diff options
Diffstat (limited to 'libssh/pcap.c')
-rw-r--r-- | libssh/pcap.c | 291 |
1 files changed, 291 insertions, 0 deletions
diff --git a/libssh/pcap.c b/libssh/pcap.c new file mode 100644 index 00000000..3c45c1e7 --- /dev/null +++ b/libssh/pcap.c @@ -0,0 +1,291 @@ +/* + * This file is part of the SSH Library + * + * Copyright (c) 2009 by Aris Adamantiadis + * + * The SSH Library is free software; you can redistribute it and/or modify + * it under the terms of the GNU Lesser General Public License as published by + * the Free Software Foundation; either version 2.1 of the License, or (at your + * option) any later version. + * + * The SSH Library 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 Lesser General Public + * License for more details. + * + * You should have received a copy of the GNU Lesser General Public License + * along with the SSH Library; see the file COPYING. If not, write to + * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, + * MA 02111-1307, USA. + */ + +/* pcap.c */ +/** \defgroup ssh_pcap SSH-pcap + * \brief libssh pcap file generation + * + * \addtogroup ssh_pcap + * @{ */ + +#include <stdio.h> +#include <sys/time.h> + +#include "config.h" +#include "libssh/libssh.h" +#include "libssh/pcap.h" +#include "libssh/session.h" +#include "libssh/buffer.h" + +#ifdef WITH_PCAP +/* The header of a pcap file is the following. We are not going to make it + * very complicated. + * Just for information. + */ +struct pcap_hdr_s { + u_int32_t magic_number; /* magic number */ + u_int16_t version_major; /* major version number */ + u_int16_t version_minor; /* minor version number */ + int32_t thiszone; /* GMT to local correction */ + u_int32_t sigfigs; /* accuracy of timestamps */ + u_int32_t snaplen; /* max length of captured packets, in octets */ + u_int32_t network; /* data link type */ +}; + +#define PCAP_MAGIC 0xa1b2c3d4 +#define PCAP_VERSION_MAJOR 2 +#define PCAP_VERSION_MINOR 4 + +#define DLT_RAW 12 /* raw IP */ + +/* 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 + +/* The header of a pcap packet. + * Just for information. + */ +struct pcaprec_hdr_s { + u_int32_t ts_sec; /* timestamp seconds */ + u_int32_t ts_usec; /* timestamp microseconds */ + u_int32_t incl_len; /* number of octets of packet saved in file */ + u_int32_t orig_len; /* actual length of packet */ +}; + +/** @private + * @brief a pcap context expresses the state of a pcap dump + * in a SSH session only. Multiple pcap contexts may be used into + * a single pcap file. + */ + +struct ssh_pcap_context_struct { + ssh_session session; + ssh_pcap_file file; + /* All of these informations are useful to generate + * the dummy IP and TCP packets + */ + u_int32_t ipsource; + u_int32_t ipdest; + u_int16_t portsource; + u_int16_t portdest; + u_int32_t outsequence; + u_int32_t insequence; +}; + +/** @private + * @brief a pcap file expresses the state of a pcap file which may + * contain several streams. + */ +struct ssh_pcap_file_struct { + FILE *output; +}; + +/** + * @brief create a new ssh_pcap_file object + */ +ssh_pcap_file ssh_pcap_file_new(){ + return malloc(sizeof(struct ssh_pcap_file_struct)); +} + +/** @internal + * @brief writes a packet on file + */ +static int ssh_pcap_file_write(ssh_pcap_file pcap, ssh_buffer packet){ + int err; + uint32_t len; + if(pcap == NULL || pcap->output==NULL) + return SSH_ERROR; + len=buffer_get_len(packet); + err=fwrite(buffer_get(packet),len,1,pcap->output); + if(err<0) + return SSH_ERROR; + else + return SSH_OK; +} + +/** @internal + * @brief prepends a packet with the pcap header and writes packet + * on file + */ +int ssh_pcap_file_write_packet(ssh_pcap_file pcap, ssh_buffer packet, u_int32_t original_len){ + ssh_buffer header=buffer_new(); + struct timeval now; + int err; + if(header == NULL) + return SSH_ERROR; + gettimeofday(&now,NULL); + buffer_add_u32(header,htonl(now.tv_sec)); + buffer_add_u32(header,htonl(now.tv_usec)); + buffer_add_u32(header,htonl(buffer_get_len(packet))); + buffer_add_u32(header,htonl(original_len)); + buffer_add_buffer(header,packet); + err=ssh_pcap_file_write(pcap,header); + buffer_free(header); + return err; +} + +/** + * @brief opens a new pcap file and create header + */ +int ssh_pcap_file_open(ssh_pcap_file pcap, const char *filename){ + ssh_buffer header; + int err; + if(pcap == NULL) + return SSH_ERROR; + if(pcap->output){ + fclose(pcap->output); + pcap->output=NULL; + } + pcap->output=fopen(filename,"wb"); + if(pcap->output==NULL) + return SSH_ERROR; + header=buffer_new(); + if(header==NULL) + return SSH_ERROR; + buffer_add_u32(header,htonl(PCAP_MAGIC)); + buffer_add_u16(header,htons(PCAP_VERSION_MAJOR)); + buffer_add_u16(header,htons(PCAP_VERSION_MINOR)); + /* currently hardcode GMT to 0 */ + buffer_add_u32(header,htonl(0)); + /* accuracy */ + buffer_add_u32(header,htonl(0)); + /* size of the biggest packet */ + buffer_add_u32(header,htonl(MAX_PACKET_LEN)); + /* we will write sort-of IP */ + buffer_add_u32(header,htonl(DLT_RAW)); + err=ssh_pcap_file_write(pcap,header); + buffer_free(header); + return err; +} + +int ssh_pcap_file_close(ssh_pcap_file pcap){ + int err; + if(pcap ==NULL || pcap->output==NULL) + return SSH_ERROR; + err=fclose(pcap->output); + pcap->output=NULL; + if(err != 0) + return SSH_ERROR; + else + return SSH_OK; +} + +void ssh_pcap_free(ssh_pcap_file pcap){ + ssh_pcap_file_close(pcap); + SAFE_FREE(pcap); +} + + +/** @internal + * @brief allocates a new ssh_pcap_context object + */ + +ssh_pcap_context ssh_pcap_context_new(ssh_session session){ + ssh_pcap_context ctx=malloc(sizeof(struct ssh_pcap_context_struct)); + if(ctx==NULL){ + ssh_set_error_oom(session); + return NULL; + } + ZERO_STRUCTP(ctx); + ctx->session=session; + return ctx; +} + +void ssh_pcap_context_set_file(ssh_pcap_context ctx, ssh_pcap_file pcap){ + ctx->file=pcap; +} + +int ssh_pcap_context_write(ssh_pcap_context ctx,enum ssh_pcap_direction direction + , void *data, u_int32_t len, u_int32_t origlen){ + ssh_buffer ip=buffer_new(); + int err; + if(ip==NULL){ + ssh_set_error_oom(ctx->session); + return SSH_ERROR; + } + /* build an IP packet */ + /* V4, 20 bytes */ + buffer_add_u8(ip,4 << 4 | 5); + /* tos */ + buffer_add_u8(ip,0); + /* total len */ + buffer_add_u16(ip,htons(origlen + 40)); + /* id */ + buffer_add_u16(ip,htons(1)); + /* fragment offset */ + buffer_add_u16(ip,htons(0)); + /* TTL */ + buffer_add_u8(ip,64); + /* protocol TCP=6 */ + buffer_add_u8(ip,6); + /* checksum */ + buffer_add_u16(ip,0); + if(direction==SSH_PCAP_DIR_OUT){ + buffer_add_u32(ip,ctx->ipsource); + buffer_add_u32(ip,ctx->ipdest); + } else { + buffer_add_u32(ip,ctx->ipdest); + buffer_add_u32(ip,ctx->ipsource); + } + /* TCP */ + if(direction==SSH_PCAP_DIR_OUT){ + buffer_add_u16(ip,ntohs(ctx->portsource)); + buffer_add_u16(ip,ntohs(ctx->portdest)); + } else { + buffer_add_u16(ip,ntohs(ctx->portdest)); + buffer_add_u16(ip,ntohs(ctx->portsource)); + } + /* sequence number */ + if(direction==SSH_PCAP_DIR_OUT){ + buffer_add_u32(ip,ntohl(ctx->outsequence)); + } else { + buffer_add_u32(ip,ntohl(ctx->insequence)); + } + /* ack number */ + if(direction==SSH_PCAP_DIR_OUT){ + buffer_add_u32(ip,ntohl(ctx->insequence)); + } else { + buffer_add_u32(ip,ntohl(ctx->outsequence)); + } + /* header len */ + buffer_add_u8(ip,5 << 4); + /* flags */ + buffer_add_u8(ip,TH_PUSH | TH_ACK); + /* window */ + buffer_add_u16(ip,htons(65535)); + /* checksum */ + buffer_add_u16(ip,htons(0)); + /* urgent data ptr */ + buffer_add_u16(ip,0); + /* actual data */ + buffer_add_data(ip,data,len); + err=ssh_pcap_file_write_packet(ctx->file,ip,origlen + 40); + buffer_free(ip); + return err; +} + +#endif /* WITH_PCAP */ +/** @} */ +/* vim: set ts=2 sw=2 et cindent: */ |