xref: /src/lib/libc/rpc/rpc_generic.c

/*	$NetBSD: rpc_generic.c,v 1.14 2003/09/09 00:22:17 itojun Exp $	*/

/*
 * Sun RPC is a product of Sun Microsystems, Inc. and is provided for
 * unrestricted use provided that this legend is included on all tape
 * media and as a part of the software program in whole or part.  Users
 * may copy or modify Sun RPC without charge, but are not authorized
 * to license or distribute it to anyone else except as part of a product or
 * program developed by the user.
 *
 * SUN RPC IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING THE
 * WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
 *
 * Sun RPC is provided with no support and without any obligation on the
 * part of Sun Microsystems, Inc. to assist in its use, correction,
 * modification or enhancement.
 *
 * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
 * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY SUN RPC
 * OR ANY PART THEREOF.
 *
 * In no event will Sun Microsystems, Inc. be liable for any lost revenue
 * or profits or other special, indirect and consequential damages, even if
 * Sun has been advised of the possibility of such damages.
 *
 * Sun Microsystems, Inc.
 * 2550 Garcia Avenue
 * Mountain View, California  94043
 */
/*
 * Copyright (c) 1986-1991 by Sun Microsystems Inc.
 */

/* #pragma ident	"@(#)rpc_generic.c	1.17	94/04/24 SMI" */

/*
 * rpc_generic.c, Miscl routines for RPC.
 *
 */

#include "namespace.h"
#include "reentrant.h"
#include <sys/types.h>
#include <sys/param.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/resource.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <rpc/rpc.h>
#include <assert.h>
#include <ctype.h>
#include <stdio.h>
#include <netdb.h>
#include <netconfig.h>
#include <malloc.h>
#include <string.h>
#include <syslog.h>
#include <rpc/nettype.h>
#include "rpc_internal.h"

struct handle {
	NCONF_HANDLE *nhandle;
	int nflag;		/* Whether NETPATH or NETCONFIG */
	int nettype;
};

static const struct _rpcnettype {
	const char *name;
	const int type;
} _rpctypelist[] = {
	{ "netpath", _RPC_NETPATH },
	{ "visible", _RPC_VISIBLE },
	{ "circuit_v", _RPC_CIRCUIT_V },
	{ "datagram_v", _RPC_DATAGRAM_V },
	{ "circuit_n", _RPC_CIRCUIT_N },
	{ "datagram_n", _RPC_DATAGRAM_N },
	{ "tcp", _RPC_TCP },
	{ "udp", _RPC_UDP },
	{ 0, _RPC_NONE }
};

struct netid_af {
	const char	*netid;
	int		af;
	int		protocol;
};

static const struct netid_af na_cvt[] = {
	{ "udp",  AF_INET,  IPPROTO_UDP },
	{ "tcp",  AF_INET,  IPPROTO_TCP },
#ifdef INET6
	{ "udp6", AF_INET6, IPPROTO_UDP },
	{ "tcp6", AF_INET6, IPPROTO_TCP },
#endif
	{ "local", AF_LOCAL, 0 }
};

#if 0
static char *strlocase __P((char *));
#endif
static int getnettype __P((const char *));

/*
 * Cache the result of getrlimit(), so we don't have to do an
 * expensive call every time.
 */
int
__rpc_dtbsize()
{
	static int tbsize;
	struct rlimit rl;

	if (tbsize) {
		return (tbsize);
	}
	if (getrlimit(RLIMIT_NOFILE, &rl) == 0) {
		return (tbsize = (int)rl.rlim_max);
	}
	/*
	 * Something wrong.  I'll try to save face by returning a
	 * pessimistic number.
	 */
	return (32);
}


/*
 * Find the appropriate buffer size
 */
u_int
/*ARGSUSED*/
__rpc_get_t_size(af, proto, size)
	int af, proto;
	int size;	/* Size requested */
{
	int maxsize, defsize;

	maxsize = 256 * 1024;	/* XXX */
	switch (proto) {
	case IPPROTO_TCP:
		defsize = 64 * 1024;	/* XXX */
		break;
	case IPPROTO_UDP:
		defsize = UDPMSGSIZE;
		break;
	default:
		defsize = RPC_MAXDATASIZE;
		break;
	}
	if (size == 0)
		return defsize;

	/* Check whether the value is within the upper max limit */
	return (size > maxsize ? (u_int)maxsize : (u_int)size);
}

/*
 * Find the appropriate address buffer size
 */
u_int
__rpc_get_a_size(af)
	int af;
{
	switch (af) {
	case AF_INET:
		return sizeof (struct sockaddr_in);
#ifdef INET6
	case AF_INET6:
		return sizeof (struct sockaddr_in6);
#endif
	case AF_LOCAL:
		return sizeof (struct sockaddr_un);
	default:
		break;
	}
	return ((u_int)RPC_MAXADDRSIZE);
}

#if 0
static char *
strlocase(p)
	char *p;
{
	char *t = p;

	_DIAGASSERT(p != NULL);

	for (; *p; p++)
		if (isupper(*p))
			*p = tolower(*p);
	return (t);
}
#endif

/*
 * Returns the type of the network as defined in <rpc/nettype.h>
 * If nettype is NULL, it defaults to NETPATH.
 */
static int
getnettype(nettype)
	const char *nettype;
{
	int i;

	if ((nettype == NULL) || (nettype[0] == NULL)) {
		return (_RPC_NETPATH);	/* Default */
	}

#if 0
	nettype = strlocase(nettype);
#endif
	for (i = 0; _rpctypelist[i].name; i++)
		if (strcasecmp(nettype, _rpctypelist[i].name) == 0) {
			return (_rpctypelist[i].type);
		}
	return (_rpctypelist[i].type);
}

/*
 * For the given nettype (tcp or udp only), return the first structure found.
 * This should be freed by calling freenetconfigent()
 */

#ifdef _REENTRANT
static thread_key_t tcp_key, udp_key;
static once_t __rpc_getconfigp_once = ONCE_INITIALIZER;

static void
__rpc_getconfigp_setup(void)
{

	thr_keycreate(&tcp_key, free);
	thr_keycreate(&udp_key, free);
}
#endif

struct netconfig *
__rpc_getconfip(nettype)
	const char *nettype;
{
	char *netid;
	char *netid_tcp = (char *) NULL;
	char *netid_udp = (char *) NULL;
	static char *netid_tcp_main;
	static char *netid_udp_main;
	struct netconfig *dummy;
#ifdef _REENTRANT
	extern int __isthreaded;

	if (__isthreaded == 0) {
		netid_udp = netid_udp_main;
		netid_tcp = netid_tcp_main;
	} else {
		thr_once(&__rpc_getconfigp_once, __rpc_getconfigp_setup);
		netid_tcp = thr_getspecific(tcp_key);
		netid_udp = thr_getspecific(udp_key);
	}
#else
	netid_udp = netid_udp_main;
	netid_tcp = netid_tcp_main;
#endif

	_DIAGASSERT(nettype != NULL);

	if (!netid_udp && !netid_tcp) {
		struct netconfig *nconf;
		void *confighandle;

		if (!(confighandle = setnetconfig())) {
			syslog (LOG_ERR, "rpc: failed to open " NETCONFIG);
			return (NULL);
		}
		while ((nconf = getnetconfig(confighandle)) != NULL) {
			if (strcmp(nconf->nc_protofmly, NC_INET) == 0) {
				if (strcmp(nconf->nc_proto, NC_TCP) == 0) {
					netid_tcp = strdup(nconf->nc_netid);
#ifdef _REENTRANT
					if (__isthreaded == 0)
						netid_tcp_main = netid_tcp;
					else
						thr_setspecific(tcp_key,
							(void *) netid_tcp);
#else
					netid_tcp_main = netid_tcp;
#endif
				} else
				if (strcmp(nconf->nc_proto, NC_UDP) == 0) {
					netid_udp = strdup(nconf->nc_netid);
#ifdef _REENTRANT
					if (__isthreaded == 0)
						netid_udp_main = netid_udp;
					else
						thr_setspecific(udp_key,
							(void *) netid_udp);
#else
					netid_udp_main = netid_udp;
#endif
				}
			}
		}
		endnetconfig(confighandle);
	}
	if (strcmp(nettype, "udp") == 0)
		netid = netid_udp;
	else if (strcmp(nettype, "tcp") == 0)
		netid = netid_tcp;
	else {
		return (NULL);
	}
	if ((netid == NULL) || (netid[0] == NULL)) {
		return (NULL);
	}
	dummy = getnetconfigent(netid);
	return (dummy);
}

/*
 * Returns the type of the nettype, which should then be used with
 * __rpc_getconf().
 */
void *
__rpc_setconf(nettype)
	const char *nettype;
{
	struct handle *handle;

	/* nettype may be NULL; getnettype() supports that */

	handle = (struct handle *) malloc(sizeof (struct handle));
	if (handle == NULL) {
		return (NULL);
	}
	switch (handle->nettype = getnettype(nettype)) {
	case _RPC_NETPATH:
	case _RPC_CIRCUIT_N:
	case _RPC_DATAGRAM_N:
		if (!(handle->nhandle = setnetpath())) {
			free(handle);
			return (NULL);
		}
		handle->nflag = TRUE;
		break;
	case _RPC_VISIBLE:
	case _RPC_CIRCUIT_V:
	case _RPC_DATAGRAM_V:
	case _RPC_TCP:
	case _RPC_UDP:
		if (!(handle->nhandle = setnetconfig())) {
		        syslog (LOG_ERR, "rpc: failed to open " NETCONFIG);
			free(handle);
			return (NULL);
		}
		handle->nflag = FALSE;
		break;
	default:
		return (NULL);
	}

	return (handle);
}

/*
 * Returns the next netconfig struct for the given "net" type.
 * __rpc_setconf() should have been called previously.
 */
struct netconfig *
__rpc_getconf(vhandle)
	void *vhandle;
{
	struct handle *handle;
	struct netconfig *nconf;

	handle = (struct handle *)vhandle;
	if (handle == NULL) {
		return (NULL);
	}
	for (;;) {
		if (handle->nflag)
			nconf = getnetpath(handle->nhandle);
		else
			nconf = getnetconfig(handle->nhandle);
		if (nconf == NULL)
			break;
		if ((nconf->nc_semantics != NC_TPI_CLTS) &&
			(nconf->nc_semantics != NC_TPI_COTS) &&
			(nconf->nc_semantics != NC_TPI_COTS_ORD))
			continue;
		switch (handle->nettype) {
		case _RPC_VISIBLE:
			if (!(nconf->nc_flag & NC_VISIBLE))
				continue;
			/* FALLTHROUGH */
		case _RPC_NETPATH:	/* Be happy */
			break;
		case _RPC_CIRCUIT_V:
			if (!(nconf->nc_flag & NC_VISIBLE))
				continue;
			/* FALLTHROUGH */
		case _RPC_CIRCUIT_N:
			if ((nconf->nc_semantics != NC_TPI_COTS) &&
				(nconf->nc_semantics != NC_TPI_COTS_ORD))
				continue;
			break;
		case _RPC_DATAGRAM_V:
			if (!(nconf->nc_flag & NC_VISIBLE))
				continue;
			/* FALLTHROUGH */
		case _RPC_DATAGRAM_N:
			if (nconf->nc_semantics != NC_TPI_CLTS)
				continue;
			break;
		case _RPC_TCP:
			if (((nconf->nc_semantics != NC_TPI_COTS) &&
				(nconf->nc_semantics != NC_TPI_COTS_ORD)) ||
				(strcmp(nconf->nc_protofmly, NC_INET)
#ifdef INET6
				 && strcmp(nconf->nc_protofmly, NC_INET6))
#else
				)
#endif
				||
				strcmp(nconf->nc_proto, NC_TCP))
				continue;
			break;
		case _RPC_UDP:
			if ((nconf->nc_semantics != NC_TPI_CLTS) ||
				(strcmp(nconf->nc_protofmly, NC_INET)
#ifdef INET6
				&& strcmp(nconf->nc_protofmly, NC_INET6))
#else
				)
#endif
				||
				strcmp(nconf->nc_proto, NC_UDP))
				continue;
			break;
		}
		break;
	}
	return (nconf);
}

void
__rpc_endconf(vhandle)
	void * vhandle;
{
	struct handle *handle;

	handle = (struct handle *) vhandle;
	if (handle == NULL) {
		return;
	}
	if (handle->nflag) {
		endnetpath(handle->nhandle);
	} else {
		endnetconfig(handle->nhandle);
	}
	free(handle);
}

/*
 * Used to ping the NULL procedure for clnt handle.
 * Returns NULL if fails, else a non-NULL pointer.
 */
void *
rpc_nullproc(clnt)
	CLIENT *clnt;
{
	struct timeval TIMEOUT = {25, 0};

	if (clnt_call(clnt, NULLPROC, (xdrproc_t) xdr_void, NULL,
		(xdrproc_t) xdr_void, NULL, TIMEOUT) != RPC_SUCCESS) {
		return (NULL);
	}
	return ((void *) clnt);
}

/*
 * Try all possible transports until
 * one succeeds in finding the netconf for the given fd.
 */
struct netconfig *
__rpcgettp(fd)
	int fd;
{
	const char *netid;
	struct __rpc_sockinfo si;

	if (!__rpc_fd2sockinfo(fd, &si))
		return NULL;

	if (!__rpc_sockinfo2netid(&si, &netid))
		return NULL;

	/*LINTED const castaway*/
	return getnetconfigent((char *)netid);
}

int
__rpc_fd2sockinfo(int fd, struct __rpc_sockinfo *sip)
{
	socklen_t len;
	int type, proto;
	struct sockaddr_storage ss;

	_DIAGASSERT(sip != NULL);

	len = sizeof ss;
	if (getsockname(fd, (struct sockaddr *)(void *)&ss, &len) < 0)
		return 0;
	sip->si_alen = len;

	len = sizeof type;
	if (getsockopt(fd, SOL_SOCKET, SO_TYPE, &type, &len) < 0)
		return 0;

	/* XXX */
	if (ss.ss_family != AF_LOCAL) {
		if (type == SOCK_STREAM)
			proto = IPPROTO_TCP;
		else if (type == SOCK_DGRAM)
			proto = IPPROTO_UDP;
		else
			return 0;
	} else
		proto = 0;

	sip->si_af = ss.ss_family;
	sip->si_proto = proto;
	sip->si_socktype = type;

	return 1;
}

/*
 * Linear search, but the number of entries is small.
 */
int
__rpc_nconf2sockinfo(const struct netconfig *nconf, struct __rpc_sockinfo *sip)
{
	size_t i;

	_DIAGASSERT(nconf != NULL);
	_DIAGASSERT(sip != NULL);

	for (i = 0; i < (sizeof na_cvt) / (sizeof (struct netid_af)); i++)
		if (!strcmp(na_cvt[i].netid, nconf->nc_netid)) {
			sip->si_af = na_cvt[i].af;
			sip->si_proto = na_cvt[i].protocol;
			sip->si_socktype =
			    __rpc_seman2socktype((int)nconf->nc_semantics);
			if (sip->si_socktype == -1)
				return 0;
			sip->si_alen = __rpc_get_a_size(sip->si_af);
			return 1;
		}

	return 0;
}

int
__rpc_nconf2fd(const struct netconfig *nconf)
{
	struct __rpc_sockinfo si;

	_DIAGASSERT(nconf != NULL);

	if (!__rpc_nconf2sockinfo(nconf, &si))
		return 0;

	return socket(si.si_af, si.si_socktype, si.si_proto);
}

int
__rpc_sockinfo2netid(struct __rpc_sockinfo *sip, const char **netid)
{
	size_t i;

	_DIAGASSERT(sip != NULL);
	/* netid may be NULL */

	for (i = 0; i < (sizeof na_cvt) / (sizeof (struct netid_af)); i++)
		if (na_cvt[i].af == sip->si_af &&
		    na_cvt[i].protocol == sip->si_proto) {
			if (netid)
				*netid = na_cvt[i].netid;
			return 1;
		}

	return 0;
}

char *
taddr2uaddr(const struct netconfig *nconf, const struct netbuf *nbuf)
{
	struct __rpc_sockinfo si;

	_DIAGASSERT(nconf != NULL);
	_DIAGASSERT(nbuf != NULL);

	if (!__rpc_nconf2sockinfo(nconf, &si))
		return NULL;
	return __rpc_taddr2uaddr_af(si.si_af, nbuf);
}

struct netbuf *
uaddr2taddr(const struct netconfig *nconf, const char *uaddr)
{
	struct __rpc_sockinfo si;

	_DIAGASSERT(nconf != NULL);
	_DIAGASSERT(uaddr != NULL);

	if (!__rpc_nconf2sockinfo(nconf, &si))
		return NULL;
	return __rpc_uaddr2taddr_af(si.si_af, uaddr);
}

char *
__rpc_taddr2uaddr_af(int af, const struct netbuf *nbuf)
{
	char *ret;
	struct sockaddr_in *sinp;
	struct sockaddr_un *sun;
	char namebuf[INET_ADDRSTRLEN];
#ifdef INET6
	struct sockaddr_in6 *sin6;
	char namebuf6[INET6_ADDRSTRLEN];
#endif
	u_int16_t port;

	_DIAGASSERT(nbuf != NULL);

	switch (af) {
	case AF_INET:
		sinp = nbuf->buf;
		if (inet_ntop(af, &sinp->sin_addr, namebuf, sizeof namebuf)
		    == NULL)
			return NULL;
		port = ntohs(sinp->sin_port);
		if (asprintf(&ret, "%s.%u.%u", namebuf, ((u_int32_t)port) >> 8,
		    port & 0xff) < 0)
			return NULL;
		break;
#ifdef INET6
	case AF_INET6:
		sin6 = nbuf->buf;
		if (inet_ntop(af, &sin6->sin6_addr, namebuf6, sizeof namebuf6)
		    == NULL)
			return NULL;
		port = ntohs(sin6->sin6_port);
		if (asprintf(&ret, "%s.%u.%u", namebuf6, ((u_int32_t)port) >> 8,
		    port & 0xff) < 0)
			return NULL;
		break;
#endif
	case AF_LOCAL:
		sun = nbuf->buf;
		sun->sun_path[sizeof(sun->sun_path) - 1] = '\0'; /* safety */
		ret = strdup(sun->sun_path);
		break;
	default:
		return NULL;
	}

	return ret;
}

struct netbuf *
__rpc_uaddr2taddr_af(int af, const char *uaddr)
{
	struct netbuf *ret = NULL;
	char *addrstr, *p;
	unsigned port, portlo, porthi;
	struct sockaddr_in *sinp;
#ifdef INET6
	struct sockaddr_in6 *sin6;
#endif
	struct sockaddr_un *sun;

	_DIAGASSERT(uaddr != NULL);

	addrstr = strdup(uaddr);
	if (addrstr == NULL)
		return NULL;

	/*
	 * AF_LOCAL addresses are expected to be absolute
	 * pathnames, anything else will be AF_INET or AF_INET6.
	 */
	if (*addrstr != '/') {
		p = strrchr(addrstr, '.');
		if (p == NULL)
			goto out;
		portlo = (unsigned)atoi(p + 1);
		*p = '\0';

		p = strrchr(addrstr, '.');
		if (p == NULL)
			goto out;
		porthi = (unsigned)atoi(p + 1);
		*p = '\0';
		port = (porthi << 8) | portlo;
	}

	ret = (struct netbuf *)malloc(sizeof *ret);
	if (ret == NULL)
		goto out;

	switch (af) {
	case AF_INET:
		sinp = (struct sockaddr_in *)malloc(sizeof *sinp);
		if (sinp == NULL)
			goto out;
		memset(sinp, 0, sizeof *sinp);
		sinp->sin_family = AF_INET;
		sinp->sin_port = htons(port);
		if (inet_pton(AF_INET, addrstr, &sinp->sin_addr) <= 0) {
			free(sinp);
			free(ret);
			ret = NULL;
			goto out;
		}
		sinp->sin_len = ret->maxlen = ret->len = sizeof *sinp;
		ret->buf = sinp;
		break;
#ifdef INET6
	case AF_INET6:
		sin6 = (struct sockaddr_in6 *)malloc(sizeof *sin6);
		if (sin6 == NULL)
			goto out;
		memset(sin6, 0, sizeof *sin6);
		sin6->sin6_family = AF_INET6;
		sin6->sin6_port = htons(port);
		if (inet_pton(AF_INET6, addrstr, &sin6->sin6_addr) <= 0) {
			free(sin6);
			free(ret);
			ret = NULL;
			goto out;
		}
		sin6->sin6_len = ret->maxlen = ret->len = sizeof *sin6;
		ret->buf = sin6;
		break;
#endif
	case AF_LOCAL:
		sun = (struct sockaddr_un *)malloc(sizeof *sun);
		if (sun == NULL)
			goto out;
		memset(sun, 0, sizeof *sun);
		sun->sun_family = AF_LOCAL;
		strncpy(sun->sun_path, addrstr, sizeof(sun->sun_path) - 1);
		ret->len = ret->maxlen = sun->sun_len = SUN_LEN(sun);
		ret->buf = sun;
		break;
	default:
		break;
	}
out:
	free(addrstr);
	return ret;
}

int
__rpc_seman2socktype(int semantics)
{
	switch (semantics) {
	case NC_TPI_CLTS:
		return SOCK_DGRAM;
	case NC_TPI_COTS_ORD:
		return SOCK_STREAM;
	case NC_TPI_RAW:
		return SOCK_RAW;
	default:
		break;
	}

	return -1;
}

int
__rpc_socktype2seman(int socktype)
{
	switch (socktype) {
	case SOCK_DGRAM:
		return NC_TPI_CLTS;
	case SOCK_STREAM:
		return NC_TPI_COTS_ORD;
	case SOCK_RAW:
		return NC_TPI_RAW;
	default:
		break;
	}

	return -1;
}

/*
 * XXXX - IPv6 scope IDs can't be handled in universal addresses.
 * Here, we compare the original server address to that of the RPC
 * service we just received back from a call to rpcbind on the remote
 * machine. If they are both "link local" or "site local", copy
 * the scope id of the server address over to the service address.
 */
int
__rpc_fixup_addr(struct netbuf *new, const struct netbuf *svc)
{
#ifdef INET6
	struct sockaddr *sa_new, *sa_svc;
	struct sockaddr_in6 *sin6_new, *sin6_svc;

	_DIAGASSERT(new != NULL);
	_DIAGASSERT(svc != NULL);

	sa_svc = (struct sockaddr *)svc->buf;
	sa_new = (struct sockaddr *)new->buf;

	if (sa_new->sa_family == sa_svc->sa_family &&
	    sa_new->sa_family == AF_INET6) {
		sin6_new = (struct sockaddr_in6 *)new->buf;
		sin6_svc = (struct sockaddr_in6 *)svc->buf;

		if ((IN6_IS_ADDR_LINKLOCAL(&sin6_new->sin6_addr) &&
		     IN6_IS_ADDR_LINKLOCAL(&sin6_svc->sin6_addr)) ||
		    (IN6_IS_ADDR_SITELOCAL(&sin6_new->sin6_addr) &&
		     IN6_IS_ADDR_SITELOCAL(&sin6_svc->sin6_addr))) {
			sin6_new->sin6_scope_id = sin6_svc->sin6_scope_id;
		}
	}
#endif
	return 1;
}

int
__rpc_sockisbound(int fd)
{
	struct sockaddr_storage ss;
	socklen_t slen;

	slen = sizeof (struct sockaddr_storage);
	if (getsockname(fd, (struct sockaddr *)(void *)&ss, &slen) < 0)
		return 0;

	switch (ss.ss_family) {
		case AF_INET:
			return (((struct sockaddr_in *)
			    (void *)&ss)->sin_port != 0);
#ifdef INET6
		case AF_INET6:
			return (((struct sockaddr_in6 *)
			    (void *)&ss)->sin6_port != 0);
#endif
		case AF_LOCAL:
			/* XXX check this */
			return (((struct sockaddr_un *)
			    (void *)&ss)->sun_path[0] != '\0');
		default:
			break;
	}

	return 0;
}

/*	$OpenBSD: ip_id.c,v 1.6 2002/03/15 18:19:52 millert Exp $	*/

/*
 * Copyright 1998 Niels Provos <provos (at) citi.umich.edu>
 * All rights reserved.
 *
 * Theo de Raadt <deraadt (at) openbsd.org> came up with the idea of using
 * such a mathematical system to generate more random (yet non-repeating)
 * ids to solve the resolver/named problem.  But Niels designed the
 * actual system based on the constraints.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Niels Provos.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * seed = random 31bit
 * n = prime, g0 = generator to n,
 * j = random so that gcd(j,n-1) == 1
 * g = g0^j mod n will be a generator again.
 *
 * X[0] = random seed.
 * X[n] = a*X[n-1]+b mod m is a Linear Congruential Generator
 * with a = 7^(even random) mod m,
 *      b = random with gcd(b,m) == 1
 *      m = 1836660096 and a maximal period of m-1.
 *
 * The transaction id is determined by:
 * id[n] = seed xor (g^X[n] mod n)
 *
 * Effectivly the id is restricted to the lower 31 bits, thus
 * yielding two different cycles by toggling the msb on and off.
 * This avoids reuse issues caused by reseeding.
 */

#define RU_OUT  180		/* Time after wich will be reseeded */
#define RU_MAX	1000000000	/* Uniq cycle, avoid blackjack prediction */
#define RU_GEN	2		/* Starting generator */
#define RU_N	2147483629	/* RU_N-1 = 2^2*3^2*59652323 */
#define RU_AGEN	7		/* determine ru_a as RU_AGEN^(2*rand) */
#define RU_M	1836660096	/* RU_M = 2^7*3^15 - don't change */

#define PFAC_N 3
const static u_int32_t pfacts[PFAC_N] = {
	2,
	3,
	59652323
};

static u_int32_t ru_x;
static u_int32_t ru_seed, ru_seed2;
static u_int32_t ru_a, ru_b;
static u_int32_t ru_g;
static u_int32_t ru_counter = 0;
static u_int32_t ru_msb = 0;
static long ru_reseed;

static u_int32_t pmod(u_int32_t, u_int32_t, u_int32_t);
static void initid(void);

/*
 * Do a fast modular exponation, returned value will be in the range
 * of 0 - (mod-1)
 */
static u_int32_t
pmod(u_int32_t gen, u_int32_t exp, u_int32_t mod)
{
	u_int64_t s, t, u;

	s = 1;
	t = gen;
	u = exp;

	while (u) {
		if (u & 1)
			s = (s * t) % mod;
		u >>= 1;
		t = (t * t) % mod;
	}
	return ((u_int32_t)s & 0xffffffff);
}

/*
 * Initalizes the seed and chooses a suitable generator. Also toggles
 * the msb flag. The msb flag is used to generate two distinct
 * cycles of random numbers and thus avoiding reuse of ids.
 *
 * This function is called from id_randomid() when needed, an
 * application does not have to worry about it.
 */
static void
initid(void)
{
	u_int32_t j, i;
	int noprime = 1;
	struct timeval tv;

	ru_x = arc4random() % RU_M;

	/* 31 bits of random seed */
	ru_seed = arc4random() & INT32_MAX;
	ru_seed2 = arc4random() & INT32_MAX;

	/* Determine the LCG we use */
	ru_b = arc4random() | 1;
	ru_a = pmod(RU_AGEN, arc4random() & (~1U), RU_M);
	while (ru_b % 3 == 0)
		ru_b += 2;

	j = arc4random() % RU_N;

	/*
	 * Do a fast gcd(j,RU_N-1), so we can find a j with
	 * gcd(j, RU_N-1) == 1, giving a new generator for
	 * RU_GEN^j mod RU_N
	 */
	while (noprime) {
		for (i = 0; i < PFAC_N; i++)
			if (j % pfacts[i] == 0)
				break;

		if (i >= PFAC_N)
			noprime = 0;
		else
			j = (j + 1) % RU_N;
	}

	ru_g = pmod(RU_GEN, j, RU_N);
	ru_counter = 0;

	gettimeofday(&tv, NULL);
	ru_reseed = tv.tv_sec + RU_OUT;
	ru_msb = ru_msb ? 0 : 0x80000000;
}

u_int32_t
__rpc_getxid(void)
{
	int i, n;
	u_int32_t tmp;
	struct timeval tv;

	gettimeofday(&tv, NULL);
	if (ru_counter >= RU_MAX || tv.tv_sec > ru_reseed)
		initid();

	tmp = arc4random();

	/* Skip a random number of ids */
	n = tmp & 0x3; tmp = tmp >> 2;
	if (ru_counter + n >= RU_MAX)
		initid();

	for (i = 0; i <= n; i++) {
		/* Linear Congruential Generator */
		ru_x = (ru_a * ru_x + ru_b) % RU_M;
	}

	ru_counter += i;

	return (ru_seed ^ pmod(ru_g, ru_seed2 ^ ru_x,RU_N)) | ru_msb;
}