/src/openssh/packet.c

Source (jump to first uncovered line)
/* $OpenBSD: packet.c,v 1.318 2025/02/18 08:02:12 djm Exp $ */
/*
 * 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
 *    documentation and/or other materials provided with the distribution.
 *
 * 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.
 */

#include "includes.h"

#include <sys/types.h>
#include "openbsd-compat/sys-queue.h"
#include <sys/socket.h>
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
#endif

#include <netinet/in.h>
#include <netinet/ip.h>
#include <arpa/inet.h>

#include <errno.h>
#include <netdb.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#ifdef HAVE_POLL_H
#include <poll.h>
#endif
#include <signal.h>
#include <time.h>

/*
 * Explicitly include OpenSSL before zlib as some versions of OpenSSL have
 * "free_func" in their headers, which zlib typedefs.
 */
#ifdef WITH_OPENSSL
# include <openssl/bn.h>
# include <openssl/evp.h>
# ifdef OPENSSL_HAS_ECC
#  include <openssl/ec.h>
# endif
#endif

#ifdef WITH_ZLIB
#include <zlib.h>
#endif

#include "xmalloc.h"
#include "compat.h"
#include "ssh2.h"
#include "cipher.h"
#include "sshkey.h"
#include "kex.h"
#include "digest.h"
#include "mac.h"
#include "log.h"
#include "canohost.h"
#include "misc.h"
#include "channels.h"
#include "ssh.h"
#include "packet.h"
#include "ssherr.h"
#include "sshbuf.h"

#ifdef PACKET_DEBUG
#define DBG(x) x
#else
#define DBG(x)
#endif

#define PACKET_MAX_SIZE (256 * 1024)

struct packet_state {
  u_int32_t seqnr;
  u_int32_t packets;
  u_int64_t blocks;
  u_int64_t bytes;
};

struct packet {
  TAILQ_ENTRY(packet) next;
  u_char type;
  struct sshbuf *payload;
};

struct session_state {
  /*
   * 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.
   */
  int connection_in;
  int connection_out;

  /* Protocol flags for the remote side. */
  u_int remote_protocol_flags;

  /* Encryption context for receiving data.  Only used for decryption. */
  struct sshcipher_ctx *receive_context;

  /* Encryption context for sending data.  Only used for encryption. */
  struct sshcipher_ctx *send_context;

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

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

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

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

  /* Scratch buffer for packet compression/decompression. */
  struct sshbuf *compression_buffer;

#ifdef WITH_ZLIB
  /* Incoming/outgoing compression dictionaries */
  z_stream compression_in_stream;
  z_stream compression_out_stream;
#endif
  int compression_in_started;
  int compression_out_started;
  int compression_in_failures;
  int compression_out_failures;

  /* default maximum packet size */
  u_int max_packet_size;

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

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

  /* Set to true if we are the server side. */
  int server_side;

  /* Set to true if we are authenticated. */
  int after_authentication;

  int keep_alive_timeouts;

  /* The maximum time that we will wait to send or receive a packet */
  int packet_timeout_ms;

  /* Session key information for Encryption and MAC */
  struct newkeys *newkeys[MODE_MAX];
  struct packet_state p_read, p_send;

  /* Volume-based rekeying */
  u_int64_t max_blocks_in, max_blocks_out, rekey_limit;

  /* Time-based rekeying */
  u_int32_t rekey_interval; /* how often in seconds */
  time_t rekey_time;  /* time of last rekeying */

  /* roundup current message to extra_pad bytes */
  u_char extra_pad;

  /* XXX discard incoming data after MAC error */
  u_int packet_discard;
  size_t packet_discard_mac_already;
  struct sshmac *packet_discard_mac;

  /* Used in packet_read_poll2() */
  u_int packlen;

  /* Used in packet_send2 */
  int rekeying;

  /* Used in ssh_packet_send_mux() */
  int mux;

  /* Used in packet_set_interactive */
  int set_interactive_called;

  /* Used in packet_set_maxsize */
  int set_maxsize_called;

  /* One-off warning about weak ciphers */
  int cipher_warning_done;

  /* Hook for fuzzing inbound packets */
  ssh_packet_hook_fn *hook_in;
  void *hook_in_ctx;

  TAILQ_HEAD(, packet) outgoing;
};

struct ssh *
ssh_alloc_session_state(void)
{
  struct ssh *ssh = NULL;
  struct session_state *state = NULL;

  if ((ssh = calloc(1, sizeof(*ssh))) == NULL ||
      (state = calloc(1, sizeof(*state))) == NULL ||
      (ssh->kex = kex_new()) == NULL ||
      (state->input = sshbuf_new()) == NULL ||
      (state->output = sshbuf_new()) == NULL ||
      (state->outgoing_packet = sshbuf_new()) == NULL ||
      (state->incoming_packet = sshbuf_new()) == NULL)
    goto fail;
  TAILQ_INIT(&state->outgoing);
  TAILQ_INIT(&ssh->private_keys);
  TAILQ_INIT(&ssh->public_keys);
  state->connection_in = -1;
  state->connection_out = -1;
  state->max_packet_size = 32768;
  state->packet_timeout_ms = -1;
  state->p_send.packets = state->p_read.packets = 0;
  state->initialized = 1;
  /*
   * ssh_packet_send2() needs to queue packets until
   * we've done the initial key exchange.
   */
  state->rekeying = 1;
  ssh->state = state;
  return ssh;
 fail:
  if (ssh) {
    kex_free(ssh->kex);
    free(ssh);
  }
  if (state) {
    sshbuf_free(state->input);
    sshbuf_free(state->output);
    sshbuf_free(state->incoming_packet);
    sshbuf_free(state->outgoing_packet);
    free(state);
  }
  return NULL;
}

void
ssh_packet_set_input_hook(struct ssh *ssh, ssh_packet_hook_fn *hook, void *ctx)
{
  ssh->state->hook_in = hook;
  ssh->state->hook_in_ctx = ctx;
}

/* Returns nonzero if rekeying is in progress */
int
ssh_packet_is_rekeying(struct ssh *ssh)
{
  return ssh->state->rekeying ||
      (ssh->kex != NULL && ssh->kex->done == 0);
}

/*
 * Sets the descriptors used for communication.
 */
struct ssh *
ssh_packet_set_connection(struct ssh *ssh, int fd_in, int fd_out)
{
  struct session_state *state;
  const struct sshcipher *none = cipher_by_name("none");
  int r;

  if (none == NULL) {
    error_f("cannot load cipher 'none'");
    return NULL;
  }
  if (ssh == NULL)
    ssh = ssh_alloc_session_state();
  if (ssh == NULL) {
    error_f("could not allocate state");
    return NULL;
  }
  state = ssh->state;
  state->connection_in = fd_in;
  state->connection_out = fd_out;
  if ((r = cipher_init(&state->send_context, none,
      (const u_char *)"", 0, NULL, 0, CIPHER_ENCRYPT)) != 0 ||
      (r = cipher_init(&state->receive_context, none,
      (const u_char *)"", 0, NULL, 0, CIPHER_DECRYPT)) != 0) {
    error_fr(r, "cipher_init failed");
    free(ssh); /* XXX need ssh_free_session_state? */
    return NULL;
  }
  state->newkeys[MODE_IN] = state->newkeys[MODE_OUT] = NULL;
  /*
   * Cache the IP address of the remote connection for use in error
   * messages that might be generated after the connection has closed.
   */
  (void)ssh_remote_ipaddr(ssh);
  return ssh;
}

void
ssh_packet_set_timeout(struct ssh *ssh, int timeout, int count)
{
  struct session_state *state = ssh->state;

  if (timeout <= 0 || count <= 0) {
    state->packet_timeout_ms = -1;
    return;
  }
  if ((INT_MAX / 1000) / count < timeout)
    state->packet_timeout_ms = INT_MAX;
  else
    state->packet_timeout_ms = timeout * count * 1000;
}

void
ssh_packet_set_mux(struct ssh *ssh)
{
  ssh->state->mux = 1;
  ssh->state->rekeying = 0;
  kex_free(ssh->kex);
  ssh->kex = NULL;
}

int
ssh_packet_get_mux(struct ssh *ssh)
{
  return ssh->state->mux;
}

int
ssh_packet_set_log_preamble(struct ssh *ssh, const char *fmt, ...)
{
  va_list args;
  int r;

  free(ssh->log_preamble);
  if (fmt == NULL)
    ssh->log_preamble = NULL;
  else {
    va_start(args, fmt);
    r = vasprintf(&ssh->log_preamble, fmt, args);
    va_end(args);
    if (r < 0 || ssh->log_preamble == NULL)
      return SSH_ERR_ALLOC_FAIL;
  }
  return 0;
}

int
ssh_packet_stop_discard(struct ssh *ssh)
{
  struct session_state *state = ssh->state;
  int r;

  if (state->packet_discard_mac) {
    char buf[1024];
    size_t dlen = PACKET_MAX_SIZE;

    if (dlen > state->packet_discard_mac_already)
      dlen -= state->packet_discard_mac_already;
    memset(buf, 'a', sizeof(buf));
    while (sshbuf_len(state->incoming_packet) < dlen)
      if ((r = sshbuf_put(state->incoming_packet, buf,
          sizeof(buf))) != 0)
        return r;
    (void) mac_compute(state->packet_discard_mac,
        state->p_read.seqnr,
        sshbuf_ptr(state->incoming_packet), dlen,
        NULL, 0);
  }
  logit("Finished discarding for %.200s port %d",
      ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
  return SSH_ERR_MAC_INVALID;
}

static int
ssh_packet_start_discard(struct ssh *ssh, struct sshenc *enc,
    struct sshmac *mac, size_t mac_already, u_int discard)
{
  struct session_state *state = ssh->state;
  int r;

  if (enc == NULL || !cipher_is_cbc(enc->cipher) || (mac && mac->etm)) {
    if ((r = sshpkt_disconnect(ssh, "Packet corrupt")) != 0)
      return r;
    return SSH_ERR_MAC_INVALID;
  }
  /*
   * Record number of bytes over which the mac has already
   * been computed in order to minimize timing attacks.
   */
  if (mac && mac->enabled) {
    state->packet_discard_mac = mac;
    state->packet_discard_mac_already = mac_already;
  }
  if (sshbuf_len(state->input) >= discard)
    return ssh_packet_stop_discard(ssh);
  state->packet_discard = discard - sshbuf_len(state->input);
  return 0;
}

/* Returns 1 if remote host is connected via socket, 0 if not. */

int
ssh_packet_connection_is_on_socket(struct ssh *ssh)
{
  struct session_state *state;
  struct sockaddr_storage from, to;
  socklen_t fromlen, tolen;

  if (ssh == NULL || ssh->state == NULL)
    return 0;

  state = ssh->state;
  if (state->connection_in == -1 || state->connection_out == -1)
    return 0;
  /* filedescriptors in and out are the same, so it's a socket */
  if (state->connection_in == state->connection_out)
    return 1;
  fromlen = sizeof(from);
  memset(&from, 0, sizeof(from));
  if (getpeername(state->connection_in, (struct sockaddr *)&from,
      &fromlen) == -1)
    return 0;
  tolen = sizeof(to);
  memset(&to, 0, sizeof(to));
  if (getpeername(state->connection_out, (struct sockaddr *)&to,
      &tolen) == -1)
    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;
}

void
ssh_packet_get_bytes(struct ssh *ssh, u_int64_t *ibytes, u_int64_t *obytes)
{
  if (ibytes)
    *ibytes = ssh->state->p_read.bytes;
  if (obytes)
    *obytes = ssh->state->p_send.bytes;
}

int
ssh_packet_connection_af(struct ssh *ssh)
{
  return get_sock_af(ssh->state->connection_out);
}

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

void
ssh_packet_set_nonblocking(struct ssh *ssh)
{
  /* Set the socket into non-blocking mode. */
  set_nonblock(ssh->state->connection_in);

  if (ssh->state->connection_out != ssh->state->connection_in)
    set_nonblock(ssh->state->connection_out);
}

/* Returns the socket used for reading. */

int
ssh_packet_get_connection_in(struct ssh *ssh)
{
  return ssh->state->connection_in;
}

/* Returns the descriptor used for writing. */

int
ssh_packet_get_connection_out(struct ssh *ssh)
{
  return ssh->state->connection_out;
}

/*
 * Returns the IP-address of the remote host as a string.  The returned
 * string must not be freed.
 */

const char *
ssh_remote_ipaddr(struct ssh *ssh)
{
  int sock;

  /* Check whether we have cached the ipaddr. */
  if (ssh->remote_ipaddr == NULL) {
    if (ssh_packet_connection_is_on_socket(ssh)) {
      sock = ssh->state->connection_in;
      ssh->remote_ipaddr = get_peer_ipaddr(sock);
      ssh->remote_port = get_peer_port(sock);
      ssh->local_ipaddr = get_local_ipaddr(sock);
      ssh->local_port = get_local_port(sock);
    } else {
      ssh->remote_ipaddr = xstrdup("UNKNOWN");
      ssh->remote_port = 65535;
      ssh->local_ipaddr = xstrdup("UNKNOWN");
      ssh->local_port = 65535;
    }
  }
  return ssh->remote_ipaddr;
}

/*
 * Returns the remote DNS hostname as a string. The returned string must not
 * be freed. NB. this will usually trigger a DNS query. Return value is on
 * heap and no caching is performed.
 * This function does additional checks on the hostname to mitigate some
 * attacks based on conflation of hostnames and addresses and will
 * fall back to returning an address on error.
 */

char *
ssh_remote_hostname(struct ssh *ssh)
{
  struct sockaddr_storage from;
  socklen_t fromlen;
  struct addrinfo hints, *ai, *aitop;
  char name[NI_MAXHOST], ntop2[NI_MAXHOST];
  const char *ntop = ssh_remote_ipaddr(ssh);

  /* Get IP address of client. */
  fromlen = sizeof(from);
  memset(&from, 0, sizeof(from));
  if (getpeername(ssh_packet_get_connection_in(ssh),
      (struct sockaddr *)&from, &fromlen) == -1) {
    debug_f("getpeername failed: %.100s", strerror(errno));
    return xstrdup(ntop);
  }

  ipv64_normalise_mapped(&from, &fromlen);
  if (from.ss_family == AF_INET6)
    fromlen = sizeof(struct sockaddr_in6);

  debug3("trying to reverse map address %.100s.", ntop);
  /* Map the IP address to a host name. */
  if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
      NULL, 0, NI_NAMEREQD) != 0) {
    /* Host name not found.  Use ip address. */
    return xstrdup(ntop);
  }

  /*
   * if reverse lookup result looks like a numeric hostname,
   * someone is trying to trick us by PTR record like following:
   *  1.1.1.10.in-addr.arpa.  IN PTR  2.3.4.5
   */
  memset(&hints, 0, sizeof(hints));
  hints.ai_socktype = SOCK_DGRAM; /*dummy*/
  hints.ai_flags = AI_NUMERICHOST;
  if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
    logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
        name, ntop);
    freeaddrinfo(ai);
    return xstrdup(ntop);
  }

  /* Names are stored in lowercase. */
  lowercase(name);

  /*
   * Map it back to an IP address and check that the given
   * address actually is an address of this host.  This is
   * necessary because anyone with access to a name server can
   * define arbitrary names for an IP address. Mapping from
   * name to IP address can be trusted better (but can still be
   * fooled if the intruder has access to the name server of
   * the domain).
   */
  memset(&hints, 0, sizeof(hints));
  hints.ai_family = from.ss_family;
  hints.ai_socktype = SOCK_STREAM;
  if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
    logit("reverse mapping checking getaddrinfo for %.700s "
        "[%s] failed.", name, ntop);
    return xstrdup(ntop);
  }
  /* Look for the address from the list of addresses. */
  for (ai = aitop; ai; ai = ai->ai_next) {
    if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
        sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
        (strcmp(ntop, ntop2) == 0))
        break;
  }
  freeaddrinfo(aitop);
  /* If we reached the end of the list, the address was not there. */
  if (ai == NULL) {
    /* Address not found for the host name. */
    logit("Address %.100s maps to %.600s, but this does not "
        "map back to the address.", ntop, name);
    return xstrdup(ntop);
  }
  return xstrdup(name);
}

/* Returns the port number of the remote host. */

int
ssh_remote_port(struct ssh *ssh)
{
  (void)ssh_remote_ipaddr(ssh); /* Will lookup and cache. */
  return ssh->remote_port;
}

/*
 * Returns the IP-address of the local host as a string.  The returned
 * string must not be freed.
 */

const char *
ssh_local_ipaddr(struct ssh *ssh)
{
  (void)ssh_remote_ipaddr(ssh); /* Will lookup and cache. */
  return ssh->local_ipaddr;
}

/* Returns the port number of the local host. */

int
ssh_local_port(struct ssh *ssh)
{
  (void)ssh_remote_ipaddr(ssh); /* Will lookup and cache. */
  return ssh->local_port;
}

/* Returns the routing domain of the input socket, or NULL if unavailable */
const char *
ssh_packet_rdomain_in(struct ssh *ssh)
{
  if (ssh->rdomain_in != NULL)
    return ssh->rdomain_in;
  if (!ssh_packet_connection_is_on_socket(ssh))
    return NULL;
  ssh->rdomain_in = get_rdomain(ssh->state->connection_in);
  return ssh->rdomain_in;
}

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

static void
ssh_packet_close_internal(struct ssh *ssh, int do_close)
{
  struct session_state *state = ssh->state;
  u_int mode;

  if (!state->initialized)
    return;
  state->initialized = 0;
  if (do_close) {
    if (state->connection_in == state->connection_out) {
      close(state->connection_out);
    } else {
      close(state->connection_in);
      close(state->connection_out);
    }
  }
  sshbuf_free(state->input);
  sshbuf_free(state->output);
  sshbuf_free(state->outgoing_packet);
  sshbuf_free(state->incoming_packet);
  for (mode = 0; mode < MODE_MAX; mode++) {
    kex_free_newkeys(state->newkeys[mode]); /* current keys */
    state->newkeys[mode] = NULL;
    ssh_clear_newkeys(ssh, mode);   /* next keys */
  }
#ifdef WITH_ZLIB
  /* compression state is in shared mem, so we can only release it once */
  if (do_close && state->compression_buffer) {
    sshbuf_free(state->compression_buffer);
    if (state->compression_out_started) {
      z_streamp stream = &state->compression_out_stream;
      debug("compress outgoing: "
          "raw data %llu, compressed %llu, factor %.2f",
        (unsigned long long)stream->total_in,
        (unsigned long long)stream->total_out,
        stream->total_in == 0 ? 0.0 :
        (double) stream->total_out / stream->total_in);
      if (state->compression_out_failures == 0)
        deflateEnd(stream);
    }
    if (state->compression_in_started) {
      z_streamp stream = &state->compression_in_stream;
      debug("compress incoming: "
          "raw data %llu, compressed %llu, factor %.2f",
          (unsigned long long)stream->total_out,
          (unsigned long long)stream->total_in,
          stream->total_out == 0 ? 0.0 :
          (double) stream->total_in / stream->total_out);
      if (state->compression_in_failures == 0)
        inflateEnd(stream);
    }
  }
#endif  /* WITH_ZLIB */
  cipher_free(state->send_context);
  cipher_free(state->receive_context);
  state->send_context = state->receive_context = NULL;
  if (do_close) {
    free(ssh->local_ipaddr);
    ssh->local_ipaddr = NULL;
    free(ssh->remote_ipaddr);
    ssh->remote_ipaddr = NULL;
    free(ssh->state);
    ssh->state = NULL;
    kex_free(ssh->kex);
    ssh->kex = NULL;
  }
}

void
ssh_packet_close(struct ssh *ssh)
{
  ssh_packet_close_internal(ssh, 1);
}

void
ssh_packet_clear_keys(struct ssh *ssh)
{
  ssh_packet_close_internal(ssh, 0);
}

/* Sets remote side protocol flags. */

void
ssh_packet_set_protocol_flags(struct ssh *ssh, u_int protocol_flags)
{
  ssh->state->remote_protocol_flags = protocol_flags;
}

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

u_int
ssh_packet_get_protocol_flags(struct ssh *ssh)
{
  return ssh->state->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 int
ssh_packet_init_compression(struct ssh *ssh)
{
  if (!ssh->state->compression_buffer &&
      ((ssh->state->compression_buffer = sshbuf_new()) == NULL))
    return SSH_ERR_ALLOC_FAIL;
  return 0;
}

#ifdef WITH_ZLIB
static int
start_compression_out(struct ssh *ssh, int level)
{
  if (level < 1 || level > 9)
    return SSH_ERR_INVALID_ARGUMENT;
  debug("Enabling compression at level %d.", level);
  if (ssh->state->compression_out_started == 1)
    deflateEnd(&ssh->state->compression_out_stream);
  switch (deflateInit(&ssh->state->compression_out_stream, level)) {
  case Z_OK:
    ssh->state->compression_out_started = 1;
    break;
  case Z_MEM_ERROR:
    return SSH_ERR_ALLOC_FAIL;
  default:
    return SSH_ERR_INTERNAL_ERROR;
  }
  return 0;
}

static int
start_compression_in(struct ssh *ssh)
{
  if (ssh->state->compression_in_started == 1)
    inflateEnd(&ssh->state->compression_in_stream);
  switch (inflateInit(&ssh->state->compression_in_stream)) {
  case Z_OK:
    ssh->state->compression_in_started = 1;
    break;
  case Z_MEM_ERROR:
    return SSH_ERR_ALLOC_FAIL;
  default:
    return SSH_ERR_INTERNAL_ERROR;
  }
  return 0;
}

/* XXX remove need for separate compression buffer */
static int
compress_buffer(struct ssh *ssh, struct sshbuf *in, struct sshbuf *out)
{
  u_char buf[4096];
  int r, status;

  if (ssh->state->compression_out_started != 1)
    return SSH_ERR_INTERNAL_ERROR;

  /* This case is not handled below. */
  if (sshbuf_len(in) == 0)
    return 0;

  /* Input is the contents of the input buffer. */
  if ((ssh->state->compression_out_stream.next_in =
      sshbuf_mutable_ptr(in)) == NULL)
    return SSH_ERR_INTERNAL_ERROR;
  ssh->state->compression_out_stream.avail_in = sshbuf_len(in);

  /* Loop compressing until deflate() returns with avail_out != 0. */
  do {
    /* Set up fixed-size output buffer. */
    ssh->state->compression_out_stream.next_out = buf;
    ssh->state->compression_out_stream.avail_out = sizeof(buf);

    /* Compress as much data into the buffer as possible. */
    status = deflate(&ssh->state->compression_out_stream,
        Z_PARTIAL_FLUSH);
    switch (status) {
    case Z_MEM_ERROR:
      return SSH_ERR_ALLOC_FAIL;
    case Z_OK:
      /* Append compressed data to output_buffer. */
      if ((r = sshbuf_put(out, buf, sizeof(buf) -
          ssh->state->compression_out_stream.avail_out)) != 0)
        return r;
      break;
    case Z_STREAM_ERROR:
    default:
      ssh->state->compression_out_failures++;
      return SSH_ERR_INVALID_FORMAT;
    }
  } while (ssh->state->compression_out_stream.avail_out == 0);
  return 0;
}

static int
uncompress_buffer(struct ssh *ssh, struct sshbuf *in, struct sshbuf *out)
{
  u_char buf[4096];
  int r, status;

  if (ssh->state->compression_in_started != 1)
    return SSH_ERR_INTERNAL_ERROR;

  if ((ssh->state->compression_in_stream.next_in =
      sshbuf_mutable_ptr(in)) == NULL)
    return SSH_ERR_INTERNAL_ERROR;
  ssh->state->compression_in_stream.avail_in = sshbuf_len(in);

  for (;;) {
    /* Set up fixed-size output buffer. */
    ssh->state->compression_in_stream.next_out = buf;
    ssh->state->compression_in_stream.avail_out = sizeof(buf);

    status = inflate(&ssh->state->compression_in_stream,
        Z_SYNC_FLUSH);
    switch (status) {
    case Z_OK:
      if ((r = sshbuf_put(out, buf, sizeof(buf) -
          ssh->state->compression_in_stream.avail_out)) != 0)
        return r;
      break;
    case Z_BUF_ERROR:
      /*
       * Comments in zlib.h say that we should keep calling
       * inflate() until we get an error.  This appears to
       * be the error that we get.
       */
      return 0;
    case Z_DATA_ERROR:
      return SSH_ERR_INVALID_FORMAT;
    case Z_MEM_ERROR:
      return SSH_ERR_ALLOC_FAIL;
    case Z_STREAM_ERROR:
    default:
      ssh->state->compression_in_failures++;
      return SSH_ERR_INTERNAL_ERROR;
    }
  }
  /* NOTREACHED */
}

#else /* WITH_ZLIB */

static int
start_compression_out(struct ssh *ssh, int level)
{
  return SSH_ERR_INTERNAL_ERROR;
}

static int
start_compression_in(struct ssh *ssh)
{
  return SSH_ERR_INTERNAL_ERROR;
}

static int
compress_buffer(struct ssh *ssh, struct sshbuf *in, struct sshbuf *out)
{
  return SSH_ERR_INTERNAL_ERROR;
}

static int
uncompress_buffer(struct ssh *ssh, struct sshbuf *in, struct sshbuf *out)
{
  return SSH_ERR_INTERNAL_ERROR;
}
#endif  /* WITH_ZLIB */

void
ssh_clear_newkeys(struct ssh *ssh, int mode)
{
  if (ssh->kex && ssh->kex->newkeys[mode]) {
    kex_free_newkeys(ssh->kex->newkeys[mode]);
    ssh->kex->newkeys[mode] = NULL;
  }
}

int
ssh_set_newkeys(struct ssh *ssh, int mode)
{
  struct session_state *state = ssh->state;
  struct sshenc *enc;
  struct sshmac *mac;
  struct sshcomp *comp;
  struct sshcipher_ctx **ccp;
  struct packet_state *ps;
  u_int64_t *max_blocks;
  const char *wmsg;
  int r, crypt_type;
  const char *dir = mode == MODE_OUT ? "out" : "in";

  debug2_f("mode %d", mode);

  if (mode == MODE_OUT) {
    ccp = &state->send_context;
    crypt_type = CIPHER_ENCRYPT;
    ps = &state->p_send;
    max_blocks = &state->max_blocks_out;
  } else {
    ccp = &state->receive_context;
    crypt_type = CIPHER_DECRYPT;
    ps = &state->p_read;
    max_blocks = &state->max_blocks_in;
  }
  if (state->newkeys[mode] != NULL) {
    debug_f("rekeying %s, input %llu bytes %llu blocks, "
        "output %llu bytes %llu blocks", dir,
        (unsigned long long)state->p_read.bytes,
        (unsigned long long)state->p_read.blocks,
        (unsigned long long)state->p_send.bytes,
        (unsigned long long)state->p_send.blocks);
    kex_free_newkeys(state->newkeys[mode]);
    state->newkeys[mode] = NULL;
  }
  /* note that both bytes and the seqnr are not reset */
  ps->packets = ps->blocks = 0;
  /* move newkeys from kex to state */
  if ((state->newkeys[mode] = ssh->kex->newkeys[mode]) == NULL)
    return SSH_ERR_INTERNAL_ERROR;
  ssh->kex->newkeys[mode] = NULL;
  enc  = &state->newkeys[mode]->enc;
  mac  = &state->newkeys[mode]->mac;
  comp = &state->newkeys[mode]->comp;
  if (cipher_authlen(enc->cipher) == 0) {
    if ((r = mac_init(mac)) != 0)
      return r;
  }
  mac->enabled = 1;
  DBG(debug_f("cipher_init: %s", dir));
  cipher_free(*ccp);
  *ccp = NULL;
  if ((r = cipher_init(ccp, enc->cipher, enc->key, enc->key_len,
      enc->iv, enc->iv_len, crypt_type)) != 0)
    return r;
  if (!state->cipher_warning_done &&
      (wmsg = cipher_warning_message(*ccp)) != NULL) {
    error("Warning: %s", wmsg);
    state->cipher_warning_done = 1;
  }
  /* Deleting the keys does not gain extra security */
  /* explicit_bzero(enc->iv,  enc->block_size);
     explicit_bzero(enc->key, enc->key_len);
     explicit_bzero(mac->key, mac->key_len); */
  if (((comp->type == COMP_DELAYED && state->after_authentication)) &&
      comp->enabled == 0) {
    if ((r = ssh_packet_init_compression(ssh)) < 0)
      return r;
    if (mode == MODE_OUT) {
      if ((r = start_compression_out(ssh, 6)) != 0)
        return r;
    } else {
      if ((r = start_compression_in(ssh)) != 0)
        return r;
    }
    comp->enabled = 1;
  }
  /*
   * The 2^(blocksize*2) limit is too expensive for 3DES,
   * so enforce a 1GB limit for small blocksizes.
   * See RFC4344 section 3.2.
   */
  if (enc->block_size >= 16)
    *max_blocks = (u_int64_t)1 << (enc->block_size*2);
  else
    *max_blocks = ((u_int64_t)1 << 30) / enc->block_size;
  if (state->rekey_limit)
    *max_blocks = MINIMUM(*max_blocks,
        state->rekey_limit / enc->block_size);
  debug("rekey %s after %llu blocks", dir,
      (unsigned long long)*max_blocks);
  return 0;
}

#define MAX_PACKETS (1U<<31)
static int
ssh_packet_need_rekeying(struct ssh *ssh, u_int outbound_packet_len)
{
  struct session_state *state = ssh->state;
  u_int32_t out_blocks;

  /* XXX client can't cope with rekeying pre-auth */
  if (!state->after_authentication)
    return 0;

  /* Haven't keyed yet or KEX in progress. */
  if (ssh_packet_is_rekeying(ssh))
    return 0;

  /* Peer can't rekey */
  if (ssh->compat & SSH_BUG_NOREKEY)
    return 0;

  /*
   * Permit one packet in or out per rekey - this allows us to
   * make progress when rekey limits are very small.
   */
  if (state->p_send.packets == 0 && state->p_read.packets == 0)
    return 0;

  /* Time-based rekeying */
  if (state->rekey_interval != 0 &&
      (int64_t)state->rekey_time + state->rekey_interval <= monotime())
    return 1;

  /*
   * Always rekey when MAX_PACKETS sent in either direction
   * As per RFC4344 section 3.1 we do this after 2^31 packets.
   */
  if (state->p_send.packets > MAX_PACKETS ||
      state->p_read.packets > MAX_PACKETS)
    return 1;

  /* Rekey after (cipher-specific) maximum blocks */
  out_blocks = ROUNDUP(outbound_packet_len,
      state->newkeys[MODE_OUT]->enc.block_size);
  return (state->max_blocks_out &&
      (state->p_send.blocks + out_blocks > state->max_blocks_out)) ||
      (state->max_blocks_in &&
      (state->p_read.blocks > state->max_blocks_in));
}

int
ssh_packet_check_rekey(struct ssh *ssh)
{
  if (!ssh_packet_need_rekeying(ssh, 0))
    return 0;
  debug3_f("rekex triggered");
  return kex_start_rekex(ssh);
}

/*
 * Delayed compression for SSH2 is enabled after authentication:
 * This happens on the server side after a SSH2_MSG_USERAUTH_SUCCESS is sent,
 * and on the client side after a SSH2_MSG_USERAUTH_SUCCESS is received.
 */
static int
ssh_packet_enable_delayed_compress(struct ssh *ssh)
{
  struct session_state *state = ssh->state;
  struct sshcomp *comp = NULL;
  int r, mode;

  /*
   * Remember that we are past the authentication step, so rekeying
   * with COMP_DELAYED will turn on compression immediately.
   */
  state->after_authentication = 1;
  for (mode = 0; mode < MODE_MAX; mode++) {
    /* protocol error: USERAUTH_SUCCESS received before NEWKEYS */
    if (state->newkeys[mode] == NULL)
      continue;
    comp = &state->newkeys[mode]->comp;
    if (comp && !comp->enabled && comp->type == COMP_DELAYED) {
      if ((r = ssh_packet_init_compression(ssh)) != 0)
        return r;
      if (mode == MODE_OUT) {
        if ((r = start_compression_out(ssh, 6)) != 0)
          return r;
      } else {
        if ((r = start_compression_in(ssh)) != 0)
          return r;
      }
      comp->enabled = 1;
    }
  }
  return 0;
}

/* Used to mute debug logging for noisy packet types */
int
ssh_packet_log_type(u_char type)
{
  switch (type) {
  case SSH2_MSG_PING:
  case SSH2_MSG_PONG:
  case SSH2_MSG_CHANNEL_DATA:
  case SSH2_MSG_CHANNEL_EXTENDED_DATA:
  case SSH2_MSG_CHANNEL_WINDOW_ADJUST:
    return 0;
  default:
    return 1;
  }
}

/*
 * Finalize packet in SSH2 format (compress, mac, encrypt, enqueue)
 */
int
ssh_packet_send2_wrapped(struct ssh *ssh)
{
  struct session_state *state = ssh->state;
  u_char type, *cp, macbuf[SSH_DIGEST_MAX_LENGTH];
  u_char tmp, padlen, pad = 0;
  u_int authlen = 0, aadlen = 0;
  u_int len;
  struct sshenc *enc   = NULL;
  struct sshmac *mac   = NULL;
  struct sshcomp *comp = NULL;
  int r, block_size;

  if (state->newkeys[MODE_OUT] != NULL) {
    enc  = &state->newkeys[MODE_OUT]->enc;
    mac  = &state->newkeys[MODE_OUT]->mac;
    comp = &state->newkeys[MODE_OUT]->comp;
    /* disable mac for authenticated encryption */
    if ((authlen = cipher_authlen(enc->cipher)) != 0)
      mac = NULL;
  }
  block_size = enc ? enc->block_size : 8;
  aadlen = (mac && mac->enabled && mac->etm) || authlen ? 4 : 0;

  type = (sshbuf_ptr(state->outgoing_packet))[5];
  if (ssh_packet_log_type(type))
    debug3("send packet: type %u", type);
#ifdef PACKET_DEBUG
  fprintf(stderr, "plain:     ");
  sshbuf_dump(state->outgoing_packet, stderr);
#endif

  if (comp && comp->enabled) {
    len = sshbuf_len(state->outgoing_packet);
    /* skip header, compress only payload */
    if ((r = sshbuf_consume(state->outgoing_packet, 5)) != 0)
      goto out;
    sshbuf_reset(state->compression_buffer);
    if ((r = compress_buffer(ssh, state->outgoing_packet,
        state->compression_buffer)) != 0)
      goto out;
    sshbuf_reset(state->outgoing_packet);
    if ((r = sshbuf_put(state->outgoing_packet,
        "\0\0\0\0\0", 5)) != 0 ||
        (r = sshbuf_putb(state->outgoing_packet,
        state->compression_buffer)) != 0)
      goto out;
    DBG(debug("compression: raw %d compressed %zd", len,
        sshbuf_len(state->outgoing_packet)));
  }

  /* sizeof (packet_len + pad_len + payload) */
  len = sshbuf_len(state->outgoing_packet);

  /*
   * calc size of padding, alloc space, get random data,
   * minimum padding is 4 bytes
   */
  len -= aadlen; /* packet length is not encrypted for EtM modes */
  padlen = block_size - (len % block_size);
  if (padlen < 4)
    padlen += block_size;
  if (state->extra_pad) {
    tmp = state->extra_pad;
    state->extra_pad =
        ROUNDUP(state->extra_pad, block_size);
    /* check if roundup overflowed */
    if (state->extra_pad < tmp)
      return SSH_ERR_INVALID_ARGUMENT;
    tmp = (len + padlen) % state->extra_pad;
    /* Check whether pad calculation below will underflow */
    if (tmp > state->extra_pad)
      return SSH_ERR_INVALID_ARGUMENT;
    pad = state->extra_pad - tmp;
    DBG(debug3_f("adding %d (len %d padlen %d extra_pad %d)",
        pad, len, padlen, state->extra_pad));
    tmp = padlen;
    padlen += pad;
    /* Check whether padlen calculation overflowed */
    if (padlen < tmp)
      return SSH_ERR_INVALID_ARGUMENT; /* overflow */
    state->extra_pad = 0;
  }
  if ((r = sshbuf_reserve(state->outgoing_packet, padlen, &cp)) != 0)
    goto out;
  if (enc && !cipher_ctx_is_plaintext(state->send_context)) {
    /* random padding */
    arc4random_buf(cp, padlen);
  } else {
    /* clear padding */
    explicit_bzero(cp, padlen);
  }
  /* sizeof (packet_len + pad_len + payload + padding) */
  len = sshbuf_len(state->outgoing_packet);
  cp = sshbuf_mutable_ptr(state->outgoing_packet);
  if (cp == NULL) {
    r = SSH_ERR_INTERNAL_ERROR;
    goto out;
  }
  /* packet_length includes payload, padding and padding length field */
  POKE_U32(cp, len - 4);
  cp[4] = padlen;
  DBG(debug("send: len %d (includes padlen %d, aadlen %d)",
      len, padlen, aadlen));

  /* compute MAC over seqnr and packet(length fields, payload, padding) */
  if (mac && mac->enabled && !mac->etm) {
    if ((r = mac_compute(mac, state->p_send.seqnr,
        sshbuf_ptr(state->outgoing_packet), len,
        macbuf, sizeof(macbuf))) != 0)
      goto out;
    DBG(debug("done calc MAC out #%d", state->p_send.seqnr));
  }
  /* encrypt packet and append to output buffer. */
  if ((r = sshbuf_reserve(state->output,
      sshbuf_len(state->outgoing_packet) + authlen, &cp)) != 0)
    goto out;
  if ((r = cipher_crypt(state->send_context, state->p_send.seqnr, cp,
      sshbuf_ptr(state->outgoing_packet),
      len - aadlen, aadlen, authlen)) != 0)
    goto out;
  /* append unencrypted MAC */
  if (mac && mac->enabled) {
    if (mac->etm) {
      /* EtM: compute mac over aadlen + cipher text */
      if ((r = mac_compute(mac, state->p_send.seqnr,
          cp, len, macbuf, sizeof(macbuf))) != 0)
        goto out;
      DBG(debug("done calc MAC(EtM) out #%d",
          state->p_send.seqnr));
    }
    if ((r = sshbuf_put(state->output, macbuf, mac->mac_len)) != 0)
      goto out;
  }
#ifdef PACKET_DEBUG
  fprintf(stderr, "encrypted: ");
  sshbuf_dump(state->output, stderr);
#endif
  /* increment sequence number for outgoing packets */
  if (++state->p_send.seqnr == 0) {
    if ((ssh->kex->flags & KEX_INITIAL) != 0) {
      ssh_packet_disconnect(ssh, "outgoing sequence number "
          "wrapped during initial key exchange");
    }
    logit("outgoing seqnr wraps around");
  }
  if (++state->p_send.packets == 0)
    if (!(ssh->compat & SSH_BUG_NOREKEY))
      return SSH_ERR_NEED_REKEY;
  state->p_send.blocks += len / block_size;
  state->p_send.bytes += len;
  sshbuf_reset(state->outgoing_packet);

  if (type == SSH2_MSG_NEWKEYS && ssh->kex->kex_strict) {
    debug_f("resetting send seqnr %u", state->p_send.seqnr);
    state->p_send.seqnr = 0;
  }

  if (type == SSH2_MSG_NEWKEYS)
    r = ssh_set_newkeys(ssh, MODE_OUT);
  else if (type == SSH2_MSG_USERAUTH_SUCCESS && state->server_side)
    r = ssh_packet_enable_delayed_compress(ssh);
  else
    r = 0;
 out:
  return r;
}

/* returns non-zero if the specified packet type is usec by KEX */
static int
ssh_packet_type_is_kex(u_char type)
{
  return
      type >= SSH2_MSG_TRANSPORT_MIN &&
      type <= SSH2_MSG_TRANSPORT_MAX &&
      type != SSH2_MSG_SERVICE_REQUEST &&
      type != SSH2_MSG_SERVICE_ACCEPT &&
      type != SSH2_MSG_EXT_INFO;
}

int
ssh_packet_send2(struct ssh *ssh)
{
  struct session_state *state = ssh->state;
  struct packet *p;
  u_char type;
  int r, need_rekey;

  if (sshbuf_len(state->outgoing_packet) < 6)
    return SSH_ERR_INTERNAL_ERROR;
  type = sshbuf_ptr(state->outgoing_packet)[5];
  need_rekey = !ssh_packet_type_is_kex(type) &&
      ssh_packet_need_rekeying(ssh, sshbuf_len(state->outgoing_packet));

  /*
   * During rekeying we can only send key exchange messages.
   * Queue everything else.
   */
  if ((need_rekey || state->rekeying) && !ssh_packet_type_is_kex(type)) {
    if (need_rekey)
      debug3_f("rekex triggered");
    debug("enqueue packet: %u", type);
    p = calloc(1, sizeof(*p));
    if (p == NULL)
      return SSH_ERR_ALLOC_FAIL;
    p->type = type;
    p->payload = state->outgoing_packet;
    TAILQ_INSERT_TAIL(&state->outgoing, p, next);
    state->outgoing_packet = sshbuf_new();
    if (state->outgoing_packet == NULL)
      return SSH_ERR_ALLOC_FAIL;
    if (need_rekey) {
      /*
       * This packet triggered a rekey, so send the
       * KEXINIT now.
       * NB. reenters this function via kex_start_rekex().
       */
      return kex_start_rekex(ssh);
    }
    return 0;
  }

  /* rekeying starts with sending KEXINIT */
  if (type == SSH2_MSG_KEXINIT)
    state->rekeying = 1;

  if ((r = ssh_packet_send2_wrapped(ssh)) != 0)
    return r;

  /* after a NEWKEYS message we can send the complete queue */
  if (type == SSH2_MSG_NEWKEYS) {
    state->rekeying = 0;
    state->rekey_time = monotime();
    while ((p = TAILQ_FIRST(&state->outgoing))) {
      type = p->type;
      /*
       * If this packet triggers a rekex, then skip the
       * remaining packets in the queue for now.
       * NB. re-enters this function via kex_start_rekex.
       */
      if (ssh_packet_need_rekeying(ssh,
          sshbuf_len(p->payload))) {
        debug3_f("queued packet triggered rekex");
        return kex_start_rekex(ssh);
      }
      debug("dequeue packet: %u", type);
      sshbuf_free(state->outgoing_packet);
      state->outgoing_packet = p->payload;
      TAILQ_REMOVE(&state->outgoing, p, next);
      memset(p, 0, sizeof(*p));
      free(p);
      if ((r = ssh_packet_send2_wrapped(ssh)) != 0)
        return r;
    }
  }
  return 0;
}

/*
 * 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
ssh_packet_read_seqnr(struct ssh *ssh, u_char *typep, u_int32_t *seqnr_p)
{
  struct session_state *state = ssh->state;
  int len, r, ms_remain = 0;
  struct pollfd pfd;
  char buf[8192];
  struct timeval start;
  struct timespec timespec, *timespecp = NULL;

  DBG(debug("packet_read()"));

  /*
   * Since we are blocking, ensure that all written packets have
   * been sent.
   */
  if ((r = ssh_packet_write_wait(ssh)) != 0)
    goto out;

  /* Stay in the loop until we have received a complete packet. */
  for (;;) {
    /* Try to read a packet from the buffer. */
    if ((r = ssh_packet_read_poll_seqnr(ssh, typep, seqnr_p)) != 0)
      break;
    /* If we got a packet, return it. */
    if (*typep != SSH_MSG_NONE)
      break;
    /*
     * Otherwise, wait for some data to arrive, add it to the
     * buffer, and try again.
     */
    pfd.fd = state->connection_in;
    pfd.events = POLLIN;

    if (state->packet_timeout_ms > 0) {
      ms_remain = state->packet_timeout_ms;
      timespecp = &timespec;
    }
    /* Wait for some data to arrive. */
    for (;;) {
      if (state->packet_timeout_ms > 0) {
        ms_to_timespec(&timespec, ms_remain);
        monotime_tv(&start);
      }
      if ((r = ppoll(&pfd, 1, timespecp, NULL)) >= 0)
        break;
      if (errno != EAGAIN && errno != EINTR &&
          errno != EWOULDBLOCK) {
        r = SSH_ERR_SYSTEM_ERROR;
        goto out;
      }
      if (state->packet_timeout_ms <= 0)
        continue;
      ms_subtract_diff(&start, &ms_remain);
      if (ms_remain <= 0) {
        r = 0;
        break;
      }
    }
    if (r == 0) {
      r = SSH_ERR_CONN_TIMEOUT;
      goto out;
    }
    /* Read data from the socket. */
    len = read(state->connection_in, buf, sizeof(buf));
    if (len == 0) {
      r = SSH_ERR_CONN_CLOSED;
      goto out;
    }
    if (len == -1) {
      r = SSH_ERR_SYSTEM_ERROR;
      goto out;
    }

    /* Append it to the buffer. */
    if ((r = ssh_packet_process_incoming(ssh, buf, len)) != 0)
      goto out;
  }
 out:
  return r;
}

int
ssh_packet_read(struct ssh *ssh)
{
  u_char type;
  int r;

  if ((r = ssh_packet_read_seqnr(ssh, &type, NULL)) != 0)
    fatal_fr(r, "read");
  return type;
}

static int
ssh_packet_read_poll2_mux(struct ssh *ssh, u_char *typep, u_int32_t *seqnr_p)
{
  struct session_state *state = ssh->state;
  const u_char *cp;
  size_t need;
  int r;

  if (ssh->kex)
    return SSH_ERR_INTERNAL_ERROR;
  *typep = SSH_MSG_NONE;
  cp = sshbuf_ptr(state->input);
  if (state->packlen == 0) {
    if (sshbuf_len(state->input) < 4 + 1)
      return 0; /* packet is incomplete */
    state->packlen = PEEK_U32(cp);
    if (state->packlen < 4 + 1 ||
        state->packlen > PACKET_MAX_SIZE)
      return SSH_ERR_MESSAGE_INCOMPLETE;
  }
  need = state->packlen + 4;
  if (sshbuf_len(state->input) < need)
    return 0; /* packet is incomplete */
  sshbuf_reset(state->incoming_packet);
  if ((r = sshbuf_put(state->incoming_packet, cp + 4,
      state->packlen)) != 0 ||
      (r = sshbuf_consume(state->input, need)) != 0 ||
      (r = sshbuf_get_u8(state->incoming_packet, NULL)) != 0 ||
      (r = sshbuf_get_u8(state->incoming_packet, typep)) != 0)
    return r;
  if (ssh_packet_log_type(*typep))
    debug3_f("type %u", *typep);
  /* sshbuf_dump(state->incoming_packet, stderr); */
  /* reset for next packet */
  state->packlen = 0;
  return r;
}

int
ssh_packet_read_poll2(struct ssh *ssh, u_char *typep, u_int32_t *seqnr_p)
{
  struct session_state *state = ssh->state;
  u_int padlen, need;
  u_char *cp;
  u_int maclen, aadlen = 0, authlen = 0, block_size;
  struct sshenc *enc   = NULL;
  struct sshmac *mac   = NULL;
  struct sshcomp *comp = NULL;
  int r;

  if (state->mux)
    return ssh_packet_read_poll2_mux(ssh, typep, seqnr_p);

  *typep = SSH_MSG_NONE;

  if (state->packet_discard)
    return 0;

  if (state->newkeys[MODE_IN] != NULL) {
    enc  = &state->newkeys[MODE_IN]->enc;
    mac  = &state->newkeys[MODE_IN]->mac;
    comp = &state->newkeys[MODE_IN]->comp;
    /* disable mac for authenticated encryption */
    if ((authlen = cipher_authlen(enc->cipher)) != 0)
      mac = NULL;
  }
  maclen = mac && mac->enabled ? mac->mac_len : 0;
  block_size = enc ? enc->block_size : 8;
  aadlen = (mac && mac->enabled && mac->etm) || authlen ? 4 : 0;

  if (aadlen && state->packlen == 0) {
    if (cipher_get_length(state->receive_context,
        &state->packlen, state->p_read.seqnr,
        sshbuf_ptr(state->input), sshbuf_len(state->input)) != 0)
      return 0;
    if (state->packlen < 1 + 4 ||
        state->packlen > PACKET_MAX_SIZE) {
#ifdef PACKET_DEBUG
      sshbuf_dump(state->input, stderr);
#endif
      logit("Bad packet length %u.", state->packlen);
      if ((r = sshpkt_disconnect(ssh, "Packet corrupt")) != 0)
        return r;
      return SSH_ERR_CONN_CORRUPT;
    }
    sshbuf_reset(state->incoming_packet);
  } else if (state->packlen == 0) {
    /*
     * check if input size is less than the cipher block size,
     * decrypt first block and extract length of incoming packet
     */
    if (sshbuf_len(state->input) < block_size)
      return 0;
    sshbuf_reset(state->incoming_packet);
    if ((r = sshbuf_reserve(state->incoming_packet, block_size,
        &cp)) != 0)
      goto out;
    if ((r = cipher_crypt(state->receive_context,
        state->p_send.seqnr, cp, sshbuf_ptr(state->input),
        block_size, 0, 0)) != 0)
      goto out;
    state->packlen = PEEK_U32(sshbuf_ptr(state->incoming_packet));
    if (state->packlen < 1 + 4 ||
        state->packlen > PACKET_MAX_SIZE) {
#ifdef PACKET_DEBUG
      fprintf(stderr, "input: \n");
      sshbuf_dump(state->input, stderr);
      fprintf(stderr, "incoming_packet: \n");
      sshbuf_dump(state->incoming_packet, stderr);
#endif
      logit("Bad packet length %u.", state->packlen);
      return ssh_packet_start_discard(ssh, enc, mac, 0,
          PACKET_MAX_SIZE);
    }
    if ((r = sshbuf_consume(state->input, block_size)) != 0)
      goto out;
  }
  DBG(debug("input: packet len %u", state->packlen+4));

  if (aadlen) {
    /* only the payload is encrypted */
    need = state->packlen;
  } else {
    /*
     * the payload size and the payload are encrypted, but we
     * have a partial packet of block_size bytes
     */
    need = 4 + state->packlen - block_size;
  }
  DBG(debug("partial packet: block %d, need %d, maclen %d, authlen %d,"
      " aadlen %d", block_size, need, maclen, authlen, aadlen));
  if (need % block_size != 0) {
    logit("padding error: need %d block %d mod %d",
        need, block_size, need % block_size);
    return ssh_packet_start_discard(ssh, enc, mac, 0,
        PACKET_MAX_SIZE - block_size);
  }
  /*
   * check if the entire packet has been received and
   * decrypt into incoming_packet:
   * 'aadlen' bytes are unencrypted, but authenticated.
   * 'need' bytes are encrypted, followed by either
   * 'authlen' bytes of authentication tag or
   * 'maclen' bytes of message authentication code.
   */
  if (sshbuf_len(state->input) < aadlen + need + authlen + maclen)
    return 0; /* packet is incomplete */
#ifdef PACKET_DEBUG
  fprintf(stderr, "read_poll enc/full: ");
  sshbuf_dump(state->input, stderr);
#endif
  /* EtM: check mac over encrypted input */
  if (mac && mac->enabled && mac->etm) {
    if ((r = mac_check(mac, state->p_read.seqnr,
        sshbuf_ptr(state->input), aadlen + need,
        sshbuf_ptr(state->input) + aadlen + need + authlen,
        maclen)) != 0) {
      if (r == SSH_ERR_MAC_INVALID)
        logit("Corrupted MAC on input.");
      goto out;
    }
  }
  if ((r = sshbuf_reserve(state->incoming_packet, aadlen + need,
      &cp)) != 0)
    goto out;
  if ((r = cipher_crypt(state->receive_context, state->p_read.seqnr, cp,
      sshbuf_ptr(state->input), need, aadlen, authlen)) != 0)
    goto out;
  if ((r = sshbuf_consume(state->input, aadlen + need + authlen)) != 0)
    goto out;
  if (mac && mac->enabled) {
    /* Not EtM: check MAC over cleartext */
    if (!mac->etm && (r = mac_check(mac, state->p_read.seqnr,
        sshbuf_ptr(state->incoming_packet),
        sshbuf_len(state->incoming_packet),
        sshbuf_ptr(state->input), maclen)) != 0) {
      if (r != SSH_ERR_MAC_INVALID)
        goto out;
      logit("Corrupted MAC on input.");
      if (need + block_size > PACKET_MAX_SIZE)
        return SSH_ERR_INTERNAL_ERROR;
      return ssh_packet_start_discard(ssh, enc, mac,
          sshbuf_len(state->incoming_packet),
          PACKET_MAX_SIZE - need - block_size);
    }
    /* Remove MAC from input buffer */
    DBG(debug("MAC #%d ok", state->p_read.seqnr));
    if ((r = sshbuf_consume(state->input, mac->mac_len)) != 0)
      goto out;
  }

  if (seqnr_p != NULL)
    *seqnr_p = state->p_read.seqnr;
  if (++state->p_read.seqnr == 0) {
    if ((ssh->kex->flags & KEX_INITIAL) != 0) {
      ssh_packet_disconnect(ssh, "incoming sequence number "
          "wrapped during initial key exchange");
    }
    logit("incoming seqnr wraps around");
  }
  if (++state->p_read.packets == 0)
    if (!(ssh->compat & SSH_BUG_NOREKEY))
      return SSH_ERR_NEED_REKEY;
  state->p_read.blocks += (state->packlen + 4) / block_size;
  state->p_read.bytes += state->packlen + 4;

  /* get padlen */
  padlen = sshbuf_ptr(state->incoming_packet)[4];
  DBG(debug("input: padlen %d", padlen));
  if (padlen < 4)  {
    if ((r = sshpkt_disconnect(ssh,
        "Corrupted padlen %d on input.", padlen)) != 0 ||
        (r = ssh_packet_write_wait(ssh)) != 0)
      return r;
    return SSH_ERR_CONN_CORRUPT;
  }

  /* skip packet size + padlen, discard padding */
  if ((r = sshbuf_consume(state->incoming_packet, 4 + 1)) != 0 ||
      ((r = sshbuf_consume_end(state->incoming_packet, padlen)) != 0))
    goto out;

  DBG(debug("input: len before de-compress %zd",
      sshbuf_len(state->incoming_packet)));
  if (comp && comp->enabled) {
    sshbuf_reset(state->compression_buffer);
    if ((r = uncompress_buffer(ssh, state->incoming_packet,
        state->compression_buffer)) != 0)
      goto out;
    sshbuf_reset(state->incoming_packet);
    if ((r = sshbuf_putb(state->incoming_packet,
        state->compression_buffer)) != 0)
      goto out;
    DBG(debug("input: len after de-compress %zd",
        sshbuf_len(state->incoming_packet)));
  }
  /*
   * get packet type, implies consume.
   * return length of payload (without type field)
   */
  if ((r = sshbuf_get_u8(state->incoming_packet, typep)) != 0)
    goto out;
  if (ssh_packet_log_type(*typep))
    debug3("receive packet: type %u", *typep);
  if (*typep < SSH2_MSG_MIN) {
    if ((r = sshpkt_disconnect(ssh,
        "Invalid ssh2 packet type: %d", *typep)) != 0 ||
        (r = ssh_packet_write_wait(ssh)) != 0)
      return r;
    return SSH_ERR_PROTOCOL_ERROR;
  }
  if (state->hook_in != NULL &&
      (r = state->hook_in(ssh, state->incoming_packet, typep,
      state->hook_in_ctx)) != 0)
    return r;
  if (*typep == SSH2_MSG_USERAUTH_SUCCESS && !state->server_side)
    r = ssh_packet_enable_delayed_compress(ssh);
  else
    r = 0;
#ifdef PACKET_DEBUG
  fprintf(stderr, "read/plain[%d]:\r\n", *typep);
  sshbuf_dump(state->incoming_packet, stderr);
#endif
  /* reset for next packet */
  state->packlen = 0;
  if (*typep == SSH2_MSG_NEWKEYS && ssh->kex->kex_strict) {
    debug_f("resetting read seqnr %u", state->p_read.seqnr);
    state->p_read.seqnr = 0;
  }

  if ((r = ssh_packet_check_rekey(ssh)) != 0)
    return r;
 out:
  return r;
}

int
ssh_packet_read_poll_seqnr(struct ssh *ssh, u_char *typep, u_int32_t *seqnr_p)
{
  struct session_state *state = ssh->state;
  u_int reason, seqnr;
  int r;
  u_char *msg;
  const u_char *d;
  size_t len;

  for (;;) {
    msg = NULL;
    r = ssh_packet_read_poll2(ssh, typep, seqnr_p);
    if (r != 0)
      return r;
    if (*typep == 0) {
      /* no message ready */
      return 0;
    }
    state->keep_alive_timeouts = 0;
    DBG(debug("received packet type %d", *typep));

    /* Always process disconnect messages */
    if (*typep == SSH2_MSG_DISCONNECT) {
      if ((r = sshpkt_get_u32(ssh, &reason)) != 0 ||
          (r = sshpkt_get_string(ssh, &msg, NULL)) != 0)
        return r;
      /* Ignore normal client exit notifications */
      do_log2(ssh->state->server_side &&
          reason == SSH2_DISCONNECT_BY_APPLICATION ?
          SYSLOG_LEVEL_INFO : SYSLOG_LEVEL_ERROR,
          "Received disconnect from %s port %d:"
          "%u: %.400s", ssh_remote_ipaddr(ssh),
          ssh_remote_port(ssh), reason, msg);
      free(msg);
      return SSH_ERR_DISCONNECTED;
    }

    /*
     * Do not implicitly handle any messages here during initial
     * KEX when in strict mode. They will be need to be allowed
     * explicitly by the KEX dispatch table or they will generate
     * protocol errors.
     */
    if (ssh->kex != NULL &&
        (ssh->kex->flags & KEX_INITIAL) && ssh->kex->kex_strict)
      return 0;
    /* Implicitly handle transport-level messages */
    switch (*typep) {
    case SSH2_MSG_IGNORE:
      debug3("Received SSH2_MSG_IGNORE");
      break;
    case SSH2_MSG_DEBUG:
      if ((r = sshpkt_get_u8(ssh, NULL)) != 0 ||
          (r = sshpkt_get_string(ssh, &msg, NULL)) != 0 ||
          (r = sshpkt_get_string(ssh, NULL, NULL)) != 0) {
        free(msg);
        return r;
      }
      debug("Remote: %.900s", msg);
      free(msg);
      break;
    case SSH2_MSG_UNIMPLEMENTED:
      if ((r = sshpkt_get_u32(ssh, &seqnr)) != 0)
        return r;
      debug("Received SSH2_MSG_UNIMPLEMENTED for %u",
          seqnr);
      break;
    case SSH2_MSG_PING:
      if ((r = sshpkt_get_string_direct(ssh, &d, &len)) != 0)
        return r;
      DBG(debug("Received SSH2_MSG_PING len %zu", len));
      if (!ssh->state->after_authentication) {
        DBG(debug("Won't reply to PING in preauth"));
        break;
      }
      if (ssh_packet_is_rekeying(ssh)) {
        DBG(debug("Won't reply to PING during KEX"));
        break;
      }
      if ((r = sshpkt_start(ssh, SSH2_MSG_PONG)) != 0 ||
          (r = sshpkt_put_string(ssh, d, len)) != 0 ||
          (r = sshpkt_send(ssh)) != 0)
        return r;
      break;
    case SSH2_MSG_PONG:
      if ((r = sshpkt_get_string_direct(ssh,
          NULL, &len)) != 0)
        return r;
      DBG(debug("Received SSH2_MSG_PONG len %zu", len));
      break;
    default:
      return 0;
    }
  }
}

/*
 * Buffers the supplied input data. This is intended to be used together
 * with packet_read_poll().
 */
int
ssh_packet_process_incoming(struct ssh *ssh, const char *buf, u_int len)
{
  struct session_state *state = ssh->state;
  int r;

  if (state->packet_discard) {
    state->keep_alive_timeouts = 0; /* ?? */
    if (len >= state->packet_discard) {
      if ((r = ssh_packet_stop_discard(ssh)) != 0)
        return r;
    }
    state->packet_discard -= len;
    return 0;
  }
  if ((r = sshbuf_put(state->input, buf, len)) != 0)
    return r;

  return 0;
}

/* Reads and buffers data from the specified fd */
int
ssh_packet_process_read(struct ssh *ssh, int fd)
{
  struct session_state *state = ssh->state;
  int r;
  size_t rlen;

  if ((r = sshbuf_read(fd, state->input, PACKET_MAX_SIZE, &rlen)) != 0)
    return r;

  if (state->packet_discard) {
    if ((r = sshbuf_consume_end(state->input, rlen)) != 0)
      return r;
    state->keep_alive_timeouts = 0; /* ?? */
    if (rlen >= state->packet_discard) {
      if ((r = ssh_packet_stop_discard(ssh)) != 0)
        return r;
    }
    state->packet_discard -= rlen;
    return 0;
  }
  return 0;
}

int
ssh_packet_remaining(struct ssh *ssh)
{
  return sshbuf_len(ssh->state->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 ssh_packet_write_wait.
 */
void
ssh_packet_send_debug(struct ssh *ssh, const char *fmt,...)
{
  char buf[1024];
  va_list args;
  int r;

  if ((ssh->compat & SSH_BUG_DEBUG))
    return;

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

  debug3("sending debug message: %s", buf);

  if ((r = sshpkt_start(ssh, SSH2_MSG_DEBUG)) != 0 ||
      (r = sshpkt_put_u8(ssh, 0)) != 0 || /* always display */
      (r = sshpkt_put_cstring(ssh, buf)) != 0 ||
      (r = sshpkt_put_cstring(ssh, "")) != 0 ||
      (r = sshpkt_send(ssh)) != 0 ||
      (r = ssh_packet_write_wait(ssh)) != 0)
    fatal_fr(r, "send DEBUG");
}

void
sshpkt_fmt_connection_id(struct ssh *ssh, char *s, size_t l)
{
  snprintf(s, l, "%.200s%s%s port %d",
      ssh->log_preamble ? ssh->log_preamble : "",
      ssh->log_preamble ? " " : "",
      ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
}

/*
 * Pretty-print connection-terminating errors and exit.
 */
static void
sshpkt_vfatal(struct ssh *ssh, int r, const char *fmt, va_list ap)
{
  char *tag = NULL, remote_id[512];
  int oerrno = errno;

  sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id));

  switch (r) {
  case SSH_ERR_CONN_CLOSED:
    ssh_packet_clear_keys(ssh);
    logdie("Connection closed by %s", remote_id);
  case SSH_ERR_CONN_TIMEOUT:
    ssh_packet_clear_keys(ssh);
    logdie("Connection %s %s timed out",
        ssh->state->server_side ? "from" : "to", remote_id);
  case SSH_ERR_DISCONNECTED:
    ssh_packet_clear_keys(ssh);
    logdie("Disconnected from %s", remote_id);
  case SSH_ERR_SYSTEM_ERROR:
    if (errno == ECONNRESET) {
      ssh_packet_clear_keys(ssh);
      logdie("Connection reset by %s", remote_id);
    }
    /* FALLTHROUGH */
  case SSH_ERR_NO_CIPHER_ALG_MATCH:
  case SSH_ERR_NO_MAC_ALG_MATCH:
  case SSH_ERR_NO_COMPRESS_ALG_MATCH:
  case SSH_ERR_NO_KEX_ALG_MATCH:
  case SSH_ERR_NO_HOSTKEY_ALG_MATCH:
    if (ssh->kex && ssh->kex->failed_choice) {
      ssh_packet_clear_keys(ssh);
      errno = oerrno;
      logdie("Unable to negotiate with %s: %s. "
          "Their offer: %s", remote_id, ssh_err(r),
          ssh->kex->failed_choice);
    }
    /* FALLTHROUGH */
  default:
    if (vasprintf(&tag, fmt, ap) == -1) {
      ssh_packet_clear_keys(ssh);
      logdie_f("could not allocate failure message");
    }
    ssh_packet_clear_keys(ssh);
    errno = oerrno;
    logdie_r(r, "%s%sConnection %s %s",
        tag != NULL ? tag : "", tag != NULL ? ": " : "",
        ssh->state->server_side ? "from" : "to", remote_id);
  }
}

void
sshpkt_fatal(struct ssh *ssh, int r, const char *fmt, ...)
{
  va_list ap;

  va_start(ap, fmt);
  sshpkt_vfatal(ssh, r, fmt, ap);
  /* NOTREACHED */
  va_end(ap);
  logdie_f("should have exited");
}

/*
 * 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
ssh_packet_disconnect(struct ssh *ssh, const char *fmt,...)
{
  char buf[1024], remote_id[512];
  va_list args;
  static int disconnecting = 0;
  int r;

  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.
   */
  sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id));
  va_start(args, fmt);
  vsnprintf(buf, sizeof(buf), fmt, args);
  va_end(args);

  /* Display the error locally */
  logit("Disconnecting %s: %.100s", remote_id, buf);

  /*
   * Send the disconnect message to the other side, and wait
   * for it to get sent.
   */
  if ((r = sshpkt_disconnect(ssh, "%s", buf)) != 0)
    sshpkt_fatal(ssh, r, "%s", __func__);

  if ((r = ssh_packet_write_wait(ssh)) != 0)
    sshpkt_fatal(ssh, r, "%s", __func__);

  /* Close the connection. */
  ssh_packet_close(ssh);
  cleanup_exit(255);
}

/*
 * Checks if there is any buffered output, and tries to write some of
 * the output.
 */
int
ssh_packet_write_poll(struct ssh *ssh)
{
  struct session_state *state = ssh->state;
  int len = sshbuf_len(state->output);
  int r;

  if (len > 0) {
    len = write(state->connection_out,
        sshbuf_ptr(state->output), len);
    if (len == -1) {
      if (errno == EINTR || errno == EAGAIN ||
          errno == EWOULDBLOCK)
        return 0;
      return SSH_ERR_SYSTEM_ERROR;
    }
    if (len == 0)
      return SSH_ERR_CONN_CLOSED;
    if ((r = sshbuf_consume(state->output, len)) != 0)
      return r;
  }
  return 0;
}

/*
 * Calls packet_write_poll repeatedly until all pending output data has been
 * written.
 */
int
ssh_packet_write_wait(struct ssh *ssh)
{
  int ret, r, ms_remain = 0;
  struct timeval start;
  struct timespec timespec, *timespecp = NULL;
  struct session_state *state = ssh->state;
  struct pollfd pfd;

  if ((r = ssh_packet_write_poll(ssh)) != 0)
    return r;
  while (ssh_packet_have_data_to_write(ssh)) {
    pfd.fd = state->connection_out;
    pfd.events = POLLOUT;

    if (state->packet_timeout_ms > 0) {
      ms_remain = state->packet_timeout_ms;
      timespecp = &timespec;
    }
    for (;;) {
      if (state->packet_timeout_ms > 0) {
        ms_to_timespec(&timespec, ms_remain);
        monotime_tv(&start);
      }
      if ((ret = ppoll(&pfd, 1, timespecp, NULL)) >= 0)
        break;
      if (errno != EAGAIN && errno != EINTR &&
          errno != EWOULDBLOCK)
        break;
      if (state->packet_timeout_ms <= 0)
        continue;
      ms_subtract_diff(&start, &ms_remain);
      if (ms_remain <= 0) {
        ret = 0;
        break;
      }
    }
    if (ret == 0)
      return SSH_ERR_CONN_TIMEOUT;
    if ((r = ssh_packet_write_poll(ssh)) != 0)
      return r;
  }
  return 0;
}

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

int
ssh_packet_have_data_to_write(struct ssh *ssh)
{
  return sshbuf_len(ssh->state->output) != 0;
}

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

int
ssh_packet_not_very_much_data_to_write(struct ssh *ssh)
{
  if (ssh->state->interactive_mode)
    return sshbuf_len(ssh->state->output) < 16384;
  else
    return sshbuf_len(ssh->state->output) < 128 * 1024;
}

/*
 * returns true when there are at most a few keystrokes of data to write
 * and the connection is in interactive mode.
 */

int
ssh_packet_interactive_data_to_write(struct ssh *ssh)
{
  return ssh->state->interactive_mode &&
      sshbuf_len(ssh->state->output) < 256;
}

void
ssh_packet_set_tos(struct ssh *ssh, int tos)
{
  if (!ssh_packet_connection_is_on_socket(ssh) || tos == INT_MAX)
    return;
  set_sock_tos(ssh->state->connection_in, tos);
}

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

void
ssh_packet_set_interactive(struct ssh *ssh, int interactive, int qos_interactive, int qos_bulk)
{
  struct session_state *state = ssh->state;

  if (state->set_interactive_called)
    return;
  state->set_interactive_called = 1;

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

  /* Only set socket options if using a socket.  */
  if (!ssh_packet_connection_is_on_socket(ssh))
    return;
  set_nodelay(state->connection_in);
  ssh_packet_set_tos(ssh, interactive ? qos_interactive : qos_bulk);
}

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

int
ssh_packet_is_interactive(struct ssh *ssh)
{
  return ssh->state->interactive_mode;
}

int
ssh_packet_set_maxsize(struct ssh *ssh, u_int s)
{
  struct session_state *state = ssh->state;

  if (state->set_maxsize_called) {
    logit_f("called twice: old %d new %d",
        state->max_packet_size, s);
    return -1;
  }
  if (s < 4 * 1024 || s > 1024 * 1024) {
    logit_f("bad size %d", s);
    return -1;
  }
  state->set_maxsize_called = 1;
  debug_f("setting to %d", s);
  state->max_packet_size = s;
  return s;
}

int
ssh_packet_inc_alive_timeouts(struct ssh *ssh)
{
  return ++ssh->state->keep_alive_timeouts;
}

void
ssh_packet_set_alive_timeouts(struct ssh *ssh, int ka)
{
  ssh->state->keep_alive_timeouts = ka;
}

u_int
ssh_packet_get_maxsize(struct ssh *ssh)
{
  return ssh->state->max_packet_size;
}

void
ssh_packet_set_rekey_limits(struct ssh *ssh, u_int64_t bytes, u_int32_t seconds)
{
  debug3("rekey after %llu bytes, %u seconds", (unsigned long long)bytes,
      (unsigned int)seconds);
  ssh->state->rekey_limit = bytes;
  ssh->state->rekey_interval = seconds;
}

time_t
ssh_packet_get_rekey_timeout(struct ssh *ssh)
{
  time_t seconds;

  seconds = ssh->state->rekey_time + ssh->state->rekey_interval -
      monotime();
  return (seconds <= 0 ? 1 : seconds);
}

void
ssh_packet_set_server(struct ssh *ssh)
{
  ssh->state->server_side = 1;
  ssh->kex->server = 1; /* XXX unify? */
}

void
ssh_packet_set_authenticated(struct ssh *ssh)
{
  ssh->state->after_authentication = 1;
}

void *
ssh_packet_get_input(struct ssh *ssh)
{
  return (void *)ssh->state->input;
}

void *
ssh_packet_get_output(struct ssh *ssh)
{
  return (void *)ssh->state->output;
}

/* Reset after_authentication and reset compression in post-auth privsep */
static int
ssh_packet_set_postauth(struct ssh *ssh)
{
  int r;

  debug_f("called");
  /* This was set in net child, but is not visible in user child */
  ssh->state->after_authentication = 1;
  ssh->state->rekeying = 0;
  if ((r = ssh_packet_enable_delayed_compress(ssh)) != 0)
    return r;
  return 0;
}

/* Packet state (de-)serialization for privsep */

/* turn kex into a blob for packet state serialization */
static int
kex_to_blob(struct sshbuf *m, struct kex *kex)
{
  int r;

  if ((r = sshbuf_put_u32(m, kex->we_need)) != 0 ||
      (r = sshbuf_put_cstring(m, kex->hostkey_alg)) != 0 ||
      (r = sshbuf_put_u32(m, kex->hostkey_type)) != 0 ||
      (r = sshbuf_put_u32(m, kex->hostkey_nid)) != 0 ||
      (r = sshbuf_put_u32(m, kex->kex_type)) != 0 ||
      (r = sshbuf_put_u32(m, kex->kex_strict)) != 0 ||
      (r = sshbuf_put_stringb(m, kex->my)) != 0 ||
      (r = sshbuf_put_stringb(m, kex->peer)) != 0 ||
      (r = sshbuf_put_stringb(m, kex->client_version)) != 0 ||
      (r = sshbuf_put_stringb(m, kex->server_version)) != 0 ||
      (r = sshbuf_put_stringb(m, kex->session_id)) != 0 ||
      (r = sshbuf_put_u32(m, kex->flags)) != 0)
    return r;
  return 0;
}

/* turn key exchange results into a blob for packet state serialization */
static int
newkeys_to_blob(struct sshbuf *m, struct ssh *ssh, int mode)
{
  struct sshbuf *b;
  struct sshcipher_ctx *cc;
  struct sshcomp *comp;
  struct sshenc *enc;
  struct sshmac *mac;
  struct newkeys *newkey;
  int r;

  if ((newkey = ssh->state->newkeys[mode]) == NULL)
    return SSH_ERR_INTERNAL_ERROR;
  enc = &newkey->enc;
  mac = &newkey->mac;
  comp = &newkey->comp;
  cc = (mode == MODE_OUT) ? ssh->state->send_context :
      ssh->state->receive_context;
  if ((r = cipher_get_keyiv(cc, enc->iv, enc->iv_len)) != 0)
    return r;
  if ((b = sshbuf_new()) == NULL)
    return SSH_ERR_ALLOC_FAIL;
  if ((r = sshbuf_put_cstring(b, enc->name)) != 0 ||
      (r = sshbuf_put_u32(b, enc->enabled)) != 0 ||
      (r = sshbuf_put_u32(b, enc->block_size)) != 0 ||
      (r = sshbuf_put_string(b, enc->key, enc->key_len)) != 0 ||
      (r = sshbuf_put_string(b, enc->iv, enc->iv_len)) != 0)
    goto out;
  if (cipher_authlen(enc->cipher) == 0) {
    if ((r = sshbuf_put_cstring(b, mac->name)) != 0 ||
        (r = sshbuf_put_u32(b, mac->enabled)) != 0 ||
        (r = sshbuf_put_string(b, mac->key, mac->key_len)) != 0)
      goto out;
  }
  if ((r = sshbuf_put_u32(b, comp->type)) != 0 ||
      (r = sshbuf_put_cstring(b, comp->name)) != 0)
    goto out;
  r = sshbuf_put_stringb(m, b);
 out:
  sshbuf_free(b);
  return r;
}

/* serialize packet state into a blob */
int
ssh_packet_get_state(struct ssh *ssh, struct sshbuf *m)
{
  struct session_state *state = ssh->state;
  int r;

  if ((r = kex_to_blob(m, ssh->kex)) != 0 ||
      (r = newkeys_to_blob(m, ssh, MODE_OUT)) != 0 ||
      (r = newkeys_to_blob(m, ssh, MODE_IN)) != 0 ||
      (r = sshbuf_put_u64(m, state->rekey_limit)) != 0 ||
      (r = sshbuf_put_u32(m, state->rekey_interval)) != 0 ||
      (r = sshbuf_put_u32(m, state->p_send.seqnr)) != 0 ||
      (r = sshbuf_put_u64(m, state->p_send.blocks)) != 0 ||
      (r = sshbuf_put_u32(m, state->p_send.packets)) != 0 ||
      (r = sshbuf_put_u64(m, state->p_send.bytes)) != 0 ||
      (r = sshbuf_put_u32(m, state->p_read.seqnr)) != 0 ||
      (r = sshbuf_put_u64(m, state->p_read.blocks)) != 0 ||
      (r = sshbuf_put_u32(m, state->p_read.packets)) != 0 ||
      (r = sshbuf_put_u64(m, state->p_read.bytes)) != 0 ||
      (r = sshbuf_put_stringb(m, state->input)) != 0 ||
      (r = sshbuf_put_stringb(m, state->output)) != 0)
    return r;

  return 0;
}

/* restore key exchange results from blob for packet state de-serialization */
static int
newkeys_from_blob(struct sshbuf *m, struct ssh *ssh, int mode)
{
  struct sshbuf *b = NULL;
  struct sshcomp *comp;
  struct sshenc *enc;
  struct sshmac *mac;
  struct newkeys *newkey = NULL;
  size_t keylen, ivlen, maclen;
  int r;

  if ((newkey = calloc(1, sizeof(*newkey))) == NULL) {
    r = SSH_ERR_ALLOC_FAIL;
    goto out;
  }
  if ((r = sshbuf_froms(m, &b)) != 0)
    goto out;
#ifdef DEBUG_PK
  sshbuf_dump(b, stderr);
#endif
  enc = &newkey->enc;
  mac = &newkey->mac;
  comp = &newkey->comp;

  if ((r = sshbuf_get_cstring(b, &enc->name, NULL)) != 0 ||
      (r = sshbuf_get_u32(b, (u_int *)&enc->enabled)) != 0 ||
      (r = sshbuf_get_u32(b, &enc->block_size)) != 0 ||
      (r = sshbuf_get_string(b, &enc->key, &keylen)) != 0 ||
      (r = sshbuf_get_string(b, &enc->iv, &ivlen)) != 0)
    goto out;
  if ((enc->cipher = cipher_by_name(enc->name)) == NULL) {
    r = SSH_ERR_INVALID_FORMAT;
    goto out;
  }
  if (cipher_authlen(enc->cipher) == 0) {
    if ((r = sshbuf_get_cstring(b, &mac->name, NULL)) != 0)
      goto out;
    if ((r = mac_setup(mac, mac->name)) != 0)
      goto out;
    if ((r = sshbuf_get_u32(b, (u_int *)&mac->enabled)) != 0 ||
        (r = sshbuf_get_string(b, &mac->key, &maclen)) != 0)
      goto out;
    if (maclen > mac->key_len) {
      r = SSH_ERR_INVALID_FORMAT;
      goto out;
    }
    mac->key_len = maclen;
  }
  if ((r = sshbuf_get_u32(b, &comp->type)) != 0 ||
      (r = sshbuf_get_cstring(b, &comp->name, NULL)) != 0)
    goto out;
  if (sshbuf_len(b) != 0) {
    r = SSH_ERR_INVALID_FORMAT;
    goto out;
  }
  enc->key_len = keylen;
  enc->iv_len = ivlen;
  ssh->kex->newkeys[mode] = newkey;
  newkey = NULL;
  r = 0;
 out:
  free(newkey);
  sshbuf_free(b);
  return r;
}

/* restore kex from blob for packet state de-serialization */
static int
kex_from_blob(struct sshbuf *m, struct kex **kexp)
{
  struct kex *kex;
  int r;

  if ((kex = kex_new()) == NULL)
    return SSH_ERR_ALLOC_FAIL;
  if ((r = sshbuf_get_u32(m, &kex->we_need)) != 0 ||
      (r = sshbuf_get_cstring(m, &kex->hostkey_alg, NULL)) != 0 ||
      (r = sshbuf_get_u32(m, (u_int *)&kex->hostkey_type)) != 0 ||
      (r = sshbuf_get_u32(m, (u_int *)&kex->hostkey_nid)) != 0 ||
      (r = sshbuf_get_u32(m, &kex->kex_type)) != 0 ||
      (r = sshbuf_get_u32(m, &kex->kex_strict)) != 0 ||
      (r = sshbuf_get_stringb(m, kex->my)) != 0 ||
      (r = sshbuf_get_stringb(m, kex->peer)) != 0 ||
      (r = sshbuf_get_stringb(m, kex->client_version)) != 0 ||
      (r = sshbuf_get_stringb(m, kex->server_version)) != 0 ||
      (r = sshbuf_get_stringb(m, kex->session_id)) != 0 ||
      (r = sshbuf_get_u32(m, &kex->flags)) != 0)
    goto out;
  kex->server = 1;
  kex->done = 1;
  r = 0;
 out:
  if (r != 0 || kexp == NULL) {
    kex_free(kex);
    if (kexp != NULL)
      *kexp = NULL;
  } else {
    kex_free(*kexp);
    *kexp = kex;
  }
  return r;
}

/*
 * Restore packet state from content of blob 'm' (de-serialization).
 * Note that 'm' will be partially consumed on parsing or any other errors.
 */
int
ssh_packet_set_state(struct ssh *ssh, struct sshbuf *m)
{
  struct session_state *state = ssh->state;
  const u_char *input, *output;
  size_t ilen, olen;
  int r;

  if ((r = kex_from_blob(m, &ssh->kex)) != 0 ||
      (r = newkeys_from_blob(m, ssh, MODE_OUT)) != 0 ||
      (r = newkeys_from_blob(m, ssh, MODE_IN)) != 0 ||
      (r = sshbuf_get_u64(m, &state->rekey_limit)) != 0 ||
      (r = sshbuf_get_u32(m, &state->rekey_interval)) != 0 ||
      (r = sshbuf_get_u32(m, &state->p_send.seqnr)) != 0 ||
      (r = sshbuf_get_u64(m, &state->p_send.blocks)) != 0 ||
      (r = sshbuf_get_u32(m, &state->p_send.packets)) != 0 ||
      (r = sshbuf_get_u64(m, &state->p_send.bytes)) != 0 ||
      (r = sshbuf_get_u32(m, &state->p_read.seqnr)) != 0 ||
      (r = sshbuf_get_u64(m, &state->p_read.blocks)) != 0 ||
      (r = sshbuf_get_u32(m, &state->p_read.packets)) != 0 ||
      (r = sshbuf_get_u64(m, &state->p_read.bytes)) != 0)
    return r;
  /*
   * We set the time here so that in post-auth privsep child we
   * count from the completion of the authentication.
   */
  state->rekey_time = monotime();
  /* XXX ssh_set_newkeys overrides p_read.packets? XXX */
  if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0 ||
      (r = ssh_set_newkeys(ssh, MODE_OUT)) != 0)
    return r;

  if ((r = ssh_packet_set_postauth(ssh)) != 0)
    return r;

  sshbuf_reset(state->input);
  sshbuf_reset(state->output);
  if ((r = sshbuf_get_string_direct(m, &input, &ilen)) != 0 ||
      (r = sshbuf_get_string_direct(m, &output, &olen)) != 0 ||
      (r = sshbuf_put(state->input, input, ilen)) != 0 ||
      (r = sshbuf_put(state->output, output, olen)) != 0)
    return r;

  if (sshbuf_len(m))
    return SSH_ERR_INVALID_FORMAT;
  debug3_f("done");
  return 0;
}

/* NEW API */

/* put data to the outgoing packet */

int
sshpkt_put(struct ssh *ssh, const void *v, size_t len)
{
  return sshbuf_put(ssh->state->outgoing_packet, v, len);
}

int
sshpkt_putb(struct ssh *ssh, const struct sshbuf *b)
{
  return sshbuf_putb(ssh->state->outgoing_packet, b);
}

int
sshpkt_put_u8(struct ssh *ssh, u_char val)
{
  return sshbuf_put_u8(ssh->state->outgoing_packet, val);
}

int
sshpkt_put_u32(struct ssh *ssh, u_int32_t val)
{
  return sshbuf_put_u32(ssh->state->outgoing_packet, val);
}

int
sshpkt_put_u64(struct ssh *ssh, u_int64_t val)
{
  return sshbuf_put_u64(ssh->state->outgoing_packet, val);
}

int
sshpkt_put_string(struct ssh *ssh, const void *v, size_t len)
{
  return sshbuf_put_string(ssh->state->outgoing_packet, v, len);
}

int
sshpkt_put_cstring(struct ssh *ssh, const void *v)
{
  return sshbuf_put_cstring(ssh->state->outgoing_packet, v);
}

int
sshpkt_put_stringb(struct ssh *ssh, const struct sshbuf *v)
{
  return sshbuf_put_stringb(ssh->state->outgoing_packet, v);
}

#ifdef WITH_OPENSSL
#ifdef OPENSSL_HAS_ECC
int
sshpkt_put_ec(struct ssh *ssh, const EC_POINT *v, const EC_GROUP *g)
{
  return sshbuf_put_ec(ssh->state->outgoing_packet, v, g);
}

int
sshpkt_put_ec_pkey(struct ssh *ssh, EVP_PKEY *pkey)
{
  return sshbuf_put_ec_pkey(ssh->state->outgoing_packet, pkey);
}
#endif /* OPENSSL_HAS_ECC */

int
sshpkt_put_bignum2(struct ssh *ssh, const BIGNUM *v)
{
  return sshbuf_put_bignum2(ssh->state->outgoing_packet, v);
}
#endif /* WITH_OPENSSL */

/* fetch data from the incoming packet */

int
sshpkt_get(struct ssh *ssh, void *valp, size_t len)
{
  return sshbuf_get(ssh->state->incoming_packet, valp, len);
}

int
sshpkt_get_u8(struct ssh *ssh, u_char *valp)
{
  return sshbuf_get_u8(ssh->state->incoming_packet, valp);
}

int
sshpkt_get_u32(struct ssh *ssh, u_int32_t *valp)
{
  return sshbuf_get_u32(ssh->state->incoming_packet, valp);
}

int
sshpkt_get_u64(struct ssh *ssh, u_int64_t *valp)
{
  return sshbuf_get_u64(ssh->state->incoming_packet, valp);
}

int
sshpkt_get_string(struct ssh *ssh, u_char **valp, size_t *lenp)
{
  return sshbuf_get_string(ssh->state->incoming_packet, valp, lenp);
}

int
sshpkt_get_string_direct(struct ssh *ssh, const u_char **valp, size_t *lenp)
{
  return sshbuf_get_string_direct(ssh->state->incoming_packet, valp, lenp);
}

int
sshpkt_peek_string_direct(struct ssh *ssh, const u_char **valp, size_t *lenp)
{
  return sshbuf_peek_string_direct(ssh->state->incoming_packet, valp, lenp);
}

int
sshpkt_get_cstring(struct ssh *ssh, char **valp, size_t *lenp)
{
  return sshbuf_get_cstring(ssh->state->incoming_packet, valp, lenp);
}

int
sshpkt_getb_froms(struct ssh *ssh, struct sshbuf **valp)
{
  return sshbuf_froms(ssh->state->incoming_packet, valp);
}

#ifdef WITH_OPENSSL
#ifdef OPENSSL_HAS_ECC
int
sshpkt_get_ec(struct ssh *ssh, EC_POINT *v, const EC_GROUP *g)
{
  return sshbuf_get_ec(ssh->state->incoming_packet, v, g);
}
#endif /* OPENSSL_HAS_ECC */

int
sshpkt_get_bignum2(struct ssh *ssh, BIGNUM **valp)
{
  return sshbuf_get_bignum2(ssh->state->incoming_packet, valp);
}
#endif /* WITH_OPENSSL */

int
sshpkt_get_end(struct ssh *ssh)
{
  if (sshbuf_len(ssh->state->incoming_packet) > 0)
    return SSH_ERR_UNEXPECTED_TRAILING_DATA;
  return 0;
}

const u_char *
sshpkt_ptr(struct ssh *ssh, size_t *lenp)
{
  if (lenp != NULL)
    *lenp = sshbuf_len(ssh->state->incoming_packet);
  return sshbuf_ptr(ssh->state->incoming_packet);
}

/* start a new packet */

int
sshpkt_start(struct ssh *ssh, u_char type)
{
  u_char buf[6]; /* u32 packet length, u8 pad len, u8 type */

  DBG(debug("packet_start[%d]", type));
  memset(buf, 0, sizeof(buf));
  buf[sizeof(buf) - 1] = type;
  sshbuf_reset(ssh->state->outgoing_packet);
  return sshbuf_put(ssh->state->outgoing_packet, buf, sizeof(buf));
}

static int
ssh_packet_send_mux(struct ssh *ssh)
{
  struct session_state *state = ssh->state;
  u_char type, *cp;
  size_t len;
  int r;

  if (ssh->kex)
    return SSH_ERR_INTERNAL_ERROR;
  len = sshbuf_len(state->outgoing_packet);
  if (len < 6)
    return SSH_ERR_INTERNAL_ERROR;
  cp = sshbuf_mutable_ptr(state->outgoing_packet);
  type = cp[5];
  if (ssh_packet_log_type(type))
    debug3_f("type %u", type);
  /* drop everything, but the connection protocol */
  if (type >= SSH2_MSG_CONNECTION_MIN &&
      type <= SSH2_MSG_CONNECTION_MAX) {
    POKE_U32(cp, len - 4);
    if ((r = sshbuf_putb(state->output,
        state->outgoing_packet)) != 0)
      return r;
    /* sshbuf_dump(state->output, stderr); */
  }
  sshbuf_reset(state->outgoing_packet);
  return 0;
}

/*
 * 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.
 */
int
sshpkt_msg_ignore(struct ssh *ssh, u_int nbytes)
{
  u_int32_t rnd = 0;
  int r;
  u_int i;

  if ((r = sshpkt_start(ssh, SSH2_MSG_IGNORE)) != 0 ||
      (r = sshpkt_put_u32(ssh, nbytes)) != 0)
    return r;
  for (i = 0; i < nbytes; i++) {
    if (i % 4 == 0)
      rnd = arc4random();
    if ((r = sshpkt_put_u8(ssh, (u_char)rnd & 0xff)) != 0)
      return r;
    rnd >>= 8;
  }
  return 0;
}

/* send it */

int
sshpkt_send(struct ssh *ssh)
{
  if (ssh->state && ssh->state->mux)
    return ssh_packet_send_mux(ssh);
  return ssh_packet_send2(ssh);
}

int
sshpkt_disconnect(struct ssh *ssh, const char *fmt,...)
{
  char buf[1024];
  va_list args;
  int r;

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

  debug2_f("sending SSH2_MSG_DISCONNECT: %s", buf);
  if ((r = sshpkt_start(ssh, SSH2_MSG_DISCONNECT)) != 0 ||
      (r = sshpkt_put_u32(ssh, SSH2_DISCONNECT_PROTOCOL_ERROR)) != 0 ||
      (r = sshpkt_put_cstring(ssh, buf)) != 0 ||
      (r = sshpkt_put_cstring(ssh, "")) != 0 ||
      (r = sshpkt_send(ssh)) != 0)
    return r;
  return 0;
}

/* roundup current message to pad bytes */
int
sshpkt_add_padding(struct ssh *ssh, u_char pad)
{
  ssh->state->extra_pad = pad;
  return 0;
}

Coverage Report

Created: 2025-06-20 06:24