int
AliasHandlePptpGreOut(struct ip *pip)
{
GreHdr *gr;
struct alias_link *link;
gr = (GreHdr *)((char *)pip + (pip->ip_hl << 2));
/* Check GRE header bits. */
if ((ntohl(*((u_int32_t *)gr)) & PPTP_INIT_MASK) != PPTP_INIT_VALUE)
return (-1);
link = FindPptpOutByPeerCallId(pip->ip_src, pip->ip_dst, gr->gh_call_id);
if (link != NULL) {
struct in_addr alias_addr = GetAliasAddress(link);
/* Change source IP address. */
DifferentialChecksum(&pip->ip_sum,
(u_short *)&alias_addr,
(u_short *)&pip->ip_src,
2);
pip->ip_src = alias_addr;
}
return (0);
}
static int
ProtoAliasOut(struct ip *pip)
{
/*
Handle outgoing IP packets. The
only thing which is done in this case is to alias
the source IP address of the packet.
*/
struct alias_link *link;
/* Return if proxy-only mode is enabled */
if (packetAliasMode & PKT_ALIAS_PROXY_ONLY)
return PKT_ALIAS_OK;
link = FindProtoOut(pip->ip_src, pip->ip_dst, pip->ip_p);
if (link != NULL)
{
struct in_addr alias_address;
alias_address = GetAliasAddress(link);
/* Change source address */
DifferentialChecksum(&pip->ip_sum,
(u_short *) &alias_address,
(u_short *) &pip->ip_src,
2);
pip->ip_src = alias_address;
return(PKT_ALIAS_OK);
}
return(PKT_ALIAS_IGNORED);
}
static int
ProtoAliasOut(struct libalias *la, struct in_addr *ip_src,
struct in_addr ip_dst, u_char ip_p, u_short *ip_sum, int create)
{
/*
Handle outgoing IP packets. The
only thing which is done in this case is to alias
the source IP address of the packet.
*/
struct alias_link *lnk;
LIBALIAS_LOCK_ASSERT(la);
(void)create;
/* Return if proxy-only mode is enabled */
if (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY)
return (PKT_ALIAS_OK);
lnk = FindProtoOut(la, *ip_src, ip_dst, ip_p);
if (lnk != NULL) {
struct in_addr alias_address;
alias_address = GetAliasAddress(lnk);
/* Change source address */
DifferentialChecksum(ip_sum,
&alias_address, ip_src, 2);
*ip_src = alias_address;
return (PKT_ALIAS_OK);
}
return (PKT_ALIAS_IGNORED);
}
static int
alias_skinny_opnrcvch_ack(struct libalias *la, struct OpenReceiveChannelAck *opnrcvch_ack,
struct ip *pip, struct tcphdr *tc,
struct alias_link *lnk, u_int32_t * localIpAddr,
ConvDirection direction)
{
struct in_addr null_addr;
struct alias_link *opnrcv_lnk;
u_int32_t localPort;
(void)lnk;
(void)direction;
*localIpAddr = (u_int32_t) opnrcvch_ack->ipAddr;
localPort = opnrcvch_ack->port;
null_addr.s_addr = INADDR_ANY;
opnrcv_lnk = FindUdpTcpOut(la, pip->ip_src, null_addr,
htons((u_short) opnrcvch_ack->port), 0,
IPPROTO_UDP, 1);
opnrcvch_ack->ipAddr = (u_int32_t) GetAliasAddress(opnrcv_lnk).s_addr;
opnrcvch_ack->port = (u_int32_t) ntohs(GetAliasPort(opnrcv_lnk));
tc->th_sum = 0;
#ifdef _KERNEL
tc->th_x2 = 1;
#else
tc->th_sum = TcpChecksum(pip);
#endif
return (0);
}
static int
UdpAliasOut(struct libalias *la, struct ip *pip, int create)
{
struct udphdr *ud;
struct alias_link *lnk;
int error;
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 = 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;
ad.lnk = lnk;
ad.oaddr = NULL;
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);
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
alias_skinny_reg_msg(struct RegisterMessage *reg_msg, struct ip *pip,
struct tcphdr *tc, struct alias_link *link,
ConvDirection direction)
{
reg_msg->ipAddr = (u_int32_t) GetAliasAddress(link).s_addr;
tc->th_sum = 0;
tc->th_sum = TcpChecksum(pip);
return 0;
}
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
IcmpAliasOut1(struct ip *pip)
{
/*
Alias outgoing echo and timestamp requests.
De-alias outgoing echo and timestamp replies.
*/
struct alias_link *link;
struct icmp *ic;
ic = (struct icmp *) ((char *) pip + (pip->ip_hl << 2));
/* Save overwritten data for when echo packet returns */
link = FindIcmpOut(pip->ip_src, pip->ip_dst, ic->icmp_id, 1);
if (link != NULL)
{
u_short alias_id;
int accumulate;
alias_id = GetAliasPort(link);
/* Since data field is being modified, adjust ICMP checksum */
accumulate = ic->icmp_id;
accumulate -= alias_id;
ADJUST_CHECKSUM(accumulate, ic->icmp_cksum);
/* Alias sequence number */
ic->icmp_id = alias_id;
/* Change source address */
{
struct in_addr alias_address;
alias_address = GetAliasAddress(link);
DifferentialChecksum(&pip->ip_sum,
(u_short *) &alias_address,
(u_short *) &pip->ip_src,
2);
pip->ip_src = alias_address;
}
return(PKT_ALIAS_OK);
}
return(PKT_ALIAS_IGNORED);
}
static int
alias_skinny_reg_msg(struct RegisterMessage *reg_msg, struct ip *pip,
struct tcphdr *tc, struct alias_link *lnk,
ConvDirection direction)
{
(void)direction;
reg_msg->ipAddr = (u_int32_t) GetAliasAddress(lnk).s_addr;
tc->th_sum = 0;
#ifdef _KERNEL
tc->th_x2 = 1;
#else
tc->th_sum = TcpChecksum(pip);
#endif
return (0);
}
static void
AliasHandleCUSeeMeOut(struct libalias *la, struct ip *pip, struct alias_link *lnk)
{
struct udphdr *ud = ip_next(pip);
if (ntohs(ud->uh_ulen) - sizeof(struct udphdr) >= sizeof(struct cu_header)) {
struct cu_header *cu;
struct alias_link *cu_lnk;
cu = udp_next(ud);
if (cu->addr)
cu->addr = (u_int32_t) GetAliasAddress(lnk).s_addr;
cu_lnk = FindUdpTcpOut(la, pip->ip_src, GetDestAddress(lnk),
ud->uh_dport, 0, IPPROTO_UDP, 1);
#ifndef NO_FW_PUNCH
if (cu_lnk)
PunchFWHole(cu_lnk);
#endif
}
}
void
AliasHandleCUSeeMeOut(struct ip *pip, struct alias_link *link)
{
struct udphdr *ud;
ud = (struct udphdr *)((char *)pip + (pip->ip_hl << 2));
if (ntohs(ud->uh_ulen) - sizeof(struct udphdr) >= sizeof(struct cu_header)) {
struct cu_header *cu;
struct alias_link *cu_link;
cu = (struct cu_header *)(ud + 1);
if (cu->addr)
cu->addr = (u_int32_t)GetAliasAddress(link).s_addr;
cu_link = FindUdpTcpOut(pip->ip_src, GetDestAddress(link),
ud->uh_dport, 0, IPPROTO_UDP, 1);
#ifndef NO_FW_PUNCH
if (cu_link)
PunchFWHole(cu_link);
#endif
}
}
static void
NewFtpMessage(struct libalias *la, struct ip *pip,
struct alias_link *lnk,
int maxpacketsize,
int ftp_message_type)
{
struct alias_link *ftp_lnk;
/* Security checks. */
if (pip->ip_src.s_addr != la->true_addr.s_addr)
return;
if (la->true_port < IPPORT_RESERVED)
return;
/* Establish link to address and port found in FTP control message. */
ftp_lnk = FindUdpTcpOut(la, la->true_addr, GetDestAddress(lnk),
htons(la->true_port), 0, IPPROTO_TCP, 1);
if (ftp_lnk != NULL) {
int slen, hlen, tlen, dlen;
struct tcphdr *tc;
#ifndef NO_FW_PUNCH
/* Punch hole in firewall */
PunchFWHole(ftp_lnk);
#endif
/* 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;
/* Create new FTP message. */
{
char stemp[MAX_MESSAGE_SIZE + 1];
char *sptr;
u_short alias_port;
u_char *ptr;
int a1, a2, a3, a4, p1, p2;
struct in_addr alias_address;
/* Decompose alias address into quad format */
alias_address = GetAliasAddress(lnk);
ptr = (u_char *) & alias_address.s_addr;
a1 = *ptr++;
a2 = *ptr++;
a3 = *ptr++;
a4 = *ptr;
alias_port = GetAliasPort(ftp_lnk);
/* Prepare new command */
switch (ftp_message_type) {
case FTP_PORT_COMMAND:
case FTP_227_REPLY:
/* Decompose alias port into pair format. */
ptr = (char *)&alias_port;
p1 = *ptr++;
p2 = *ptr;
if (ftp_message_type == FTP_PORT_COMMAND) {
/* Generate PORT command string. */
sprintf(stemp, "PORT %d,%d,%d,%d,%d,%d\r\n",
a1, a2, a3, a4, p1, p2);
} else {
/* Generate 227 reply string. */
sprintf(stemp,
"227 Entering Passive Mode (%d,%d,%d,%d,%d,%d)\r\n",
a1, a2, a3, a4, p1, p2);
}
break;
case FTP_EPRT_COMMAND:
/* Generate EPRT command string. */
sprintf(stemp, "EPRT |1|%d.%d.%d.%d|%d|\r\n",
a1, a2, a3, a4, ntohs(alias_port));
break;
case FTP_229_REPLY:
/* Generate 229 reply string. */
sprintf(stemp, "229 Entering Extended Passive Mode (|||%d|)\r\n",
ntohs(alias_port));
break;
}
/* Save string length for IP header modification */
slen = strlen(stemp);
/* Copy modified buffer into IP packet. */
sptr = (char *)pip;
sptr += hlen;
strncpy(sptr, stemp, maxpacketsize - hlen);
}
/* Save information regarding modified seq and ack numbers */
{
int delta;
SetAckModified(lnk);
tc = (struct tcphdr *)ip_next(pip);
delta = GetDeltaSeqOut(tc->th_seq, lnk);
AddSeq(lnk, delta + slen - dlen, pip->ip_hl,
pip->ip_len, tc->th_seq, tc->th_off);
}
/* Revise IP header */
{
u_short new_len;
new_len = htons(hlen + slen);
DifferentialChecksum(&pip->ip_sum,
&new_len,
&pip->ip_len,
1);
pip->ip_len = new_len;
}
/* Compute TCP checksum for revised packet */
tc->th_sum = 0;
#ifdef _KERNEL
tc->th_x2 = 1;
#else
tc->th_sum = TcpChecksum(pip);
#endif
} else {
#ifdef LIBALIAS_DEBUG
fprintf(stderr,
"PacketAlias/HandleFtpOut: Cannot allocate FTP data port\n");
#endif
}
}
static void
AliasHandlePptpIn(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;
u_int16_t *pcall_id;
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_InCallConn:
case PPTP_WanErrorNotify:
case PPTP_SetLinkInfo:
pcall_id = &cptr->cid1;
break;
case PPTP_OutCallReply:
case PPTP_InCallReply:
pcall_id = &cptr->cid2;
break;
case PPTP_CallDiscNotify: /* Connection closed. */
pptp_lnk = FindPptpInByCallId(la, GetDestAddress(lnk),
GetAliasAddress(lnk),
cptr->cid1);
if (pptp_lnk != NULL)
SetExpire(pptp_lnk, 0);
return;
default:
return;
}
/* Find PPTP link for address and Call ID found in PPTP Control Msg */
pptp_lnk = FindPptpInByPeerCallId(la, GetDestAddress(lnk),
GetAliasAddress(lnk),
*pcall_id);
if (pptp_lnk != NULL) {
int accumulate = *pcall_id;
/* De-alias the Peer's Call Id. */
*pcall_id = GetOriginalPort(pptp_lnk);
/* Compute TCP checksum for modified packet */
tc = (struct tcphdr *)ip_next(pip);
accumulate -= *pcall_id;
ADJUST_CHECKSUM(accumulate, tc->th_sum);
if (ctl_type == PPTP_OutCallReply || ctl_type == PPTP_InCallReply) {
PptpCode codes = (PptpCode) (cptr + 1);
if (codes->resCode == 1) /* Connection
* established, */
SetDestCallId(pptp_lnk, /* note the Call ID. */
cptr->cid1);
else
SetExpire(pptp_lnk, 0); /* Connection refused. */
}
}
}
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
IcmpAliasOut2(struct libalias *la, struct ip *pip)
{
/*
Alias outgoing 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;
LIBALIAS_LOCK_ASSERT(la);
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 = FindUdpTcpOut(la, ip->ip_dst, ip->ip_src,
ud->uh_dport, ud->uh_sport,
IPPROTO_UDP, 0);
else if (ip->ip_p == IPPROTO_TCP)
lnk = FindUdpTcpOut(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 = FindIcmpOut(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;
struct in_addr alias_address;
u_short alias_port;
alias_address = GetAliasAddress(lnk);
alias_port = GetAliasPort(lnk);
/* Adjust ICMP checksum */
accumulate = twowords(&ip->ip_dst);
accumulate -= twowords(&alias_address);
accumulate += ud->uh_dport;
accumulate -= alias_port;
ADJUST_CHECKSUM(accumulate, ic->icmp_cksum);
/*
* Alias address in IP header if it comes from the host
* the original TCP/UDP packet was destined for.
*/
if (pip->ip_src.s_addr == ip->ip_dst.s_addr) {
DifferentialChecksum(&pip->ip_sum,
&alias_address, &pip->ip_src, 2);
pip->ip_src = alias_address;
}
/* Alias address and port number of original IP packet
fragment contained in ICMP data section */
ip->ip_dst = alias_address;
ud->uh_dport = alias_port;
} else if (ip->ip_p == IPPROTO_ICMP) {
int accumulate;
struct in_addr alias_address;
u_short alias_id;
alias_address = GetAliasAddress(lnk);
alias_id = GetAliasPort(lnk);
/* Adjust ICMP checksum */
accumulate = twowords(&ip->ip_dst);
accumulate -= twowords(&alias_address);
accumulate += ic2->icmp_id;
accumulate -= alias_id;
ADJUST_CHECKSUM(accumulate, ic->icmp_cksum);
/*
* Alias address in IP header if it comes from the host
* the original ICMP message was destined for.
*/
if (pip->ip_src.s_addr == ip->ip_dst.s_addr) {
DifferentialChecksum(&pip->ip_sum,
&alias_address, &pip->ip_src, 2);
pip->ip_src = alias_address;
}
/* Alias address of original IP packet and sequence number of
embedded ICMP datagram */
ip->ip_dst = alias_address;
ic2->icmp_id = alias_id;
}
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;
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 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);
}
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 void
AliasHandleIrcOut(struct libalias *la,
struct ip *pip, /* IP packet to examine */
struct alias_link *lnk, /* Which link are we on? */
int maxsize /* Maximum size of IP packet including
* headers */
)
{
int hlen, tlen, dlen;
struct in_addr true_addr;
u_short true_port;
char *sptr;
struct tcphdr *tc;
int i; /* Iterator through the source */
/* 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;
/*
* Return if data length is too short - assume an entire PRIVMSG in
* each packet.
*/
if (dlen < (int)sizeof(":[email protected] PRIVMSG A :aDCC 1 1a") - 1)
return;
/* Place string pointer at beginning of data */
sptr = (char *)pip;
sptr += hlen;
maxsize -= hlen; /* We're interested in maximum size of
* data, not packet */
/* Search for a CTCP command [Note 1] */
for (i = 0; i < dlen; i++) {
if (sptr[i] == '\001')
goto lFOUND_CTCP;
}
return; /* No CTCP commands in */
/* Handle CTCP commands - the buffer may have to be copied */
lFOUND_CTCP:
{
char newpacket[65536]; /* Estimate of maximum packet size
* :) */
unsigned int copyat = i; /* Same */
unsigned int iCopy = 0; /* How much data have we written to
* copy-back string? */
unsigned long org_addr; /* Original IP address */
unsigned short org_port; /* Original source port
* address */
lCTCP_START:
if (i >= dlen || iCopy >= sizeof(newpacket))
goto lPACKET_DONE;
newpacket[iCopy++] = sptr[i++]; /* Copy the CTCP start
* character */
/* Start of a CTCP */
if (i + 4 >= dlen) /* Too short for DCC */
goto lBAD_CTCP;
if (sptr[i + 0] != 'D')
goto lBAD_CTCP;
if (sptr[i + 1] != 'C')
goto lBAD_CTCP;
if (sptr[i + 2] != 'C')
goto lBAD_CTCP;
if (sptr[i + 3] != ' ')
goto lBAD_CTCP;
/* We have a DCC command - handle it! */
i += 4; /* Skip "DCC " */
if (iCopy + 4 > sizeof(newpacket))
goto lPACKET_DONE;
newpacket[iCopy++] = 'D';
newpacket[iCopy++] = 'C';
newpacket[iCopy++] = 'C';
newpacket[iCopy++] = ' ';
DBprintf(("Found DCC\n"));
/*
* Skip any extra spaces (should not occur according to
* protocol, but DCC breaks CTCP protocol anyway
*/
while (sptr[i] == ' ') {
if (++i >= dlen) {
DBprintf(("DCC packet terminated in just spaces\n"));
goto lPACKET_DONE;
}
}
DBprintf(("Transferring command...\n"));
while (sptr[i] != ' ') {
newpacket[iCopy++] = sptr[i];
if (++i >= dlen || iCopy >= sizeof(newpacket)) {
DBprintf(("DCC packet terminated during command\n"));
goto lPACKET_DONE;
}
}
/* Copy _one_ space */
if (i + 1 < dlen && iCopy < sizeof(newpacket))
newpacket[iCopy++] = sptr[i++];
DBprintf(("Done command - removing spaces\n"));
/*
* Skip any extra spaces (should not occur according to
* protocol, but DCC breaks CTCP protocol anyway
*/
while (sptr[i] == ' ') {
if (++i >= dlen) {
DBprintf(("DCC packet terminated in just spaces (post-command)\n"));
goto lPACKET_DONE;
}
}
DBprintf(("Transferring filename...\n"));
while (sptr[i] != ' ') {
newpacket[iCopy++] = sptr[i];
if (++i >= dlen || iCopy >= sizeof(newpacket)) {
DBprintf(("DCC packet terminated during filename\n"));
goto lPACKET_DONE;
}
}
/* Copy _one_ space */
if (i + 1 < dlen && iCopy < sizeof(newpacket))
newpacket[iCopy++] = sptr[i++];
DBprintf(("Done filename - removing spaces\n"));
/*
* Skip any extra spaces (should not occur according to
* protocol, but DCC breaks CTCP protocol anyway
*/
while (sptr[i] == ' ') {
if (++i >= dlen) {
DBprintf(("DCC packet terminated in just spaces (post-filename)\n"));
goto lPACKET_DONE;
}
}
DBprintf(("Fetching IP address\n"));
/* Fetch IP address */
org_addr = 0;
while (i < dlen && isdigit(sptr[i])) {
if (org_addr > ULONG_MAX / 10UL) { /* Terminate on overflow */
DBprintf(("DCC Address overflow (org_addr == 0x%08lx, next char %c\n", org_addr, sptr[i]));
goto lBAD_CTCP;
}
org_addr *= 10;
org_addr += sptr[i++] - '0';
}
DBprintf(("Skipping space\n"));
if (i + 1 >= dlen || sptr[i] != ' ') {
DBprintf(("Overflow (%d >= %d) or bad character (%02x) terminating IP address\n", i + 1, dlen, sptr[i]));
goto lBAD_CTCP;
}
/*
* Skip any extra spaces (should not occur according to
* protocol, but DCC breaks CTCP protocol anyway, so we
* might as well play it safe
*/
while (sptr[i] == ' ') {
if (++i >= dlen) {
DBprintf(("Packet failure - space overflow.\n"));
goto lPACKET_DONE;
}
}
DBprintf(("Fetching port number\n"));
/* Fetch source port */
org_port = 0;
while (i < dlen && isdigit(sptr[i])) {
if (org_port > 6554) { /* Terminate on overflow
* (65536/10 rounded up */
DBprintf(("DCC: port number overflow\n"));
goto lBAD_CTCP;
}
org_port *= 10;
org_port += sptr[i++] - '0';
}
/* Skip illegal addresses (or early termination) */
if (i >= dlen || (sptr[i] != '\001' && sptr[i] != ' ')) {
DBprintf(("Bad port termination\n"));
goto lBAD_CTCP;
}
DBprintf(("Got IP %lu and port %u\n", org_addr, (unsigned)org_port));
/* We've got the address and port - now alias it */
{
struct alias_link *dcc_lnk;
struct in_addr destaddr;
true_port = htons(org_port);
true_addr.s_addr = htonl(org_addr);
destaddr.s_addr = 0;
/* Sanity/Security checking */
if (!org_addr || !org_port ||
pip->ip_src.s_addr != true_addr.s_addr ||
org_port < IPPORT_RESERVED)
goto lBAD_CTCP;
/*
* Steal the FTP_DATA_PORT - it doesn't really
* matter, and this would probably allow it through
* at least _some_ firewalls.
*/
dcc_lnk = FindUdpTcpOut(la, true_addr, destaddr,
true_port, 0,
IPPROTO_TCP, 1);
DBprintf(("Got a DCC link\n"));
if (dcc_lnk) {
struct in_addr alias_address; /* Address from aliasing */
u_short alias_port; /* Port given by
* aliasing */
int n;
#ifndef NO_FW_PUNCH
/* Generate firewall hole as appropriate */
PunchFWHole(dcc_lnk);
#endif
alias_address = GetAliasAddress(lnk);
n = snprintf(&newpacket[iCopy],
sizeof(newpacket) - iCopy,
"%lu ", (u_long) htonl(alias_address.s_addr));
if (n < 0) {
DBprintf(("DCC packet construct failure.\n"));
goto lBAD_CTCP;
}
if ((iCopy += n) >= sizeof(newpacket)) { /* Truncated/fit exactly
* - bad news */
DBprintf(("DCC constructed packet overflow.\n"));
goto lBAD_CTCP;
}
alias_port = GetAliasPort(dcc_lnk);
n = snprintf(&newpacket[iCopy],
sizeof(newpacket) - iCopy,
"%u", htons(alias_port));
if (n < 0) {
DBprintf(("DCC packet construct failure.\n"));
goto lBAD_CTCP;
}
iCopy += n;
/*
* Done - truncated cases will be taken
* care of by lBAD_CTCP
*/
DBprintf(("Aliased IP %lu and port %u\n", alias_address.s_addr, (unsigned)alias_port));
}
}
/*
* An uninteresting CTCP - state entered right after '\001'
* has been pushed. Also used to copy the rest of a DCC,
* after IP address and port has been handled
*/
lBAD_CTCP:
for (; i < dlen && iCopy < sizeof(newpacket); i++, iCopy++) {
newpacket[iCopy] = sptr[i]; /* Copy CTCP unchanged */
if (sptr[i] == '\001') {
goto lNORMAL_TEXT;
}
}
goto lPACKET_DONE;
/* Normal text */
lNORMAL_TEXT:
for (; i < dlen && iCopy < sizeof(newpacket); i++, iCopy++) {
newpacket[iCopy] = sptr[i]; /* Copy CTCP unchanged */
if (sptr[i] == '\001') {
goto lCTCP_START;
}
}
/* Handle the end of a packet */
lPACKET_DONE:
iCopy = iCopy > maxsize - copyat ? maxsize - copyat : iCopy;
memcpy(sptr + copyat, newpacket, iCopy);
/* Save information regarding modified seq and ack numbers */
{
int delta;
SetAckModified(lnk);
delta = GetDeltaSeqOut(pip, lnk);
AddSeq(pip, lnk, delta + copyat + iCopy - dlen);
}
/* Revise IP header */
{
u_short new_len;
new_len = htons(hlen + iCopy + copyat);
DifferentialChecksum(&pip->ip_sum,
&new_len,
&pip->ip_len,
1);
pip->ip_len = new_len;
}
/* Compute TCP checksum for revised packet */
tc->th_sum = 0;
#ifdef _KERNEL
tc->th_x2 = 1;
#else
tc->th_sum = TcpChecksum(pip);
#endif
return;
}
}
static int
TcpAliasOut(struct ip *pip, int maxpacketsize)
{
int proxy_type;
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 *link;
tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
proxy_type = ProxyCheck(pip, &proxy_server_address, &proxy_server_port);
if (proxy_type == 0 && (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;
u_short *sptr;
accumulate = tc->th_dport;
tc->th_dport = proxy_server_port;
accumulate -= tc->th_dport;
sptr = (u_short *) &(pip->ip_dst);
accumulate += *sptr++;
accumulate += *sptr;
sptr = (u_short *) &proxy_server_address;
accumulate -= *sptr++;
accumulate -= *sptr;
ADJUST_CHECKSUM(accumulate, tc->th_sum);
sptr = (u_short *) &(pip->ip_dst);
accumulate = *sptr++;
accumulate += *sptr;
pip->ip_dst = proxy_server_address;
sptr = (u_short *) &(pip->ip_dst);
accumulate -= *sptr++;
accumulate -= *sptr;
ADJUST_CHECKSUM(accumulate, pip->ip_sum);
}
link = FindUdpTcpOut(pip->ip_src, pip->ip_dst,
tc->th_sport, tc->th_dport,
IPPROTO_TCP, 1);
if (link !=NULL)
{
u_short alias_port;
struct in_addr alias_address;
int accumulate;
u_short *sptr;
/* 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(link, dest_port);
SetProxyAddress(link, dest_address);
ProxyModify(link, pip, maxpacketsize, proxy_type);
tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
}
/* Get alias address and port */
alias_port = GetAliasPort(link);
alias_address = GetAliasAddress(link);
/* Monitor TCP connection state */
TcpMonitorOut(pip, link);
/* Special processing for IP encoding protocols */
if (ntohs(tc->th_dport) == FTP_CONTROL_PORT_NUMBER
|| ntohs(tc->th_sport) == FTP_CONTROL_PORT_NUMBER)
AliasHandleFtpOut(pip, link, maxpacketsize);
else if (ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_1
|| ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_2)
AliasHandleIrcOut(pip, link, maxpacketsize);
else if (ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_1
|| ntohs(tc->th_sport) == RTSP_CONTROL_PORT_NUMBER_1
|| ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_2
|| ntohs(tc->th_sport) == RTSP_CONTROL_PORT_NUMBER_2)
AliasHandleRtspOut(pip, link, maxpacketsize);
else if (ntohs(tc->th_dport) == PPTP_CONTROL_PORT_NUMBER
|| ntohs(tc->th_sport) == PPTP_CONTROL_PORT_NUMBER)
AliasHandlePptpOut(pip, link);
/* 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;
sptr = (u_short *) &(pip->ip_src);
accumulate += *sptr++;
accumulate += *sptr;
sptr = (u_short *) &alias_address;
accumulate -= *sptr++;
accumulate -= *sptr;
/* Modify sequence number if necessary */
if (GetAckModified(link) == 1)
{
int delta;
delta = GetDeltaSeqOut(pip, link);
if (delta != 0)
{
sptr = (u_short *) &tc->th_seq;
accumulate += *sptr++;
accumulate += *sptr;
tc->th_seq = htonl(ntohl(tc->th_seq) + delta);
sptr = (u_short *) &tc->th_seq;
accumulate -= *sptr++;
accumulate -= *sptr;
}
}
ADJUST_CHECKSUM(accumulate, tc->th_sum);
/* Change source address */
sptr = (u_short *) &(pip->ip_src);
accumulate = *sptr++;
accumulate += *sptr;
pip->ip_src = alias_address;
sptr = (u_short *) &(pip->ip_src);
accumulate -= *sptr++;
accumulate -= *sptr;
ADJUST_CHECKSUM(accumulate, pip->ip_sum);
return(PKT_ALIAS_OK);
}
return(PKT_ALIAS_IGNORED);
}
static int
UdpAliasOut(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 = FindUdpTcpOut(pip->ip_src, pip->ip_dst,
ud->uh_sport, ud->uh_dport,
IPPROTO_UDP, 1);
if (link != NULL)
{
u_short alias_port;
struct in_addr alias_address;
alias_address = GetAliasAddress(link);
alias_port = GetAliasPort(link);
/* Special processing for IP encoding protocols */
if (ntohs(ud->uh_dport) == CUSEEME_PORT_NUMBER)
AliasHandleCUSeeMeOut(pip, link);
/* 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)
AliasHandleUdpNbt(pip, link, &alias_address, alias_port);
else if (ntohs(ud->uh_dport) == NETBIOS_NS_PORT_NUMBER
|| ntohs(ud->uh_sport) == NETBIOS_NS_PORT_NUMBER)
AliasHandleUdpNbtNS(pip, link, &pip->ip_src, &ud->uh_sport,
&alias_address, &alias_port);
/*
* We don't know in advance what TID the TFTP server will choose,
* so we create a wilcard link (destination port is unspecified)
* that will match any TID from a given destination.
*/
else if (ntohs(ud->uh_dport) == TFTP_PORT_NUMBER)
FindRtspOut(pip->ip_src, pip->ip_dst,
ud->uh_sport, alias_port, IPPROTO_UDP);
/* 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;
u_short *sptr;
accumulate = ud->uh_sport;
accumulate -= alias_port;
sptr = (u_short *) &(pip->ip_src);
accumulate += *sptr++;
accumulate += *sptr;
sptr = (u_short *) &alias_address;
accumulate -= *sptr++;
accumulate -= *sptr;
ADJUST_CHECKSUM(accumulate, ud->uh_sum);
}
/* Put alias port in UDP header */
ud->uh_sport = alias_port;
/* Change source address */
DifferentialChecksum(&pip->ip_sum,
(u_short *) &alias_address,
(u_short *) &pip->ip_src,
2);
pip->ip_src = alias_address;
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);
}