-#!/bin/bash
+#!/usr/bin/env bash
# monkeysphere-ssh-proxycommand: MonkeySphere ssh ProxyCommand hook
#
# established. Can be added to ~/.ssh/config as follows:
# ProxyCommand monkeysphere-ssh-proxycommand %h %p
+########################################################################
+PGRM=$(basename $0)
+
+SYSSHAREDIR=${MONKEYSPHERE_SYSSHAREDIR:-"/usr/share/monkeysphere"}
+export SYSSHAREDIR
+. "${SYSSHAREDIR}/common" || exit 1
+
+########################################################################
+# FUNCTIONS
########################################################################
usage() {
-cat <<EOF >&2
+ cat <<EOF >&2
usage: ssh -o ProxyCommand="$(basename $0) %h %p" ...
EOF
}
+log() {
+ echo "$@" >&2
+}
+
+output_no_valid_key() {
+ local sshKeyOffered
+ local userID
+ local type
+ local validity
+ local keyid
+ local uidfpr
+ local usage
+ local sshKeyGPG
+ local tmpkey
+ local sshFingerprint
+ local gpgSigOut
+
+ userID="ssh://${HOSTP}"
+
+ log "-------------------- Monkeysphere warning -------------------"
+ log "Monkeysphere found OpenPGP keys for this hostname, but none had full validity."
+
+ # retrieve the actual ssh key
+ sshKeyOffered=$(ssh-keyscan -t rsa -p "$PORT" "$HOST" 2>/dev/null | awk '{ print $2, $3 }')
+ # FIXME: should we do any checks for failed keyscans, eg. host not
+ # found?
+
+ # get the gpg info for userid
+ gpgOut=$(gpg --list-key --fixed-list-mode --with-colon \
+ --with-fingerprint --with-fingerprint \
+ ="$userID" 2>/dev/null)
+
+ # find all 'pub' and 'sub' lines in the gpg output, which each
+ # represent a retrieved key for the user ID
+ echo "$gpgOut" | cut -d: -f1,2,5,10,12 | \
+ while IFS=: read -r type validity keyid uidfpr usage ; do
+ case $type in
+ 'pub'|'sub')
+ # get the ssh key of the gpg key
+ sshKeyGPG=$(gpg2ssh "$keyid")
+
+ # if one of keys found matches the one offered by the
+ # host, then output info
+ if [ "$sshKeyGPG" = "$sshKeyOffered" ] ; then
+ log "An OpenPGP key matching the ssh key offered by the host was found:"
+ log
+
+ # do some crazy "Here Strings" redirection to get the key to
+ # ssh-keygen, since it doesn't read from stdin cleanly
+ sshFingerprint=$(ssh-keygen -l -f /dev/stdin \
+ <<<$(echo "$sshKeyGPG") | \
+ awk '{ print $2 }')
+
+ # get the sigs for the matching key
+ gpgSigOut=$(gpg --check-sigs \
+ --list-options show-uid-validity \
+ "$keyid")
+
+ # output the sigs, but only those on the user ID
+ # we are looking for
+ echo "$gpgSigOut" | awk '
+{
+if (match($0,"^pub")) { print; }
+if (match($0,"^uid")) { ok=0; }
+if (match($0,"^uid.*'$userID'$")) { ok=1; print; }
+if (ok) { if (match($0,"^sig")) { print; } }
+}
+' >&2
+ log
+
+ # output the other user IDs for reference
+ if (echo "$gpgSigOut" | grep "^uid" | grep -v -q "$userID") ; then
+ log "Other user IDs on this key:"
+ echo "$gpgSigOut" | grep "^uid" | grep -v "$userID" >&2
+ log
+ fi
+
+ # output ssh fingerprint
+ log "RSA key fingerprint is ${sshFingerprint}."
+
+ # this whole process is in a "while read"
+ # subshell. the only way to get information out
+ # of the subshell is to change the return code.
+ # therefore we return 1 here to indicate that a
+ # matching gpg key was found for the ssh key
+ # offered by the host
+ return 1
+ fi
+ ;;
+ esac
+ done
+
+ # if no key match was made (and the "while read" subshell returned
+ # 1) output how many keys were found
+ if (($? != 1)) ; then
+ log "None of the found keys matched the key offered by the host."
+ log "Run the following command for more info about the found keys:"
+ log "gpg --check-sigs --list-options show-uid-validity =${userID}"
+ # FIXME: should we do anything extra here if the retrieved
+ # host key is actually in the known_hosts file and the ssh
+ # connection will succeed? Should the user be warned?
+ # prompted?
+ fi
+
+ log "-------------------- ssh continues below --------------------"
+}
+
########################################################################
# export the monkeysphere log level
PORT="$2"
if [ -z "$HOST" ] ; then
- echo "Host not specified." >&2
+ log "Host not specified."
usage
exit 255
fi
URI="ssh://${HOSTP}"
# specify keyserver checking. the behavior of this proxy command is
-# intentially different than that of running monkeyesphere normally,
-# and keychecking is intentially done unders certain circumstances.
-# This can be overridden by setting the MONKEYSPHERE_CHECK_KEYSERVER
-# variable on the command line.
+# intentionally different than that of running monkeyesphere normally,
+# and keyserver checking is intentionally done under certain
+# circumstances. This can be overridden by setting the
+# MONKEYSPHERE_CHECK_KEYSERVER environment variable.
# if the host is in the gpg keyring...
if gpg --list-key ="${URI}" 2>&1 >/dev/null ; then
# update the known_hosts file for the host
monkeysphere update-known_hosts "$HOSTP"
+# output on depending on the return of the update-known_hosts
+# subcommand, which is (ultimately) the return code of the
+# update_known_hosts function in common
+case $? in
+ 0)
+ # acceptable host key found so continue to ssh
+ true
+ ;;
+ 1)
+ # no hosts at all found so also continue (drop through to
+ # regular ssh host verification)
+ true
+ ;;
+ 2)
+ # at least one *bad* host key (and no good host keys) was
+ # found, so output some usefull information
+ output_no_valid_key
+ ;;
+ *)
+ # anything else drop through
+ true
+ ;;
+esac
+
+# FIXME: what about the case where monkeysphere successfully finds a
+# valid key for the host and adds it to the known_hosts file, but a
+# different non-monkeysphere key for the host already exists in the
+# known_hosts, and it is this non-ms key that is offered by the host?
+# monkeysphere will succeed, and the ssh connection will succeed, and
+# the user will be left with the impression that they are dealing with
+# a OpenPGP/PKI host key when in fact they are not. should we use
+# ssh-keyscan to compare the keys first?
+
# exec a netcat passthrough to host for the ssh connection
if [ -z "$NO_CONNECT" ] ; then
if (which nc 2>/dev/null >/dev/null); then
projects / monkeysphere.git / blobdiff