source: postlfs/security/openssh.xml@ f8dd4ec

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Last change on this file since f8dd4ec was e628e070, checked in by Bruce Dubbs <bdubbs@…>, 15 months ago

Update to openssh-9.3p1.
  • Property mode set to 100644
File size: 19.0 KB
Line 
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 "https://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable/openssh-&openssh-version;.tar.gz">
9 <!ENTITY openssh-download-ftp
10 " "> <!-- at the moment, unable to connect via ftp: ken
11 "ftp://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable/openssh-&openssh-version;.tar.gz"> -->
12 <!ENTITY openssh-md5sum "&openssh-md5sum;">
13 <!ENTITY openssh-size "1.8 MB">
14 <!ENTITY openssh-buildsize "45 MB (add 22 MB for tests)">
15 <!ENTITY openssh-time "0.2 SBU (Using parallelism=4;
16 running the tests takes about 20 minutes,
17 irrespective of processor speed)">
18]>
19
20 <!-- make check: real 18m13.005s; 9.2p1 3 Feb 2023 -->
21 <!-- make check: real 18m08.654s; 9.3p1 17 Mar 2023 -->
22
23<sect1 id="openssh" xreflabel="OpenSSH-&openssh-version;">
24 <?dbhtml filename="openssh.html"?>
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.
38 This is useful for encrypting authentication and subsequent traffic over
39 a network. The <command>ssh</command> and <command>scp</command> commands
40 are secure implementations of <command>telnet</command> and
41 <command>rcp</command> respectively.
42 </para>
43
44 &lfs113_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">Additional Downloads</bridgehead>
81 <itemizedlist spacing="compact">
82 <listitem>
83 <para>
84 Required patch:
85 <ulink url="&patch-root;/openssh-&openssh-version;-glibc_2.31_fix-1.patch"/>
86 </para>
87 </listitem>
88 </itemizedlist>
89-->
90 <bridgehead renderas="sect3">OpenSSH Dependencies</bridgehead>
91
92 <bridgehead renderas="sect4">Optional</bridgehead>
93 <para role="optional">
94 <xref linkend="gdb"/> (for tests),
95 <xref linkend="linux-pam"/>,
96 <xref linkend="x-window-system"/>,
97 <xref linkend="mitkrb"/>,
98 <xref linkend="which"/> (for tests),
99 <ulink url="https://www.thrysoee.dk/editline/">libedit</ulink>,
100 <ulink url="https://www.libressl.org/">LibreSSL Portable</ulink>,
101 <ulink url="https://github.com/OpenSC/OpenSC/wiki">OpenSC</ulink>, and
102 <ulink url="http://www.citi.umich.edu/projects/smartcard/sectok.html">libsectok</ulink>
103 </para>
104
105 <bridgehead renderas="sect4">Optional Runtime (Used only to gather entropy)</bridgehead>
106 <para role="optional">
107 <!--<xref role="runtime" linkend="openjdk"/>, Not seen in 8.8p1 -->
108 <xref role="runtime" linkend="net-tools"/>, and
109 <xref role="runtime" linkend="sysstat"/>
110 </para>
111
112 <para condition="html" role="usernotes">
113 User Notes: <ulink url="&blfs-wiki;/OpenSSH"/>
114 </para>
115 </sect2>
116
117 <sect2 role="installation">
118 <title>Installation of OpenSSH</title>
119
120 <para>
121 <application>OpenSSH</application> runs as two processes when connecting
122 to other computers. The first process is a privileged process and controls
123 the issuance of privileges as necessary. The second process communicates
124 with the network. Additional installation steps are necessary to set up
125 the proper environment, which are performed by issuing the following
126 commands as the <systemitem class="username">root</systemitem> user:
127 </para>
128
129<screen role="root"><userinput>install -v -m700 -d /var/lib/sshd &amp;&amp;
130chown -v root:sys /var/lib/sshd &amp;&amp;
131
132groupadd -g 50 sshd &amp;&amp;
133useradd -c 'sshd PrivSep' \
134 -d /var/lib/sshd \
135 -g sshd \
136 -s /bin/false \
137 -u 50 sshd</userinput></screen>
138<!--
139 <para>
140 Apply a patch to allow OpenSSH to build and function with
141 <application>Glibc-2.31</application> and later:
142 </para>
143
144<screen><userinput remap="pre">patch -Np1 -i ../openssh-&openssh-version;-glibc_2.31_fix-1.patch</userinput></screen>
145-->
146
147<!-- Applied in 8.5p1
148 <para>
149 First, adapt <application>ssh-copy-id</application> to changes
150 in bash-5.1:
151 </para>
152
153<screen><userinput remap="pre">sed -e '/INSTALLKEYS_SH/s/)//' -e '260a\ )' -i contrib/ssh-copy-id</userinput></screen>
154
155 <para>
156 Next, fix an issue on platforms other than x86_64:
157 </para>
158 <screen><userinput remap="pre">if [ "$(uname -m)" != "x86_64" ]; then
159 l1="#ifdef __NR_pselect6_time64"
160 l2=" SC_ALLOW(__NR_pselect6_time64),"
161 l3="#endif"
162 sed -e "/^#ifdef __NR_read$/ i $l1\n$l2\n$l3" \
163 -i sandbox-seccomp-filter.c
164fi</userinput></screen>
165-->
166 <para>
167 Install <application>OpenSSH</application> by running the following
168 commands:
169 </para>
170
171<!-- -\-with-md5-passwords used to be here, but a comment inside of a <screen>
172 block leaves an eyesore. -->
173<screen><userinput>./configure --prefix=/usr \
174 --sysconfdir=/etc/ssh \
175 --with-privsep-path=/var/lib/sshd \
176 --with-default-path=/usr/bin \
177 --with-superuser-path=/usr/sbin:/usr/bin \
178 --with-pid-dir=/run &amp;&amp;
179make</userinput></screen>
180
181 <para>
182 The test suite requires an installed copy of <command>scp</command> to
183 complete the multiplexing tests. To run the test suite, first copy the
184 <command>scp</command> program to
185 <filename class="directory">/usr/bin</filename>, making sure that you
186 backup any existing copy first.
187 </para>
188<!-- I got all tests passed without this with 9.0p1. Apr 13, 2022.
189 <para>
190 If you wish to run the tests, remove a test suite that is not valid on
191 Linux-based platforms:
192 </para>
193
194<screen><userinput>sed -i 's/conch-ciphers//' regress/Makefile</userinput></screen>
195-->
196 <para>
197 To test the results, issue: <command>make -j1 tests</command>.
198 <!--One test, <filename>key options</filename>, fails when run in chroot.-->
199 </para>
200
201<!-- commenting this, I get "all tests passed" [ ken ]
202 NB tests should be run as _user_ but the role in the comment is root
203
204 commenting [ bruce ]: There are a couple of tests that want root.
205 The log mentions that SUDO is not set. These skipped tests are
206 ignored and the end says 'all tests passed' even when not root
207
208 <para>
209 To run the test suite, issue the following commands:
210 </para>
211
212<screen role="root"><userinput>make tests 2&gt;&amp;1 | tee check.log
213grep FATAL check.log</userinput></screen>
214
215 <para>
216 If the above command produces no 'FATAL' errors, then proceed with the
217 installation, as the <systemitem class="username">root</systemitem> user:
218 </para>-->
219 <para>
220 Now, as the <systemitem class="username">root</systemitem> user:
221 </para>
222
223<screen role="root"><userinput>make install &amp;&amp;
224install -v -m755 contrib/ssh-copy-id /usr/bin &amp;&amp;
225
226install -v -m644 contrib/ssh-copy-id.1 \
227 /usr/share/man/man1 &amp;&amp;
228install -v -m755 -d /usr/share/doc/openssh-&openssh-version; &amp;&amp;
229install -v -m644 INSTALL LICENCE OVERVIEW README* \
230 /usr/share/doc/openssh-&openssh-version;</userinput></screen>
231 </sect2>
232
233 <sect2 role="commands">
234 <title>Command Explanations</title>
235
236 <para>
237 <parameter>--sysconfdir=/etc/ssh</parameter>: This prevents the
238 configuration files from being installed in
239 <filename class="directory">/usr/etc</filename>.
240 </para>
241
242 <!--
243 <para>
244 <parameter>-\-with-md5-passwords</parameter>: This enables the use of MD5
245 passwords.
246 </para>
247 -->
248
249 <para>
250 <parameter>--with-default-path=/usr/bin</parameter> and
251 <parameter>--with-superuser-path=/usr/sbin:/usr/bin</parameter>:
252 These set <envar>PATH</envar> consistent with LFS and BLFS
253 <application>Shadow</application> package.
254 </para>
255
256 <para>
257 <parameter>--with-pid-dir=/run</parameter>: This prevents
258 <application>OpenSSH</application> from referring to deprecated
259 <filename class="directory">/var/run</filename>.
260 </para>
261
262 <para>
263 <option>--with-pam</option>: This parameter enables
264 <application>Linux-PAM</application> support in the build.
265 </para>
266
267 <para>
268 <option>--with-xauth=/usr/bin/xauth</option>: Set the default
269 location for the <command>xauth</command> binary for X authentication.
270 Change the location if <command>xauth</command> will be installed to a
271 different path. This can also be controlled from
272 <filename>sshd_config</filename> with the XAuthLocation keyword. You can
273 omit this switch if <application>Xorg</application> is already installed.
274 </para>
275
276 <para>
277 <option>--with-kerberos5=/usr</option>: This option is used to
278 include Kerberos 5 support in the build.
279 </para>
280
281 <para>
282 <option>--with-libedit</option>: This option enables line editing
283 and history features for <command>sftp</command>.
284 </para>
285
286 </sect2>
287
288 <sect2 role="configuration">
289 <title>Configuring OpenSSH</title>
290
291 <sect3 id="openssh-config">
292 <title>Config Files</title>
293
294 <para>
295 <filename>~/.ssh/*</filename>,
296 <filename>/etc/ssh/ssh_config</filename>, and
297 <filename>/etc/ssh/sshd_config</filename>
298 </para>
299
300 <indexterm zone="openssh openssh-config">
301 <primary sortas="e-AA.ssh">~/.ssh/*</primary>
302 </indexterm>
303
304 <indexterm zone="openssh openssh-config">
305 <primary sortas="e-etc-ssh-ssh_config">/etc/ssh/ssh_config</primary>
306 </indexterm>
307
308 <indexterm zone="openssh openssh-config">
309 <primary sortas="e-etc-ssh-sshd_config">/etc/ssh/sshd_config</primary>
310 </indexterm>
311
312 <para>
313 There are no required changes to any of these files. However,
314 you may wish to view the
315 <filename class='directory'>/etc/ssh/</filename> files and make any
316 changes appropriate for the security of your system. One recommended
317 change is that you disable
318 <systemitem class='username'>root</systemitem> login via
319 <command>ssh</command>. Execute the following command as the
320 <systemitem class='username'>root</systemitem> user to disable
321 <systemitem class='username'>root</systemitem> login via
322 <command>ssh</command>:
323 </para>
324
325<screen role="root"><userinput>echo "PermitRootLogin no" &gt;&gt; /etc/ssh/sshd_config</userinput></screen>
326
327 <para>
328 If you want to be able to log in without typing in your password, first
329 create ~/.ssh/id_rsa and ~/.ssh/id_rsa.pub with
330 <command>ssh-keygen</command> and then copy ~/.ssh/id_rsa.pub to
331 ~/.ssh/authorized_keys on the remote computer that you want to log into.
332 You'll need to change REMOTE_USERNAME and REMOTE_HOSTNAME for the username and hostname of the remote
333 computer and you'll also need to enter your password for the ssh-copy-id command
334 to succeed:
335 </para>
336
337<screen><userinput>ssh-keygen &amp;&amp;
338ssh-copy-id -i ~/.ssh/id_rsa.pub <replaceable>REMOTE_USERNAME</replaceable>@<replaceable>REMOTE_HOSTNAME</replaceable></userinput></screen>
339
340 <para>
341 Once you've got passwordless logins working it's actually more secure
342 than logging in with a password (as the private key is much longer than
343 most people's passwords). If you would like to now disable password
344 logins, as the <systemitem class="username">root</systemitem> user:
345 </para>
346
347
348<screen role="root"><userinput>echo "PasswordAuthentication no" >> /etc/ssh/sshd_config &amp;&amp;
349echo "KbdInteractiveAuthentication no" >> /etc/ssh/sshd_config</userinput></screen>
350
351 <para>
352 If you added <application>Linux-PAM</application> support and you want
353 ssh to use it then you will need to add a configuration file for
354 <application>sshd</application> and enable use of
355 <application>LinuxPAM</application>. Note, ssh only uses PAM to check
356 passwords, if you've disabled password logins these commands are not
357 needed. If you want to use PAM, issue the following commands as the
358 <systemitem class='username'>root</systemitem> user:
359 </para>
360
361<screen role="root"><userinput>sed 's@d/login@d/sshd@g' /etc/pam.d/login &gt; /etc/pam.d/sshd &amp;&amp;
362chmod 644 /etc/pam.d/sshd &amp;&amp;
363echo "UsePAM yes" &gt;&gt; /etc/ssh/sshd_config</userinput></screen>
364
365 <para>
366 Additional configuration information can be found in the man
367 pages for <command>sshd</command>, <command>ssh</command> and
368 <command>ssh-agent</command>.
369 </para>
370 </sect3>
371
372 <sect3 id="openssh-init">
373 <title><phrase revision="sysv">Boot Script</phrase>
374 <phrase revision="systemd">Systemd Unit</phrase></title>
375
376 <para revision="sysv">
377 To start the SSH server at system boot, install the
378 <filename>/etc/rc.d/init.d/sshd</filename> init script included
379 in the <xref linkend="bootscripts"/> package.
380 </para>
381
382 <para revision="systemd">
383 To start the SSH server at system boot, install the
384 <filename>sshd.service</filename> unit included in the
385 <xref linkend="systemd-units"/> package.
386 </para>
387
388 <indexterm zone="openssh openssh-init">
389 <primary sortas="f-sshd">sshd</primary>
390 </indexterm>
391
392<screen role="root"><userinput>make install-sshd</userinput></screen>
393 </sect3>
394 </sect2>
395
396 <sect2 role="content">
397 <title>Contents</title>
398
399 <segmentedlist>
400 <segtitle>Installed Programs</segtitle>
401 <segtitle>Installed Libraries</segtitle>
402 <segtitle>Installed Directories</segtitle>
403
404 <seglistitem>
405 <seg>
406 scp, sftp, <!--slogin (symlink to ssh),--> ssh, ssh-add, ssh-agent,
407 ssh-copy-id, ssh-keygen, ssh-keyscan, and sshd
408 </seg>
409 <seg>
410 None
411 </seg>
412 <seg>
413 /etc/ssh,
414 /usr/share/doc/openssh-&openssh-version;, and
415 /var/lib/sshd
416 </seg>
417 </seglistitem>
418 </segmentedlist>
419
420 <variablelist>
421 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
422 <?dbfo list-presentation="list"?>
423 <?dbhtml list-presentation="table"?>
424
425 <varlistentry id="scp">
426 <term><command>scp</command></term>
427 <listitem>
428 <para>
429 is a file copy program that acts like <command>rcp</command> except
430 it uses an encrypted protocol
431 </para>
432 <indexterm zone="openssh scp">
433 <primary sortas="b-scp">scp</primary>
434 </indexterm>
435 </listitem>
436 </varlistentry>
437
438 <varlistentry id="sftp">
439 <term><command>sftp</command></term>
440 <listitem>
441 <para>
442 is an FTP-like program that works over the SSH1 and SSH2 protocols
443 </para>
444 <indexterm zone="openssh sftp">
445 <primary sortas="b-sftp">sftp</primary>
446 </indexterm>
447 </listitem>
448 </varlistentry>
449<!-- Not installed anymore as of 8.5p1
450 <varlistentry id="slogin">
451 <term><command>slogin</command></term>
452 <listitem>
453 <para>
454 is a symlink to <command>ssh</command>
455 </para>
456 <indexterm zone="openssh slogin">
457 <primary sortas="b-slogin">slogin</primary>
458 </indexterm>
459 </listitem>
460 </varlistentry>
461-->
462 <varlistentry id="ssh">
463 <term><command>ssh</command></term>
464 <listitem>
465 <para>
466 is an <command>rlogin</command>/<command>rsh</command>-like client
467 program except it uses an encrypted protocol
468 </para>
469 <indexterm zone="openssh ssh">
470 <primary sortas="b-ssh">ssh</primary>
471 </indexterm>
472 </listitem>
473 </varlistentry>
474
475 <varlistentry id="sshd">
476 <term><command>sshd</command></term>
477 <listitem>
478 <para>
479 is a daemon that listens for <command>ssh</command> login requests
480 </para>
481 <indexterm zone="openssh sshd">
482 <primary sortas="b-sshd">sshd</primary>
483 </indexterm>
484 </listitem>
485 </varlistentry>
486
487 <varlistentry id="ssh-add">
488 <term><command>ssh-add</command></term>
489 <listitem>
490 <para>
491 is a tool which adds keys to the <command>ssh-agent</command>
492 </para>
493 <indexterm zone="openssh ssh-add">
494 <primary sortas="b-ssh-add">ssh-add</primary>
495 </indexterm>
496 </listitem>
497 </varlistentry>
498
499 <varlistentry id="ssh-agent">
500 <term><command>ssh-agent</command></term>
501 <listitem>
502 <para>
503 is an authentication agent that can store private keys
504 </para>
505 <indexterm zone="openssh ssh-agent">
506 <primary sortas="b-ssh-agent">ssh-agent</primary>
507 </indexterm>
508 </listitem>
509 </varlistentry>
510
511 <varlistentry id="ssh-copy-id">
512 <term><command>ssh-copy-id</command></term>
513 <listitem>
514 <para>
515 is a script that enables logins on remote machines using local keys
516 </para>
517 <indexterm zone="openssh ssh-copy-id">
518 <primary sortas="b-ssh-copy-id">ssh-copy-id</primary>
519 </indexterm>
520 </listitem>
521 </varlistentry>
522
523 <varlistentry id="ssh-keygen">
524 <term><command>ssh-keygen</command></term>
525 <listitem>
526 <para>
527 is a key generation tool
528 </para>
529 <indexterm zone="openssh ssh-keygen">
530 <primary sortas="b-ssh-keygen">ssh-keygen</primary>
531 </indexterm>
532 </listitem>
533 </varlistentry>
534
535 <varlistentry id="ssh-keyscan">
536 <term><command>ssh-keyscan</command></term>
537 <listitem>
538 <para>
539 is a utility for gathering public host keys from a number of hosts
540 </para>
541 <indexterm zone="openssh ssh-keyscan">
542 <primary sortas="b-ssh-keyscan">ssh-keyscan</primary>
543 </indexterm>
544 </listitem>
545 </varlistentry>
546
547 </variablelist>
548 </sect2>
549
550</sect1>
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