/* Copyright (C) 2007-2022 Open Information Security Foundation * * You can copy, redistribute or modify this Program under the terms of * the GNU General Public License version 2 as published by the Free * Software Foundation. * * 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 * version 2 along with this program; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA * 02110-1301, USA. */ /** * \file * * \author Victor Julien * \todo RAW* macro's should be returning the raw value, not the host order */ #ifndef __DECODE_TCP_H__ #define __DECODE_TCP_H__ #define TCP_HEADER_LEN 20 #define TCP_OPTLENMAX 40 #define TCP_OPTMAX 20 /* every opt is at least 2 bytes * (type + len), except EOL and NOP */ /* TCP flags */ #define TH_FIN 0x01 #define TH_SYN 0x02 #define TH_RST 0x04 #define TH_PUSH 0x08 #define TH_ACK 0x10 #define TH_URG 0x20 /** Establish a new connection reducing window */ #define TH_ECN 0x40 /** Echo Congestion flag */ #define TH_CWR 0x80 /* tcp option codes */ #define TCP_OPT_EOL 0x00 #define TCP_OPT_NOP 0x01 #define TCP_OPT_MSS 0x02 #define TCP_OPT_WS 0x03 #define TCP_OPT_SACKOK 0x04 #define TCP_OPT_SACK 0x05 #define TCP_OPT_TS 0x08 #define TCP_OPT_TFO 0x22 /* TCP Fast Open */ #define TCP_OPT_EXP1 0xfd /* Experimental, could be TFO */ #define TCP_OPT_EXP2 0xfe /* Experimental, could be TFO */ #define TCP_OPT_MD5 0x13 /* 19: RFC 2385 TCP MD5 option */ #define TCP_OPT_AO 0x1d /* 29: RFC 5925 TCP AO option */ #define TCP_OPT_SACKOK_LEN 2 #define TCP_OPT_WS_LEN 3 #define TCP_OPT_TS_LEN 10 #define TCP_OPT_MSS_LEN 4 #define TCP_OPT_SACK_MIN_LEN 10 /* hdr 2, 1 pair 8 = 10 */ #define TCP_OPT_SACK_MAX_LEN 34 /* hdr 2, 4 pair 32= 34 */ #define TCP_OPT_TFO_MIN_LEN 4 /* kind, len, 2 bytes cookie: 4 */ #define TCP_OPT_TFO_MAX_LEN 18 /* kind, len, 18 */ /** Max valid wscale value. */ #define TCP_WSCALE_MAX 14 #define TCP_GET_RAW_OFFSET(tcph) (((tcph)->th_offx2 & 0xf0) >> 4) #define TCP_GET_RAW_X2(tcph) (unsigned char)((tcph)->th_offx2 & 0x0f) #define TCP_GET_RAW_SRC_PORT(tcph) SCNtohs((tcph)->th_sport) #define TCP_GET_RAW_DST_PORT(tcph) SCNtohs((tcph)->th_dport) #define TCP_SET_RAW_TCP_OFFSET(tcph, value) ((tcph)->th_offx2 = (unsigned char)(((tcph)->th_offx2 & 0x0f) | (value << 4))) #define TCP_SET_RAW_TCP_X2(tcph, value) ((tcph)->th_offx2 = (unsigned char)(((tcph)->th_offx2 & 0xf0) | (value & 0x0f))) #define TCP_GET_RAW_SEQ(tcph) SCNtohl((tcph)->th_seq) #define TCP_GET_RAW_ACK(tcph) SCNtohl((tcph)->th_ack) #define TCP_GET_RAW_WINDOW(tcph) SCNtohs((tcph)->th_win) #define TCP_GET_RAW_URG_POINTER(tcph) SCNtohs((tcph)->th_urp) #define TCP_GET_RAW_SUM(tcph) SCNtohs((tcph)->th_sum) /** macro for getting the first timestamp from the packet in host order */ #define TCP_GET_TSVAL(p) ((p)->tcpvars.ts_val) /** macro for getting the second timestamp from the packet in host order. */ #define TCP_GET_TSECR(p) ((p)->tcpvars.ts_ecr) #define TCP_HAS_WSCALE(p) ((p)->tcpvars.ws.type == TCP_OPT_WS) #define TCP_HAS_SACK(p) ((p)->tcpvars.sack.type == TCP_OPT_SACK) #define TCP_HAS_SACKOK(p) ((p)->tcpvars.sackok.type == TCP_OPT_SACKOK) #define TCP_HAS_TS(p) ((p)->tcpvars.ts_set) #define TCP_HAS_MSS(p) ((p)->tcpvars.mss.type == TCP_OPT_MSS) #define TCP_HAS_TFO(p) ((p)->tcpvars.tfo.type == TCP_OPT_TFO) /** macro for getting the wscale from the packet. */ #define TCP_GET_WSCALE(p) (TCP_HAS_WSCALE((p)) ? \ (((*(uint8_t *)(p)->tcpvars.ws.data) <= TCP_WSCALE_MAX) ? \ (*(uint8_t *)((p)->tcpvars.ws.data)) : 0) : 0) #define TCP_GET_SACKOK(p) (TCP_HAS_SACKOK((p)) ? 1 : 0) #define TCP_GET_SACK_PTR(p) TCP_HAS_SACK((p)) ? (p)->tcpvars.sack.data : NULL #define TCP_GET_SACK_CNT(p) (TCP_HAS_SACK((p)) ? (((p)->tcpvars.sack.len - 2) / 8) : 0) #define TCP_GET_MSS(p) SCNtohs(*(uint16_t *)((p)->tcpvars.mss.data)) #define TCP_GET_OFFSET(p) TCP_GET_RAW_OFFSET((p)->tcph) #define TCP_GET_X2(p) TCP_GET_RAW_X2((p)->tcph) #define TCP_GET_HLEN(p) ((uint8_t)(TCP_GET_OFFSET((p)) << 2)) #define TCP_GET_SRC_PORT(p) TCP_GET_RAW_SRC_PORT((p)->tcph) #define TCP_GET_DST_PORT(p) TCP_GET_RAW_DST_PORT((p)->tcph) #define TCP_GET_SEQ(p) TCP_GET_RAW_SEQ((p)->tcph) #define TCP_GET_ACK(p) TCP_GET_RAW_ACK((p)->tcph) #define TCP_GET_WINDOW(p) TCP_GET_RAW_WINDOW((p)->tcph) #define TCP_GET_URG_POINTER(p) TCP_GET_RAW_URG_POINTER((p)->tcph) #define TCP_GET_SUM(p) TCP_GET_RAW_SUM((p)->tcph) #define TCP_GET_FLAGS(p) (p)->tcph->th_flags #define TCP_ISSET_FLAG_FIN(p) ((p)->tcph->th_flags & TH_FIN) #define TCP_ISSET_FLAG_SYN(p) ((p)->tcph->th_flags & TH_SYN) #define TCP_ISSET_FLAG_RST(p) ((p)->tcph->th_flags & TH_RST) #define TCP_ISSET_FLAG_PUSH(p) ((p)->tcph->th_flags & TH_PUSH) #define TCP_ISSET_FLAG_ACK(p) ((p)->tcph->th_flags & TH_ACK) #define TCP_ISSET_FLAG_URG(p) ((p)->tcph->th_flags & TH_URG) #define TCP_ISSET_FLAG_RES2(p) ((p)->tcph->th_flags & TH_RES2) #define TCP_ISSET_FLAG_RES1(p) ((p)->tcph->th_flags & TH_RES1) typedef struct TCPOpt_ { uint8_t type; uint8_t len; const uint8_t *data; } TCPOpt; typedef struct TCPOptSackRecord_ { uint32_t le; /**< left edge, network order */ uint32_t re; /**< right edge, network order */ } TCPOptSackRecord; typedef struct TCPHdr_ { uint16_t th_sport; /**< source port */ uint16_t th_dport; /**< destination port */ uint32_t th_seq; /**< sequence number */ uint32_t th_ack; /**< acknowledgement number */ uint8_t th_offx2; /**< offset and reserved */ uint8_t th_flags; /**< pkt flags */ uint16_t th_win; /**< pkt window */ uint16_t th_sum; /**< checksum */ uint16_t th_urp; /**< urgent pointer */ } __attribute__((__packed__)) TCPHdr; typedef struct TCPVars_ { /* commonly used and needed opts */ bool md5_option_present; bool ao_option_present; bool ts_set; uint32_t ts_val; /* host-order */ uint32_t ts_ecr; /* host-order */ uint16_t stream_pkt_flags; TCPOpt sack; TCPOpt sackok; TCPOpt ws; TCPOpt mss; TCPOpt tfo; /* tcp fast open */ } TCPVars; #define CLEAR_TCP_PACKET(p) { \ (p)->level4_comp_csum = -1; \ PACKET_CLEAR_L4VARS((p)); \ (p)->tcph = NULL; \ } void DecodeTCPRegisterTests(void); /** -------- Inline functions ------- */ /** * \brief Calculate or validate the checksum for the TCP packet * * \param shdr Pointer to source address field from the IP packet. Used as a * part of the pseudoheader for computing the checksum * \param pkt Pointer to the start of the TCP packet * \param tlen Total length of the TCP packet(header + payload) * \param init The current checksum if validating, 0 if generating. * * \retval csum For validation 0 will be returned for success, for calculation * this will be the checksum. */ static inline uint16_t TCPChecksum( const uint16_t *shdr, const uint16_t *pkt, uint16_t tlen, uint16_t init) { uint16_t pad = 0; uint32_t csum = init; csum += shdr[0] + shdr[1] + shdr[2] + shdr[3] + htons(6) + htons(tlen); csum += pkt[0] + pkt[1] + pkt[2] + pkt[3] + pkt[4] + pkt[5] + pkt[6] + pkt[7] + pkt[9]; tlen -= 20; pkt += 10; while (tlen >= 32) { csum += pkt[0] + pkt[1] + pkt[2] + pkt[3] + pkt[4] + pkt[5] + pkt[6] + pkt[7] + pkt[8] + pkt[9] + pkt[10] + pkt[11] + pkt[12] + pkt[13] + pkt[14] + pkt[15]; tlen -= 32; pkt += 16; } while(tlen >= 8) { csum += pkt[0] + pkt[1] + pkt[2] + pkt[3]; tlen -= 8; pkt += 4; } while(tlen >= 4) { csum += pkt[0] + pkt[1]; tlen -= 4; pkt += 2; } while (tlen > 1) { csum += pkt[0]; pkt += 1; tlen -= 2; } if (tlen == 1) { *(uint8_t *)(&pad) = (*(uint8_t *)pkt); csum += pad; } csum = (csum >> 16) + (csum & 0x0000FFFF); csum += (csum >> 16); return (uint16_t)~csum; } /** * \brief Calculate or validate the checksum for the TCP packet * * \param shdr Pointer to source address field from the IPV6 packet. Used as a * part of the psuedoheader for computing the checksum * \param pkt Pointer to the start of the TCP packet * \param tlen Total length of the TCP packet(header + payload) * \param init The current checksum if validating, 0 if generating. * * \retval csum For validation 0 will be returned for success, for calculation * this will be the checksum. */ static inline uint16_t TCPV6Checksum( const uint16_t *shdr, const uint16_t *pkt, uint16_t tlen, uint16_t init) { uint16_t pad = 0; uint32_t csum = init; csum += shdr[0] + shdr[1] + shdr[2] + shdr[3] + shdr[4] + shdr[5] + shdr[6] + shdr[7] + shdr[8] + shdr[9] + shdr[10] + shdr[11] + shdr[12] + shdr[13] + shdr[14] + shdr[15] + htons(6) + htons(tlen); csum += pkt[0] + pkt[1] + pkt[2] + pkt[3] + pkt[4] + pkt[5] + pkt[6] + pkt[7] + pkt[9]; tlen -= 20; pkt += 10; while (tlen >= 32) { csum += pkt[0] + pkt[1] + pkt[2] + pkt[3] + pkt[4] + pkt[5] + pkt[6] + pkt[7] + pkt[8] + pkt[9] + pkt[10] + pkt[11] + pkt[12] + pkt[13] + pkt[14] + pkt[15]; tlen -= 32; pkt += 16; } while(tlen >= 8) { csum += pkt[0] + pkt[1] + pkt[2] + pkt[3]; tlen -= 8; pkt += 4; } while(tlen >= 4) { csum += pkt[0] + pkt[1]; tlen -= 4; pkt += 2; } while (tlen > 1) { csum += pkt[0]; pkt += 1; tlen -= 2; } if (tlen == 1) { *(uint8_t *)(&pad) = (*(uint8_t *)pkt); csum += pad; } csum = (csum >> 16) + (csum & 0x0000FFFF); csum += (csum >> 16); return (uint16_t)~csum; } #endif /* __DECODE_TCP_H__ */