| 1 | ;;; GNU Guix --- Functional package management for GNU |
| 2 | ;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2019, 2020 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 system pam) |
| 20 | #:use-module (guix records) |
| 21 | #:use-module (guix derivations) |
| 22 | #:use-module (guix gexp) |
| 23 | #:use-module (gnu services) |
| 24 | #:use-module (ice-9 match) |
| 25 | #:use-module (srfi srfi-1) |
| 26 | #:use-module (srfi srfi-9) |
| 27 | #:use-module (srfi srfi-11) |
| 28 | #:use-module (srfi srfi-26) |
| 29 | #:use-module ((guix utils) #:select (%current-system)) |
| 30 | #:export (pam-service |
| 31 | pam-service-name |
| 32 | pam-service-account |
| 33 | pam-service-auth |
| 34 | pam-service-password |
| 35 | pam-service-session |
| 36 | |
| 37 | pam-entry |
| 38 | pam-entry-control |
| 39 | pam-entry-module |
| 40 | pam-entry-arguments |
| 41 | |
| 42 | pam-limits-entry |
| 43 | pam-limits-entry-domain |
| 44 | pam-limits-entry-type |
| 45 | pam-limits-entry-item |
| 46 | pam-limits-entry-value |
| 47 | pam-limits-entry->string |
| 48 | |
| 49 | pam-services->directory |
| 50 | unix-pam-service |
| 51 | base-pam-services |
| 52 | |
| 53 | session-environment-service |
| 54 | session-environment-service-type |
| 55 | |
| 56 | pam-root-service-type |
| 57 | pam-root-service)) |
| 58 | |
| 59 | ;;; Commentary: |
| 60 | ;;; |
| 61 | ;;; Configuration of the pluggable authentication modules (PAM). |
| 62 | ;;; |
| 63 | ;;; Code: |
| 64 | |
| 65 | ;; PAM services (see |
| 66 | ;; <http://www.linux-pam.org/Linux-PAM-html/sag-configuration-file.html>.) |
| 67 | (define-record-type* <pam-service> pam-service |
| 68 | make-pam-service |
| 69 | pam-service? |
| 70 | (name pam-service-name) ; string |
| 71 | |
| 72 | ;; The four "management groups". |
| 73 | (account pam-service-account ; list of <pam-entry> |
| 74 | (default '())) |
| 75 | (auth pam-service-auth |
| 76 | (default '())) |
| 77 | (password pam-service-password |
| 78 | (default '())) |
| 79 | (session pam-service-session |
| 80 | (default '()))) |
| 81 | |
| 82 | (define-record-type* <pam-entry> pam-entry |
| 83 | make-pam-entry |
| 84 | pam-entry? |
| 85 | (control pam-entry-control) ; string |
| 86 | (module pam-entry-module) ; file name |
| 87 | (arguments pam-entry-arguments ; list of string-valued g-expressions |
| 88 | (default '()))) |
| 89 | |
| 90 | ;; PAM limits entries are used by the pam_limits PAM module to set or override |
| 91 | ;; limits on system resources for user sessions. The format is specified |
| 92 | ;; here: http://linux-pam.org/Linux-PAM-html/sag-pam_limits.html |
| 93 | (define-record-type <pam-limits-entry> |
| 94 | (make-pam-limits-entry domain type item value) |
| 95 | pam-limits-entry? |
| 96 | (domain pam-limits-entry-domain) ; string |
| 97 | (type pam-limits-entry-type) ; symbol |
| 98 | (item pam-limits-entry-item) ; symbol |
| 99 | (value pam-limits-entry-value)) ; symbol or number |
| 100 | |
| 101 | (define (pam-limits-entry domain type item value) |
| 102 | "Construct a pam-limits-entry ensuring that the provided values are valid." |
| 103 | (define (valid? value) |
| 104 | (case item |
| 105 | ((priority) (number? value)) |
| 106 | ((nice) (and (number? value) |
| 107 | (>= value -20) |
| 108 | (<= value 19))) |
| 109 | (else (or (and (number? value) |
| 110 | (>= value -1)) |
| 111 | (member value '(unlimited infinity)))))) |
| 112 | (define items |
| 113 | (list 'core 'data 'fsize |
| 114 | 'memlock 'nofile 'rss |
| 115 | 'stack 'cpu 'nproc |
| 116 | 'as 'maxlogins 'maxsyslogins |
| 117 | 'priority 'locks 'sigpending |
| 118 | 'msgqueue 'nice 'rtprio)) |
| 119 | (when (not (member type '(hard soft both))) |
| 120 | (error "invalid limit type" type)) |
| 121 | (when (not (member item items)) |
| 122 | (error "invalid limit item" item)) |
| 123 | (when (not (valid? value)) |
| 124 | (error "invalid limit value" value)) |
| 125 | (make-pam-limits-entry domain type item value)) |
| 126 | |
| 127 | (define (pam-limits-entry->string entry) |
| 128 | "Convert a pam-limits-entry record to a string." |
| 129 | (match entry |
| 130 | (($ <pam-limits-entry> domain type item value) |
| 131 | (string-join (list domain |
| 132 | (if (eq? type 'both) |
| 133 | "-" |
| 134 | (symbol->string type)) |
| 135 | (symbol->string item) |
| 136 | (cond |
| 137 | ((symbol? value) |
| 138 | (symbol->string value)) |
| 139 | (else |
| 140 | (number->string value)))) |
| 141 | " ")))) |
| 142 | |
| 143 | (define (pam-service->configuration service) |
| 144 | "Return the derivation building the configuration file for SERVICE, to be |
| 145 | dumped in /etc/pam.d/NAME, where NAME is the name of SERVICE." |
| 146 | (define (entry->gexp type entry) |
| 147 | (match entry |
| 148 | (($ <pam-entry> control module (arguments ...)) |
| 149 | #~(format #t "~a ~a ~a ~a~%" |
| 150 | #$type #$control #$module |
| 151 | (string-join (list #$@arguments)))))) |
| 152 | |
| 153 | (match service |
| 154 | (($ <pam-service> name account auth password session) |
| 155 | (define builder |
| 156 | #~(begin |
| 157 | (with-output-to-file #$output |
| 158 | (lambda () |
| 159 | #$@(append (map (cut entry->gexp "account" <>) account) |
| 160 | (map (cut entry->gexp "auth" <>) auth) |
| 161 | (map (cut entry->gexp "password" <>) password) |
| 162 | (map (cut entry->gexp "session" <>) session)) |
| 163 | #t)))) |
| 164 | |
| 165 | (computed-file name builder)))) |
| 166 | |
| 167 | (define (pam-services->directory services) |
| 168 | "Return the derivation to build the configuration directory to be used as |
| 169 | /etc/pam.d for SERVICES." |
| 170 | (let ((names (map pam-service-name services)) |
| 171 | (files (map pam-service->configuration services))) |
| 172 | (define builder |
| 173 | #~(begin |
| 174 | (use-modules (ice-9 match) |
| 175 | (srfi srfi-1)) |
| 176 | |
| 177 | (mkdir #$output) |
| 178 | (for-each (match-lambda |
| 179 | ((name file) |
| 180 | (symlink file (string-append #$output "/" name)))) |
| 181 | |
| 182 | ;; Since <pam-service> objects cannot be compared with |
| 183 | ;; 'equal?' since they contain gexps, which contain |
| 184 | ;; closures, use 'delete-duplicates' on the build-side |
| 185 | ;; instead. See <http://bugs.gnu.org/20037>. |
| 186 | (delete-duplicates '#$(zip names files))))) |
| 187 | |
| 188 | (computed-file "pam.d" builder))) |
| 189 | |
| 190 | (define %pam-other-services |
| 191 | ;; The "other" PAM configuration, which denies everything (see |
| 192 | ;; <http://www.linux-pam.org/Linux-PAM-html/sag-configuration-example.html>.) |
| 193 | (let ((deny (pam-entry |
| 194 | (control "required") |
| 195 | (module "pam_deny.so")))) |
| 196 | (pam-service |
| 197 | (name "other") |
| 198 | (account (list deny)) |
| 199 | (auth (list deny)) |
| 200 | (password (list deny)) |
| 201 | (session (list deny))))) |
| 202 | |
| 203 | (define unix-pam-service |
| 204 | (let ((unix (pam-entry |
| 205 | (control "required") |
| 206 | (module "pam_unix.so"))) |
| 207 | (env (pam-entry ; to honor /etc/environment. |
| 208 | (control "required") |
| 209 | (module "pam_env.so")))) |
| 210 | (lambda* (name #:key allow-empty-passwords? (allow-root? #f) motd |
| 211 | login-uid?) |
| 212 | "Return a standard Unix-style PAM service for NAME. When |
| 213 | ALLOW-EMPTY-PASSWORDS? is true, allow empty passwords. When ALLOW-ROOT? is |
| 214 | true, allow root to run the command without authentication. When MOTD is |
| 215 | true, it should be a file-like object used as the message-of-the-day. |
| 216 | When LOGIN-UID? is true, require the 'pam_loginuid' module; that module sets |
| 217 | /proc/self/loginuid, which the libc 'getlogin' function relies on." |
| 218 | ;; See <http://www.linux-pam.org/Linux-PAM-html/sag-configuration-example.html>. |
| 219 | (pam-service |
| 220 | (name name) |
| 221 | (account (list unix)) |
| 222 | (auth (append (if allow-root? |
| 223 | (list (pam-entry |
| 224 | (control "sufficient") |
| 225 | (module "pam_rootok.so"))) |
| 226 | '()) |
| 227 | (list (if allow-empty-passwords? |
| 228 | (pam-entry |
| 229 | (control "required") |
| 230 | (module "pam_unix.so") |
| 231 | (arguments '("nullok"))) |
| 232 | unix)))) |
| 233 | (password (list (pam-entry |
| 234 | (control "required") |
| 235 | (module "pam_unix.so") |
| 236 | ;; Store SHA-512 encrypted passwords in /etc/shadow. |
| 237 | (arguments '("sha512" "shadow"))))) |
| 238 | (session `(,@(if motd |
| 239 | (list (pam-entry |
| 240 | (control "optional") |
| 241 | (module "pam_motd.so") |
| 242 | (arguments |
| 243 | (list #~(string-append "motd=" #$motd))))) |
| 244 | '()) |
| 245 | ,@(if login-uid? |
| 246 | (list (pam-entry ;to fill in /proc/self/loginuid |
| 247 | (control "required") |
| 248 | (module "pam_loginuid.so"))) |
| 249 | '()) |
| 250 | ,env ,unix)))))) |
| 251 | |
| 252 | (define (rootok-pam-service command) |
| 253 | "Return a PAM service for COMMAND such that 'root' does not need to |
| 254 | authenticate to run COMMAND." |
| 255 | (let ((unix (pam-entry |
| 256 | (control "required") |
| 257 | (module "pam_unix.so")))) |
| 258 | (pam-service |
| 259 | (name command) |
| 260 | (account (list unix)) |
| 261 | (auth (list (pam-entry |
| 262 | (control "sufficient") |
| 263 | (module "pam_rootok.so")))) |
| 264 | (password (list unix)) |
| 265 | (session (list unix))))) |
| 266 | |
| 267 | (define* (base-pam-services #:key allow-empty-passwords?) |
| 268 | "Return the list of basic PAM services everyone would want." |
| 269 | ;; TODO: Add other Shadow programs? |
| 270 | (append (list %pam-other-services) |
| 271 | |
| 272 | ;; These programs are setuid-root. |
| 273 | (map (cut unix-pam-service <> |
| 274 | #:allow-empty-passwords? allow-empty-passwords?) |
| 275 | '("passwd" "sudo")) |
| 276 | ;; This is setuid-root, as well. Allow root to run "su" without |
| 277 | ;; authenticating. |
| 278 | (list (unix-pam-service "su" |
| 279 | #:allow-empty-passwords? allow-empty-passwords? |
| 280 | #:allow-root? #t)) |
| 281 | |
| 282 | ;; These programs are not setuid-root, and we want root to be able |
| 283 | ;; to run them without having to authenticate (notably because |
| 284 | ;; 'useradd' and 'groupadd' are run during system activation.) |
| 285 | (map rootok-pam-service |
| 286 | '("useradd" "userdel" "usermod" |
| 287 | "groupadd" "groupdel" "groupmod")))) |
| 288 | |
| 289 | \f |
| 290 | ;;; |
| 291 | ;;; System-wide environment variables. |
| 292 | ;;; |
| 293 | |
| 294 | (define (environment-variables->environment-file vars) |
| 295 | "Return a file for pam_env(8) that contains environment variables VARS." |
| 296 | (apply mixed-text-file "environment" |
| 297 | (append-map (match-lambda |
| 298 | ((key . value) |
| 299 | (list key "=" value "\n"))) |
| 300 | vars))) |
| 301 | |
| 302 | (define session-environment-service-type |
| 303 | (service-type |
| 304 | (name 'session-environment) |
| 305 | (extensions |
| 306 | (list (service-extension |
| 307 | etc-service-type |
| 308 | (lambda (vars) |
| 309 | (list `("environment" |
| 310 | ,(environment-variables->environment-file vars))))))) |
| 311 | (compose concatenate) |
| 312 | (extend append) |
| 313 | (description |
| 314 | "Populate @file{/etc/environment}, which is honored by @code{pam_env}, |
| 315 | with the specified environment variables. The value of this service is a list |
| 316 | of name/value pairs for environments variables, such as: |
| 317 | |
| 318 | @example |
| 319 | '((\"TZ\" . \"Canada/Pacific\")) |
| 320 | @end example\n"))) |
| 321 | |
| 322 | (define (session-environment-service vars) |
| 323 | "Return a service that builds the @file{/etc/environment}, which can be read |
| 324 | by PAM-aware applications to set environment variables for sessions. |
| 325 | |
| 326 | VARS should be an association list in which both the keys and the values are |
| 327 | strings or string-valued gexps." |
| 328 | (service session-environment-service-type vars)) |
| 329 | |
| 330 | |
| 331 | \f |
| 332 | ;;; |
| 333 | ;;; PAM root service. |
| 334 | ;;; |
| 335 | |
| 336 | ;; Overall PAM configuration: a list of services, plus a procedure that takes |
| 337 | ;; one <pam-service> and returns a <pam-service>. The procedure is used to |
| 338 | ;; implement cross-cutting concerns such as the use of the 'elogind.so' |
| 339 | ;; session module that keeps track of logged-in users. |
| 340 | (define-record-type* <pam-configuration> |
| 341 | pam-configuration make-pam-configuration? pam-configuration? |
| 342 | (services pam-configuration-services) ;list of <pam-service> |
| 343 | (transform pam-configuration-transform)) ;procedure |
| 344 | |
| 345 | (define (/etc-entry config) |
| 346 | "Return the /etc/pam.d entry corresponding to CONFIG." |
| 347 | (match config |
| 348 | (($ <pam-configuration> services transform) |
| 349 | (let ((services (map transform services))) |
| 350 | `(("pam.d" ,(pam-services->directory services))))))) |
| 351 | |
| 352 | (define (extend-configuration initial extensions) |
| 353 | "Extend INITIAL with NEW." |
| 354 | (let-values (((services procs) |
| 355 | (partition pam-service? extensions))) |
| 356 | (pam-configuration |
| 357 | (services (append (pam-configuration-services initial) |
| 358 | services)) |
| 359 | (transform (apply compose |
| 360 | (pam-configuration-transform initial) |
| 361 | procs))))) |
| 362 | |
| 363 | (define pam-root-service-type |
| 364 | (service-type (name 'pam) |
| 365 | (extensions (list (service-extension etc-service-type |
| 366 | /etc-entry))) |
| 367 | |
| 368 | ;; Arguments include <pam-service> as well as procedures. |
| 369 | (compose concatenate) |
| 370 | (extend extend-configuration) |
| 371 | (description |
| 372 | "Configure the Pluggable Authentication Modules (PAM) for all |
| 373 | the specified @dfn{PAM services}. Each PAM service corresponds to a program, |
| 374 | such as @command{login} or @command{sshd}, and specifies for instance how the |
| 375 | program may authenticate users or what it should do when opening a new |
| 376 | session."))) |
| 377 | |
| 378 | (define* (pam-root-service base #:key (transform identity)) |
| 379 | "The \"root\" PAM service, which collects <pam-service> instance and turns |
| 380 | them into a /etc/pam.d directory, including the <pam-service> listed in BASE. |
| 381 | TRANSFORM is a procedure that takes a <pam-service> and returns a |
| 382 | <pam-service>. It can be used to implement cross-cutting concerns that affect |
| 383 | all the PAM services." |
| 384 | (service pam-root-service-type |
| 385 | (pam-configuration (services base) |
| 386 | (transform transform)))) |
| 387 | |
| 388 | |