ssh-copy-id

#!/bin/sh

# Copyright (c) 1999-2020 Philip Hands <phil@hands.com>
#               2020 Matthias Blümel <blaimi@blaimi.de>
#               2017 Sebastien Boyron <seb@boyron.eu>
#               2013 Martin Kletzander <mkletzan@redhat.com>
#               2010 Adeodato =?iso-8859-1?Q?Sim=F3?= <asp16@alu.ua.es>
#               2010 Eric Moret <eric.moret@gmail.com>
#               2009 Xr <xr@i-jeuxvideo.com>
#               2007 Justin Pryzby <justinpryzby@users.sourceforge.net>
#               2004 Reini Urban <rurban@x-ray.at>
#               2003 Colin Watson <cjwatson@debian.org>
# 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.

# Shell script to install your public key(s) on a remote machine
# See the ssh-copy-id(1) man page for details

# shellcheck shell=dash

# check that we have something mildly sane as our shell, or try to find something better
if false ^ printf "%s: WARNING: ancient shell, hunting for a more modern one... " "$0"
then
  SANE_SH=${SANE_SH:-/usr/bin/ksh}
  if printf 'true ^ false\n' | "$SANE_SH"
  then
    printf "'%s' seems viable.\\n" "$SANE_SH"
    exec "$SANE_SH" "$0" "$@"
  else
    cat <<-EOF
	oh dear.

	  If you have a more recent shell available, that supports \$(...) etc.
	  please try setting the environment variable SANE_SH to the path of that
	  shell, and then retry running this script. If that works, please report
	  a bug describing your setup, and the shell you used to make it work.

	EOF
    printf '%s: ERROR: Less dimwitted shell required.\n' "$0"
    exit 1
  fi
fi

# shellcheck disable=SC2010
DEFAULT_PUB_ID_FILE=$(ls -t "${HOME}"/.ssh/id*.pub 2>/dev/null | grep -v -- '-cert.pub$' | head -n 1)
SSH="ssh -a -x"
umask 0177

usage () {
  printf 'Usage: %s [-h|-?|-f|-n|-s] [-i [identity_file]] [-p port] [-F alternative ssh_config file] [[-o <ssh -o options>] ...] [user@]hostname\n' "$0" >&2
  printf '\t-f: force mode -- copy keys without trying to check if they are already installed\n' >&2
  printf '\t-n: dry run    -- no keys are actually copied\n' >&2
  printf '\t-s: use sftp   -- use sftp instead of executing remote-commands. Can be useful if the remote only allows sftp\n' >&2
  printf '\t-h|-?: print this help\n' >&2
  exit 1
}

# escape any single quotes in an argument
quote() {
  printf '%s\n' "$1" | sed -e "s/'/'\\\\''/g"
}

use_id_file() {
  L_ID_FILE="$1"

  if [ -z "$L_ID_FILE" ] ; then
    printf '%s: ERROR: no ID file found\n' "$0"
    exit 1
  fi

  if expr "$L_ID_FILE" : '.*\.pub$' >/dev/null ; then
    PUB_ID_FILE="$L_ID_FILE"
  else
    PUB_ID_FILE="$L_ID_FILE.pub"
  fi

  [ "$FORCED" ] || PRIV_ID_FILE=$(dirname "$PUB_ID_FILE")/$(basename "$PUB_ID_FILE" .pub)

  # check that the files are readable
  for f in "$PUB_ID_FILE" ${PRIV_ID_FILE:+"$PRIV_ID_FILE"} ; do
    ErrMSG=$( { : < "$f" ; } 2>&1 ) || {
      L_PRIVMSG=""
      [ "$f" = "$PRIV_ID_FILE" ] && L_PRIVMSG="	(to install the contents of '$PUB_ID_FILE' anyway, look at the -f option)"
      printf "\\n%s: ERROR: failed to open ID file '%s': %s\\n" "$0" "$f" "$(printf '%s\n%s\n' "$ErrMSG" "$L_PRIVMSG" | sed -e 's/.*: *//')"
      exit 1
    }
  done
  printf '%s: INFO: Source of key(s) to be installed: "%s"\n' "$0" "$PUB_ID_FILE" >&2
  GET_ID="cat \"$PUB_ID_FILE\""
}

if [ -n "$SSH_AUTH_SOCK" ] && ssh-add -L >/dev/null 2>&1 ; then
  GET_ID="ssh-add -L"
fi

while getopts "i:o:p:F:fnsh?" OPT
do
  case "$OPT" in
    i)
      [ "${SEEN_OPT_I}" ] && {
        printf '\n%s: ERROR: -i option must not be specified more than once\n\n' "$0"
        usage
      }
      SEEN_OPT_I="yes"
      use_id_file "${OPTARG:-$DEFAULT_PUB_ID_FILE}"
      ;;
    o|p|F)
      SSH_OPTS="${SSH_OPTS:+$SSH_OPTS }-$OPT '$(quote "${OPTARG}")'"
      ;;
    f)
      FORCED=1
      ;;
    n)
      DRY_RUN=1
      ;;
    s)
      SFTP=sftp
      ;;
    h|\?)
      usage
      ;;
  esac
done 
#shift all args to keep only USER_HOST
shift $((OPTIND-1))

if [ $# = 0 ] ; then
  usage
fi
if [ $# != 1 ] ; then
  printf '%s: ERROR: Too many arguments.  Expecting a target hostname, got: %s\n\n' "$0" "$SAVEARGS" >&2
  usage
fi

# drop trailing colon
USER_HOST="$*"
# tack the hostname onto SSH_OPTS
SSH_OPTS="${SSH_OPTS:+$SSH_OPTS }'$(quote "$USER_HOST")'"
# and populate "$@" for later use (only way to get proper quoting of options)
eval set -- "$SSH_OPTS"

# shellcheck disable=SC2086
if [ -z "$(eval $GET_ID)" ] && [ -r "${PUB_ID_FILE:=$DEFAULT_PUB_ID_FILE}" ] ; then
  use_id_file "$PUB_ID_FILE"
fi

# shellcheck disable=SC2086
if [ -z "$(eval $GET_ID)" ] ; then
  printf '%s: ERROR: No identities found\n' "$0" >&2
  exit 1
fi

# filter_ids()
# tries to log in using the keys piped to it, and filters out any that work
filter_ids() {
  L_SUCCESS="$1"
  L_TMP_ID_FILE="$SCRATCH_DIR"/popids_tmp_id
  L_OUTPUT_FILE="$SCRATCH_DIR"/popids_output

  # repopulate "$@" inside this function
  eval set -- "$SSH_OPTS"

  while read -r ID || [ "$ID" ] ; do
    printf '%s\n' "$ID" > "$L_TMP_ID_FILE"

    # the next line assumes $PRIV_ID_FILE only set if using a single id file - this
    # assumption will break if we implement the possibility of multiple -i options.
    # The point being that if file based, ssh needs the private key, which it cannot
    # find if only given the contents of the .pub file in an unrelated tmpfile
    $SSH -i "${PRIV_ID_FILE:-$L_TMP_ID_FILE}" \
      -o ControlPath=none \
      -o LogLevel=INFO \
      -o PreferredAuthentications=publickey \
      -o IdentitiesOnly=yes "$@" exit >"$L_OUTPUT_FILE" 2>&1 </dev/null
    if [ "$?" = "$L_SUCCESS" ] || {
         [ "$SFTP" ] && grep 'allows sftp connections only' "$L_OUTPUT_FILE" >/dev/null
         # this error counts as a success if we're setting up an sftp connection
       }
    then
      : > "$L_TMP_ID_FILE"
    else
      grep 'Permission denied' "$L_OUTPUT_FILE" >/dev/null || {
        sed -e 's/^/ERROR: /' <"$L_OUTPUT_FILE" >"$L_TMP_ID_FILE"
        cat >/dev/null #consume the other keys, causing loop to end
      }
    fi

    cat "$L_TMP_ID_FILE"
  done
}

# populate_new_ids() uses several global variables ($USER_HOST, $SSH_OPTS ...)
# and has the side effect of setting $NEW_IDS
populate_new_ids() {
  if [ "$FORCED" ] ; then
    # shellcheck disable=SC2086
    NEW_IDS=$(eval $GET_ID)
    return
  fi

  printf '%s: INFO: attempting to log in with the new key(s), to filter out any that are already installed\n' "$0" >&2
  # shellcheck disable=SC2086
  NEW_IDS=$(eval $GET_ID | filter_ids $1)

  if expr "$NEW_IDS" : "^ERROR: " >/dev/null ; then
    printf '\n%s: %s\n\n' "$0" "$NEW_IDS" >&2
    exit 1
  fi
  if [ -z "$NEW_IDS" ] ; then
    printf '\n%s: WARNING: All keys were skipped because they already exist on the remote system.\n' "$0" >&2
    printf '\t\t(if you think this is a mistake, you may want to use -f option)\n\n' >&2
    exit 0
  fi
  printf '%s: INFO: %d key(s) remain to be installed -- if you are prompted now it is to install the new keys\n' "$0" "$(printf '%s\n' "$NEW_IDS" | wc -l)" >&2
}

# installkey_sh [target_path]
#    produce a one-liner to add the keys to remote authorized_keys file
#    optionally takes an alternative path for authorized_keys
installkeys_sh() {
  AUTH_KEY_FILE=${1:-.ssh/authorized_keys}
  AUTH_KEY_DIR=$(dirname "${AUTH_KEY_FILE}")

  # In setting INSTALLKEYS_SH:
  #    the tr puts it all on one line (to placate tcsh)
  #      (hence the excessive use of semi-colons (;) )
  # then in the command:
  #    cd to be at $HOME, just in case;
  #    the -z `tail ...` checks for a trailing newline. The echo adds one if was missing
  #    the cat adds the keys we're getting via STDIN
  #    and if available restorecon is used to restore the SELinux context
  INSTALLKEYS_SH=$(tr '\t\n' ' ' <<-EOF
	cd;
	umask 077;
	mkdir -p "${AUTH_KEY_DIR}" &&
		{ [ -z \`tail -1c ${AUTH_KEY_FILE} 2>/dev/null\` ] ||
			echo >> "${AUTH_KEY_FILE}" || exit 1; } &&
		cat >> "${AUTH_KEY_FILE}" || exit 1;
	if type restorecon >/dev/null 2>&1; then
		restorecon -F "${AUTH_KEY_DIR}" "${AUTH_KEY_FILE}";
	fi
	EOF
  )

  # to defend against quirky remote shells: use 'exec sh -c' to get POSIX;
  printf "exec sh -c '%s'" "${INSTALLKEYS_SH}"
}

#shellcheck disable=SC2120 # the 'eval set' confuses this
installkeys_via_sftp() {

  # repopulate "$@" inside this function
  eval set -- "$SSH_OPTS"

  L_KEYS=$SCRATCH_DIR/authorized_keys
  L_SHARED_CON=$SCRATCH_DIR/master-conn
  $SSH -f -N -M -S "$L_SHARED_CON" "$@"
  L_CLEANUP="$SSH -S $L_SHARED_CON -O exit 'ignored' >/dev/null 2>&1 ; $SCRATCH_CLEANUP"
  #shellcheck disable=SC2064
  trap "$L_CLEANUP" EXIT TERM INT QUIT
  sftp -b - -o "ControlPath=$L_SHARED_CON" "ignored" <<-EOF || return 1
	-get .ssh/authorized_keys $L_KEYS
	EOF
  # add a newline or create file if it's missing, same like above
  [ -z "$(tail -1c "$L_KEYS" 2>/dev/null)" ] || echo >> "$L_KEYS"
  # append the keys being piped in here
  cat >> "$L_KEYS"
  sftp -b - -o "ControlPath=$L_SHARED_CON" "ignored" <<-EOF || return 1
	-mkdir .ssh
	chmod 700 .ssh
	put $L_KEYS .ssh/authorized_keys
	chmod 600 .ssh/authorized_keys
	EOF
  #shellcheck disable=SC2064
  eval "$L_CLEANUP" && trap "$SCRATCH_CLEANUP" EXIT TERM INT QUIT
}


# create a scratch dir for any temporary files needed
if SCRATCH_DIR=$(mktemp -d ~/.ssh/ssh-copy-id.XXXXXXXXXX) &&
    [ "$SCRATCH_DIR" ] && [ -d "$SCRATCH_DIR" ]
then
  chmod 0700 "$SCRATCH_DIR"
  SCRATCH_CLEANUP="rm -rf \"$SCRATCH_DIR\""
  #shellcheck disable=SC2064
  trap "$SCRATCH_CLEANUP" EXIT TERM INT QUIT
else
  printf '%s: ERROR: failed to create required temporary directory under ~/.ssh\n' "$0" >&2
  exit 1
fi

REMOTE_VERSION=$($SSH -v -o PreferredAuthentications=',' -o ControlPath=none "$@" 2>&1 |
                 sed -ne 's/.*remote software version //p')

# shellcheck disable=SC2029
case "$REMOTE_VERSION" in
  NetScreen*)
    populate_new_ids 1
    for KEY in $(printf "%s" "$NEW_IDS" | cut -d' ' -f2) ; do
      KEY_NO=$((KEY_NO + 1))
      printf '%s\n' "$KEY" | grep ssh-dss >/dev/null || {
         printf '%s: WARNING: Non-dsa key (#%d) skipped (NetScreen only supports DSA keys)\n' "$0" "$KEY_NO" >&2
         continue
      }
      [ "$DRY_RUN" ] || printf 'set ssh pka-dsa key %s\nsave\nexit\n' "$KEY" | $SSH -T "$@" >/dev/null 2>&1
      if [ $? = 255 ] ; then
        printf '%s: ERROR: installation of key #%d failed (please report a bug describing what caused this, so that we can make this message useful)\n' "$0" "$KEY_NO" >&2
      else
        ADDED=$((ADDED + 1))
      fi
    done
    if [ -z "$ADDED" ] ; then
      exit 1
    fi
    ;;
  dropbear*)
    populate_new_ids 0
    [ "$DRY_RUN" ] || printf '%s\n' "$NEW_IDS" | \
      $SSH "$@" "$(installkeys_sh /etc/dropbear/authorized_keys)" \
      || exit 1
    ADDED=$(printf '%s\n' "$NEW_IDS" | wc -l)
    ;;
  *)
    # Assuming that the remote host treats ~/.ssh/authorized_keys as one might expect
    populate_new_ids 0
    if ! [ "$DRY_RUN" ] ; then
      printf '%s\n' "$NEW_IDS" | \
        if [ "$SFTP" ] ; then
          #shellcheck disable=SC2119
          installkeys_via_sftp
        else
          $SSH "$@" "$(installkeys_sh)"
        fi || exit 1
    fi
    ADDED=$(printf '%s\n' "$NEW_IDS" | wc -l)
    ;;
esac

if [ "$DRY_RUN" ] ; then
  cat <<-EOF
	=-=-=-=-=-=-=-=
	Would have added the following key(s):

	$NEW_IDS
	=-=-=-=-=-=-=-=
	EOF
else
  cat <<-EOF

	Number of key(s) added: $ADDED

	Now try logging into the machine, with:   "${SFTP:-ssh} $SSH_OPTS"
	and check to make sure that only the key(s) you wanted were added.

	EOF
fi

# =-=-=-=