summaryrefslogtreecommitdiff
path: root/debian/openssh-server.postinst
blob: cf3fa68ea5ce05c30ae0991e3773f00f1ef827af (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
#!/bin/sh -e

action="$1"
oldversion="$2"

. /usr/share/debconf/confmodule
db_version 2.0

umask 022

if [ "$action" != configure ]
  then
  exit 0
fi


fix_doc_symlink() {
	if [ ! -L /usr/share/doc/openssh-server ] && \
	   dpkg --compare-versions "$oldversion" lt-nl 1:4.1p1-5; then
		rm -rf /usr/share/doc/openssh-server
		ln -s openssh-client /usr/share/doc/openssh-server
	fi
}


get_config_option() {
	option="$1"

	[ -f /etc/ssh/sshd_config ] || return

	# TODO: actually only one '=' allowed after option
	perl -lne 's/\s+/ /g; print if s/^\s*'"$option"'[[:space:]=]+//i' \
	   /etc/ssh/sshd_config
}


set_config_option() {
	option="$1"
	value="$2"

	perl -le '
		$option = $ARGV[0]; $value = $ARGV[1]; $done = 0;
		while (<STDIN>) {
			chomp;
			(my $match = $_) =~ s/\s+/ /g;
			if ($match =~ s/^\s*\Q$option\E\s+.*/$option $value/) {
				$_ = $match;
				$done = 1;
			}
			print;
		}
		print "$option $value" unless $done;' \
		"$option" "$value" \
		< /etc/ssh/sshd_config > /etc/ssh/sshd_config.dpkg-new
	chown --reference /etc/ssh/sshd_config /etc/ssh/sshd_config.dpkg-new
	chmod --reference /etc/ssh/sshd_config /etc/ssh/sshd_config.dpkg-new
	mv /etc/ssh/sshd_config.dpkg-new /etc/ssh/sshd_config
}


disable_config_option() {
	option="$1"

	value="$(get_config_option "$option")"
	[ "$value" ] || return 0

	perl -le '
		$option = $ARGV[0];
		while (<STDIN>) {
			chomp;
			(my $match = $_) =~ s/\s+/ /g;
			# TODO: actually only one "=" allowed after option
			if ($match =~ s/^(\s*\Q$option\E[[:space:]=]+.*)/#$1/i) {
				$_ = $match;
			}
			print;
		}' \
		"$option" \
		< /etc/ssh/sshd_config > /etc/ssh/sshd_config.dpkg-new
	chown --reference /etc/ssh/sshd_config /etc/ssh/sshd_config.dpkg-new
	chmod --reference /etc/ssh/sshd_config /etc/ssh/sshd_config.dpkg-new
	mv /etc/ssh/sshd_config.dpkg-new /etc/ssh/sshd_config
}


rename_config_option() {
	oldoption="$1"
	newoption="$2"

	value="$(get_config_option "$oldoption")"
	[ "$value" ] || return 0

	perl -le '
		$oldoption = $ARGV[0]; $newoption = $ARGV[1];
		while (<STDIN>) {
			chomp;
			(my $match = $_) =~ s/\s+/ /g;
			# TODO: actually only one "=" allowed after option
			if ($match =~ s/^(\s*)\Q$oldoption\E([[:space:]=]+)/$1$newoption$2/i) {
				$_ = $match;
			}
			print;
		}' \
		"$oldoption" "$newoption" \
		< /etc/ssh/sshd_config > /etc/ssh/sshd_config.dpkg-new
	chown --reference /etc/ssh/sshd_config /etc/ssh/sshd_config.dpkg-new
	chmod --reference /etc/ssh/sshd_config /etc/ssh/sshd_config.dpkg-new
	mv /etc/ssh/sshd_config.dpkg-new /etc/ssh/sshd_config
}


remove_obsolete_gssapi() {
	disable_config_option GSSAPINoMICAuthentication
	disable_config_option GSSUseSessionCCache
	disable_config_option GSSAPIUseSessionCredCache
}


host_keys_required() {
	hostkeys="$(get_config_option HostKey)"
	if [ "$hostkeys" ]; then
		echo "$hostkeys"
	else
		# No HostKey directives at all, so the server picks some
		# defaults depending on the setting of Protocol.
		protocol="$(get_config_option Protocol)"
		[ "$protocol" ] || protocol=1,2
		if echo "$protocol" | grep 1 >/dev/null; then
			echo /etc/ssh/ssh_host_key
		fi
		if echo "$protocol" | grep 2 >/dev/null; then
			echo /etc/ssh/ssh_host_rsa_key
			echo /etc/ssh/ssh_host_dsa_key
			echo /etc/ssh/ssh_host_ecdsa_key
		fi
	fi
}


create_key() {
	msg="$1"
	shift
	hostkeys="$1"
	shift
	file="$1"
	shift

	if echo "$hostkeys" | grep -x "$file" >/dev/null && \
	   [ ! -f "$file" ] ; then
		echo -n $msg
		ssh-keygen -q -f "$file" -N '' "$@"
		echo
		if which restorecon >/dev/null 2>&1; then
			restorecon "$file.pub"
		fi
	fi
}


create_keys() {
	hostkeys="$(host_keys_required)"

	create_key "Creating SSH1 key; this may take some time ..." \
		"$hostkeys" /etc/ssh/ssh_host_key -t rsa1

	create_key "Creating SSH2 RSA key; this may take some time ..." \
		"$hostkeys" /etc/ssh/ssh_host_rsa_key -t rsa
	create_key "Creating SSH2 DSA key; this may take some time ..." \
		"$hostkeys" /etc/ssh/ssh_host_dsa_key -t dsa
	create_key "Creating SSH2 ECDSA key; this may take some time ..." \
		"$hostkeys" /etc/ssh/ssh_host_ecdsa_key -t ecdsa
}


vulnerable_host_keys() {
	# If the admin has explicitly put the vulnerable keys back, we
	# assume they can look after themselves.
	db_fget ssh/vulnerable_host_keys seen
	if [ "$RET" = true ]; then
		return 0
	fi

	hostkeys="$(host_keys_required)"
	vulnerable=
	for hostkey in $hostkeys; do
		[ -f "$hostkey" ] || continue
		if ssh-vulnkey -q "$hostkey"; then
			vulnerable="${vulnerable:+$vulnerable }$hostkey"
		fi
	done
	if [ "$vulnerable" ]; then
		db_subst ssh/vulnerable_host_keys HOST_KEYS "$vulnerable"
		db_input critical ssh/vulnerable_host_keys || true
		db_go
		for hostkey in $vulnerable; do
			mv "$hostkey" "$hostkey.broken" || true
			mv "$hostkey.pub" "$hostkey.pub.broken" || true
		done
		create_keys
	fi
}


check_password_auth() {
	passwordauth="$(get_config_option PasswordAuthentication)"
	crauth="$(get_config_option ChallengeResponseAuthentication)"
	if [ "$passwordauth" = no ] && \
	   ([ -z "$crauth" ] || [ "$crauth" = yes ]); then
		db_get ssh/disable_cr_auth
		if [ "$RET" = true ]; then
			set_config_option ChallengeResponseAuthentication no
		fi
	fi
}


move_subsystem_sftp() {
	subsystem_sftp="$(get_config_option 'Subsystem sftp')"
	if [ "$subsystem_sftp" = /usr/lib/sftp-server ] || \
	   [ "$subsystem_sftp" = /usr/libexec/sftp-server ]; then
		set_config_option 'Subsystem sftp' /usr/lib/openssh/sftp-server
	fi
}


fix_loglevel_silent() {
	if [ "$(get_config_option LogLevel)" = SILENT ]; then
		set_config_option LogLevel QUIET
	fi
}


create_sshdconfig() {
	if [ -e /etc/ssh/sshd_config ] ; then
	    # Upgrade an existing sshd configuration.

	    if (dpkg --compare-versions "$oldversion" lt-nl 1:3.8p1-1 && \
		! grep -iq ^UsePAM /etc/ssh/sshd_config) || \
	       grep -Eiq '^(PAMAuthenticationViaKbdInt|RhostsAuthentication)' \
		 /etc/ssh/sshd_config ; then
		# Upgrade from pre-3.7: UsePAM needed to maintain standard
		# Debian configuration.
		# Note that --compare-versions is sadly not reliable enough
		# here due to the package split of ssh into openssh-client
		# and openssh-server. The extra grep for some deprecated
		# options should with any luck be a good enough heuristic.
		echo -n 'Upgrading sshd_config (old version in .dpkg-old) ...'
		cp -a /etc/ssh/sshd_config /etc/ssh/sshd_config.dpkg-old
		perl -pe 's/^(PAMAuthenticationViaKbdInt|RhostsAuthentication)\b/#$1/i' \
		    /etc/ssh/sshd_config > /etc/ssh/sshd_config.dpkg-new
		echo >> /etc/ssh/sshd_config.dpkg-new
		echo 'UsePAM yes' >> /etc/ssh/sshd_config.dpkg-new
		chown --reference /etc/ssh/sshd_config \
				  /etc/ssh/sshd_config.dpkg-new
		chmod --reference /etc/ssh/sshd_config \
				  /etc/ssh/sshd_config.dpkg-new
		mv /etc/ssh/sshd_config.dpkg-new /etc/ssh/sshd_config
		echo
	    fi

	    # An empty version means we're upgrading from before the
	    # package split, so check.
	    if dpkg --compare-versions "$oldversion" lt 1:3.8.1p1-11; then
		check_password_auth
	    fi

	    # libexecdir changed, so fix up 'Subsystem sftp'.
	    if dpkg --compare-versions "$oldversion" lt 1:4.1p1-1; then
		move_subsystem_sftp
	    fi

	    # Remove obsolete GSSAPI options.
	    if dpkg --compare-versions "$oldversion" lt 1:4.3p2-8; then
		remove_obsolete_gssapi
	    fi

	    # This option was renamed in 3.8p1, but we never took care
	    # of adjusting the configuration file until now.
	    if dpkg --compare-versions "$oldversion" lt 1:4.7p1-8; then
		rename_config_option KeepAlive TCPKeepAlive
	    fi

	    # 'LogLevel SILENT' is now equivalent to QUIET.
	    if dpkg --compare-versions "$oldversion" lt 1:5.4p1-1; then
		fix_loglevel_silent
	    fi

	    return 0
	fi

	cat <<EOF > /etc/ssh/sshd_config
# Package generated configuration file
# See the sshd_config(5) manpage for details

# What ports, IPs and protocols we listen for
Port 22
# Use these options to restrict which interfaces/protocols sshd will bind to
#ListenAddress ::
#ListenAddress 0.0.0.0
Protocol 2
# HostKeys for protocol version 2
HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_dsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key
#Privilege Separation is turned on for security
UsePrivilegeSeparation yes

# Lifetime and size of ephemeral version 1 server key
KeyRegenerationInterval 3600
ServerKeyBits 768

# Logging
SyslogFacility AUTH
LogLevel INFO

# Authentication:
LoginGraceTime 120
PermitRootLogin yes
StrictModes yes

RSAAuthentication yes
PubkeyAuthentication yes
#AuthorizedKeysFile	%h/.ssh/authorized_keys

# Don't read the user's ~/.rhosts and ~/.shosts files
IgnoreRhosts yes
# For this to work you will also need host keys in /etc/ssh_known_hosts
RhostsRSAAuthentication no
# similar for protocol version 2
HostbasedAuthentication no
# Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication
#IgnoreUserKnownHosts yes

# To enable empty passwords, change to yes (NOT RECOMMENDED)
PermitEmptyPasswords no

# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication no

# Change to no to disable tunnelled clear text passwords
#PasswordAuthentication yes

# Kerberos options
#KerberosAuthentication no
#KerberosGetAFSToken no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes

# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes

X11Forwarding yes
X11DisplayOffset 10
PrintMotd no
PrintLastLog yes
TCPKeepAlive yes
#UseLogin no

#MaxStartups 10:30:60
#Banner /etc/issue.net

# Allow client to pass locale environment variables
AcceptEnv LANG LC_*

Subsystem sftp /usr/lib/openssh/sftp-server

# Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication.  Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
UsePAM yes
EOF
}

fix_statoverride() {
# Remove an erronous override for sshd (we should have overridden ssh)
	if [ -x /usr/sbin/dpkg-statoverride ]; then
		if dpkg-statoverride --list /usr/sbin/sshd >/dev/null ; then
			dpkg-statoverride --remove /usr/sbin/sshd
		fi
	fi
}

fix_sshd_shell() {
	if getent passwd sshd | grep -q ':/bin/false$'; then
		usermod -s /usr/sbin/nologin sshd || true
	fi
}

setup_sshd_user() {
	if ! getent passwd sshd >/dev/null; then
		adduser --quiet --system --no-create-home --home /var/run/sshd --shell /usr/sbin/nologin sshd
	fi
}

fix_conffile_permissions() {
	# Clean up after executable /etc/default/ssh in 1:3.5p1-5. dpkg
	# doesn't do this for us; see bug #192981.
	chmod 644 /etc/default/ssh
}

remove_old_init_links() {
	# Yes, this only works with the SysV init script layout. I know.
	# The important thing is that it doesn't actually *break* with
	# file-rc ...
	if [ -e /etc/rc2.d/S20ssh ]; then
		update-rc.d -f ssh remove >/dev/null 2>&1
	fi
	rm -f /etc/rc0.d/K??ssh /etc/rc1.d/K??ssh /etc/rc6.d/K??ssh
}

setup_init() {
	if [ -x /etc/init.d/ssh ]; then
		update-rc.d ssh start 16 2 3 4 5 . >/dev/null
		if [ -x /usr/sbin/invoke-rc.d ]; then
			invoke-rc.d ssh restart
		else
			/etc/init.d/ssh restart
		fi
	fi
}

commit_transfer_conffile () {
	CONFFILE="$1"
	if [ -e "$CONFFILE.moved-by-preinst" ]; then
		rm -f "$CONFFILE.moved-by-preinst"
	fi
}

commit_mv_conffile () {
	OLDCONFFILE="$1"
	NEWCONFFILE="$2"

	if [ -e "$OLDCONFFILE.moving" ]; then
		echo "Preserving user changes to $NEWCONFFILE ..."
		mv -f "$NEWCONFFILE" "$NEWCONFFILE.dpkg-new"
		mv -f "$OLDCONFFILE.moving" "$NEWCONFFILE"
	elif [ -e "$OLDCONFFILE.dpkg-old" ]; then
		rm -f "$OLDCONFFILE.dpkg-old"
	fi
}


fix_doc_symlink
create_sshdconfig
create_keys
vulnerable_host_keys
fix_statoverride
if dpkg --compare-versions "$2" lt 1:4.3p2-3; then
    fix_sshd_shell
fi
setup_sshd_user
if dpkg --compare-versions "$2" lt 1:3.6.1p2-2; then
    fix_conffile_permissions
fi
if dpkg --compare-versions "$2" lt 1:5.2p1-1; then
    remove_old_init_links
fi
setup_init
commit_transfer_conffile /etc/default/ssh
commit_transfer_conffile /etc/init.d/ssh
commit_transfer_conffile /etc/pam.d/ssh
commit_mv_conffile /etc/pam.d/ssh /etc/pam.d/sshd
# Renamed to /etc/ssh/moduli in 2.9.9 (!)
if dpkg --compare-versions "$2" lt 1:4.7p1-1; then
    rm -f /etc/ssh/primes
fi
if dpkg --compare-versions "$2" lt 1:5.5p1-6; then
    rm -f /var/run/sshd/.placeholder
fi


db_stop

exit 0