/*
 * Copyright (C) 2012 by Darren Reed.
 *
 * See the IPFILTER.LICENCE file for details on licencing.
 *
 * $Id$
 */

#define IPF_IRC_PROXY

#define IPF_IRCBUFSZ    96      /* This *MUST* be >= 64! */


void ipf_p_irc_main_load(void);
void ipf_p_irc_main_unload(void);
int ipf_p_irc_new(void *, fr_info_t *, ap_session_t *, nat_t *);
int ipf_p_irc_out(void *, fr_info_t *, ap_session_t *, nat_t *);
int ipf_p_irc_send(fr_info_t *, nat_t *);
int ipf_p_irc_complete(ircinfo_t *, char *, size_t);
u_short ipf_irc_atoi(char **);

static  frentry_t       ircnatfr;

int     irc_proxy_init = 0;


/*
 * Initialize local structures.
 */
void
ipf_p_irc_main_load(void)
{
        bzero((char *)&ircnatfr, sizeof(ircnatfr));
        ircnatfr.fr_ref = 1;
        ircnatfr.fr_flags = FR_INQUE|FR_PASS|FR_QUICK|FR_KEEPSTATE;
        MUTEX_INIT(&ircnatfr.fr_lock, "IRC proxy rule lock");
        irc_proxy_init = 1;
}


void
ipf_p_irc_main_unload(void)
{
        if (irc_proxy_init == 1) {
                MUTEX_DESTROY(&ircnatfr.fr_lock);
                irc_proxy_init = 0;
        }
}


const char *ipf_p_irc_dcctypes[] = {
        "CHAT ",        /* CHAT chat ipnumber portnumber */
        "SEND ",        /* SEND filename ipnumber portnumber */
        "MOVE ",
        "TSEND ",
        "SCHAT ",
        NULL,
};


/*
 * :A PRIVMSG B :^ADCC CHAT chat 0 0^A\r\n
 * PRIVMSG B ^ADCC CHAT chat 0 0^A\r\n
 */


int
ipf_p_irc_complete(ircinfo_t *ircp, char *buf, size_t len)
{
        register char *s, c;
        register size_t i;
        u_32_t l;
        int j, k;

        ircp->irc_ipnum = 0;
        ircp->irc_port = 0;

        if (len < 31)
                return (0);
        s = buf;
        c = *s++;
        i = len - 1;

        if ((c != ':') && (c != 'P'))
                return (0);

        if (c == ':') {
                /*
                 * Loosely check that the source is a nickname of some sort
                 */
                s++;
                c = *s;
                ircp->irc_snick = s;
                if (!ISALPHA(c))
                        return (0);
                i--;
                for (c = *s; !ISSPACE(c) && (i > 0); i--)
                        c = *s++;
                if (i < 31)
                        return (0);
                if (c != 'P')
                        return (0);
        } else
                ircp->irc_snick = NULL;

        /*
         * Check command string
         */
        if (strncmp(s, "PRIVMSG ", 8))
                return (0);
        i -= 8;
        s += 8;
        c = *s;
        ircp->irc_dnick = s;

        /*
         * Loosely check that the destination is a nickname of some sort
         */
        if (!ISALPHA(c))
                return (0);
        for (; !ISSPACE(c) && (i > 0); i--)
                c = *s++;
        if (i < 20)
                return (0);
        s++,
        i--;

        /*
         * Look for a ^A to start the DCC
         */
        c = *s;
        if (c == ':') {
                s++;
                c = *s;
        }

        if (strncmp(s, "\001DCC ", 4))
                return (0);

        i -= 4;
        s += 4;

        /*
         * Check for a recognised DCC command
         */
        for (j = 0, k = 0; ipf_p_irc_dcctypes[j]; j++) {
                k = MIN(strlen(ipf_p_irc_dcctypes[j]), i);
                if (!strncmp(ipf_p_irc_dcctypes[j], s, k))
                        break;
        }
        if (!ipf_p_irc_dcctypes[j])
                return (0);

        ircp->irc_type = s;
        i -= k;
        s += k;

        if (i < 11)
                return (0);

        /*
         * Check for the arg
         */
        c = *s;
        if (ISSPACE(c))
                return (0);
        ircp->irc_arg = s;
        for (; (c != ' ') && (c != '\001') && (i > 0); i--)
                c = *s++;

        if (c == '\001')        /* In reality a ^A can quote another ^A...*/
                return (0);

        if (i < 5)
                return (0);

        s++;
        i--;
        c = *s;
        if (!ISDIGIT(c))
                return (0);
        ircp->irc_addr = s;
        /*
         * Get the IP#
         */
        for (l = 0; ISDIGIT(c) && (i > 0); i--) {
                l *= 10;
                l += c - '0';
                c = *s++;
        }

        if (i < 4)
                return (0);

        if (c != ' ')
                return (0);

        ircp->irc_ipnum = l;
        s++;
        i--;
        c = *s;
        if (!ISDIGIT(c))
                return (0);
        /*
         * Get the port#
         */
        for (l = 0; ISDIGIT(c) && (i > 0); i--) {
                l *= 10;
                l += c - '0';
                c = *s++;
        }
        if (i < 3)
                return (0);
        if (strncmp(s, "\001\r\n", 3))
                return (0);
        s += 3;
        ircp->irc_len = s - buf;
        ircp->irc_port = l;
        return (1);
}


int
ipf_p_irc_new(void *arg, fr_info_t *fin, ap_session_t *aps, nat_t *nat __unused)
{
        ircinfo_t *irc;

        if (fin->fin_v != 4)
                return (-1);

        KMALLOC(irc, ircinfo_t *);
        if (irc == NULL)
                return (-1);

        aps->aps_data = irc;
        aps->aps_psiz = sizeof(ircinfo_t);

        bzero((char *)irc, sizeof(*irc));
        return (0);
}


int
ipf_p_irc_send(fr_info_t *fin, nat_t *nat)
{
        char ctcpbuf[IPF_IRCBUFSZ], newbuf[IPF_IRCBUFSZ];
        tcphdr_t *tcp, tcph, *tcp2 = &tcph;
        int off, inc = 0, i, dlen;
        ipf_main_softc_t *softc;
        size_t nlen = 0, olen;
        struct in_addr swip;
        u_short a5, sp;
        ircinfo_t *irc;
        fr_info_t fi;
        nat_t *nat2;
        u_int a1;
        ip_t *ip;
        mb_t *m;
#if SOLARIS
        mb_t *m1;
#endif
        softc = fin->fin_main_soft;

        m = fin->fin_m;
        ip = fin->fin_ip;
        tcp = (tcphdr_t *)fin->fin_dp;
        bzero(ctcpbuf, sizeof(ctcpbuf));
        off = (char *)tcp - (char *)ip + (TCP_OFF(tcp) << 2) + fin->fin_ipoff;

        dlen = MSGDSIZE(m) - off;
        if (dlen <= 0)
                return (0);
        COPYDATA(m, off, MIN(sizeof(ctcpbuf), dlen), ctcpbuf);

        if (dlen <= 0)
                return (0);
        ctcpbuf[sizeof(ctcpbuf) - 1] = '\0';
        *newbuf = '\0';

        irc = nat->nat_aps->aps_data;
        if (ipf_p_irc_complete(irc, ctcpbuf, dlen) == 0)
                return (0);

        /*
         * check that IP address in the DCC reply is the same as the
         * sender of the command - prevents use for port scanning.
         */
        if (irc->irc_ipnum != ntohl(nat->nat_osrcaddr))
                return (0);

        a5 = irc->irc_port;

        /*
         * Calculate new address parts for the DCC command
         */
        a1 = ntohl(ip->ip_src.s_addr);
        olen = irc->irc_len;
        i = irc->irc_addr - ctcpbuf;
        i++;
        (void) strncpy(newbuf, ctcpbuf, i);
        /* DO NOT change these! */
        (void) snprintf(newbuf, sizeof(newbuf), "%u %u\001\r\n", a1, a5);

        nlen = strlen(newbuf);
        inc = nlen - olen;

        if ((inc + fin->fin_plen) > 65535)
                return (0);

#if SOLARIS
        for (m1 = m; m1->b_cont; m1 = m1->b_cont)
                ;
        if ((inc > 0) && (m1->b_datap->db_lim - m1->b_wptr < inc)) {
                mblk_t *nm;

                /* alloc enough to keep same trailer space for lower driver */
                nm = allocb(nlen, BPRI_MED);
                PANIC((!nm),("ipf_p_irc_out: allocb failed"));

                nm->b_band = m1->b_band;
                nm->b_wptr += nlen;

                m1->b_wptr -= olen;
                PANIC((m1->b_wptr < m1->b_rptr),
                      ("ipf_p_irc_out: cannot handle fragmented data block"));

                linkb(m1, nm);
        } else {
# if SOLARIS && defined(ICK_VALID)
                if (m1->b_datap->db_struiolim == m1->b_wptr)
                        m1->b_datap->db_struiolim += inc;
                m1->b_datap->db_struioflag &= ~STRUIO_IP;
# endif
                m1->b_wptr += inc;
        }
#else
        if (inc < 0)
                m_adj(m, inc);
        /* the mbuf chain will be extended if necessary by m_copyback() */
#endif
        COPYBACK(m, off, nlen, newbuf);
        fin->fin_flx |= FI_DOCKSUM;

        if (inc != 0) {
#if SOLARIS
                register u_32_t sum1, sum2;

                sum1 = fin->fin_plen;
                sum2 = fin->fin_plen + inc;

                /* Because ~1 == -2, We really need ~1 == -1 */
                if (sum1 > sum2)
                        sum2--;
                sum2 -= sum1;
                sum2 = (sum2 & 0xffff) + (sum2 >> 16);

                ipf_fix_outcksum(0, &ip->ip_sum, sum2, 0);
#endif
                fin->fin_plen += inc;
                ip->ip_len = htons(fin->fin_plen);
                fin->fin_dlen += inc;
        }

        /*
         * Add skeleton NAT entry for connection which will come back the
         * other way.
         */
        sp = htons(a5);
        /*
         * Don't allow the PORT command to specify a port < 1024 due to
         * security crap.
         */
        if (ntohs(sp) < 1024)
                return (0);

        /*
         * The server may not make the connection back from port 20, but
         * it is the most likely so use it here to check for a conflicting
         * mapping.
         */
        bcopy((caddr_t)fin, (caddr_t)&fi, sizeof(fi));
        fi.fin_data[0] = sp;
        fi.fin_data[1] = fin->fin_data[1];
        nat2 = ipf_nat_outlookup(fin, IPN_TCP, nat->nat_pr[1], nat->nat_nsrcip,
                             ip->ip_dst);
        if (nat2 == NULL) {
#ifdef USE_MUTEXES
                ipf_nat_softc_t *softn = softc->ipf_nat_soft;
#endif

                bcopy((caddr_t)fin, (caddr_t)&fi, sizeof(fi));
                bzero((char *)tcp2, sizeof(*tcp2));
                tcp2->th_win = htons(8192);
                tcp2->th_sport = sp;
                tcp2->th_dport = 0; /* XXX - don't specify remote port */
                fi.fin_data[0] = ntohs(sp);
                fi.fin_data[1] = 0;
                fi.fin_dp = (char *)tcp2;
                fi.fin_fr = &ircnatfr;
                fi.fin_dlen = sizeof(*tcp2);
                fi.fin_plen = fi.fin_hlen + sizeof(*tcp2);
                swip = ip->ip_src;
                ip->ip_src = nat->nat_nsrcip;
                MUTEX_ENTER(&softn->ipf_nat_new);
                nat2 = ipf_nat_add(&fi, nat->nat_ptr, NULL,
                               NAT_SLAVE|IPN_TCP|SI_W_DPORT, NAT_OUTBOUND);
                MUTEX_EXIT(&softn->ipf_nat_new);
                if (nat2 != NULL) {
                        (void) ipf_nat_proto(&fi, nat2, 0);
                        MUTEX_ENTER(&nat2->nat_lock);
                        ipf_nat_update(&fi, nat2);
                        MUTEX_EXIT(&nat2->nat_lock);

                        (void) ipf_state_add(softc, &fi, NULL, SI_W_DPORT);
                }
                ip->ip_src = swip;
        }
        return (inc);
}


int
ipf_p_irc_out(void *arg, fr_info_t *fin, ap_session_t *aps __unused, nat_t *nat)
{
        return (ipf_p_irc_send(fin, nat));
}