/* $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; }