static int ProtoAliasIn(struct libalias *la, struct in_addr ip_src, struct in_addr *ip_dst, u_char ip_p, u_short *ip_sum) { /* Handle incoming IP packets. The only thing which is done in this case is to alias the dest IP address of the packet to our inside machine. */ struct alias_link *lnk; LIBALIAS_LOCK_ASSERT(la); /* Return if proxy-only mode is enabled */ if (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY) return (PKT_ALIAS_OK); lnk = FindProtoIn(la, ip_src, *ip_dst, ip_p); if (lnk != NULL) { struct in_addr original_address; original_address = GetOriginalAddress(lnk); /* Restore original IP address */ DifferentialChecksum(ip_sum, &original_address, ip_dst, 2); *ip_dst = original_address; return (PKT_ALIAS_OK); } return (PKT_ALIAS_IGNORED); }
static int AliasHandlePptpGreIn(struct libalias *la, struct ip *pip) { GreHdr *gr; struct alias_link *lnk; gr = (GreHdr *) ip_next(pip); /* Check GRE header bits. */ if ((ntohl(*((u_int32_t *) gr)) & PPTP_INIT_MASK) != PPTP_INIT_VALUE) return (-1); lnk = FindPptpInByPeerCallId(la, pip->ip_src, pip->ip_dst, gr->gh_call_id); if (lnk != NULL) { struct in_addr src_addr = GetOriginalAddress(lnk); /* De-alias the Peer's Call Id. */ gr->gh_call_id = GetOriginalPort(lnk); /* Restore original IP address. */ DifferentialChecksum(&pip->ip_sum, &src_addr, &pip->ip_dst, 2); pip->ip_dst = src_addr; } return (0); }
static int ProtoAliasIn(struct ip *pip) { /* Handle incoming IP packets. The only thing which is done in this case is to alias the dest IP address of the packet to our inside machine. */ struct alias_link *link; /* Return if proxy-only mode is enabled */ if (packetAliasMode & PKT_ALIAS_PROXY_ONLY) return PKT_ALIAS_OK; link = FindProtoIn(pip->ip_src, pip->ip_dst, pip->ip_p); if (link != NULL) { struct in_addr original_address; original_address = GetOriginalAddress(link); /* Restore original IP address */ DifferentialChecksum(&pip->ip_sum, (u_short *) &original_address, (u_short *) &pip->ip_dst, 2); pip->ip_dst = original_address; return(PKT_ALIAS_OK); } return(PKT_ALIAS_IGNORED); }
static void AliasHandleFtpIn(struct libalias *la, struct ip *pip, /* IP packet to examine/patch */ struct alias_link *lnk) /* The link to go through (aliased port) */ { int hlen, tlen, dlen, pflags; char *sptr; struct tcphdr *tc; /* Calculate data length of TCP packet */ tc = (struct tcphdr *)ip_next(pip); hlen = (pip->ip_hl + tc->th_off) << 2; tlen = ntohs(pip->ip_len); dlen = tlen - hlen; /* Place string pointer and beginning of data */ sptr = (char *)pip; sptr += hlen; /* * Check that data length is not too long and previous message was * properly terminated with CRLF. */ pflags = GetProtocolFlags(lnk); if (dlen <= MAX_MESSAGE_SIZE && (pflags & WAIT_CRLF) == 0 && ntohs(tc->th_dport) == FTP_CONTROL_PORT_NUMBER && (ParseFtpPortCommand(la, sptr, dlen) != 0 || ParseFtpEprtCommand(la, sptr, dlen) != 0)) { /* * Alias active mode client requesting data from server * behind NAT. We need to alias server->client connection * to external address client is connecting to. */ AddLink(la, GetOriginalAddress(lnk), la->true_addr, GetAliasAddress(lnk), htons(FTP_CONTROL_PORT_NUMBER - 1), htons(la->true_port), GET_ALIAS_PORT, IPPROTO_TCP); } /* Track the msgs which are CRLF term'd for PORT/PASV FW breach */ if (dlen) { sptr = (char *)pip; /* start over at beginning */ tlen = ntohs(pip->ip_len); /* recalc tlen, pkt may * have grown. */ if (sptr[tlen - 2] == '\r' && sptr[tlen - 1] == '\n') pflags &= ~WAIT_CRLF; else pflags |= WAIT_CRLF; SetProtocolFlags(lnk, pflags); } }
static int IcmpAliasIn1(struct libalias *la, struct ip *pip) { /* De-alias incoming echo and timestamp replies. Alias incoming echo and timestamp requests. */ struct alias_link *lnk; struct icmp *ic; LIBALIAS_LOCK_ASSERT(la); ic = (struct icmp *)ip_next(pip); /* Get source address from ICMP data field and restore original data */ lnk = FindIcmpIn(la, pip->ip_src, pip->ip_dst, ic->icmp_id, 1); if (lnk != NULL) { u_short original_id; int accumulate; original_id = GetOriginalPort(lnk); /* Adjust ICMP checksum */ accumulate = ic->icmp_id; accumulate -= original_id; ADJUST_CHECKSUM(accumulate, ic->icmp_cksum); /* Put original sequence number back in */ ic->icmp_id = original_id; /* Put original address back into IP header */ { struct in_addr original_address; original_address = GetOriginalAddress(lnk); DifferentialChecksum(&pip->ip_sum, &original_address, &pip->ip_dst, 2); pip->ip_dst = original_address; } return (PKT_ALIAS_OK); } return (PKT_ALIAS_IGNORED); }
static int alias_rtsp_out(struct libalias *la, struct ip *pip, struct alias_link *lnk, char *data, const char *port_str) { int hlen, tlen, dlen; struct tcphdr *tc; int i, j, pos, state, port_dlen, new_dlen, delta; u_short p[2], new_len; u_short sport, eport, base_port; u_short salias = 0, ealias = 0, base_alias = 0; const char *transport_str = "transport:"; char newdata[2048], *port_data, *port_newdata, stemp[80]; int links_created = 0, pkt_updated = 0; struct alias_link *rtsp_lnk = NULL; struct in_addr null_addr; /* Calculate data length of TCP packet */ tc = (struct tcphdr *)ip_next(pip); hlen = (pip->ip_hl + tc->th_off) << 2; tlen = ntohs(pip->ip_len); dlen = tlen - hlen; /* Find keyword, "Transport: " */ pos = search_string(data, dlen, transport_str); if (pos < 0) { return (-1); } port_data = data + pos; port_dlen = dlen - pos; memcpy(newdata, data, pos); port_newdata = newdata + pos; while (port_dlen > (int)strlen(port_str)) { /* Find keyword, appropriate port string */ pos = search_string(port_data, port_dlen, port_str); if (pos < 0) { break; } memcpy(port_newdata, port_data, pos + 1); port_newdata += (pos + 1); p[0] = p[1] = 0; sport = eport = 0; state = 0; for (i = pos; i < port_dlen; i++) { switch (state) { case 0: if (port_data[i] == '=') { state++; } break; case 1: if (ISDIGIT(port_data[i])) { p[0] = p[0] * 10 + port_data[i] - '0'; } else { if (port_data[i] == ';') { state = 3; } if (port_data[i] == '-') { state++; } } break; case 2: if (ISDIGIT(port_data[i])) { p[1] = p[1] * 10 + port_data[i] - '0'; } else { state++; } break; case 3: base_port = p[0]; sport = htons(p[0]); eport = htons(p[1]); if (!links_created) { links_created = 1; /* * Find an even numbered port * number base that satisfies the * contiguous number of ports we * need */ null_addr.s_addr = 0; if (0 == (salias = FindNewPortGroup(la, null_addr, FindAliasAddress(la, pip->ip_src), sport, 0, RTSP_PORT_GROUP, IPPROTO_UDP, 1))) { #ifdef LIBALIAS_DEBUG fprintf(stderr, "PacketAlias/RTSP: Cannot find contiguous RTSP data ports\n"); #endif } else { base_alias = ntohs(salias); for (j = 0; j < RTSP_PORT_GROUP; j++) { /* * Establish link * to port found in * RTSP packet */ rtsp_lnk = FindRtspOut(la, GetOriginalAddress(lnk), null_addr, htons(base_port + j), htons(base_alias + j), IPPROTO_UDP); if (rtsp_lnk != NULL) { #ifndef NO_FW_PUNCH /* * Punch * hole in * firewall */ PunchFWHole(rtsp_lnk); #endif } else { #ifdef LIBALIAS_DEBUG fprintf(stderr, "PacketAlias/RTSP: Cannot allocate RTSP data ports\n"); #endif break; } } } ealias = htons(base_alias + (RTSP_PORT_GROUP - 1)); } if (salias && rtsp_lnk) { pkt_updated = 1; /* Copy into IP packet */ sprintf(stemp, "%d", ntohs(salias)); memcpy(port_newdata, stemp, strlen(stemp)); port_newdata += strlen(stemp); if (eport != 0) { *port_newdata = '-'; port_newdata++; /* Copy into IP packet */ sprintf(stemp, "%d", ntohs(ealias)); memcpy(port_newdata, stemp, strlen(stemp)); port_newdata += strlen(stemp); } *port_newdata = ';'; port_newdata++; } state++; break; } if (state > 3) { break; } } port_data += i; port_dlen -= i; } if (!pkt_updated) return (-1); memcpy(port_newdata, port_data, port_dlen); port_newdata += port_dlen; *port_newdata = '\0'; /* Create new packet */ new_dlen = port_newdata - newdata; memcpy(data, newdata, new_dlen); SetAckModified(lnk); tc = (struct tcphdr *)ip_next(pip); delta = GetDeltaSeqOut(tc->th_seq, lnk); AddSeq(lnk, delta + new_dlen - dlen, pip->ip_hl, pip->ip_len, tc->th_seq, tc->th_off); new_len = htons(hlen + new_dlen); DifferentialChecksum(&pip->ip_sum, &new_len, &pip->ip_len, 1); pip->ip_len = new_len; tc->th_sum = 0; #ifdef _KERNEL tc->th_x2 = 1; #else tc->th_sum = TcpChecksum(pip); #endif return (0); }
static void AliasHandlePptpOut(struct libalias *la, struct ip *pip, /* IP packet to examine/patch */ struct alias_link *lnk) { /* The PPTP control link */ struct alias_link *pptp_lnk; PptpCallId cptr; PptpCode codes; u_int16_t ctl_type; /* control message type */ struct tcphdr *tc; /* Verify valid PPTP control message */ if ((cptr = AliasVerifyPptp(pip, &ctl_type)) == NULL) return; /* Modify certain PPTP messages */ switch (ctl_type) { case PPTP_OutCallRequest: case PPTP_OutCallReply: case PPTP_InCallRequest: case PPTP_InCallReply: /* * Establish PPTP link for address and Call ID found in * control message. */ pptp_lnk = AddPptp(la, GetOriginalAddress(lnk), GetDestAddress(lnk), GetAliasAddress(lnk), cptr->cid1); break; case PPTP_CallClearRequest: case PPTP_CallDiscNotify: /* * Find PPTP link for address and Call ID found in control * message. */ pptp_lnk = FindPptpOutByCallId(la, GetOriginalAddress(lnk), GetDestAddress(lnk), cptr->cid1); break; default: return; } if (pptp_lnk != NULL) { int accumulate = cptr->cid1; /* alias the Call Id */ cptr->cid1 = GetAliasPort(pptp_lnk); /* Compute TCP checksum for revised packet */ tc = (struct tcphdr *)ip_next(pip); accumulate -= cptr->cid1; ADJUST_CHECKSUM(accumulate, tc->th_sum); switch (ctl_type) { case PPTP_OutCallReply: case PPTP_InCallReply: codes = (PptpCode) (cptr + 1); if (codes->resCode == 1) /* Connection * established, */ SetDestCallId(pptp_lnk, /* note the Peer's Call * ID. */ cptr->cid2); else SetExpire(pptp_lnk, 0); /* Connection refused. */ break; case PPTP_CallDiscNotify: /* Connection closed. */ SetExpire(pptp_lnk, 0); break; } } }
static int UdpAliasIn(struct libalias *la, struct ip *pip) { struct udphdr *ud; struct alias_link *lnk; LIBALIAS_LOCK_ASSERT(la); ud = (struct udphdr *)ip_next(pip); lnk = FindUdpTcpIn(la, pip->ip_src, pip->ip_dst, ud->uh_sport, ud->uh_dport, IPPROTO_UDP, !(la->packetAliasMode & PKT_ALIAS_PROXY_ONLY)); if (lnk != NULL) { struct in_addr alias_address; struct in_addr original_address; struct in_addr proxy_address; u_short alias_port; u_short proxy_port; int accumulate; int error; struct alias_data ad = { .lnk = lnk, .oaddr = &original_address, .aaddr = &alias_address, .aport = &alias_port, .sport = &ud->uh_sport, .dport = &ud->uh_dport, .maxpktsize = 0 }; alias_address = GetAliasAddress(lnk); original_address = GetOriginalAddress(lnk); proxy_address = GetProxyAddress(lnk); alias_port = ud->uh_dport; ud->uh_dport = GetOriginalPort(lnk); proxy_port = GetProxyPort(lnk); /* Walk out chain. */ error = find_handler(IN, UDP, la, pip, &ad); /* If we cannot figure out the packet, ignore it. */ if (error < 0) return (PKT_ALIAS_IGNORED); /* If UDP checksum is not zero, then adjust since destination port */ /* is being unaliased and destination address is being altered. */ if (ud->uh_sum != 0) { accumulate = alias_port; accumulate -= ud->uh_dport; accumulate += twowords(&alias_address); accumulate -= twowords(&original_address); /* If this is a proxy packet, modify checksum because of source change.*/ if (proxy_port != 0) { accumulate += ud->uh_sport; accumulate -= proxy_port; } if (proxy_address.s_addr != 0) { accumulate += twowords(&pip->ip_src); accumulate -= twowords(&proxy_address); } ADJUST_CHECKSUM(accumulate, ud->uh_sum); } /* XXX: Could the two if's below be concatenated to one ? */ /* Restore source port and/or address in case of proxying*/ if (proxy_port != 0) ud->uh_sport = proxy_port; if (proxy_address.s_addr != 0) { DifferentialChecksum(&pip->ip_sum, &proxy_address, &pip->ip_src, 2); pip->ip_src = proxy_address; } /* Restore original IP address */ DifferentialChecksum(&pip->ip_sum, &original_address, &pip->ip_dst, 2); pip->ip_dst = original_address; return (PKT_ALIAS_OK); } return (PKT_ALIAS_IGNORED); } static int UdpAliasOut(struct libalias *la, struct ip *pip, int maxpacketsize, int create) { struct udphdr *ud; struct alias_link *lnk; struct in_addr dest_address; struct in_addr proxy_server_address; u_short dest_port; u_short proxy_server_port; int proxy_type; int error; LIBALIAS_LOCK_ASSERT(la); /* Return if proxy-only mode is enabled and not proxyrule found.*/ ud = (struct udphdr *)ip_next(pip); proxy_type = ProxyCheck(la, &proxy_server_address, &proxy_server_port, pip->ip_src, pip->ip_dst, ud->uh_dport, pip->ip_p); if (proxy_type == 0 && (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY)) return (PKT_ALIAS_OK); /* If this is a transparent proxy, save original destination, * then alter the destination and adjust checksums */ dest_port = ud->uh_dport; dest_address = pip->ip_dst; if (proxy_type != 0) { int accumulate; accumulate = twowords(&pip->ip_dst); accumulate -= twowords(&proxy_server_address); ADJUST_CHECKSUM(accumulate, pip->ip_sum); if (ud->uh_sum != 0) { accumulate = twowords(&pip->ip_dst); accumulate -= twowords(&proxy_server_address); accumulate += ud->uh_dport; accumulate -= proxy_server_port; ADJUST_CHECKSUM(accumulate, ud->uh_sum); } pip->ip_dst = proxy_server_address; ud->uh_dport = proxy_server_port; } lnk = FindUdpTcpOut(la, pip->ip_src, pip->ip_dst, ud->uh_sport, ud->uh_dport, IPPROTO_UDP, create); if (lnk != NULL) { u_short alias_port; struct in_addr alias_address; struct alias_data ad = { .lnk = lnk, .oaddr = NULL, .aaddr = &alias_address, .aport = &alias_port, .sport = &ud->uh_sport, .dport = &ud->uh_dport, .maxpktsize = 0 }; /* Save original destination address, if this is a proxy packet. * Also modify packet to include destination encoding. This may * change the size of IP header. */ if (proxy_type != 0) { SetProxyPort(lnk, dest_port); SetProxyAddress(lnk, dest_address); ProxyModify(la, lnk, pip, maxpacketsize, proxy_type); ud = (struct udphdr *)ip_next(pip); } alias_address = GetAliasAddress(lnk); alias_port = GetAliasPort(lnk); /* Walk out chain. */ error = find_handler(OUT, UDP, la, pip, &ad); /* If UDP checksum is not zero, adjust since source port is */ /* being aliased and source address is being altered */ if (ud->uh_sum != 0) { int accumulate; accumulate = ud->uh_sport; accumulate -= alias_port; accumulate += twowords(&pip->ip_src); accumulate -= twowords(&alias_address); ADJUST_CHECKSUM(accumulate, ud->uh_sum); } /* Put alias port in UDP header */ ud->uh_sport = alias_port; /* Change source address */ DifferentialChecksum(&pip->ip_sum, &alias_address, &pip->ip_src, 2); pip->ip_src = alias_address; return (PKT_ALIAS_OK); } return (PKT_ALIAS_IGNORED); } static int TcpAliasIn(struct libalias *la, struct ip *pip) { struct tcphdr *tc; struct alias_link *lnk; LIBALIAS_LOCK_ASSERT(la); tc = (struct tcphdr *)ip_next(pip); lnk = FindUdpTcpIn(la, pip->ip_src, pip->ip_dst, tc->th_sport, tc->th_dport, IPPROTO_TCP, !(la->packetAliasMode & PKT_ALIAS_PROXY_ONLY)); if (lnk != NULL) { struct in_addr alias_address; struct in_addr original_address; struct in_addr proxy_address; u_short alias_port; u_short proxy_port; int accumulate, error; /* * The init of MANY vars is a bit below, but aliashandlepptpin * seems to need the destination port that came within the * packet and not the original one looks below [*]. */ struct alias_data ad = { .lnk = lnk, .oaddr = NULL, .aaddr = NULL, .aport = NULL, .sport = &tc->th_sport, .dport = &tc->th_dport, .maxpktsize = 0 }; /* Walk out chain. */ error = find_handler(IN, TCP, la, pip, &ad); alias_address = GetAliasAddress(lnk); original_address = GetOriginalAddress(lnk); proxy_address = GetProxyAddress(lnk); alias_port = tc->th_dport; tc->th_dport = GetOriginalPort(lnk); proxy_port = GetProxyPort(lnk); /* * Look above, if anyone is going to add find_handler AFTER * this aliashandlepptpin/point, please redo alias_data too. * Uncommenting the piece here below should be enough. */ #if 0 struct alias_data ad = { .lnk = lnk, .oaddr = &original_address, .aaddr = &alias_address, .aport = &alias_port, .sport = &ud->uh_sport, .dport = &ud->uh_dport, .maxpktsize = 0 }; /* Walk out chain. */ error = find_handler(la, pip, &ad); if (error == EHDNOF) printf("Protocol handler not found\n"); #endif /* Adjust TCP checksum since destination port is being unaliased */ /* and destination port is being altered. */ accumulate = alias_port; accumulate -= tc->th_dport; accumulate += twowords(&alias_address); accumulate -= twowords(&original_address); /* If this is a proxy, then modify the TCP source port and checksum accumulation */ if (proxy_port != 0) { accumulate += tc->th_sport; tc->th_sport = proxy_port; accumulate -= tc->th_sport; accumulate += twowords(&pip->ip_src); accumulate -= twowords(&proxy_address); } /* See if ACK number needs to be modified */ if (GetAckModified(lnk) == 1) { int delta; tc = (struct tcphdr *)ip_next(pip); delta = GetDeltaAckIn(tc->th_ack, lnk); if (delta != 0) { accumulate += twowords(&tc->th_ack); tc->th_ack = htonl(ntohl(tc->th_ack) - delta); accumulate -= twowords(&tc->th_ack); } } ADJUST_CHECKSUM(accumulate, tc->th_sum); /* Restore original IP address */ accumulate = twowords(&pip->ip_dst); pip->ip_dst = original_address; accumulate -= twowords(&pip->ip_dst); /* If this is a transparent proxy packet, then modify the source address */ if (proxy_address.s_addr != 0) { accumulate += twowords(&pip->ip_src); pip->ip_src = proxy_address; accumulate -= twowords(&pip->ip_src); } ADJUST_CHECKSUM(accumulate, pip->ip_sum); /* Monitor TCP connection state */ tc = (struct tcphdr *)ip_next(pip); TcpMonitorIn(tc->th_flags, lnk); return (PKT_ALIAS_OK); } return (PKT_ALIAS_IGNORED); } static int TcpAliasOut(struct libalias *la, struct ip *pip, int maxpacketsize, int create) { int proxy_type, error; u_short dest_port; u_short proxy_server_port; struct in_addr dest_address; struct in_addr proxy_server_address; struct tcphdr *tc; struct alias_link *lnk; LIBALIAS_LOCK_ASSERT(la); tc = (struct tcphdr *)ip_next(pip); if (create) proxy_type = ProxyCheck(la, &proxy_server_address, &proxy_server_port, pip->ip_src, pip->ip_dst, tc->th_dport, pip->ip_p); else proxy_type = 0; if (proxy_type == 0 && (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY)) return (PKT_ALIAS_OK); /* If this is a transparent proxy, save original destination, then alter the destination and adjust checksums */ dest_port = tc->th_dport; dest_address = pip->ip_dst; if (proxy_type != 0) { int accumulate; accumulate = tc->th_dport; tc->th_dport = proxy_server_port; accumulate -= tc->th_dport; accumulate += twowords(&pip->ip_dst); accumulate -= twowords(&proxy_server_address); ADJUST_CHECKSUM(accumulate, tc->th_sum); accumulate = twowords(&pip->ip_dst); pip->ip_dst = proxy_server_address; accumulate -= twowords(&pip->ip_dst); ADJUST_CHECKSUM(accumulate, pip->ip_sum); } lnk = FindUdpTcpOut(la, pip->ip_src, pip->ip_dst, tc->th_sport, tc->th_dport, IPPROTO_TCP, create); if (lnk == NULL) return (PKT_ALIAS_IGNORED); if (lnk != NULL) { u_short alias_port; struct in_addr alias_address; int accumulate; struct alias_data ad = { .lnk = lnk, .oaddr = NULL, .aaddr = &alias_address, .aport = &alias_port, .sport = &tc->th_sport, .dport = &tc->th_dport, .maxpktsize = maxpacketsize }; /* Save original destination address, if this is a proxy packet. Also modify packet to include destination encoding. This may change the size of IP header. */ if (proxy_type != 0) { SetProxyPort(lnk, dest_port); SetProxyAddress(lnk, dest_address); ProxyModify(la, lnk, pip, maxpacketsize, proxy_type); tc = (struct tcphdr *)ip_next(pip); } /* Get alias address and port */ alias_port = GetAliasPort(lnk); alias_address = GetAliasAddress(lnk); /* Monitor TCP connection state */ tc = (struct tcphdr *)ip_next(pip); TcpMonitorOut(tc->th_flags, lnk); /* Walk out chain. */ error = find_handler(OUT, TCP, la, pip, &ad); /* Adjust TCP checksum since source port is being aliased */ /* and source address is being altered */ accumulate = tc->th_sport; tc->th_sport = alias_port; accumulate -= tc->th_sport; accumulate += twowords(&pip->ip_src); accumulate -= twowords(&alias_address); /* Modify sequence number if necessary */ if (GetAckModified(lnk) == 1) { int delta; tc = (struct tcphdr *)ip_next(pip); delta = GetDeltaSeqOut(tc->th_seq, lnk); if (delta != 0) { accumulate += twowords(&tc->th_seq); tc->th_seq = htonl(ntohl(tc->th_seq) + delta); accumulate -= twowords(&tc->th_seq); } } ADJUST_CHECKSUM(accumulate, tc->th_sum); /* Change source address */ accumulate = twowords(&pip->ip_src); pip->ip_src = alias_address; accumulate -= twowords(&pip->ip_src); ADJUST_CHECKSUM(accumulate, pip->ip_sum); return (PKT_ALIAS_OK); } return (PKT_ALIAS_IGNORED); } /* Fragment Handling FragmentIn() FragmentOut() The packet aliasing module has a limited ability for handling IP fragments. If the ICMP, TCP or UDP header is in the first fragment received, then the ID number of the IP packet is saved, and other fragments are identified according to their ID number and IP address they were sent from. Pointers to unresolved fragments can also be saved and recalled when a header fragment is seen. */ /* Local prototypes */ static int FragmentIn(struct libalias *la, struct in_addr ip_src, struct in_addr *ip_dst, u_short ip_id, u_short *ip_sum); static int FragmentOut(struct libalias *, struct in_addr *ip_src, u_short *ip_sum); static int FragmentIn(struct libalias *la, struct in_addr ip_src, struct in_addr *ip_dst, u_short ip_id, u_short *ip_sum) { struct alias_link *lnk; LIBALIAS_LOCK_ASSERT(la); lnk = FindFragmentIn2(la, ip_src, *ip_dst, ip_id); if (lnk != NULL) { struct in_addr original_address; GetFragmentAddr(lnk, &original_address); DifferentialChecksum(ip_sum, &original_address, ip_dst, 2); *ip_dst = original_address; return (PKT_ALIAS_OK); } return (PKT_ALIAS_UNRESOLVED_FRAGMENT); } static int FragmentOut(struct libalias *la, struct in_addr *ip_src, u_short *ip_sum) { struct in_addr alias_address; LIBALIAS_LOCK_ASSERT(la); alias_address = FindAliasAddress(la, *ip_src); DifferentialChecksum(ip_sum, &alias_address, ip_src, 2); *ip_src = alias_address; return (PKT_ALIAS_OK); } /* Outside World Access PacketAliasSaveFragment() PacketAliasGetFragment() PacketAliasFragmentIn() PacketAliasIn() PacketAliasOut() PacketUnaliasOut() (prototypes in alias.h) */ int LibAliasSaveFragment(struct libalias *la, char *ptr) { int iresult; struct alias_link *lnk; struct ip *pip; LIBALIAS_LOCK(la); pip = (struct ip *)ptr; lnk = AddFragmentPtrLink(la, pip->ip_src, pip->ip_id); iresult = PKT_ALIAS_ERROR; if (lnk != NULL) { SetFragmentPtr(lnk, ptr); iresult = PKT_ALIAS_OK; } LIBALIAS_UNLOCK(la); return (iresult); } char * LibAliasGetFragment(struct libalias *la, char *ptr) { struct alias_link *lnk; char *fptr; struct ip *pip; LIBALIAS_LOCK(la); pip = (struct ip *)ptr; lnk = FindFragmentPtr(la, pip->ip_src, pip->ip_id); if (lnk != NULL) { GetFragmentPtr(lnk, &fptr); SetFragmentPtr(lnk, NULL); SetExpire(lnk, 0); /* Deletes link */ } else fptr = NULL; LIBALIAS_UNLOCK(la); return (fptr); } void LibAliasFragmentIn(struct libalias *la, char *ptr, /* Points to correctly * de-aliased header * fragment */ char *ptr_fragment /* Points to fragment which must be * de-aliased */ ) { struct ip *pip; struct ip *fpip; LIBALIAS_LOCK(la); (void)la; pip = (struct ip *)ptr; fpip = (struct ip *)ptr_fragment; DifferentialChecksum(&fpip->ip_sum, &pip->ip_dst, &fpip->ip_dst, 2); fpip->ip_dst = pip->ip_dst; LIBALIAS_UNLOCK(la); } /* Local prototypes */ static int LibAliasOutLocked(struct libalias *la, char *ptr, int maxpacketsize, int create); static int LibAliasInLocked(struct libalias *la, char *ptr, int maxpacketsize); int LibAliasIn(struct libalias *la, char *ptr, int maxpacketsize) { int res; LIBALIAS_LOCK(la); res = LibAliasInLocked(la, ptr, maxpacketsize); LIBALIAS_UNLOCK(la); return (res); }
static int IcmpAliasIn2(struct libalias *la, struct ip *pip) { LIBALIAS_LOCK_ASSERT(la); /* Alias incoming ICMP error messages containing IP header and first 64 bits of datagram. */ struct ip *ip; struct icmp *ic, *ic2; struct udphdr *ud; struct tcphdr *tc; struct alias_link *lnk; ic = (struct icmp *)ip_next(pip); ip = &ic->icmp_ip; ud = (struct udphdr *)ip_next(ip); tc = (struct tcphdr *)ip_next(ip); ic2 = (struct icmp *)ip_next(ip); if (ip->ip_p == IPPROTO_UDP) lnk = FindUdpTcpIn(la, ip->ip_dst, ip->ip_src, ud->uh_dport, ud->uh_sport, IPPROTO_UDP, 0); else if (ip->ip_p == IPPROTO_TCP) lnk = FindUdpTcpIn(la, ip->ip_dst, ip->ip_src, tc->th_dport, tc->th_sport, IPPROTO_TCP, 0); else if (ip->ip_p == IPPROTO_ICMP) { if (ic2->icmp_type == ICMP_ECHO || ic2->icmp_type == ICMP_TSTAMP) lnk = FindIcmpIn(la, ip->ip_dst, ip->ip_src, ic2->icmp_id, 0); else lnk = NULL; } else lnk = NULL; if (lnk != NULL) { if (ip->ip_p == IPPROTO_UDP || ip->ip_p == IPPROTO_TCP) { int accumulate, accumulate2; struct in_addr original_address; u_short original_port; original_address = GetOriginalAddress(lnk); original_port = GetOriginalPort(lnk); /* Adjust ICMP checksum */ accumulate = twowords(&ip->ip_src); accumulate -= twowords(&original_address); accumulate += ud->uh_sport; accumulate -= original_port; accumulate2 = accumulate; accumulate2 += ip->ip_sum; ADJUST_CHECKSUM(accumulate, ip->ip_sum); accumulate2 -= ip->ip_sum; ADJUST_CHECKSUM(accumulate2, ic->icmp_cksum); /* Un-alias address in IP header */ DifferentialChecksum(&pip->ip_sum, &original_address, &pip->ip_dst, 2); pip->ip_dst = original_address; /* Un-alias address and port number of original IP packet fragment contained in ICMP data section */ ip->ip_src = original_address; ud->uh_sport = original_port; } else if (ip->ip_p == IPPROTO_ICMP) { int accumulate, accumulate2; struct in_addr original_address; u_short original_id; original_address = GetOriginalAddress(lnk); original_id = GetOriginalPort(lnk); /* Adjust ICMP checksum */ accumulate = twowords(&ip->ip_src); accumulate -= twowords(&original_address); accumulate += ic2->icmp_id; accumulate -= original_id; accumulate2 = accumulate; accumulate2 += ip->ip_sum; ADJUST_CHECKSUM(accumulate, ip->ip_sum); accumulate2 -= ip->ip_sum; ADJUST_CHECKSUM(accumulate2, ic->icmp_cksum); /* Un-alias address in IP header */ DifferentialChecksum(&pip->ip_sum, &original_address, &pip->ip_dst, 2); pip->ip_dst = original_address; /* Un-alias address of original IP packet and sequence number of embedded ICMP datagram */ ip->ip_src = original_address; ic2->icmp_id = original_id; } return (PKT_ALIAS_OK); } return (PKT_ALIAS_IGNORED); }
int LibAliasUnaliasOut(struct libalias *la, char *ptr, /* valid IP packet */ int maxpacketsize /* for error checking */ ) { struct ip *pip; struct icmp *ic; struct udphdr *ud; struct tcphdr *tc; struct alias_link *lnk; int iresult = PKT_ALIAS_IGNORED; LIBALIAS_LOCK(la); pip = (struct ip *)ptr; /* Defense against mangled packets */ if (ntohs(pip->ip_len) > maxpacketsize || (pip->ip_hl << 2) > maxpacketsize) goto getout; ud = (struct udphdr *)ip_next(pip); tc = (struct tcphdr *)ip_next(pip); ic = (struct icmp *)ip_next(pip); /* Find a link */ if (pip->ip_p == IPPROTO_UDP) lnk = FindUdpTcpIn(la, pip->ip_dst, pip->ip_src, ud->uh_dport, ud->uh_sport, IPPROTO_UDP, 0); else if (pip->ip_p == IPPROTO_TCP) lnk = FindUdpTcpIn(la, pip->ip_dst, pip->ip_src, tc->th_dport, tc->th_sport, IPPROTO_TCP, 0); else if (pip->ip_p == IPPROTO_ICMP) lnk = FindIcmpIn(la, pip->ip_dst, pip->ip_src, ic->icmp_id, 0); else lnk = NULL; /* Change it from an aliased packet to an unaliased packet */ if (lnk != NULL) { if (pip->ip_p == IPPROTO_UDP || pip->ip_p == IPPROTO_TCP) { int accumulate; struct in_addr original_address; u_short original_port; original_address = GetOriginalAddress(lnk); original_port = GetOriginalPort(lnk); /* Adjust TCP/UDP checksum */ accumulate = twowords(&pip->ip_src); accumulate -= twowords(&original_address); if (pip->ip_p == IPPROTO_UDP) { accumulate += ud->uh_sport; accumulate -= original_port; ADJUST_CHECKSUM(accumulate, ud->uh_sum); } else { accumulate += tc->th_sport; accumulate -= original_port; ADJUST_CHECKSUM(accumulate, tc->th_sum); } /* Adjust IP checksum */ DifferentialChecksum(&pip->ip_sum, &original_address, &pip->ip_src, 2); /* Un-alias source address and port number */ pip->ip_src = original_address; if (pip->ip_p == IPPROTO_UDP) ud->uh_sport = original_port; else tc->th_sport = original_port; iresult = PKT_ALIAS_OK; } else if (pip->ip_p == IPPROTO_ICMP) { int accumulate; struct in_addr original_address; u_short original_id; original_address = GetOriginalAddress(lnk); original_id = GetOriginalPort(lnk); /* Adjust ICMP checksum */ accumulate = twowords(&pip->ip_src); accumulate -= twowords(&original_address); accumulate += ic->icmp_id; accumulate -= original_id; ADJUST_CHECKSUM(accumulate, ic->icmp_cksum); /* Adjust IP checksum */ DifferentialChecksum(&pip->ip_sum, &original_address, &pip->ip_src, 2); /* Un-alias source address and port number */ pip->ip_src = original_address; ic->icmp_id = original_id; iresult = PKT_ALIAS_OK; } } getout: LIBALIAS_UNLOCK(la); return (iresult); }
VOID CALLBACK LdrDllNotification(ULONG NotificationReason, const LDR_DLL_NOTIFICATION_DATA* NotificationData, PVOID Context) { DWORD dwSaveErrCode = GetLastError(); wchar_t szModule[MAX_PATH*2] = L""; HMODULE hModule; BOOL bMainThread = (GetCurrentThreadId() == gnHookMainThreadId); const UNICODE_STRING* FullDllName; //The full path name of the DLL module. const UNICODE_STRING* BaseDllName; //The base file name of the DLL module. switch (NotificationReason) { case LDR_DLL_NOTIFICATION_REASON_LOADED: FullDllName = NotificationData->Loaded.FullDllName; BaseDllName = NotificationData->Loaded.BaseDllName; hModule = (HMODULE)NotificationData->Loaded.DllBase; break; case LDR_DLL_NOTIFICATION_REASON_UNLOADED: FullDllName = NotificationData->Unloaded.FullDllName; BaseDllName = NotificationData->Unloaded.BaseDllName; hModule = (HMODULE)NotificationData->Unloaded.DllBase; break; default: return; } if (FullDllName && FullDllName->Buffer) memmove(szModule, FullDllName->Buffer, min(sizeof(szModule)-2,FullDllName->Length)); else if (BaseDllName && BaseDllName->Buffer) memmove(szModule, BaseDllName->Buffer, min(sizeof(szModule)-2,BaseDllName->Length)); #ifdef _DEBUG wchar_t szDbgInfo[MAX_PATH*3]; _wsprintf(szDbgInfo, SKIPLEN(countof(szDbgInfo)) L"ConEmuHk: Ldr(%s) " WIN3264TEST(L"0x%08X",L"0x%08X%08X") L" '%s'\n", (NotificationReason==LDR_DLL_NOTIFICATION_REASON_LOADED) ? L"Loaded" : L"Unload", WIN3264WSPRINT(hModule), szModule); DebugString(szDbgInfo); #endif switch (NotificationReason) { case LDR_DLL_NOTIFICATION_REASON_LOADED: if (PrepareNewModule(hModule, NULL, szModule, TRUE, TRUE)) { HookItem* ph = NULL; GetOriginalAddress((LPVOID)OnLoadLibraryW, HOOK_FN_ID(LoadLibraryW), NULL, &ph, true); if (ph && ph->PostCallBack) { SETARGS1(&hModule,szModule); ph->PostCallBack(&args); } } break; case LDR_DLL_NOTIFICATION_REASON_UNLOADED: UnprepareModule(hModule, szModule, 0); UnprepareModule(hModule, szModule, 2); break; } SetLastError(dwSaveErrCode); }
static int TcpAliasIn(struct libalias *la, struct ip *pip) { struct tcphdr *tc; struct alias_link *lnk; LIBALIAS_LOCK_ASSERT(la); tc = (struct tcphdr *)ip_next(pip); lnk = FindUdpTcpIn(la, pip->ip_src, pip->ip_dst, tc->th_sport, tc->th_dport, IPPROTO_TCP, !(la->packetAliasMode & PKT_ALIAS_PROXY_ONLY)); if (lnk != NULL) { struct in_addr alias_address; struct in_addr original_address; struct in_addr proxy_address; u_short alias_port; u_short proxy_port; int accumulate, error; /* * The init of MANY vars is a bit below, but aliashandlepptpin * seems to need the destination port that came within the * packet and not the original one looks below [*]. */ struct alias_data ad; ad.lnk = lnk; ad.oaddr = NULL; ad.aaddr = NULL; ad.aport = NULL; ad.sport = &tc->th_sport; ad.dport = &tc->th_dport; ad.maxpktsize = 0; /* Walk out chain. */ error = find_handler(IN, TCP, la, pip, &ad); alias_address = GetAliasAddress(lnk); original_address = GetOriginalAddress(lnk); proxy_address = GetProxyAddress(lnk); alias_port = tc->th_dport; tc->th_dport = GetOriginalPort(lnk); proxy_port = GetProxyPort(lnk); /* * Look above, if anyone is going to add find_handler AFTER * this aliashandlepptpin/point, please redo alias_data too. * Uncommenting the piece here below should be enough. */ #if 0 struct alias_data ad = { .lnk = lnk, .oaddr = &original_address, .aaddr = &alias_address, .aport = &alias_port, .sport = &ud->uh_sport, .dport = &ud->uh_dport, .maxpktsize = 0 }; /* Walk out chain. */ error = find_handler(la, pip, &ad); if (error == EHDNOF) printf("Protocol handler not found\n"); #endif /* Adjust TCP checksum since destination port is being unaliased */ /* and destination port is being altered. */ accumulate = alias_port; accumulate -= tc->th_dport; accumulate += twowords(&alias_address); accumulate -= twowords(&original_address); /* If this is a proxy, then modify the TCP source port and checksum accumulation */ if (proxy_port != 0) { accumulate += tc->th_sport; tc->th_sport = proxy_port; accumulate -= tc->th_sport; accumulate += twowords(&pip->ip_src); accumulate -= twowords(&proxy_address); } /* See if ACK number needs to be modified */ if (GetAckModified(lnk) == 1) { int delta; delta = GetDeltaAckIn(pip, lnk); if (delta != 0) { accumulate += twowords(&tc->th_ack); tc->th_ack = htonl(ntohl(tc->th_ack) - delta); accumulate -= twowords(&tc->th_ack); } } ADJUST_CHECKSUM(accumulate, tc->th_sum); /* Restore original IP address */ accumulate = twowords(&pip->ip_dst); pip->ip_dst = original_address; accumulate -= twowords(&pip->ip_dst); /* If this is a transparent proxy packet, then modify the source address */ if (proxy_address.s_addr != 0) { accumulate += twowords(&pip->ip_src); pip->ip_src = proxy_address; accumulate -= twowords(&pip->ip_src); } ADJUST_CHECKSUM(accumulate, pip->ip_sum); /* Monitor TCP connection state */ TcpMonitorIn(pip, lnk); return (PKT_ALIAS_OK); } return (PKT_ALIAS_IGNORED); } static int TcpAliasOut(struct libalias *la, struct ip *pip, int maxpacketsize, int create) { int proxy_type, error; u_short dest_port; u_short proxy_server_port; struct in_addr dest_address; struct in_addr proxy_server_address; struct tcphdr *tc; struct alias_link *lnk; LIBALIAS_LOCK_ASSERT(la); tc = (struct tcphdr *)ip_next(pip); if (create) proxy_type = ProxyCheck(la, pip, &proxy_server_address, &proxy_server_port); else proxy_type = 0; if (proxy_type == 0 && (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY)) return (PKT_ALIAS_OK); /* If this is a transparent proxy, save original destination, then alter the destination and adjust checksums */ dest_port = tc->th_dport; dest_address = pip->ip_dst; if (proxy_type != 0) { int accumulate; accumulate = tc->th_dport; tc->th_dport = proxy_server_port; accumulate -= tc->th_dport; accumulate += twowords(&pip->ip_dst); accumulate -= twowords(&proxy_server_address); ADJUST_CHECKSUM(accumulate, tc->th_sum); accumulate = twowords(&pip->ip_dst); pip->ip_dst = proxy_server_address; accumulate -= twowords(&pip->ip_dst); ADJUST_CHECKSUM(accumulate, pip->ip_sum); } lnk = FindUdpTcpOut(la, pip->ip_src, pip->ip_dst, tc->th_sport, tc->th_dport, IPPROTO_TCP, create); if (lnk == NULL) return (PKT_ALIAS_IGNORED); if (lnk != NULL) { u_short alias_port; struct in_addr alias_address; int accumulate; struct alias_data ad; ad.lnk = lnk; ad.oaddr = NULL; ad.aaddr = &alias_address; ad.aport = &alias_port; ad.sport = &tc->th_sport; ad.dport = &tc->th_dport; ad.maxpktsize = maxpacketsize; /* Save original destination address, if this is a proxy packet. Also modify packet to include destination encoding. This may change the size of IP header. */ if (proxy_type != 0) { SetProxyPort(lnk, dest_port); SetProxyAddress(lnk, dest_address); ProxyModify(la, lnk, pip, maxpacketsize, proxy_type); tc = (struct tcphdr *)ip_next(pip); } /* Get alias address and port */ alias_port = GetAliasPort(lnk); alias_address = GetAliasAddress(lnk); /* Monitor TCP connection state */ TcpMonitorOut(pip, lnk); /* Walk out chain. */ error = find_handler(OUT, TCP, la, pip, &ad); /* Adjust TCP checksum since source port is being aliased */ /* and source address is being altered */ accumulate = tc->th_sport; tc->th_sport = alias_port; accumulate -= tc->th_sport; accumulate += twowords(&pip->ip_src); accumulate -= twowords(&alias_address); /* Modify sequence number if necessary */ if (GetAckModified(lnk) == 1) { int delta; delta = GetDeltaSeqOut(pip, lnk); if (delta != 0) { accumulate += twowords(&tc->th_seq); tc->th_seq = htonl(ntohl(tc->th_seq) + delta); accumulate -= twowords(&tc->th_seq); } } ADJUST_CHECKSUM(accumulate, tc->th_sum); /* Change source address */ accumulate = twowords(&pip->ip_src); pip->ip_src = alias_address; accumulate -= twowords(&pip->ip_src); ADJUST_CHECKSUM(accumulate, pip->ip_sum); return (PKT_ALIAS_OK); } return (PKT_ALIAS_IGNORED); }
static int UdpAliasIn(struct libalias *la, struct ip *pip) { struct udphdr *ud; struct alias_link *lnk; LIBALIAS_LOCK_ASSERT(la); /* Return if proxy-only mode is enabled */ if (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY) return (PKT_ALIAS_OK); ud = (struct udphdr *)ip_next(pip); lnk = FindUdpTcpIn(la, pip->ip_src, pip->ip_dst, ud->uh_sport, ud->uh_dport, IPPROTO_UDP, 1); if (lnk != NULL) { struct in_addr alias_address; struct in_addr original_address; u_short alias_port; int accumulate; int r = 0, error; struct alias_data ad; ad.lnk = lnk; ad.oaddr = &original_address; ad.aaddr = &alias_address; ad.aport = &alias_port; ad.sport = &ud->uh_sport; ad.dport = &ud->uh_dport; ad.maxpktsize = 0; alias_address = GetAliasAddress(lnk); original_address = GetOriginalAddress(lnk); alias_port = ud->uh_dport; ud->uh_dport = GetOriginalPort(lnk); /* Walk out chain. */ error = find_handler(IN, UDP, la, pip, &ad); /* If UDP checksum is not zero, then adjust since destination port */ /* is being unaliased and destination address is being altered. */ if (ud->uh_sum != 0) { accumulate = alias_port; accumulate -= ud->uh_dport; accumulate += twowords(&alias_address); accumulate -= twowords(&original_address); ADJUST_CHECKSUM(accumulate, ud->uh_sum); } /* Restore original IP address */ DifferentialChecksum(&pip->ip_sum, &original_address, &pip->ip_dst, 2); pip->ip_dst = original_address; /* * If we cannot figure out the packet, ignore it. */ if (r < 0) return (PKT_ALIAS_IGNORED); else return (PKT_ALIAS_OK); } return (PKT_ALIAS_IGNORED); }
static int TcpAliasIn(struct ip *pip) { struct tcphdr *tc; struct alias_link *link; tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2)); link = FindUdpTcpIn(pip->ip_src, pip->ip_dst, tc->th_sport, tc->th_dport, IPPROTO_TCP, !(packetAliasMode & PKT_ALIAS_PROXY_ONLY)); if (link != NULL) { struct in_addr alias_address; struct in_addr original_address; struct in_addr proxy_address; u_short alias_port; u_short proxy_port; int accumulate; u_short *sptr; /* Special processing for IP encoding protocols */ if (ntohs(tc->th_dport) == PPTP_CONTROL_PORT_NUMBER || ntohs(tc->th_sport) == PPTP_CONTROL_PORT_NUMBER) AliasHandlePptpIn(pip, link); alias_address = GetAliasAddress(link); original_address = GetOriginalAddress(link); proxy_address = GetProxyAddress(link); alias_port = tc->th_dport; tc->th_dport = GetOriginalPort(link); proxy_port = GetProxyPort(link); /* Adjust TCP checksum since destination port is being unaliased */ /* and destination port is being altered. */ accumulate = alias_port; accumulate -= tc->th_dport; sptr = (u_short *) &alias_address; accumulate += *sptr++; accumulate += *sptr; sptr = (u_short *) &original_address; accumulate -= *sptr++; accumulate -= *sptr; /* If this is a proxy, then modify the TCP source port and checksum accumulation */ if (proxy_port != 0) { accumulate += tc->th_sport; tc->th_sport = proxy_port; accumulate -= tc->th_sport; sptr = (u_short *) &pip->ip_src; accumulate += *sptr++; accumulate += *sptr; sptr = (u_short *) &proxy_address; accumulate -= *sptr++; accumulate -= *sptr; } /* See if ACK number needs to be modified */ if (GetAckModified(link) == 1) { int delta; delta = GetDeltaAckIn(pip, link); if (delta != 0) { sptr = (u_short *) &tc->th_ack; accumulate += *sptr++; accumulate += *sptr; tc->th_ack = htonl(ntohl(tc->th_ack) - delta); sptr = (u_short *) &tc->th_ack; accumulate -= *sptr++; accumulate -= *sptr; } } ADJUST_CHECKSUM(accumulate, tc->th_sum); /* Restore original IP address */ sptr = (u_short *) &pip->ip_dst; accumulate = *sptr++; accumulate += *sptr; pip->ip_dst = original_address; sptr = (u_short *) &pip->ip_dst; accumulate -= *sptr++; accumulate -= *sptr; /* If this is a transparent proxy packet, then modify the source address */ if (proxy_address.s_addr != 0) { sptr = (u_short *) &pip->ip_src; accumulate += *sptr++; accumulate += *sptr; pip->ip_src = proxy_address; sptr = (u_short *) &pip->ip_src; accumulate -= *sptr++; accumulate -= *sptr; } ADJUST_CHECKSUM(accumulate, pip->ip_sum); /* Monitor TCP connection state */ TcpMonitorIn(pip, link); return(PKT_ALIAS_OK); } return(PKT_ALIAS_IGNORED); }
static int UdpAliasIn(struct ip *pip) { struct udphdr *ud; struct alias_link *link; /* Return if proxy-only mode is enabled */ if (packetAliasMode & PKT_ALIAS_PROXY_ONLY) return PKT_ALIAS_OK; ud = (struct udphdr *) ((char *) pip + (pip->ip_hl << 2)); link = FindUdpTcpIn(pip->ip_src, pip->ip_dst, ud->uh_sport, ud->uh_dport, IPPROTO_UDP, 1); if (link != NULL) { struct in_addr alias_address; struct in_addr original_address; u_short alias_port; int accumulate; u_short *sptr; int r = 0; alias_address = GetAliasAddress(link); original_address = GetOriginalAddress(link); alias_port = ud->uh_dport; ud->uh_dport = GetOriginalPort(link); /* Special processing for IP encoding protocols */ if (ntohs(ud->uh_dport) == CUSEEME_PORT_NUMBER) AliasHandleCUSeeMeIn(pip, original_address); /* If NETBIOS Datagram, It should be alias address in UDP Data, too */ else if (ntohs(ud->uh_dport) == NETBIOS_DGM_PORT_NUMBER || ntohs(ud->uh_sport) == NETBIOS_DGM_PORT_NUMBER) r = AliasHandleUdpNbt(pip, link, &original_address, ud->uh_dport); else if (ntohs(ud->uh_dport) == NETBIOS_NS_PORT_NUMBER || ntohs(ud->uh_sport) == NETBIOS_NS_PORT_NUMBER) r = AliasHandleUdpNbtNS(pip, link, &alias_address, &alias_port, &original_address, &ud->uh_dport); /* If UDP checksum is not zero, then adjust since destination port */ /* is being unaliased and destination address is being altered. */ if (ud->uh_sum != 0) { accumulate = alias_port; accumulate -= ud->uh_dport; sptr = (u_short *) &alias_address; accumulate += *sptr++; accumulate += *sptr; sptr = (u_short *) &original_address; accumulate -= *sptr++; accumulate -= *sptr; ADJUST_CHECKSUM(accumulate, ud->uh_sum); } /* Restore original IP address */ DifferentialChecksum(&pip->ip_sum, (u_short *) &original_address, (u_short *) &pip->ip_dst, 2); pip->ip_dst = original_address; /* * If we cannot figure out the packet, ignore it. */ if (r < 0) return(PKT_ALIAS_IGNORED); else return(PKT_ALIAS_OK); } return(PKT_ALIAS_IGNORED); }
int PacketUnaliasOut(char *ptr, /* valid IP packet */ int maxpacketsize /* for error checking */ ) { struct ip *pip; struct icmp *ic; struct udphdr *ud; struct tcphdr *tc; struct alias_link *link; int iresult = PKT_ALIAS_IGNORED; pip = (struct ip *) ptr; /* Defense against mangled packets */ if (ntohs(pip->ip_len) > maxpacketsize || (pip->ip_hl<<2) > maxpacketsize) return(iresult); ud = (struct udphdr *) ((char *) pip + (pip->ip_hl << 2)); tc = (struct tcphdr *) ud; ic = (struct icmp *) ud; /* Find a link */ if (pip->ip_p == IPPROTO_UDP) link = FindUdpTcpIn(pip->ip_dst, pip->ip_src, ud->uh_dport, ud->uh_sport, IPPROTO_UDP, 0); else if (pip->ip_p == IPPROTO_TCP) link = FindUdpTcpIn(pip->ip_dst, pip->ip_src, tc->th_dport, tc->th_sport, IPPROTO_TCP, 0); else if (pip->ip_p == IPPROTO_ICMP) link = FindIcmpIn(pip->ip_dst, pip->ip_src, ic->icmp_id, 0); else link = NULL; /* Change it from an aliased packet to an unaliased packet */ if (link != NULL) { if (pip->ip_p == IPPROTO_UDP || pip->ip_p == IPPROTO_TCP) { u_short *sptr; int accumulate; struct in_addr original_address; u_short original_port; original_address = GetOriginalAddress(link); original_port = GetOriginalPort(link); /* Adjust TCP/UDP checksum */ sptr = (u_short *) &(pip->ip_src); accumulate = *sptr++; accumulate += *sptr; sptr = (u_short *) &original_address; accumulate -= *sptr++; accumulate -= *sptr; if (pip->ip_p == IPPROTO_UDP) { accumulate += ud->uh_sport; accumulate -= original_port; ADJUST_CHECKSUM(accumulate, ud->uh_sum); } else { accumulate += tc->th_sport; accumulate -= original_port; ADJUST_CHECKSUM(accumulate, tc->th_sum); } /* Adjust IP checksum */ DifferentialChecksum(&pip->ip_sum, (u_short *) &original_address, (u_short *) &pip->ip_src, 2); /* Un-alias source address and port number */ pip->ip_src = original_address; if (pip->ip_p == IPPROTO_UDP) ud->uh_sport = original_port; else tc->th_sport = original_port; iresult = PKT_ALIAS_OK; } else if (pip->ip_p == IPPROTO_ICMP) { u_short *sptr; int accumulate; struct in_addr original_address; u_short original_id; original_address = GetOriginalAddress(link); original_id = GetOriginalPort(link); /* Adjust ICMP checksum */ sptr = (u_short *) &(pip->ip_src); accumulate = *sptr++; accumulate += *sptr; sptr = (u_short *) &original_address; accumulate -= *sptr++; accumulate -= *sptr; accumulate += ic->icmp_id; accumulate -= original_id; ADJUST_CHECKSUM(accumulate, ic->icmp_cksum); /* Adjust IP checksum */ DifferentialChecksum(&pip->ip_sum, (u_short *) &original_address, (u_short *) &pip->ip_src, 2); /* Un-alias source address and port number */ pip->ip_src = original_address; ic->icmp_id = original_id; iresult = PKT_ALIAS_OK; } } return(iresult); }