Initial revision

1 files changed, 762 insertions, 0 deletions

diff --git a/packet.c b/packet.c
new file mode 100644
index 00000000..7e74c73b
--- /dev/null
+++ b/packet.c
@@ -0,0 +1,762 @@
+/*
+
+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 1.1 1999/10/27 03:42:44 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 coontext 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;
+
+/* 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)
+{
+  assert((bytes % 8) == 0);
+  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;
+  
+  assert((bytes % 8) == 0);
+  
+  /*
+    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, int is_client)
+{
+  cipher_type = cipher;
+  if (cipher == SSH_CIPHER_RC4)
+    {
+      if (is_client)
+	{ /* In client: use first half for receiving, second for sending. */
+	  cipher_set_key(&receive_context, cipher, key, keylen / 2, 0);
+	  cipher_set_key(&send_context, cipher, key + keylen / 2, 
+			 keylen / 2, 1);
+	}
+      else
+	{ /* In server: use first half for sending, second for receiving. */
+	  cipher_set_key(&receive_context, cipher, key + keylen / 2, 
+			 keylen / 2, 0);
+	  cipher_set_key(&send_context, cipher, key, keylen / 2, 1);
+	}
+    }
+  else
+    {
+      /* 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);
+      buffer_consume(&outgoing_packet, 8); /* Skip padding. */
+      buffer_append(&compression_buffer, "\0\0\0\0\0\0\0\0", 8); /* padding */
+      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 remote host.");
+      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. */
+  assert(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)
+    fatal("%.900s", packet_get_string(NULL));
+
+  /* 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. */
+  fatal("Local: %.100s", buf);
+}
+
+/* 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;
+}