2 # This should be sourced by bash (though we welcome changes to make it POSIX sh compliant)
4 # Monkeysphere ssh-proxycommand subcommand
6 # The monkeysphere scripts are written by:
7 # Jameson Rollins <jrollins@finestructure.net>
8 # Daniel Kahn Gillmor <dkg@fifthhorseman.net>
10 # They are Copyright 2008-2009, and are all released under the GPL,
13 # This is meant to be run as an ssh ProxyCommand to initiate a
14 # monkeysphere known_hosts update before an ssh connection to host is
15 # established. Can be added to ~/.ssh/config as follows:
16 # ProxyCommand monkeysphere ssh-proxycommand %h %p
18 # output the key info, including the RSA fingerprint
26 # get the ssh key of the gpg key
27 sshKeyGPGFile=$(msmktempfile)
28 gpg2ssh "$keyid" >"$sshKeyGPGFile"
29 sshFingerprint=$(ssh-keygen -l -f "$sshKeyGPGFile" | \
31 rm -f "$sshKeyGPGFile"
33 # get the sigs for the matching key
34 gpgSigOut=$(gpg_user --check-sigs \
35 --list-options show-uid-validity \
40 # output the sigs, but only those on the user ID
42 echo "$gpgSigOut" | awk '
44 if (match($0,"^pub")) { print; }
45 if (match($0,"^uid")) { ok=0; }
46 if (match($0,"^uid.*'$userID'$")) { ok=1; print; }
47 if (ok) { if (match($0,"^sig")) { print; } }
51 # output ssh fingerprint
53 RSA key fingerprint is ${sshFingerprint}.
56 # output the other user IDs for reference
57 otherUids=$(echo "$gpgSigOut" | grep "^uid" | grep -v "$userID")
58 if [ "$otherUids" ] ; then
60 Other user IDs on this key:
62 echo "$otherUids" | log info
67 # "marginal case" ouput in the case that there is not a full
68 # validation path to the host
69 output_no_valid_key() {
82 userID="ssh://${HOSTP}"
86 # retrieve the ssh key being offered by the host
87 sshKeyOffered=$(ssh-keyscan -t rsa -p "$PORT" "$HOST" 2>/dev/null \
88 | awk '{ print $2, $3 }')
90 # get the gpg info for userid
91 gpgOut=$(gpg_user --list-key --fixed-list-mode --with-colon \
92 --with-fingerprint --with-fingerprint \
93 ="$userID" 2>/dev/null)
97 -------------------- Monkeysphere warning -------------------
98 Monkeysphere found OpenPGP keys for this hostname, but none had full validity.
101 # output message if host key could not be retrieved from the host
102 if [ -z "$sshKeyOffered" ] ; then
104 Could not retrieve RSA host key from $HOST.
106 # check that there are any marginally valid keys
107 if echo "$gpgOut" | egrep -q '^(pub|sub):(m|f|u):' ; then
109 The following keys were found with marginal validity:
114 # find all keys in the gpg output ('pub' and 'sub' lines) and
115 # output the ones that match the host key or that have marginal
117 echo "$gpgOut" | cut -d: -f1,2,5,10,12 | \
118 while IFS=: read -r type validity keyid uidfpr usage ; do
121 # get the ssh key of the gpg key
122 sshKeyGPG=$(gpg2ssh "$keyid")
123 # if a key was retrieved from the host...
124 if [ "$sshKeyOffered" ] ; then
125 # if one of the keys matches the one offered by
126 # the host, then output info and return
127 if [ "$sshKeyGPG" = "$sshKeyOffered" ] ; then
129 An OpenPGP key matching the ssh key offered by the host was found:
131 show_key_info "$keyid" | log info
132 # this whole process is in a "while read"
133 # subshell. the only way to get information
134 # out of the subshell is to change the return
135 # code. therefore we return 1 here to
136 # indicate that a matching gpg key was found
137 # for the ssh key offered by the host
140 # else if a key was not retrieved from the host...
142 # and the current key is marginal, show info
143 if [ "$validity" = 'm' ] \
144 || [ "$validity" = 'f' ] \
145 || [ "$validity" = 'u' ] ; then
146 show_key_info "$keyid" | log info
151 done || returnCode="$?"
153 # if no key match was made (and the "while read" subshell
154 # returned 1) output how many keys were found
155 if (( returnCode == 1 )) ; then
158 # if a key was retrieved, but didn't match, note this
159 if [ "$sshKeyOffered" ] ; then
161 None of the found keys matched the key offered by the host.
165 # note how many invalid keys were found
166 nInvalidKeys=$(echo "$gpgOut" | egrep '^(pub|sub):[^(m|f|u)]:' | wc -l)
167 if ((nInvalidKeys > 0)) ; then
169 Keys found with less than marginal validity: $nInvalidKeys
174 Run the following command for more info about the found keys:
175 gpg --check-sigs --list-options show-uid-validity =${userID}
178 # FIXME: should we do anything extra here if the retrieved
179 # host key is actually in the known_hosts file and the ssh
180 # connection will succeed? Should the user be warned?
186 -------------------- ssh continues below --------------------
191 # the ssh proxycommand function itself
194 if [ "$1" = '--no-connect' ] ; then
202 if [ -z "$HOST" ] ; then
203 log error "Host not specified."
207 if [ -z "$PORT" ] ; then
212 if [ "$PORT" != '22' ] ; then
213 HOSTP="${HOST}:${PORT}"
219 # specify keyserver checking. the behavior of this proxy command is
220 # intentionally different than that of running monkeyesphere normally,
221 # and keyserver checking is intentionally done under certain
222 # circumstances. This can be overridden by setting the
223 # MONKEYSPHERE_CHECK_KEYSERVER environment variable, or by setting the
224 # CHECK_KEYSERVER variable in the monkeysphere.conf file.
226 # if the host is in the gpg keyring...
227 if gpg_user --list-key ="${URI}" &>/dev/null ; then
228 # do not check the keyserver
229 CHECK_KEYSERVER=${CHECK_KEYSERVER:="false"}
231 # if the host is NOT in the keyring...
233 # if the host key is found in the known_hosts file...
234 hostKey=$( [ ! -r "$KNOWN_HOSTS" ] || ssh-keygen -F "$HOST" -f "$KNOWN_HOSTS" 2>/dev/null)
236 if [ "$hostKey" ] ; then
237 # do not check the keyserver
238 # FIXME: more nuanced checking should be done here to properly
239 # take into consideration hosts that join monkeysphere by
240 # converting an existing and known ssh key
241 CHECK_KEYSERVER=${CHECK_KEYSERVER:="false"}
243 # if the host key is not found in the known_hosts file...
245 # check the keyserver
246 CHECK_KEYSERVER=${CHECK_KEYSERVER:="true"}
250 # finally look in the MONKEYSPHERE_ environment variable for a
251 # CHECK_KEYSERVER setting to override all else
252 CHECK_KEYSERVER=${MONKEYSPHERE_CHECK_KEYSERVER:=$CHECK_KEYSERVER}
254 # update the known_hosts file for the host
256 update_known_hosts "$HOSTP" || returnCode="$?"
258 # output on depending on the return of the update-known_hosts
259 # subcommand, which is (ultimately) the return code of the
260 # update_known_hosts function in common
261 case "$returnCode" in
263 # acceptable host key found so continue to ssh
267 # no hosts at all found so also continue (drop through to
268 # regular ssh host verification)
272 # at least one *bad* host key (and no good host keys) was
273 # found, so output some usefull information
277 # anything else drop through
282 # FIXME: what about the case where monkeysphere successfully finds a
283 # valid key for the host and adds it to the known_hosts file, but a
284 # different non-monkeysphere key for the host already exists in the
285 # known_hosts, and it is this non-ms key that is offered by the host?
286 # monkeysphere will succeed, and the ssh connection will succeed, and
287 # the user will be left with the impression that they are dealing with
288 # a OpenPGP/PKI host key when in fact they are not. should we use
289 # ssh-keyscan to compare the keys first?
291 # exec a netcat passthrough to host for the ssh connection
292 if [ -z "$NO_CONNECT" ] ; then
293 if (type nc &>/dev/null); then
294 exec nc "$HOST" "$PORT"
295 elif (type socat &>/dev/null); then
296 exec socat STDIO "TCP:$HOST:$PORT"
298 echo "Neither netcat nor socat found -- could not complete monkeysphere-ssh-proxycommand connection to $HOST:$PORT" >&2