| 1 | ;;; GNU Guix --- Functional package management for GNU |
| 2 | ;;; Copyright © 2019 Ludovic Courtès <ludo@gnu.org> |
| 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 build accounts) |
| 20 | #:use-module (guix records) |
| 21 | #:use-module (guix combinators) |
| 22 | #:use-module (gnu system accounts) |
| 23 | #:use-module (srfi srfi-1) |
| 24 | #:use-module (srfi srfi-11) |
| 25 | #:use-module (srfi srfi-19) |
| 26 | #:use-module (srfi srfi-26) |
| 27 | #:use-module (ice-9 match) |
| 28 | #:use-module (ice-9 vlist) |
| 29 | #:use-module (ice-9 rdelim) |
| 30 | #:export (password-entry |
| 31 | password-entry? |
| 32 | password-entry-name |
| 33 | password-entry-uid |
| 34 | password-entry-gid |
| 35 | password-entry-real-name |
| 36 | password-entry-directory |
| 37 | password-entry-shell |
| 38 | |
| 39 | shadow-entry |
| 40 | shadow-entry? |
| 41 | shadow-entry-name |
| 42 | shadow-entry-minimum-change-period |
| 43 | shadow-entry-maximum-change-period |
| 44 | shadow-entry-change-warning-time |
| 45 | shadow-entry-maximum-inactivity |
| 46 | shadow-entry-expiration |
| 47 | |
| 48 | group-entry |
| 49 | group-entry? |
| 50 | group-entry-name |
| 51 | group-entry-gid |
| 52 | group-entry-members |
| 53 | |
| 54 | write-group |
| 55 | write-passwd |
| 56 | write-shadow |
| 57 | read-group |
| 58 | read-passwd |
| 59 | read-shadow |
| 60 | |
| 61 | %id-min |
| 62 | %id-max |
| 63 | %system-id-min |
| 64 | %system-id-max |
| 65 | |
| 66 | user+group-databases)) |
| 67 | |
| 68 | ;;; Commentary: |
| 69 | ;;; |
| 70 | ;;; This modules provides functionality equivalent to the C library's |
| 71 | ;;; <shadow.h>, <pwd.h>, and <grp.h> routines, as well as a subset of the |
| 72 | ;;; functionality of the Shadow command-line tools. It can parse and write |
| 73 | ;;; /etc/passwd, /etc/shadow, and /etc/group. It can also take care of UID |
| 74 | ;;; and GID allocation in a way similar to what 'useradd' does. |
| 75 | ;;; |
| 76 | ;;; The benefit is twofold: less code is involved, and the ID allocation |
| 77 | ;;; strategy and state preservation is made explicit. |
| 78 | ;;; |
| 79 | ;;; Code: |
| 80 | |
| 81 | \f |
| 82 | ;;; |
| 83 | ;;; Machinery to define user and group databases. |
| 84 | ;;; |
| 85 | |
| 86 | (define-syntax serialize-field |
| 87 | (syntax-rules (serialization) |
| 88 | ((_ entry (field get (serialization ->string string->) _ ...)) |
| 89 | (->string (get entry))) |
| 90 | ((_ entry (field get _ ...)) |
| 91 | (get entry)))) |
| 92 | |
| 93 | (define-syntax deserialize-field |
| 94 | (syntax-rules (serialization) |
| 95 | ((_ str (field get (serialization ->string string->) _ ...)) |
| 96 | (string-> str)) |
| 97 | ((_ str (field get _ ...)) |
| 98 | str))) |
| 99 | |
| 100 | (define-syntax let/fields |
| 101 | (syntax-rules () |
| 102 | ((_ (((name get attributes ...) rest ...) lst) body ...) |
| 103 | (let ((l lst)) |
| 104 | (let ((name (deserialize-field (car l) |
| 105 | (name get attributes ...)))) |
| 106 | (let/fields ((rest ...) (cdr l)) body ...)))) |
| 107 | ((_ (() lst) body ...) |
| 108 | (begin body ...)))) |
| 109 | |
| 110 | (define-syntax define-database-entry |
| 111 | (syntax-rules (serialization) |
| 112 | "Define a record data type, as per 'define-record-type*', with additional |
| 113 | information on how to serialize and deserialize the whole database as well as |
| 114 | each field." |
| 115 | ((_ <record> record make-record record? |
| 116 | (serialization separator entry->string string->entry) |
| 117 | fields ...) |
| 118 | (let-syntax ((field-name |
| 119 | (syntax-rules () |
| 120 | ((_ (name _ (... ...))) name)))) |
| 121 | (define-record-type* <record> record make-record |
| 122 | record? |
| 123 | fields ...) |
| 124 | |
| 125 | (define (entry->string entry) |
| 126 | (string-join (list (serialize-field entry fields) ...) |
| 127 | (string separator))) |
| 128 | |
| 129 | (define (string->entry str) |
| 130 | (let/fields ((fields ...) (string-split str #\:)) |
| 131 | (make-record (field-name fields) ...))))))) |
| 132 | |
| 133 | |
| 134 | (define number->string* |
| 135 | (match-lambda |
| 136 | ((? number? number) (number->string number)) |
| 137 | (_ ""))) |
| 138 | |
| 139 | (define (false-if-string=? false-string) |
| 140 | (lambda (str) |
| 141 | (if (string=? str false-string) |
| 142 | #f |
| 143 | str))) |
| 144 | |
| 145 | (define (string-if-false str) |
| 146 | (lambda (obj) |
| 147 | (if (not obj) str obj))) |
| 148 | |
| 149 | (define (comma-separated->list str) |
| 150 | (string-tokenize str (char-set-complement (char-set #\,)))) |
| 151 | |
| 152 | (define (list->comma-separated lst) |
| 153 | (string-join lst ",")) |
| 154 | |
| 155 | \f |
| 156 | ;;; |
| 157 | ;;; Database definitions. |
| 158 | ;;; |
| 159 | |
| 160 | (define-database-entry <password-entry> ;<pwd.h> |
| 161 | password-entry make-password-entry |
| 162 | password-entry? |
| 163 | (serialization #\: password-entry->string string->password-entry) |
| 164 | |
| 165 | (name password-entry-name) |
| 166 | (password password-entry-password |
| 167 | (serialization (const "x") (const #f)) |
| 168 | (default "x")) |
| 169 | (uid password-entry-uid |
| 170 | (serialization number->string string->number)) |
| 171 | (gid password-entry-gid |
| 172 | (serialization number->string string->number)) |
| 173 | (real-name password-entry-real-name |
| 174 | (default "")) |
| 175 | (directory password-entry-directory) |
| 176 | (shell password-entry-shell |
| 177 | (default "/bin/sh"))) |
| 178 | |
| 179 | (define-database-entry <shadow-entry> ;<shadow.h> |
| 180 | shadow-entry make-shadow-entry |
| 181 | shadow-entry? |
| 182 | (serialization #\: shadow-entry->string string->shadow-entry) |
| 183 | |
| 184 | (name shadow-entry-name) ;string |
| 185 | (password shadow-entry-password ;string | #f |
| 186 | (serialization (string-if-false "!") |
| 187 | (false-if-string=? "!")) |
| 188 | (default #f)) |
| 189 | (last-change shadow-entry-last-change ;days since 1970-01-01 |
| 190 | (serialization number->string* string->number) |
| 191 | (default 0)) |
| 192 | (minimum-change-period shadow-entry-minimum-change-period |
| 193 | (serialization number->string* string->number) |
| 194 | (default #f)) ;days | #f |
| 195 | (maximum-change-period shadow-entry-maximum-change-period |
| 196 | (serialization number->string* string->number) |
| 197 | (default #f)) ;days | #f |
| 198 | (change-warning-time shadow-entry-change-warning-time |
| 199 | (serialization number->string* string->number) |
| 200 | (default #f)) ;days | #f |
| 201 | (maximum-inactivity shadow-entry-maximum-inactivity |
| 202 | (serialization number->string* string->number) |
| 203 | (default #f)) ;days | #f |
| 204 | (expiration shadow-entry-expiration |
| 205 | (serialization number->string* string->number) |
| 206 | (default #f)) ;days since 1970-01-01 | #f |
| 207 | (flags shadow-entry-flags ;"reserved" |
| 208 | (serialization number->string* string->number) |
| 209 | (default #f))) |
| 210 | |
| 211 | (define-database-entry <group-entry> ;<grp.h> |
| 212 | group-entry make-group-entry |
| 213 | group-entry? |
| 214 | (serialization #\: group-entry->string string->group-entry) |
| 215 | |
| 216 | (name group-entry-name) |
| 217 | (password group-entry-password |
| 218 | (serialization (string-if-false "x") |
| 219 | (false-if-string=? "x")) |
| 220 | (default #f)) |
| 221 | (gid group-entry-gid |
| 222 | (serialization number->string string->number)) |
| 223 | (members group-entry-members |
| 224 | (serialization list->comma-separated comma-separated->list) |
| 225 | (default '()))) |
| 226 | |
| 227 | (define (database-writer file mode entry->string) |
| 228 | (lambda* (entries #:optional (file-or-port file)) |
| 229 | "Write ENTRIES to FILE-OR-PORT. When FILE-OR-PORT is a file name, write |
| 230 | to it atomically and set the appropriate permissions." |
| 231 | (define (write-entries port) |
| 232 | (for-each (lambda (entry) |
| 233 | (display (entry->string entry) port) |
| 234 | (newline port)) |
| 235 | entries)) |
| 236 | |
| 237 | (if (port? file-or-port) |
| 238 | (write-entries file-or-port) |
| 239 | (let* ((template (string-append file-or-port ".XXXXXX")) |
| 240 | (port (mkstemp! template))) |
| 241 | (dynamic-wind |
| 242 | (const #t) |
| 243 | (lambda () |
| 244 | (chmod port mode) |
| 245 | (write-entries port) |
| 246 | (rename-file template file-or-port)) |
| 247 | (lambda () |
| 248 | (close-port port) |
| 249 | (when (file-exists? template) |
| 250 | (delete-file template)))))))) |
| 251 | |
| 252 | (define write-passwd |
| 253 | (database-writer "/etc/passwd" #o644 password-entry->string)) |
| 254 | (define write-shadow |
| 255 | (database-writer "/etc/shadow" #o600 shadow-entry->string)) |
| 256 | (define write-group |
| 257 | (database-writer "/etc/group" #o644 group-entry->string)) |
| 258 | |
| 259 | (define (database-reader file string->entry) |
| 260 | (lambda* (#:optional (file-or-port file)) |
| 261 | (define (read-entries port) |
| 262 | (let loop ((entries '())) |
| 263 | (match (read-line port) |
| 264 | ((? eof-object?) |
| 265 | (reverse entries)) |
| 266 | (line |
| 267 | (loop (cons (string->entry line) entries)))))) |
| 268 | |
| 269 | (if (port? file-or-port) |
| 270 | (read-entries file-or-port) |
| 271 | (call-with-input-file file-or-port |
| 272 | read-entries)))) |
| 273 | |
| 274 | (define read-passwd |
| 275 | (database-reader "/etc/passwd" string->password-entry)) |
| 276 | (define read-shadow |
| 277 | (database-reader "/etc/shadow" string->shadow-entry)) |
| 278 | (define read-group |
| 279 | (database-reader "/etc/group" string->group-entry)) |
| 280 | |
| 281 | \f |
| 282 | ;;; |
| 283 | ;;; Building databases. |
| 284 | ;;; |
| 285 | |
| 286 | (define-record-type* <allocation> |
| 287 | allocation make-allocation |
| 288 | allocation? |
| 289 | (ids allocation-ids (default vlist-null)) |
| 290 | (next-id allocation-next-id (default %id-min)) |
| 291 | (next-system-id allocation-next-system-id (default %system-id-max))) |
| 292 | |
| 293 | ;; Trick to avoid name clashes... |
| 294 | (define-syntax %allocation (identifier-syntax allocation)) |
| 295 | |
| 296 | ;; Minimum and maximum UIDs and GIDs (from find_new_uid.c and find_new_gid.c |
| 297 | ;; in Shadow.) |
| 298 | (define %id-min 1000) |
| 299 | (define %id-max 60000) |
| 300 | |
| 301 | (define %system-id-min 100) |
| 302 | (define %system-id-max 999) |
| 303 | |
| 304 | (define (system-id? id) |
| 305 | (and (> id %system-id-min) |
| 306 | (<= id %system-id-max))) |
| 307 | |
| 308 | (define (user-id? id) |
| 309 | (and (>= id %id-min) |
| 310 | (< id %id-max))) |
| 311 | |
| 312 | (define* (allocate-id assignment #:key system?) |
| 313 | "Return two values: a newly allocated ID, and an updated <allocation> record |
| 314 | based on ASSIGNMENT. If SYSTEM? is true, return a system ID." |
| 315 | (define next |
| 316 | ;; Return the next available ID, looping if necessary. |
| 317 | (if system? |
| 318 | (lambda (id) |
| 319 | (let ((next-id (- id 1))) |
| 320 | (if (< next-id %system-id-min) |
| 321 | %system-id-max |
| 322 | next-id))) |
| 323 | (lambda (id) |
| 324 | (let ((next-id (+ id 1))) |
| 325 | (if (>= next-id %id-max) |
| 326 | %id-min |
| 327 | next-id))))) |
| 328 | |
| 329 | (let loop ((id (if system? |
| 330 | (allocation-next-system-id assignment) |
| 331 | (allocation-next-id assignment)))) |
| 332 | (if (vhash-assv id (allocation-ids assignment)) |
| 333 | (loop (next id)) |
| 334 | (let ((taken (vhash-consv id #t (allocation-ids assignment)))) |
| 335 | (values (if system? |
| 336 | (allocation (inherit assignment) |
| 337 | (next-system-id (next id)) |
| 338 | (ids taken)) |
| 339 | (allocation (inherit assignment) |
| 340 | (next-id (next id)) |
| 341 | (ids taken))) |
| 342 | id))))) |
| 343 | |
| 344 | (define* (reserve-ids allocation ids #:key (skip? #t)) |
| 345 | "Mark the numbers listed in IDS as reserved in ALLOCATION. When SKIP? is |
| 346 | true, start allocation after the highest (or lowest, depending on whether it's |
| 347 | a system ID allocation) number among IDS." |
| 348 | (%allocation |
| 349 | (inherit allocation) |
| 350 | (next-id (if skip? |
| 351 | (+ (reduce max |
| 352 | (- (allocation-next-id allocation) 1) |
| 353 | (filter user-id? ids)) |
| 354 | 1) |
| 355 | (allocation-next-id allocation))) |
| 356 | (next-system-id |
| 357 | (if skip? |
| 358 | (- (reduce min |
| 359 | (+ 1 (allocation-next-system-id allocation)) |
| 360 | (filter system-id? ids)) |
| 361 | 1) |
| 362 | (allocation-next-system-id allocation))) |
| 363 | (ids (fold (cut vhash-consv <> #t <>) |
| 364 | (allocation-ids allocation) |
| 365 | ids)))) |
| 366 | |
| 367 | (define (allocated? allocation id) |
| 368 | "Return true if ID is already allocated as part of ALLOCATION." |
| 369 | (->bool (vhash-assv id (allocation-ids allocation)))) |
| 370 | |
| 371 | (define (lookup-procedure lst key) |
| 372 | "Return a lookup procedure for the elements of LST, calling KEY to obtain |
| 373 | the key of each element." |
| 374 | (let ((table (fold (lambda (obj table) |
| 375 | (vhash-cons (key obj) obj table)) |
| 376 | vlist-null |
| 377 | lst))) |
| 378 | (lambda (key) |
| 379 | (match (vhash-assoc key table) |
| 380 | (#f #f) |
| 381 | ((_ . value) value))))) |
| 382 | |
| 383 | (define* (allocate-groups groups members |
| 384 | #:optional (current-groups '())) |
| 385 | "Return a list of group entries for GROUPS, a list of <user-group>. Members |
| 386 | for each group are taken from MEMBERS, a vhash that maps group names to member |
| 387 | names. GIDs and passwords found in CURRENT-GROUPS, a list of group entries, |
| 388 | are reused." |
| 389 | (define gids |
| 390 | ;; Mark all the currently-used GIDs and the explicitly requested GIDs as |
| 391 | ;; reserved. |
| 392 | (reserve-ids (reserve-ids (allocation) |
| 393 | (map group-entry-gid current-groups)) |
| 394 | (filter-map user-group-id groups) |
| 395 | #:skip? #f)) |
| 396 | |
| 397 | (define previous-entry |
| 398 | (lookup-procedure current-groups group-entry-name)) |
| 399 | |
| 400 | (reverse |
| 401 | (fold2 (lambda (group result allocation) |
| 402 | (let ((name (user-group-name group)) |
| 403 | (password (user-group-password group)) |
| 404 | (requested-id (user-group-id group)) |
| 405 | (system? (user-group-system? group))) |
| 406 | (let*-values (((previous) |
| 407 | (previous-entry name)) |
| 408 | ((allocation id) |
| 409 | (cond |
| 410 | ((number? requested-id) |
| 411 | (values (reserve-ids allocation |
| 412 | (list requested-id)) |
| 413 | requested-id)) |
| 414 | (previous |
| 415 | (values allocation |
| 416 | (group-entry-gid previous))) |
| 417 | (else |
| 418 | (allocate-id allocation |
| 419 | #:system? system?))))) |
| 420 | (values (cons (group-entry |
| 421 | (name name) |
| 422 | (password |
| 423 | (if previous |
| 424 | (group-entry-password previous) |
| 425 | password)) |
| 426 | (gid id) |
| 427 | (members (vhash-fold* cons '() name members))) |
| 428 | result) |
| 429 | allocation)))) |
| 430 | '() |
| 431 | gids |
| 432 | groups))) |
| 433 | |
| 434 | (define* (allocate-passwd users groups #:optional (current-passwd '())) |
| 435 | "Return a list of password entries for USERS, a list of <user-account>. |
| 436 | Take GIDs from GROUPS, a list of group entries. Reuse UIDs from |
| 437 | CURRENT-PASSWD, a list of password entries, when possible; otherwise allocate |
| 438 | new UIDs." |
| 439 | (define uids |
| 440 | (reserve-ids (reserve-ids (allocation) |
| 441 | (map password-entry-uid current-passwd)) |
| 442 | (filter-map user-account-uid users) |
| 443 | #:skip? #f)) |
| 444 | |
| 445 | (define previous-entry |
| 446 | (lookup-procedure current-passwd password-entry-name)) |
| 447 | |
| 448 | (define (group-id name) |
| 449 | (or (any (lambda (entry) |
| 450 | (and (string=? (group-entry-name entry) name) |
| 451 | (group-entry-gid entry))) |
| 452 | groups) |
| 453 | (error "group not found" name))) |
| 454 | |
| 455 | (reverse |
| 456 | (fold2 (lambda (user result allocation) |
| 457 | (let ((name (user-account-name user)) |
| 458 | (requested-id (user-account-uid user)) |
| 459 | (group (user-account-group user)) |
| 460 | (real-name (user-account-comment user)) |
| 461 | (directory (user-account-home-directory user)) |
| 462 | (shell (user-account-shell user)) |
| 463 | (system? (user-account-system? user))) |
| 464 | (let*-values (((previous) |
| 465 | (previous-entry name)) |
| 466 | ((allocation id) |
| 467 | (cond |
| 468 | ((number? requested-id) |
| 469 | (values (reserve-ids allocation |
| 470 | (list requested-id)) |
| 471 | requested-id)) |
| 472 | (previous |
| 473 | (values allocation |
| 474 | (password-entry-uid previous))) |
| 475 | (else |
| 476 | (allocate-id allocation |
| 477 | #:system? system?))))) |
| 478 | (values (cons (password-entry |
| 479 | (name name) |
| 480 | (uid id) |
| 481 | (directory directory) |
| 482 | (gid (if (number? group) group (group-id group))) |
| 483 | (real-name (if previous |
| 484 | (password-entry-real-name previous) |
| 485 | real-name)) |
| 486 | |
| 487 | ;; Do not reuse the shell of PREVIOUS since (1) |
| 488 | ;; that could lead to confusion, and (2) the |
| 489 | ;; shell might have been GC'd. See |
| 490 | ;; <https://lists.gnu.org/archive/html/guix-devel/2019-04/msg00478.html>. |
| 491 | (shell shell)) |
| 492 | result) |
| 493 | allocation)))) |
| 494 | '() |
| 495 | uids |
| 496 | users))) |
| 497 | |
| 498 | (define* (days-since-epoch #:optional (current-time current-time)) |
| 499 | "Return the number of days elapsed since the 1st of January, 1970." |
| 500 | (let* ((now (current-time time-utc)) |
| 501 | (epoch (make-time time-utc 0 0)) |
| 502 | (diff (time-difference now epoch))) |
| 503 | (quotient (time-second diff) (* 24 3600)))) |
| 504 | |
| 505 | (define* (passwd->shadow users passwd #:optional (current-shadow '()) |
| 506 | #:key (current-time current-time)) |
| 507 | "Return a list of shadow entries for the password entries listed in PASSWD. |
| 508 | Reuse shadow entries from CURRENT-SHADOW when they exist, and take the initial |
| 509 | password from USERS." |
| 510 | (define previous-entry |
| 511 | (lookup-procedure current-shadow shadow-entry-name)) |
| 512 | |
| 513 | (define now |
| 514 | (days-since-epoch current-time)) |
| 515 | |
| 516 | (map (lambda (user passwd) |
| 517 | (or (previous-entry (password-entry-name passwd)) |
| 518 | (shadow-entry (name (password-entry-name passwd)) |
| 519 | (password (user-account-password user)) |
| 520 | (last-change now)))) |
| 521 | users passwd)) |
| 522 | |
| 523 | (define (empty-if-not-found thunk) |
| 524 | "Call THUNK and return the empty list if that throws to ENOENT." |
| 525 | (catch 'system-error |
| 526 | thunk |
| 527 | (lambda args |
| 528 | (if (= ENOENT (system-error-errno args)) |
| 529 | '() |
| 530 | (apply throw args))))) |
| 531 | |
| 532 | (define* (user+group-databases users groups |
| 533 | #:key |
| 534 | (current-passwd |
| 535 | (empty-if-not-found read-passwd)) |
| 536 | (current-groups |
| 537 | (empty-if-not-found read-group)) |
| 538 | (current-shadow |
| 539 | (empty-if-not-found read-shadow)) |
| 540 | (current-time current-time)) |
| 541 | "Return three values: the list of group entries, the list of password |
| 542 | entries, and the list of shadow entries corresponding to USERS and GROUPS. |
| 543 | Preserve stateful bits from CURRENT-PASSWD, CURRENT-GROUPS, and |
| 544 | CURRENT-SHADOW: UIDs, GIDs, passwords, user shells, etc." |
| 545 | (define members |
| 546 | ;; Map group name to user names. |
| 547 | (fold (lambda (user members) |
| 548 | (fold (cute vhash-cons <> (user-account-name user) <>) |
| 549 | members |
| 550 | (user-account-supplementary-groups user))) |
| 551 | vlist-null |
| 552 | users)) |
| 553 | |
| 554 | (define group-entries |
| 555 | (allocate-groups groups members current-groups)) |
| 556 | |
| 557 | (define passwd-entries |
| 558 | (allocate-passwd users group-entries current-passwd)) |
| 559 | |
| 560 | (define shadow-entries |
| 561 | (passwd->shadow users passwd-entries current-shadow |
| 562 | #:current-time current-time)) |
| 563 | |
| 564 | (values group-entries passwd-entries shadow-entries)) |