1 files changed, 1287 insertions, 0 deletions

diff --git a/other/openssh-reverse/packet.c b/other/openssh-reverse/packet.c
new file mode 100644
index 0000000..56080cb
--- /dev/null
+++ b/other/openssh-reverse/packet.c
@@ -0,0 +1,1287 @@
+/*
+ *
+ * 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.
+ *
+ * SSH2 packet format added by Markus Friedl.
+ *
+ */
+
+#include "includes.h"
+RCSID("$OpenBSD: packet.c,v 1.33 2000/06/20 01:39:43 markus 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"
+#include "channels.h"
+
+#include "compat.h"
+#include "ssh2.h"
+
+#include <openssl/bn.h>
+#include <openssl/dh.h>
+#include <openssl/hmac.h>
+#include "buffer.h"
+#include "kex.h"
+#include "hmac.h"
+
+#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;
+
+/*
+ * 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;
+
+/* True if SSH2 packet format is used */
+int use_ssh2_packet_format = 0;
+
+/* Session key information for Encryption and MAC */
+Kex     *kex = NULL;
+
+void
+packet_set_kex(Kex *k)
+{
+        if( k->mac[MODE_IN ].key == NULL ||
+            k->enc[MODE_IN ].key == NULL ||
+            k->enc[MODE_IN ].iv  == NULL ||
+            k->mac[MODE_OUT].key == NULL ||
+            k->enc[MODE_OUT].key == NULL ||
+            k->enc[MODE_OUT].iv  == NULL)
+                fatal("bad KEX");
+        kex = k;
+}
+void
+clear_enc_keys(Enc *enc, int len)
+{
+        memset(enc->iv,  0, len);
+        memset(enc->key, 0, len);
+        xfree(enc->iv);
+        xfree(enc->key);
+        enc->iv = NULL;
+        enc->key = NULL;
+}
+void
+packet_set_ssh2_format(void)
+{
+        DBG(debug("use_ssh2_packet_format"));
+        use_ssh2_packet_format = 1;
+}
+
+/*
+ * 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);
+        cipher_set_key(&receive_context, SSH_CIPHER_NONE, (unsigned char *) "", 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);
+}
+
+/* Returns 1 if remote host is connected via socket, 0 if not. */
+
+int
+packet_connection_is_on_socket()
+{
+        struct sockaddr_storage from, to;
+        socklen_t fromlen, tolen;
+
+        /* filedescriptors in and out are the same, so it's a socket */
+        if (connection_in == connection_out)
+                return 1;
+        fromlen = sizeof(from);
+        memset(&from, 0, sizeof(from));
+        if (getpeername(connection_in, (struct sockaddr *)&from, &fromlen) < 0)
+                return 0;
+        tolen = sizeof(to);
+        memset(&to, 0, sizeof(to));
+        if (getpeername(connection_out, (struct sockaddr *)&to, &tolen) < 0)
+                return 0;
+        if (fromlen != tolen || memcmp(&from, &to, fromlen) != 0)
+                return 0;
+        if (from.ss_family != AF_INET && from.ss_family != AF_INET6)
+                return 0;
+        return 1;
+}
+
+/* returns 1 if connection is via ipv4 */
+
+int
+packet_connection_is_ipv4()
+{
+        struct sockaddr_storage to;
+        socklen_t tolen = sizeof(to);
+
+        memset(&to, 0, sizeof(to));
+        if (getsockname(connection_out, (struct sockaddr *)&to, &tolen) < 0)
+                return 0;
+        if (to.ss_family != AF_INET)
+                return 0;
+        return 1;
+}
+
+/* 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.
+ */
+
+/*** XXXXX todo: kex means re-init */
+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)
+         */
+
+        if (cc->type == SSH_CIPHER_NONE || compat20) {
+                i = DEATTACK_OK;
+        } else {
+                i = detect_attack(src, bytes, NULL);
+        }
+        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)
+{
+        if (keylen < 20)
+                fatal("keylen too small: %d", keylen);
+
+        /* All other ciphers use the same key in both directions for now. */
+        cipher_set_key(&receive_context, cipher, key, keylen);
+        cipher_set_key(&send_context, cipher, key, keylen);
+}
+
+/* Starts constructing a packet to send. */
+
+void
+packet_start1(int type)
+{
+        char buf[9];
+
+        buffer_clear(&outgoing_packet);
+        memset(buf, 0, 8);
+        buf[8] = type;
+        buffer_append(&outgoing_packet, buf, 9);
+}
+
+void
+packet_start2(int type)
+{
+        char buf[4+1+1];
+
+        buffer_clear(&outgoing_packet);
+        memset(buf, 0, sizeof buf);
+        /* buf[0..3] = payload_len; */
+        /* buf[4] =    pad_len; */
+        buf[5] = type & 0xff;
+        buffer_append(&outgoing_packet, buf, sizeof buf);
+}
+
+void
+packet_start(int type)
+{
+        DBG(debug("packet_start[%d]",type));
+        if (use_ssh2_packet_format)
+                packet_start2(type);
+        else
+                packet_start1(type);
+}
+
+/* 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);
+}
+void
+packet_put_cstring(const char *str)
+{
+        buffer_put_string(&outgoing_packet, str, strlen(str));
+}
+
+void
+packet_put_raw(const char *buf, unsigned int len)
+{
+        buffer_append(&outgoing_packet, buf, len);
+}
+
+
+/* Appends an arbitrary precision integer to packet data. */
+
+void
+packet_put_bignum(BIGNUM * value)
+{
+        buffer_put_bignum(&outgoing_packet, value);
+}
+void
+packet_put_bignum2(BIGNUM * value)
+{
+        buffer_put_bignum2(&outgoing_packet, value);
+}
+
+/*
+ * Finalizes and sends the packet.  If the encryption key has been set,
+ * encrypts the packet before sending.
+ */
+
+void
+packet_send1()
+{
+        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. Initialized to zero in packet_start1() */
+        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.
+         */
+}
+
+/*
+ * Finalize packet in SSH2 format (compress, mac, encrypt, enqueue)
+ */
+void
+packet_send2()
+{
+        unsigned char *macbuf = NULL;
+        char *cp;
+        unsigned int packet_length = 0;
+        unsigned int i, padlen, len;
+        u_int32_t rand = 0;
+        static unsigned int seqnr = 0;
+        int type;
+        Enc *enc   = NULL;
+        Mac *mac   = NULL;
+        Comp *comp = NULL;
+        int block_size;
+
+        if (kex != NULL) {
+                enc  = &kex->enc[MODE_OUT];
+                mac  = &kex->mac[MODE_OUT];
+                comp = &kex->comp[MODE_OUT];
+        }
+        block_size = enc ? enc->block_size : 8;
+
+        cp = buffer_ptr(&outgoing_packet);
+        type = cp[5] & 0xff;
+
+#ifdef PACKET_DEBUG
+        fprintf(stderr, "plain:     ");
+        buffer_dump(&outgoing_packet);
+#endif
+
+        if (comp && comp->enabled) {
+                len = buffer_len(&outgoing_packet);
+                /* skip header, compress only payload */
+                buffer_consume(&outgoing_packet, 5);
+                buffer_clear(&compression_buffer);
+                buffer_compress(&outgoing_packet, &compression_buffer);
+                buffer_clear(&outgoing_packet);
+                buffer_append(&outgoing_packet, "\0\0\0\0\0", 5);
+                buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
+                    buffer_len(&compression_buffer));
+                DBG(debug("compression: raw %d compressed %d", len,
+                    buffer_len(&outgoing_packet)));
+        }
+
+        /* sizeof (packet_len + pad_len + payload) */
+        len = buffer_len(&outgoing_packet);
+
+        /*
+         * calc size of padding, alloc space, get random data,
+         * minimum padding is 4 bytes
+         */
+        padlen = block_size - (len % block_size);
+        if (padlen < 4)
+                padlen += block_size;
+        buffer_append_space(&outgoing_packet, &cp, padlen);
+        if (enc && enc->type != SSH_CIPHER_NONE) {
+                /* random padding */
+                for (i = 0; i < padlen; i++) {
+                        if (i % 4 == 0)
+                                rand = arc4random();
+                        cp[i] = rand & 0xff;
+                        rand <<= 8;
+                }
+        } else {
+                /* clear padding */
+                memset(cp, 0, padlen);
+        }
+        /* packet_length includes payload, padding and padding length field */
+        packet_length = buffer_len(&outgoing_packet) - 4;
+        cp = buffer_ptr(&outgoing_packet);
+        PUT_32BIT(cp, packet_length);
+        cp[4] = padlen & 0xff;
+        DBG(debug("send: len %d (includes padlen %d)", packet_length+4, padlen));
+
+        /* compute MAC over seqnr and packet(length fields, payload, padding) */
+        if (mac && mac->enabled) {
+                macbuf = hmac( mac->md, seqnr,
+                    (unsigned char *) buffer_ptr(&outgoing_packet),
+                    buffer_len(&outgoing_packet),
+                    mac->key, mac->key_len
+                );
+                DBG(debug("done calc HMAC out #%d", seqnr));
+        }
+        /* encrypt packet and append to output buffer. */
+        buffer_append_space(&output, &cp, buffer_len(&outgoing_packet));
+        packet_encrypt(&send_context, cp, buffer_ptr(&outgoing_packet),
+            buffer_len(&outgoing_packet));
+        /* append unencrypted MAC */
+        if (mac && mac->enabled)
+                buffer_append(&output, (char *)macbuf, mac->mac_len);
+#ifdef PACKET_DEBUG
+        fprintf(stderr, "encrypted: ");
+        buffer_dump(&output);
+#endif
+        /* increment sequence number for outgoing packets */
+        if (++seqnr == 0)
+                log("outgoing seqnr wraps around");
+        buffer_clear(&outgoing_packet);
+
+        if (type == SSH2_MSG_NEWKEYS) {
+                if (kex==NULL || mac==NULL || enc==NULL || comp==NULL)
+                        fatal("packet_send2: no KEX");
+                if (mac->md != NULL)
+                        mac->enabled = 1;
+                DBG(debug("cipher_set_key_iv send_context"));
+                cipher_set_key_iv(&send_context, enc->type,
+                    enc->key, enc->key_len,
+                    enc->iv, enc->iv_len);
+                clear_enc_keys(enc, kex->we_need);
+                if (comp->type != 0 && comp->enabled == 0) {
+                        comp->enabled = 1;
+                        if (! packet_compression)
+                                packet_start_compression(6);
+                }
+        }
+}
+
+void
+packet_send()
+{
+        if (use_ssh2_packet_format)
+                packet_send2();
+        else
+                packet_send1();
+        DBG(debug("packet_send done"));
+}
+
+/*
+ * 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];
+        DBG(debug("packet_read()"));
+
+        /* 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 (!use_ssh2_packet_format && (
+                    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) {
+                        log("Connection closed by %.200s", get_remote_ipaddr());
+                        fatal_cleanup();
+                }
+                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_poll1(int *payload_len_ptr)
+{
+        unsigned int len, padded_len;
+        unsigned char *ucp;
+        char buf[8], *cp;
+        unsigned int checksum, stored_checksum;
+
+        /* 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);
+
+        /* Return type. */
+        return (unsigned char) buf[0];
+}
+
+int
+packet_read_poll2(int *payload_len_ptr)
+{
+        unsigned int padlen, need;
+        unsigned char buf[8], *macbuf;
+        unsigned char *ucp;
+        char *cp;
+        static unsigned int packet_length = 0;
+        static unsigned int seqnr = 0;
+        int type;
+        int maclen, block_size;
+        Enc *enc   = NULL;
+        Mac *mac   = NULL;
+        Comp *comp = NULL;
+
+        if (kex != NULL) {
+                enc  = &kex->enc[MODE_IN];
+                mac  = &kex->mac[MODE_IN];
+                comp = &kex->comp[MODE_IN];
+        }
+        maclen = mac && mac->enabled ? mac->mac_len : 0;
+        block_size = enc ? enc->block_size : 8;
+
+        if (packet_length == 0) {
+                /*
+                 * check if input size is less than the cipher block size,
+                 * decrypt first block and extract length of incoming packet
+                 */
+                if (buffer_len(&input) < block_size)
+                        return SSH_MSG_NONE;
+                buffer_clear(&incoming_packet);
+                buffer_append_space(&incoming_packet, &cp, block_size);
+                packet_decrypt(&receive_context, cp, buffer_ptr(&input),
+                    block_size);
+                ucp = (unsigned char *) buffer_ptr(&incoming_packet);
+                packet_length = GET_32BIT(ucp);
+                if (packet_length < 1 + 4 || packet_length > 256 * 1024) {
+                        buffer_dump(&incoming_packet);
+                        packet_disconnect("Bad packet length %d.", packet_length);
+                }
+                DBG(debug("input: packet len %d", packet_length+4));
+                buffer_consume(&input, block_size);
+        }
+        /* we have a partial packet of block_size bytes */
+        need = 4 + packet_length - block_size;
+        DBG(debug("partial packet %d, need %d, maclen %d", block_size,
+            need, maclen));
+        if (need % block_size != 0)
+                fatal("padding error: need %d block %d mod %d",
+                    need, block_size, need % block_size);
+        /*
+         * check if the entire packet has been received and
+         * decrypt into incoming_packet
+         */
+        if (buffer_len(&input) < need + maclen)
+                return SSH_MSG_NONE;
+#ifdef PACKET_DEBUG
+        fprintf(stderr, "read_poll enc/full: ");
+        buffer_dump(&input);
+#endif
+        buffer_append_space(&incoming_packet, &cp, need);
+        packet_decrypt(&receive_context, cp, buffer_ptr(&input), need);
+        buffer_consume(&input, need);
+        /*
+         * compute MAC over seqnr and packet,
+         * increment sequence number for incoming packet
+         */
+        if (mac && mac->enabled) {
+                macbuf = hmac( mac->md, seqnr,
+                    (unsigned char *) buffer_ptr(&incoming_packet),
+                    buffer_len(&incoming_packet),
+                    mac->key, mac->key_len
+                );
+                if (memcmp(macbuf, buffer_ptr(&input), mac->mac_len) != 0)
+                        packet_disconnect("Corrupted HMAC on input.");
+                DBG(debug("HMAC #%d ok", seqnr));
+                buffer_consume(&input, mac->mac_len);
+        }
+        if (++seqnr == 0)
+                log("incoming seqnr wraps around");
+
+        /* get padlen */
+        cp = buffer_ptr(&incoming_packet) + 4;
+        padlen = *cp & 0xff;
+        DBG(debug("input: padlen %d", padlen));
+        if (padlen < 4)
+                packet_disconnect("Corrupted padlen %d on input.", padlen);
+
+        /* skip packet size + padlen, discard padding */
+        buffer_consume(&incoming_packet, 4 + 1);
+        buffer_consume_end(&incoming_packet, padlen);
+
+        DBG(debug("input: len before de-compress %d", buffer_len(&incoming_packet)));
+        if (comp && comp->enabled) {
+                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));
+                DBG(debug("input: len after de-compress %d", buffer_len(&incoming_packet)));
+        }
+        /*
+         * get packet type, implies consume.
+         * return length of payload (without type field)
+         */
+        buffer_get(&incoming_packet, (char *)&buf[0], 1);
+        *payload_len_ptr = buffer_len(&incoming_packet);
+
+        /* reset for next packet */
+        packet_length = 0;
+
+        /* extract packet type */
+        type = (unsigned char)buf[0];
+
+        if (type == SSH2_MSG_NEWKEYS) {
+                if (kex==NULL || mac==NULL || enc==NULL || comp==NULL)
+                        fatal("packet_read_poll2: no KEX");
+                if (mac->md != NULL)
+                        mac->enabled = 1;
+                DBG(debug("cipher_set_key_iv receive_context"));
+                cipher_set_key_iv(&receive_context, enc->type,
+                    enc->key, enc->key_len,
+                    enc->iv, enc->iv_len);
+                clear_enc_keys(enc, kex->we_need);
+                if (comp->type != 0 && comp->enabled == 0) {
+                        comp->enabled = 1;
+                        if (! packet_compression)
+                                packet_start_compression(6);
+                }
+        }
+
+#ifdef PACKET_DEBUG
+        fprintf(stderr, "read/plain[%d]:\r\n",type);
+        buffer_dump(&incoming_packet);
+#endif
+        return (unsigned char)type;
+}
+
+int
+packet_read_poll(int *payload_len_ptr)
+{
+        char *msg;
+        for (;;) {
+                int type = use_ssh2_packet_format ?
+                    packet_read_poll2(payload_len_ptr):
+                    packet_read_poll1(payload_len_ptr);
+
+                if(compat20) {
+                        int reason;
+                        if (type != 0)
+                                DBG(debug("received packet type %d", type));
+                        switch(type) {
+                        case SSH2_MSG_IGNORE:
+                                break;
+                        case SSH2_MSG_DEBUG:
+                                packet_get_char();
+                                msg = packet_get_string(NULL);
+                                debug("Remote: %.900s", msg);
+                                xfree(msg);
+                                msg = packet_get_string(NULL);
+                                xfree(msg);
+                                break;
+                        case SSH2_MSG_DISCONNECT:
+                                reason = packet_get_int();
+                                msg = packet_get_string(NULL);
+                                log("Received disconnect: %d: %.900s", reason, msg);
+                                xfree(msg);
+                                fatal_cleanup();
+                                break;
+                        default:
+                                return type;
+                                break;
+                        }       
+                } else {
+                        switch(type) {
+                        case SSH_MSG_IGNORE:
+                                break;
+                        case SSH_MSG_DEBUG:
+                                msg = packet_get_string(NULL);
+                                debug("Remote: %.900s", msg);
+                                xfree(msg);
+                                break;
+                        case SSH_MSG_DISCONNECT:
+                                msg = packet_get_string(NULL);
+                                log("Received disconnect: %.900s", msg);
+                                fatal_cleanup();
+                                xfree(msg);
+                                break;
+                        default:
+                                if (type != 0)
+                                        DBG(debug("received packet type %d", type));
+                                return type;
+                                break;
+                        }       
+                }
+        }
+}
+
+/*
+ * 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);
+}
+
+void
+packet_get_bignum2(BIGNUM * value, int *length_ptr)
+{
+        *length_ptr = buffer_get_bignum2(&incoming_packet, value);
+}
+
+char *
+packet_get_raw(int *length_ptr)
+{
+        int bytes = buffer_len(&incoming_packet);
+        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.
+ */
+
+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);
+
+        if (compat20) {
+                packet_start(SSH2_MSG_DEBUG);
+                packet_put_char(0);     /* bool: always display */
+                packet_put_cstring(buf);
+                packet_put_cstring("");
+        } else {
+                packet_start(SSH_MSG_DEBUG);
+                packet_put_cstring(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. */
+        if (compat20) {
+                packet_start(SSH2_MSG_DISCONNECT);
+                packet_put_int(SSH2_DISCONNECT_PROTOCOL_ERROR);
+                packet_put_cstring(buf);
+                packet_put_cstring("");
+        } else {
+                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.  */
+        if (!packet_connection_is_on_socket())
+                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));
+        }
+        /*
+         * IPTOS_LOWDELAY, TCP_NODELAY and IPTOS_THROUGHPUT are IPv4 only
+         */
+        if (!packet_connection_is_ipv4())
+                return;
+        if (interactive) {
+                /*
+                 * Set IP options for an interactive connection.  Use
+                 * IPTOS_LOWDELAY and TCP_NODELAY.
+                 */
+#if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
+                int lowdelay = IPTOS_LOWDELAY;
+                if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &lowdelay,
+                    sizeof(lowdelay)) < 0)
+                        error("setsockopt IPTOS_LOWDELAY: %.100s", strerror(errno));
+#endif
+                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.
+                 */
+#if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
+                int throughput = IPTOS_THROUGHPUT;
+                if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &throughput,
+                    sizeof(throughput)) < 0)
+                        error("setsockopt IPTOS_THROUGHPUT: %.100s", strerror(errno));
+#endif
+        }
+}
+
+/* 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;
+}