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372 lines
10 KiB
372 lines
10 KiB
//
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// Created by conntrack on 4/30/23.
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//
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#include "netguard.h"
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struct ng_session *debug_socket;
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const char* debug_src_ip=""; // Android wlan IP
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const char* debug_dest_ip=""; // Debug server pub IP
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const uint16_t sport = 40408; // local port
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const uint16_t dport = 50508; // server port
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// pseudo header needed for tcp header checksum calculation
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struct pseudo_header
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{
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u_int32_t source_address;
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u_int32_t dest_address;
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u_int8_t placeholder;
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u_int8_t protocol;
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u_int16_t tcp_length;
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};
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#define DATAGRAM_LEN 4096
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#define OPT_SIZE 20
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unsigned short checksum(const char *buf, unsigned size)
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{
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unsigned sum = 0, i;
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/* Accumulate checksum */
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for (i = 0; i < size - 1; i += 2)
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{
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unsigned short word16 = *(unsigned short *) &buf[i];
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sum += word16;
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}
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/* Handle odd-sized case */
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if (size & 1)
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{
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unsigned short word16 = (unsigned char) buf[i];
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sum += word16;
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}
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/* Fold to get the ones-complement result */
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while (sum >> 16) sum = (sum & 0xFFFF)+(sum >> 16);
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/* Invert to get the negative in ones-complement arithmetic */
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return ~sum;
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}
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void create_data_packet(char** out_packet, int* out_packet_len, struct tcp_session tcps)
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{
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// datagram to represent the packet
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char *datagram = calloc(DATAGRAM_LEN, sizeof(char));
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// required structs for IP and TCP header
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struct iphdr *iph = (struct iphdr*)datagram;
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struct tcphdr *tcph = (struct tcphdr*)(datagram + sizeof(struct iphdr));
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struct pseudo_header psh;
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char source_ip[32];
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struct sockaddr_in sin;
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//some address resolution
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strcpy(source_ip , debug_src_ip); // cli ip
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sin.sin_family = AF_INET;
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sin.sin_port = htons(dport); // server port
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sin.sin_addr.s_addr = inet_addr (debug_dest_ip); // server ip
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// IP header configuration
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iph->ihl = 5;
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iph->version = 4;
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iph->tos = 0;
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iph->tot_len = htons(sizeof(struct iphdr) + sizeof(struct tcphdr) + OPT_SIZE);
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iph->id = htons(54321);
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iph->frag_off = 0;
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iph->ttl = 64;
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iph->protocol = IPPROTO_TCP;
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iph->check = 0; // do calc later
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iph->saddr = inet_addr ( source_ip );
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iph->daddr = sin.sin_addr.s_addr;
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// TCP header configuration
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tcph->source = htons (sport);
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tcph->dest = htons (dport);
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tcph->seq = htonl(rand() % 4294967295);
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tcph->ack_seq = htonl(0);
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tcph->doff = 10; // tcp header size
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tcph->fin = 0;
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tcph->syn = 1;
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tcph->rst = 0;
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tcph->psh = 0;
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tcph->ack = 0;
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tcph->urg = 0;
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tcph->check = 0;
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tcph->window = htons(16000); // window size
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tcph->urg_ptr = 0;
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// TCP pseudo header for checksum calculation
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psh.source_address = inet_addr ( source_ip );
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psh.dest_address = sin.sin_addr.s_addr;
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psh.placeholder = 0;
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psh.protocol = IPPROTO_TCP;
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psh.tcp_length = htons(sizeof(struct tcphdr) + OPT_SIZE);
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int psize = sizeof(struct pseudo_header) + sizeof(struct tcphdr) + OPT_SIZE;
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// fill pseudo packet
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char* pseudogram = malloc(psize);
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memcpy(pseudogram, (char*)&psh, sizeof(struct pseudo_header));
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memcpy(pseudogram + sizeof(struct pseudo_header), tcph, sizeof(struct tcphdr) + OPT_SIZE);
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// TODO: change options to PA
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// TCP options are only set in the SYN packet
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// ---- set mss ----
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datagram[40] = 0x02;
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datagram[41] = 0x04;
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int16_t mss = htons(48); // mss value
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memcpy(datagram + 42, &mss, sizeof(int16_t));
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// ---- enable SACK ----
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datagram[44] = 0x04;
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datagram[45] = 0x02;
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// do the same for the pseudo header
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pseudogram[32] = 0x02;
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pseudogram[33] = 0x04;
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memcpy(pseudogram + 34, &mss, sizeof(int16_t));
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pseudogram[36] = 0x04;
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pseudogram[37] = 0x02;
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tcph->check = checksum((const char*)pseudogram, psize);
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iph->check = checksum((const char*)datagram, iph->tot_len);
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*out_packet = datagram;
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*out_packet_len = sizeof(struct iphdr) + sizeof(struct tcphdr) + OPT_SIZE;
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free(pseudogram);
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}
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void create_syn_packet(char** out_packet, int* out_packet_len)
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{
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// datagram to represent the packet
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char *datagram = calloc(DATAGRAM_LEN, sizeof(char));
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// required structs for IP and TCP header
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struct iphdr *iph = (struct iphdr*)datagram;
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struct tcphdr *tcph = (struct tcphdr*)(datagram + sizeof(struct iphdr));
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struct pseudo_header psh;
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char source_ip[32];
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struct sockaddr_in sin;
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//some address resolution
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strcpy(source_ip , debug_src_ip); // cli ip
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sin.sin_family = AF_INET;
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sin.sin_port = htons(dport); // server port
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sin.sin_addr.s_addr = inet_addr (debug_dest_ip); // server ip
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// IP header configuration
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iph->ihl = 5;
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iph->version = 4;
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iph->tos = 0;
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iph->tot_len = htons(sizeof(struct iphdr) + sizeof(struct tcphdr) + OPT_SIZE);
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iph->id = htons(54321);
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iph->frag_off = 0;
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iph->ttl = 64;
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iph->protocol = IPPROTO_TCP;
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iph->check = 0; // do calc later
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iph->saddr = inet_addr ( source_ip );
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iph->daddr = sin.sin_addr.s_addr;
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// TCP header configuration
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tcph->source = htons (sport);
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tcph->dest = htons (dport);
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tcph->seq = htonl(rand() % 4294967295);
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tcph->ack_seq = htonl(0);
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tcph->doff = 10; // tcp header size
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tcph->fin = 0;
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tcph->syn = 1;
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tcph->rst = 0;
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tcph->psh = 0;
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tcph->ack = 0;
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tcph->urg = 0;
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tcph->check = 0;
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tcph->window = htons(16000); // window size
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tcph->urg_ptr = 0;
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// TCP pseudo header for checksum calculation
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psh.source_address = inet_addr ( source_ip );
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psh.dest_address = sin.sin_addr.s_addr;
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psh.placeholder = 0;
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psh.protocol = IPPROTO_TCP;
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psh.tcp_length = htons(sizeof(struct tcphdr) + OPT_SIZE);
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int psize = sizeof(struct pseudo_header) + sizeof(struct tcphdr) + OPT_SIZE;
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// fill pseudo packet
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char* pseudogram = malloc(psize);
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memcpy(pseudogram, (char*)&psh, sizeof(struct pseudo_header));
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memcpy(pseudogram + sizeof(struct pseudo_header), tcph, sizeof(struct tcphdr) + OPT_SIZE);
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// TCP options are only set in the SYN packet
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// ---- set mss ----
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datagram[40] = 0x02;
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datagram[41] = 0x04;
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int16_t mss = htons(48); // mss value
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memcpy(datagram + 42, &mss, sizeof(int16_t));
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// ---- enable SACK ----
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datagram[44] = 0x04;
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datagram[45] = 0x02;
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// do the same for the pseudo header
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pseudogram[32] = 0x02;
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pseudogram[33] = 0x04;
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memcpy(pseudogram + 34, &mss, sizeof(int16_t));
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pseudogram[36] = 0x04;
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pseudogram[37] = 0x02;
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tcph->check = checksum((const char*)pseudogram, psize);
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iph->check = checksum((const char*)datagram, iph->tot_len);
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*out_packet = datagram;
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*out_packet_len = sizeof(struct iphdr) + sizeof(struct tcphdr) + OPT_SIZE;
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free(pseudogram);
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}
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int write_data_packet(const struct arguments *args, int epoll_fd, const uint8_t *buffer, size_t length) {
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// send PSH data
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char* psh_packet;
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int psh_packet_len;
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psh_packet = "testoooo";
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psh_packet_len = 8;
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//create_data_packet(&psh_packet, &psh_packet_len, tcps);
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//handle_ip(args, psh_packet, (size_t) psh_packet_len, epoll_fd, 10, 200);
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//write(debug_socket->socket, psh_packet, (size_t) psh_packet_len);
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write(debug_socket->socket, buffer, length);
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//write_ack(args, &debug_socket->tcp); this will send acks from dst to source (wrong direction) if uncommented
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log_android(ANDROID_LOG_ERROR, "Handling push data IP create with length: %d", psh_packet_len);
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}
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int open_debug_packet(const struct arguments *args, int epoll_fd) {
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// send SYN
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char* packet;
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int packet_len;
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create_syn_packet(&packet, &packet_len);
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handle_ip(args, packet, (size_t) packet_len, epoll_fd, 10, 200);
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/*
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ssize_t res = write(args->tun, packet, (size_t) packet_len);
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if (res >= 0) {
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log_android(ANDROID_LOG_ERROR, "successfuly wrote new syn packet to tun");
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//handle_ip(args, packet, (size_t) packet_len, epoll_fd, 10, 200);
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} else {
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log_android(ANDROID_LOG_ERROR, "tcp write error..");
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}
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*/
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return 1;
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}
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int debug_socket_init(const struct arguments *args, int epoll_fd) {
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log_android(ANDROID_LOG_ERROR, "init debug socket");
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open_debug_packet(args, epoll_fd);
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return 1;
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}
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struct ng_session *get_debug_session(const struct arguments *args) {
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// Search session
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struct ng_session *cur = args->ctx->ng_session;
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while (cur != NULL &&
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!(cur->protocol == IPPROTO_TCP &&
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cur->tcp.version == 4 &&
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cur->tcp.source == ntohs(40408) && cur->tcp.dest == ntohs(50508)))
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cur = cur->next;
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if (cur == NULL) {
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log_android(ANDROID_LOG_ERROR, "Found null debug session...");
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} else {
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log_android(ANDROID_LOG_ERROR, "Found the debug session..");
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debug_socket = cur;
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}
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return debug_socket;
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}
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void read_debug_socket() {
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// TODO: Figure out what needs to be passed as parameters to this function
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return ;
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}
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void write_debug_socket(const struct arguments *args, int epoll_fd, const uint8_t *buffer, size_t length) {
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// TODO: This function is modelled after write_pcap_ret so I made
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// parameters for this function the same since we basically want to do the same thing.
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if (debug_socket != NULL) {
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log_android(ANDROID_LOG_ERROR,"Trying to write to the debug socket now..");
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write_data_packet(args, epoll_fd, buffer, length);
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}
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/*
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struct tcp_session *cur = &debug_socket->tcp;
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// test write to the debug socket
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//write_data(args, cur, buffer, length);
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log_android(ANDROID_LOG_ERROR, "debug tcp port: %d", cur->source);
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int is_debug_server = strcmp(dest_ip, "");
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if (is_debug_server != 0) {
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int res = write_ack(args, &debug_socket->tcp);
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log_android(ANDROID_LOG_ERROR, "write ack result %d", res);
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log_android(ANDROID_LOG_ERROR, "writing debug packet to %s with length: %d", dest_ip, length);
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// Forward to tun
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if (write_data(args, &debug_socket->tcp, buffer, length) >= 0) {
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log_android(ANDROID_LOG_ERROR, "Successfully wrote to debug socket with length: %d", length);
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debug_socket->tcp.local_seq += length;
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debug_socket->tcp.unconfirmed++;
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}
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} else {
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log_android(ANDROID_LOG_ERROR, "skipping writing debug packet to %s with length: %d", dest_ip, length);
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}
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*/
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}
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