/*************************************************************************** * TCPHeader.cc -- The TCPHeader Class represents a TCP packet. It * * contains methods to set the different header fields. These methods * * tipically perform the necessary error checks and byte order * * conversions. * * * ***********************IMPORTANT NMAP LICENSE TERMS************************ * * * The Nmap Security Scanner is (C) 1996-2011 Insecure.Com LLC. Nmap is * * also a registered trademark of Insecure.Com LLC. This program is free * * software; you may redistribute and/or modify it under the terms of the * * GNU General Public License as published by the Free Software * * Foundation; Version 2 with the clarifications and exceptions described * * below. This guarantees your right to use, modify, and redistribute * * this software under certain conditions. If you wish to embed Nmap * * technology into proprietary software, we sell alternative licenses * * (contact sales@insecure.com). 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See the GNU * * General Public License v2.0 for more details at * * http://www.gnu.org/licenses/gpl-2.0.html , or in the COPYING file * * included with Nmap. * * * ***************************************************************************/ #include "TCPHeader.h" #include "nping.h" #include "common.h" #include "../libnetutil/netutil.h" TCPHeader::TCPHeader(){ this->reset(); } /* End of TCPHeader constructor */ TCPHeader::~TCPHeader(){ } /* End of TCPHeader destructor */ /** Sets every attribute to its default value- */ void TCPHeader::reset(){ memset(&this->h, 0, sizeof(nping_tcp_hdr_t)); this->length=20; /* Initial value 20. This will be incremented if options are used */ this->tcpoptlen=0; } /* End of reset() */ /** @warning This method is essential for the superclass getBinaryBuffer() * method to work. Do NOT change a thing unless you know what you're doing */ u8 * TCPHeader::getBufferPointer(){ return (u8*)(&h); } /* End of getBufferPointer() */ /** Stores supplied packet in the internal buffer so the information * can be accessed using the standard get & set methods. * @warning The TCPHeader class is able to hold a maximum of 60 bytes. If the * supplied buffer is longer than that, only the first 60 bytes will be stored * in the internal buffer. * @warning Supplied len MUST be at least 20 bytes (min TCP header length). * @return OP_SUCCESS on success and OP_FAILURE in case of error */ int TCPHeader::storeRecvData(const u8 *buf, size_t len){ if(buf==NULL || lenreset(); /* Re-init the object, just in case the caller had used it already */ this->length=stored_len; memcpy(&(this->h), buf, stored_len); } return OP_SUCCESS; } /* End of storeRecvData() */ /** Performs some VERY BASIC checks that intend to validate the information * stored in the internal buffer, as a valid protocol header. * @warning If the information stored in the object has been set through a * call to storeRecvData(), the object's internal length count may be updated * if the validation is successful. * @return the length, in bytes, of the header, if its found to be valid or * OP_FAILURE (-1) otherwise. */ int TCPHeader::validate(){ if(this->getOffset()<5) return OP_FAILURE; else if(this->getOffset()*4 > this->length) return OP_FAILURE; this->length=this->getOffset()*4; return this->length; } /* End of validate() */ /** Sets source port. * @warning Port must be supplied in host byte order. This method performs * byte order conversion using htons() */ int TCPHeader::setSrcPort(u16 p){ h.th_sport = htons(p); return OP_SUCCESS; } /* End of setSrcPort() */ /** Returns source port in HOST byte order */ u16 TCPHeader::getSrcPort(){ return ntohs(h.th_sport); } /* End of getSrcPort() */ /** Sets destination port. * @warning Port must be supplied in host byte order. This method performs * byte order conversion using htons() */ int TCPHeader::setDstPort(u16 p){ h.th_dport = htons(p); return OP_SUCCESS; } /* End of setDstPort() */ /** Returns destination port in HOST byte order */ u16 TCPHeader::getDstPort(){ return ntohs(h.th_dport); } /* End of getDstPort() */ /** Sets sequence number. * @warning Seq number must be supplied in host byte order. This method * performs byte order conversion using htonl() */ int TCPHeader::setSeq(u32 p){ h.th_seq = htonl(p); return OP_SUCCESS; } /* End of setSeq() */ /** Returns sequence number in HOST byte order */ u32 TCPHeader::getSeq(){ return ntohl(h.th_seq); } /* End of getSeq() */ /** Sets acknowledgement number. * @warning ACK number must be supplied in host byte order. This method * performs byte order conversion using htonl() */ int TCPHeader::setAck(u32 p){ h.th_ack = htonl(p); return OP_SUCCESS; } /* End of setAck() */ /** Returns ACK number in HOST byte order */ u32 TCPHeader::getAck(){ return ntohl(h.th_ack); } /* End of getAck() */ /* TODO: Test this method. It may not work becuasse th_off is supposed to * be 4 bits long and arg o is 8. * UPDATE: It seems to work just fine. However, let's keep this note just * in case problems arise. */ int TCPHeader::setOffset(u8 o){ h.th_off = o; return OP_SUCCESS; } /* End of setOffset() */ int TCPHeader::setOffset(){ h.th_off = 5 + tcpoptlen/4; return OP_SUCCESS; } /* End of setOffset() */ /** Returns offset value */ u8 TCPHeader::getOffset(){ return h.th_off; } /* End of getOffset() */ /** Sets TCP flags */ int TCPHeader::setFlags(u8 f){ h.th_flags = f; return OP_SUCCESS; } /* End of setFlags() */ /** Returns the 8bit flags field of the TCP header */ u8 TCPHeader::getFlags(){ return h.th_flags; } /* End of getFlags() */ /** Sets flag CWR * @return Previous state of the flag */ bool TCPHeader::setCWR(){ u8 prev = h.th_flags & TH_CWR; h.th_flags |= TH_CWR; return prev; } /* End of setCWR() */ /** Unsets flag CWR * @return Previous state of the flag */ bool TCPHeader::unsetCWR(){ u8 prev = h.th_flags & TH_CWR; h.th_flags ^= TH_CWR; return prev; } /* End of unsetCWR() */ /** Get CWR flag */ bool TCPHeader::getCWR(){ return h.th_flags & TH_CWR; } /* End of getCWR() */ /** Sets flag ECE/ECN * @return Previous state of the flag */ bool TCPHeader::setECE(){ u8 prev = h.th_flags & TH_ECN; h.th_flags |= TH_ECN; return prev; } /* End of setECE() */ /** Unsets flag ECE/ECN * @return Previous state of the flag */ bool TCPHeader::unsetECE(){ u8 prev = h.th_flags & TH_ECN; h.th_flags ^= TH_ECN; return prev; } /* End of unsetECE() */ /** Get CWR flag */ bool TCPHeader::getECE(){ return h.th_flags & TH_ECN; } /* End of getECE() */ /** Same as setECE() but with a different name since there are two possible * ways to call this flag * @return Previous state of the flag */ bool TCPHeader::setECN(){ u8 prev = h.th_flags & TH_ECN; h.th_flags |= TH_ECN; return prev; } /* End of setECN() */ /** Unsets flag ECE/ECN * @return Previous state of the flag */ bool TCPHeader::unsetECN(){ u8 prev = h.th_flags & TH_ECN; h.th_flags ^= TH_ECN; return prev; } /* End of unsetECN() */ /** Get ECN flag */ bool TCPHeader::getECN(){ return h.th_flags & TH_ECN; } /* End of getECN() */ /** Sets flag URG * @return Previous state of the flag */ bool TCPHeader::setURG(){ u8 prev = h.th_flags & TH_URG; h.th_flags |= TH_URG; return prev; } /* End of setURG() */ /** Unsets flag URG * @return Previous state of the flag */ bool TCPHeader::unsetURG(){ u8 prev = h.th_flags & TH_URG; h.th_flags ^= TH_URG; return prev; } /* End of unsetURG() */ /** Get URG flag */ bool TCPHeader::getURG(){ return h.th_flags & TH_URG; } /* End of getURG() */ /** Sets flag ACK * @return Previous state of the flag */ bool TCPHeader::setACK(){ u8 prev = h.th_flags & TH_ACK; h.th_flags |= TH_ACK; return prev; } /* End of setACK() */ /** Unsets flag ACK * @return Previous state of the flag */ bool TCPHeader::unsetACK(){ u8 prev = h.th_flags & TH_ACK; h.th_flags ^= TH_ACK; return prev; } /* End of unsetACK() */ /** Get ACK flag */ bool TCPHeader::getACK(){ return h.th_flags & TH_ACK; } /* End of getACK() */ /** Sets flag PUSH * @return Previous state of the flag */ bool TCPHeader::setPUSH(){ u8 prev = h.th_flags & TH_PUSH; h.th_flags |= TH_PUSH; return prev; } /* End of setPUSH() */ /** Unsets flag PUSH * @return Previous state of the flag */ bool TCPHeader::unsetPUSH(){ u8 prev = h.th_flags & TH_PUSH; h.th_flags ^= TH_PUSH; return prev; } /* End of unetPUSH() */ /** Get PUSH flag */ bool TCPHeader::getPUSH(){ return h.th_flags & TH_PUSH; } /* End of getPUSH() */ /** Sets flag RST * @return Previous state of the flag */ bool TCPHeader::setRST(){ u8 prev = h.th_flags & TH_RST; h.th_flags |= TH_RST; return prev; } /* End of setRST() */ /** Unsets flag RST * @return Previous state of the flag */ bool TCPHeader::unsetRST(){ u8 prev = h.th_flags & TH_RST; h.th_flags ^= TH_RST; return prev; } /* End of unsetRST() */ /** Get RST flag */ bool TCPHeader::getRST(){ return h.th_flags & TH_RST; } /* End of getRST() */ /** Sets flag SYN * @return Previous state of the flag */ bool TCPHeader::setSYN(){ u8 prev = h.th_flags & TH_SYN; h.th_flags |= TH_SYN; return prev; } /* End of setSYN() */ /** Unsets flag SYN * @return Previous state of the flag */ bool TCPHeader::unsetSYN(){ u8 prev = h.th_flags & TH_SYN; h.th_flags ^= TH_SYN; return prev; } /* End of unsetSYN() */ /** Get SYN flag */ bool TCPHeader::getSYN(){ return h.th_flags & TH_SYN; } /* End of getSYN() */ /** Sets flag FIN * @return Previous state of the flag */ bool TCPHeader::setFIN(){ u8 prev = h.th_flags & TH_FIN; h.th_flags |= TH_FIN; return prev; } /* End of setFIN() */ /** Unsets flag FIN * @return Previous state of the flag */ bool TCPHeader::unsetFIN(){ u8 prev = h.th_flags & TH_FIN; h.th_flags ^= TH_FIN; return prev; } /* End of unsetFIN() */ /** Get FIN flag */ bool TCPHeader::getFIN(){ return h.th_flags & TH_FIN; } /* End of getFIN() */ /** Sets window size. * @warning Win number must be supplied in host byte order. This method * performs byte order conversion using htons() */ int TCPHeader::setWindow(u16 p){ h.th_win = htons(p); return OP_SUCCESS; } /* End of setWindow() */ /** Returns window size in HOST byte order. */ u16 TCPHeader::getWindow(){ return ntohs(h.th_win); } /* End of getWindow() */ /** Sets urgent pointer. * @warning Pointer must be supplied in host byte order. This method * performs byte order conversion using htons() */ int TCPHeader::setUrgPointer(u16 l){ h.th_urp = htons(l); return OP_SUCCESS; } /* End of setUrgPointer() */ /** Returns Urgent Pointer in HOST byte order. */ u16 TCPHeader::getUrgPointer(){ return ntohs(h.th_urp); } /* End of getUrgPointer() */ int TCPHeader::setSum(struct in_addr src, struct in_addr dst){ int bufflen; u8 aux[ MAX_TCP_PAYLOAD_LEN ]; /* FROM: RFC 1323: TCP Extensions for High Performance, March 4, 2009 * * "With IP Version 4, the largest amount of TCP data that can be sent in * a single packet is 65495 bytes (64K - 1 - size of fixed IP and TCP * headers)". * * In theory TCP should not worry about the practical max payload length * because it is supposed to be independent of the network layer. However, * since TCP does not have any length field and we need to allocate a * buffer, we are using that value. (Note htat in UDPHeader.cc we do just * the opposite, forget about the practical limitation and allow the * theorical limit for the payload. */ h.th_sum = 0; /* Copy packet contents to a buffer */ bufflen=dumpToBinaryBuffer(aux, MAX_TCP_PAYLOAD_LEN); /* Compute checksum */ h.th_sum = tcpudp_cksum(&src, &dst, IPPROTO_TCP, bufflen, (char *)aux); return OP_SUCCESS; } /* End of setSum() */ /** @warning Sum is set to supplied value with NO byte ordering conversion * performed. */ int TCPHeader::setSum(u16 s){ h.th_sum = s; return OP_SUCCESS; } /* End of setSum() */ /** Set the TCP checksum field to a random value, which may accidentally * match the correct checksum */ int TCPHeader::setSumRandom(){ h.th_sum=get_random_u16(); return OP_SUCCESS; } /* End of setSumRandom() */ /** Set the TCP checksum field to a random value. It takes the source and * destination address to make sure the random generated sum does not * accidentally match the correct checksum. This function only handles * IPv4 address. */ int TCPHeader::setSumRandom(struct in_addr source, struct in_addr destination){ u16 correct_csum=0; /* Compute the correct checksum */ this->setSum(source, destination); correct_csum=this->getSum(); /* Generate numbers until one does not match the correct sum */ while( (h.th_sum=get_random_u16())==correct_csum); return OP_SUCCESS; } /* End of setSumRandom() */ /** Returns the TCP checksum field in NETWORK byte order */ u16 TCPHeader::getSum(){ return h.th_sum; } /* End of getSum() */