src/pcap.c - master - niceSOFT/libssh

src/pcap.c
585 строк15 KB
Jakub Jelen
Use calloc instead of zeroizing structure after malloc
06 авг 2025, 12:16
06 авг 2025, 12:16d1bf906
/*
 * 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 */
#include "config.h"
#ifdef WITH_PCAP

#include <stdio.h>
#ifdef _WIN32
#include <winsock2.h>
#include <ws2tcpip.h>
#else
#include <netinet/in.h>
#include <sys/socket.h>
#endif
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif /* HAVE_SYS_TIME_H */
#include <errno.h>
#include <stdlib.h>

#include "libssh/libssh.h"
#include "libssh/pcap.h"
#include "libssh/session.h"
#include "libssh/buffer.h"
#include "libssh/socket.h"

/**
 * @defgroup libssh_pcap The libssh pcap functions
 * @ingroup libssh
 *
 * The pcap file generation
 *
 * @{
 */

/* 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 {
	uint32_t magic_number;   /* magic number */
	uint16_t version_major;  /* major version number */
	uint16_t version_minor;  /* minor version number */
	int32_t  thiszone;       /* GMT to local correction */
	uint32_t sigfigs;        /* accuracy of timestamps */
	uint32_t snaplen;        /* max length of captured packets, in octets */
	uint32_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 {
	uint32_t ts_sec;         /* timestamp seconds */
	uint32_t ts_usec;        /* timestamp microseconds */
	uint32_t incl_len;       /* number of octets of packet saved in file */
	uint32_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;
	int connected;
	/* All of this information is useful to generate
	 * the dummy IP and TCP packets
	 */
	uint32_t ipsource;
	uint32_t ipdest;
	uint16_t portsource;
	uint16_t portdest;
	uint32_t outsequence;
	uint32_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;
	uint16_t ipsequence;
};

/**
 * @brief create a new ssh_pcap_file object
 */
ssh_pcap_file ssh_pcap_file_new(void)
{
    struct ssh_pcap_file_struct *pcap = NULL;

    pcap = calloc(1, sizeof(struct ssh_pcap_file_struct));
    if (pcap == NULL) {
        return NULL;
    }

    return pcap;
}

/** @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 = ssh_buffer_get_len(packet);
    err = fwrite(ssh_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, uint32_t original_len)
{
    ssh_buffer header = ssh_buffer_new();
    struct timeval now;
    int err;

    if (header == NULL) {
        return SSH_ERROR;
    }

    gettimeofday(&now, NULL);
    err = ssh_buffer_allocate_size(header,
                                   sizeof(uint32_t) * 4 +
                                   ssh_buffer_get_len(packet));
    if (err < 0) {
        goto error;
    }
    err = ssh_buffer_add_u32(header, htonl(now.tv_sec));
    if (err < 0) {
        goto error;
    }
    err = ssh_buffer_add_u32(header, htonl(now.tv_usec));
    if (err < 0) {
        goto error;
    }
    err = ssh_buffer_add_u32(header, htonl(ssh_buffer_get_len(packet)));
    if (err < 0) {
        goto error;
    }
    err = ssh_buffer_add_u32(header, htonl(original_len));
    if (err < 0) {
        goto error;
    }
    err = ssh_buffer_add_buffer(header, packet);
    if (err < 0) {
        goto error;
    }
    err = ssh_pcap_file_write(pcap, header);
error:
    SSH_BUFFER_FREE(header);
    return err;
}

/**
 * @brief opens a new pcap file and creates header
 */
int ssh_pcap_file_open(ssh_pcap_file pcap, const char *filename)
{
    ssh_buffer header = NULL;
    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 = ssh_buffer_new();
    if (header == NULL) {
        return SSH_ERROR;
    }
    err = ssh_buffer_allocate_size(header,
                                   sizeof(uint32_t) * 5 +
                                   sizeof(uint16_t) * 2);
    if (err < 0) {
        goto error;
    }
    err = ssh_buffer_add_u32(header, htonl(PCAP_MAGIC));
    if (err < 0) {
        goto error;
    }
    err = ssh_buffer_add_u16(header, htons(PCAP_VERSION_MAJOR));
    if (err < 0) {
        goto error;
    }
    err = ssh_buffer_add_u16(header, htons(PCAP_VERSION_MINOR));
    if (err < 0) {
        goto error;
    }
    /* currently hardcode GMT to 0 */
    err = ssh_buffer_add_u32(header, htonl(0));
    if (err < 0) {
        goto error;
    }
    /* accuracy */
    err = ssh_buffer_add_u32(header, htonl(0));
    if (err < 0) {
        goto error;
    }
    /* size of the biggest packet */
    err = ssh_buffer_add_u32(header, htonl(MAX_PACKET_LEN));
    if (err < 0) {
        goto error;
    }
    /* we will write sort-of IP */
    err = ssh_buffer_add_u32(header, htonl(DLT_RAW));
    if (err < 0) {
        goto error;
    }
    err = ssh_pcap_file_write(pcap,header);
error:
    SSH_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_file_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 = NULL;

    ctx = calloc(1, sizeof(struct ssh_pcap_context_struct));
    if (ctx == NULL) {
        ssh_set_error_oom(session);
        return NULL;
    }
    ctx->session = session;
    return ctx;
}

void ssh_pcap_context_free(ssh_pcap_context ctx)
{
    SAFE_FREE(ctx);
}

void ssh_pcap_context_set_file(ssh_pcap_context ctx, ssh_pcap_file pcap)
{
    ctx->file = pcap;
}

/** @internal
 * @brief sets the IP and port parameters in the connection
 */
static int ssh_pcap_context_connect(ssh_pcap_context ctx)
{
    ssh_session session=ctx->session;
    struct sockaddr_in local = {
        .sin_family = AF_UNSPEC,
    };
    struct sockaddr_in remote = {
        .sin_family = AF_UNSPEC,
    };
    socket_t fd;
    socklen_t len;
    int rc;
    char err_msg[SSH_ERRNO_MSG_MAX] = {0};

    if (session == NULL) {
        return SSH_ERROR;
    }

    if (session->socket == NULL) {
        return SSH_ERROR;
    }

    fd = ssh_socket_get_fd(session->socket);

    /* TODO: adapt for windows */
    if (fd < 0) {
        return SSH_ERROR;
    }

    len = sizeof(local);
    rc = getsockname(fd, (struct sockaddr *)&local, &len);
    if (rc < 0) {
        ssh_set_error(session,
                      SSH_REQUEST_DENIED,
                      "Getting local IP address: %s",
                      ssh_strerror(errno, err_msg, SSH_ERRNO_MSG_MAX));
        return SSH_ERROR;
    }

    len = sizeof(remote);
    rc = getpeername(fd, (struct sockaddr *)&remote, &len);
    if (rc < 0) {
        ssh_set_error(session,
                      SSH_REQUEST_DENIED,
                      "Getting remote IP address: %s",
                      ssh_strerror(errno, err_msg, SSH_ERRNO_MSG_MAX));
        return SSH_ERROR;
    }

    if (local.sin_family != AF_INET) {
        ssh_set_error(session,
                      SSH_REQUEST_DENIED,
                      "Only IPv4 supported for pcap logging");
        return SSH_ERROR;
    }

    memcpy(&ctx->ipsource, &local.sin_addr, sizeof(ctx->ipsource));
    memcpy(&ctx->ipdest, &remote.sin_addr, sizeof(ctx->ipdest));
    memcpy(&ctx->portsource, &local.sin_port, sizeof(ctx->portsource));
    memcpy(&ctx->portdest, &remote.sin_port, sizeof(ctx->portdest));

    ctx->connected = 1;
    return SSH_OK;
}

#define IPHDR_LEN 20
#define TCPHDR_LEN 20
#define TCPIPHDR_LEN (IPHDR_LEN + TCPHDR_LEN)
/** @internal
 * @brief write a SSH packet as a TCP over IP in a pcap file
 * @param ctx open pcap context
 * @param direction SSH_PCAP_DIRECTION_IN if the packet has been received
 * @param direction SSH_PCAP_DIRECTION_OUT if the packet has been emitted
 * @param data pointer to the data to write
 * @param len data to write in the pcap file. May be smaller than origlen.
 * @param origlen number of bytes of complete data.
 * @returns SSH_OK write is successful
 * @returns SSH_ERROR an error happened.
 */
int ssh_pcap_context_write(ssh_pcap_context ctx,
                           enum ssh_pcap_direction direction,
                           void *data,
                           uint32_t len,
                           uint32_t origlen)
{
    ssh_buffer ip;
    int rc;

    if (ctx == NULL || ctx->file == NULL) {
        return SSH_ERROR;
    }
    if (ctx->connected == 0) {
        if (ssh_pcap_context_connect(ctx) == SSH_ERROR) {
            return SSH_ERROR;
        }
    }
    ip = ssh_buffer_new();
    if (ip == NULL) {
        ssh_set_error_oom(ctx->session);
        return SSH_ERROR;
    }

    /* build an IP packet */
    rc = ssh_buffer_pack(ip,
                         "bbwwwbbw",
                         4 << 4 | 5, /* V4, 20 bytes */
                         0,          /* tos */
                         origlen + TCPIPHDR_LEN, /* total len */
                         ctx->file->ipsequence,  /* IP id number */
                         0,          /* fragment offset */
                         64,         /* TTL */
                         6,          /* protocol TCP=6 */
                         0);         /* checksum */

    ctx->file->ipsequence++;
    if (rc != SSH_OK) {
        goto error;
    }
    if (direction == SSH_PCAP_DIR_OUT) {
        rc = ssh_buffer_add_u32(ip, ctx->ipsource);
        if (rc < 0) {
            goto error;
        }
        rc = ssh_buffer_add_u32(ip, ctx->ipdest);
        if (rc < 0) {
            goto error;
        }
    } else {
        rc = ssh_buffer_add_u32(ip, ctx->ipdest);
        if (rc < 0) {
            goto error;
        }
        rc = ssh_buffer_add_u32(ip, ctx->ipsource);
        if (rc < 0) {
            goto error;
        }
    }
    /* TCP */
    if (direction == SSH_PCAP_DIR_OUT) {
        rc = ssh_buffer_add_u16(ip, ctx->portsource);
        if (rc < 0) {
            goto error;
        }
        rc = ssh_buffer_add_u16(ip, ctx->portdest);
        if (rc < 0) {
            goto error;
        }
    } else {
        rc = ssh_buffer_add_u16(ip, ctx->portdest);
        if (rc < 0) {
            goto error;
        }
        rc = ssh_buffer_add_u16(ip, ctx->portsource);
        if (rc < 0) {
            goto error;
        }
    }
    /* sequence number */
    if (direction == SSH_PCAP_DIR_OUT) {
        rc = ssh_buffer_pack(ip, "d", ctx->outsequence);
        if (rc != SSH_OK) {
            goto error;
        }
        ctx->outsequence += origlen;
    } else {
        rc = ssh_buffer_pack(ip, "d", ctx->insequence);
        if (rc != SSH_OK) {
            goto error;
        }
        ctx->insequence += origlen;
    }
    /* ack number */
    if (direction == SSH_PCAP_DIR_OUT) {
        rc = ssh_buffer_pack(ip, "d", ctx->insequence);
        if (rc != SSH_OK) {
            goto error;
        }
    } else {
        rc = ssh_buffer_pack(ip, "d", ctx->outsequence);
        if (rc != SSH_OK) {
            goto error;
        }
    }

    rc = ssh_buffer_pack(ip,
                         "bbwwwP",
                         5 << 4,             /* header len = 20 = 5 * 32 bits, at offset 4*/
                         TH_PUSH | TH_ACK,   /* flags */
                         65535,              /* window */
                         0,                  /* checksum */
                         0,                  /* urgent data ptr */
                         (size_t)len, data); /* actual data */
    if (rc != SSH_OK) {
        goto error;
    }
    rc = ssh_pcap_file_write_packet(ctx->file, ip, origlen + TCPIPHDR_LEN);

error:
    SSH_BUFFER_FREE(ip);
    return rc;
}

/** @brief sets the pcap file used to trace the session
 * @param current session
 * @param pcap a handler to a pcap file. A pcap file may be used in several
 * sessions.
 * @returns SSH_ERROR in case of error, SSH_OK otherwise.
 */
int ssh_set_pcap_file(ssh_session session, ssh_pcap_file pcap)
{
    ssh_pcap_context ctx = ssh_pcap_context_new(session);
    if (ctx == NULL) {
        ssh_set_error_oom(session);
        return SSH_ERROR;
    }
    ctx->file = pcap;
    if (session->pcap_ctx) {
        ssh_pcap_context_free(session->pcap_ctx);
    }
    session->pcap_ctx = ctx;
    return SSH_OK;
}
/** @} */

#else /* WITH_PCAP */

/* Simple stub returning errors when no pcap compiled in */

#include "libssh/libssh.h"
#include "libssh/priv.h"

int ssh_pcap_file_close(ssh_pcap_file pcap)
{
    (void)pcap;

    return SSH_ERROR;
}

void ssh_pcap_file_free(ssh_pcap_file pcap)
{
    (void)pcap;
}

ssh_pcap_file ssh_pcap_file_new(void)
{
    return NULL;
}
int ssh_pcap_file_open(ssh_pcap_file pcap, const char *filename)
{
    (void)pcap;
    (void)filename;

    return SSH_ERROR;
}

int ssh_set_pcap_file(ssh_session session, ssh_pcap_file pcapfile)
{
    (void)pcapfile;

    ssh_set_error(session, SSH_REQUEST_DENIED, "Pcap support not compiled in");
    return SSH_ERROR;
}

#endif