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Merge pull request #22 from EaseTheWorld/handshake

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Handle weird 3-way handshake(syn&ack -> syn -> ack)
This commit is contained in:
Alexandre Dulaunoy 2019-08-16 21:04:45 +02:00 committed by GitHub
commit f10e4d7462
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 34 additions and 21 deletions
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39
base/tcppack.c
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@ -91,18 +91,13 @@ int process_tcp_packet(handler,ctx,p)
if(r!=R_NOT_FOUND) if(r!=R_NOT_FOUND)
ABORT(r); ABORT(r);
/*Note that we MUST receive the 3-way handshake in the if((p->tcp->th_flags & TH_SYN)!=TH_SYN){
proper order. This shouldn't be a problem, though,
except for simultaneous connects*/
if((p->tcp->th_flags & (TH_SYN|TH_ACK))!=TH_SYN){
DBG((0,"TCP: rejecting packet from unknown connection, seq: %u\n",ntohl(p->tcp->th_seq))); DBG((0,"TCP: rejecting packet from unknown connection, seq: %u\n",ntohl(p->tcp->th_seq)));
return(0); return(0);
} }
DBG((0,"SYN1 seq: %u",ntohl(p->tcp->th_seq)));
if(r=new_connection(handler,ctx,p,&conn)) if(r=new_connection(handler,ctx,p,&conn))
ABORT(r); ABORT(r);
conn->i2r.seq=ntohl(p->tcp->th_seq)+1;
return(0); return(0);
} }
@ -112,16 +107,22 @@ int process_tcp_packet(handler,ctx,p)
switch(conn->state){ switch(conn->state){
case TCP_STATE_SYN1: case TCP_STATE_SYN1:
if(direction != DIR_R2I) if(direction == DIR_R2I && (p->tcp->th_flags & TH_SYN)) {
break; DBG((0,"SYN2 seq: %u",ntohl(p->tcp->th_seq)));
if((p->tcp->th_flags & (TH_SYN|TH_ACK))!=(TH_SYN|TH_ACK))
break;
conn->r2i.seq=ntohl(p->tcp->th_seq)+1; conn->r2i.seq=ntohl(p->tcp->th_seq)+1;
conn->r2i.ack=ntohl(p->tcp->th_ack)+1; conn->r2i.ack=ntohl(p->tcp->th_ack)+1;
conn->state=TCP_STATE_SYN2; conn->state=TCP_STATE_ACK;
DBG((0,"SYN2 seq: %u",ntohl(p->tcp->th_seq))); }
break; break;
case TCP_STATE_SYN2: case TCP_STATE_SYN2:
if(direction == DIR_I2R && (p->tcp->th_flags & TH_SYN)) {
DBG((0,"SYN1 seq: %u",ntohl(p->tcp->th_seq)));
conn->i2r.seq=ntohl(p->tcp->th_seq)+1;
conn->i2r.ack=ntohl(p->tcp->th_ack)+1;
conn->state=TCP_STATE_ACK;
}
break;
case TCP_STATE_ACK:
{ {
char *sn=0,*dn=0; char *sn=0,*dn=0;
if(direction != DIR_I2R) if(direction != DIR_I2R)
@ -178,11 +179,23 @@ static int new_connection(handler,ctx,p,connp)
int r,_status; int r,_status;
tcp_conn *conn=0; tcp_conn *conn=0;
if ((p->tcp->th_flags & (TH_SYN|TH_ACK))==TH_SYN) {
if(r=tcp_create_conn(&conn,&p->ip->ip_src,ntohs(p->tcp->th_sport), if(r=tcp_create_conn(&conn,&p->ip->ip_src,ntohs(p->tcp->th_sport),
&p->ip->ip_dst,ntohs(p->tcp->th_dport))) &p->ip->ip_dst,ntohs(p->tcp->th_dport)))
ABORT(r); ABORT(r);
DBG((0,"SYN1 seq: %u",ntohl(p->tcp->th_seq)));
conn->i2r.seq=ntohl(p->tcp->th_seq)+1;
conn->i2r.ack=ntohl(p->tcp->th_ack)+1;
conn->state=TCP_STATE_SYN1; conn->state=TCP_STATE_SYN1;
} else { // SYN&ACK comes first somehow
if(r=tcp_create_conn(&conn,&p->ip->ip_dst,ntohs(p->tcp->th_dport),
&p->ip->ip_src,ntohs(p->tcp->th_sport)))
ABORT(r);
DBG((0,"SYN2 seq: %u",ntohl(p->tcp->th_seq)));
conn->r2i.seq=ntohl(p->tcp->th_seq)+1;
conn->r2i.ack=ntohl(p->tcp->th_ack)+1;
conn->state=TCP_STATE_SYN2;
}
memcpy(&conn->start_time,&p->ts,sizeof(struct timeval)); memcpy(&conn->start_time,&p->ts,sizeof(struct timeval));
memcpy(&conn->last_seen_time,&p->ts,sizeof(struct timeval)); memcpy(&conn->last_seen_time,&p->ts,sizeof(struct timeval));
if(r=create_proto_handler(handler,ctx,&conn->analyzer,conn,&p->ts)) if(r=create_proto_handler(handler,ctx,&conn->analyzer,conn,&p->ts))