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
18 ########################################################################
21 SYSSHAREDIR=${MONKEYSPHERE_SYSSHAREDIR:-"/usr/share/monkeysphere"}
23 . "${SYSSHAREDIR}/common" || exit 1
25 ########################################################################
27 ########################################################################
31 usage: ssh -o ProxyCommand="$(basename $0) %h %p" ...
39 output_no_valid_key() {
52 userID="ssh://${HOSTP}"
54 log "-------------------- Monkeysphere warning -------------------"
55 log "Monkeysphere found OpenPGP keys for this hostname, but none had full validity."
57 # retrieve the actual ssh key
58 sshKeyOffered=$(ssh-keyscan -t rsa -p "$PORT" "$HOST" 2>/dev/null | awk '{ print $2, $3 }')
59 # FIXME: should we do any checks for failed keyscans, eg. host not
62 # get the gpg info for userid
63 gpgOut=$(gpg --list-key --fixed-list-mode --with-colon \
64 --with-fingerprint --with-fingerprint \
65 ="$userID" 2>/dev/null)
67 # find all 'pub' and 'sub' lines in the gpg output, which each
68 # represent a retrieved key for the user ID
69 echo "$gpgOut" | cut -d: -f1,2,5,10,12 | \
70 while IFS=: read -r type validity keyid uidfpr usage ; do
73 # get the ssh key of the gpg key
74 sshKeyGPG=$(gpg2ssh "$keyid")
76 # if one of keys found matches the one offered by the
77 # host, then output info
78 if [ "$sshKeyGPG" = "$sshKeyOffered" ] ; then
79 log "An OpenPGP key matching the ssh key offered by the host was found:"
82 # do some crazy "Here Strings" redirection to get the key to
83 # ssh-keygen, since it doesn't read from stdin cleanly
84 sshFingerprint=$(ssh-keygen -l -f /dev/stdin \
85 <<<$(echo "$sshKeyGPG") | \
88 # get the sigs for the matching key
89 gpgSigOut=$(gpg --check-sigs \
90 --list-options show-uid-validity \
93 # output the sigs, but only those on the user ID
95 echo "$gpgSigOut" | awk '
97 if (match($0,"^pub")) { print; }
98 if (match($0,"^uid")) { ok=0; }
99 if (match($0,"^uid.*'$userID'$")) { ok=1; print; }
100 if (ok) { if (match($0,"^sig")) { print; } }
105 # output the other user IDs for reference
106 if (echo "$gpgSigOut" | grep "^uid" | grep -v -q "$userID") ; then
107 log "Other user IDs on this key:"
108 echo "$gpgSigOut" | grep "^uid" | grep -v "$userID" >&2
112 # output ssh fingerprint
113 log "RSA key fingerprint is ${sshFingerprint}."
115 # this whole process is in a "while read"
116 # subshell. the only way to get information out
117 # of the subshell is to change the return code.
118 # therefore we return 1 here to indicate that a
119 # matching gpg key was found for the ssh key
120 # offered by the host
127 # if no key match was made (and the "while read" subshell returned
128 # 1) output how many keys were found
129 if (($? != 1)) ; then
130 log "None of the found keys matched the key offered by the host."
131 log "Run the following command for more info about the found keys:"
132 log "gpg --check-sigs --list-options show-uid-validity =${userID}"
133 # FIXME: should we do anything extra here if the retrieved
134 # host key is actually in the known_hosts file and the ssh
135 # connection will succeed? Should the user be warned?
139 log "-------------------- ssh continues below --------------------"
142 ########################################################################
144 # export the monkeysphere log level
145 export MONKEYSPHERE_LOG_LEVEL
147 if [ "$1" = '--no-connect' ] ; then
155 if [ -z "$HOST" ] ; then
156 log "Host not specified."
160 if [ -z "$PORT" ] ; then
165 if [ "$PORT" != '22' ] ; then
166 HOSTP="${HOST}:${PORT}"
172 # specify keyserver checking. the behavior of this proxy command is
173 # intentionally different than that of running monkeyesphere normally,
174 # and keyserver checking is intentionally done under certain
175 # circumstances. This can be overridden by setting the
176 # MONKEYSPHERE_CHECK_KEYSERVER environment variable.
178 # if the host is in the gpg keyring...
179 if gpg --list-key ="${URI}" 2>&1 >/dev/null ; then
180 # do not check the keyserver
181 CHECK_KEYSERVER="false"
183 # if the host is NOT in the keyring...
185 # if the host key is found in the known_hosts file...
186 # FIXME: this only works for default known_hosts location
187 hostKey=$(ssh-keygen -F "$HOST" 2>/dev/null)
189 if [ "$hostKey" ] ; then
190 # do not check the keyserver
191 # FIXME: more nuanced checking should be done here to properly
192 # take into consideration hosts that join monkeysphere by
193 # converting an existing and known ssh key
194 CHECK_KEYSERVER="false"
196 # if the host key is not found in the known_hosts file...
198 # check the keyserver
199 CHECK_KEYSERVER="true"
202 # set and export the variable for use by monkeysphere
203 MONKEYSPHERE_CHECK_KEYSERVER=${MONKEYSPHERE_CHECK_KEYSERVER:="$CHECK_KEYSERVER"}
204 export MONKEYSPHERE_CHECK_KEYSERVER
206 # update the known_hosts file for the host
207 monkeysphere update-known_hosts "$HOSTP"
209 # output on depending on the return of the update-known_hosts
210 # subcommand, which is (ultimately) the return code of the
211 # update_known_hosts function in common
214 # acceptable host key found so continue to ssh
218 # no hosts at all found so also continue (drop through to
219 # regular ssh host verification)
223 # at least one *bad* host key (and no good host keys) was
224 # found, so output some usefull information
228 # anything else drop through
233 # FIXME: what about the case where monkeysphere successfully finds a
234 # valid key for the host and adds it to the known_hosts file, but a
235 # different non-monkeysphere key for the host already exists in the
236 # known_hosts, and it is this non-ms key that is offered by the host?
237 # monkeysphere will succeed, and the ssh connection will succeed, and
238 # the user will be left with the impression that they are dealing with
239 # a OpenPGP/PKI host key when in fact they are not. should we use
240 # ssh-keyscan to compare the keys first?
242 # exec a netcat passthrough to host for the ssh connection
243 if [ -z "$NO_CONNECT" ] ; then
244 if (which nc 2>/dev/null >/dev/null); then
245 exec nc "$HOST" "$PORT"
246 elif (which socat 2>/dev/null >/dev/null); then
247 exec socat STDIO "TCP:$HOST:$PORT"
249 echo "Neither netcat nor socat found -- could not complete monkeysphere-ssh-proxycommand connection to $HOST:$PORT" >&2