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/* $OpenBSD: ip_ftp_pxy.c,v 1.2 1998/02/17 01:39:04 dgregor Exp $ */
/*
* Simple FTP transparent proxy for in-kernel use. For use with the NAT
* code.
*/
#define isdigit(x) ((x) >= '0' && (x) <= '9')
#define IPF_FTP_PROXY
#define IPF_MINPORTLEN 18
#define IPF_MAXPORTLEN 30
int ippr_ftp_init __P((fr_info_t *, ip_t *, tcphdr_t *,
ap_session_t *, nat_t *));
int ippr_ftp_in __P((fr_info_t *, ip_t *, tcphdr_t *,
ap_session_t *, nat_t *));
int ippr_ftp_out __P((fr_info_t *, ip_t *, tcphdr_t *,
ap_session_t *, nat_t *));
u_short ipf_ftp_atoi __P((char **));
int ippr_ftp_init __P((fr_info_t *, ip_t *, tcphdr_t *, ap_session_t *,
nat_t *));
int ippr_ftp_in __P((fr_info_t *, ip_t *, tcphdr_t *, ap_session_t *,
nat_t *));
int ippr_ftp_out __P((fr_info_t *, ip_t *, tcphdr_t *, ap_session_t *,
nat_t *));
u_short ipf_ftp_atoi __P((char **));
/*
* FTP application proxy initialization.
*/
int ippr_ftp_init(fin, ip, tcp, aps, nat)
fr_info_t *fin;
ip_t *ip;
tcphdr_t *tcp;
ap_session_t *aps;
nat_t *nat;
{
aps->aps_sport = tcp->th_sport;
aps->aps_dport = tcp->th_dport;
return 0;
}
int ippr_ftp_in(fin, ip, tcp, aps, nat)
fr_info_t *fin;
ip_t *ip;
tcphdr_t *tcp;
ap_session_t *aps;
nat_t *nat;
{
u_long sum1, sum2;
short sel;
if (tcp->th_sport == aps->aps_dport) {
sum2 = (u_long)ntohl(tcp->th_ack);
sel = aps->aps_sel;
if ((aps->aps_after[!sel] > aps->aps_after[sel]) &&
(sum2 > aps->aps_after[!sel])) {
sel = aps->aps_sel = !sel; /* switch to other set */
}
if (aps->aps_seqoff[sel] && (sum2 > aps->aps_after[sel])) {
sum1 = (u_long)aps->aps_seqoff[sel];
tcp->th_ack = htonl(sum2 - sum1);
return 2;
}
}
return 0;
}
/*
* ipf_ftp_atoi - implement a version of atoi which processes numbers in
* pairs separated by commas (which are expected to be in the range 0 - 255),
* returning a 16 bit number combining either side of the , as the MSB and
* LSB.
*/
u_short ipf_ftp_atoi(ptr)
char **ptr;
{
register char *s = *ptr, c;
register u_char i = 0, j = 0;
while ((c = *s++) && isdigit(c)) {
i *= 10;
i += c - '0';
}
if (c != ',') {
*ptr = NULL;
return 0;
}
while ((c = *s++) && isdigit(c)) {
j *= 10;
j += c - '0';
}
*ptr = s;
return (i << 8) | j;
}
int ippr_ftp_out(fin, ip, tcp, aps, nat)
fr_info_t *fin;
ip_t *ip;
tcphdr_t *tcp;
ap_session_t *aps;
nat_t *nat;
{
register u_long sum1, sum2;
char newbuf[IPF_MAXPORTLEN+1];
char portbuf[IPF_MAXPORTLEN+1], *s;
int ch = 0, off = (ip->ip_hl << 2) + (tcp->th_off << 2);
u_int a1, a2, a3, a4;
u_short a5, a6;
int olen, dlen, nlen = 0, inc = 0;
tcphdr_t tcph, *tcp2 = &tcph;
void *savep;
nat_t *ipn;
struct in_addr swip;
mb_t *m = *(mb_t **)fin->fin_mp;
#if SOLARIS
mb_t *m1;
/* skip any leading M_PROTOs */
while(m && (MTYPE(m) != M_DATA))
m = m->b_cont;
PANIC((!m),("ippr_ftp_out: no M_DATA"));
dlen = msgdsize(m) - off;
bzero(portbuf, sizeof(portbuf));
copyout_mblk(m, off, MIN(sizeof(portbuf), dlen), portbuf);
#else
dlen = mbufchainlen(m) - off;
bzero(portbuf, sizeof(portbuf));
m_copydata(m, off, MIN(sizeof(portbuf), dlen), portbuf);
#endif
portbuf[IPF_MAXPORTLEN] = '\0';
if ((dlen < IPF_MINPORTLEN) || strncmp(portbuf, "PORT ", 5))
goto adjust_seqack;
/*
* Skip the PORT command + space
*/
s = portbuf + 5;
/*
* Pick out the address components, two at a time.
*/
(void) ipf_ftp_atoi(&s);
if (!s)
goto adjust_seqack;
(void) ipf_ftp_atoi(&s);
if (!s)
goto adjust_seqack;
a5 = ipf_ftp_atoi(&s);
if (!s)
goto adjust_seqack;
/*
* check for CR-LF at the end.
*/
if (*s != '\n' || *(s - 1) != '\r')
goto adjust_seqack;
a6 = a5 & 0xff;
a5 >>= 8;
/*
* Calculate new address parts for PORT command
*/
a1 = ntohl(ip->ip_src.s_addr);
a2 = (a1 >> 16) & 0xff;
a3 = (a1 >> 8) & 0xff;
a4 = a1 & 0xff;
a1 >>= 24;
olen = s - portbuf + 1;
(void) sprintf(newbuf, "PORT %d,%d,%d,%d,%d,%d\r\n",
a1, a2, a3, a4, a5, a6);
nlen = strlen(newbuf);
inc = nlen - olen;
#if SOLARIS
for (m1 = m; m1->b_cont; m1 = m1->b_cont)
;
if (inc > 0) {
mblk_t *nm;
/* alloc enough to keep same trailer space for lower driver */
nm = allocb(nlen + m1->b_datap->db_lim - m1->b_wptr, BPRI_MED);
PANIC((!nm),("ippr_ftp_out: allocb failed"));
nm->b_band = m1->b_band;
nm->b_wptr += nlen;
m1->b_wptr -= olen;
PANIC((m1->b_wptr < m1->b_rptr),("ippr_ftp_out: cannot handle fragmented data block"));
linkb(m1, nm);
} else {
m1->b_wptr += inc;
}
copyin_mblk(m, off, nlen, newbuf);
#else
if (inc < 0)
m_adj(m, inc);
/* the mbuf chain will be extended if necessary by m_copyback() */
m_copyback(m, off, nlen, newbuf);
#endif
if (inc) {
#if SOLARIS || defined(__sgi)
sum1 = ip->ip_len;
sum2 = ip->ip_len + inc;
/* Because ~1 == -2, We really need ~1 == -1 */
if (sum1 > sum2)
sum2--;
sum2 -= sum1;
sum2 = (sum2 & 0xffff) + (sum2 >> 16);
fix_outcksum(&ip->ip_sum, sum2);
#endif
ip->ip_len += inc;
}
ch = 1;
/*
* Add skeleton NAT entry for connection which will come back the
* other way.
*/
savep = fin->fin_dp;
fin->fin_dp = (char *)tcp2;
bzero((char *)tcp2, sizeof(*tcp2));
tcp2->th_sport = htons(a5 << 8 | a6);
tcp2->th_dport = htons(20);
swip = ip->ip_src;
ip->ip_src = nat->nat_inip;
if ((ipn = nat_new(nat->nat_ptr, ip, fin, IPN_TCP, NAT_OUTBOUND)))
ipn->nat_age = fr_defnatage;
(void) fr_addstate(ip, fin, FR_INQUE|FR_PASS|FR_QUICK|FR_KEEPSTATE);
ip->ip_src = swip;
fin->fin_dp = (char *)savep;
adjust_seqack:
if (tcp->th_dport == aps->aps_dport) {
sum2 = (u_long)ntohl(tcp->th_seq);
off = aps->aps_sel;
if ((aps->aps_after[!off] > aps->aps_after[off]) &&
(sum2 > aps->aps_after[!off])) {
off = aps->aps_sel = !off; /* switch to other set */
}
if (aps->aps_seqoff[off]) {
sum1 = (u_long)aps->aps_after[off] -
aps->aps_seqoff[off];
if (sum2 > sum1) {
sum1 = (u_long)aps->aps_seqoff[off];
sum2 += sum1;
tcp->th_seq = htonl(sum2);
ch = 1;
}
}
if (inc && (sum2 > aps->aps_after[!off])) {
aps->aps_after[!off] = sum2 + nlen - 1;
aps->aps_seqoff[!off] = aps->aps_seqoff[off] + inc;
}
}
return ch ? 2 : 0;
}
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