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() {
33 userID="ssh://${HOSTP}"
36 -------------------- Monkeysphere warning -------------------
37 Monkeysphere found OpenPGP keys for this hostname, but none had full validity.
40 # retrieve the actual ssh key
41 sshKeyOffered=$(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_user --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
63 An OpenPGP key matching the ssh key offered by the host was found:
67 sshKeyGPGFile=$(msmktempfile)
68 printf "%s" "$sshKeyGPG" >"$sshKeyGPGFile"
69 sshFingerprint=$(ssh-keygen -l -f "$sshKeyGPGFile" | \
71 rm -f "$sshKeyGPGFile"
73 # get the sigs for the matching key
74 gpgSigOut=$(gpg_user --check-sigs \
75 --list-options show-uid-validity \
78 # output the sigs, but only those on the user ID
80 echo "$gpgSigOut" | awk '
82 if (match($0,"^pub")) { print; }
83 if (match($0,"^uid")) { ok=0; }
84 if (match($0,"^uid.*'$userID'$")) { ok=1; print; }
85 if (ok) { if (match($0,"^sig")) { print; } }
90 # output the other user IDs for reference
91 if (echo "$gpgSigOut" | grep "^uid" | grep -v -q "$userID") ; then
93 Other user IDs on this key:
96 echo "$gpgSigOut" | grep "^uid" | grep -v "$userID" | log info
100 # output ssh fingerprint
102 RSA key fingerprint is ${sshFingerprint}.
105 # this whole process is in a "while read"
106 # subshell. the only way to get information out
107 # of the subshell is to change the return code.
108 # therefore we return 1 here to indicate that a
109 # matching gpg key was found for the ssh key
110 # offered by the host
117 # if no key match was made (and the "while read" subshell returned
118 # 1) output how many keys were found
119 if (($? != 1)) ; then
121 None of the found keys matched the key offered by the host.
122 Run the following command for more info about the found keys:
123 gpg --check-sigs --list-options show-uid-validity =${userID}
126 # FIXME: should we do anything extra here if the retrieved
127 # host key is actually in the known_hosts file and the ssh
128 # connection will succeed? Should the user be warned?
133 -------------------- ssh continues below --------------------
138 # the ssh proxycommand function itself
141 if [ "$1" = '--no-connect' ] ; then
149 if [ -z "$HOST" ] ; then
150 log error "Host not specified."
154 if [ -z "$PORT" ] ; then
159 if [ "$PORT" != '22' ] ; then
160 HOSTP="${HOST}:${PORT}"
166 # specify keyserver checking. the behavior of this proxy command is
167 # intentionally different than that of running monkeyesphere normally,
168 # and keyserver checking is intentionally done under certain
169 # circumstances. This can be overridden by setting the
170 # MONKEYSPHERE_CHECK_KEYSERVER environment variable, or by setting the
171 # CHECK_KEYSERVER variable in the monkeysphere.conf file.
173 # if the host is in the gpg keyring...
174 if gpg_user --list-key ="${URI}" 2>&1 >/dev/null ; then
175 # do not check the keyserver
176 CHECK_KEYSERVER=${CHECK_KEYSERVER:="false"}
178 # if the host is NOT in the keyring...
180 # if the host key is found in the known_hosts file...
181 # FIXME: this only works for default known_hosts location
182 hostKey=$(ssh-keygen -F "$HOST" 2>/dev/null)
184 if [ "$hostKey" ] ; then
185 # do not check the keyserver
186 # FIXME: more nuanced checking should be done here to properly
187 # take into consideration hosts that join monkeysphere by
188 # converting an existing and known ssh key
189 CHECK_KEYSERVER=${CHECK_KEYSERVER:="false"}
191 # if the host key is not found in the known_hosts file...
193 # check the keyserver
194 CHECK_KEYSERVER=${CHECK_KEYSERVER:="true"}
198 # finally look in the MONKEYSPHERE_ environment variable for a
199 # CHECK_KEYSERVER setting to override all else
200 CHECK_KEYSERVER=${MONKEYSPHERE_CHECK_KEYSERVER:=$CHECK_KEYSERVER}
202 # update the known_hosts file for the host
203 update_known_hosts "$HOSTP"
205 # output on depending on the return of the update-known_hosts
206 # subcommand, which is (ultimately) the return code of the
207 # update_known_hosts function in common
210 # acceptable host key found so continue to ssh
214 # no hosts at all found so also continue (drop through to
215 # regular ssh host verification)
219 # at least one *bad* host key (and no good host keys) was
220 # found, so output some usefull information
224 # anything else drop through
229 # FIXME: what about the case where monkeysphere successfully finds a
230 # valid key for the host and adds it to the known_hosts file, but a
231 # different non-monkeysphere key for the host already exists in the
232 # known_hosts, and it is this non-ms key that is offered by the host?
233 # monkeysphere will succeed, and the ssh connection will succeed, and
234 # the user will be left with the impression that they are dealing with
235 # a OpenPGP/PKI host key when in fact they are not. should we use
236 # ssh-keyscan to compare the keys first?
238 # exec a netcat passthrough to host for the ssh connection
239 if [ -z "$NO_CONNECT" ] ; then
240 if (which nc 2>/dev/null >/dev/null); then
241 exec nc "$HOST" "$PORT"
242 elif (which socat 2>/dev/null >/dev/null); then
243 exec socat STDIO "TCP:$HOST:$PORT"
245 echo "Neither netcat nor socat found -- could not complete monkeysphere-ssh-proxycommand connection to $HOST:$PORT" >&2