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Added module which arbitrarily increases the size of the packet we received. Needs some tweaking to allow for modification of the header and payload fields yet, but the space allocation is already there. Also, multiple improvements overall

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h3xduck
2021-11-24 20:41:07 -05:00
parent 74cc7ff9e5
commit 442f955cf5
8 changed files with 592 additions and 269 deletions
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49
src/ebpf/xdp_filter.bpf.c
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@@ -26,6 +26,7 @@
#include "packet/packet_manager.h"
#include "packet/protocol/tcp_helper.h"
#include "xdp/xdp_helper.h"
#include "common/common_utils.h"
@@ -118,9 +119,53 @@ int xdp_receive(struct xdp_md *ctx)
bpf_printk("H");
return XDP_PASS;
}
int data_len_prev = data_end-data;
int data_len_next = -1;
bpf_printk("BPF finished\n ");
payload[1] = 'b';
struct expand_return ret = expand_tcp_packet_payload(ctx, eth, ip, tcp, 2);
if(ret.code == 0){
//We must check bounds again, otherwise the verifier gets angry
data = (void*)(long)ret.ret_md.data;
data_end = (void*)(long)ret.ret_md.data_end;
eth = data;
if(ethernet_header_bound_check(eth, data_end)<0){
bpf_printk("Bound check A failed while expanding\n");
return XDP_PASS;
}
ip = data + sizeof(*eth);
if (ip_header_bound_check(ip, data_end)<0){
bpf_printk("Bound check B failed while expanding\n");
return XDP_PASS;
}
tcp = (void *)ip + sizeof(*ip);
/*if (get_protocol(data_end) != IPPROTO_TCP){
bpf_printk("Bound check C failed while expanding\n");
return XDP_PASS;
}*/
if (tcp_header_bound_check(tcp, data_end)){
bpf_printk("Bound check D failed while expanding\n");
return XDP_PASS;
}
payload_size = ntohs(ip->tot_len) - (tcp->doff * 4) - (ip->ihl * 4);
payload = (void *)tcp + tcp->doff*4;
/*if (tcp_payload_bound_check(payload, payload_size, data_end)){
bpf_printk("Bound check E failed while expanding\n");
return XDP_PASS;
}*/
bpf_printk("BPF finished with ret %i and payload %s of size %i\n ", ret.code, payload, payload_size);
}else{
bpf_printk("BPF finished with error on expansion\n");
}
data_len_next = data_end-data;
bpf_printk("Previous length: %i, current length: %i\n", data_len_prev, data_len_next);
//payload[4] = 'A';
//payload[6] = '\0';
//payload[1] = 'b';
/*if(!payload){
bpf_probe_read_str(&rb_event->payload, sizeof(rb_event->payload), (void *)payload);
bpf_ringbuf_submit(rb_event, 0);