/*************************************************************************** * 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). Dozens of software vendors already * * license Nmap technology such as host discovery, port scanning, OS * * detection, and version detection. * * * * Note that the GPL places important restrictions on "derived works", yet * * it does not provide a detailed definition of that term. To avoid * * misunderstandings, we consider an application to constitute a * * "derivative work" for the purpose of this license if it does any of the * * following: * * o Integrates source code from Nmap * * o Reads or includes Nmap copyrighted data files, such as * * nmap-os-db or nmap-service-probes. * * o Executes Nmap and parses the results (as opposed to typical shell or * * execution-menu apps, which simply display raw Nmap output and so are * * not derivative works.) * * o Integrates/includes/aggregates Nmap into a proprietary executable * * installer, such as those produced by InstallShield. * * o Links to a library or executes a program that does any of the above * * * * The term "Nmap" should be taken to also include any portions or derived * * works of Nmap. This list is not exclusive, but is meant to clarify our * * interpretation of derived works with some common examples. Our * * interpretation applies only to Nmap--we don't speak for other people's * * GPL works. * * * * If you have any questions about the GPL licensing restrictions on using * * Nmap in non-GPL works, we would be happy to help. As mentioned above, * * we also offer alternative license to integrate Nmap into proprietary * * applications and appliances. These contracts have been sold to dozens * * of software vendors, and generally include a perpetual license as well * * as providing for priority support and updates as well as helping to * * fund the continued development of Nmap technology. Please email * * sales@insecure.com for further information. * * * * As a special exception to the GPL terms, Insecure.Com LLC grants * * permission to link the code of this program with any version of the * * OpenSSL library which is distributed under a license identical to that * * listed in the included docs/licenses/OpenSSL.txt file, and distribute * * linked combinations including the two. 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By sending these changes to Fyodor or one of the * * Insecure.Org development mailing lists, it is assumed that you are * * offering the Nmap Project (Insecure.Com LLC) the unlimited, * * non-exclusive right to reuse, modify, and relicense the code. Nmap * * will always be available Open Source, but this is important because the * * inability to relicense code has caused devastating problems for other * * Free Software projects (such as KDE and NASM). We also occasionally * * relicense the code to third parties as discussed above. If you wish to * * specify special license conditions of your contributions, just say so * * when you send them. * * * * 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 v2.0 for more details at * * http://www.gnu.org/licenses/gpl-2.0.html , or in the COPYING file * * included with Nmap. * * * ***************************************************************************/ /* This code was originally part of the Nping tool. */ #include "TCPHeader.h" #include /******************************************************************************/ /* CONTRUCTORS, DESTRUCTORS AND INITIALIZATION METHODS */ /******************************************************************************/ 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() */ /******************************************************************************/ /* PacketElement:: OVERWRITTEN METHODS */ /******************************************************************************/ /** @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; if(stored_len>TCP_HEADER_LEN) this->tcpoptlen=stored_len-TCP_HEADER_LEN; memcpy(&(this->h), buf, stored_len); } return OP_SUCCESS; } /* End of storeRecvData() */ /* Returns a protocol identifier. This is used by packet parsing funtions * that return linked lists of PacketElement objects, to determine the protocol * the object represents. */ int TCPHeader::protocol_id(){ return HEADER_TYPE_TCP; } /* End of protocol_id() */ /** Determines if the data stored in the object after an storeRecvData() call * is valid and safe to use. This mainly checks the length of the data but may * also test the value of certain protocol fields to ensure their correctness. * @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() */ /** Prints the contents of the header and calls print() on the next protocol * header in the chain (if there is any). * @return OP_SUCCESS on success and OP_FAILURE in case of error. */ int TCPHeader::print(FILE *output, int detail){ char optinfo[256]; fprintf(output, "TCP["); fprintf(output, "%d", this->getSourcePort()); fprintf(output, " >"); fprintf(output, " %d", this->getDestinationPort()); fprintf(output, " %s%s%s%s%s%s%s%s", !this->getSYN() ? "" : "S", !this->getFIN() ? "" : "F", !this->getRST() ? "" : "R", !this->getPUSH() ? "" : "P", !this->getACK() ? "" : "A", !this->getURG() ? "" : "U", !this->getECN() ? "" : "E", !this->getCWR() ? "" : "C" ); fprintf(output, " seq=%lu", (long unsigned int)this->getSeq() ); if(detail>=PRINT_DETAIL_HIGH){ fprintf(output, " ack=%lu", (long unsigned int)this->getAck() ); fprintf(output, " off=%d", this->getOffset() ); fprintf(output, " res=%d", this->h.th_x2); } fprintf(output, " win=%hu", this->getWindow() ); if(detail>=PRINT_DETAIL_MED) fprintf(output, " csum=0x%04X", ntohs( this->getSum() )); if(detail>=PRINT_DETAIL_HIGH) fprintf(output, " urp=%d", this->getUrgPointer() ); if(this->tcpoptlen>0 && (this->length >= TCP_HEADER_LEN+this->tcpoptlen) && this->tcpoptlen<=MAX_TCP_OPTIONS_LEN){ this->__tcppacketoptinfo(this->h.options, this->tcpoptlen, optinfo, sizeof(optinfo)-1); optinfo[255]='\0'; fprintf(output, " %s", optinfo); } fprintf(output, "]"); if(this->next!=NULL){ print_separator(output, detail); next->print(output, detail); } return OP_SUCCESS; } /* End of print() */ /* Get an ASCII information about a tcp option which is pointed by optp, with a length of len. The result is stored in the result buffer. The result may look like "" */ void TCPHeader::__tcppacketoptinfo(u8 *optp, int len, char *result, int bufsize){ assert(optp); assert(result); char *p, ch; u8 *q; int opcode; u16 tmpshort; u32 tmpword1, tmpword2; unsigned int i=0; p = result; *p = '\0'; q = optp; ch = '<'; while (len > 0 && bufsize > 2) { Snprintf(p, bufsize, "%c", ch); bufsize--; p++; opcode = *q++; if (!opcode) { /* End of List */ Snprintf(p, bufsize, "eol"); bufsize -= strlen(p); p += strlen(p); len--; } else if (opcode == 1) { /* No Op */ Snprintf(p, bufsize, "nop"); bufsize -= strlen(p); p += strlen(p); len--; } else if (opcode == 2) { /* MSS */ if (len < 4) break; /* MSS has 4 bytes */ q++; memcpy(&tmpshort, q, 2); Snprintf(p, bufsize, "mss %u", ntohs(tmpshort)); bufsize -= strlen(p); p += strlen(p); q += 2; len -= 4; } else if (opcode == 3) { /* Window Scale */ if (len < 3) break; /* Window Scale option has 3 bytes */ q++; Snprintf(p, bufsize, "wscale %u", *q); bufsize -= strlen(p); p += strlen(p); q++; len -= 3; } else if (opcode == 4) { /* SACK permitted */ if (len < 2) break; /* SACK permitted option has 2 bytes */ Snprintf(p, bufsize, "sackOK"); bufsize -= strlen(p); p += strlen(p); q++; len -= 2; } else if (opcode == 5) { /* SACK */ unsigned sackoptlen = *q; if ((unsigned) len < sackoptlen) break; /* This would break parsing, so it's best to just give up */ if (sackoptlen < 2) break; q++; if ((sackoptlen - 2) == 0 || ((sackoptlen - 2) % 8 != 0)) { Snprintf(p, bufsize, "malformed sack"); bufsize -= strlen(p); p += strlen(p); } else { Snprintf(p, bufsize, "sack %d ", (sackoptlen - 2) / 8); bufsize -= strlen(p); p += strlen(p); for (i = 0; i < sackoptlen - 2; i += 8) { memcpy(&tmpword1, q + i, 4); memcpy(&tmpword2, q + i + 4, 4); Snprintf(p, bufsize, "{%u:%u}", tmpword1, tmpword2); bufsize -= strlen(p); p += strlen(p); } } q += sackoptlen - 2; len -= sackoptlen; } else if (opcode == 8) { /* Timestamp */ if (len < 10) break; /* Timestamp option has 10 bytes */ q++; memcpy(&tmpword1, q, 4); memcpy(&tmpword2, q + 4, 4); Snprintf(p, bufsize, "timestamp %u %u", ntohl(tmpword1), ntohl(tmpword2)); bufsize -= strlen(p); p += strlen(p); q += 8; len -= 10; } ch = ','; } if (len > 0) { *result = '\0'; return; } Snprintf(p, bufsize, ">"); } /******************************************************************************/ /* PROTOCOL-SPECIFIC METHODS */ /******************************************************************************/ /** Sets source port. * @warning Port must be supplied in host byte order. This method performs * byte order conversion using htons() */ int TCPHeader::setSourcePort(u16 p){ h.th_sport = htons(p); return OP_SUCCESS; } /* End of setSourcePort() */ /** Returns source port in HOST byte order */ u16 TCPHeader::getSourcePort(){ return ntohs(h.th_sport); } /* End of getSourcePort() */ /** Sets destination port. * @warning Port must be supplied in host byte order. This method performs * byte order conversion using htons() */ int TCPHeader::setDestinationPort(u16 p){ h.th_dport = htons(p); return OP_SUCCESS; } /* End of setDestinationPort() */ /** Returns destination port in HOST byte order */ u16 TCPHeader::getDestinationPort(){ return ntohs(h.th_dport); } /* End of getDestinationPort() */ /** 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 = ipv4_pseudoheader_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() */