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 void
AliasHandleFtpOut(
struct libalias *la,
struct ip *pip, /* IP packet to examine/patch */
struct alias_link *lnk, /* The link to go through (aliased port) */
int maxpacketsize /* The maximum size this packet can grow to
(including headers) */ )
{
int hlen, tlen, dlen, pflags;
char *sptr;
struct tcphdr *tc;
int ftp_message_type;
/* 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)) {
ftp_message_type = FTP_UNKNOWN_MESSAGE;
if (ntohs(tc->th_dport) == FTP_CONTROL_PORT_NUMBER) {
/*
* When aliasing a client, check for the PORT/EPRT command.
*/
if (ParseFtpPortCommand(la, sptr, dlen))
ftp_message_type = FTP_PORT_COMMAND;
else if (ParseFtpEprtCommand(la, sptr, dlen))
ftp_message_type = FTP_EPRT_COMMAND;
} else {
/*
* When aliasing a server, check for the 227/229 reply.
*/
if (ParseFtp227Reply(la, sptr, dlen))
ftp_message_type = FTP_227_REPLY;
else if (ParseFtp229Reply(la, sptr, dlen)) {
ftp_message_type = FTP_229_REPLY;
la->true_addr.s_addr = pip->ip_src.s_addr;
}
}
if (ftp_message_type != FTP_UNKNOWN_MESSAGE)
NewFtpMessage(la, pip, lnk, maxpacketsize, ftp_message_type);
}
/* Track the msgs which are CRLF term'd for PORT/PASV FW breach */
if (dlen) { /* only if there's data */
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);
}
}
