/*
 *      auth_time.c
 *
 * This module contains the private function __rpc_get_time_offset()
 * which will return the difference in seconds between the local system's
 * notion of time and a remote server's notion of time. This must be
 * possible without calling any functions that may invoke the name
 * service. (netdir_getbyxxx, getXbyY, etc). The function is used in the
 * synchronize call of the authdes code to synchronize clocks between
 * NIS+ clients and their servers.
 *
 * Note to minimize the amount of duplicate code, portions of the
 * synchronize() function were folded into this code, and the synchronize
 * call becomes simply a wrapper around this function. Further, if this
 * function is called with a timehost it *DOES* recurse to the name
 * server so don't use it in that mode if you are doing name service code.
 *
 *      Copyright (c) 1992 Sun Microsystems Inc.
 *      All rights reserved.
 *
 * Side effects :
 *      When called a client handle to a RPCBIND process is created
 *      and destroyed. Two strings "netid" and "uaddr" are malloc'd
 *      and returned. The SIGALRM processing is modified only if
 *      needed to deal with TCP connections.
 */

#include "namespace.h"
#include <stdio.h>
#include <syslog.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <netdb.h>
#include <sys/signal.h>
#include <sys/errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <rpc/rpc.h>
#include <rpc/rpc_com.h>
#include <rpc/rpcb_prot.h>
#undef NIS
#include <rpcsvc/nis.h>
#include "un-namespace.h"

extern int _rpc_dtablesize( void );

#ifdef TESTING
#define msg(x)  printf("ERROR: %s\n", x)
/* #define msg(x) syslog(LOG_ERR, "%s", x) */
#else
#define msg(x)
#endif

static int saw_alarm = 0;

static void
alarm_hndler(int s)
{
        saw_alarm = 1;
        return;
}

/*
 * The internet time server defines the epoch to be Jan 1, 1900
 * whereas UNIX defines it to be Jan 1, 1970. To adjust the result
 * from internet time-service time, into UNIX time we subtract the
 * following offset :
 */
#define NYEARS  (1970 - 1900)
#define TOFFSET ((u_long)60*60*24*(365*NYEARS + (NYEARS/4)))


/*
 * Stolen from rpc.nisd:
 * Turn a 'universal address' into a struct sockaddr_in.
 * Bletch.
 */
static int uaddr_to_sockaddr(char *uaddr, struct sockaddr_in *sin)
{
        unsigned char           p_bytes[2];
        int                     i;
        unsigned long           a[6];

        i = sscanf(uaddr, "%lu.%lu.%lu.%lu.%lu.%lu", &a[0], &a[1], &a[2],
                                                &a[3], &a[4], &a[5]);

        if (i < 6)
                return(1);

        for (i = 0; i < 4; i++)
                sin->sin_addr.s_addr |= (a[i] & 0x000000FF) << (8 * i);

        p_bytes[0] = (unsigned char)a[4] & 0x000000FF;
        p_bytes[1] = (unsigned char)a[5] & 0x000000FF;

        sin->sin_family = AF_INET; /* always */
        bcopy((char *)&p_bytes, (char *)&sin->sin_port, 2);

        return (0);
}

/*
 * free_eps()
 *
 * Free the strings that were strduped into the eps structure.
 */
static void
free_eps(endpoint eps[], int num)
{
        int             i;

        for (i = 0; i < num; i++) {
                free(eps[i].uaddr);
                free(eps[i].proto);
                free(eps[i].family);
        }
        return;
}

/*
 * get_server()
 *
 * This function constructs a nis_server structure description for the
 * indicated hostname.
 *
 * NOTE: There is a chance we may end up recursing here due to the
 * fact that gethostbyname() could do an NIS search. Ideally, the
 * NIS+ server will call __rpc_get_time_offset() with the nis_server
 * structure already populated.
 *
 * host  - name of the time host
 * srv   - nis_server struct to use.
 * eps[] - array of endpoints
 * maxep - max array size
 */
static nis_server *
get_server(struct sockaddr_in *sin, char *host, nis_server *srv,
    endpoint eps[], int maxep)
{
        char                    hname[256];
        int                     num_ep = 0, i;
        struct hostent          *he;
        struct hostent          dummy;
        char                    *ptr[2];
        endpoint                *ep;

        if (host == NULL && sin == NULL)
                return (NULL);

        if (sin == NULL) {
                he = gethostbyname(host);
                if (he == NULL)
                        return(NULL);
        } else {
                he = &dummy;
                ptr[0] = (char *)&sin->sin_addr.s_addr;
                ptr[1] = NULL;
                dummy.h_addr_list = ptr;
        }

        /*
         * This is lame. We go around once for TCP, then again
         * for UDP.
         */
        for (i = 0, ep = eps; (he->h_addr_list[i] != NULL) && (num_ep < maxep);
            i++, ep++, num_ep++) {
                struct in_addr *a;

                a = (struct in_addr *)he->h_addr_list[i];
                snprintf(hname, sizeof(hname), "%s.0.111", inet_ntoa(*a));
                ep->uaddr = strdup(hname);
                ep->family = strdup("inet");
                ep->proto =  strdup("tcp");
                if (ep->uaddr == NULL || ep->family == NULL || ep->proto == NULL) {
                        free_eps(eps, num_ep + 1);
                        return (NULL);
                }
        }

        for (i = 0; (he->h_addr_list[i] != NULL) && (num_ep < maxep);
            i++, ep++, num_ep++) {
                struct in_addr *a;

                a = (struct in_addr *)he->h_addr_list[i];
                snprintf(hname, sizeof(hname), "%s.0.111", inet_ntoa(*a));
                ep->uaddr = strdup(hname);
                ep->family = strdup("inet");
                ep->proto =  strdup("udp");
                if (ep->uaddr == NULL || ep->family == NULL || ep->proto == NULL) {
                        free_eps(eps, num_ep + 1);
                        return (NULL);
                }
        }

        srv->name = (nis_name) host;
        srv->ep.ep_len = num_ep;
        srv->ep.ep_val = eps;
        srv->key_type = NIS_PK_NONE;
        srv->pkey.n_bytes = NULL;
        srv->pkey.n_len = 0;
        return (srv);
}

/*
 * __rpc_get_time_offset()
 *
 * This function uses a nis_server structure to contact the a remote
 * machine (as named in that structure) and returns the offset in time
 * between that machine and this one. This offset is returned in seconds
 * and may be positive or negative.
 *
 * The first time through, a lot of fiddling is done with the netconfig
 * stuff to find a suitable transport. The function is very aggressive
 * about choosing UDP or at worst TCP if it can. This is because
 * those transports support both the RCPBIND call and the internet
 * time service.
 *
 * Once through, *uaddr is set to the universal address of
 * the machine and *netid is set to the local netid for the transport
 * that uaddr goes with. On the second call, the netconfig stuff
 * is skipped and the uaddr/netid pair are used to fetch the netconfig
 * structure and to then contact the machine for the time.
 *
 * td = "server" - "client"
 *
 * td    - Time difference
 * srv   - NIS Server description
 * thost - if no server, this is the timehost
 * uaddr - known universal address
 * netid - known network identifier
 */
int
__rpc_get_time_offset(struct timeval *td, nis_server *srv, char *thost,
    char **uaddr, struct sockaddr_in *netid)
{
        CLIENT                  *clnt;          /* Client handle        */
        endpoint                *ep,            /* useful endpoints     */
                                *useep = NULL;  /* endpoint of xp       */
        char                    *useua = NULL;  /* uaddr of selected xp */
        int                     epl, i;         /* counters             */
        enum clnt_stat          status;         /* result of clnt_call  */
        u_long                  thetime, delta;
        int                     needfree = 0;
        struct timeval          tv;
        int                     time_valid;
        int                     udp_ep = -1, tcp_ep = -1;
        int                     a1, a2, a3, a4;
        char                    ut[64], ipuaddr[64];
        endpoint                teps[32];
        nis_server              tsrv;
        void                    (*oldsig)(int) = NULL; /* old alarm handler */
        struct sockaddr_in      sin;
        socklen_t               len;
        int                     s = RPC_ANYSOCK;
        int                     type = 0;

        td->tv_sec = 0;
        td->tv_usec = 0;

        /*
         * First check to see if we need to find and address for this
         * server.
         */
        if (*uaddr == NULL) {
                if ((srv != NULL) && (thost != NULL)) {
                        msg("both timehost and srv pointer used!");
                        return (0);
                }
                if (! srv) {
                        srv = get_server(netid, thost, &tsrv, teps, 32);
                        if (srv == NULL) {
                                msg("unable to contruct server data.");
                                return (0);
                        }
                        needfree = 1;   /* need to free data in endpoints */
                }

                ep = srv->ep.ep_val;
                epl = srv->ep.ep_len;

                /* Identify the TCP and UDP endpoints */
                for (i = 0;
                        (i < epl) && ((udp_ep == -1) || (tcp_ep == -1)); i++) {
                        if (strcasecmp(ep[i].proto, "udp") == 0)
                                udp_ep = i;
                        if (strcasecmp(ep[i].proto, "tcp") == 0)
                                tcp_ep = i;
                }

                /* Check to see if it is UDP or TCP */
                if (tcp_ep > -1) {
                        useep = &ep[tcp_ep];
                        useua = ep[tcp_ep].uaddr;
                        type = SOCK_STREAM;
                } else if (udp_ep > -1) {
                        useep = &ep[udp_ep];
                        useua = ep[udp_ep].uaddr;
                        type = SOCK_DGRAM;
                }

                if (useep == NULL) {
                        msg("no acceptable transport endpoints.");
                        if (needfree)
                                free_eps(teps, tsrv.ep.ep_len);
                        return (0);
                }
        }

        /*
         * Create a sockaddr from the uaddr.
         */
        if (*uaddr != NULL)
                useua = *uaddr;

        /* Fixup test for NIS+ */
        sscanf(useua, "%d.%d.%d.%d.", &a1, &a2, &a3, &a4);
        sprintf(ipuaddr, "%d.%d.%d.%d.0.111", a1, a2, a3, a4);
        useua = &ipuaddr[0];

        bzero((char *)&sin, sizeof(sin));
        if (uaddr_to_sockaddr(useua, &sin)) {
                msg("unable to translate uaddr to sockaddr.");
                if (needfree)
                        free_eps(teps, tsrv.ep.ep_len);
                return (0);
        }

        /*
         * Create the client handle to rpcbind. Note we always try
         * version 3 since that is the earliest version that supports
         * the RPCB_GETTIME call. Also it is the version that comes
         * standard with SVR4. Since most everyone supports TCP/IP
         * we could consider trying the rtime call first.
         */
        clnt = clnttcp_create(&sin, RPCBPROG, RPCBVERS, &s, 0, 0);
        if (clnt == NULL) {
                msg("unable to create client handle to rpcbind.");
                if (needfree)
                        free_eps(teps, tsrv.ep.ep_len);
                return (0);
        }

        tv.tv_sec = 5;
        tv.tv_usec = 0;
        time_valid = 0;
        status = clnt_call(clnt, RPCBPROC_GETTIME, (xdrproc_t)xdr_void, NULL,
                                        (xdrproc_t)xdr_u_long, &thetime, tv);
        /*
         * The only error we check for is anything but success. In
         * fact we could have seen PROGMISMATCH if talking to a 4.1
         * machine (pmap v2) or TIMEDOUT if the net was busy.
         */
        if (status == RPC_SUCCESS)
                time_valid = 1;
        else {
                int save;

                /* Blow away possible stale CLNT handle. */
                if (clnt != NULL) {
                        clnt_destroy(clnt);
                        clnt = NULL;
                }

                /*
                 * Convert PMAP address into timeservice address
                 * We take advantage of the fact that we "know" what
                 * the universal address looks like for inet transports.
                 *
                 * We also know that the internet timeservice is always
                 * listening on port 37.
                 */
                sscanf(useua, "%d.%d.%d.%d.", &a1, &a2, &a3, &a4);
                sprintf(ut, "%d.%d.%d.%d.0.37", a1, a2, a3, a4);

                if (uaddr_to_sockaddr(ut, &sin)) {
                        msg("cannot convert timeservice uaddr to sockaddr.");
                        goto error;
                }

                s = _socket(AF_INET, type, 0);
                if (s == -1) {
                        msg("unable to open fd to network.");
                        goto error;
                }

                /*
                 * Now depending on whether or not we're talking to
                 * UDP we set a timeout or not.
                 */
                if (type == SOCK_DGRAM) {
                        struct timeval timeout = { 20, 0 };
                        struct sockaddr_in from;
                        fd_set readfds;
                        int res;

                        if (_sendto(s, &thetime, sizeof(thetime), 0,
                                (struct sockaddr *)&sin, sizeof(sin)) == -1) {
                                msg("udp : sendto failed.");
                                goto error;
                        }
                        do {
                                FD_ZERO(&readfds);
                                FD_SET(s, &readfds);
                                res = _select(_rpc_dtablesize(), &readfds,
                                     (fd_set *)NULL, (fd_set *)NULL, &timeout);
                        } while (res < 0 && errno == EINTR);
                        if (res <= 0)
                                goto error;
                        len = sizeof(from);
                        res = _recvfrom(s, (char *)&thetime, sizeof(thetime), 0,
                                       (struct sockaddr *)&from, &len);
                        if (res == -1) {
                                msg("recvfrom failed on udp transport.");
                                goto error;
                        }
                        time_valid = 1;
                } else {
                        int res;

                        oldsig = (void (*)(int))signal(SIGALRM, alarm_hndler);
                        saw_alarm = 0; /* global tracking the alarm */
                        alarm(20); /* only wait 20 seconds */
                        res = _connect(s, (struct sockaddr *)&sin, sizeof(sin));
                        if (res == -1) {
                                msg("failed to connect to tcp endpoint.");
                                goto error;
                        }
                        if (saw_alarm) {
                                msg("alarm caught it, must be unreachable.");
                                goto error;
                        }
                        res = _read(s, (char *)&thetime, sizeof(thetime));
                        if (res != sizeof(thetime)) {
                                if (saw_alarm)
                                        msg("timed out TCP call.");
                                else
                                        msg("wrong size of results returned");

                                goto error;
                        }
                        time_valid = 1;
                }
                save = errno;
                (void)_close(s);
                errno = save;
                s = RPC_ANYSOCK;

                if (time_valid) {
                        thetime = ntohl(thetime);
                        thetime = thetime - TOFFSET; /* adjust to UNIX time */
                } else
                        thetime = 0;
        }

        gettimeofday(&tv, 0);

error:
        /*
         * clean up our allocated data structures.
         */

        if (s != RPC_ANYSOCK)
                (void)_close(s);

        if (clnt != NULL)
                clnt_destroy(clnt);

        alarm(0);       /* reset that alarm if its outstanding */
        if (oldsig) {
                signal(SIGALRM, oldsig);
        }

        /*
         * note, don't free uaddr strings until after we've made a
         * copy of them.
         */
        if (time_valid) {
                if (*uaddr == NULL)
                        *uaddr = strdup(useua);

                /* Round to the nearest second */
                tv.tv_sec += (tv.tv_sec > 500000) ? 1 : 0;
                delta = (thetime > tv.tv_sec) ? thetime - tv.tv_sec :
                                                tv.tv_sec - thetime;
                td->tv_sec = (thetime < tv.tv_sec) ? - delta : delta;
                td->tv_usec = 0;
        } else {
                msg("unable to get the server's time.");
        }

        if (needfree)
                free_eps(teps, tsrv.ep.ep_len);

        return (time_valid);
}