summaryrefslogtreecommitdiff
path: root/gnu/system/nss.scm
blob: f4d2855289980c93a9167d6e5a6af44a713b0b35 (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
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2015 Ludovic Courtès <ludo@gnu.org>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.

(define-module (gnu system nss)
  #:use-module (rnrs enums)
  #:use-module (guix records)
  #:use-module (srfi srfi-9)
  #:use-module (ice-9 match)
  #:export (name-service-switch?
            name-service-switch
            name-service?
            name-service

            lookup-specification

            %default-nss
            %mdns-host-lookup-nss

            %files
            %compat
            %dns

            name-service-switch->string))

;;; Commentary:
;;;
;;; Bindings for libc's name service switch (NSS) configuration.
;;;
;;; Code:

(define-record-type* <name-service> name-service
  make-name-service
  name-service?
  (name     name-service-name)
  (reaction name-service-reaction
            (default (lookup-specification))))

;; Lookup specification (info "(libc) Actions in the NSS Configuration").

(define-enumeration lookup-action
  (return continue)
  make-lookup-action)

(define-enumeration lookup-status
  (success
   not-found
   unavailable
   try-again)
  make-lookup-status)

(define-record-type <lookup-status-negation>
  (lookup-status-negation status)
  lookup-status-negation?
  (status lookup-status-negation-status))

(define-record-type <lookup-reaction>
  (make-lookup-reaction status action)
  lookup-reaction?
  (status  lookup-reaction-status)
  (action  lookup-reaction-action))

(define-syntax lookup-reaction
  (syntax-rules (not =>)
    ((_ ((not status) => action))
     (make-lookup-reaction (lookup-status-negation (lookup-status status))
                           (lookup-action action)))
    ((_ (status => action))
     (make-lookup-reaction (lookup-status status)
                           (lookup-action action)))))

(define-syntax-rule (lookup-specification reaction ...)
  "Return an NSS lookup specification."
  (list (lookup-reaction reaction) ...))


;;;
;;; Common name services and default NSS configuration.
;;;

(define %compat
  (name-service
    (name "compat")
    (reaction (lookup-specification (not-found => return)))))

(define %files
  (name-service (name "files")))

(define %dns
  ;; DNS is supposed to be authoritative, so unless it's unavailable, return
  ;; what it finds.
  (name-service
    (name "dns")
    (reaction (lookup-specification ((not unavailable) => return)))))

;; The NSS.  We list all the databases here because that allows us to
;; statically ensure that the user's configuration refers to existing
;; databases.  See libc/nss/databases.def for the list of databases.  Default
;; values obtained by looking for "DEFAULT_CONFIG" in libc/nss/*.c.
;;
;; Although libc places 'dns' before 'files' in the default configurations of
;; the 'hosts' and 'networks' databases, we choose to put 'files' before 'dns'
;; by default, so that users can override host/address mappings in /etc/hosts
;; and bypass DNS to improve their privacy and escape NSA's MORECOWBELL.
(define-record-type* <name-service-switch> name-service-switch
  make-name-service-switch
  name-service-switch?
  (aliases    name-service-switch-aliases
              (default '()))
  (ethers     name-service-switch-ethers
              (default '()))
  (group      name-service-switch-group
              (default (list %compat %files)))
  (gshadow    name-service-switch-gshadow
              (default '()))
  (hosts      name-service-switch-hosts
              (default (list %files %dns)))
  (initgroups name-service-switch-initgroups
              (default '()))
  (netgroup   name-service-switch-netgroup
              (default '()))
  (networks   name-service-switch-networks
              (default (list %files %dns)))
  (password   name-service-switch-password
              (default (list %compat %files)))
  (public-key name-service-switch-public-key
              (default '()))
  (rpc        name-service-switch-rpc
              (default '()))
  (services   name-service-switch-services
              (default '()))
  (shadow     name-service-switch-shadow
              (default (list %compat %files))))

(define %default-nss
  ;; Default NSS configuration.
  (name-service-switch))

(define %mdns-host-lookup-nss
  (name-service-switch
    (hosts (list %files                           ;first, check /etc/hosts

                 ;; If the above did not succeed, try with 'mdns_minimal'.
                 (name-service
                   (name "mdns_minimal")

                   ;; 'mdns_minimal' is authoritative for '.local'.  When it
                   ;; returns "not found", no need to try the next methods.
                   (reaction (lookup-specification
                              (not-found => return))))

                 ;; Then fall back to DNS.
                 (name-service
                   (name "dns"))

                 ;; Finally, try with the "full" 'mdns'.
                 (name-service
                   (name "mdns"))))))


;;;
;;; Serialization.
;;;

(define (lookup-status->string status)
  (match status
    ('success     "SUCCESS")
    ('not-found   "NOTFOUND")
    ('unavailable "UNAVAIL")
    ('try-again   "TRYAGAIN")
    (($ <lookup-status-negation> status)
     (string-append "!" (lookup-status->string status)))))

(define lookup-reaction->string
  (match-lambda
   (($ <lookup-reaction> status action)
    (string-append (lookup-status->string status) "="
                   (symbol->string action)))))

(define name-service->string
  (match-lambda
   (($ <name-service> name ())
    name)
   (($ <name-service> name reactions)
    (string-append name " ["
                   (string-join (map lookup-reaction->string reactions))
                   "]"))))

(define (name-service-switch->string nss)
  "Return the 'nsswitch.conf' contents for NSS as a string.  See \"NSS
Configuration File\" in the libc manual."
  (let-syntax ((->string
                (syntax-rules ()
                  ((_ name field)
                   (match (field nss)
                     (()                          ;keep the default config
                      "")
                     ((services (... ...))
                      (string-append name ":\t"
                                     (string-join
                                      (map name-service->string services))
                                     "\n")))))))
    (string-append (->string "aliases"    name-service-switch-aliases)
                   (->string "ethers"     name-service-switch-ethers)
                   (->string "group"      name-service-switch-group)
                   (->string "gshadow"    name-service-switch-gshadow)
                   (->string "hosts"      name-service-switch-hosts)
                   (->string "initgroups" name-service-switch-initgroups)
                   (->string "netgroup"   name-service-switch-netgroup)
                   (->string "networks"   name-service-switch-networks)
                   (->string "passwd"     name-service-switch-password)
                   (->string "publickey"  name-service-switch-public-key)
                   (->string "rpc"        name-service-switch-rpc)
                   (->string "services"   name-service-switch-services)
                   (->string "shadow"     name-service-switch-shadow))))

;;; Local Variables:
;;; eval: (put 'name-service 'scheme-indent-function 0)
;;; eval: (put 'name-service-switch 'scheme-indent-function 0)
;;; End:

;;; nss.scm ends here