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1;;; GNU Guix --- Functional package management for GNU
2;;; Copyright © 2016 John Darrington <[email protected]>
3;;;
4;;; This file is part of GNU Guix.
5;;;
6;;; GNU Guix is free software; you can redistribute it and/or modify it
7;;; under the terms of the GNU General Public License as published by
8;;; the Free Software Foundation; either version 3 of the License, or (at
9;;; your option) any later version.
10;;;
11;;; GNU Guix is distributed in the hope that it will be useful, but
12;;; WITHOUT ANY WARRANTY; without even the implied warranty of
13;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14;;; GNU General Public License for more details.
15;;;
16;;; You should have received a copy of the GNU General Public License
17;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
18
19(define-module (gnu services kerberos)
20 #:use-module (gnu packages admin)
21 #:use-module (gnu services)
22 #:use-module (gnu services configuration)
23 #:use-module (gnu system pam)
24 #:use-module (guix gexp)
25 #:use-module (guix records)
26 #:use-module (srfi srfi-1)
27 #:use-module (srfi srfi-34)
28 #:use-module (srfi srfi-35)
29 #:use-module (ice-9 match)
30 #:export (pam-krb5-configuration
31 pam-krb5-configuration?
32 pam-krb5-service-type
33
34 krb5-realm
35 krb5-realm?
36
37 krb5-configuration
38 krb5-configuration?
39 krb5-service-type))
40
41
42
43;; TODO Use %unset-value and the define-maybe infrastructure.
44(define unset-field (list 'unset-field))
45
46(define (predicate/unset pred)
47 (lambda (x) (or (eq? x unset-field) (pred x))))
48
49(define string/unset? (predicate/unset string?))
50(define boolean/unset? (predicate/unset boolean?))
51(define integer/unset? (predicate/unset integer?))
52
53(define (uglify-field-name field-name)
54 "Return FIELD-NAME with all instances of '-' replaced by '_' and any
55trailing '?' removed."
56 (let ((str (symbol->string field-name)))
57 (string-join (string-split (if (string-suffix? "?" str)
58 (substring str 0 (1- (string-length str)))
59 str)
60 #\-)
61 "_")))
62
63(define (serialize-field* field-name val)
64 (format #t "~a = ~a\n" (uglify-field-name field-name) val))
65
66(define (serialize-string/unset field-name val)
67 (unless (eq? val unset-field)
68 (serialize-field* field-name val)))
69
70(define (serialize-integer/unset field-name val)
71 (unless (eq? val unset-field)
72 (serialize-field* field-name val)))
73
74(define (serialize-boolean/unset field-name val)
75 (unless (eq? val unset-field)
76 (serialize-field* field-name
77 (if val "true" "false"))))
78
79
80;; An end-point is an address such as "192.168.0.1"
81;; or an address port pair ("foobar.example.com" . 109)
82(define (end-point? val)
83 (match val
84 ((? string?) #t)
85 (((? string?) . (? integer?)) #t)
86 (_ #f)))
87
88(define (serialize-end-point field-name val)
89 (serialize-field* field-name
90 (match val
91 ((host . port)
92 ;; The [] are needed in the case of IPv6 addresses
93 (format #f "[~a]:~a" host port))
94 (host
95 (format #f "~a" host)))))
96
97(define (serialize-space-separated-string-list/unset field-name val)
98 (unless (eq? val unset-field)
99 (serialize-field* field-name (string-join val " "))))
100
101(define (space-separated-string-list? val)
102 (and (list? val)
103 (and-map (lambda (x)
104 (and (string? x) (not (string-index x #\space))))
105 val)))
106
107(define space-separated-string-list/unset?
108 (predicate/unset space-separated-string-list?))
109
110(define comma-separated-integer-list/unset?
111 (predicate/unset (lambda (val)
112 (and (list? val)
113 (and-map (lambda (x) (integer? x))
114 val)))))
115
116(define (serialize-comma-separated-integer-list/unset field-name val)
117 (unless (eq? val unset-field)
118 (serialize-field* field-name
119 (string-drop ; Drop the leading comma
120 (fold
121 (lambda (i prev)
122 (string-append prev "," (number->string i)))
123 "" val) 1))))
124
125(define file-name? (predicate/unset
126 (lambda (val)
127 (string-prefix? "/" val))))
128
129(define (serialize-field field-name val)
130 (format #t "~a ~a\n" (uglify-field-name field-name) val))
131
132(define (serialize-string field-name val)
133 (serialize-field field-name val))
134
135(define (serialize-file-name field-name val)
136 (unless (eq? val unset-field)
137 (serialize-string field-name val)))
138
139(define (serialize-space-separated-string-list field-name val)
140 (serialize-field field-name (string-join val " ")))
141
142(define (non-negative-integer? val)
143 (and (exact-integer? val) (not (negative? val))))
144
145(define (serialize-non-negative-integer/unset field-name val)
146 (unless (eq? val unset-field)
147 (serialize-field* field-name val)))
148
149(define (free-form-fields? val)
150 (match val
151 (() #t)
152 ((((? symbol?) . (? string)) . val) (free-form-fields? val))
153 (_ #f)))
154
155(define (serialize-free-form-fields field-name val)
156 (for-each (match-lambda ((k . v) (serialize-field* k v))) val))
157
158(define non-negative-integer/unset? (predicate/unset non-negative-integer?))
159
160(define (realm-list? val)
161 (and (list? val)
162 (and-map (lambda (x) (krb5-realm? x)) val)))
163
164(define (serialize-realm-list field-name val)
165 (format #t "\n[~a]\n" field-name)
166 (for-each (lambda (realm)
167 (format #t "\n~a = {\n" (krb5-realm-name realm))
168 (for-each (lambda (field)
169 (unless (eq? 'name (configuration-field-name field))
170 ((configuration-field-serializer field)
171 (configuration-field-name field)
172 ((configuration-field-getter field)
173 realm)))) krb5-realm-fields)
174
175 (format #t "}\n")) val))
176
177
178
179;; For a more detailed explanation of these fields see man 5 krb5.conf
180(define-configuration krb5-realm
181 (name
182 (string/unset unset-field)
183 "The name of the realm.")
184
185 (kdc
186 (end-point unset-field)
187 "The host and port on which the realm's Key Distribution Server listens.")
188
189 (admin-server
190 (string/unset unset-field)
191 "The Host running the administration server for the realm.")
192
193 (master-kdc
194 (string/unset unset-field)
195 "If an attempt to get credentials fails because of an invalid password,
196the client software will attempt to contact the master KDC.")
197
198 (kpasswd-server
199 (string/unset unset-field)
200 "The server where password changes are performed.")
201
202 (auth-to-local
203 (free-form-fields '())
204 "Rules to map between principals and local users.")
205
206 (auth-to-local-names
207 (free-form-fields '())
208 "Explicit mappings between principal names and local user names.")
209
210 (http-anchors
211 (free-form-fields '())
212 "Useful only when http proxy is used to access KDC or KPASSWD.")
213
214 ;; The following are useful only for working with V4 services
215 (default-domain
216 (string/unset unset-field)
217 "The domain used to expand host names when translating Kerberos 4 service
218principals to Kerberos 5 principals")
219
220 (v4-instance-convert
221 (free-form-fields '())
222 "Exceptions to the default-domain mapping rule.")
223
224 (v4-realm
225 (string/unset unset-field)
226 "Used when the V4 realm name and the V5 realm name are not the same, but
227still share the same principal names and passwords"))
228
229
230
231;; For a more detailed explanation of these fields see man 5 krb5.conf
232(define-configuration krb5-configuration
233 (allow-weak-crypto?
234 (boolean/unset unset-field)
235 "If true, permits access to services which only offer weak encryption.")
236
237 (ap-req-checksum-type
238 (non-negative-integer/unset unset-field)
239 "The type of the AP-REQ checksum.")
240
241 (canonicalize?
242 (boolean/unset unset-field)
243 "Should principals in initial ticket requests be canonicalized?")
244
245 (ccache-type
246 (non-negative-integer/unset unset-field)
247 "The format of the credential cache type.")
248
249 (clockskew
250 (non-negative-integer/unset unset-field)
251 "Maximum allowable clock skew in seconds (default 300).")
252
253 (default-ccache-name
254 (file-name unset-field)
255 "The name of the default credential cache.")
256
257 (default-client-keytab-name
258 (file-name unset-field)
259 "The name of the default keytab for client credentials.")
260
261 (default-keytab-name
262 (file-name unset-field)
263 "The name of the default keytab file.")
264
265 (default-realm
266 (string/unset unset-field)
267 "The realm to be accessed if not explicitly specified by clients.")
268
269 (default-tgs-enctypes
270 (free-form-fields '())
271 "Session key encryption types when making TGS-REQ requests.")
272
273 (default-tkt-enctypes
274 (free-form-fields '())
275 "Session key encryption types when making AS-REQ requests.")
276
277 (dns-canonicalize-hostname?
278 (boolean/unset unset-field)
279 "Whether name lookups will be used to canonicalize host names for use in
280service principal names.")
281
282 (dns-lookup-kdc?
283 (boolean/unset unset-field)
284 "Should DNS SRV records should be used to locate the KDCs and other servers
285not appearing in the realm specification")
286
287 (err-fmt
288 (string/unset unset-field)
289 "Custom error message formatting. If not #f error messages will be formatted
290by substituting a normal error message for %M and an error code for %C in the
291value.")
292
293 (forwardable?
294 (boolean/unset unset-field)
295 "Should initial tickets be forwardable by default?")
296
297 (ignore-acceptor-hostname?
298 (boolean/unset unset-field)
299 "When accepting GSSAPI or krb5 security contexts for host-based service
300principals, ignore any hostname passed by the calling application, and allow
301clients to authenticate to any service principal in the keytab matching the
302service name and realm name.")
303
304 (k5login-authoritative?
305 (boolean/unset unset-field)
306 "If this flag is true, principals must be listed in a local user's k5login
307file to be granted login access, if a ~/.k5login file exists.")
308
309 (k5login-directory
310 (string/unset unset-field)
311 "If not #f, the library will look for a local user's @file{k5login} file
312within the named directory (instead of the user's home directory), with a
313file name corresponding to the local user name.")
314
315 (kcm-mach-service
316 (string/unset unset-field)
317 "The name of the bootstrap service used to contact the KCM daemon for the
318KCM credential cache type.")
319
320 (kcm-socket
321 (file-name unset-field)
322 "Path to the Unix domain socket used to access the KCM daemon for the KCM
323credential cache type.")
324
325 (kdc-default-options
326 (non-negative-integer/unset unset-field)
327 "Default KDC options (logored for multiple values) when requesting initial
328tickets.")
329
330 (kdc-timesync
331 (non-negative-integer/unset unset-field)
332 "Attempt to compensate for clock skew between the KDC and client.")
333
334 (kdc-req-checksum-type
335 (non-negative-integer/unset unset-field)
336 "The type of checksum to use for the KDC requests. Relevant only for DES
337keys")
338
339 (noaddresses?
340 (boolean/unset unset-field)
341 "If true, initial ticket requests will not be made with address restrictions.
342This enables their use across NATs.")
343
344 (permitted-enctypes
345 (space-separated-string-list/unset unset-field)
346 "All encryption types that are permitted for use in session key encryption.")
347
348 (plugin-base-dir
349 (file-name unset-field)
350 "The directory where krb5 plugins are located.")
351
352 (preferred-preauth-types
353 (comma-separated-integer-list/unset unset-field)
354 "The preferred pre-authentication types which the client will attempt before
355others.")
356
357 (proxiable?
358 (boolean/unset unset-field)
359 "Should initial tickets be proxiable by default?")
360
361 (rdns?
362 (boolean/unset unset-field)
363 "Should reverse DNS lookup be used in addition to forward name lookup to
364canonicalize host names for use in service principal names.")
365
366 (realm-try-domains
367 (integer/unset unset-field)
368 "Should a host's domain components should be used to determine the Kerberos
369realm of the host.")
370
371 (renew-lifetime
372 (non-negative-integer/unset unset-field)
373 "The default renewable lifetime for initial ticket requests.")
374
375 (safe-checksum-type
376 (non-negative-integer/unset unset-field)
377 "The type of checksum to use for the KRB-SAFE requests.")
378
379 (ticket-lifetime
380 (non-negative-integer/unset unset-field)
381 "The default lifetime for initial ticket requests.")
382
383 (udp-preference-limit
384 (non-negative-integer/unset unset-field)
385 "When sending messages to the KDC, the library will try using TCP
386before UDP if the size of the message greater than this limit.")
387
388 (verify-ap-rereq-nofail?
389 (boolean/unset unset-field)
390 "If true, then attempts to verify initial credentials will fail if the client
391machine does not have a keytab.")
392
393 (realms
394 (realm-list '())
395 "The list of realms which clients may access."))
396
397
398(define (krb5-configuration-file config)
399 "Create a Kerberos 5 configuration file based on CONFIG"
400 (mixed-text-file "krb5.conf"
401 "[libdefaults]\n\n"
402 (with-output-to-string
403 (lambda ()
404 (serialize-configuration config
405 krb5-configuration-fields)))))
406
407(define (krb5-etc-service config)
408 (list `("krb5.conf" ,(krb5-configuration-file config))))
409
410
411(define krb5-service-type
412 (service-type (name 'krb5)
413 (extensions
414 (list (service-extension etc-service-type
415 krb5-etc-service)))
416 (description "Programs using a Kerberos client library
417normally expect a configuration file in @file{/etc/krb5.conf}. This service
418generates such a file. It does not cause any daemon to be started.")))
419
420
421
422(define-record-type* <pam-krb5-configuration>
423 pam-krb5-configuration make-pam-krb5-configuration
424 pam-krb5-configuration?
425 (pam-krb5 pam-krb5-configuration-pam-krb5
426 (default pam-krb5))
427 (minimum-uid pam-krb5-configuration-minimum-uid
428 (default 1000)))
429
430(define (pam-krb5-pam-service config)
431 "Return a PAM service for Kerberos authentication."
432 (pam-extension
433 (transformer
434 (lambda (pam)
435 (define pam-krb5-module
436 (file-append (pam-krb5-configuration-pam-krb5 config)
437 "/lib/security/pam_krb5.so"))
438
439 (let ((pam-krb5-sufficient
440 (pam-entry
441 (control "sufficient")
442 (module pam-krb5-module)
443 (arguments
444 (list
445 (format #f "minimum_uid=~a"
446 (pam-krb5-configuration-minimum-uid config)))))))
447 (pam-service
448 (inherit pam)
449 (auth (cons* pam-krb5-sufficient
450 (pam-service-auth pam)))
451 (session (cons* pam-krb5-sufficient
452 (pam-service-session pam)))
453 (account (cons* pam-krb5-sufficient
454 (pam-service-account pam)))))))))
455
456(define (pam-krb5-pam-services config)
457 (list (pam-krb5-pam-service config)))
458
459(define pam-krb5-service-type
460 (service-type (name 'pam-krb5)
461 (extensions
462 (list
463 (service-extension pam-root-service-type
464 pam-krb5-pam-services)))
465 (description "The @code{pam-krb5} service allows for login
466authentication and password management via Kerberos. You will need this
467service if you want PAM-enabled applications to authenticate users using
468Kerberos.")))