;
    conf->pdef = &protodefs[conf->type];
    if (lconf) {
	parsehostport(lconf, conf, default_port);
	if (!strcmp(conf->host, "*")) {
	    free(conf->host);
	    conf->host = NULL;
	}
    } else
	conf->port = default_port ? stringcopy(default_port, 0) : NULL;
    if (!resolvepeer(conf, AI_PASSIVE))
	debugx(1, DBG_ERR, "failed to resolve host %s port %s, exiting", conf->host ? conf->host : "(null)", conf->port ? conf->port : "(null)");
    return conf;
}

void freeclsrvres(struct clsrvconf *res) {
    free(res->host);
    free(res->port);
    if (res->addrinfo)
	freeaddrinfo(res->addrinfo);
    free(res);
}

int connecttcp(struct addrinfo *addrinfo) {
    int s;
    struct addrinfo *res;

    s = -1;
    for (res = addrinfo; res; res = res->ai_next) {
	s = bindtoaddr(srctcpres, res->ai_family, 1, 1);
        if (s < 0) {
            debug(DBG_WARN, "connecttoserver: socket failed");
            continue;
        }
        if (connect(s, res->ai_addr, res->ai_addrlen) == 0)
            break;
        debug(DBG_WARN, "connecttoserver: connect failed");
        close(s);
        s = -1;
    }
    return s;
}	  

/* 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 };
    int 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]);
}

/* check if conf has matching address */
struct clsrvconf *checkconfaddr(uint8_t type, struct sockaddr *addr, struct clsrvconf *conf) {
    struct sockaddr_in6 *sa6 = NULL;
    struct in_addr *a4 = NULL;
    struct addrinfo *res;
    
    if (addr->sa_family == AF_INET6) {
        sa6 = (struct sockaddr_in6 *)addr;
        if (IN6_IS_ADDR_V4MAPPED(&sa6->sin6_addr)) {
            a4 = (struct in_addr *)&sa6->sin6_addr.s6_addr[12];
	    sa6 = NULL;
	}
    } else
	a4 = &((struct sockaddr_in *)addr)->sin_addr;

    if (conf->type == type) {
	if (conf->prefixlen == 255) {
	    for (res = conf->addrinfo; res; res = res->ai_next)
		if ((a4 && res->ai_family == AF_INET &&
		     !memcmp(a4, &((struct sockaddr_in *)res->ai_addr)->sin_addr, 4)) ||
		    (sa6 && res->ai_family == AF_INET6 &&
		     !memcmp(&sa6->sin6_addr, &((struct sockaddr_in6 *)res->ai_addr)->sin6_addr, 16)))
		    return conf;
	} else {
	    res = conf->addrinfo;
	    if (res &&
		((a4 && res->ai_family == AF_INET &&
		  prefixmatch(a4, &((struct sockaddr_in *)res->ai_addr)->sin_addr, conf->prefixlen)) ||
		 (sa6 && res->ai_family == AF_INET6 &&
		  prefixmatch(&sa6->sin6_addr, &((struct sockaddr_in6 *)res->ai_addr)->sin6_addr, conf->prefixlen))))
		return conf;
	}
    }
    return NULL;
}

/* 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) {
    struct sockaddr_in6 *sa6 = NULL;
    struct in_addr *a4 = NULL;
    struct addrinfo *res;
    struct list_node *entry;
    struct clsrvconf *conf;
    
    if (addr->sa_family == AF_INET6) {
        sa6 = (struct sockaddr_in6 *)addr;
        if (IN6_IS_ADDR_V4MAPPED(&sa6->sin6_addr)) {
            a4 = (struct in_addr *)&sa6->sin6_addr.s6_addr[12];
	    sa6 = NULL;
	}
    } else
	a4 = &((struct sockaddr_in *)addr)->sin_addr;

    for (entry = (cur && *cur ? list_next(*cur) : list_first(confs)); entry; entry = list_next(entry)) {
	conf = (struct clsrvconf *)entry->data;
	if (conf->type == type) {
	    if (conf->prefixlen == 255) {
		for (res = conf->addrinfo; res; res = res->ai_next)
		    if ((a4 && res->ai_family == AF_INET &&
			 !memcmp(a4, &((struct sockaddr_in *)res->ai_addr)->sin_addr, 4)) ||
			(sa6 && res->ai_family == AF_INET6 &&
			 !memcmp(&sa6->sin6_addr, &((struct sockaddr_in6 *)res->ai_addr)->sin6_addr, 16))) {
			if (cur)
			    *cur = entry;
			return conf;
		    }
	    } else {
		res = conf->addrinfo;
		if (res &&
		    ((a4 && res->ai_family == AF_INET &&
		      prefixmatch(a4, &((struct sockaddr_in *)res->ai_addr)->sin_addr, conf->prefixlen)) ||
		     (sa6 && res->ai_family == AF_INET6 &&
		      prefixmatch(&sa6->sin6_addr, &((struct sockaddr_in6 *)res->ai_addr)->sin6_addr, conf->prefixlen)))) {
		    if (cur)
			*cur = entry;
		    return conf;
		}
	    }
	}
    }    
    return NULL;
}

/* returns next config of given type, or NULL */
struct clsrvconf *find_conf_type(uint8_t type, struct list *confs, struct list_node **cur) {
    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) {
	    if (cur)
		*cur = entry;
	    return conf;
	}
    }    
    return NULL;
}

struct replyq *newreplyq() {
    struct replyq *replyq;
    
    replyq = malloc(sizeof(struct replyq));
    if (!replyq)
	debugx(1, DBG_ERR, "malloc failed");
    replyq->replies = list_create();
    if (!replyq->replies)
	debugx(1, DBG_ERR, "malloc failed");
    pthread_mutex_init(&replyq->mutex, NULL);
    pthread_cond_init(&replyq->cond, NULL);
    return replyq;
}

struct client *addclient(struct clsrvconf *conf) {
    struct client *new = malloc(sizeof(struct client));
    
    if (!new) {
	debug(DBG_ERR, "malloc failed");
	return NULL;
    }
    if (!conf->clients) {
	conf->clients = list_create();
	if (!conf->clients) {
	    debug(DBG_ERR, "malloc failed");
	    return NULL;
	}
    }
    
    memset(new, 0, sizeof(struct client));
    new->conf = conf;
    new->replyq = conf->type == RAD_UDP ? udp_server_replyq : newreplyq();

    list_push(conf->clients, new);
    return new;
}

void removeclient(struct client *client) {
    struct list_node *entry;
    
    if (!client || !client->conf->clients)
	return;

    pthread_mutex_lock(&client->replyq->mutex);
    for (entry = list_first(client->replyq->replies); entry; entry = list_next(entry))
	free(((struct reply *)entry)->buf);
    list_destroy(client->replyq->replies);
    pthread_cond_destroy(&client->replyq->cond);
    pthread_mutex_unlock(&client->replyq->mutex);
    pthread_mutex_destroy(&client->replyq->mutex);
    list_removedata(client->conf->clients, client);
    free(client);
}

void removeclientrqs(struct client *client) {
    struct list_node *entry;
    struct server *server;
    struct request *rq;
    int i;
    
    for (entry = list_first(srvconfs); entry; entry = list_next(entry)) {
	server = ((struct clsrvconf *)entry->data)->servers;
	if (!server)
	    continue;
	pthread_mutex_lock(&server->newrq_mutex);
	for (i = 0; i < MAX_REQUESTS; i++) {
	    rq = server->requests + i;
	    if (rq->from == client)
		rq->from = NULL;
	}
	pthread_mutex_unlock(&server->newrq_mutex);
    }
}

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

    if (!server)
	return;

    if(server->requests) {
	rq = server->requests;
	for (end = rq + MAX_REQUESTS; rq < end; rq++)
	    freerqdata(rq);
	free(server->requests);
    }
    free(server->dynamiclookuparg);
    if (destroymutex) {
	pthread_mutex_destroy(&server->lock);
	pthread_cond_destroy(&server->newrq_cond);
	pthread_mutex_destroy(&server->newrq_mutex);
    }
    free(server);
}

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

    if (conf->type == RAD_UDP) {
	if (!srcudpres) {
	    res = resolve_hostport(RAD_UDP, options.sourceudp, NULL);
	    srcudpres = res->addrinfo;
	    res->addrinfo = NULL;
	    freeclsrvres(res);
	}
	switch (conf->addrinfo->ai_family) {
	case AF_INET:
	    if (udp_client4_sock < 0) {
		udp_client4_sock = bindtoaddr(srcudpres, AF_INET, 0, 1);
		if (udp_client4_sock < 0)
		    debugx(1, DBG_ERR, "addserver: failed to create client socket for server %s", conf->host);
	    }
	    conf->servers->sock = udp_client4_sock;
	    break;
	case AF_INET6:
	    if (udp_client6_sock < 0) {
		udp_client6_sock = bindtoaddr(srcudpres, AF_INET6, 0, 1);
		if (udp_client6_sock < 0)
		    debugx(1, DBG_ERR, "addserver: failed to create client socket for server %s", conf->host);
	    }
	    conf->servers->sock = udp_client6_sock;
	    break;
	default:
	    debugx(1, DBG_ERR, "addserver: unsupported address family");
	}
	
    } else {
	if (!srctcpres) {
	    res = resolve_hostport(RAD_TLS, options.sourcetcp, NULL);
	    srctcpres = res->addrinfo;
	    res->addrinfo = NULL;
	    freeclsrvres(res);
	}
	conf->servers->sock = -1;
    }
    
    conf->servers->requests = calloc(MAX_REQUESTS, sizeof(struct request));
    if (!conf->servers->requests) {
	debug(DBG_ERR, "malloc failed");
	goto errexit;
    }
    if (pthread_mutex_init(&conf->servers->lock, NULL)) {
	debug(DBG_ERR, "mutex init failed");
	goto errexit;
    }
    conf->servers->newrq = 0;
    if (pthread_mutex_init(&conf->servers->newrq_mutex, NULL)) {
	debug(DBG_ERR, "mutex init failed");
	pthread_mutex_destroy(&conf->servers->lock);
	goto errexit;
    }
    if (pthread_cond_init(&conf->servers->newrq_cond, NULL)) {
	debug(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;
}

/* exactly one of client and server must be non-NULL */
/* should probably take peer list (client(s) or server(s)) as argument instead */
/* if *peer == NULL we return who we received from, else require it to be from peer */
/* return from in sa if not NULL */
unsigned char *radudpget(int s, struct client **client, struct server **server, struct sockaddr_storage *sa) {
    int cnt, len;
    unsigned char buf[65536], *rad;
    struct sockaddr_storage from;
    socklen_t fromlen = sizeof(from);
    struct clsrvconf *p;
    struct list_node *node;
    
    for (;;) {
	cnt = recvfrom(s, buf, sizeof(buf), 0, (struct sockaddr *)&from, &fromlen);
	if (cnt == -1) {
	    debug(DBG_WARN, "radudpget: recv failed");
	    continue;
	}
	debug(DBG_DBG, "radudpget: got %d bytes from %s", cnt, addr2string((struct sockaddr *)&from, fromlen));

	if (cnt < 20) {
	    debug(DBG_WARN, "radudpget: packet too small");
	    continue;
	}
    
	len = RADLEN(buf);
	if (len < 20) {
	    debug(DBG_WARN, "radudpget: length too small");
	    continue;
	}

	if (cnt < len) {
	    debug(DBG_WARN, "radudpget: packet smaller than length field in radius header");
	    continue;
	}
	if (cnt > len)
	    debug(DBG_DBG, "radudpget: packet was padded with %d bytes", cnt - len);

	if (client)
	    if (*client)
		p = checkconfaddr(RAD_UDP, (struct sockaddr *)&from, (*client)->conf);
	    else
		p = find_conf(RAD_UDP, (struct sockaddr *)&from, clconfs, NULL);
	else
	    if (*server)
		p = checkconfaddr(RAD_UDP, (struct sockaddr *)&from, (*server)->conf);
	    else
		p = find_conf(RAD_UDP, (struct sockaddr *)&from, srvconfs, NULL);

	if (!p) {
	    debug(DBG_WARN, "radudpget: got packet from wrong or unknown UDP peer %s, ignoring", addr2string((struct sockaddr *)&from, fromlen));
	    continue;
	}
	
	rad = malloc(len);
	if (!rad) {
	    debug(DBG_ERR, "radudpget: malloc failed");
	    continue;
	}
	
	if (client && !*client) {
	    node = list_first(p->clients);
	    *client = node ? (struct client *)node->data : addclient(p);
	    if (!*client) {
		free(rad);
		continue;
	    }
	} else if (server && !*server)
	    *server = p->servers;
	
	break;
    }
    memcpy(rad, buf, len);
    if (sa)
	*sa = from;
    return rad;
}

int subjectaltnameaddr(X509 *cert, int family, struct in6_addr *addr) {
    int loc, i, l, n, r = 0;
    char *v;
    X509_EXTENSION *ex;
    STACK_OF(GENERAL_NAME) *alt;
    GENERAL_NAME *gn;
    
    debug(DBG_DBG, "subjectaltnameaddr");
    
    loc = X509_get_ext_by_NID(cert, NID_subject_alt_name, -1);
    if (loc < 0)
	return r;
    
    ex = X509_get_ext(cert, loc);
    alt = X509V3_EXT_d2i(ex);
    if (!alt)
	return r;
    
    n = sk_GENERAL_NAME_num(alt);
    for (i = 0; i < n; i++) {
	gn = sk_GENERAL_NAME_value(alt, i);
	if (gn->type != GEN_IPADD)
	    continue;
	r = -1;
	v = (char *)ASN1_STRING_data(gn->d.ia5);
	l = ASN1_STRING_length(gn->d.ia5);
	if (((family == AF_INET && l == sizeof(struct in_addr)) || (family == AF_INET6 && l == sizeof(struct in6_addr)))
	    && !memcmp(v, &addr, l)) {
	    r = 1;
	    break;
	}
    }
    GENERAL_NAMES_free(alt);
    return r;
}

int cnregexp(X509 *cert, char *exact, regex_t *regex) {
    int loc, l;
    char *v, *s;
    X509_NAME *nm;
    X509_NAME_ENTRY *e;
    ASN1_STRING *t;

    nm = X509_get_subject_name(cert);
    loc = -1;
    for (;;) {
	loc = X509_NAME_get_index_by_NID(nm, NID_commonName, loc);
	if (loc == -1)
	    break;
	e = X509_NAME_get_entry(nm, loc);
	t = X509_NAME_ENTRY_get_data(e);
	v = (char *) ASN1_STRING_data(t);
	l = ASN1_STRING_length(t);
	if (l < 0)
	    continue;
	if (exact) {
	    if (l == strlen(exact) && !strncasecmp(exact, v, l))
		return 1;
	} else {
	    s = stringcopy((char *)v, l);
	    if (!s) {
		debug(DBG_ERR, "malloc failed");
		continue;
	    }
	    if (regexec(regex, s, 0, NULL, 0)) {
		free(s);
		continue;
	    }
	    free(s);
	    return 1;
	}
    }
    return 0;
}

int subjectaltnameregexp(X509 *cert, int type, char *exact,  regex_t *regex) {
    int loc, i, l, n, r = 0;
    char *s, *v;
    X509_EXTENSION *ex;
    STACK_OF(GENERAL_NAME) *alt;
    GENERAL_NAME *gn;
    
    debug(DBG_DBG, "subjectaltnameregexp");
    
    loc = X509_get_ext_by_NID(cert, NID_subject_alt_name, -1);
    if (loc < 0)
	return r;
    
    ex = X509_get_ext(cert, loc);
    alt = X509V3_EXT_d2i(ex);
    if (!alt)
	return r;
    
    n = sk_GENERAL_NAME_num(alt);
    for (i = 0; i < n; i++) {
	gn = sk_GENERAL_NAME_value(alt, i);
	if (gn->type != type)
	    continue;
	r = -1;
	v = (char *)ASN1_STRING_data(gn->d.ia5);
	l = ASN1_STRING_length(gn->d.ia5);
	if (l <= 0)
	    continue;
#ifdef DEBUG
	printfchars(NULL, gn->type == GEN_DNS ? "dns" : "uri", NULL, v, l);
#endif	
	if (exact) {
	    if (memcmp(v, exact, l))
		continue;
	} else {
	    s = stringcopy((char *)v, l);
	    if (!s) {
		debug(DBG_ERR, "malloc failed");
		continue;
	    }
	    if (regexec(regex, s, 0, NULL, 0)) {
		free(s);
		continue;
	    }
	    free(s);
	}
	r = 1;
	break;
    }
    GENERAL_NAMES_free(alt);
    return r;
}

X509 *verifytlscert(SSL *ssl) {
    X509 *cert;
    unsigned long error;
    
    if (SSL_get_verify_result(ssl) != X509_V_OK) {
	debug(DBG_ERR, "verifytlscert: basic validation failed");
	while ((error = ERR_get_error()))
	    debug(DBG_ERR, "verifytlscert: TLS: %s", ERR_error_string(error, NULL));
	return NULL;
    }

    cert = SSL_get_peer_certificate(ssl);
    if (!cert)
	debug(DBG_ERR, "verifytlscert: failed to obtain certificate");
    return cert;
}
    
int verifyconfcert(X509 *cert, struct clsrvconf *conf) {
    int r;
    uint8_t type = 0; /* 0 for DNS, AF_INET for IPv4, AF_INET6 for IPv6 */
    struct in6_addr addr;
    
    if (conf->certnamecheck && conf->prefixlen == 255) {
	if (inet_pton(AF_INET, conf->host, &addr))
	    type = AF_INET;
	else if (inet_pton(AF_INET6, conf->host, &addr))
	    type = AF_INET6;

	r = type ? subjectaltnameaddr(cert, type, &addr) : subjectaltnameregexp(cert, GEN_DNS, conf->host, NULL);
	if (r) {
	    if (r < 0) {
		debug(DBG_WARN, "verifyconfcert: No subjectaltname matching %s %s", type ? "address" : "host", conf->host);
		return 0;
	    }
	    debug(DBG_DBG, "verifyconfcert: Found subjectaltname matching %s %s", type ? "address" : "host", conf->host);
	} else {
	    if (!cnregexp(cert, conf->host, NULL)) {
		debug(DBG_WARN, "verifyconfcert: cn not matching host %s", conf->host);
		return 0;
	    }		
	    debug(DBG_DBG, "verifyconfcert: Found cn matching host %s", conf->host);
	}
    }
    if (conf->certcnregex) {
	if (cnregexp(cert, NULL, conf->certcnregex) < 1) {
	    debug(DBG_WARN, "verifyconfcert: CN not matching regex");
	    return 0;
	}
	debug(DBG_DBG, "verifyconfcert: CN matching regex");
    }
    if (conf->certuriregex) {
	if (subjectaltnameregexp(cert, GEN_URI, NULL, conf->certuriregex) < 1) {
	    debug(DBG_WARN, "verifyconfcert: subjectaltname URI not matching regex");
	    return 0;
	}
	debug(DBG_DBG, "verifyconfcert: subjectaltname URI matching regex");
    }
    return 1;
}

int tlsconnect(struct server *server, struct timeval *when, int timeout, char *text) {
    struct timeval now;
    time_t elapsed;
    X509 *cert;
    
    debug(DBG_DBG, "tlsconnect called from %s", text);
    pthread_mutex_lock(&server->lock);
    if (when && memcmp(&server->lastconnecttry, when, sizeof(struct timeval))) {
	/* already reconnected, nothing to do */
	debug(DBG_DBG, "tlsconnect(%s): seems already reconnected", text);
	pthread_mutex_unlock(&server->lock);
	return 1;
    }

    debug(DBG_DBG, "tlsconnect %s", text);

    for (;;) {
	gettimeofday(&now, NULL);
	elapsed = now.tv_sec - server->lastconnecttry.tv_sec;
	if (timeout && server->lastconnecttry.tv_sec && elapsed > timeout) {
	    debug(DBG_DBG, "tlsconnect: timeout");
	    if (server->sock >= 0)
		close(server->sock);
	    SSL_free(server->ssl);
	    server->ssl = NULL;
	    pthread_mutex_unlock(&server->lock);
	    return 0;
	}
	if (server->connectionok) {
	    server->connectionok = 0;
	    sleep(2);
	} else if (elapsed < 1)
	    sleep(2);
	else if (elapsed < 60) {
	    debug(DBG_INFO, "tlsconnect: sleeping %lds", elapsed);
	    sleep(elapsed);
	} else if (elapsed < 100000) {
	    debug(DBG_INFO, "tlsconnect: sleeping %ds", 60);
	    sleep(60);
	} else
	    server->lastconnecttry.tv_sec = now.tv_sec;  /* no sleep at startup */
	debug(DBG_WARN, "tlsconnect: trying to open TLS connection to %s port %s", server->conf->host, server->conf->port);
	if (server->sock >= 0)
	    close(server->sock);
	if ((server->sock = connecttcp(server->conf->addrinfo)) < 0) {
	    debug(DBG_ERR, "tlsconnect: connecttcp failed");
	    continue;
	}
	
	SSL_free(server->ssl);
	server->ssl = SSL_new(server->conf->ssl_ctx);
	SSL_set_fd(server->ssl, server->sock);
	if (SSL_connect(server->ssl) <= 0)
	    continue;
	cert = verifytlscert(server->ssl);
	if (!cert)
	    continue;
	if (verifyconfcert(cert, server->conf)) {
	    X509_free(cert);
	    break;