source: postlfs/security/openssh.xml@ c0b5bba

gnome
Last change on this file since c0b5bba was c0b5bba, checked in by Christopher Gregory <cjg@…>, 10 years ago

Added systemd notes to libcap mitkrb openssh polkit and stunnel pages

git-svn-id: svn://svn.linuxfromscratch.org/BLFS/branches/gnome@13393 af4574ff-66df-0310-9fd7-8a98e5e911e0
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File size: 19.2 KB
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1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
4 <!ENTITY % general-entities SYSTEM "../../general.ent">
5 %general-entities;
6
7 <!ENTITY openssh-download-http
8 "http://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable/openssh-&openssh-version;.tar.gz">
9 <!ENTITY openssh-download-ftp
10 "ftp://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable/openssh-&openssh-version;.tar.gz">
11 <!ENTITY openssh-md5sum "3e9800e6bca1fbac0eea4d41baa7f239">
12 <!ENTITY openssh-size "1.3 MB">
13 <!ENTITY openssh-buildsize "32 MB (additional 2 MB if running the tests)">
14 <!ENTITY openssh-time "0.5 SBU (running the tests takes at least 10
15 minutes, irrespective of processor speed)">
16]>
17
18<sect1 id="openssh" xreflabel="OpenSSH-&openssh-version;">
19 <?dbhtml filename="openssh.html"?>
20
21 <sect1info>
22 <othername>$LastChangedBy$</othername>
23 <date>$Date$</date>
24 </sect1info>
25
26 <title>OpenSSH-&openssh-version;</title>
27
28 <indexterm zone="openssh">
29 <primary sortas="a-OpenSSH">OpenSSH</primary>
30 </indexterm>
31
32 <sect2 role="package">
33 <title>Introduction to OpenSSH</title>
34
35 <para>
36 The <application>OpenSSH</application> package contains
37 <command>ssh</command> clients and the <command>sshd</command> daemon. This
38 is useful for encrypting authentication and subsequent traffic over a
39 network. The <command>ssh</command> and <command>scp</command> commands are
40 secure implementions of <command>telnet</command> and <command>rcp</command>
41 respectively.
42 </para>
43
44 &lfs75_checked;
45
46 <bridgehead renderas="sect3">Package Information</bridgehead>
47 <itemizedlist spacing="compact">
48 <listitem>
49 <para>
50 Download (HTTP): <ulink url="&openssh-download-http;"/>
51 </para>
52 </listitem>
53 <listitem>
54 <para>
55 Download (FTP): <ulink url="&openssh-download-ftp;"/>
56 </para>
57 </listitem>
58 <listitem>
59 <para>
60 Download MD5 sum: &openssh-md5sum;
61 </para>
62 </listitem>
63 <listitem>
64 <para>
65 Download size: &openssh-size;
66 </para>
67 </listitem>
68 <listitem>
69 <para>
70 Estimated disk space required: &openssh-buildsize;
71 </para>
72 </listitem>
73 <listitem>
74 <para>
75 Estimated build time: &openssh-time;
76 </para>
77 </listitem>
78 </itemizedlist>
79
80 <bridgehead renderas="sect3">OpenSSH Dependencies</bridgehead>
81
82 <bridgehead renderas="sect4">Required</bridgehead>
83 <para role="required"><xref linkend="openssl"/></para>
84
85 <bridgehead renderas="sect4">Optional</bridgehead>
86 <para role="optional">
87 <xref linkend="linux-pam"/>,
88 <xref linkend="x-window-system"/>,
89 <xref linkend="mitkrb"/>,
90 <ulink url="http://www.thrysoee.dk/editline/">libedit</ulink>,
91 <ulink url="http://www.opensc-project.org/">OpenSC</ulink>, and
92 <ulink url="http://www.citi.umich.edu/projects/smartcard/sectok.html">libsectok</ulink>
93 </para>
94
95 <bridgehead renderas="sect4">Optional Runtime (Used only to gather entropy)</bridgehead>
96 <para role="optional">
97 <xref linkend="openjdk"/>,
98 <xref linkend="net-tools"/>, and
99 <xref linkend="sysstat"/>.
100 </para>
101
102 <para condition="html" role="usernotes">
103 User Notes: <ulink url="&blfs-wiki;/OpenSSH"/>
104 </para>
105 </sect2>
106
107 <sect2 role="installation">
108 <title>Installation of OpenSSH</title>
109
110 <para>
111 <application>OpenSSH</application> runs as two processes when connecting
112 to other computers. The first process is a privileged process and controls
113 the issuance of privileges as necessary. The second process communicates
114 with the network. Additional installation steps are necessary to set up
115 the proper environment, which are performed by issuing the following
116 commands as the <systemitem class="username">root</systemitem> user:
117 </para>
118
119<screen role="root"><userinput>install -v -m700 -d /var/lib/sshd &amp;&amp;
120chown -v root:sys /var/lib/sshd &amp;&amp;
121
122groupadd -g 50 sshd &amp;&amp;
123useradd -c 'sshd PrivSep' -d /var/lib/sshd -g sshd -s /bin/false -u 50 sshd</userinput></screen>
124
125 <para>
126 Install <application>OpenSSH</application> by running the following
127 commands:
128 </para>
129
130<screen><userinput>./configure --prefix=/usr \
131 --sysconfdir=/etc/ssh \
132 --with-md5-passwords \
133 --with-privsep-path=/var/lib/sshd &amp;&amp;
134make</userinput></screen>
135
136 <para>
137 The testsuite requires an installed copy of <command>scp</command> to
138 complete the multiplexing tests. To run the test suite, first copy the
139 <command>scp</command> program to
140 <filename class="directory">/usr/bin</filename>, making sure that you
141 back up any existing copy first.
142 </para>
143
144 <para>
145 To test the results, issue: <command>make tests</command>.
146 </para>
147
148<!-- commenting this, I get "all tests passed" [ ken ]
149 NB tests should be run as _user_ but the role in the comment is root
150
151 commenting [ bruce ]: There are a couple of tests that want root.
152 The log mentions that SUDO is not set. These skipped tests are
153 ignored and the end says 'all tests passed' even when not root
154
155 <para>
156 To run the test suite, issue the following commands:
157 </para>
158
159<screen role="root"><userinput>make tests 2&gt;&amp;1 | tee check.log
160grep FATAL check.log</userinput></screen>
161
162 <para>
163 If the above command produces no 'FATAL' errors, then proceed with the
164 installation, as the <systemitem class="username">root</systemitem> user:
165 </para>-->
166 <para>
167 Now, as the <systemitem class="username">root</systemitem> user:
168 </para>
169
170<screen role="root"><userinput>make install &amp;&amp;
171install -v -m755 contrib/ssh-copy-id /usr/bin &amp;&amp;
172install -v -m644 contrib/ssh-copy-id.1 /usr/share/man/man1 &amp;&amp;
173install -v -m755 -d /usr/share/doc/openssh-&openssh-version; &amp;&amp;
174install -v -m644 INSTALL LICENCE OVERVIEW README* /usr/share/doc/openssh-&openssh-version;</userinput></screen>
175 </sect2>
176
177 <sect2 role="commands">
178 <title>Command Explanations</title>
179
180 <para>
181 <parameter>--sysconfdir=/etc/ssh</parameter>: This prevents the
182 configuration files from being installed in
183 <filename class="directory">/usr/etc</filename>.
184 </para>
185
186 <para>
187 <parameter>--with-md5-passwords</parameter>: This enables the use of MD5
188 passwords.
189 </para>
190
191 <para>
192 <parameter>--with-pam</parameter>: This parameter enables
193 <application>Linux-PAM</application> support in the build.
194 </para>
195
196 <para>
197 <parameter>--with-xauth=/usr/bin/xauth</parameter>: Set the default
198 location for the <command>xauth</command> binary for X authentication.
199 Change the location if <command>xauth</command> will be installed to a
200 different path. This can also be controlled from
201 <filename>sshd_config</filename> with the XAuthLocation keyword. You can
202 omit this switch if <application>Xorg</application> is already installed.
203 </para>
204
205 <para>
206 <parameter>--with-kerberos5=/usr</parameter>: This option is used to
207 include Kerberos 5 support in the build.
208 </para>
209
210 <para>
211 <parameter>--with-libedit</parameter>: This option enables line editing
212 and history features for <command>sftp</command>.
213 </para>
214
215 </sect2>
216
217 <sect2 role="configuration">
218 <title>Configuring OpenSSH</title>
219
220 <sect3 id="openssh-config">
221 <title>Config Files</title>
222
223 <para>
224 <filename>~/.ssh/*</filename>,
225 <filename>/etc/ssh/ssh_config</filename>, and
226 <filename>/etc/ssh/sshd_config</filename>
227 </para>
228
229 <indexterm zone="openssh openssh-config">
230 <primary sortas="e-AA.ssh">~/.ssh/*</primary>
231 </indexterm>
232
233 <indexterm zone="openssh openssh-config">
234 <primary sortas="e-etc-ssh-ssh_config">/etc/ssh/ssh_config</primary>
235 </indexterm>
236
237 <indexterm zone="openssh openssh-config">
238 <primary sortas="e-etc-ssh-sshd_config">/etc/ssh/sshd_config</primary>
239 </indexterm>
240
241 <para>
242 There are no required changes to any of these files. However,
243 you may wish to view the
244 <filename class='directory'>/etc/ssh/</filename> files and make any
245 changes appropriate for the security of your system. One recommended
246 change is that you disable
247 <systemitem class='username'>root</systemitem> login via
248 <command>ssh</command>. Execute the following command as the
249 <systemitem class='username'>root</systemitem> user to disable
250 <systemitem class='username'>root</systemitem> login via
251 <command>ssh</command>:
252 </para>
253
254<screen role="root"><userinput>echo "PermitRootLogin no" &gt;&gt; /etc/ssh/sshd_config</userinput></screen>
255
256 <para>
257 If you want to be able to log in without typing in your password, first
258 create ~/.ssh/id_rsa and ~/.ssh/id_rsa.pub with
259 <command>ssh-keygen</command> and then copy ~/.ssh/id_rsa.pub to
260 ~/.ssh/authorized_keys on the remote computer that you want to log into.
261 You'll need to change REMOTE_HOSTNAME for the hostname of the remote
262 computer and you'll also need to enter you password for the ssh command
263 to succeed:
264 </para>
265
266<screen><userinput>ssh-keygen &amp;&amp;
267public_key="$(cat ~/.ssh/id_rsa.pub)" &amp;&amp;
268ssh REMOTE_HOSTNAME "echo ${public_key} &gt;&gt; ~/.ssh/authorized_keys" &amp;&amp;
269unset public_key</userinput></screen>
270
271 <para>
272 Once you've got passwordless logins working it's actually more secure
273 than logging in with a password (as the private key is much longer than
274 most people's passwords). If you would like to now disable password
275 logins, as the <systemitem class="username">root</systemitem> user:
276 </para>
277
278
279<screen role="root"><userinput>echo "PasswordAuthentication no" >> /etc/ssh/sshd_config &amp;&amp;
280echo "ChallengeResponseAuthentication no" >> /etc/ssh/sshd_config</userinput></screen>
281
282 <para>
283 If you added <application>LinuxPAM</application> support and you want
284 ssh to use it then you will need to add a configuration file for
285 <application>sshd</application> and enable use of
286 <application>LinuxPAM</application>. Note, ssh only uses PAM to check
287 passwords, if you've disabled password logins these commands are not
288 needed. If you want to use PAM issue the following commands as the
289 <systemitem class='username'>root</systemitem> user:
290 </para>
291
292<screen role="root"><userinput>sed 's@d/login@d/sshd@g' /etc/pam.d/login &gt; /etc/pam.d/sshd &amp;&amp;
293chmod 644 /etc/pam.d/sshd &amp;&amp;
294echo "UsePAM yes" &gt;&gt; /etc/ssh/sshd_config</userinput></screen>
295
296 <para>
297 Additional configuration information can be found in the man
298 pages for <command>sshd</command>, <command>ssh</command> and
299 <command>ssh-agent</command>.
300 </para>
301 </sect3>
302
303 <sect3 id="openssh-init">
304 <title>Boot Script</title>
305
306 <para>
307 To start the SSH server at system boot, install the
308 <filename>/etc/rc.d/init.d/sshd</filename> init script included
309 in the <xref linkend="bootscripts"/> package.
310 </para>
311
312 <indexterm zone="openssh openssh-init">
313 <primary sortas="f-sshd">sshd</primary>
314 </indexterm>
315
316<screen role="root"><userinput>make install-sshd</userinput></screen>
317 </sect3>
318
319 <sect3 id="openssh-init-systemd">
320 <title>Systemd Unit File</title>
321
322 <para>
323 Instead of using the classic boot script, the systemd-units package provides
324 native unit files. To start the SSH server at system boot, install the
325 systemd unit included in the <xref linkend="systemd-units"/> package.as the
326 <systemitem class="username">root</systemitem> user:
327 </para>
328
329 <indexterm zone="openssh openssh-init-systemd">
330 <primary sortas="f-sshd">sshd</primary>
331 </indexterm>
332
333<screen role="root"><userinput>make install-sshd</userinput></screen>
334
335 <note>
336 <para>
337 Note that this package comes with two types of units: A service file and a socket file.
338 The service file will start sshd daemon once at boot and it will keep running until the
339 system shuts down. The socket file will make systemd listen to sshd port (Default 22, needs
340 to be edited for anything else) and will start sshd daemon when something tries to connect
341 to that port and stop the daemon when the connection is terminated. This is
342 called socket activation.
343
344 By default, the first method is used - sshd daemon is started at boot and stopped at shutdown.
345 If the socket method is desired, you need to run as the <systemitem class="username">root</systemitem> user:
346
347
348<screen role="root">
349
350<userinput>
351
352systemctl stop sshd &amp;&amp;
353systemctl disable sshd.service &amp;&amp;
354systemctl enable sshd.socket &amp;&amp;
355systemctl start sshd.socket
356
357</userinput>
358</screen>
359
360 </para>
361 </note>
362 </sect3>
363
364 </sect2>
365
366 <sect2 role="content">
367 <title>Contents</title>
368
369 <segmentedlist>
370 <segtitle>Installed Programs</segtitle>
371 <segtitle>Installed Libraries</segtitle>
372 <segtitle>Installed Directories</segtitle>
373
374 <seglistitem>
375 <seg>
376 scp, sftp, sftp-server, slogin (symlink to ssh), ssh, sshd, ssh-add,
377 ssh-agent, ssh-copy-id, ssh-keygen, ssh-keyscan, ssh-keysign,
378 and ssh-pkcs11-helper
379 </seg>
380 <seg>
381 None
382 </seg>
383 <seg>
384 /etc/ssh,
385 /usr/libexec/openssh,
386 /usr/share/doc/openssh-&openssh-version;, and
387 /var/lib/sshd
388 </seg>
389 </seglistitem>
390 </segmentedlist>
391
392 <variablelist>
393 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
394 <?dbfo list-presentation="list"?>
395 <?dbhtml list-presentation="table"?>
396
397 <varlistentry id="scp">
398 <term><command>scp</command></term>
399 <listitem>
400 <para>
401 is a file copy program that acts like <command>rcp</command> except
402 it uses an encrypted protocol.
403 </para>
404 <indexterm zone="openssh scp">
405 <primary sortas="b-scp">scp</primary>
406 </indexterm>
407 </listitem>
408 </varlistentry>
409
410 <varlistentry id="sftp">
411 <term><command>sftp</command></term>
412 <listitem>
413 <para>
414 is an FTP-like program that works over the SSH1 and SSH2 protocols.
415 </para>
416 <indexterm zone="openssh sftp">
417 <primary sortas="b-sftp">sftp</primary>
418 </indexterm>
419 </listitem>
420 </varlistentry>
421
422 <varlistentry id="sftp-server">
423 <term><command>sftp-server</command></term>
424 <listitem>
425 <para>
426 is an SFTP server subsystem. This program is not normally called
427 directly by the user.
428 </para>
429 <indexterm zone="openssh sftp-server">
430 <primary sortas="b-sftp-server">sftp-server</primary>
431 </indexterm>
432 </listitem>
433 </varlistentry>
434
435 <varlistentry id="slogin">
436 <term><command>slogin</command></term>
437 <listitem>
438 <para>
439 is a symlink to <command>ssh</command>.
440 </para>
441 <indexterm zone="openssh slogin">
442 <primary sortas="b-slogin">slogin</primary>
443 </indexterm>
444 </listitem>
445 </varlistentry>
446
447 <varlistentry id="ssh">
448 <term><command>ssh</command></term>
449 <listitem>
450 <para>
451 is an <command>rlogin</command>/<command>rsh</command>-like client
452 program except it uses an encrypted protocol.
453 </para>
454 <indexterm zone="openssh ssh">
455 <primary sortas="b-ssh">ssh</primary>
456 </indexterm>
457 </listitem>
458 </varlistentry>
459
460 <varlistentry id="sshd">
461 <term><command>sshd</command></term>
462 <listitem>
463 <para>
464 is a daemon that listens for <command>ssh</command> login requests.
465 </para>
466 <indexterm zone="openssh sshd">
467 <primary sortas="b-sshd">sshd</primary>
468 </indexterm>
469 </listitem>
470 </varlistentry>
471
472 <varlistentry id="ssh-add">
473 <term><command>ssh-add</command></term>
474 <listitem>
475 <para>
476 is a tool which adds keys to the <command>ssh-agent</command>.
477 </para>
478 <indexterm zone="openssh ssh-add">
479 <primary sortas="b-ssh-add">ssh-add</primary>
480 </indexterm>
481 </listitem>
482 </varlistentry>
483
484 <varlistentry id="ssh-agent">
485 <term><command>ssh-agent</command></term>
486 <listitem>
487 <para>
488 is an authentication agent that can store private keys.
489 </para>
490 <indexterm zone="openssh ssh-agent">
491 <primary sortas="b-ssh-agent">ssh-agent</primary>
492 </indexterm>
493 </listitem>
494 </varlistentry>
495
496 <varlistentry id="ssh-copy-id">
497 <term><command>ssh-copy-id</command></term>
498 <listitem>
499 <para>
500 is a script that enables logins on remote machine using local keys.
501 </para>
502 <indexterm zone="openssh ssh-copy-id">
503 <primary sortas="b-ssh-copy-id">ssh-copy-id</primary>
504 </indexterm>
505 </listitem>
506 </varlistentry>
507
508 <varlistentry id="ssh-keygen">
509 <term><command>ssh-keygen</command></term>
510 <listitem>
511 <para>
512 is a key generation tool.
513 </para>
514 <indexterm zone="openssh ssh-keygen">
515 <primary sortas="b-ssh-keygen">ssh-keygen</primary>
516 </indexterm>
517 </listitem>
518 </varlistentry>
519
520 <varlistentry id="ssh-keyscan">
521 <term><command>ssh-keyscan</command></term>
522 <listitem>
523 <para>
524 is a utility for gathering public host keys from a number of hosts.
525 </para>
526 <indexterm zone="openssh ssh-keyscan">
527 <primary sortas="b-ssh-keyscan">ssh-keyscan</primary>
528 </indexterm>
529 </listitem>
530 </varlistentry>
531
532 <varlistentry id="ssh-keysign">
533 <term><command>ssh-keysign</command></term>
534 <listitem>
535 <para>
536 is used by <command>ssh</command> to access the local host keys and
537 generate the digital signature required during hostbased
538 authentication with SSH protocol version 2. This program is not
539 normally called directly by the user.
540 </para>
541 <indexterm zone="openssh ssh-keysign">
542 <primary sortas="b-ssh-keysign">ssh-keysign</primary>
543 </indexterm>
544 </listitem>
545 </varlistentry>
546
547 <varlistentry id="ssh-pkcs11-helper">
548 <term><command>ssh-pkcs11-helper</command></term>
549 <listitem>
550 <para>
551 is a <command>ssh-agent</command> helper program for PKCS#11 support.
552 </para>
553 <indexterm zone="openssh ssh-pkcs11-helper">
554 <primary sortas="b-ssh-pkcs11-helper">ssh-pkcs11-helper</primary>
555 </indexterm>
556 </listitem>
557 </varlistentry>
558
559 </variablelist>
560 </sect2>
561</sect1>
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