dyndnssh-shell

#!/bin/sh

re_match() {
  echo "$2" | egrep "$1" > /dev/null
  return $?
}

part() {
  echo "$2" | cut -d " " -f "$1"
}

log() {
  echo "$@" | ./dyndnssh-log
}

logf() {
  printf "$@" | ./dyndnssh-log
}

hostname_re="([A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9-]*[A-Za-z0-9])"
ip4_re='(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])'
ip6_re='([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)'

if test -z "$SSH_CONNECTION"; then
  echo "\$SSH_CONNECTION not set"
  exit 1
fi
ssh_address="$(part 1 "$SSH_CONNECTION")"

if test $# -ne 2 -o "$1" != "-c"; then
  echo "interactive login not permitted"
  logf "%s: attempted interactive login\n" "$ssh_address"
  exit 1
fi
request="$2"

if re_match "^$hostname_re\$" "$request"; then # no address supplied, use SSH_CONNECTION
  hostname="$request"
  address="$ssh_address"
  logf "%s: implicit request for hostname: %s\n" "$ssh_address" "$hostname"
elif re_match "^$hostname_re ($ip4_re)|($ip6_re)$" "$request"; then # explicit address supplied in request
  hostname="$(part 1 "$request")"
  address="$(part 2 "$request")"
  logf "%s: explicit request for hostname: %s, address: %s\n" "$ssh_address" "$hostname" "$address"
else # malformed request
  echo "malformed request, should be \"HOSTNAME\" or \"HOSTNAME ADDRESS\""
  logf "%s: malformed request \"%s\"\n" "$ssh_address" "$request"
  exit 1
fi

if test -z "$DYNDNSSH_ALLOWED_HOSTNAMES" || \
    re_match ":$hostname:" ":$DYNDNSSH_ALLOWED_HOSTNAMES:"; then # user has permission for this hostname
  if re_match "^$ip4_re\$" "$address"; then
    echo "$address" > db/ip4/$hostname
  elif re_match "^$ip6_re\$" "$address"; then
    echo "$address" > db/ip6/$hostname
  else
    echo "malformed address"
    logf "%s: malformed address \"%s\"\n" "$ssh_address" "$address"
    exit 1
  fi
else
  echo "permission denied"
  logf "%s: permission denied\n" "$ssh_address"
  exit 1
fi

if test -x dyndnssh-bridge; then
  exec ./dyndnssh-bridge
fi