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-rw-r--r--ChangeLog4
-rw-r--r--contrib/ssh-copy-id309
-rw-r--r--contrib/ssh-copy-id.1251
3 files changed, 459 insertions, 105 deletions
diff --git a/ChangeLog b/ChangeLog
index 80429f849..d69fd350c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
120120322
2 - (djm) [contrib/ssh-copy-id contrib/ssh-copy-id.1] Updated to Phil
3 Hands' greatly revised version.
4
120120318 520120318
2 - (djm) [configure.ac log.c scp.c sshconnect2.c openbsd-compat/vis.c] 6 - (djm) [configure.ac log.c scp.c sshconnect2.c openbsd-compat/vis.c]
3 [openbsd-compat/vis.h] FreeBSD's strnvis isn't compatible with OpenBSD's 7 [openbsd-compat/vis.h] FreeBSD's strnvis isn't compatible with OpenBSD's
diff --git a/contrib/ssh-copy-id b/contrib/ssh-copy-id
index 9451aceec..af18a1929 100644
--- a/contrib/ssh-copy-id
+++ b/contrib/ssh-copy-id
@@ -1,54 +1,293 @@
1#!/bin/sh 1#!/bin/sh
2 2
3# Shell script to install your public key on a remote machine 3# Copyright (c) 1999-2013 Philip Hands <phil@hands.com>
4# Takes the remote machine name as an argument. 4# 2013 Martin Kletzander <mkletzan@redhat.com>
5# Obviously, the remote machine must accept password authentication, 5# 2010 Adeodato =?iso-8859-1?Q?Sim=F3?= <asp16@alu.ua.es>
6# or one of the other keys in your ssh-agent, for this to work. 6# 2010 Eric Moret <eric.moret@gmail.com>
7 7# 2009 Xr <xr@i-jeuxvideo.com>
8ID_FILE="${HOME}/.ssh/id_rsa.pub" 8# 2007 Justin Pryzby <justinpryzby@users.sourceforge.net>
9 9# 2004 Reini Urban <rurban@x-ray.at>
10if [ "-i" = "$1" ]; then 10# 2003 Colin Watson <cjwatson@debian.org>
11 shift 11# All rights reserved.
12 # check if we have 2 parameters left, if so the first is the new ID file 12#
13 if [ -n "$2" ]; then 13# Redistribution and use in source and binary forms, with or without
14 if expr "$1" : ".*\.pub" > /dev/null ; then 14# modification, are permitted provided that the following conditions
15 ID_FILE="$1" 15# are met:
16 else 16# 1. Redistributions of source code must retain the above copyright
17 ID_FILE="$1.pub" 17# notice, this list of conditions and the following disclaimer.
18 fi 18# 2. Redistributions in binary form must reproduce the above copyright
19 shift # and this should leave $1 as the target name 19# notice, this list of conditions and the following disclaimer in the
20# documentation and/or other materials provided with the distribution.
21#
22# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
23# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
24# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
25# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
26# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
27# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
28# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
29# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
30# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
31# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32
33# Shell script to install your public key(s) on a remote machine
34# See the ssh-copy-id(1) man page for details
35
36# check that we have something mildly sane as our shell, or try to find something better
37if false ^ printf "%s: WARNING: ancient shell, hunting for a more modern one... " "$0"
38then
39 SANE_SH=${SANE_SH:-/usr/bin/ksh}
40 if printf 'true ^ false\n' | "$SANE_SH"
41 then
42 printf "'%s' seems viable.\n" "$SANE_SH"
43 exec "$SANE_SH" "$0" "$@"
44 else
45 cat <<-EOF
46 oh dear.
47
48 If you have a more recent shell available, that supports \$(...) etc.
49 please try setting the environment variable SANE_SH to the path of that
50 shell, and then retry running this script. If that works, please report
51 a bug describing your setup, and the shell you used to make it work.
52
53 EOF
54 printf "%s: ERROR: Less dimwitted shell required.\n" "$0"
55 exit 1
20 fi 56 fi
21else 57fi
22 if [ x$SSH_AUTH_SOCK != x ] && ssh-add -L >/dev/null 2>&1; then 58
23 GET_ID="$GET_ID ssh-add -L" 59DEFAULT_PUB_ID_FILE=$(ls -t ${HOME}/.ssh/id*.pub 2>/dev/null | grep -v -- '-cert.pub$' | head -n 1)
60
61usage () {
62 printf 'Usage: %s [-h|-?|-n] [-i [identity_file]] [-p port] [[-o <ssh -o options>] ...] [user@]hostname\n' "$0" >&2
63 exit 1
64}
65
66# escape any single quotes in an argument
67quote() {
68 printf "%s\n" "$1" | sed -e "s/'/'\\\\''/g"
69}
70
71use_id_file() {
72 local L_ID_FILE="$1"
73
74 if expr "$L_ID_FILE" : ".*\.pub$" >/dev/null ; then
75 PUB_ID_FILE="$L_ID_FILE"
76 else
77 PUB_ID_FILE="$L_ID_FILE.pub"
24 fi 78 fi
79
80 PRIV_ID_FILE=$(dirname "$PUB_ID_FILE")/$(basename "$PUB_ID_FILE" .pub)
81
82 # check that the files are readable
83 for f in $PUB_ID_FILE $PRIV_ID_FILE ; do
84 ErrMSG=$( { : < $f ; } 2>&1 ) || {
85 printf "\n%s: ERROR: failed to open ID file '%s': %s\n\n" "$0" "$f" "$(printf "%s\n" "$ErrMSG" | sed -e 's/.*: *//')"
86 exit 1
87 }
88 done
89 GET_ID="cat \"$PUB_ID_FILE\""
90}
91
92if [ -n "$SSH_AUTH_SOCK" ] && ssh-add -L >/dev/null 2>&1 ; then
93 GET_ID="ssh-add -L"
25fi 94fi
26 95
27if [ -z "`eval $GET_ID`" ] && [ -r "${ID_FILE}" ] ; then 96while test "$#" -gt 0
28 GET_ID="cat \"${ID_FILE}\"" 97do
98 [ "${SEEN_OPT_I}" ] && expr "$1" : "[-]i" >/dev/null && {
99 printf "\n%s: ERROR: -i option must not be specified more than once\n\n" "$0"
100 usage
101 }
102
103 OPT= OPTARG=
104 # implement something like getopt to avoid Solaris pain
105 case "$1" in
106 -i?*|-o?*|-p?*)
107 OPT="$(printf -- "$1"|cut -c1-2)"
108 OPTARG="$(printf -- "$1"|cut -c3-)"
109 shift
110 ;;
111 -o|-p)
112 OPT="$1"
113 OPTARG="$2"
114 shift 2
115 ;;
116 -i)
117 OPT="$1"
118 test "$#" -le 2 || expr "$2" : "[-]" >/dev/null || {
119 OPTARG="$2"
120 shift
121 }
122 shift
123 ;;
124 -n|-h|-\?)
125 OPT="$1"
126 OPTARG=
127 shift
128 ;;
129 --)
130 shift
131 while test "$#" -gt 0
132 do
133 SAVEARGS="${SAVEARGS:+$SAVEARGS }'$(quote "$1")'"
134 shift
135 done
136 break
137 ;;
138 -*)
139 printf "\n%s: ERROR: invalid option (%s)\n\n" "$0" "$1"
140 usage
141 ;;
142 *)
143 SAVEARGS="${SAVEARGS:+$SAVEARGS }'$(quote "$1")'"
144 shift
145 continue
146 ;;
147 esac
148
149 case "$OPT" in
150 -i)
151 SEEN_OPT_I="yes"
152 use_id_file "${OPTARG:-$DEFAULT_PUB_ID_FILE}"
153 ;;
154 -o|-p)
155 SSH_OPTS="${SSH_OPTS:+$SSH_OPTS }$OPT '$(quote "$OPTARG")'"
156 ;;
157 -n)
158 DRY_RUN=1
159 ;;
160 -h|-\?)
161 usage
162 ;;
163 esac
164done
165
166eval set -- "$SAVEARGS"
167
168if [ $# != 1 ] ; then
169 printf '%s: ERROR: Too many arguments. Expecting a target hostname, got: %s\n\n' "$0" "$SAVEARGS" >&2
170 usage
29fi 171fi
30 172
31if [ -z "`eval $GET_ID`" ]; then 173# drop trailing colon
32 echo "$0: ERROR: No identities found" >&2 174USER_HOST=$(printf "%s\n" "$1" | sed 's/:$//')
33 exit 1 175# tack the hostname onto SSH_OPTS
176SSH_OPTS="${SSH_OPTS:+$SSH_OPTS }'$(quote "$USER_HOST")'"
177# and populate "$@" for later use (only way to get proper quoting of options)
178eval set -- "$SSH_OPTS"
179
180if [ -z "$(eval $GET_ID)" ] && [ -r "${PUB_ID_FILE:=$DEFAULT_PUB_ID_FILE}" ] ; then
181 use_id_file "$PUB_ID_FILE"
34fi 182fi
35 183
36if [ "$#" -lt 1 ] || [ "$1" = "-h" ] || [ "$1" = "--help" ]; then 184if [ -z "$(eval $GET_ID)" ] ; then
37 echo "Usage: $0 [-i [identity_file]] [user@]machine" >&2 185 printf '%s: ERROR: No identities found\n' "$0" >&2
38 exit 1 186 exit 1
39fi 187fi
40 188
41# strip any trailing colon 189# populate_new_ids() uses several global variables ($USER_HOST, $SSH_OPTS ...)
42host=`echo $1 | sed 's/:$//'` 190# and has the side effect of setting $NEW_IDS
191populate_new_ids() {
192 local L_SUCCESS="$1"
43 193
44{ eval "$GET_ID" ; } | ssh $host "umask 077; test -d ~/.ssh || mkdir ~/.ssh ; cat >> ~/.ssh/authorized_keys" || exit 1 194 # repopulate "$@" inside this function
195 eval set -- "$SSH_OPTS"
45 196
46cat <<EOF 197 umask 0177
47Now try logging into the machine, with "ssh '$host'", and check in: 198 local L_TMP_ID_FILE=$(mktemp ~/.ssh/ssh-copy-id_id.XXXXXXXXXX)
199 trap "rm -f $L_TMP_ID_FILE*" EXIT TERM INT QUIT
200 printf '%s: INFO: attempting to log in with the new key(s), to filter out any that are already installed\n' "$0" >&2
201 NEW_IDS=$(
202 eval $GET_ID | {
203 while read ID ; do
204 printf '%s\n' "$ID" > $L_TMP_ID_FILE
48 205
49 ~/.ssh/authorized_keys 206 # the next line assumes $PRIV_ID_FILE only set if using a single id file - this
207 # assumption will break if we implement the possibility of multiple -i options.
208 # The point being that if file based, ssh needs the private key, which it cannot
209 # find if only given the contents of the .pub file in an unrelated tmpfile
210 ssh -i "${PRIV_ID_FILE:-$L_TMP_ID_FILE}" \
211 -o PreferredAuthentications=publickey \
212 -o IdentitiesOnly=yes "$@" exit 2>$L_TMP_ID_FILE.stderr </dev/null
213 if [ "$?" = "$L_SUCCESS" ] ; then
214 : > $L_TMP_ID_FILE
215 else
216 grep 'Permission denied' $L_TMP_ID_FILE.stderr >/dev/null || {
217 sed -e 's/^/ERROR: /' <$L_TMP_ID_FILE.stderr >$L_TMP_ID_FILE
218 cat >/dev/null #consume the other keys, causing loop to end
219 }
220 fi
221
222 cat $L_TMP_ID_FILE
223 done
224 }
225 )
226 rm -f $L_TMP_ID_FILE* && trap - EXIT TERM INT QUIT
227
228 if expr "$NEW_IDS" : "^ERROR: " >/dev/null ; then
229 printf '\n%s: %s\n\n' "$0" "$NEW_IDS" >&2
230 exit 1
231 fi
232 if [ -z "$NEW_IDS" ] ; then
233 printf '\n%s: WARNING: All keys were skipped because they already exist on the remote system.\n\n' "$0" >&2
234 exit 0
235 fi
236 printf '%s: INFO: %d key(s) remain to be installed -- if you are prompted now it is to install the new keys\n' "$0" "$(printf '%s\n' "$NEW_IDS" | wc -l)" >&2
237}
50 238
51to make sure we haven't added extra keys that you weren't expecting. 239REMOTE_VERSION=$(ssh -v -o PreferredAuthentications=',' "$@" 2>&1 |
240 sed -ne 's/.*remote software version //p')
52 241
53EOF 242case "$REMOTE_VERSION" in
243 NetScreen*)
244 populate_new_ids 1
245 for KEY in $(printf "%s" "$NEW_IDS" | cut -d' ' -f2) ; do
246 KEY_NO=$(($KEY_NO + 1))
247 printf "%s\n" "$KEY" | grep ssh-dss >/dev/null || {
248 printf '%s: WARNING: Non-dsa key (#%d) skipped (NetScreen only supports DSA keys)\n' "$0" "$KEY_NO" >&2
249 continue
250 }
251 [ "$DRY_RUN" ] || printf 'set ssh pka-dsa key %s\nsave\nexit\n' "$KEY" | ssh -T "$@" >/dev/null 2>&1
252 if [ $? = 255 ] ; then
253 printf '%s: ERROR: installation of key #%d failed (please report a bug describing what caused this, so that we can make this message useful)\n' "$0" "$KEY_NO" >&2
254 else
255 ADDED=$(($ADDED + 1))
256 fi
257 done
258 if [ -z "$ADDED" ] ; then
259 exit 1
260 fi
261 ;;
262 *)
263 # Assuming that the remote host treats ~/.ssh/authorized_keys as one might expect
264 populate_new_ids 0
265 [ "$DRY_RUN" ] || printf '%s\n' "$NEW_IDS" | ssh "$@" "
266 umask 077 ;
267 mkdir -p .ssh && cat >> .ssh/authorized_keys || exit 1 ;
268 if type restorecon >/dev/null 2>&1 ; then restorecon -F .ssh .ssh/authorized_keys ; fi" \
269 || exit 1
270 ADDED=$(printf '%s\n' "$NEW_IDS" | wc -l)
271 ;;
272esac
273
274if [ "$DRY_RUN" ] ; then
275 cat <<-EOF
276 =-=-=-=-=-=-=-=
277 Would have added the following key(s):
278
279 $NEW_IDS
280 =-=-=-=-=-=-=-=
281 EOF
282else
283 cat <<-EOF
284
285 Number of key(s) added: $ADDED
286
287 Now try logging into the machine, with: "ssh $SSH_OPTS"
288 and check to make sure that only the key(s) you wanted were added.
289
290 EOF
291fi
54 292
293# =-=-=-=
diff --git a/contrib/ssh-copy-id.1 b/contrib/ssh-copy-id.1
index cb15ab24d..67a59e492 100644
--- a/contrib/ssh-copy-id.1
+++ b/contrib/ssh-copy-id.1
@@ -1,75 +1,186 @@
1.ig \" -*- nroff -*- 1.ig \" -*- nroff -*-
2Copyright (c) 1999 Philip Hands Computing <http://www.hands.com/> 2Copyright (c) 1999-2013 hands.com Ltd. <http://hands.com/>
3 3
4Permission is granted to make and distribute verbatim copies of 4Redistribution and use in source and binary forms, with or without
5this manual provided the copyright notice and this permission notice 5modification, are permitted provided that the following conditions
6are preserved on all copies. 6are met:
71. Redistributions of source code must retain the above copyright
8 notice, this list of conditions and the following disclaimer.
92. Redistributions in binary form must reproduce the above copyright
10 notice, this list of conditions and the following disclaimer in the
11 documentation and/or other materials provided with the distribution.
7 12
8Permission is granted to copy and distribute modified versions of this 13THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
9manual under the conditions for verbatim copying, provided that the 14IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
10entire resulting derived work is distributed under the terms of a 15OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
11permission notice identical to this one. 16IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
12 17INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
13Permission is granted to copy and distribute translations of this 18NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
14manual into another language, under the above conditions for modified 19DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
15versions, except that this permission notice may be included in 20THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
16translations approved by the Free Software Foundation instead of in 21(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
17the original English. 22THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
18.. 23..
19.TH SSH-COPY-ID 1 "14 November 1999" "OpenSSH" 24.Dd $Mdocdate: June 17 2010 $
20.SH NAME 25.Dt SSH-COPY-ID 1
21ssh-copy-id \- install your public key in a remote machine's authorized_keys 26.Os
22.SH SYNOPSIS 27.Sh NAME
23.B ssh-copy-id [-i [identity_file]] 28.Nm ssh-copy-id
24.I "[user@]machine" 29.Nd use locally available keys to authorise logins on a remote machine
30.Sh SYNOPSIS
31.Nm
32.Op Fl n
33.Op Fl i Op Ar identity_file
34.Op Fl p Ar port
35.Op Fl o Ar ssh_option
36.Op Ar user Ns @ Ns
37.Ar hostname
38.Nm
39.Fl h | Fl ?
25.br 40.br
26.SH DESCRIPTION 41.Sh DESCRIPTION
27.BR ssh-copy-id 42.Nm
28is a script that uses ssh to log into a remote machine and 43is a script that uses
29append the indicated identity file to that machine's 44.Xr ssh 1
30.B ~/.ssh/authorized_keys 45to log into a remote machine (presumably using a login password,
31file. 46so password authentication should be enabled, unless you've done some
32.PP 47clever use of multiple identities). It assembles a list of one or more
33If the 48fingerprints (as described below) and tries to log in with each key, to
34.B -i 49see if any of them are already installed (of course, if you are not using
35option is given then the identity file (defaults to 50.Xr ssh-agent 1
36.BR ~/.ssh/id_rsa.pub ) 51this may result in you being repeatedly prompted for pass-phrases).
37is used, regardless of whether there are any keys in your 52It then assembles a list of those that failed to log in, and using ssh,
38.BR ssh-agent . 53enables logins with those keys on the remote server. By default it adds
39Otherwise, if this: 54the keys by appending them to the remote user's
40.PP 55.Pa ~/.ssh/authorized_keys
41.B " ssh-add -L" 56(creating the file, and directory, if necessary). It is also capable
42.PP 57of detecting if the remote system is a NetScreen, and using its
43provides any output, it uses that in preference to the identity file. 58.Ql set ssh pka-dsa key ...
44.PP 59command instead.
45If the 60.Pp
46.B -i 61The options are as follows:
47option is used, or the 62.Bl -tag -width Ds
48.B ssh-add 63.It Fl i Ar identity_file
49produced no output, then it uses the contents of the identity 64Use only the key(s) contained in
50file. Once it has one or more fingerprints (by whatever means) it 65.Ar identity_file
51uses ssh to append them to 66(rather than looking for identities via
52.B ~/.ssh/authorized_keys 67.Xr ssh-add 1
53on the remote machine (creating the file, and directory, if necessary.) 68or in the
54 69.Ic default_ID_file ) .
55.SH NOTES 70If the filename does not end in
56This program does not modify the permissions of any 71.Pa .pub
57pre-existing files or directories. Therefore, if the remote 72this is added. If the filename is omitted, the
58.B sshd 73.Ic default_ID_file
59has 74is used.
60.B StrictModes 75.Pp
61set in its 76Note that this can be used to ensure that the keys copied have the
62configuration, then the user's home, 77comment one prefers and/or extra options applied, by ensuring that the
63.B ~/.ssh 78key file has these set as preferred before the copy is attempted.
64folder, and 79.It Fl n
65.B ~/.ssh/authorized_keys 80do a dry-run. Instead of installing keys on the remote system simply
66file may need to have group writability disabled manually, e.g. via 81prints the key(s) that would have been installed.
67 82.It Fl h , Fl ?
68.B " chmod go-w ~ ~/.ssh ~/.ssh/authorized_keys" 83Print Usage summary
69 84.It Fl p Ar port , Fl o Ar ssh_option
70on the remote machine. 85These two options are simply passed through untouched, along with their
71 86argument, to allow one to set the port or other
72.SH "SEE ALSO" 87.Xr ssh 1
73.BR ssh (1), 88options, respectively.
74.BR ssh-agent (1), 89.Pp
75.BR sshd (8) 90Rather than specifying these as command line options, it is often better to use (per-host) settings in
91.Xr ssh 1 Ns 's
92configuration file:
93.Xr ssh_config 5 .
94.El
95.Pp
96Default behaviour without
97.Fl i ,
98is to check if
99.Ql ssh-add -L
100provides any output, and if so those keys are used. Note that this results in
101the comment on the key being the filename that was given to
102.Xr ssh-add 1
103when the key was loaded into your
104.Xr ssh-agent 1
105rather than the comment contained in that file, which is a bit of a shame.
106Otherwise, if
107.Xr ssh-add 1
108provides no keys contents of the
109.Ic default_ID_file
110will be used.
111.Pp
112The
113.Ic default_ID_file
114is the most recent file that matches:
115.Pa ~/.ssh/id*.pub ,
116(excluding those that match
117.Pa ~/.ssh/*-cert.pub )
118so if you create a key that is not the one you want
119.Nm
120to use, just use
121.Xr touch 1
122on your preferred key's
123.Pa .pub
124file to reinstate it as the most recent.
125.Pp
126.Sh EXAMPLES
127If you have already installed keys from one system on a lot of remote
128hosts, and you then create a new key, on a new client machine, say,
129it can be difficult to keep track of which systems on which you've
130installed the new key. One way of dealing with this is to load both
131the new key and old key(s) into your
132.Xr ssh-agent 1 .
133Load the new key first, without the
134.Fl c
135option, then load one or more old keys into the agent, possibly by
136ssh-ing to the client machine that has that old key, using the
137.Fl A
138option to allow agent forwarding:
139.Pp
140.D1 user@newclient$ ssh-add
141.D1 user@newclient$ ssh -A old.client
142.D1 user@oldl$ ssh-add -c
143.D1 No ... prompt for pass-phrase ...
144.D1 user@old$ logoff
145.D1 user@newclient$ ssh someserver
146.Pp
147now, if the new key is installed on the server, you'll be allowed in
148unprompted, whereas if you only have the old key(s) enabled, you'll be
149asked for confirmation, which is your cue to log back out and run
150.Pp
151.D1 user@newclient$ ssh-copy-id -i someserver
152.Pp
153The reason you might want to specify the -i option in this case is to
154ensure that the comment on the installed key is the one from the
155.Pa .pub
156file, rather than just the filename that was loaded into you agent.
157It also ensures that only the id you intended is installed, rather than
158all the keys that you have in your
159.Xr ssh-agent 1 .
160Of course, you can specify another id, or use the contents of the
161.Xr ssh-agent 1
162as you prefer.
163.Pp
164Having mentioned
165.Xr ssh-add 1 Ns 's
166.Fl c
167option, you might consider using this whenever using agent forwarding
168to avoid your key being hijacked, but it is much better to instead use
169.Xr ssh 1 Ns 's
170.Ar ProxyCommand
171and
172.Fl W
173option,
174to bounce through remote servers while always doing direct end-to-end
175authentication. This way the middle hop(s) don't get access to your
176.Xr ssh-agent 1 .
177A web search for
178.Ql ssh proxycommand nc
179should prove enlightening (N.B. the modern approach is to use the
180.Fl W
181option, rather than
182.Xr nc 1 ) .
183.Sh "SEE ALSO"
184.Xr ssh 1 ,
185.Xr ssh-agent 1 ,
186.Xr sshd 8