/src/dropbear/src/packet.c

Source
/*
 * Dropbear - a SSH2 server
 * 
 * Copyright (c) 2002,2003 Matt Johnston
 * All rights reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE. */

#include "includes.h"
#include "packet.h"
#include "session.h"
#include "dbutil.h"
#include "ssh.h"
#include "algo.h"
#include "buffer.h"
#include "kex.h"
#include "dbrandom.h"
#include "service.h"
#include "auth.h"
#include "channel.h"
#include "netio.h"
#include "runopts.h"

static int read_packet_init(void);
static void make_mac(unsigned int seqno, const struct key_context_directional * key_state,
    buffer * clear_buf, unsigned int clear_len, 
    unsigned char *output_mac);
static int checkmac(void);

/* For exact details see http://www.zlib.net/zlib_tech.html
 * 5 bytes per 16kB block, plus 6 bytes for the stream.
 * We might allocate 5 unnecessary bytes here if it's an
 * exact multiple. */
#define ZLIB_COMPRESS_EXPANSION (((RECV_MAX_PAYLOAD_LEN/16384)+1)*5 + 6)
#define ZLIB_DECOMPRESS_INCR 1024
#ifndef DISABLE_ZLIB
static buffer* buf_decompress(const buffer* buf, unsigned int len);
static void buf_compress(buffer * dest, buffer * src, unsigned int len);
#endif

/* non-blocking function writing out a current encrypted packet */
void write_packet() {

  ssize_t written;
#if defined(HAVE_WRITEV) && (defined(IOV_MAX) || defined(UIO_MAXIOV))
  /* 50 is somewhat arbitrary */
  unsigned int iov_count = 50;
  struct iovec iov[50];
#else
  int len;
  buffer* writebuf;
#endif
  
  TRACE2(("enter write_packet"))
  dropbear_assert(!isempty(&ses.writequeue));

#if defined(HAVE_WRITEV) && (defined(IOV_MAX) || defined(UIO_MAXIOV))

  packet_queue_to_iovec(&ses.writequeue, iov, &iov_count);
  /* This may return EAGAIN. The main loop sometimes
  calls write_packet() without bothering to test with select() since
  it's likely to be necessary */
#if DROPBEAR_FUZZ
  if (fuzz.fuzzing) {
    /* pretend to write one packet at a time */
    /* TODO(fuzz): randomise amount written based on the fuzz input */
    written = iov[0].iov_len;
  }
  else
#endif
  {
  written = writev(ses.sock_out, iov, iov_count);
  if (written < 0) {
    if (errno == EINTR || errno == EAGAIN) {
      TRACE2(("leave write_packet: EINTR"))
      return;
    } else {
      dropbear_exit("Error writing: %s", strerror(errno));
    }
  }
  }

  packet_queue_consume(&ses.writequeue, written);
  ses.writequeue_len -= written;

  if (written == 0) {
    ses.remoteclosed();
  }

#else /* No writev () */
#if DROPBEAR_FUZZ
  _Static_assert(0, "No fuzzing code for no-writev writes");
#endif
  /* Get the next buffer in the queue of encrypted packets to write*/
  writebuf = (buffer*)examine(&ses.writequeue);

  len = writebuf->len - writebuf->pos;
  dropbear_assert(len > 0);
  /* Try to write as much as possible */
  written = write(ses.sock_out, buf_getptr(writebuf, len), len);

  if (written < 0) {
    if (errno == EINTR || errno == EAGAIN) {
      TRACE2(("leave writepacket: EINTR"))
      return;
    } else {
      dropbear_exit("Error writing: %s", strerror(errno));
    }
  } 

  if (written == 0) {
    ses.remoteclosed();
  }

  ses.writequeue_len -= written;

  if (written == len) {
    /* We've finished with the packet, free it */
    dequeue(&ses.writequeue);
    buf_free(writebuf);
    writebuf = NULL;
  } else {
    /* More packet left to write, leave it in the queue for later */
    buf_incrpos(writebuf, written);
  }
#endif /* writev */

  TRACE2(("leave write_packet"))
}

/* Non-blocking function reading available portion of a packet into the
 * ses's buffer, decrypting the length if encrypted, decrypting the
 * full portion if possible */
void read_packet() {

  int len;
  unsigned int maxlen;
  unsigned char blocksize;

  TRACE2(("enter read_packet"))
  blocksize = ses.keys->recv.algo_crypt->blocksize;
  
  if (ses.readbuf == NULL || ses.readbuf->len < blocksize) {
    int ret;
    /* In the first blocksize of a packet */

    /* Read the first blocksize of the packet, so we can decrypt it and
     * find the length of the whole packet */
    ret = read_packet_init();

    if (ret == DROPBEAR_FAILURE) {
      /* didn't read enough to determine the length */
      TRACE2(("leave read_packet: packetinit done"))
      return;
    }
  }

  /* Attempt to read the remainder of the packet, note that there
   * mightn't be any available (EAGAIN) */
  maxlen = ses.readbuf->len - ses.readbuf->pos;
  if (maxlen == 0) {
    /* Occurs when the packet is only a single block long and has all
     * been read in read_packet_init().  Usually means that MAC is disabled
     */
    len = 0;
  } else {
    len = read(ses.sock_in, buf_getptr(ses.readbuf, maxlen), maxlen);

    if (len == 0) {
      ses.remoteclosed();
    }

    if (len < 0) {
      if (errno == EINTR || errno == EAGAIN) {
        TRACE2(("leave read_packet: EINTR or EAGAIN"))
        return;
      } else {
        dropbear_exit("Error reading: %s", strerror(errno));
      }
    }

    buf_incrpos(ses.readbuf, len);
  }

  if ((unsigned int)len == maxlen) {
    /* The whole packet has been read */
    decrypt_packet();
    /* The main select() loop process_packet() to
     * handle the packet contents... */
  }
  TRACE2(("leave read_packet"))
}

/* Function used to read the initial portion of a packet, and determine the
 * length. Only called during the first BLOCKSIZE of a packet. */
/* Returns DROPBEAR_SUCCESS if the length is determined, 
 * DROPBEAR_FAILURE otherwise */
static int read_packet_init() {

  unsigned int maxlen;
  int slen;
  unsigned int len, plen;
  unsigned int blocksize;
  unsigned int macsize;


  blocksize = ses.keys->recv.algo_crypt->blocksize;
  macsize = ses.keys->recv.algo_mac->hashsize;

  if (ses.readbuf == NULL) {
    /* start of a new packet */
    ses.readbuf = buf_new(INIT_READBUF);
  }

  maxlen = blocksize - ses.readbuf->pos;
      
  /* read the rest of the packet if possible */
  slen = read(ses.sock_in, buf_getwriteptr(ses.readbuf, maxlen),
      maxlen);
  if (slen == 0) {
    ses.remoteclosed();
  }
  if (slen < 0) {
    if (errno == EINTR || errno == EAGAIN) {
      TRACE2(("leave read_packet_init: EINTR"))
      return DROPBEAR_FAILURE;
    }
    dropbear_exit("Error reading: %s", strerror(errno));
  }

  buf_incrwritepos(ses.readbuf, slen);

  if ((unsigned int)slen != maxlen) {
    /* don't have enough bytes to determine length, get next time */
    return DROPBEAR_FAILURE;
  }

  /* now we have the first block, need to get packet length, so we decrypt
   * the first block (only need first 4 bytes) */
  buf_setpos(ses.readbuf, 0);
#if DROPBEAR_AEAD_MODE
  if (ses.keys->recv.crypt_mode->aead_crypt) {
    if (ses.keys->recv.crypt_mode->aead_getlength(ses.recvseq,
          buf_getptr(ses.readbuf, blocksize), &plen,
          blocksize,
          &ses.keys->recv.cipher_state) != CRYPT_OK) {
      dropbear_exit("Error decrypting");
    }
    len = plen + 4 + macsize;
  } else
#endif
  {
    if (ses.keys->recv.crypt_mode->decrypt(buf_getptr(ses.readbuf, blocksize), 
          buf_getwriteptr(ses.readbuf, blocksize),
          blocksize,
          &ses.keys->recv.cipher_state) != CRYPT_OK) {
      dropbear_exit("Error decrypting");
    }
    plen = buf_getint(ses.readbuf) + 4;
    len = plen + macsize;
  }

  TRACE2(("packet size is %u, block %u mac %u", len, blocksize, macsize))


  /* check packet length */
  if ((len > RECV_MAX_PACKET_LEN) ||
    (plen < blocksize) ||
    (plen % blocksize != 0)) {
    dropbear_exit("Integrity error (bad packet size %u)", len);
  }

  if (len > ses.readbuf->size) {
    ses.readbuf = buf_resize(ses.readbuf, len);   
  }
  buf_setlen(ses.readbuf, len);
  buf_setpos(ses.readbuf, blocksize);
  return DROPBEAR_SUCCESS;
}

/* handle the received packet */
void decrypt_packet() {

  unsigned char blocksize;
  unsigned char macsize;
  unsigned int padlen;
  unsigned int len;

  TRACE2(("enter decrypt_packet"))
  blocksize = ses.keys->recv.algo_crypt->blocksize;
  macsize = ses.keys->recv.algo_mac->hashsize;

  ses.kexstate.datarecv += ses.readbuf->len;

#if DROPBEAR_AEAD_MODE
  if (ses.keys->recv.crypt_mode->aead_crypt) {
    /* first blocksize is not decrypted yet */
    buf_setpos(ses.readbuf, 0);

    /* decrypt it in-place */
    len = ses.readbuf->len - macsize - ses.readbuf->pos;
    if (ses.keys->recv.crypt_mode->aead_crypt(ses.recvseq,
          buf_getptr(ses.readbuf, len + macsize),
          buf_getwriteptr(ses.readbuf, len),
          len, macsize,
          &ses.keys->recv.cipher_state, LTC_DECRYPT) != CRYPT_OK) {
      dropbear_exit("Error decrypting");
    }
    buf_incrpos(ses.readbuf, len);
  } else
#endif
  {
    /* we've already decrypted the first blocksize in read_packet_init */
    buf_setpos(ses.readbuf, blocksize);

    /* decrypt it in-place */
    len = ses.readbuf->len - macsize - ses.readbuf->pos;
    if (ses.keys->recv.crypt_mode->decrypt(
          buf_getptr(ses.readbuf, len), 
          buf_getwriteptr(ses.readbuf, len),
          len,
          &ses.keys->recv.cipher_state) != CRYPT_OK) {
      dropbear_exit("Error decrypting");
    }
    buf_incrpos(ses.readbuf, len);

    /* check the hmac */
    if (checkmac() != DROPBEAR_SUCCESS) {
      dropbear_exit("Integrity error");
    }

  }
  
#if DROPBEAR_FUZZ
  fuzz_dump(ses.readbuf->data, ses.readbuf->len);
#endif

  /* get padding length */
  buf_setpos(ses.readbuf, PACKET_PADDING_OFF);
  padlen = buf_getbyte(ses.readbuf);
    
  /* payload length */
  /* - 4 - 1 is for LEN and PADLEN values */
  len = ses.readbuf->len - padlen - 4 - 1 - macsize;
  if ((len > RECV_MAX_PAYLOAD_LEN+ZLIB_COMPRESS_EXPANSION) || (len < 1)) {
    dropbear_exit("Bad packet size %u", len);
  }

  buf_setpos(ses.readbuf, PACKET_PAYLOAD_OFF);

#ifndef DISABLE_ZLIB
  if (is_compress_recv()) {
    /* decompress */
    ses.payload = buf_decompress(ses.readbuf, len);
    buf_setpos(ses.payload, 0);
    ses.payload_beginning = 0;
    buf_free(ses.readbuf);
  } else 
#endif
  {
    ses.payload = ses.readbuf;
    ses.payload_beginning = ses.payload->pos;
    buf_setlen(ses.payload, ses.payload->pos + len);
  }
  ses.readbuf = NULL;

  ses.recvseq++;

  TRACE2(("leave decrypt_packet"))
}

/* Checks the mac at the end of a decrypted readbuf.
 * Returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
static int checkmac() {

  unsigned char mac_bytes[MAX_MAC_LEN];
  unsigned int mac_size, contents_len;
  
  mac_size = ses.keys->recv.algo_mac->hashsize;
  contents_len = ses.readbuf->len - mac_size;

  buf_setpos(ses.readbuf, 0);
  make_mac(ses.recvseq, &ses.keys->recv, ses.readbuf, contents_len, mac_bytes);

#if DROPBEAR_FUZZ
  if (fuzz.fuzzing) {
    /* fail 1 in 2000 times to test error path. */
    unsigned int value = 0;
    if (mac_size > sizeof(value)) {
      memcpy(&value, mac_bytes, sizeof(value));
    }
    if (value % 2000 == 99) {
      return DROPBEAR_FAILURE;
    }
    return DROPBEAR_SUCCESS;
  }
#endif

  /* compare the hash */
  buf_setpos(ses.readbuf, contents_len);
  if (constant_time_memcmp(mac_bytes, buf_getptr(ses.readbuf, mac_size), mac_size) != 0) {
    return DROPBEAR_FAILURE;
  } else {
    return DROPBEAR_SUCCESS;
  }
}

#ifndef DISABLE_ZLIB
/* returns a pointer to a newly created buffer */
static buffer* buf_decompress(const buffer* buf, unsigned int len) {

  int result;
  buffer * ret;
  z_streamp zstream;

  zstream = ses.keys->recv.zstream;
  /* We use RECV_MAX_PAYLOAD_LEN+1 here to ensure that
     we can detect an oversized payload after inflate() */
  ret = buf_new(RECV_MAX_PAYLOAD_LEN+1);

  zstream->avail_in = len;
  zstream->next_in = buf_getptr(buf, len);
  zstream->avail_out = ret->size;
  zstream->next_out = ret->data;

  result = inflate(zstream, Z_SYNC_FLUSH);
  if (result != Z_OK) {
    dropbear_exit("zlib error");
  }

  buf_setlen(ret, ret->size - zstream->avail_out);

  if (zstream->avail_in > 0 || ret->len > RECV_MAX_PAYLOAD_LEN) {
    /* The remote side sent larger than a payload size
     * of uncompressed data.
     */
    dropbear_exit("bad packet, oversized decompressed");
  }

  /* Success. All input was consumed and avail_out > 0 */
  return ret;

}
#endif


/* returns 1 if the packet is a valid type during kex (see 7.1 of rfc4253) */
static int packet_is_okay_kex(unsigned char type) {
  if (type >= SSH_MSG_USERAUTH_REQUEST) {
    return 0;
  }
  if (type == SSH_MSG_SERVICE_REQUEST || type == SSH_MSG_SERVICE_ACCEPT) {
    return 0;
  }
  if (type == SSH_MSG_KEXINIT) {
    /* XXX should this die horribly if !dataallowed ?? */
    return 0;
  }
  return 1;
}

static void enqueue_reply_packet() {
  struct packetlist * new_item = NULL;
  new_item = m_malloc(sizeof(struct packetlist));
  new_item->next = NULL;
  
  new_item->payload = buf_newcopy(ses.writepayload);
  buf_setpos(ses.writepayload, 0);
  buf_setlen(ses.writepayload, 0);
  
  if (ses.reply_queue_tail) {
    ses.reply_queue_tail->next = new_item;
  } else {
    ses.reply_queue_head = new_item;
  }
  ses.reply_queue_tail = new_item;
}

void maybe_flush_reply_queue() {
  struct packetlist *tmp_item = NULL, *curr_item = NULL;
  if (!ses.dataallowed)
  {
    TRACE(("maybe_empty_reply_queue - no data allowed"))
    return;
  }
    
  for (curr_item = ses.reply_queue_head; curr_item; ) {
    CHECKCLEARTOWRITE();
    buf_putbytes(ses.writepayload,
      curr_item->payload->data, curr_item->payload->len);
      
    buf_free(curr_item->payload);
    tmp_item = curr_item;
    curr_item = curr_item->next;
    m_free(tmp_item);
    encrypt_packet();
  }
  ses.reply_queue_head = ses.reply_queue_tail = NULL;
}
  
/* encrypt the writepayload, putting into writebuf, ready for write_packet()
 * to put on the wire */
void encrypt_packet() {

  unsigned char padlen;
  unsigned char blocksize, mac_size;
  buffer * writebuf; /* the packet which will go on the wire. This is 
                        encrypted in-place. */
  unsigned char packet_type;
  unsigned int len, encrypt_buf_size;
  unsigned char mac_bytes[MAX_MAC_LEN];

  time_t now;
  
  TRACE2(("enter encrypt_packet()"))

  buf_setpos(ses.writepayload, 0);
  packet_type = buf_getbyte(ses.writepayload);
  buf_setpos(ses.writepayload, 0);

  TRACE2(("encrypt_packet type is %d", packet_type))
  
  if ((!ses.dataallowed && !packet_is_okay_kex(packet_type))) {
    /* During key exchange only particular packets are allowed.
      Since this packet_type isn't OK we just enqueue it to send 
      after the KEX, see maybe_flush_reply_queue */
    enqueue_reply_packet();
    return;
  }
    
  blocksize = ses.keys->trans.algo_crypt->blocksize;
  mac_size = ses.keys->trans.algo_mac->hashsize;

  /* Encrypted packet len is payload+5. We need to then make sure
   * there is enough space for padding or MIN_PACKET_LEN. 
   * Add extra 3 since we need at least 4 bytes of padding */
  encrypt_buf_size = (ses.writepayload->len+4+1) 
    + MAX(MIN_PACKET_LEN, blocksize) + 3
  /* add space for the MAC at the end */
        + mac_size
#ifndef DISABLE_ZLIB
  /* some extra in case 'compression' makes it larger */
        + ZLIB_COMPRESS_EXPANSION
#endif
  /* and an extra cleartext (stripped before transmission) byte for the
   * packet type */
        + 1;

  writebuf = buf_new(encrypt_buf_size);
  buf_setlen(writebuf, PACKET_PAYLOAD_OFF);
  buf_setpos(writebuf, PACKET_PAYLOAD_OFF);

#ifndef DISABLE_ZLIB
  /* compression */
  if (is_compress_trans()) {
    buf_compress(writebuf, ses.writepayload, ses.writepayload->len);
  } else
#endif
  {
    memcpy(buf_getwriteptr(writebuf, ses.writepayload->len),
        buf_getptr(ses.writepayload, ses.writepayload->len),
        ses.writepayload->len);
    buf_incrwritepos(writebuf, ses.writepayload->len);
  }

  /* finished with payload */
  buf_setpos(ses.writepayload, 0);
  buf_setlen(ses.writepayload, 0);

  /* length of padding - packet length excluding the packetlength uint32
   * field in aead mode must be a multiple of blocksize, with a minimum of
   * 4 bytes of padding */
  len = writebuf->len;
#if DROPBEAR_AEAD_MODE
  if (ses.keys->trans.crypt_mode->aead_crypt) {
    len -= 4;
  }
#endif
  padlen = blocksize - len % blocksize;
  if (padlen < 4) {
    padlen += blocksize;
  }
  /* check for min packet length */
  if (writebuf->len + padlen < MIN_PACKET_LEN) {
    padlen += blocksize;
  }

  buf_setpos(writebuf, 0);
  /* packet length excluding the packetlength uint32 */
  buf_putint(writebuf, writebuf->len + padlen - 4);

  /* padding len */
  buf_putbyte(writebuf, padlen);
  /* actual padding */
  buf_setpos(writebuf, writebuf->len);
  buf_incrlen(writebuf, padlen);
  genrandom(buf_getptr(writebuf, padlen), padlen);

#if DROPBEAR_AEAD_MODE
  if (ses.keys->trans.crypt_mode->aead_crypt) {
    /* do the actual encryption, in-place */
    buf_setpos(writebuf, 0);
    /* encrypt it in-place*/
    len = writebuf->len;
    buf_incrlen(writebuf, mac_size);
    if (ses.keys->trans.crypt_mode->aead_crypt(ses.transseq,
          buf_getptr(writebuf, len),
          buf_getwriteptr(writebuf, len + mac_size),
          len, mac_size,
          &ses.keys->trans.cipher_state, LTC_ENCRYPT) != CRYPT_OK) {
      dropbear_exit("Error encrypting");
    }
    buf_incrpos(writebuf, len + mac_size);
  } else
#endif
  {
    make_mac(ses.transseq, &ses.keys->trans, writebuf, writebuf->len, mac_bytes);

    /* do the actual encryption, in-place */
    buf_setpos(writebuf, 0);
    /* encrypt it in-place*/
    len = writebuf->len;
    if (ses.keys->trans.crypt_mode->encrypt(
          buf_getptr(writebuf, len),
          buf_getwriteptr(writebuf, len),
          len,
          &ses.keys->trans.cipher_state) != CRYPT_OK) {
      dropbear_exit("Error encrypting");
    }
    buf_incrpos(writebuf, len);

    /* stick the MAC on it */
    buf_putbytes(writebuf, mac_bytes, mac_size);
  }

  /* Update counts */
  ses.kexstate.datatrans += writebuf->len;

  writebuf_enqueue(writebuf);

  /* Update counts */
  ses.transseq++;

  now = monotonic_now();
  ses.last_packet_time_any_sent = now;
  /* idle timeout shouldn't be affected by responses to keepalives.
  send_msg_keepalive() itself also does tricks with 
  ses.last_packet_idle_time - read that if modifying this code */
  if (packet_type != SSH_MSG_REQUEST_FAILURE
    && packet_type != SSH_MSG_UNIMPLEMENTED
    && packet_type != SSH_MSG_IGNORE) {
    ses.last_packet_time_idle = now;

  }

  TRACE2(("leave encrypt_packet()"))
}

void writebuf_enqueue(buffer * writebuf) {
  /* enqueue the packet for sending. It will get freed after transmission. */
  buf_setpos(writebuf, 0);
  enqueue(&ses.writequeue, (void*)writebuf);
  ses.writequeue_len += writebuf->len;
}


/* Create the packet mac, and append H(seqno|clearbuf) to the output */
/* output_mac must have ses.keys->trans.algo_mac->hashsize bytes. */
static void make_mac(unsigned int seqno, const struct key_context_directional * key_state,
    buffer * clear_buf, unsigned int clear_len, 
    unsigned char *output_mac) {
  unsigned char seqbuf[4];
  unsigned long bufsize;
  hmac_state hmac;

  if (key_state->algo_mac->hashsize > 0) {
    /* calculate the mac */
    if (hmac_init(&hmac, 
          key_state->hash_index,
          key_state->mackey,
          key_state->algo_mac->keysize) != CRYPT_OK) {
      dropbear_exit("HMAC error");
    }
  
    /* sequence number */
    STORE32H(seqno, seqbuf);
    if (hmac_process(&hmac, seqbuf, 4) != CRYPT_OK) {
      dropbear_exit("HMAC error");
    }
  
    /* the actual contents */
    buf_setpos(clear_buf, 0);
    if (hmac_process(&hmac, 
          buf_getptr(clear_buf, clear_len),
          clear_len) != CRYPT_OK) {
      dropbear_exit("HMAC error");
    }
  
    bufsize = MAX_MAC_LEN;
    if (hmac_done(&hmac, output_mac, &bufsize) != CRYPT_OK) {
      dropbear_exit("HMAC error");
    }
  }
  TRACE2(("leave writemac"))
}

#ifndef DISABLE_ZLIB
/* compresses len bytes from src, outputting to dest (starting from the
 * respective current positions. dest must have sufficient space,
 * len+ZLIB_COMPRESS_EXPANSION */
static void buf_compress(buffer * dest, buffer * src, unsigned int len) {

  unsigned int endpos = src->pos + len;
  int result;

  TRACE2(("enter buf_compress"))

  dropbear_assert(dest->size - dest->pos >= len+ZLIB_COMPRESS_EXPANSION);

  ses.keys->trans.zstream->avail_in = endpos - src->pos;
  ses.keys->trans.zstream->next_in = 
    buf_getptr(src, ses.keys->trans.zstream->avail_in);

  ses.keys->trans.zstream->avail_out = dest->size - dest->pos;
  ses.keys->trans.zstream->next_out =
    buf_getwriteptr(dest, ses.keys->trans.zstream->avail_out);

  result = deflate(ses.keys->trans.zstream, Z_SYNC_FLUSH);

  buf_setpos(src, endpos - ses.keys->trans.zstream->avail_in);
  buf_setlen(dest, dest->size - ses.keys->trans.zstream->avail_out);
  buf_setpos(dest, dest->len);

  if (result != Z_OK) {
    dropbear_exit("zlib error");
  }

  /* fails if destination buffer wasn't large enough */
  dropbear_assert(ses.keys->trans.zstream->avail_in == 0);
  TRACE2(("leave buf_compress"))
}
#endif

Coverage Report

Created: 2025-11-13 06:08