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https://git.libssh.org/projects/libssh.git
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misc: Rename libssh/ to src/
This commit is contained in:
Andreas Schneider
434
src/pcap.c
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434
src/pcap.c
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/*
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* This file is part of the SSH Library
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*
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* Copyright (c) 2009 by Aris Adamantiadis
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*
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* The SSH Library is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 2.1 of the License, or (at your
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* option) any later version.
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*
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* The SSH Library is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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* License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with the SSH Library; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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* MA 02111-1307, USA.
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*/
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/* pcap.c */
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#include "config.h"
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#ifdef WITH_PCAP
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#include <stdio.h>
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#ifdef _WIN32
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#include <ws2tcpip.h>
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#else
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#include <sys/time.h>
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#include <sys/socket.h>
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#endif
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#include <errno.h>
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#include "libssh/libssh.h"
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#include "libssh/pcap.h"
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#include "libssh/session.h"
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#include "libssh/buffer.h"
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#include "libssh/socket.h"
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/**
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* @internal
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*
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* @defgroup libssh_pcap The libssh pcap functions
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* @ingroup libssh
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*
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* The pcap file generation
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*
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*
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* @{
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*/
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/* The header of a pcap file is the following. We are not going to make it
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* very complicated.
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* Just for information.
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*/
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struct pcap_hdr_s {
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uint32_t magic_number; /* magic number */
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uint16_t version_major; /* major version number */
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uint16_t version_minor; /* minor version number */
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int32_t thiszone; /* GMT to local correction */
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uint32_t sigfigs; /* accuracy of timestamps */
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uint32_t snaplen; /* max length of captured packets, in octets */
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uint32_t network; /* data link type */
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};
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#define PCAP_MAGIC 0xa1b2c3d4
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#define PCAP_VERSION_MAJOR 2
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#define PCAP_VERSION_MINOR 4
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#define DLT_RAW 12 /* raw IP */
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/* TCP flags */
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#define TH_FIN 0x01
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#define TH_SYN 0x02
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#define TH_RST 0x04
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#define TH_PUSH 0x08
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#define TH_ACK 0x10
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#define TH_URG 0x20
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/* The header of a pcap packet.
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* Just for information.
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*/
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struct pcaprec_hdr_s {
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uint32_t ts_sec; /* timestamp seconds */
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uint32_t ts_usec; /* timestamp microseconds */
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uint32_t incl_len; /* number of octets of packet saved in file */
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uint32_t orig_len; /* actual length of packet */
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};
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/** @private
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* @brief a pcap context expresses the state of a pcap dump
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* in a SSH session only. Multiple pcap contexts may be used into
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* a single pcap file.
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*/
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struct ssh_pcap_context_struct {
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ssh_session session;
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ssh_pcap_file file;
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int connected;
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/* All of these information are useful to generate
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* the dummy IP and TCP packets
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*/
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uint32_t ipsource;
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uint32_t ipdest;
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uint16_t portsource;
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uint16_t portdest;
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uint32_t outsequence;
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uint32_t insequence;
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};
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/** @private
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* @brief a pcap file expresses the state of a pcap file which may
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* contain several streams.
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*/
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struct ssh_pcap_file_struct {
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FILE *output;
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uint16_t ipsequence;
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};
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/**
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* @brief create a new ssh_pcap_file object
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*/
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ssh_pcap_file ssh_pcap_file_new(){
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struct ssh_pcap_file_struct *pcap;
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pcap = malloc(sizeof(struct ssh_pcap_file_struct));
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if (pcap == NULL) {
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return NULL;
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}
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ZERO_STRUCTP(pcap);
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return pcap;
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}
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/** @internal
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* @brief writes a packet on file
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*/
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static int ssh_pcap_file_write(ssh_pcap_file pcap, ssh_buffer packet){
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int err;
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uint32_t len;
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if(pcap == NULL || pcap->output==NULL)
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return SSH_ERROR;
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len=ssh_buffer_get_len(packet);
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err=fwrite(ssh_buffer_get_begin(packet),len,1,pcap->output);
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if(err<0)
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return SSH_ERROR;
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else
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return SSH_OK;
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}
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/** @internal
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* @brief prepends a packet with the pcap header and writes packet
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* on file
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*/
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int ssh_pcap_file_write_packet(ssh_pcap_file pcap, ssh_buffer packet, uint32_t original_len){
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ssh_buffer header=ssh_buffer_new();
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struct timeval now;
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int err;
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if(header == NULL)
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return SSH_ERROR;
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gettimeofday(&now,NULL);
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buffer_add_u32(header,htonl(now.tv_sec));
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buffer_add_u32(header,htonl(now.tv_usec));
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buffer_add_u32(header,htonl(ssh_buffer_get_len(packet)));
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buffer_add_u32(header,htonl(original_len));
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buffer_add_buffer(header,packet);
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err=ssh_pcap_file_write(pcap,header);
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ssh_buffer_free(header);
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return err;
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}
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/**
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* @brief opens a new pcap file and create header
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*/
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int ssh_pcap_file_open(ssh_pcap_file pcap, const char *filename){
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ssh_buffer header;
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int err;
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if(pcap == NULL)
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return SSH_ERROR;
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if(pcap->output){
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fclose(pcap->output);
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pcap->output=NULL;
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}
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pcap->output=fopen(filename,"wb");
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if(pcap->output==NULL)
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return SSH_ERROR;
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header=ssh_buffer_new();
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if(header==NULL)
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return SSH_ERROR;
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buffer_add_u32(header,htonl(PCAP_MAGIC));
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buffer_add_u16(header,htons(PCAP_VERSION_MAJOR));
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buffer_add_u16(header,htons(PCAP_VERSION_MINOR));
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/* currently hardcode GMT to 0 */
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buffer_add_u32(header,htonl(0));
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/* accuracy */
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buffer_add_u32(header,htonl(0));
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/* size of the biggest packet */
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buffer_add_u32(header,htonl(MAX_PACKET_LEN));
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/* we will write sort-of IP */
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buffer_add_u32(header,htonl(DLT_RAW));
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err=ssh_pcap_file_write(pcap,header);
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ssh_buffer_free(header);
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return err;
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}
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int ssh_pcap_file_close(ssh_pcap_file pcap){
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int err;
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if(pcap ==NULL || pcap->output==NULL)
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return SSH_ERROR;
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err=fclose(pcap->output);
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pcap->output=NULL;
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if(err != 0)
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return SSH_ERROR;
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else
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return SSH_OK;
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}
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void ssh_pcap_file_free(ssh_pcap_file pcap){
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ssh_pcap_file_close(pcap);
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SAFE_FREE(pcap);
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}
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/** @internal
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* @brief allocates a new ssh_pcap_context object
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*/
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ssh_pcap_context ssh_pcap_context_new(ssh_session session){
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ssh_pcap_context ctx=malloc(sizeof(struct ssh_pcap_context_struct));
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if(ctx==NULL){
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ssh_set_error_oom(session);
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return NULL;
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}
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ZERO_STRUCTP(ctx);
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ctx->session=session;
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return ctx;
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}
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void ssh_pcap_context_free(ssh_pcap_context ctx){
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SAFE_FREE(ctx);
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}
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void ssh_pcap_context_set_file(ssh_pcap_context ctx, ssh_pcap_file pcap){
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ctx->file=pcap;
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}
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/** @internal
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* @brief sets the IP and port parameters in the connection
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*/
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static int ssh_pcap_context_connect(ssh_pcap_context ctx){
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ssh_session session=ctx->session;
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struct sockaddr_in local, remote;
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socket_t fd;
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socklen_t len;
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if(session==NULL)
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return SSH_ERROR;
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if(session->socket==NULL)
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return SSH_ERROR;
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fd=ssh_socket_get_fd_in(session->socket);
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/* TODO: adapt for windows */
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if(fd<0)
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return SSH_ERROR;
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len=sizeof(local);
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if(getsockname(fd,(struct sockaddr *)&local,&len)<0){
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ssh_set_error(session,SSH_REQUEST_DENIED,"Getting local IP address: %s",strerror(errno));
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return SSH_ERROR;
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}
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len=sizeof(remote);
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if(getpeername(fd,(struct sockaddr *)&remote,&len)<0){
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ssh_set_error(session,SSH_REQUEST_DENIED,"Getting remote IP address: %s",strerror(errno));
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return SSH_ERROR;
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}
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if(local.sin_family != AF_INET){
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ssh_set_error(session,SSH_REQUEST_DENIED,"Only IPv4 supported for pcap logging");
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return SSH_ERROR;
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}
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memcpy(&ctx->ipsource,&local.sin_addr,sizeof(ctx->ipsource));
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memcpy(&ctx->ipdest,&remote.sin_addr,sizeof(ctx->ipdest));
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memcpy(&ctx->portsource,&local.sin_port,sizeof(ctx->portsource));
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memcpy(&ctx->portdest,&remote.sin_port,sizeof(ctx->portdest));
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ctx->connected=1;
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return SSH_OK;
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}
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#define IPHDR_LEN 20
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#define TCPHDR_LEN 20
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#define TCPIPHDR_LEN (IPHDR_LEN + TCPHDR_LEN)
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/** @internal
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* @brief write a SSH packet as a TCP over IP in a pcap file
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* @param ctx open pcap context
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* @param direction SSH_PCAP_DIRECTION_IN if the packet has been received
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* @param direction SSH_PCAP_DIRECTION_OUT if the packet has been emitted
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* @param data pointer to the data to write
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* @param len data to write in the pcap file. May be smaller than origlen.
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* @param origlen number of bytes of complete data.
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* @returns SSH_OK write is successful
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* @returns SSH_ERROR an error happened.
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*/
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int ssh_pcap_context_write(ssh_pcap_context ctx,enum ssh_pcap_direction direction
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, void *data, uint32_t len, uint32_t origlen){
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ssh_buffer ip;
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int err;
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if(ctx==NULL || ctx->file ==NULL)
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return SSH_ERROR;
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if(ctx->connected==0)
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if(ssh_pcap_context_connect(ctx)==SSH_ERROR)
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return SSH_ERROR;
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ip=ssh_buffer_new();
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if(ip==NULL){
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ssh_set_error_oom(ctx->session);
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return SSH_ERROR;
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}
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/* build an IP packet */
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/* V4, 20 bytes */
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buffer_add_u8(ip,4 << 4 | 5);
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/* tos */
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buffer_add_u8(ip,0);
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/* total len */
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buffer_add_u16(ip,htons(origlen + TCPIPHDR_LEN));
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/* IP id number */
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buffer_add_u16(ip,htons(ctx->file->ipsequence));
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ctx->file->ipsequence++;
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/* fragment offset */
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buffer_add_u16(ip,htons(0));
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/* TTL */
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buffer_add_u8(ip,64);
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/* protocol TCP=6 */
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buffer_add_u8(ip,6);
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/* checksum */
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buffer_add_u16(ip,0);
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if(direction==SSH_PCAP_DIR_OUT){
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buffer_add_u32(ip,ctx->ipsource);
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buffer_add_u32(ip,ctx->ipdest);
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} else {
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buffer_add_u32(ip,ctx->ipdest);
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buffer_add_u32(ip,ctx->ipsource);
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}
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/* TCP */
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if(direction==SSH_PCAP_DIR_OUT){
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buffer_add_u16(ip,ctx->portsource);
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buffer_add_u16(ip,ctx->portdest);
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} else {
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buffer_add_u16(ip,ctx->portdest);
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buffer_add_u16(ip,ctx->portsource);
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}
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/* sequence number */
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if(direction==SSH_PCAP_DIR_OUT){
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buffer_add_u32(ip,ntohl(ctx->outsequence));
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ctx->outsequence+=origlen;
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} else {
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buffer_add_u32(ip,ntohl(ctx->insequence));
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ctx->insequence+=origlen;
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}
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/* ack number */
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if(direction==SSH_PCAP_DIR_OUT){
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buffer_add_u32(ip,ntohl(ctx->insequence));
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} else {
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buffer_add_u32(ip,ntohl(ctx->outsequence));
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}
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/* header len = 20 = 5 * 32 bits, at offset 4*/
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buffer_add_u8(ip,5 << 4);
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/* flags */
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buffer_add_u8(ip,TH_PUSH | TH_ACK);
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/* window */
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buffer_add_u16(ip,htons(65535));
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/* checksum */
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buffer_add_u16(ip,htons(0));
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/* urgent data ptr */
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buffer_add_u16(ip,0);
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/* actual data */
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buffer_add_data(ip,data,len);
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err=ssh_pcap_file_write_packet(ctx->file,ip,origlen + TCPIPHDR_LEN);
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ssh_buffer_free(ip);
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return err;
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}
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/** @brief sets the pcap file used to trace the session
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* @param current session
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* @param pcap an handler to a pcap file. A pcap file may be used in several
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* sessions.
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* @returns SSH_ERROR in case of error, SSH_OK otherwise.
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*/
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int ssh_set_pcap_file(ssh_session session, ssh_pcap_file pcap){
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ssh_pcap_context ctx=ssh_pcap_context_new(session);
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if(ctx==NULL){
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ssh_set_error_oom(session);
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return SSH_ERROR;
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}
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ctx->file=pcap;
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if(session->pcap_ctx)
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ssh_pcap_context_free(session->pcap_ctx);
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session->pcap_ctx=ctx;
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return SSH_OK;
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}
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#else /* WITH_PCAP */
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/* Simple stub returning errors when no pcap compiled in */
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#include "libssh/libssh.h"
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#include "libssh/priv.h"
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int ssh_pcap_file_close(ssh_pcap_file pcap){
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(void) pcap;
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return SSH_ERROR;
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}
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void ssh_pcap_file_free(ssh_pcap_file pcap){
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(void) pcap;
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}
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ssh_pcap_file ssh_pcap_file_new(void){
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return NULL;
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}
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int ssh_pcap_file_open(ssh_pcap_file pcap, const char *filename){
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(void) pcap;
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(void) filename;
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return SSH_ERROR;
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}
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int ssh_set_pcap_file(ssh_session session, ssh_pcap_file pcapfile){
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(void) pcapfile;
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ssh_set_error(session,SSH_REQUEST_DENIED,"Pcap support not compiled in");
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return SSH_ERROR;
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}
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#endif
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/** @} */
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/* vim: set ts=4 sw=4 et cindent: */
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