slitheen/relay_station/packet.h

/* Slitheen - a decoy routing system for censorship resistance
 * Copyright (C) 2017 Cecylia Bocovich (cbocovic@uwaterloo.ca)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, version 3.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Additional permission under GNU GPL version 3 section 7
 * 
 * If you modify this Program, or any covered work, by linking or combining
 * it with the OpenSSL library (or a modified version of that library), 
 * containing parts covered by the terms of the OpenSSL Licence and the
 * SSLeay license, the licensors of this Program grant you additional
 * permission to convey the resulting work. Corresponding Source for a
 * non-source form of such a combination shall include the source code
 * for the parts of the OpenSSL library used as well as that of the covered
 * work.
 */
#ifndef PACKET_H
#define PACKET_H

#include <pcap.h>
#include <stdint.h>
#include <stdlib.h>
#include <netinet/in.h>

/* Ethernet addresses are 6 bytes */
#define ETHER_ADDR_LEN	6
#define ETHER_HEADER_LEN  2*ETHER_ADDR_LEN + 2

/* Definitions for parsing packet data */
struct ip_header {
    u_char versionihl;		/* Version >> 4 | IHL & 0x0f */
    u_char dscpecn;		/* DSCP >> 2 | ECN  & 0x03 */
    u_short len;		/* Total Length */
    u_short id;		/* Identification */
    u_short flagsoff;		/* Flags >> 13 | Fragment Offset & 0x1fff */
#define RF 0x8000		/* Reserved; must be zero */
#define DF 0x4000		/* Dont Fragment */
#define MF 0x2000		/* More Fragments */
    u_char ttl;		/* Time To Live */
    u_char proto;		/* Protocol */
    u_short chksum;		/* Header Checksum */
    struct in_addr src, dst; /* Source and Destination addresses */
};
#define IP_HEADER_LEN(ip)		(((ip)->versionihl) & 0x0f)*4

struct tcp_header {
    u_short src_port;	/* source port */
    u_short dst_port;	/* destination port */
    u_int sequence_num;		/* sequence number */
    u_int ack_num;		/* acknowledgement number */
    u_char offset_res_ns;	/*Data offset >> 4 |  res >> 1 | NS 0x01 */
    u_char flags;			/* Flags */
#define FIN 0x01
#define RST 0x04
    u_short win_size;		/* Window size*/
    u_short chksum;		/* Checksum */
    u_short urg;		/* Urgent pointer */
};
#define TCP_HEADER_LEN(tcp)		(((tcp)->offset_res_ns) >> 4)*4

struct tls_header {
    u_char type; /* Content Type */
#define CCS 0x14
#define ALERT   0x15
#define HS  0x16
#define APP 0x17
#define HB  0x18
    u_short version; /* Version */
    u_short len; /* Length */
    u_char msg; /* Message Type */
#define CLIENT_HELLO 0x01
#define FINISHED 0x14
};
#define RECORD_HEADER_LEN 5
#define CLIENT_HELLO_HEADER_LEN 6

struct __attribute__((__packed__)) slitheen_header {
    uint64_t counter;
    uint16_t stream_id; /* determines which stream the data is from */
    uint16_t len;
    uint16_t garbage;
    uint16_t zeros;
};

#define SLITHEEN_HEADER_LEN 16

struct __attribute__((__packed__)) record_header {
    u_char type;
#define HS 0x16
    u_short version;
    u_short len;
};
#define RECORD_LEN(rec)		(htons(rec->len))

struct __attribute__((__packed__)) handshake_header {
    u_char type; /*Handshake message type */
    u_char len1;
    u_char len2;
    u_char len3;
};
#define HANDSHAKE_MESSAGE_LEN(hs)		(((hs)->len1) << 16)+(((hs)->len2) << 8)+ ((hs)->len3)
#define HANDSHAKE_HEADER_LEN 4
struct packet_info {
    const struct ip_header *ip_hdr;
    struct tcp_header *tcp_hdr;
    const struct tls_header *record_hdr;

    uint32_t size_tcp_hdr;
    uint32_t size_ip_hdr;

    uint8_t *app_data;
    uint16_t app_data_len;
};

struct inject_args {
    uint8_t *mac_addr;
    pcap_t *write_dev;
};

void extract_packet_headers(uint8_t *packet, struct packet_info *info);
struct packet_info *copy_packet_info(struct packet_info *src_info);

void inject_packet(struct inject_args *iargs, const struct pcap_pkthdr *header, uint8_t *packet);
#endif /* PACKET_H */