libssh/libssh/packet.c

/*
 * packet.c - packet building functions
 *
 * This file is part of the SSH Library
 *
 * Copyright (c) 2003-2008 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.
 *
 * vim: ts=2 sw=2 et cindent
 */

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>

#include "config.h"
#include "libssh/priv.h"
#include "libssh/ssh2.h"
#include "libssh/ssh1.h"
#include "libssh/crypto.h"

/* XXX include selected mac size */
static int macsize=SHA_DIGEST_LEN;

/* in nonblocking mode, socket_read will read as much as it can, and return */
/* SSH_OK if it has read at least len bytes, otherwise, SSH_AGAIN. */
/* in blocking mode, it will read at least len bytes and will block until it's ok. */


#define PACKET_STATE_INIT 0
#define PACKET_STATE_SIZEREAD 1

static int packet_read2(SSH_SESSION *session) {
  unsigned int blocksize = (session->current_crypto ?
      session->current_crypto->in_cipher->blocksize : 8);
  int current_macsize = session->current_crypto ? macsize : 0;
  unsigned char mac[30] = {0};
  char buffer[16] = {0};
  void *packet=NULL;
  int to_be_read;
  int rc = SSH_ERROR;

  u32 len;
  u8 padding;

  enter_function();

  if (session->alive == 0) {
    /* The error message was already set into this session */
    leave_function();
    return SSH_ERROR;
  }

  switch(session->packet_state) {
    case PACKET_STATE_INIT:
      memset(&session->in_packet, 0, sizeof(PACKET));

      if (session->in_buffer) {
        if (buffer_reinit(session->in_buffer) < 0) {
          goto error;
        }
      } else {
        session->in_buffer = buffer_new();
        if (session->in_buffer == NULL) {
          goto error;
        }
      }

      rc = ssh_socket_wait_for_data(session->socket, session, blocksize);
      if (rc != SSH_OK) {
        goto error;
      }
      rc = SSH_ERROR;
      /* can't fail since we're sure there is enough data in socket buffer */
      ssh_socket_read(session->socket, buffer, blocksize);
      len = packet_decrypt_len(session, buffer);

      if (buffer_add_data(session->in_buffer, buffer, blocksize) < 0) {
        goto error;
      }

      if(len > MAX_PACKET_LEN) {
        ssh_set_error(session, SSH_FATAL,
            "read_packet(): Packet len too high(%u %.4x)", len, len);
        goto error;
      }

      to_be_read = len - blocksize + sizeof(u32);
      if (to_be_read < 0) {
        /* remote sshd sends invalid sizes? */
        ssh_set_error(session, SSH_FATAL,
            "given numbers of bytes left to be read < 0 (%d)!", to_be_read);
        goto error;
      }

      /* saves the status of the current operations */
      session->in_packet.len = len;
      session->packet_state = PACKET_STATE_SIZEREAD;
    case PACKET_STATE_SIZEREAD:
      len = session->in_packet.len;
      to_be_read = len - blocksize + sizeof(u32) + current_macsize;
      /* if to_be_read is zero, the whole packet was blocksize bytes. */
      if (to_be_read != 0) {
        rc = ssh_socket_wait_for_data(session->socket,session,to_be_read);
        if (rc != SSH_OK) {
          goto error;
        }
        rc = SSH_ERROR;

        packet = malloc(to_be_read);
        if (packet == NULL) {
          ssh_set_error(session, SSH_FATAL, "No space left");
          goto error;
        }
        ssh_socket_read(session->socket,packet,to_be_read-current_macsize);

        ssh_log(session,SSH_LOG_PACKET,"Read a %d bytes packet",len);

        if (buffer_add_data(session->in_buffer, packet,
              to_be_read - current_macsize) < 0) {
          SAFE_FREE(packet);
          goto error;
        }
        SAFE_FREE(packet);
      }

      if (session->current_crypto) {
        /*
         * decrypt the rest of the packet (blocksize bytes already
         * have been decrypted)
         */
        if (packet_decrypt(session,
              buffer_get(session->in_buffer) + blocksize,
              buffer_get_len(session->in_buffer) - blocksize) < 0) {
          ssh_set_error(session, SSH_FATAL, "Decrypt error");
          goto error;
        }
        ssh_socket_read(session->socket, mac, macsize);

        if (packet_hmac_verify(session, session->in_buffer, mac)) {
          ssh_set_error(session, SSH_FATAL, "HMAC error");
          goto error;
        }
      }

      buffer_pass_bytes(session->in_buffer, sizeof(u32));

      /* pass the size which has been processed before */
      if (buffer_get_u8(session->in_buffer, &padding) == 0) {
        ssh_set_error(session, SSH_FATAL, "Packet too short to read padding");
        goto error;
      }

      ssh_log(session, SSH_LOG_RARE,
          "%hhd bytes padding, %d bytes left in buffer",
          padding, buffer_get_rest_len(session->in_buffer));

      if (padding > buffer_get_rest_len(session->in_buffer)) {
        ssh_set_error(session, SSH_FATAL,
            "Invalid padding: %d (%d resting)",
            padding,
            buffer_get_rest_len(session->in_buffer));
#ifdef DEBUG_CRYPTO
        ssh_print_hexa("incrimined packet",
            buffer_get(session->in_buffer),
            buffer_get_len(session->in_buffer));
#endif
        goto error;
      }
      buffer_pass_bytes_end(session->in_buffer, padding);

      ssh_log(session, SSH_LOG_RARE,
          "After padding, %d bytes left in buffer",
          buffer_get_rest_len(session->in_buffer));
#if defined(HAVE_LIBZ) && defined(WITH_LIBZ)
      if (session->current_crypto && session->current_crypto->do_compress_in) {
        ssh_log(session, SSH_LOG_RARE, "Decompressing in_buffer ...");
        if (decompress_buffer(session, session->in_buffer) < 0) {
          goto error;
        }
      }
#endif
      session->recv_seq++;
      session->packet_state = PACKET_STATE_INIT;

      leave_function();
      return SSH_OK;
  }

  ssh_set_error(session, SSH_FATAL,
      "Invalid state into packet_read2(): %d",
      session->packet_state);

error:
  leave_function();
  return rc;
}

#ifdef HAVE_SSH1
/* a slighty modified packet_read2() for SSH-1 protocol */
static int packet_read1(SSH_SESSION *session) {
  void *packet = NULL;
  int rc = SSH_ERROR;
  int to_be_read;
  u32 padding;
  u32 crc;
  u32 len;

  enter_function();

  if(!session->alive) {
    goto error;
  }

  switch (session->packet_state){
    case PACKET_STATE_INIT:
      memset(&session->in_packet, 0, sizeof(PACKET));

      if (session->in_buffer) {
        if (buffer_reinit(session->in_buffer) < 0) {
          goto error;
        }
      } else {
        session->in_buffer = buffer_new();
        if (session->in_buffer == NULL) {
          goto error;
        }
      }

      rc = ssh_socket_read(session->socket, &len, sizeof(u32));
      if (rc != SSH_OK) {
        goto error;
      }

      rc = SSH_ERROR;

      /* len is not encrypted */
      len = ntohl(len);
      if (len > MAX_PACKET_LEN) {
        ssh_set_error(session, SSH_FATAL,
            "read_packet(): Packet len too high (%u %.8x)", len, len);
        goto error;
      }

      ssh_log(session, SSH_LOG_PACKET, "Reading a %d bytes packet", len);

      session->in_packet.len = len;
      session->packet_state = PACKET_STATE_SIZEREAD;
    case PACKET_STATE_SIZEREAD:
      len = session->in_packet.len;
      /* SSH-1 has a fixed padding lenght */
      padding = 8 - (len % 8);
      to_be_read = len + padding;

      /* it is _not_ possible that to_be_read be < 8. */
      packet = malloc(to_be_read);
      if (packet == NULL) {
        ssh_set_error(session, SSH_FATAL, "Not enough space");
        goto error;
      }

      rc = ssh_socket_read(session->socket, packet, to_be_read);
      if(rc != SSH_OK) {
        SAFE_FREE(packet);
        goto error;
      }
      rc = SSH_ERROR;

      if (buffer_add_data(session->in_buffer,packet,to_be_read) < 0) {
        SAFE_FREE(packet);
        goto error;
      }
      SAFE_FREE(packet);

#ifdef DEBUG_CRYPTO
      ssh_print_hexa("read packet:", buffer_get(session->in_buffer),
          buffer_get_len(session->in_buffer));
#endif
      if (session->current_crypto) {
        /*
         * We decrypt everything, missing the lenght part (which was
         * previously read, unencrypted, and is not part of the buffer
         */
        if (packet_decrypt(session,
              buffer_get(session->in_buffer),
              buffer_get_len(session->in_buffer)) < 0) {
          ssh_set_error(session, SSH_FATAL, "Packet decrypt error");
          goto error;
        }
      }
#ifdef DEBUG_CRYPTO
      ssh_print_hexa("read packet decrypted:", buffer_get(session->in_buffer),
          buffer_get_len(session->in_buffer));
#endif
      ssh_log(session, SSH_LOG_PACKET, "%d bytes padding", padding);
      if(((len + padding) != buffer_get_rest_len(session->in_buffer)) ||
          ((len + padding) < sizeof(u32))) {
        ssh_log(session, SSH_LOG_RARE, "no crc32 in packet");
        ssh_set_error(session, SSH_FATAL, "no crc32 in packet");
        goto error;
      }

      memcpy(&crc,
          buffer_get_rest(session->in_buffer) + (len+padding) - sizeof(u32),
          sizeof(u32));
      buffer_pass_bytes_end(session->in_buffer, sizeof(u32));
      crc = ntohl(crc);
      if (ssh_crc32(buffer_get_rest(session->in_buffer),
            (len + padding) - sizeof(u32)) != crc) {
#ifdef DEBUG_CRYPTO
        ssh_print_hexa("crc32 on",buffer_get_rest(session->in_buffer),
            len + padding - sizeof(u32));
#endif
        ssh_log(session, SSH_LOG_RARE, "Invalid crc32");
        ssh_set_error(session, SSH_FATAL,
            "Invalid crc32: expected %.8x, got %.8x",
            crc,
            ssh_crc32(buffer_get_rest(session->in_buffer),
              len + padding - sizeof(u32)));
        goto error;
      }
      /* pass the padding */
      buffer_pass_bytes(session->in_buffer, padding);
      ssh_log(session, SSH_LOG_PACKET, "The packet is valid");

/* TODO FIXME
#if defined(HAVE_LIBZ) && defined(WITH_LIBZ)
    if(session->current_crypto && session->current_crypto->do_compress_in){
        decompress_buffer(session,session->in_buffer);
    }
#endif
*/
      session->recv_seq++;
      session->packet_state=PACKET_STATE_INIT;

      leave_function();
      return SSH_OK;
  } /* switch */

  ssh_set_error(session, SSH_FATAL,
      "Invalid state into packet_read1(): %d",
      session->packet_state);
error:
  leave_function();
  return rc;
}

#endif /* HAVE_SSH1 */

/* that's where i'd like C to be object ... */
int packet_read(SSH_SESSION *session) {
#ifdef HAVE_SSH1
  if (session->version == 1) {
    return packet_read1(session);
  }
#endif
  return packet_read2(session);
}

int packet_translate(SSH_SESSION *session) {
  enter_function();

  memset(&session->in_packet, 0, sizeof(PACKET));
  if(session->in_buffer == NULL) {
    leave_function();
    return SSH_ERROR;
  }

  ssh_log(session, SSH_LOG_RARE, "Final size %d",
      buffer_get_rest_len(session->in_buffer));

  if(buffer_get_u8(session->in_buffer, &session->in_packet.type) == 0) {
    ssh_set_error(session, SSH_FATAL, "Packet too short to read type");
    leave_function();
    return SSH_ERROR;
  }

  ssh_log(session, SSH_LOG_RARE, "Type %hhd", session->in_packet.type);
  session->in_packet.valid = 1;

  leave_function();
  return SSH_OK;
}

/*
 * Write the the bufferized output. If the session is blocking, or
 * enforce_blocking is set, the call may block. Otherwise, it won't block.
 * Return SSH_OK if everything has been sent, SSH_AGAIN if there are still
 * things to send on buffer, SSH_ERROR if there is an error.
 */
int packet_flush(SSH_SESSION *session, int enforce_blocking) {
  if (enforce_blocking || session->blocking) {
    return ssh_socket_blocking_flush(session->socket);
  }

  return ssh_socket_nonblocking_flush(session->socket);
}

/*
 * This function places the outgoing packet buffer into an outgoing
 * socket buffer
 */
static int packet_write(SSH_SESSION *session) {
  int rc = SSH_ERROR;

  enter_function();

  ssh_socket_write(session->socket,
      buffer_get(session->out_buffer),
      buffer_get_len(session->out_buffer));

  rc = packet_flush(session, 0);

  leave_function();
  return rc;
}

static int packet_send2(SSH_SESSION *session) {
  unsigned int blocksize = (session->current_crypto ?
      session->current_crypto->out_cipher->blocksize : 8);
  u32 currentlen = buffer_get_len(session->out_buffer);
  unsigned char *hmac = NULL;
  char padstring[32] = {0};
  int rc = SSH_ERROR;
  u32 finallen;
  u8 padding;

  enter_function();

  ssh_log(session, SSH_LOG_RARE,
      "Writing on the wire a packet having %u bytes before", currentlen);

#if defined(HAVE_LIBZ) && defined(WITH_LIBZ)
  if (session->current_crypto && session->current_crypto->do_compress_out) {
    ssh_log(session, SSH_LOG_RARE, "Compressing in_buffer ...");
    if (compress_buffer(session,session->out_buffer) < 0) {
      goto error;
    }
    currentlen = buffer_get_len(session->out_buffer);
  }
#endif
  padding = (blocksize - ((currentlen +5) % blocksize));
  if(padding < 4) {
    padding += blocksize;
  }

  if (session->current_crypto) {
    ssh_get_random(padstring, padding, 0);
  } else {
    memset(padstring,0,padding);
  }

  finallen = htonl(currentlen + padding + 1);
  ssh_log(session, SSH_LOG_RARE,
      "%d bytes after comp + %d padding bytes = %d bytes packet",
      currentlen, padding, (ntohl(finallen)));

  if (buffer_add_data_begin(session->out_buffer, &padding, sizeof(u8)) < 0) {
    goto error;
  }
  if (buffer_add_data_begin(session->out_buffer, &finallen, sizeof(u32)) < 0) {
    goto error;
  }
  if (buffer_add_data(session->out_buffer, padstring, padding) < 0) {
    goto error;
  }

  hmac = packet_encrypt(session, buffer_get(session->out_buffer),
      buffer_get_len(session->out_buffer));
  if (hmac) {
    if (buffer_add_data(session->out_buffer, hmac, 20) < 0) {
      goto error;
    }
  }

  rc = packet_write(session);
  session->send_seq++;

  if (buffer_reinit(session->out_buffer) < 0) {
    rc = SSH_ERROR;
  }
error:
  leave_function();
  return rc; /* SSH_OK, AGAIN or ERROR */
}

#ifdef HAVE_SSH1
static int packet_send1(SSH_SESSION *session) {
  unsigned int blocksize = (session->current_crypto ?
      session->current_crypto->out_cipher->blocksize : 8);
  u32 currentlen = buffer_get_len(session->out_buffer) + sizeof(u32);
  char padstring[32] = {0};
  int rc = SSH_ERROR;
  u32 finallen;
  u32 crc;
  u8 padding;

  enter_function();
  ssh_log(session,SSH_LOG_PACKET,"Sending a %d bytes long packet",currentlen);

/* TODO FIXME
#if defined(HAVE_LIBZ) && defined(WITH_LIBZ)
  if (session->current_crypto && session->current_crypto->do_compress_out) {
    if (compress_buffer(session, session->out_buffer) < 0) {
      goto error;
    }
    currentlen = buffer_get_len(session->out_buffer);
  }
#endif
*/
  padding = blocksize - (currentlen % blocksize);
  if (session->current_crypto) {
    ssh_get_random(padstring, padding, 0);
  } else {
    memset(padstring, 0, padding);
  }

  finallen = htonl(currentlen);
  ssh_log(session, SSH_LOG_PACKET,
      "%d bytes after comp + %d padding bytes = %d bytes packet",
      currentlen, padding, ntohl(finallen));

  if (buffer_add_data_begin(session->out_buffer,i &padstring, padding) < 0) {
    goto error;
  }
  if (buffer_add_data_begin(session->out_buffer, &finallen, sizeof(u32)) < 0) {
    goto error;
  }

  crc = ssh_crc32(buffer_get(session->out_buffer) + sizeof(u32),
      buffer_get_len(session->out_buffer) - sizeof(u32));

  if (buffer_add_u32(session->out_buffer, ntohl(crc)) < 0) {
    goto error;
  }

#ifdef DEBUG_CRYPTO
  ssh_print_hexa("Clear packet", buffer_get(session->out_buffer),
      buffer_get_len(session->out_buffer));
#endif

  packet_encrypt(session, buffer_get(session->out_buffer) + sizeof(u32),
      buffer_get_len(session->out_buffer) - sizeof(u32));

#ifdef DEBUG_CRYPTO
  ssh_print_hexa("encrypted packet",buffer_get(session->out_buffer),
      buffer_get_len(session->out_buffer));
#endif
  if (ssh_socket_write(session->socket, buffer_get(session->out_buffer),
      buffer_get_len(session->out_buffer)) == SSH_ERROR) {
    goto error;
  }

  rc = packet_flush(session, 0);
  session->send_seq++;

  if (buffer_reinit(session->out_buffer) < 0) {
    rc = SSH_ERROR;
  }
error:
  leave_function();
  return rc;     /* SSH_OK, AGAIN or ERROR */
}

#endif /* HAVE_SSH1 */

int packet_send(SSH_SESSION *session) {
#ifdef HAVE_SSH1
  if (session->version == 1) {
    return packet_send1(session);
  }
#endif
  return packet_send2(session);
}

void packet_parse(SSH_SESSION *session) {
  STRING *error_s = NULL;
  char *error = NULL;
  int type = session->in_packet.type;
  u32 tmp;

#ifdef HAVE_SSH1
  if (session->version == 1) {
    /* SSH-1 */
    switch(type) {
      case SSH_MSG_DISCONNECT:
        ssh_log(session, SSH_LOG_PACKET, "Received SSH_MSG_DISCONNECT");
        ssh_set_error(session, SSH_FATAL, "Received SSH_MSG_DISCONNECT");

        ssh_socket_close(session->socket);
        session->alive = 0;
        return;
      case SSH_SMSG_STDOUT_DATA:
      case SSH_SMSG_STDERR_DATA:
      case SSH_SMSG_EXITSTATUS:
        channel_handle1(session,type)
        return;
      case SSH_MSG_DEBUG:
      case SSH_MSG_IGNORE:
        break;
      default:
        ssh_log(session, SSH_LOG_PACKET,
            "Unexpected message code %d", type);
    }
    return;
  } else {
#endif /* HAVE_SSH1 */
    switch(type) {
      case SSH2_MSG_DISCONNECT:
        buffer_get_u32(session->in_buffer, &tmp);
        error_s = buffer_get_ssh_string(session->in_buffer);
        if (error_s == NULL) {
          return;
        }
        error = string_to_char(error_s);
        string_free(error_s);
        if (error == NULL) {
          return;
        }
        ssh_log(session, SSH_LOG_PACKET, "Received SSH_MSG_DISCONNECT\n");
        ssh_set_error(session, SSH_FATAL,
            "Received SSH_MSG_DISCONNECT: %s",error);

        SAFE_FREE(error);

        ssh_socket_close(session->socket);
        session->alive = 0;

        return;
      case SSH2_MSG_CHANNEL_WINDOW_ADJUST:
      case SSH2_MSG_CHANNEL_DATA:
      case SSH2_MSG_CHANNEL_EXTENDED_DATA:
      case SSH2_MSG_CHANNEL_REQUEST:
      case SSH2_MSG_CHANNEL_EOF:
      case SSH2_MSG_CHANNEL_CLOSE:
        channel_handle(session,type);
      case SSH2_MSG_IGNORE:
      case SSH2_MSG_DEBUG:
        return;
      default:
        ssh_log(session, SSH_LOG_RARE, "Received unhandled packet %d", type);
    }
#ifdef HAVE_SSH1
  }
#endif
}

#ifdef HAVE_SSH1
static int packet_wait1(SSH_SESSION *session,int type,int blocking){
	enter_function();
    ssh_log(session,SSH_LOG_PROTOCOL,"packet_wait1 waiting for %d",type);
    while(1){
        if ((packet_read1(session) != SSH_OK) ||
            (packet_translate(session) != SSH_OK)) {
            leave_function();
            return -1;
        }
        ssh_log(session,SSH_LOG_PACKET,"packet_wait 1 received a type %d packet",session->in_packet.type);
        switch(session->in_packet.type){
            case SSH_MSG_DISCONNECT:
                packet_parse(session);
                leave_function();
                return -1;
            case SSH_SMSG_STDOUT_DATA:
            case SSH_SMSG_STDERR_DATA:
            case SSH_SMSG_EXITSTATUS:
                if (channel_handle1(session,type) < 0) {
                  leave_function();
                  return -1;
                }
                break;
            case SSH_MSG_DEBUG:
            case SSH_MSG_IGNORE:
            	break;
/*          case SSH2_MSG_CHANNEL_CLOSE:
               packet_parse(session);
                break;;
*/               
            default:
               if(type && (type != session->in_packet.type)){
                   ssh_set_error(session,SSH_FATAL,"waitpacket(): Received a %d type packet, was waiting for a %d\n",session->in_packet.type,type);
                   leave_function();
                   return -1;
               }
               leave_function();
               return 0;
           }
        if(blocking==0){
            leave_function();
        	return 0;
        }
    }
    leave_function();
    return 0;
}
#endif /* HAVE_SSH1 */
static int packet_wait2(SSH_SESSION *session,int type,int blocking){
    int ret;
    enter_function();
    while(1){
        ret=packet_read2(session);
        if(ret != SSH_OK){
            leave_function();
        	return ret;
        }
        if (packet_translate(session) != SSH_OK) {
            leave_function();
            return SSH_ERROR;
        }
        switch(session->in_packet.type){
           case SSH2_MSG_DISCONNECT:
               packet_parse(session);
               ssh_log(session, SSH_LOG_PACKET, "received disconnect packet");
               leave_function();
               return SSH_ERROR;
           case SSH2_MSG_CHANNEL_WINDOW_ADJUST:
           case SSH2_MSG_CHANNEL_DATA:
           case SSH2_MSG_CHANNEL_EXTENDED_DATA:
           case SSH2_MSG_CHANNEL_REQUEST:
           case SSH2_MSG_CHANNEL_EOF:
           case SSH2_MSG_CHANNEL_CLOSE:
               packet_parse(session);
               break;
           case SSH2_MSG_IGNORE:
               break;
           default:
               if(type && (type != session->in_packet.type)){
                   ssh_set_error(session,SSH_FATAL,"waitpacket(): Received a %d type packet, was waiting for a %d\n",session->in_packet.type,type);
                   leave_function();
                   return SSH_ERROR;
               }
               leave_function();
               return SSH_OK;
           }
        if(blocking==0){
            leave_function();
        	return SSH_OK; //shouldn't it return SSH_AGAIN here ?
        }
    }
    leave_function();
    return SSH_OK;
}
int packet_wait(SSH_SESSION *session, int type, int block){
#ifdef HAVE_SSH1
    if(session->version==1)
        return packet_wait1(session,type,block);
    else
#endif
        return packet_wait2(session,type,block);
}