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authorDamien Miller <djm@mindrot.org>1999-10-27 13:42:43 +1000
committerDamien Miller <djm@mindrot.org>1999-10-27 13:42:43 +1000
commitd4a8b7e34dd619a4debf9a206c81db26d1402ea6 (patch)
treea47d770a2f790f40d18b0982d4e55fa7cfb1fa3b /packet.c
Initial revision
Diffstat (limited to 'packet.c')
-rw-r--r--packet.c762
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;
+}