source: postlfs/security/openssh.xml@ 7969f18

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Last change on this file since 7969f18 was 02cb684, checked in by Pierre Labastie <pierre.labastie@…>, 2 years ago

Update to openssh-8.9p1 with ssh-askpass
  • Property mode set to 100644
File size: 18.8 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 "f33910174f0af52491277211e2b105bb">
13 <!ENTITY openssh-size "1.7 MB">
14 <!ENTITY openssh-buildsize "52 MB (add 20 MB for tests)">
15 <!ENTITY openssh-time "0.3 SBU (Using parallelism=4;
16 running the tests takes c.a. 25 minutes,
17 irrespective of processor speed)">
18]>
19
20<sect1 id="openssh" xreflabel="OpenSSH-&openssh-version;">
21 <?dbhtml filename="openssh.html"?>
22
23 <sect1info>
24 <date>$Date$</date>
25 </sect1info>
26
27 <title>OpenSSH-&openssh-version;</title>
28
29 <indexterm zone="openssh">
30 <primary sortas="a-OpenSSH">OpenSSH</primary>
31 </indexterm>
32
33 <sect2 role="package">
34 <title>Introduction to OpenSSH</title>
35
36 <para>
37 The <application>OpenSSH</application> package contains
38 <command>ssh</command> clients and the <command>sshd</command> daemon.
39 This is useful for encrypting authentication and subsequent traffic over
40 a network. The <command>ssh</command> and <command>scp</command> commands
41 are secure implementations of <command>telnet</command> and
42 <command>rcp</command> respectively.
43 </para>
44
45 &lfs111_checked;
46
47 <bridgehead renderas="sect3">Package Information</bridgehead>
48 <itemizedlist spacing="compact">
49 <listitem>
50 <para>
51 Download (HTTP): <ulink url="&openssh-download-http;"/>
52 </para>
53 </listitem>
54 <listitem>
55 <para>
56 Download (FTP): <ulink url="&openssh-download-ftp;"/>
57 </para>
58 </listitem>
59 <listitem>
60 <para>
61 Download MD5 sum: &openssh-md5sum;
62 </para>
63 </listitem>
64 <listitem>
65 <para>
66 Download size: &openssh-size;
67 </para>
68 </listitem>
69 <listitem>
70 <para>
71 Estimated disk space required: &openssh-buildsize;
72 </para>
73 </listitem>
74 <listitem>
75 <para>
76 Estimated build time: &openssh-time;
77 </para>
78 </listitem>
79 </itemizedlist>
80<!--
81 <bridgehead renderas="sect3">Additional Downloads</bridgehead>
82 <itemizedlist spacing="compact">
83 <listitem>
84 <para>
85 Required patch:
86 <ulink url="&patch-root;/openssh-&openssh-version;-glibc_2.31_fix-1.patch"/>
87 </para>
88 </listitem>
89 </itemizedlist>
90-->
91 <bridgehead renderas="sect3">OpenSSH Dependencies</bridgehead>
92
93 <bridgehead renderas="sect4">Optional</bridgehead>
94 <para role="optional">
95 <xref linkend="gdb"/> (for tests),
96 <xref linkend="linux-pam"/>,
97 <xref linkend="x-window-system"/>,
98 <xref linkend="mitkrb"/>,
99 <ulink url="http://www.thrysoee.dk/editline/">libedit</ulink>,
100 <ulink url="http://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<screen><userinput>./configure --prefix=/usr \
172 --sysconfdir=/etc/ssh \
173 --with-privsep-path=/var/lib/sshd \
174 --with-default-path=/usr/bin \
175 --with-superuser-path=/usr/sbin:/usr/bin \
176 --with-pid-dir=/run &amp;&amp;
177<!-- -\-with-md5-passwords \ -->
178
179make</userinput></screen>
180
181 <para>
182 The testsuite 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
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 <para>
243 <parameter>--with-md5-passwords</parameter>: This enables the use of MD5
244 passwords.
245 </para>
246
247 <para>
248 <parameter>--with-default-path=/usr/bin</parameter> and
249 <parameter>--with-superuser-path=/usr/sbin:/usr/bin</parameter>:
250 These set <envar>PATH</envar> consistent with LFS and BLFS
251 <application>Shadow</application> package.
252 </para>
253
254 <para>
255 <parameter>--with-pid-dir=/run</parameter>: This prevents
256 <application>OpenSSH</application> from referring to deprecated
257 <filename class="directory">/var/run</filename>.
258 </para>
259
260 <para>
261 <option>--with-pam</option>: This parameter enables
262 <application>Linux-PAM</application> support in the build.
263 </para>
264
265 <para>
266 <option>--with-xauth=/usr/bin/xauth</option>: Set the default
267 location for the <command>xauth</command> binary for X authentication.
268 Change the location if <command>xauth</command> will be installed to a
269 different path. This can also be controlled from
270 <filename>sshd_config</filename> with the XAuthLocation keyword. You can
271 omit this switch if <application>Xorg</application> is already installed.
272 </para>
273
274 <para>
275 <option>--with-kerberos5=/usr</option>: This option is used to
276 include Kerberos 5 support in the build.
277 </para>
278
279 <para>
280 <option>--with-libedit</option>: This option enables line editing
281 and history features for <command>sftp</command>.
282 </para>
283
284 </sect2>
285
286 <sect2 role="configuration">
287 <title>Configuring OpenSSH</title>
288
289 <sect3 id="openssh-config">
290 <title>Config Files</title>
291
292 <para>
293 <filename>~/.ssh/*</filename>,
294 <filename>/etc/ssh/ssh_config</filename>, and
295 <filename>/etc/ssh/sshd_config</filename>
296 </para>
297
298 <indexterm zone="openssh openssh-config">
299 <primary sortas="e-AA.ssh">~/.ssh/*</primary>
300 </indexterm>
301
302 <indexterm zone="openssh openssh-config">
303 <primary sortas="e-etc-ssh-ssh_config">/etc/ssh/ssh_config</primary>
304 </indexterm>
305
306 <indexterm zone="openssh openssh-config">
307 <primary sortas="e-etc-ssh-sshd_config">/etc/ssh/sshd_config</primary>
308 </indexterm>
309
310 <para>
311 There are no required changes to any of these files. However,
312 you may wish to view the
313 <filename class='directory'>/etc/ssh/</filename> files and make any
314 changes appropriate for the security of your system. One recommended
315 change is that you disable
316 <systemitem class='username'>root</systemitem> login via
317 <command>ssh</command>. Execute the following command as the
318 <systemitem class='username'>root</systemitem> user to disable
319 <systemitem class='username'>root</systemitem> login via
320 <command>ssh</command>:
321 </para>
322
323<screen role="root"><userinput>echo "PermitRootLogin no" &gt;&gt; /etc/ssh/sshd_config</userinput></screen>
324
325 <para>
326 If you want to be able to log in without typing in your password, first
327 create ~/.ssh/id_rsa and ~/.ssh/id_rsa.pub with
328 <command>ssh-keygen</command> and then copy ~/.ssh/id_rsa.pub to
329 ~/.ssh/authorized_keys on the remote computer that you want to log into.
330 You'll need to change REMOTE_USERNAME and REMOTE_HOSTNAME for the username and hostname of the remote
331 computer and you'll also need to enter your password for the ssh-copy-id command
332 to succeed:
333 </para>
334
335<screen><userinput>ssh-keygen &amp;&amp;
336ssh-copy-id -i ~/.ssh/id_rsa.pub <replaceable>REMOTE_USERNAME</replaceable>@<replaceable>REMOTE_HOSTNAME</replaceable></userinput></screen>
337
338 <para>
339 Once you've got passwordless logins working it's actually more secure
340 than logging in with a password (as the private key is much longer than
341 most people's passwords). If you would like to now disable password
342 logins, as the <systemitem class="username">root</systemitem> user:
343 </para>
344
345
346<screen role="root"><userinput>echo "PasswordAuthentication no" >> /etc/ssh/sshd_config &amp;&amp;
347echo "ChallengeResponseAuthentication no" >> /etc/ssh/sshd_config</userinput></screen>
348
349 <para>
350 If you added <application>Linux-PAM</application> support and you want
351 ssh to use it then you will need to add a configuration file for
352 <application>sshd</application> and enable use of
353 <application>LinuxPAM</application>. Note, ssh only uses PAM to check
354 passwords, if you've disabled password logins these commands are not
355 needed. If you want to use PAM, issue the following commands as the
356 <systemitem class='username'>root</systemitem> user:
357 </para>
358
359<screen role="root"><userinput>sed 's@d/login@d/sshd@g' /etc/pam.d/login &gt; /etc/pam.d/sshd &amp;&amp;
360chmod 644 /etc/pam.d/sshd &amp;&amp;
361echo "UsePAM yes" &gt;&gt; /etc/ssh/sshd_config</userinput></screen>
362
363 <para>
364 Additional configuration information can be found in the man
365 pages for <command>sshd</command>, <command>ssh</command> and
366 <command>ssh-agent</command>.
367 </para>
368 </sect3>
369
370 <sect3 id="openssh-init">
371 <title><phrase revision="sysv">Boot Script</phrase>
372 <phrase revision="systemd">Systemd Unit</phrase></title>
373
374 <para revision="sysv">
375 To start the SSH server at system boot, install the
376 <filename>/etc/rc.d/init.d/sshd</filename> init script included
377 in the <xref linkend="bootscripts"/> package.
378 </para>
379
380 <para revision="systemd">
381 To start the SSH server at system boot, install the
382 <filename>sshd.service</filename> unit included in the
383 <xref linkend="systemd-units"/> package.
384 </para>
385
386 <indexterm zone="openssh openssh-init">
387 <primary sortas="f-sshd">sshd</primary>
388 </indexterm>
389
390<screen role="root"><userinput>make install-sshd</userinput></screen>
391 </sect3>
392 </sect2>
393
394 <sect2 role="content">
395 <title>Contents</title>
396
397 <segmentedlist>
398 <segtitle>Installed Programs</segtitle>
399 <segtitle>Installed Libraries</segtitle>
400 <segtitle>Installed Directories</segtitle>
401
402 <seglistitem>
403 <seg>
404 scp, sftp, <!--slogin (symlink to ssh),--> ssh, ssh-add, ssh-agent,
405 ssh-copy-id, ssh-keygen, ssh-keyscan, and sshd
406 </seg>
407 <seg>
408 None
409 </seg>
410 <seg>
411 /etc/ssh,
412 /usr/share/doc/openssh-&openssh-version;, and
413 /var/lib/sshd
414 </seg>
415 </seglistitem>
416 </segmentedlist>
417
418 <variablelist>
419 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
420 <?dbfo list-presentation="list"?>
421 <?dbhtml list-presentation="table"?>
422
423 <varlistentry id="scp">
424 <term><command>scp</command></term>
425 <listitem>
426 <para>
427 is a file copy program that acts like <command>rcp</command> except
428 it uses an encrypted protocol
429 </para>
430 <indexterm zone="openssh scp">
431 <primary sortas="b-scp">scp</primary>
432 </indexterm>
433 </listitem>
434 </varlistentry>
435
436 <varlistentry id="sftp">
437 <term><command>sftp</command></term>
438 <listitem>
439 <para>
440 is an FTP-like program that works over the SSH1 and SSH2 protocols
441 </para>
442 <indexterm zone="openssh sftp">
443 <primary sortas="b-sftp">sftp</primary>
444 </indexterm>
445 </listitem>
446 </varlistentry>
447<!-- Not installed anymore as of 8.5p1
448 <varlistentry id="slogin">
449 <term><command>slogin</command></term>
450 <listitem>
451 <para>
452 is a symlink to <command>ssh</command>
453 </para>
454 <indexterm zone="openssh slogin">
455 <primary sortas="b-slogin">slogin</primary>
456 </indexterm>
457 </listitem>
458 </varlistentry>
459-->
460 <varlistentry id="ssh">
461 <term><command>ssh</command></term>
462 <listitem>
463 <para>
464 is an <command>rlogin</command>/<command>rsh</command>-like client
465 program except it uses an encrypted protocol
466 </para>
467 <indexterm zone="openssh ssh">
468 <primary sortas="b-ssh">ssh</primary>
469 </indexterm>
470 </listitem>
471 </varlistentry>
472
473 <varlistentry id="sshd">
474 <term><command>sshd</command></term>
475 <listitem>
476 <para>
477 is a daemon that listens for <command>ssh</command> login requests
478 </para>
479 <indexterm zone="openssh sshd">
480 <primary sortas="b-sshd">sshd</primary>
481 </indexterm>
482 </listitem>
483 </varlistentry>
484
485 <varlistentry id="ssh-add">
486 <term><command>ssh-add</command></term>
487 <listitem>
488 <para>
489 is a tool which adds keys to the <command>ssh-agent</command>
490 </para>
491 <indexterm zone="openssh ssh-add">
492 <primary sortas="b-ssh-add">ssh-add</primary>
493 </indexterm>
494 </listitem>
495 </varlistentry>
496
497 <varlistentry id="ssh-agent">
498 <term><command>ssh-agent</command></term>
499 <listitem>
500 <para>
501 is an authentication agent that can store private keys
502 </para>
503 <indexterm zone="openssh ssh-agent">
504 <primary sortas="b-ssh-agent">ssh-agent</primary>
505 </indexterm>
506 </listitem>
507 </varlistentry>
508
509 <varlistentry id="ssh-copy-id">
510 <term><command>ssh-copy-id</command></term>
511 <listitem>
512 <para>
513 is a script that enables logins on remote machines using local keys
514 </para>
515 <indexterm zone="openssh ssh-copy-id">
516 <primary sortas="b-ssh-copy-id">ssh-copy-id</primary>
517 </indexterm>
518 </listitem>
519 </varlistentry>
520
521 <varlistentry id="ssh-keygen">
522 <term><command>ssh-keygen</command></term>
523 <listitem>
524 <para>
525 is a key generation tool
526 </para>
527 <indexterm zone="openssh ssh-keygen">
528 <primary sortas="b-ssh-keygen">ssh-keygen</primary>
529 </indexterm>
530 </listitem>
531 </varlistentry>
532
533 <varlistentry id="ssh-keyscan">
534 <term><command>ssh-keyscan</command></term>
535 <listitem>
536 <para>
537 is a utility for gathering public host keys from a number of hosts
538 </para>
539 <indexterm zone="openssh ssh-keyscan">
540 <primary sortas="b-ssh-keyscan">ssh-keyscan</primary>
541 </indexterm>
542 </listitem>
543 </varlistentry>
544
545 </variablelist>
546 </sect2>
547
548</sect1>
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