packet.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
* 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.
*
* As far as I am concerned, the code I have written for this software
* can be used freely for any purpose. Any derived versions of this
* software must be clearly marked as such, and if the derived work is
* incompatible with the protocol description in the RFC file, it must be
* called by a name other than "ssh" or "Secure Shell".
*
*
* SSH2 packet format added by Markus Friedl.
* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#include "includes.h"
#pragma ident "%Z%%M% %I% %E% SMI"
#include "xmalloc.h"
#include "buffer.h"
#include "packet.h"
#include "bufaux.h"
#include "crc32.h"
#include "getput.h"
#include "compress.h"
#include "deattack.h"
#include "channels.h"
#include "compat.h"
#include "ssh1.h"
#include "ssh2.h"
#include "cipher.h"
#include "kex.h"
#include "mac.h"
#include "log.h"
#include "canohost.h"
#include "misc.h"
#include "ssh.h"
#ifdef ALTPRIVSEP
static int packet_server = 0;
static int packet_monitor = 0;
#endif /* ALTPRIVSEP */
#ifdef PACKET_DEBUG
#define DBG(x) x
#else
#define DBG(x)
#endif
/*
* 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;
/* Protocol flags for the remote side. */
static u_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. */
/* Buffer for raw output data going to the socket. */
/* 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;
static int compression_buffer_ready = 0;
/* 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;
/* Session key information for Encryption and MAC */
static u_int32_t read_seqnr = 0;
static u_int32_t send_seqnr = 0;
/* Session key for protocol v1 */
static u_int ssh1_keylen;
/* roundup current message to extra_pad bytes */
/*
* Sets the descriptors used for communication. Disables encryption until
* packet_set_encryption_key is called.
*/
void
{
fatal("packet_set_connection: cannot load cipher 'none'");
if (!initialized) {
initialized = 1;
buffer_init(&input);
} else {
}
/*
* Prime the cache for get_remote_ipaddr() while we have a
* socket on which to do a getpeername().
*/
(void) get_remote_ipaddr();
/* Kludge: arrange the close function to be called from fatal(). */
}
/* Returns 1 if remote host is connected via socket, 0 if not. */
int
{
/* filedescriptors in and out are the same, so it's a socket */
return 1;
return 0;
return 0;
return 0;
return 0;
return 1;
}
/*
* Exports an IV from the CipherContext required to export the key
* state back from the unprivileged child to the privileged parent
* process.
*/
void
{
cc = &send_context;
else
cc = &receive_context;
}
int
{
cc = &send_context;
else
cc = &receive_context;
}
void
{
cc = &send_context;
else
cc = &receive_context;
}
int
packet_get_keyiv_len(int mode)
{
cc = &send_context;
else
cc = &receive_context;
return (cipher_get_keyiv_len(cc));
}
void
{
cc = &send_context;
else
cc = &receive_context;
}
int
{
}
packet_get_seqnr(int mode)
{
}
void
{
read_seqnr = seqnr;
send_seqnr = seqnr;
else
}
/* returns 1 if connection is via ipv4 */
int
{
struct sockaddr_storage to;
return 0;
return 1;
#ifdef IPV4_IN_IPV6
return 1;
#endif
return 0;
}
/* Sets the connection into non-blocking mode. */
void
packet_set_nonblocking(void)
{
/* Set the socket into non-blocking mode. */
if (connection_out != connection_in) {
}
}
/* Returns the socket used for reading. */
int
packet_get_connection_in(void)
{
return connection_in;
}
/* Returns the descriptor used for writing. */
int
{
return connection_out;
}
/* Closes the connection and clears and frees internal data structures. */
void
packet_close(void)
{
if (!initialized)
return;
initialized = 0;
if (connection_in == connection_out) {
} else {
}
buffer_free(&input);
if (compression_buffer_ready) {
}
}
/* Sets remote side protocol flags. */
void
{
}
/* Returns the remote protocol flags set earlier by the above function. */
{
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.
*/
static void
packet_init_compression(void)
{
if (compression_buffer_ready == 1)
return;
}
void
{
#ifdef ALTPRIVSEP
/* shouldn't happen! */
if (packet_monitor)
fatal("INTERNAL ERROR: The monitor cannot compress.");
#endif /* ALTPRIVSEP */
if (packet_compression && !compat20)
fatal("Compression already enabled.");
packet_compression = 1;
}
/*
* 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
int number)
{
if (keylen < 20)
if (keylen > SSH_SESSION_KEY_LENGTH)
}
{
return (ssh1_keylen);
return (ssh1_keylen);
}
/* Start constructing a packet to send. */
void
{
int len;
}
/* Append payload. */
void
packet_put_char(int value)
{
}
void
{
}
void
{
}
void
packet_put_cstring(const char *str)
{
}
void
packet_put_ascii_cstring(const char *str)
{
}
void
{
}
#if 0
void
{
}
void
{
}
#endif
void
{
}
void
{
}
void
{
}
/*
* Finalizes and sends the packet. If the encryption key has been set,
* encrypts the packet before sending.
*/
static void
packet_send1(void)
{
/*
* If using packet compression, compress the payload of the outgoing
* packet.
*/
if (packet_compression) {
/* Skip padding. */
/* padding */
}
/* Compute packet length without padding (add checksum, remove padding). */
/* Insert padding. Initialized to zero in packet_start1() */
if (!send_context.plaintext) {
for (i = 0; i < padding; i++) {
if (i % 4 == 0)
rand = arc4random();
rand >>= 8;
}
}
/* Add check bytes. */
#ifdef PACKET_DEBUG
#endif
/* Append to output. */
#ifdef PACKET_DEBUG
#endif
/*
* 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.
*/
}
void
set_newkeys(int mode)
{
int encrypt;
cc = &send_context;
} else {
cc = &receive_context;
}
debug("newkeys: rekeying");
}
/* Deleting the keys does not gain extra security */
/* memset(enc->iv, 0, enc->block_size);
memset(enc->key, 0, enc->key_len); */
else
}
}
/*
* Finalize packet in SSH2 format (compress, mac, encrypt, enqueue)
*/
static void
packet_send2(void)
{
u_int packet_length = 0;
int block_size;
}
#ifdef PACKET_DEBUG
#endif
/* skip header, compress only payload */
}
/* sizeof (packet_len + pad_len + payload) */
/*
* calc size of padding, alloc space, get random data,
* minimum padding is 4 bytes
*/
if (padlen < 4)
padlen += block_size;
if (extra_pad) {
/* will wrap if extra_pad+padlen > 255 */
debug3("packet_send2: adding %d (len %d padlen %d extra_pad %d)",
extra_pad = 0;
}
/* random padding */
for (i = 0; i < padlen; i++) {
if (i % 4 == 0)
rand = arc4random();
rand >>= 8;
}
} else {
/* clear padding */
}
/* packet_length includes payload, padding and padding length field */
/* compute MAC over seqnr and packet(length fields, payload, padding) */
}
/* encrypt packet and append to output buffer. */
/* append unencrypted MAC */
#ifdef PACKET_DEBUG
#endif
/* increment sequence number for outgoing packets */
if (++send_seqnr == 0)
log("outgoing seqnr wraps around");
if (type == SSH2_MSG_NEWKEYS)
#ifdef ALTPRIVSEP
/* set_newkeys(MODE_OUT) in client, server, but not monitor */
if (!packet_is_server() && !packet_is_monitor())
#endif /* ALTPRIVSEP */
}
void
packet_send(void)
{
if (compat20)
packet_send2();
else
packet_send1();
}
/*
* 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
{
char buf[8192];
sizeof(fd_mask));
/* Since we are blocking, ensure that all written packets have been sent. */
/* Stay in the loop until we have received a complete packet. */
for (;;) {
/* Try to read a packet from the buffer. */
if (!compat20 && (
|| type == SSH_SMSG_FAILURE
|| type == SSH_CMSG_EOF
|| type == SSH_CMSG_EXIT_CONFIRMATION))
/* 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.
*/
sizeof(fd_mask));
/* Wait for some data to arrive. */
;
/* Read data from the socket. */
if (len == 0) {
}
if (len < 0)
/* Append it to the buffer. */
}
/* NOTREACHED */
}
int
packet_read(void)
{
return packet_read_seqnr(NULL);
}
/*
* 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
{
int type;
type = packet_read();
if (type != expected_type)
packet_disconnect("Protocol error: expected packet type %d, got %d",
}
/* 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.
*/
static int
packet_read_poll1(void)
{
/* Check if input size is less than minimum packet size. */
return SSH_MSG_NONE;
/* Get length of incoming packet. */
/* Check if the packet has been entirely received. */
return SSH_MSG_NONE;
/* The entire packet is in buffer. */
/* Consume packet length. */
/*
* Cryptographic attack detector for ssh
* (C)1998 CORE-SDI, Buenos Aires Argentina
* Ariel Futoransky(futo@core-sdi.com)
*/
if (!receive_context.plaintext &&
packet_disconnect("crc32 compensation attack: network attack detected");
/* Decrypt data to incoming_packet. */
#ifdef PACKET_DEBUG
#endif
/* Compute packet checksum. */
/* Skip padding. */
/* Test check bytes. */
packet_disconnect("packet_read_poll1: len %d != buffer_len %d.",
if (checksum != stored_checksum)
packet_disconnect("Corrupted check bytes on input.");
if (packet_compression) {
}
return type;
}
static int
{
static u_int packet_length = 0;
int maclen, block_size;
}
if (packet_length == 0) {
/*
* check if input size is less than the cipher block size,
* decrypt first block and extract length of incoming packet
*/
return SSH_MSG_NONE;
}
}
/* we have a partial packet of block_size bytes */
if (need % block_size != 0)
fatal("padding error: need %d block %d mod %d",
/*
* check if the entire packet has been received and
* decrypt into incoming_packet
*/
return SSH_MSG_NONE;
#ifdef PACKET_DEBUG
buffer_dump(&input);
#endif
/*
* compute MAC over seqnr and packet,
* increment sequence number for incoming packet
*/
packet_disconnect("Corrupted MAC on input.");
}
*seqnr_p = read_seqnr;
if (++read_seqnr == 0)
log("incoming seqnr wraps around");
/* get padlen */
if (padlen < 4)
/* skip packet size + padlen, discard padding */
}
/*
* get packet type, implies consume.
* return length of payload (without type field)
*/
#ifdef ALTPRIVSEP
if (type == SSH2_MSG_NEWKEYS)
/* set_newkeys(MODE_OUT) in client, server, but not monitor */
if (!packet_is_server() && !packet_is_monitor())
#else /* ALTPRIVSEP */
if (type == SSH2_MSG_NEWKEYS)
#endif /* ALTPRIVSEP */
#ifdef PACKET_DEBUG
#endif
/* reset for next packet */
packet_length = 0;
return type;
}
int
{
char *msg;
for (;;) {
if (compat20) {
switch (type) {
case SSH2_MSG_IGNORE:
break;
case SSH2_MSG_DEBUG:
break;
case SSH2_MSG_DISCONNECT:
reason = packet_get_int();
log("Received disconnect from %s: %u: %.400s",
break;
case SSH2_MSG_UNIMPLEMENTED:
seqnr = packet_get_int();
debug("Received SSH2_MSG_UNIMPLEMENTED for %u",
seqnr);
break;
default:
return type;
break;
}
} else {
type = packet_read_poll1();
switch (type) {
case SSH_MSG_IGNORE:
break;
case SSH_MSG_DEBUG:
break;
case SSH_MSG_DISCONNECT:
log("Received disconnect from %s: %.400s",
get_remote_ipaddr(), msg);
break;
default:
return type;
break;
}
}
}
}
int
packet_read_poll(void)
{
return packet_read_poll_seqnr(NULL);
}
/*
* Buffers the given amount of input characters. This is intended to be used
* together with packet_read_poll.
*/
void
{
}
/* Returns a character from the packet. */
packet_get_char(void)
{
char ch;
}
/* Returns an integer from the packet data. */
packet_get_int(void)
{
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
{
}
void
{
}
void *
{
if (length_ptr != NULL)
*length_ptr = bytes;
return buffer_ptr(&incoming_packet);
}
int
packet_remaining(void)
{
return buffer_len(&incoming_packet);
}
/*
* 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.
*/
void *
{
}
char *
{
return buffer_get_ascii_cstring(&incoming_packet);
}
u_char *
{
return buffer_get_utf8_cstring(&incoming_packet);
}
/*
* 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];
return;
#ifdef ALTPRIVSEP
/* shouldn't happen */
if (packet_monitor) {
return;
}
#endif /* ALTPRIVSEP */
if (compat20) {
packet_put_char(0); /* bool: always display */
packet_put_cstring("");
} else {
}
packet_send();
}
/*
* 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];
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.
*/
#ifdef ALTPRIVSEP
/*
* If we packet_disconnect() in the monitor the fatal cleanups will take
* care of the child. See main() in sshd.c. We don't send the packet
* disconnect message here because: a) the child might not be looking
* for it and b) because we don't really know if the child is compat20
* or not as we lost that information when packet_set_monitor() was
* called.
*/
if (packet_monitor)
goto close_stuff;
#endif /* ALTPRIVSEP */
/* Send the disconnect message to the other side, and wait for it to get sent. */
if (compat20) {
packet_put_cstring("");
} else {
}
packet_send();
#ifdef ALTPRIVSEP
#endif /* ALTPRIVSEP */
/* Stop listening for connections. */
/* Close the connection. */
packet_close();
/* Display the error locally and exit. */
}
/* Checks if there is any buffered output, and tries to write some of the output. */
void
packet_write_poll(void)
{
if (len > 0) {
if (len <= 0) {
return;
else
}
}
}
/*
* Calls packet_write_poll repeatedly until all pending output data has been
* written.
*/
void
packet_write_wait(void)
{
sizeof(fd_mask));
while (packet_have_data_to_write()) {
sizeof(fd_mask));
;
}
}
/* Returns true if there is buffered data to write to the connection. */
int
{
return buffer_len(&output) != 0;
}
/* Returns true if there is not too much data to write to the connection. */
int
{
if (interactive_mode)
else
}
/* Informs that the current session is interactive. Sets IP flags for that. */
void
{
static int called = 0;
#if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
int lowdelay = IPTOS_LOWDELAY;
int throughput = IPTOS_THROUGHPUT;
#endif
if (called)
return;
called = 1;
/* Record that we are in interactive mode. */
/* Only set socket options if using a socket. */
if (!packet_connection_is_on_socket())
return;
/*
* IPTOS_LOWDELAY and IPTOS_THROUGHPUT are IPv4 only
*/
if (interactive) {
/*
* Set IP options for an interactive connection. Use
* IPTOS_LOWDELAY and TCP_NODELAY.
*/
#if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
if (packet_connection_is_ipv4()) {
error("setsockopt IPTOS_LOWDELAY: %.100s",
}
#endif
}
#if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
else if (packet_connection_is_ipv4()) {
/*
* Set IP options for a non-interactive connection. Use
* IPTOS_THROUGHPUT.
*/
sizeof(throughput)) < 0)
}
#endif
}
/* Returns true if the current connection is interactive. */
int
packet_is_interactive(void)
{
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;
}
called = 1;
debug("packet_set_maxsize: setting to %d", s);
max_packet_size = s;
return s;
}
/* roundup current message to pad bytes */
void
{
}
/*
* 9.2. Ignored Data Message
*
* byte SSH_MSG_IGNORE
* string data
*
* All implementations MUST understand (and ignore) this message at any
* time (after receiving the protocol version). No implementation is
* required to send them. This message can be used as an additional
* protection measure against advanced traffic analysis techniques.
*/
void
packet_send_ignore(int nbytes)
{
int i;
#ifdef ALTPRIVSEP
/* shouldn't happen -- see packet_set_monitor() */
if (packet_monitor)
return;
#endif /* ALTPRIVSEP */
for (i = 0; i < nbytes; i++) {
if (i % 4 == 0)
rand = arc4random();
rand >>= 8;
}
}
#ifdef ALTPRIVSEP
void
packet_set_server(void)
{
packet_server = 1;
}
void
packet_set_no_monitor(void)
{
packet_server = 0;
}
int
packet_is_server(void)
{
return (packet_server);
}
void
packet_set_monitor(int pipe)
{
int dup_fd;
packet_server = 1;
packet_monitor = 1;
/*
* Awful hack follows.
*
* For SSHv1 the monitor does not process any SSHv1 packets, only
* ALTPRIVSEP packets. We take advantage of that here to keep changes
* to packet.c to a minimum by using the SSHv2 binary packet protocol,
* with cipher "none," mac "none" and compression alg "none," as the
* basis for the monitor protocol. And so to force packet.c to treat
* packets as SSHv2 we force compat20 == 1 here.
*
* For completeness and to help future developers catch this we also
* force compat20 == 1 in the monitor loop, in serverloop.c.
*/
compat20 = 1;
/*
* NOTE: Assumptions below!
*
* - lots of packet.c code assumes that (connection_in ==
* connection_out) -> connection is socket
*
* - packet_close() does not shutdown() the connection fildes
* if connection_in != connection_out
*
* - other code assumes the connection is a socket if
* connection_in == connection_out
*/
/*
* make sure that the monitor's child's socket is not shutdown(3SOCKET)
* when we packet_close()
*/
connection_out = -1;
/* now cleanup state related to ssh socket */
packet_close();
/* now make the monitor pipe look like the ssh connection */
}
int
packet_is_monitor(void)
{
return (packet_monitor);
}
#endif /* ALTPRIVSEP */