Add Chacha20-Poly1305, AES128-GCM and AES256-GCM support (#93) * Add Chacha20-Poly1305 authenticated encryption * Add general AEAD approach. * Add [email protected] algo using LibTomCrypt chacha and poly1305 routines. Chacha20-Poly1305 is generally faster than AES256 on CPU w/o dedicated AES instructions, having the same key size. Compiling in will add ~5,5kB to binary size on x86-64. function old new delta chacha_crypt - 1397 +1397 _poly1305_block - 608 +608 poly1305_done - 595 +595 dropbear_chachapoly_crypt - 457 +457 .rodata 26976 27392 +416 poly1305_process - 290 +290 poly1305_init - 221 +221 chacha_setup - 218 +218 encrypt_packet 1068 1270 +202 dropbear_chachapoly_getlength - 147 +147 decrypt_packet 756 897 +141 chacha_ivctr64 - 137 +137 read_packet 543 637 +94 dropbear_chachapoly_start - 94 +94 read_kex_algos 792 880 +88 chacha_keystream - 69 +69 dropbear_mode_chachapoly - 48 +48 sshciphers 280 320 +40 dropbear_mode_none 24 48 +24 dropbear_mode_ctr 24 48 +24 dropbear_mode_cbc 24 48 +24 dropbear_chachapoly_mac - 24 +24 dropbear_chachapoly - 24 +24 gen_new_keys 848 854 +6 ------------------------------------------------------------------------------ (add/remove: 14/0 grow/shrink: 10/0 up/down: 5388/0) Total: 5388 bytes * Add AES128-GCM and AES256-GCM authenticated encryption * Add general AES-GCM mode. * Add [email protected] and [email protected] algo using LibTomCrypt gcm routines. AES-GCM is combination of AES CTR mode and GHASH, slower than AES-CTR on CPU w/o dedicated AES/GHASH instructions therefore disabled by default. Compiling in will add ~6kB to binary size on x86-64. function old new delta gcm_process - 1060 +1060 .rodata 26976 27808 +832 gcm_gf_mult - 820 +820 gcm_add_aad - 660 +660 gcm_shift_table - 512 +512 gcm_done - 471 +471 gcm_add_iv - 384 +384 gcm_init - 347 +347 dropbear_gcm_crypt - 309 +309 encrypt_packet 1068 1270 +202 decrypt_packet 756 897 +141 gcm_reset - 118 +118 read_packet 543 637 +94 read_kex_algos 792 880 +88 sshciphers 280 360 +80 gcm_mult_h - 80 +80 dropbear_gcm_start - 62 +62 dropbear_mode_gcm - 48 +48 dropbear_mode_none 24 48 +24 dropbear_mode_ctr 24 48 +24 dropbear_mode_cbc 24 48 +24 dropbear_ghash - 24 +24 dropbear_gcm_getlength - 24 +24 gen_new_keys 848 854 +6 ------------------------------------------------------------------------------ (add/remove: 14/0 grow/shrink: 10/0 up/down: 6434/0) Total: 6434 bytes

#!/bin/sh
set -e

test "$1" = 'configure' || exit 0

if test ! -e /etc/dropbear/dropbear_rsa_host_key; then
  if test -f /etc/ssh/ssh_host_rsa_key; then
    echo "Converting existing OpenSSH RSA host key to Dropbear format."
    /usr/lib/dropbear/dropbearconvert openssh dropbear \
      /etc/ssh/ssh_host_rsa_key /etc/dropbear/dropbear_rsa_host_key
  else
    echo "Generating Dropbear RSA key. Please wait."
    dropbearkey -t rsa -f /etc/dropbear/dropbear_rsa_host_key
  fi
fi
if test ! -e /etc/dropbear/dropbear_dss_host_key; then
  if test -f /etc/ssh/ssh_host_dsa_key; then
    echo "Converting existing OpenSSH RSA host key to Dropbear format."
    /usr/lib/dropbear/dropbearconvert openssh dropbear \
      /etc/ssh/ssh_host_dsa_key /etc/dropbear/dropbear_dss_host_key
  else
    echo "Generating Dropbear DSS key. Please wait."
    dropbearkey -t dss -f /etc/dropbear/dropbear_dss_host_key
  fi
fi
if test ! -s /etc/default/dropbear; then 
  # check whether OpenSSH seems to be installed.
  if test -x /usr/sbin/sshd; then
    cat <<EOT
OpenSSH appears to be installed.  Setting /etc/default/dropbear so that
Dropbear will not start by default.  Edit this file to change this behaviour.

EOT
    cat >>/etc/default/dropbear <<EOT
# disabled because OpenSSH is installed
# change to NO_START=0 to enable Dropbear
NO_START=1

EOT
  fi
  cat >>/etc/default/dropbear <<EOT
# the TCP port that Dropbear listens on
DROPBEAR_PORT=22

# any additional arguments for Dropbear
DROPBEAR_EXTRA_ARGS=

# specify an optional banner file containing a message to be
# sent to clients before they connect, such as "/etc/issue.net"
DROPBEAR_BANNER=""

# RSA hostkey file (default: /etc/dropbear/dropbear_rsa_host_key)
#DROPBEAR_RSAKEY="/etc/dropbear/dropbear_rsa_host_key"

# DSS hostkey file (default: /etc/dropbear/dropbear_dss_host_key)
#DROPBEAR_DSSKEY="/etc/dropbear/dropbear_dss_host_key"

# Receive window size - this is a tradeoff between memory and
# network performance
DROPBEAR_RECEIVE_WINDOW=65536
EOT
fi

if test -x /etc/init.d/dropbear; then
  update-rc.d dropbear defaults >/dev/null
  if test -x /usr/sbin/invoke-rc.d; then
    invoke-rc.d dropbear restart
  else
    /etc/init.d/dropbear restart
  fi
fi

if test -n "$2" && dpkg --compare-versions "$2" lt '0.50-4' &&
update-service --check dropbear 2>/dev/null; then
  update-service --remove /etc/dropbear 2>/dev/null || :
  sleep 6
  rm -rf /var/run/dropbear /var/run/dropbear.log
  update-service --add /etc/dropbear || :
fi