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 # "marginal case" ouput in the case that there is not a full
19 # validation path to the host
20 output_no_valid_key() {
35 userID="ssh://${HOSTP}"
40 -------------------- Monkeysphere warning -------------------
41 Monkeysphere found OpenPGP keys for this hostname, but none had full validity.
44 # retrieve the actual ssh key
45 sshKeyOffered=$(ssh-keyscan -t rsa -p "$PORT" "$HOST" 2>/dev/null | awk '{ print $2, $3 }')
46 # FIXME: should we do any checks for failed keyscans, eg. host not
49 # get the gpg info for userid
50 gpgOut=$(gpg_user --list-key --fixed-list-mode --with-colon \
51 --with-fingerprint --with-fingerprint \
52 ="$userID" 2>/dev/null)
54 # find all 'pub' and 'sub' lines in the gpg output, which each
55 # represent a retrieved key for the user ID
56 echo "$gpgOut" | cut -d: -f1,2,5,10,12 | \
57 while IFS=: read -r type validity keyid uidfpr usage ; do
60 # get the ssh key of the gpg key
61 sshKeyGPG=$(gpg2ssh "$keyid")
63 # if one of keys found matches the one offered by the
64 # host, then output info
65 if [ "$sshKeyGPG" = "$sshKeyOffered" ] ; then
67 An OpenPGP key matching the ssh key offered by the host was found:
71 sshKeyGPGFile=$(msmktempfile)
72 printf "%s" "$sshKeyGPG" >"$sshKeyGPGFile"
73 sshFingerprint=$(ssh-keygen -l -f "$sshKeyGPGFile" | \
75 rm -f "$sshKeyGPGFile"
77 # get the sigs for the matching key
78 gpgSigOut=$(gpg_user --check-sigs \
79 --list-options show-uid-validity \
82 # output the sigs, but only those on the user ID
84 echo "$gpgSigOut" | awk '
86 if (match($0,"^pub")) { print; }
87 if (match($0,"^uid")) { ok=0; }
88 if (match($0,"^uid.*'$userID'$")) { ok=1; print; }
89 if (ok) { if (match($0,"^sig")) { print; } }
94 # output the other user IDs for reference
95 if (echo "$gpgSigOut" | grep "^uid" | grep -v -q "$userID") ; then
97 Other user IDs on this key:
100 echo "$gpgSigOut" | grep "^uid" | grep -v "$userID" | log info
104 # output ssh fingerprint
106 RSA key fingerprint is ${sshFingerprint}.
109 # this whole process is in a "while read"
110 # subshell. the only way to get information out
111 # of the subshell is to change the return code.
112 # therefore we return 1 here to indicate that a
113 # matching gpg key was found for the ssh key
114 # offered by the host
119 done || returnCode="$?"
121 # if no key match was made (and the "while read" subshell returned
122 # 1) output how many keys were found
123 if (( returnCode != 1 )) ; then
125 None of the found keys matched the key offered by the host.
126 Run the following command for more info about the found keys:
127 gpg --check-sigs --list-options show-uid-validity =${userID}
130 # FIXME: should we do anything extra here if the retrieved
131 # host key is actually in the known_hosts file and the ssh
132 # connection will succeed? Should the user be warned?
137 -------------------- ssh continues below --------------------
142 # the ssh proxycommand function itself
145 if [ "$1" = '--no-connect' ] ; then
153 if [ -z "$HOST" ] ; then
154 log error "Host not specified."
158 if [ -z "$PORT" ] ; then
163 if [ "$PORT" != '22' ] ; then
164 HOSTP="${HOST}:${PORT}"
170 # specify keyserver checking. the behavior of this proxy command is
171 # intentionally different than that of running monkeyesphere normally,
172 # and keyserver checking is intentionally done under certain
173 # circumstances. This can be overridden by setting the
174 # MONKEYSPHERE_CHECK_KEYSERVER environment variable, or by setting the
175 # CHECK_KEYSERVER variable in the monkeysphere.conf file.
177 # if the host is in the gpg keyring...
178 if gpg_user --list-key ="${URI}" 2>&1 >/dev/null ; then
179 # do not check the keyserver
180 CHECK_KEYSERVER=${CHECK_KEYSERVER:="false"}
182 # if the host is NOT in the keyring...
184 # if the host key is found in the known_hosts file...
185 # FIXME: this only works for default known_hosts location
186 hostKey=$(ssh-keygen -F "$HOST" 2>/dev/null)
188 if [ "$hostKey" ] ; then
189 # do not check the keyserver
190 # FIXME: more nuanced checking should be done here to properly
191 # take into consideration hosts that join monkeysphere by
192 # converting an existing and known ssh key
193 CHECK_KEYSERVER=${CHECK_KEYSERVER:="false"}
195 # if the host key is not found in the known_hosts file...
197 # check the keyserver
198 CHECK_KEYSERVER=${CHECK_KEYSERVER:="true"}
202 # finally look in the MONKEYSPHERE_ environment variable for a
203 # CHECK_KEYSERVER setting to override all else
204 CHECK_KEYSERVER=${MONKEYSPHERE_CHECK_KEYSERVER:=$CHECK_KEYSERVER}
206 # update the known_hosts file for the host
208 update_known_hosts "$HOSTP" || returnCode="$?"
210 # output on depending on the return of the update-known_hosts
211 # subcommand, which is (ultimately) the return code of the
212 # update_known_hosts function in common
213 case "$returnCode" in
215 # acceptable host key found so continue to ssh
219 # no hosts at all found so also continue (drop through to
220 # regular ssh host verification)
224 # at least one *bad* host key (and no good host keys) was
225 # found, so output some usefull information
229 # anything else drop through
234 # FIXME: what about the case where monkeysphere successfully finds a
235 # valid key for the host and adds it to the known_hosts file, but a
236 # different non-monkeysphere key for the host already exists in the
237 # known_hosts, and it is this non-ms key that is offered by the host?
238 # monkeysphere will succeed, and the ssh connection will succeed, and
239 # the user will be left with the impression that they are dealing with
240 # a OpenPGP/PKI host key when in fact they are not. should we use
241 # ssh-keyscan to compare the keys first?
243 # exec a netcat passthrough to host for the ssh connection
244 if [ -z "$NO_CONNECT" ] ; then
245 if (which nc 2>/dev/null >/dev/null); then
246 exec nc "$HOST" "$PORT"
247 elif (which socat 2>/dev/null >/dev/null); then
248 exec socat STDIO "TCP:$HOST:$PORT"
250 echo "Neither netcat nor socat found -- could not complete monkeysphere-ssh-proxycommand connection to $HOST:$PORT" >&2