diff options
Diffstat (limited to 'src/libnet_build_tcp.c')
| -rw-r--r-- | src/libnet_build_tcp.c | 307 |
1 files changed, 307 insertions, 0 deletions
diff --git a/src/libnet_build_tcp.c b/src/libnet_build_tcp.c new file mode 100644 index 0000000..2697d28 --- /dev/null +++ b/src/libnet_build_tcp.c @@ -0,0 +1,307 @@ +/* + * $Id: libnet_build_tcp.c,v 1.11 2004/01/28 19:45:00 mike Exp $ + * + * libnet + * libnet_build_tcp.c - TCP packet assembler + * + * Copyright (c) 1998 - 2004 Mike D. Schiffman <mike@infonexus.com> + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + */ + +#include "common.h" + +libnet_ptag_t +libnet_build_tcp( + uint16_t sp, uint16_t dp, uint32_t seq, uint32_t ack, + uint8_t control, uint16_t win, uint16_t sum, uint16_t urg, uint16_t h_len, + const uint8_t *payload, uint32_t payload_s, libnet_t *l, libnet_ptag_t ptag) +{ + int n, offset; + libnet_pblock_t *p = NULL; + libnet_ptag_t ptag_data = 0; + struct libnet_tcp_hdr tcp_hdr; + + if (l == NULL) + return -1; + + if (payload_s && !payload) + { + snprintf(l->err_buf, LIBNET_ERRBUF_SIZE, + "%s(): payload inconsistency", __func__); + return -1; + } + + p = libnet_pblock_probe(l, ptag, LIBNET_TCP_H, LIBNET_PBLOCK_TCP_H); + if (p == NULL) + return -1; + + memset(&tcp_hdr, 0, sizeof(tcp_hdr)); + tcp_hdr.th_sport = htons(sp); /* source port */ + tcp_hdr.th_dport = htons(dp); /* destination port */ + tcp_hdr.th_seq = htonl(seq); /* sequence number */ + tcp_hdr.th_ack = htonl(ack); /* acknowledgement number */ + tcp_hdr.th_flags = control; /* control flags */ + tcp_hdr.th_x2 = 0; /* UNUSED */ + tcp_hdr.th_off = 5; /* 20 byte header */ + + /* check to see if there are TCP options to include */ + if (p->prev && p->prev->type == LIBNET_PBLOCK_TCPO_H) + { + /* Note that the tcp options pblock is already padded */ + tcp_hdr.th_off += (p->prev->b_len/4); + } + + tcp_hdr.th_win = htons(win); /* window size */ + tcp_hdr.th_sum = (sum ? htons(sum) : 0); /* checksum */ + tcp_hdr.th_urp = htons(urg); /* urgent pointer */ + + n = libnet_pblock_append(l, p, (uint8_t *)&tcp_hdr, LIBNET_TCP_H); + if (n == -1) + { + goto bad; + } + + if (ptag == LIBNET_PTAG_INITIALIZER) + { + libnet_pblock_update(l, p, h_len, LIBNET_PBLOCK_TCP_H); + } + + offset = payload_s; + + /* If we are going to modify a TCP data block, find it, and figure out the + * "offset", the possibly negative amount by which we are increasing the ip + * data length. */ + if (ptag) + { + libnet_pblock_t* datablock = p->prev; + + if (datablock && datablock->type == LIBNET_PBLOCK_TCPO_H) + datablock = datablock->prev; + + if (datablock && datablock->type == LIBNET_PBLOCK_TCPDATA) + { + ptag_data = datablock->ptag; + offset -= datablock->b_len; + } + p->h_len += offset; + } + + /* If we are modifying a TCP block, we should look forward and apply the offset + * to our IPv4 header, if we have one. + */ + if (p->next) + { + libnet_pblock_t* ipblock = p->next; + + if(ipblock->type == LIBNET_PBLOCK_IPO_H) + ipblock = ipblock->next; + + if(ipblock && ipblock->type == LIBNET_PBLOCK_IPV4_H) + { + struct libnet_ipv4_hdr * ip_hdr = (struct libnet_ipv4_hdr *)ipblock->buf; + int ip_len = ntohs(ip_hdr->ip_len) + offset; + ip_hdr->ip_len = htons(ip_len); + } + } + + /* if there is a payload, add it in the context */ + if (payload_s) + { + /* update ptag_data with the new payload */ + libnet_pblock_t* p_data = libnet_pblock_probe(l, ptag_data, payload_s, LIBNET_PBLOCK_TCPDATA); + if (!p_data) + { + goto bad; + } + + n = libnet_pblock_append(l, p_data, payload, payload_s); + if (n == -1) + { + goto bad; + } + + if (ptag_data == LIBNET_PTAG_INITIALIZER) + { + int insertbefore = p->ptag; + + /* Then we created it, and we need to shuffle it back until it's before + * the tcp header and options. */ + libnet_pblock_update(l, p_data, payload_s, LIBNET_PBLOCK_TCPDATA); + + if(p->prev && p->prev->type == LIBNET_PBLOCK_TCPO_H) + insertbefore = p->prev->ptag; + + libnet_pblock_insert_before(l, insertbefore, p_data->ptag); + } + } + else + { + libnet_pblock_t* p_data = libnet_pblock_find(l, ptag_data); + libnet_pblock_delete(l, p_data); + } + + if (sum == 0) + { + /* + * If checksum is zero, by default libnet will compute a checksum + * for the user. The programmer can override this by calling + * libnet_toggle_checksum(l, ptag, 1); + */ + libnet_pblock_setflags(p, LIBNET_PBLOCK_DO_CHECKSUM); + } + return (p->ptag); +bad: + libnet_pblock_delete(l, p); + return (-1); +} + +libnet_ptag_t +libnet_build_tcp_options(const uint8_t *options, uint32_t options_s, libnet_t *l, +libnet_ptag_t ptag) +{ + static const uint8_t padding[] = { 0 }; + int n, offset, underflow; + uint32_t i, j, adj_size; + libnet_pblock_t *p, *p_temp; + struct libnet_ipv4_hdr *ip_hdr; + struct libnet_tcp_hdr *tcp_hdr; + + if (l == NULL) + { + return (-1); + } + + underflow = 0; + offset = 0; + + /* check options list size */ + if (options_s > LIBNET_MAXOPTION_SIZE) + { + snprintf(l->err_buf, LIBNET_ERRBUF_SIZE, + "%s(): options list is too large %d", __func__, options_s); + return (-1); + } + + adj_size = options_s; + if (adj_size % 4) + { + /* size of memory block with padding */ + adj_size += 4 - (options_s % 4); + } + + /* if this pblock already exists, determine if there is a size diff */ + if (ptag) + { + p_temp = libnet_pblock_find(l, ptag); + if (p_temp) + { + if (adj_size >= p_temp->b_len) + { + offset = adj_size - p_temp->b_len; + } + else + { + offset = p_temp->b_len - adj_size; + underflow = 1; + } + } + } + + /* + * Find the existing protocol block if a ptag is specified, or create + * a new one. + */ + p = libnet_pblock_probe(l, ptag, adj_size, LIBNET_PBLOCK_TCPO_H); + if (p == NULL) + { + return (-1); + } + + n = libnet_pblock_append(l, p, options, options_s); + if (n == -1) + { + goto bad; + } + + n = libnet_pblock_append(l, p, padding, adj_size - options_s); + if (n == -1) + { + goto bad; + } + + if (ptag && p->next) + { + p_temp = p->next; + while ((p_temp->next) && (p_temp->type != LIBNET_PBLOCK_TCP_H)) + { + p_temp = p_temp->next; + } + if (p_temp->type == LIBNET_PBLOCK_TCP_H) + { + /* + * Count up number of 32-bit words in options list, padding if + * neccessary. + */ + for (i = 0, j = 0; i < p->b_len; i++) + { + (i % 4) ? j : j++; + } + tcp_hdr = (struct libnet_tcp_hdr *)p_temp->buf; + tcp_hdr->th_off = j + 5; + if (!underflow) + { + p_temp->h_len += offset; + } + else + { + p_temp->h_len -= offset; + } + } + while ((p_temp->next) && (p_temp->type != LIBNET_PBLOCK_IPV4_H)) + { + p_temp = p_temp->next; + } + if (p_temp->type == LIBNET_PBLOCK_IPV4_H) + { + ip_hdr = (struct libnet_ipv4_hdr *)p_temp->buf; + if (!underflow) + { + ip_hdr->ip_len += htons(offset); + } + else + { + ip_hdr->ip_len -= htons(offset); + } + } + } + + return (ptag ? ptag : libnet_pblock_update(l, p, adj_size, + LIBNET_PBLOCK_TCPO_H)); +bad: + libnet_pblock_delete(l, p); + return (-1); +} + +/* EOF */ |