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() {
34 userID="ssh://${HOSTP}"
37 -------------------- Monkeysphere warning -------------------
38 Monkeysphere found OpenPGP keys for this hostname, but none had full validity.
41 # retrieve the actual ssh key
42 sshKeyOffered=$(ssh-keyscan -t rsa -p "$PORT" "$HOST" 2>/dev/null | awk '{ print $2, $3 }')
43 # FIXME: should we do any checks for failed keyscans, eg. host not
46 # get the gpg info for userid
47 gpgOut=$(gpg_user --list-key --fixed-list-mode --with-colon \
48 --with-fingerprint --with-fingerprint \
49 ="$userID" 2>/dev/null)
51 # find all 'pub' and 'sub' lines in the gpg output, which each
52 # represent a retrieved key for the user ID
53 echo "$gpgOut" | cut -d: -f1,2,5,10,12 | \
54 while IFS=: read -r type validity keyid uidfpr usage ; do
57 # get the ssh key of the gpg key
58 sshKeyGPG=$(gpg2ssh "$keyid")
60 # if one of keys found matches the one offered by the
61 # host, then output info
62 if [ "$sshKeyGPG" = "$sshKeyOffered" ] ; then
64 An OpenPGP key matching the ssh key offered by the host was found:
68 sshKeyGPGFile=$(msmktempfile)
69 printf "%s" "$sshKeyGPG" >"$sshKeyGPGFile"
70 sshFingerprint=$(ssh-keygen -l -f "$sshKeyGPGFile" | \
72 rm -f "$sshKeyGPGFile"
74 # get the sigs for the matching key
75 gpgSigOut=$(gpg_user --check-sigs \
76 --list-options show-uid-validity \
79 # output the sigs, but only those on the user ID
81 echo "$gpgSigOut" | awk '
83 if (match($0,"^pub")) { print; }
84 if (match($0,"^uid")) { ok=0; }
85 if (match($0,"^uid.*'$userID'$")) { ok=1; print; }
86 if (ok) { if (match($0,"^sig")) { print; } }
91 # output the other user IDs for reference
92 if (echo "$gpgSigOut" | grep "^uid" | grep -v -q "$userID") ; then
94 Other user IDs on this key:
97 echo "$gpgSigOut" | grep "^uid" | grep -v "$userID" | log info
101 # output ssh fingerprint
103 RSA key fingerprint is ${sshFingerprint}.
106 # this whole process is in a "while read"
107 # subshell. the only way to get information out
108 # of the subshell is to change the return code.
109 # therefore we return 1 here to indicate that a
110 # matching gpg key was found for the ssh key
111 # offered by the host
116 done || returnCode="$?"
118 # if no key match was made (and the "while read" subshell returned
119 # 1) output how many keys were found
120 if (( "$returnCode" != 1 )) ; then
122 None of the found keys matched the key offered by the host.
123 Run the following command for more info about the found keys:
124 gpg --check-sigs --list-options show-uid-validity =${userID}
127 # FIXME: should we do anything extra here if the retrieved
128 # host key is actually in the known_hosts file and the ssh
129 # connection will succeed? Should the user be warned?
134 -------------------- ssh continues below --------------------
139 # the ssh proxycommand function itself
142 if [ "$1" = '--no-connect' ] ; then
150 if [ -z "$HOST" ] ; then
151 log error "Host not specified."
155 if [ -z "$PORT" ] ; then
160 if [ "$PORT" != '22' ] ; then
161 HOSTP="${HOST}:${PORT}"
167 # specify keyserver checking. the behavior of this proxy command is
168 # intentionally different than that of running monkeyesphere normally,
169 # and keyserver checking is intentionally done under certain
170 # circumstances. This can be overridden by setting the
171 # MONKEYSPHERE_CHECK_KEYSERVER environment variable, or by setting the
172 # CHECK_KEYSERVER variable in the monkeysphere.conf file.
174 # if the host is in the gpg keyring...
175 if gpg_user --list-key ="${URI}" 2>&1 >/dev/null ; then
176 # do not check the keyserver
177 CHECK_KEYSERVER=${CHECK_KEYSERVER:="false"}
179 # if the host is NOT in the keyring...
181 # if the host key is found in the known_hosts file...
182 # FIXME: this only works for default known_hosts location
183 hostKey=$(ssh-keygen -F "$HOST" 2>/dev/null)
185 if [ "$hostKey" ] ; then
186 # do not check the keyserver
187 # FIXME: more nuanced checking should be done here to properly
188 # take into consideration hosts that join monkeysphere by
189 # converting an existing and known ssh key
190 CHECK_KEYSERVER=${CHECK_KEYSERVER:="false"}
192 # if the host key is not found in the known_hosts file...
194 # check the keyserver
195 CHECK_KEYSERVER=${CHECK_KEYSERVER:="true"}
199 # finally look in the MONKEYSPHERE_ environment variable for a
200 # CHECK_KEYSERVER setting to override all else
201 CHECK_KEYSERVER=${MONKEYSPHERE_CHECK_KEYSERVER:=$CHECK_KEYSERVER}
203 # update the known_hosts file for the host
205 update_known_hosts "$HOSTP" || returnCode="$?"
207 # output on depending on the return of the update-known_hosts
208 # subcommand, which is (ultimately) the return code of the
209 # update_known_hosts function in common
210 case "$returnCode" in
212 # acceptable host key found so continue to ssh
216 # no hosts at all found so also continue (drop through to
217 # regular ssh host verification)
221 # at least one *bad* host key (and no good host keys) was
222 # found, so output some usefull information
226 # anything else drop through
231 # FIXME: what about the case where monkeysphere successfully finds a
232 # valid key for the host and adds it to the known_hosts file, but a
233 # different non-monkeysphere key for the host already exists in the
234 # known_hosts, and it is this non-ms key that is offered by the host?
235 # monkeysphere will succeed, and the ssh connection will succeed, and
236 # the user will be left with the impression that they are dealing with
237 # a OpenPGP/PKI host key when in fact they are not. should we use
238 # ssh-keyscan to compare the keys first?
240 # exec a netcat passthrough to host for the ssh connection
241 if [ -z "$NO_CONNECT" ] ; then
242 if (which nc 2>/dev/null >/dev/null); then
243 exec nc "$HOST" "$PORT"
244 elif (which socat 2>/dev/null >/dev/null); then
245 exec socat STDIO "TCP:$HOST:$PORT"
247 echo "Neither netcat nor socat found -- could not complete monkeysphere-ssh-proxycommand connection to $HOST:$PORT" >&2