2 # This should be sourced by bash (though we welcome changes to make it POSIX sh compliant)
4 # monkeysphere-ssh-proxycommand: MonkeySphere ssh ProxyCommand hook
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
20 # "marginal case" ouput in the case that there is not a full
21 # validation path to the host
22 output_no_valid_key() {
35 userID="ssh://${HOSTP}"
37 log "-------------------- Monkeysphere warning -------------------"
38 log "Monkeysphere found OpenPGP keys for this hostname, but none had full validity."
40 # retrieve the actual ssh key
41 sshKeyOffered=$(ssh-keyscan -t rsa -p "$PORT" "$HOST" 2>/dev/null | awk '{ print $2, $3 }')
42 # FIXME: should we do any checks for failed keyscans, eg. host not
45 # get the gpg info for userid
46 gpgOut=$(gpg --list-key --fixed-list-mode --with-colon \
47 --with-fingerprint --with-fingerprint \
48 ="$userID" 2>/dev/null)
50 # find all 'pub' and 'sub' lines in the gpg output, which each
51 # represent a retrieved key for the user ID
52 echo "$gpgOut" | cut -d: -f1,2,5,10,12 | \
53 while IFS=: read -r type validity keyid uidfpr usage ; do
56 # get the ssh key of the gpg key
57 sshKeyGPG=$(gpg2ssh "$keyid")
59 # if one of keys found matches the one offered by the
60 # host, then output info
61 if [ "$sshKeyGPG" = "$sshKeyOffered" ] ; then
62 log "An OpenPGP key matching the ssh key offered by the host was found:"
65 # do some crazy "Here Strings" redirection to get the key to
66 # ssh-keygen, since it doesn't read from stdin cleanly
67 sshFingerprint=$(ssh-keygen -l -f /dev/stdin \
68 <<<$(echo "$sshKeyGPG") | \
71 # get the sigs for the matching key
72 gpgSigOut=$(gpg --check-sigs \
73 --list-options show-uid-validity \
76 # output the sigs, but only those on the user ID
78 echo "$gpgSigOut" | awk '
80 if (match($0,"^pub")) { print; }
81 if (match($0,"^uid")) { ok=0; }
82 if (match($0,"^uid.*'$userID'$")) { ok=1; print; }
83 if (ok) { if (match($0,"^sig")) { print; } }
88 # output the other user IDs for reference
89 if (echo "$gpgSigOut" | grep "^uid" | grep -v -q "$userID") ; then
90 log "Other user IDs on this key:"
91 echo "$gpgSigOut" | grep "^uid" | grep -v "$userID" >&2
95 # output ssh fingerprint
96 log "RSA key fingerprint is ${sshFingerprint}."
98 # this whole process is in a "while read"
99 # subshell. the only way to get information out
100 # of the subshell is to change the return code.
101 # therefore we return 1 here to indicate that a
102 # matching gpg key was found for the ssh key
103 # offered by the host
110 # if no key match was made (and the "while read" subshell returned
111 # 1) output how many keys were found
112 if (($? != 1)) ; then
113 log "None of the found keys matched the key offered by the host."
114 log "Run the following command for more info about the found keys:"
115 log "gpg --check-sigs --list-options show-uid-validity =${userID}"
116 # FIXME: should we do anything extra here if the retrieved
117 # host key is actually in the known_hosts file and the ssh
118 # connection will succeed? Should the user be warned?
122 log "-------------------- ssh continues below --------------------"
125 ########################################################################
127 # export the monkeysphere log level
128 export MONKEYSPHERE_LOG_LEVEL
130 if [ "$1" = '--no-connect' ] ; then
138 if [ -z "$HOST" ] ; then
139 log "Host not specified."
143 if [ -z "$PORT" ] ; then
148 if [ "$PORT" != '22' ] ; then
149 HOSTP="${HOST}:${PORT}"
155 # specify keyserver checking. the behavior of this proxy command is
156 # intentionally different than that of running monkeyesphere normally,
157 # and keyserver checking is intentionally done under certain
158 # circumstances. This can be overridden by setting the
159 # MONKEYSPHERE_CHECK_KEYSERVER environment variable.
161 # if the host is in the gpg keyring...
162 if gpg --list-key ="${URI}" 2>&1 >/dev/null ; then
163 # do not check the keyserver
164 CHECK_KEYSERVER="false"
166 # if the host is NOT in the keyring...
168 # if the host key is found in the known_hosts file...
169 # FIXME: this only works for default known_hosts location
170 hostKey=$(ssh-keygen -F "$HOST" 2>/dev/null)
172 if [ "$hostKey" ] ; then
173 # do not check the keyserver
174 # FIXME: more nuanced checking should be done here to properly
175 # take into consideration hosts that join monkeysphere by
176 # converting an existing and known ssh key
177 CHECK_KEYSERVER="false"
179 # if the host key is not found in the known_hosts file...
181 # check the keyserver
182 CHECK_KEYSERVER="true"
185 # set and export the variable for use by monkeysphere
186 MONKEYSPHERE_CHECK_KEYSERVER=${MONKEYSPHERE_CHECK_KEYSERVER:="$CHECK_KEYSERVER"}
187 export MONKEYSPHERE_CHECK_KEYSERVER
189 # update the known_hosts file for the host
190 monkeysphere update-known_hosts "$HOSTP"
192 # output on depending on the return of the update-known_hosts
193 # subcommand, which is (ultimately) the return code of the
194 # update_known_hosts function in common
197 # acceptable host key found so continue to ssh
201 # no hosts at all found so also continue (drop through to
202 # regular ssh host verification)
206 # at least one *bad* host key (and no good host keys) was
207 # found, so output some usefull information
211 # anything else drop through
216 # FIXME: what about the case where monkeysphere successfully finds a
217 # valid key for the host and adds it to the known_hosts file, but a
218 # different non-monkeysphere key for the host already exists in the
219 # known_hosts, and it is this non-ms key that is offered by the host?
220 # monkeysphere will succeed, and the ssh connection will succeed, and
221 # the user will be left with the impression that they are dealing with
222 # a OpenPGP/PKI host key when in fact they are not. should we use
223 # ssh-keyscan to compare the keys first?
225 # exec a netcat passthrough to host for the ssh connection
226 if [ -z "$NO_CONNECT" ] ; then
227 if (which nc 2>/dev/null >/dev/null); then
228 exec nc "$HOST" "$PORT"
229 elif (which socat 2>/dev/null >/dev/null); then
230 exec socat STDIO "TCP:$HOST:$PORT"
232 echo "Neither netcat nor socat found -- could not complete monkeysphere-ssh-proxycommand connection to $HOST:$PORT" >&2