packet.c - security/openssh-library - Rivoreo Source Code Repositories

 /*
  *
  * packet.c
  *
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  *
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
  *                    All rights reserved
  *
  * Created: Sat Mar 18 02:40:40 1995 ylo
  *
  * This file contains code implementing the packet protocol and communication
  * with the other side.  This same code is used both on client and server side.
  *
  */

 #include "includes.h"
 RCSID("$Id: packet.c,v 1.7 1999/12/06 00:47:29 damien Exp $");

 #include "xmalloc.h"
 #include "buffer.h"
 #include "packet.h"
 #include "bufaux.h"
 #include "ssh.h"
 #include "crc32.h"
 #include "cipher.h"
 #include "getput.h"

 #include "compress.h"
 #include "deattack.h"

 /*
  * This variable contains the file descriptors used for communicating with
  * the other side.  connection_in is used for reading; connection_out for
  * writing.  These can be the same descriptor, in which case it is assumed to
  * be a socket.
  */
 static int connection_in = -1;
 static int connection_out = -1;

 /*
  * Cipher type.  This value is only used to determine whether to pad the
  * packets with zeroes or random data.
  */
 static int cipher_type = SSH_CIPHER_NONE;

 /* Protocol flags for the remote side. */
 static unsigned int remote_protocol_flags = 0;

 /* Encryption context for receiving data.  This is only used for decryption. */
 static CipherContext receive_context;

 /* Encryption context for sending data.  This is only used for encryption. */
 static CipherContext send_context;

 /* Buffer for raw input data from the socket. */
 static Buffer input;

 /* Buffer for raw output data going to the socket. */
 static Buffer output;

 /* Buffer for the partial outgoing packet being constructed. */
 static Buffer outgoing_packet;

 /* Buffer for the incoming packet currently being processed. */
 static Buffer incoming_packet;

 /* Scratch buffer for packet compression/decompression. */
 static Buffer compression_buffer;

 /* Flag indicating whether packet compression/decompression is enabled. */
 static int packet_compression = 0;

 /* default maximum packet size */
 int max_packet_size = 32768;

 /* Flag indicating whether this module has been initialized. */
 static int initialized = 0;

 /* Set to true if the connection is interactive. */
 static int interactive_mode = 0;

 /*
  * Sets the descriptors used for communication.  Disables encryption until
  * packet_set_encryption_key is called.
  */

 void
 packet_set_connection(int fd_in, int fd_out)
 {
 	connection_in = fd_in;
 	connection_out = fd_out;
 	cipher_type = SSH_CIPHER_NONE;
 	cipher_set_key(&send_context, SSH_CIPHER_NONE, (unsigned char *) "", 0, 1);
 	cipher_set_key(&receive_context, SSH_CIPHER_NONE, (unsigned char *) "", 0, 0);
 	if (!initialized) {
 		initialized = 1;
 		buffer_init(&input);
 		buffer_init(&output);
 		buffer_init(&outgoing_packet);
 		buffer_init(&incoming_packet);
 	}
 	/* Kludge: arrange the close function to be called from fatal(). */
 	fatal_add_cleanup((void (*) (void *)) packet_close, NULL);
 }

 /* Sets the connection into non-blocking mode. */

 void
 packet_set_nonblocking()
 {
 	/* Set the socket into non-blocking mode. */
 	if (fcntl(connection_in, F_SETFL, O_NONBLOCK) < 0)
 		error("fcntl O_NONBLOCK: %.100s", strerror(errno));

 	if (connection_out != connection_in) {
 		if (fcntl(connection_out, F_SETFL, O_NONBLOCK) < 0)
 			error("fcntl O_NONBLOCK: %.100s", strerror(errno));
 	}
 }

 /* Returns the socket used for reading. */

 int
 packet_get_connection_in()
 {
 	return connection_in;
 }

 /* Returns the descriptor used for writing. */

 int
 packet_get_connection_out()
 {
 	return connection_out;
 }

 /* Closes the connection and clears and frees internal data structures. */

 void
 packet_close()
 {
 	if (!initialized)
 		return;
 	initialized = 0;
 	if (connection_in == connection_out) {
 		shutdown(connection_out, SHUT_RDWR);
 		close(connection_out);
 	} else {
 		close(connection_in);
 		close(connection_out);
 	}
 	buffer_free(&input);
 	buffer_free(&output);
 	buffer_free(&outgoing_packet);
 	buffer_free(&incoming_packet);
 	if (packet_compression) {
 		buffer_free(&compression_buffer);
 		buffer_compress_uninit();
 	}
 }

 /* Sets remote side protocol flags. */

 void
 packet_set_protocol_flags(unsigned int protocol_flags)
 {
 	remote_protocol_flags = protocol_flags;
 	channel_set_options((protocol_flags & SSH_PROTOFLAG_HOST_IN_FWD_OPEN) != 0);
 }

 /* Returns the remote protocol flags set earlier by the above function. */

 unsigned int
 packet_get_protocol_flags()
 {
 	return remote_protocol_flags;
 }

 /*
  * Starts packet compression from the next packet on in both directions.
  * Level is compression level 1 (fastest) - 9 (slow, best) as in gzip.
  */

 void
 packet_start_compression(int level)
 {
 	if (packet_compression)
 		fatal("Compression already enabled.");
 	packet_compression = 1;
 	buffer_init(&compression_buffer);
 	buffer_compress_init(level);
 }

 /*
  * Encrypts the given number of bytes, copying from src to dest. bytes is
  * known to be a multiple of 8.
  */

 void
 packet_encrypt(CipherContext * cc, void *dest, void *src,
 	       unsigned int bytes)
 {
 	cipher_encrypt(cc, dest, src, bytes);
 }

 /*
  * Decrypts the given number of bytes, copying from src to dest. bytes is
  * known to be a multiple of 8.
  */

 void
 packet_decrypt(CipherContext * cc, void *dest, void *src,
 	       unsigned int bytes)
 {
 	int i;

 	if ((bytes % 8) != 0)
 		fatal("packet_decrypt: bad ciphertext length %d", bytes);

 	/*
 	 * Cryptographic attack detector for ssh - Modifications for packet.c
 	 * (C)1998 CORE-SDI, Buenos Aires Argentina Ariel Futoransky(futo@core-sdi.com)
 	 */

 	switch (cc->type) {
 	case SSH_CIPHER_NONE:
 		i = DEATTACK_OK;
 		break;
 	default:
 		i = detect_attack(src, bytes, NULL);
 		break;
 	}

 	if (i == DEATTACK_DETECTED)
 		packet_disconnect("crc32 compensation attack: network attack detected");

 	cipher_decrypt(cc, dest, src, bytes);
 }

 /*
  * Causes any further packets to be encrypted using the given key.  The same
  * key is used for both sending and reception.  However, both directions are
  * encrypted independently of each other.
  */

 void
 packet_set_encryption_key(const unsigned char *key, unsigned int keylen,
 			  int cipher)
 {
 	/* All other ciphers use the same key in both directions for now. */
 	cipher_set_key(&receive_context, cipher, key, keylen, 0);
 	cipher_set_key(&send_context, cipher, key, keylen, 1);
 }

 /* Starts constructing a packet to send. */

 void
 packet_start(int type)
 {
 	char buf[9];

 	buffer_clear(&outgoing_packet);
 	memset(buf, 0, 8);
 	buf[8] = type;
 	buffer_append(&outgoing_packet, buf, 9);
 }

 /* Appends a character to the packet data. */

 void
 packet_put_char(int value)
 {
 	char ch = value;
 	buffer_append(&outgoing_packet, &ch, 1);
 }

 /* Appends an integer to the packet data. */

 void
 packet_put_int(unsigned int value)
 {
 	buffer_put_int(&outgoing_packet, value);
 }

 /* Appends a string to packet data. */

 void
 packet_put_string(const char *buf, unsigned int len)
 {
 	buffer_put_string(&outgoing_packet, buf, len);
 }

 /* Appends an arbitrary precision integer to packet data. */

 void
 packet_put_bignum(BIGNUM * value)
 {
 	buffer_put_bignum(&outgoing_packet, value);
 }

 /*
  * Finalizes and sends the packet.  If the encryption key has been set,
  * encrypts the packet before sending.
  */

 void
 packet_send()
 {
 	char buf[8], *cp;
 	int i, padding, len;
 	unsigned int checksum;
 	u_int32_t rand = 0;

 	/*
 	 * If using packet compression, compress the payload of the outgoing
 	 * packet.
 	 */
 	if (packet_compression) {
 		buffer_clear(&compression_buffer);
 		/* Skip padding. */
 		buffer_consume(&outgoing_packet, 8);
 		/* padding */
 		buffer_append(&compression_buffer, "\0\0\0\0\0\0\0\0", 8);
 		buffer_compress(&outgoing_packet, &compression_buffer);
 		buffer_clear(&outgoing_packet);
 		buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
 			      buffer_len(&compression_buffer));
 	}
 	/* Compute packet length without padding (add checksum, remove padding). */
 	len = buffer_len(&outgoing_packet) + 4 - 8;

 	/* Insert padding. */
 	padding = 8 - len % 8;
 	if (cipher_type != SSH_CIPHER_NONE) {
 		cp = buffer_ptr(&outgoing_packet);
 		for (i = 0; i < padding; i++) {
 			if (i % 4 == 0)
 				rand = arc4random();
 			cp[7 - i] = rand & 0xff;
 			rand >>= 8;
 		}
 	}
 	buffer_consume(&outgoing_packet, 8 - padding);

 	/* Add check bytes. */
 	checksum = crc32((unsigned char *) buffer_ptr(&outgoing_packet),
 			 buffer_len(&outgoing_packet));
 	PUT_32BIT(buf, checksum);
 	buffer_append(&outgoing_packet, buf, 4);

 #ifdef PACKET_DEBUG
 	fprintf(stderr, "packet_send plain: ");
 	buffer_dump(&outgoing_packet);
 #endif

 	/* Append to output. */
 	PUT_32BIT(buf, len);
 	buffer_append(&output, buf, 4);
 	buffer_append_space(&output, &cp, buffer_len(&outgoing_packet));
 	packet_encrypt(&send_context, cp, buffer_ptr(&outgoing_packet),
 		       buffer_len(&outgoing_packet));

 #ifdef PACKET_DEBUG
 	fprintf(stderr, "encrypted: ");
 	buffer_dump(&output);
 #endif

 	buffer_clear(&outgoing_packet);

 	/*
 	 * Note that the packet is now only buffered in output.  It won\'t be
 	 * actually sent until packet_write_wait or packet_write_poll is
 	 * called.
 	 */
 }

 /*
  * Waits until a packet has been received, and returns its type.  Note that
  * no other data is processed until this returns, so this function should not
  * be used during the interactive session.
  */

 int
 packet_read(int *payload_len_ptr)
 {
 	int type, len;
 	fd_set set;
 	char buf[8192];

 	/* Since we are blocking, ensure that all written packets have been sent. */
 	packet_write_wait();

 	/* Stay in the loop until we have received a complete packet. */
 	for (;;) {
 		/* Try to read a packet from the buffer. */
 		type = packet_read_poll(payload_len_ptr);
 		if (type == SSH_SMSG_SUCCESS
 		    || type == SSH_SMSG_FAILURE
 		    || type == SSH_CMSG_EOF
 		    || type == SSH_CMSG_EXIT_CONFIRMATION)
 			packet_integrity_check(*payload_len_ptr, 0, type);
 		/* If we got a packet, return it. */
 		if (type != SSH_MSG_NONE)
 			return type;
 		/*
 		 * Otherwise, wait for some data to arrive, add it to the
 		 * buffer, and try again.
 		 */
 		FD_ZERO(&set);
 		FD_SET(connection_in, &set);

 		/* Wait for some data to arrive. */
 		select(connection_in + 1, &set, NULL, NULL, NULL);

 		/* Read data from the socket. */
 		len = read(connection_in, buf, sizeof(buf));
 		if (len == 0)
 			fatal("Connection closed by %.200s", get_remote_ipaddr());
 		if (len < 0)
 			fatal("Read from socket failed: %.100s", strerror(errno));
 		/* Append it to the buffer. */
 		packet_process_incoming(buf, len);
 	}
 	/* NOTREACHED */
 }

 /*
  * Waits until a packet has been received, verifies that its type matches
  * that given, and gives a fatal error and exits if there is a mismatch.
  */

 void
 packet_read_expect(int *payload_len_ptr, int expected_type)
 {
 	int type;

 	type = packet_read(payload_len_ptr);
 	if (type != expected_type)
 		packet_disconnect("Protocol error: expected packet type %d, got %d",
 				  expected_type, type);
 }

 /* Checks if a full packet is available in the data received so far via
  * packet_process_incoming.  If so, reads the packet; otherwise returns
  * SSH_MSG_NONE.  This does not wait for data from the connection.
  *
  * SSH_MSG_DISCONNECT is handled specially here.  Also,
  * SSH_MSG_IGNORE messages are skipped by this function and are never returned
  * to higher levels.
  *
  * The returned payload_len does include space consumed by:
  * 	Packet length
  * 	Padding
  * 	Packet type
  * 	Check bytes
  */

 int
 packet_read_poll(int *payload_len_ptr)
 {
 	unsigned int len, padded_len;
 	unsigned char *ucp;
 	char buf[8], *cp;
 	unsigned int checksum, stored_checksum;

 restart:

 	/* Check if input size is less than minimum packet size. */
 	if (buffer_len(&input) < 4 + 8)
 		return SSH_MSG_NONE;
 	/* Get length of incoming packet. */
 	ucp = (unsigned char *) buffer_ptr(&input);
 	len = GET_32BIT(ucp);
 	if (len < 1 + 2 + 2 || len > 256 * 1024)
 		packet_disconnect("Bad packet length %d.", len);
 	padded_len = (len + 8) & ~7;

 	/* Check if the packet has been entirely received. */
 	if (buffer_len(&input) < 4 + padded_len)
 		return SSH_MSG_NONE;

 	/* The entire packet is in buffer. */

 	/* Consume packet length. */
 	buffer_consume(&input, 4);

 	/* Copy data to incoming_packet. */
 	buffer_clear(&incoming_packet);
 	buffer_append_space(&incoming_packet, &cp, padded_len);
 	packet_decrypt(&receive_context, cp, buffer_ptr(&input), padded_len);
 	buffer_consume(&input, padded_len);

 #ifdef PACKET_DEBUG
 	fprintf(stderr, "read_poll plain: ");
 	buffer_dump(&incoming_packet);
 #endif

 	/* Compute packet checksum. */
 	checksum = crc32((unsigned char *) buffer_ptr(&incoming_packet),
 			 buffer_len(&incoming_packet) - 4);

 	/* Skip padding. */
 	buffer_consume(&incoming_packet, 8 - len % 8);

 	/* Test check bytes. */

 	if (len != buffer_len(&incoming_packet))
 		packet_disconnect("packet_read_poll: len %d != buffer_len %d.",
 				  len, buffer_len(&incoming_packet));

 	ucp = (unsigned char *) buffer_ptr(&incoming_packet) + len - 4;
 	stored_checksum = GET_32BIT(ucp);
 	if (checksum != stored_checksum)
 		packet_disconnect("Corrupted check bytes on input.");
 	buffer_consume_end(&incoming_packet, 4);

 	/* If using packet compression, decompress the packet. */
 	if (packet_compression) {
 		buffer_clear(&compression_buffer);
 		buffer_uncompress(&incoming_packet, &compression_buffer);
 		buffer_clear(&incoming_packet);
 		buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
 			      buffer_len(&compression_buffer));
 	}
 	/* Get packet type. */
 	buffer_get(&incoming_packet, &buf[0], 1);

 	/* Return length of payload (without type field). */
 	*payload_len_ptr = buffer_len(&incoming_packet);

 	/* Handle disconnect message. */
 	if ((unsigned char) buf[0] == SSH_MSG_DISCONNECT) {
 		log("Received disconnect: %.900s", packet_get_string(NULL));
 		fatal_cleanup();
 	}

 	/* Ignore ignore messages. */
 	if ((unsigned char) buf[0] == SSH_MSG_IGNORE)
 		goto restart;

 	/* Send debug messages as debugging output. */
 	if ((unsigned char) buf[0] == SSH_MSG_DEBUG) {
 		debug("Remote: %.900s", packet_get_string(NULL));
 		goto restart;
 	}
 	/* Return type. */
 	return (unsigned char) buf[0];
 }

 /*
  * Buffers the given amount of input characters.  This is intended to be used
  * together with packet_read_poll.
  */

 void
 packet_process_incoming(const char *buf, unsigned int len)
 {
 	buffer_append(&input, buf, len);
 }

 /* Returns a character from the packet. */

 unsigned int
 packet_get_char()
 {
 	char ch;
 	buffer_get(&incoming_packet, &ch, 1);
 	return (unsigned char) ch;
 }

 /* Returns an integer from the packet data. */

 unsigned int
 packet_get_int()
 {
 	return buffer_get_int(&incoming_packet);
 }

 /*
  * Returns an arbitrary precision integer from the packet data.  The integer
  * must have been initialized before this call.
  */

 void
 packet_get_bignum(BIGNUM * value, int *length_ptr)
 {
 	*length_ptr = buffer_get_bignum(&incoming_packet, value);
 }

 /*
  * Returns a string from the packet data.  The string is allocated using
  * xmalloc; it is the responsibility of the calling program to free it when
  * no longer needed.  The length_ptr argument may be NULL, or point to an
  * integer into which the length of the string is stored.
  */

 char *
 packet_get_string(unsigned int *length_ptr)
 {
 	return buffer_get_string(&incoming_packet, length_ptr);
 }

 /*
  * Sends a diagnostic message from the server to the client.  This message
  * can be sent at any time (but not while constructing another message). The
  * message is printed immediately, but only if the client is being executed
  * in verbose mode.  These messages are primarily intended to ease debugging
  * authentication problems.   The length of the formatted message must not
  * exceed 1024 bytes.  This will automatically call packet_write_wait.
  */

 void
 packet_send_debug(const char *fmt,...)
 {
 	char buf[1024];
 	va_list args;

 	va_start(args, fmt);
 	vsnprintf(buf, sizeof(buf), fmt, args);
 	va_end(args);

 	packet_start(SSH_MSG_DEBUG);
 	packet_put_string(buf, strlen(buf));
 	packet_send();
 	packet_write_wait();
 }

 /*
  * Logs the error plus constructs and sends a disconnect packet, closes the
  * connection, and exits.  This function never returns. The error message
  * should not contain a newline.  The length of the formatted message must
  * not exceed 1024 bytes.
  */

 void
 packet_disconnect(const char *fmt,...)
 {
 	char buf[1024];
 	va_list args;
 	static int disconnecting = 0;
 	if (disconnecting)	/* Guard against recursive invocations. */
 		fatal("packet_disconnect called recursively.");
 	disconnecting = 1;

 	/*
 	 * Format the message.  Note that the caller must make sure the
 	 * message is of limited size.
 	 */
 	va_start(args, fmt);
 	vsnprintf(buf, sizeof(buf), fmt, args);
 	va_end(args);

 	/* Send the disconnect message to the other side, and wait for it to get sent. */
 	packet_start(SSH_MSG_DISCONNECT);
 	packet_put_string(buf, strlen(buf));
 	packet_send();
 	packet_write_wait();

 	/* Stop listening for connections. */
 	channel_stop_listening();

 	/* Close the connection. */
 	packet_close();

 	/* Display the error locally and exit. */
 	log("Disconnecting: %.100s", buf);
 	fatal_cleanup();
 }

 /* Checks if there is any buffered output, and tries to write some of the output. */

 void
 packet_write_poll()
 {
 	int len = buffer_len(&output);
 	if (len > 0) {
 		len = write(connection_out, buffer_ptr(&output), len);
 		if (len <= 0) {
 			if (errno == EAGAIN)
 				return;
 			else
 				fatal("Write failed: %.100s", strerror(errno));
 		}
 		buffer_consume(&output, len);
 	}
 }

 /*
  * Calls packet_write_poll repeatedly until all pending output data has been
  * written.
  */

 void
 packet_write_wait()
 {
 	packet_write_poll();
 	while (packet_have_data_to_write()) {
 		fd_set set;
 		FD_ZERO(&set);
 		FD_SET(connection_out, &set);
 		select(connection_out + 1, NULL, &set, NULL, NULL);
 		packet_write_poll();
 	}
 }

 /* Returns true if there is buffered data to write to the connection. */

 int
 packet_have_data_to_write()
 {
 	return buffer_len(&output) != 0;
 }

 /* Returns true if there is not too much data to write to the connection. */

 int
 packet_not_very_much_data_to_write()
 {
 	if (interactive_mode)
 		return buffer_len(&output) < 16384;
 	else
 		return buffer_len(&output) < 128 * 1024;
 }

 /* Informs that the current session is interactive.  Sets IP flags for that. */

 void
 packet_set_interactive(int interactive, int keepalives)
 {
 	int on = 1;

 	/* Record that we are in interactive mode. */
 	interactive_mode = interactive;

 	/*
 	 * Only set socket options if using a socket (as indicated by the
 	 * descriptors being the same).
 	 */
 	if (connection_in != connection_out)
 		return;

 	if (keepalives) {
 		/* Set keepalives if requested. */
 		if (setsockopt(connection_in, SOL_SOCKET, SO_KEEPALIVE, (void *) &on,
 			       sizeof(on)) < 0)
 			error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
 	}
 	if (interactive) {
 		/*
 		 * Set IP options for an interactive connection.  Use
 		 * IPTOS_LOWDELAY and TCP_NODELAY.
 		 */
 		int lowdelay = IPTOS_LOWDELAY;
 		if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &lowdelay,
 			       sizeof(lowdelay)) < 0)
 			error("setsockopt IPTOS_LOWDELAY: %.100s", strerror(errno));
 		if (setsockopt(connection_in, IPPROTO_TCP, TCP_NODELAY, (void *) &on,
 			       sizeof(on)) < 0)
 			error("setsockopt TCP_NODELAY: %.100s", strerror(errno));
 	} else {
 		/*
 		 * Set IP options for a non-interactive connection.  Use
 		 * IPTOS_THROUGHPUT.
 		 */
 		int throughput = IPTOS_THROUGHPUT;
 		if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &throughput,
 			       sizeof(throughput)) < 0)
 			error("setsockopt IPTOS_THROUGHPUT: %.100s", strerror(errno));
 	}
 }

 /* Returns true if the current connection is interactive. */

 int
 packet_is_interactive()
 {
 	return interactive_mode;
 }

 int
 packet_set_maxsize(int s)
 {
 	static int called = 0;
 	if (called) {
 		log("packet_set_maxsize: called twice: old %d new %d", max_packet_size, s);
 		return -1;
 	}
 	if (s < 4 * 1024 || s > 1024 * 1024) {
 		log("packet_set_maxsize: bad size %d", s);
 		return -1;
 	}
 	log("packet_set_maxsize: setting to %d", s);
 	max_packet_size = s;
 	return s;
 }
	/*
	*
	* packet.c
	*
	* Author: Tatu Ylonen <ylo@cs.hut.fi>
	*
	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
	* All rights reserved
	*
	* Created: Sat Mar 18 02:40:40 1995 ylo
	*
	* This file contains code implementing the packet protocol and communication
	* with the other side. This same code is used both on client and server side.
	*
	*/

	#include "includes.h"
	RCSID("$Id: packet.c,v 1.7 1999/12/06 00:47:29 damien Exp $");

	#include "xmalloc.h"
	#include "buffer.h"
	#include "packet.h"
	#include "bufaux.h"
	#include "ssh.h"
	#include "crc32.h"
	#include "cipher.h"
	#include "getput.h"

	#include "compress.h"
	#include "deattack.h"

	/*
	* This variable contains the file descriptors used for communicating with
	* the other side. connection_in is used for reading; connection_out for
	* writing. These can be the same descriptor, in which case it is assumed to
	* be a socket.
	*/
	static int connection_in = -1;
	static int connection_out = -1;

	/*
	* Cipher type. This value is only used to determine whether to pad the
	* packets with zeroes or random data.
	*/
	static int cipher_type = SSH_CIPHER_NONE;

	/* Protocol flags for the remote side. */
	static unsigned int remote_protocol_flags = 0;

	/* Encryption context for receiving data. This is only used for decryption. */
	static CipherContext receive_context;

	/* Encryption context for sending data. This is only used for encryption. */
	static CipherContext send_context;

	/* Buffer for raw input data from the socket. */
	static Buffer input;

	/* Buffer for raw output data going to the socket. */
	static Buffer output;

	/* Buffer for the partial outgoing packet being constructed. */
	static Buffer outgoing_packet;

	/* Buffer for the incoming packet currently being processed. */
	static Buffer incoming_packet;

	/* Scratch buffer for packet compression/decompression. */
	static Buffer compression_buffer;

	/* Flag indicating whether packet compression/decompression is enabled. */
	static int packet_compression = 0;

	/* default maximum packet size */
	int max_packet_size = 32768;

	/* Flag indicating whether this module has been initialized. */
	static int initialized = 0;

	/* Set to true if the connection is interactive. */
	static int interactive_mode = 0;

	/*
	* Sets the descriptors used for communication. Disables encryption until
	* packet_set_encryption_key is called.
	*/

	void
	packet_set_connection(int fd_in, int fd_out)
	{
	connection_in = fd_in;
	connection_out = fd_out;
	cipher_type = SSH_CIPHER_NONE;
	cipher_set_key(&send_context, SSH_CIPHER_NONE, (unsigned char *) "", 0, 1);
	cipher_set_key(&receive_context, SSH_CIPHER_NONE, (unsigned char *) "", 0, 0);
	if (!initialized) {
	initialized = 1;
	buffer_init(&input);
	buffer_init(&output);
	buffer_init(&outgoing_packet);
	buffer_init(&incoming_packet);
	}
	/* Kludge: arrange the close function to be called from fatal(). */
	fatal_add_cleanup((void () (void )) packet_close, NULL);
	}

	/* Sets the connection into non-blocking mode. */

	void
	packet_set_nonblocking()
	{
	/* Set the socket into non-blocking mode. */
	if (fcntl(connection_in, F_SETFL, O_NONBLOCK) < 0)
	error("fcntl O_NONBLOCK: %.100s", strerror(errno));

	if (connection_out != connection_in) {
	if (fcntl(connection_out, F_SETFL, O_NONBLOCK) < 0)
	error("fcntl O_NONBLOCK: %.100s", strerror(errno));
	}
	}

	/* Returns the socket used for reading. */

	int
	packet_get_connection_in()
	{
	return connection_in;
	}

	/* Returns the descriptor used for writing. */

	int
	packet_get_connection_out()
	{
	return connection_out;
	}

	/* Closes the connection and clears and frees internal data structures. */

	void
	packet_close()
	{
	if (!initialized)
	return;
	initialized = 0;
	if (connection_in == connection_out) {
	shutdown(connection_out, SHUT_RDWR);
	close(connection_out);
	} else {
	close(connection_in);
	close(connection_out);
	}
	buffer_free(&input);
	buffer_free(&output);
	buffer_free(&outgoing_packet);
	buffer_free(&incoming_packet);
	if (packet_compression) {
	buffer_free(&compression_buffer);
	buffer_compress_uninit();
	}
	}

	/* Sets remote side protocol flags. */

	void
	packet_set_protocol_flags(unsigned int protocol_flags)
	{
	remote_protocol_flags = protocol_flags;
	channel_set_options((protocol_flags & SSH_PROTOFLAG_HOST_IN_FWD_OPEN) != 0);
	}

	/* Returns the remote protocol flags set earlier by the above function. */

	unsigned int
	packet_get_protocol_flags()
	{
	return remote_protocol_flags;
	}

	/*
	* Starts packet compression from the next packet on in both directions.
	* Level is compression level 1 (fastest) - 9 (slow, best) as in gzip.
	*/

	void
	packet_start_compression(int level)
	{
	if (packet_compression)
	fatal("Compression already enabled.");
	packet_compression = 1;
	buffer_init(&compression_buffer);
	buffer_compress_init(level);
	}

	/*
	* Encrypts the given number of bytes, copying from src to dest. bytes is
	* known to be a multiple of 8.
	*/

	void
	packet_encrypt(CipherContext * cc, void dest, void src,
	unsigned int bytes)
	{
	cipher_encrypt(cc, dest, src, bytes);
	}

	/*
	* Decrypts the given number of bytes, copying from src to dest. bytes is
	* known to be a multiple of 8.
	*/

	void
	packet_decrypt(CipherContext * cc, void dest, void src,
	unsigned int bytes)
	{
	int i;

	if ((bytes % 8) != 0)
	fatal("packet_decrypt: bad ciphertext length %d", bytes);

	/*
	* Cryptographic attack detector for ssh - Modifications for packet.c
	* (C)1998 CORE-SDI, Buenos Aires Argentina Ariel Futoransky(futo@core-sdi.com)
	*/

	switch (cc->type) {
	case SSH_CIPHER_NONE:
	i = DEATTACK_OK;
	break;
	default:
	i = detect_attack(src, bytes, NULL);
	break;
	}

	if (i == DEATTACK_DETECTED)
	packet_disconnect("crc32 compensation attack: network attack detected");

	cipher_decrypt(cc, dest, src, bytes);
	}

	/*
	* Causes any further packets to be encrypted using the given key. The same
	* key is used for both sending and reception. However, both directions are
	* encrypted independently of each other.
	*/

	void
	packet_set_encryption_key(const unsigned char *key, unsigned int keylen,
	int cipher)
	{
	/* All other ciphers use the same key in both directions for now. */
	cipher_set_key(&receive_context, cipher, key, keylen, 0);
	cipher_set_key(&send_context, cipher, key, keylen, 1);
	}

	/* Starts constructing a packet to send. */

	void
	packet_start(int type)
	{
	char buf[9];

	buffer_clear(&outgoing_packet);
	memset(buf, 0, 8);
	buf[8] = type;
	buffer_append(&outgoing_packet, buf, 9);
	}

	/* Appends a character to the packet data. */

	void
	packet_put_char(int value)
	{
	char ch = value;
	buffer_append(&outgoing_packet, &ch, 1);
	}

	/* Appends an integer to the packet data. */

	void
	packet_put_int(unsigned int value)
	{
	buffer_put_int(&outgoing_packet, value);
	}

	/* Appends a string to packet data. */

	void
	packet_put_string(const char *buf, unsigned int len)
	{
	buffer_put_string(&outgoing_packet, buf, len);
	}

	/* Appends an arbitrary precision integer to packet data. */

	void
	packet_put_bignum(BIGNUM * value)
	{
	buffer_put_bignum(&outgoing_packet, value);
	}

	/*
	* Finalizes and sends the packet. If the encryption key has been set,
	* encrypts the packet before sending.
	*/

	void
	packet_send()
	{
	char buf[8], *cp;
	int i, padding, len;
	unsigned int checksum;
	u_int32_t rand = 0;

	/*
	* If using packet compression, compress the payload of the outgoing
	* packet.
	*/
	if (packet_compression) {
	buffer_clear(&compression_buffer);
	/* Skip padding. */
	buffer_consume(&outgoing_packet, 8);
	/* padding */
	buffer_append(&compression_buffer, "\0\0\0\0\0\0\0\0", 8);
	buffer_compress(&outgoing_packet, &compression_buffer);
	buffer_clear(&outgoing_packet);
	buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
	buffer_len(&compression_buffer));
	}
	/* Compute packet length without padding (add checksum, remove padding). */
	len = buffer_len(&outgoing_packet) + 4 - 8;

	/* Insert padding. */
	padding = 8 - len % 8;
	if (cipher_type != SSH_CIPHER_NONE) {
	cp = buffer_ptr(&outgoing_packet);
	for (i = 0; i < padding; i++) {
	if (i % 4 == 0)
	rand = arc4random();
	cp[7 - i] = rand & 0xff;
	rand >>= 8;
	}
	}
	buffer_consume(&outgoing_packet, 8 - padding);

	/* Add check bytes. */
	checksum = crc32((unsigned char *) buffer_ptr(&outgoing_packet),
	buffer_len(&outgoing_packet));
	PUT_32BIT(buf, checksum);
	buffer_append(&outgoing_packet, buf, 4);

	#ifdef PACKET_DEBUG
	fprintf(stderr, "packet_send plain: ");
	buffer_dump(&outgoing_packet);
	#endif

	/* Append to output. */
	PUT_32BIT(buf, len);
	buffer_append(&output, buf, 4);
	buffer_append_space(&output, &cp, buffer_len(&outgoing_packet));
	packet_encrypt(&send_context, cp, buffer_ptr(&outgoing_packet),
	buffer_len(&outgoing_packet));

	#ifdef PACKET_DEBUG
	fprintf(stderr, "encrypted: ");
	buffer_dump(&output);
	#endif

	buffer_clear(&outgoing_packet);

	/*
	* Note that the packet is now only buffered in output. It won\'t be
	* actually sent until packet_write_wait or packet_write_poll is
	* called.
	*/
	}

	/*
	* Waits until a packet has been received, and returns its type. Note that
	* no other data is processed until this returns, so this function should not
	* be used during the interactive session.
	*/

	int
	packet_read(int *payload_len_ptr)
	{
	int type, len;
	fd_set set;
	char buf[8192];

	/* Since we are blocking, ensure that all written packets have been sent. */
	packet_write_wait();

	/* Stay in the loop until we have received a complete packet. */
	for (;;) {
	/* Try to read a packet from the buffer. */
	type = packet_read_poll(payload_len_ptr);
	if (type == SSH_SMSG_SUCCESS
	\|\| type == SSH_SMSG_FAILURE
	\|\| type == SSH_CMSG_EOF
	\|\| type == SSH_CMSG_EXIT_CONFIRMATION)
	packet_integrity_check(*payload_len_ptr, 0, type);
	/* If we got a packet, return it. */
	if (type != SSH_MSG_NONE)
	return type;
	/*
	* Otherwise, wait for some data to arrive, add it to the
	* buffer, and try again.
	*/
	FD_ZERO(&set);
	FD_SET(connection_in, &set);

	/* Wait for some data to arrive. */
	select(connection_in + 1, &set, NULL, NULL, NULL);

	/* Read data from the socket. */
	len = read(connection_in, buf, sizeof(buf));
	if (len == 0)
	fatal("Connection closed by %.200s", get_remote_ipaddr());
	if (len < 0)
	fatal("Read from socket failed: %.100s", strerror(errno));
	/* Append it to the buffer. */
	packet_process_incoming(buf, len);
	}
	/* NOTREACHED */
	}

	/*
	* Waits until a packet has been received, verifies that its type matches
	* that given, and gives a fatal error and exits if there is a mismatch.
	*/

	void
	packet_read_expect(int *payload_len_ptr, int expected_type)
	{
	int type;

	type = packet_read(payload_len_ptr);
	if (type != expected_type)
	packet_disconnect("Protocol error: expected packet type %d, got %d",
	expected_type, type);
	}

	/* Checks if a full packet is available in the data received so far via
	* packet_process_incoming. If so, reads the packet; otherwise returns
	* SSH_MSG_NONE. This does not wait for data from the connection.
	*
	* SSH_MSG_DISCONNECT is handled specially here. Also,
	* SSH_MSG_IGNORE messages are skipped by this function and are never returned
	* to higher levels.
	*
	* The returned payload_len does include space consumed by:
	* Packet length
	* Padding
	* Packet type
	* Check bytes
	*/

	int
	packet_read_poll(int *payload_len_ptr)
	{
	unsigned int len, padded_len;
	unsigned char *ucp;
	char buf[8], *cp;
	unsigned int checksum, stored_checksum;

	restart:

	/* Check if input size is less than minimum packet size. */
	if (buffer_len(&input) < 4 + 8)
	return SSH_MSG_NONE;
	/* Get length of incoming packet. */
	ucp = (unsigned char *) buffer_ptr(&input);
	len = GET_32BIT(ucp);
	if (len < 1 + 2 + 2 \|\| len > 256 * 1024)
	packet_disconnect("Bad packet length %d.", len);
	padded_len = (len + 8) & ~7;

	/* Check if the packet has been entirely received. */
	if (buffer_len(&input) < 4 + padded_len)
	return SSH_MSG_NONE;

	/* The entire packet is in buffer. */

	/* Consume packet length. */
	buffer_consume(&input, 4);

	/* Copy data to incoming_packet. */
	buffer_clear(&incoming_packet);
	buffer_append_space(&incoming_packet, &cp, padded_len);
	packet_decrypt(&receive_context, cp, buffer_ptr(&input), padded_len);
	buffer_consume(&input, padded_len);

	#ifdef PACKET_DEBUG
	fprintf(stderr, "read_poll plain: ");
	buffer_dump(&incoming_packet);
	#endif

	/* Compute packet checksum. */
	checksum = crc32((unsigned char *) buffer_ptr(&incoming_packet),
	buffer_len(&incoming_packet) - 4);

	/* Skip padding. */
	buffer_consume(&incoming_packet, 8 - len % 8);

	/* Test check bytes. */

	if (len != buffer_len(&incoming_packet))
	packet_disconnect("packet_read_poll: len %d != buffer_len %d.",
	len, buffer_len(&incoming_packet));

	ucp = (unsigned char *) buffer_ptr(&incoming_packet) + len - 4;
	stored_checksum = GET_32BIT(ucp);
	if (checksum != stored_checksum)
	packet_disconnect("Corrupted check bytes on input.");
	buffer_consume_end(&incoming_packet, 4);

	/* If using packet compression, decompress the packet. */
	if (packet_compression) {
	buffer_clear(&compression_buffer);
	buffer_uncompress(&incoming_packet, &compression_buffer);
	buffer_clear(&incoming_packet);
	buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
	buffer_len(&compression_buffer));
	}
	/* Get packet type. */
	buffer_get(&incoming_packet, &buf[0], 1);

	/* Return length of payload (without type field). */
	*payload_len_ptr = buffer_len(&incoming_packet);

	/* Handle disconnect message. */
	if ((unsigned char) buf[0] == SSH_MSG_DISCONNECT) {
	log("Received disconnect: %.900s", packet_get_string(NULL));
	fatal_cleanup();
	}

	/* Ignore ignore messages. */
	if ((unsigned char) buf[0] == SSH_MSG_IGNORE)
	goto restart;

	/* Send debug messages as debugging output. */
	if ((unsigned char) buf[0] == SSH_MSG_DEBUG) {
	debug("Remote: %.900s", packet_get_string(NULL));
	goto restart;
	}
	/* Return type. */
	return (unsigned char) buf[0];
	}

	/*
	* Buffers the given amount of input characters. This is intended to be used
	* together with packet_read_poll.
	*/

	void
	packet_process_incoming(const char *buf, unsigned int len)
	{
	buffer_append(&input, buf, len);
	}

	/* Returns a character from the packet. */

	unsigned int
	packet_get_char()
	{
	char ch;
	buffer_get(&incoming_packet, &ch, 1);
	return (unsigned char) ch;
	}

	/* Returns an integer from the packet data. */

	unsigned int
	packet_get_int()
	{
	return buffer_get_int(&incoming_packet);
	}

	/*
	* Returns an arbitrary precision integer from the packet data. The integer
	* must have been initialized before this call.
	*/

	void
	packet_get_bignum(BIGNUM * value, int *length_ptr)
	{
	*length_ptr = buffer_get_bignum(&incoming_packet, value);
	}

	/*
	* Returns a string from the packet data. The string is allocated using
	* xmalloc; it is the responsibility of the calling program to free it when
	* no longer needed. The length_ptr argument may be NULL, or point to an
	* integer into which the length of the string is stored.
	*/

	char *
	packet_get_string(unsigned int *length_ptr)
	{
	return buffer_get_string(&incoming_packet, length_ptr);
	}

	/*
	* Sends a diagnostic message from the server to the client. This message
	* can be sent at any time (but not while constructing another message). The
	* message is printed immediately, but only if the client is being executed
	* in verbose mode. These messages are primarily intended to ease debugging
	* authentication problems. The length of the formatted message must not
	* exceed 1024 bytes. This will automatically call packet_write_wait.
	*/

	void
	packet_send_debug(const char *fmt,...)
	{
	char buf[1024];
	va_list args;

	va_start(args, fmt);
	vsnprintf(buf, sizeof(buf), fmt, args);
	va_end(args);

	packet_start(SSH_MSG_DEBUG);
	packet_put_string(buf, strlen(buf));
	packet_send();
	packet_write_wait();
	}

	/*
	* Logs the error plus constructs and sends a disconnect packet, closes the
	* connection, and exits. This function never returns. The error message
	* should not contain a newline. The length of the formatted message must
	* not exceed 1024 bytes.
	*/

	void
	packet_disconnect(const char *fmt,...)
	{
	char buf[1024];
	va_list args;
	static int disconnecting = 0;
	if (disconnecting) /* Guard against recursive invocations. */
	fatal("packet_disconnect called recursively.");
	disconnecting = 1;

	/*
	* Format the message. Note that the caller must make sure the
	* message is of limited size.
	*/
	va_start(args, fmt);
	vsnprintf(buf, sizeof(buf), fmt, args);
	va_end(args);

	/* Send the disconnect message to the other side, and wait for it to get sent. */
	packet_start(SSH_MSG_DISCONNECT);
	packet_put_string(buf, strlen(buf));
	packet_send();
	packet_write_wait();

	/* Stop listening for connections. */
	channel_stop_listening();

	/* Close the connection. */
	packet_close();

	/* Display the error locally and exit. */
	log("Disconnecting: %.100s", buf);
	fatal_cleanup();
	}

	/* Checks if there is any buffered output, and tries to write some of the output. */

	void
	packet_write_poll()
	{
	int len = buffer_len(&output);
	if (len > 0) {
	len = write(connection_out, buffer_ptr(&output), len);
	if (len <= 0) {
	if (errno == EAGAIN)
	return;
	else
	fatal("Write failed: %.100s", strerror(errno));
	}
	buffer_consume(&output, len);
	}
	}

	/*
	* Calls packet_write_poll repeatedly until all pending output data has been
	* written.
	*/

	void
	packet_write_wait()
	{
	packet_write_poll();
	while (packet_have_data_to_write()) {
	fd_set set;
	FD_ZERO(&set);
	FD_SET(connection_out, &set);
	select(connection_out + 1, NULL, &set, NULL, NULL);
	packet_write_poll();
	}
	}

	/* Returns true if there is buffered data to write to the connection. */

	int
	packet_have_data_to_write()
	{
	return buffer_len(&output) != 0;
	}

	/* Returns true if there is not too much data to write to the connection. */

	int
	packet_not_very_much_data_to_write()
	{
	if (interactive_mode)
	return buffer_len(&output) < 16384;
	else
	return buffer_len(&output) < 128 * 1024;
	}

	/* Informs that the current session is interactive. Sets IP flags for that. */

	void
	packet_set_interactive(int interactive, int keepalives)
	{
	int on = 1;

	/* Record that we are in interactive mode. */
	interactive_mode = interactive;

	/*
	* Only set socket options if using a socket (as indicated by the
	* descriptors being the same).
	*/
	if (connection_in != connection_out)
	return;

	if (keepalives) {
	/* Set keepalives if requested. */
	if (setsockopt(connection_in, SOL_SOCKET, SO_KEEPALIVE, (void *) &on,
	sizeof(on)) < 0)
	error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
	}
	if (interactive) {
	/*
	* Set IP options for an interactive connection. Use
	* IPTOS_LOWDELAY and TCP_NODELAY.
	*/
	int lowdelay = IPTOS_LOWDELAY;
	if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &lowdelay,
	sizeof(lowdelay)) < 0)
	error("setsockopt IPTOS_LOWDELAY: %.100s", strerror(errno));
	if (setsockopt(connection_in, IPPROTO_TCP, TCP_NODELAY, (void *) &on,
	sizeof(on)) < 0)
	error("setsockopt TCP_NODELAY: %.100s", strerror(errno));
	} else {
	/*
	* Set IP options for a non-interactive connection. Use
	* IPTOS_THROUGHPUT.
	*/
	int throughput = IPTOS_THROUGHPUT;
	if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &throughput,
	sizeof(throughput)) < 0)
	error("setsockopt IPTOS_THROUGHPUT: %.100s", strerror(errno));
	}
	}

	/* Returns true if the current connection is interactive. */

	int
	packet_is_interactive()
	{
	return interactive_mode;
	}

	int
	packet_set_maxsize(int s)
	{
	static int called = 0;
	if (called) {
	log("packet_set_maxsize: called twice: old %d new %d", max_packet_size, s);
	return -1;
	}
	if (s < 4 * 1024 \|\| s > 1024 * 1024) {
	log("packet_set_maxsize: bad size %d", s);
	return -1;
	}
	log("packet_set_maxsize: setting to %d", s);
	max_packet_size = s;
	return s;
	}