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812862db LP |
1 | --- |
2 | title: JSON User Records | |
5fe63895 | 3 | category: Users, Groups and Home Directories |
812862db LP |
4 | layout: default |
5 | --- | |
6 | ||
7 | # JSON User Records | |
8 | ||
9 | systemd optionally processes user records that go beyond the classic UNIX (or | |
10 | glibc NSS) `struct passwd`. Various components of systemd are able to provide | |
11 | and consume records in a more extensible format of a dictionary of key/value | |
12 | pairs, encoded as JSON. Specifically: | |
13 | ||
14 | 1. [`systemd-homed.service`](https://www.freedesktop.org/software/systemd/man/systemd-homed.service.html) | |
15 | manages `human` user home directories and embeds these JSON records | |
16 | directly in the home directory images (see [Home | |
afcb3e75 | 17 | Directories](https://systemd.io/HOME_DIRECTORY) for details). |
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18 | |
19 | 2. [`pam_systemd`](https://www.freedesktop.org/software/systemd/man/pam_systemd.html) | |
20 | processes these JSON records for users that log in, and applies various | |
21 | settings to the activated session, including environment variables, nice | |
22 | levels and more. | |
23 | ||
24 | 3. [`systemd-logind.service`](https://www.freedesktop.org/software/systemd/man/systemd-logind.service.html) | |
25 | processes these JSON records of users that log in, and applies various | |
26 | resource management settings to the per-user slice units it manages. This | |
27 | allows setting global limits on resource consumption by a specific user. | |
28 | ||
29 | 4. [`nss-systemd`](https://www.freedesktop.org/software/systemd/man/nss-systemd.html) | |
30 | is a glibc NSS module that synthesizes classic NSS records from these JSON | |
31 | records, providing full backwards compatibility with the classic UNIX APIs | |
32 | both for look-up and enumeration. | |
33 | ||
34 | 5. The service manager (PID 1) exposes dynamic users (i.e. users synthesized as | |
35 | effect of `DynamicUser=` in service unit files) as these advanced JSON | |
36 | records, making them discoverable to the rest of the system. | |
37 | ||
38 | 6. [`systemd-userdbd.service`](https://www.freedesktop.org/software/systemd/man/systemd-userdbd.service.html) | |
39 | is a small service that can translate UNIX/glibc NSS records to these JSON | |
40 | user records. It also provides a unified [Varlink](https://varlink.org/) API | |
41 | for querying and enumerating records of this type, optionally acquiring them | |
42 | from various other services. | |
43 | ||
44 | JSON user records may contain various fields that are not available in `struct | |
45 | passwd`, and are extensible for other applications. For example, the record may | |
46 | contain information about: | |
47 | ||
48 | 1. Additional security credentials (PKCS#11 security token information, | |
49 | biometrical authentication information, SSH public key information) | |
50 | ||
51 | 2. Additional user metadata, such as a picture, email address, location string, | |
52 | preferred language or timezone | |
53 | ||
54 | 3. Resource Management settings (such as CPU/IO weights, memory and tasks | |
55 | limits, classic UNIX resource limits or nice levels) | |
56 | ||
57 | 4. Runtime parameters such as environment variables or the `nodev`, `noexec`, | |
58 | `nosuid` flags to use for the home directory | |
59 | ||
60 | 5. Information about where to mount the home directory from | |
61 | ||
62 | And various other things. The record is intended to be extensible, for example | |
63 | the following extensions are envisioned: | |
64 | ||
65 | 1. Windows network credential information | |
66 | ||
67 | 2. Information about default IMAP, SMTP servers to use for this user | |
68 | ||
69 | 3. Parental control information to enforce on this user | |
70 | ||
71 | 4. Default parameters for backup applications and similar | |
72 | ||
73 | Similar to JSON User Records there are also [JSON Group | |
56b3eddb | 74 | Records](https://systemd.io/GROUP_RECORD) that encapsulate UNIX groups. |
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75 | |
76 | JSON User Records may be transferred or written to disk in various protocols | |
77 | and formats. To inquire about such records defined on the local system use the | |
56b3eddb | 78 | [User/Group Lookup API via Varlink](https://systemd.io/USER_GROUP_API). |
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79 | |
80 | ## Why JSON? | |
81 | ||
82 | JSON is nicely extensible and widely used. In particular it's easy to | |
83 | synthesize and process with numerous programming languages. It's particularly | |
84 | popular in the web communities, which hopefully should make it easy to link | |
85 | user credential data from the web and from local systems more closely together. | |
86 | ||
87 | ## General Structure | |
88 | ||
89 | The JSON user records generated and processed by systemd follow a general | |
90 | structure, consisting of seven distinct "sections". Specifically: | |
91 | ||
92 | 1. Various fields are placed at the top-level of user record (the `regular` | |
93 | section). These are generally fields that shall apply unconditionally to the | |
94 | user in all contexts, are portable and not security sensitive. | |
95 | ||
96 | 2. A number of fields are located in the `privileged` section (a sub-object of | |
97 | the user record). Fields contained in this object are security sensitive, | |
98 | i.e. contain information that the user and the administrator should be able | |
99 | to see, but other users should not. In many ways this matches the data | |
100 | stored in `/etc/shadow` in classic Linux user accounts, i.e. includes | |
101 | password hashes and more. Algorithmically, when a user record is passed to | |
102 | an untrusted client, by monopolizing such sensitive records in a single | |
103 | object field we can easily remove it from view. | |
104 | ||
105 | 3. A number of fields are located in objects inside the `perMachine` section | |
106 | (an array field of the user record). Primarily these are resource | |
107 | management-related fields, as those tend to make sense on a specific system | |
108 | only, e.g. limiting a user's memory use to 1G only makes sense on a specific | |
109 | system that has more than 1G of memory. Each object inside the `perMachine` | |
110 | array comes with a `matchMachineId` or `matchHostname` field which indicate | |
111 | which systems to apply the listed settings to. Note that many fields | |
112 | accepted in the `perMachine` section can also be set at the top level (the | |
113 | `regular` section), where they define the fallback if no matching object in | |
114 | `perMachine` is found. | |
115 | ||
116 | 4. Various fields are located in the `binding` section (a sub-sub-object of the | |
117 | user record; an intermediary object is inserted which is keyed by the | |
118 | machine ID of the host). Fields included in this section "bind" the object | |
119 | to a specific system. They generally include non-portable information about | |
120 | paths or UID assignments, that are true on a specific system, but not | |
121 | necessarily on others, and which are managed automatically by some user | |
122 | record manager (such as `systemd-homed`). Data in this section is considered | |
123 | part of the user record only in the local context, and is generally not | |
124 | ported to other systems. Due to that it is not included in the reduced user | |
125 | record the cryptographic signature defined in the `signature` section is | |
126 | calculated on. In `systemd-homed` this section is also removed when the | |
127 | user's record is stored in the `~/.identity` file in the home directory, so | |
128 | that every system with access to the home directory can manage these | |
129 | `binding` fields individually. Typically, the binding section is persisted | |
130 | to the local disk. | |
131 | ||
132 | 5. Various fields are located in the `status` section (a sub-sub-object of the | |
133 | user record, also with an intermediary object between that is keyed by the | |
134 | machine ID, similar to the way the `binding` section is organized). This | |
135 | section is augmented during runtime only, and never persisted to disk. The | |
136 | idea is that this section contains information about current runtime | |
137 | resource usage (for example: currently used disk space of the user), that | |
138 | changes dynamically but is otherwise immediately associated with the user | |
139 | record and for many purposes should be considered to be part of the user | |
140 | record. | |
141 | ||
142 | 6. The `signature` section contains one or more cryptographic signatures of a | |
143 | reduced version of the user record. This is used to ensure that only user | |
144 | records defined by a specific source are accepted on a system, by validating | |
145 | the signature against the set of locally accepted signature public keys. The | |
146 | signature is calculated from the JSON user record with all sections removed, | |
147 | except for `regular`, `privileged`, `perMachine`. Specifically, `binding`, | |
148 | `status`, `signature` itself and `secret` are removed first and thus not | |
149 | covered by the signature. This section is optional, and is only used when | |
150 | cryptographic validation of user records is required (as it is by | |
151 | `systemd-homed.service` for example). | |
152 | ||
153 | 7. The `secret` section contains secret user credentials, such as password or | |
154 | PIN information. This data is never persisted, and never returned when user | |
155 | records are inquired by a client, privileged or not. This data should only | |
156 | be included in a user record very briefly, for example when certain very | |
157 | specific operations are executed. For example, in tools such as | |
158 | `systemd-homed` this section may be included in user records, when creating | |
159 | a new home directory, as passwords and similar credentials need to be | |
160 | provided to encrypt the home directory with. | |
161 | ||
162 | Here's a tabular overview of the sections and their properties: | |
163 | ||
164 | | Section | Included in Signature | Persistent | Security Sensitive | Contains Host-Specific Data | | |
165 | |------------|-----------------------|------------|--------------------|-----------------------------| | |
166 | | regular | yes | yes | no | no | | |
167 | | privileged | yes | yes | yes | no | | |
168 | | perMachine | yes | yes | no | yes | | |
169 | | binding | no | yes | no | yes | | |
170 | | status | no | no | no | yes | | |
171 | | signature | no | yes | no | no | | |
172 | | secret | no | no | yes | no | | |
173 | ||
174 | Note that services providing user records to the local system are free to | |
175 | manage only a subset of these sections and never include the others in | |
176 | them. For example, a service that has no concept of signed records (for example | |
177 | because the records it manages are inherently trusted anyway) does not have to | |
178 | bother with the `signature` section. A service that only defines records in a | |
179 | strictly local context and without signatures doesn't have to deal with the | |
180 | `perMachine` or `binding` sections and can include its data exclusively in the | |
181 | regular section. A service that uses a separate, private channel for | |
182 | authenticating users (or that doesn't have a concept of authentication at all) | |
183 | does not need to to be concerned with the `secret` section of user records, as | |
184 | the fields included therein are only useful when executing authentication | |
185 | operations natively against JSON user records. | |
186 | ||
58345a23 | 187 | The `systemd-homed` manager uses all seven sections for various |
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188 | purposes. Inside the home directories (and if the LUKS2 backend is used, also |
189 | in the LUKS2 header) a user record containing the `regular`, `privileged`, | |
190 | `perMachine` and `signature` sections is stored. `systemd-homed` also stores a | |
191 | version of the record on the host, with the same four sections and augmented | |
192 | with an additional, fifth `binding` section. When a local client enquires about | |
193 | a user record managed by `systemd-homed` the service will add in some | |
194 | additional information about the user and home directory in the `status` | |
195 | section — this version is only transferred via IPC and never written to | |
196 | disk. Finally the `secret` section is used during authentication operations via | |
197 | IPC to transfer the user record along with its authentication tokens in one go. | |
198 | ||
199 | ## Fields in the `regular` section | |
200 | ||
201 | As mentioned, the `regular` section's fields are placed at the top level | |
202 | object. The following fields are currently defined: | |
203 | ||
204 | `userName` → The UNIX user name for this record. Takes a string with a valid | |
205 | UNIX user name. This field is the only mandatory field, all others are | |
206 | optional. Corresponds with the `pw_name` field of of `struct passwd` and the | |
207 | `sp_namp` field of `struct spwd` (i.e. the shadow user record stored in | |
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208 | `/etc/shadow`). See [User/Group Name Syntax](https://systemd.io/USER_NAMES) for |
209 | the (relaxed) rules the various systemd components enforce on user/group names. | |
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210 | |
211 | `realm` → The "realm" a user is defined in. This concept allows distinguishing | |
212 | users with the same name that originate in different organizations or | |
213 | installations. This should take a string in DNS domain syntax, but doesn't have | |
214 | to refer to an actual DNS domain (though it is recommended to use one for | |
215 | this). The idea is that the user `lpoetter` in the `redhat.com` realm might be | |
216 | distinct from the same user in the `poettering.hq` realm. User records for the | |
217 | same user name that have different realm fields are considered referring to | |
218 | different users. When updating a user record it is required that any new | |
219 | version has to match in both `userName` and `realm` field. This field is | |
220 | optional, when unset the user should not be considered part of any realm. A | |
221 | user record with a realm set is never compatible (for the purpose of updates, | |
222 | see above) with a user record without one set, even if the `userName` field matches. | |
223 | ||
224 | `realName` → The real name of the user, a string. This should contain the user's | |
225 | real ("human") name, and corresponds loosely to the GECOS field of classic UNIX | |
226 | user records. When converting a `struct passwd` to a JSON user record this | |
227 | field is initialized from GECOS (i.e. the `pw_gecos` field), and vice versa | |
228 | when converting back. That said, unlike GECOS this field is supposed to contain | |
229 | only the real name and no other information. | |
230 | ||
231 | `emailAddress` → The email address of the user, formatted as | |
232 | string. [`pam_systemd`](https://www.freedesktop.org/software/systemd/man/pam_systemd.html) | |
233 | initializes the `$EMAIL` environment variable from this value for all login | |
234 | sessions. | |
235 | ||
236 | `iconName` → The name of an icon picked by the user, for example for the | |
237 | purpose of an avatar. This must be a string, and should follow the semantics | |
238 | defined in the [Icon Naming | |
239 | Specification](https://standards.freedesktop.org/icon-naming-spec/icon-naming-spec-latest.html). | |
240 | ||
241 | `location` → A free-form location string describing the location of the user, | |
242 | if that is applicable. It's probably wise to use a location string processable | |
243 | by geo-location subsystems, but this is not enforced nor required. Example: | |
244 | `Berlin, Germany` or `Basement, Room 3a`. | |
245 | ||
246 | `disposition` → A string, one of `intrinsic`, `system`, `dynamic`, `regular`, | |
247 | `container`, `reserved`. If specified clarifies the disposition of the user, | |
248 | i.e. the context it is defined in. For regular, "human" users this should be | |
249 | `regular`, for system users (i.e. users that system services run under, and | |
250 | similar) this should be `system`. The `intrinsic` disposition should be used | |
251 | only for the two users that have special meaning to the OS kernel itself, | |
252 | i.e. the `root` and `nobody` users. The `container` string should be used for | |
253 | users that are used by an OS container, and hence will show up in `ps` listings | |
254 | and such, but are only defined in container context. Finally `reserved` should | |
255 | be used for any users outside of these use-cases. Note that this property is | |
256 | entirely optional and applications are assumed to be able to derive the | |
257 | disposition of a user automatically from a record even in absence of this | |
258 | field, based on other fields, for example the numeric UID. By setting this | |
259 | field explicitly applications can override this default determination. | |
260 | ||
261 | `lastChangeUSec` → An unsigned 64bit integer value, referring to a timestamp in µs | |
262 | since the epoch 1970, indicating when the user record (specifically, any of the | |
263 | `regular`, `privileged`, `perMachine` sections) was last changed. This field is | |
264 | used when comparing two records of the same user to identify the newer one, and | |
265 | is used for example for automatic updating of user records, where appropriate. | |
266 | ||
267 | `lastPasswordChangeUSec` → Similar, also an unsigned 64bit integer value, | |
268 | indicating the point in time the password (or any authentication token) of the | |
269 | user was last changed. This corresponds to the `sp_lstchg` field of `struct | |
270 | spwd`, i.e. the matching field in the user shadow database `/etc/shadow`, | |
271 | though provides finer resolution. | |
272 | ||
273 | `shell` → A string, referring to the shell binary to use for terminal logins of | |
274 | this user. This corresponds with the `pw_shell` field of `struct passwd`, and | |
275 | should contain an absolute file system path. For system users not suitable for | |
276 | terminal log-in this field should not be set. | |
277 | ||
278 | `umask` → The `umask` to set for the user's login sessions. Takes an | |
279 | integer. Note that usually on UNIX the umask is noted in octal, but JSON's | |
280 | integers are generally written in decimal, hence in this context we denote it | |
281 | umask in decimal too. The specified value should be in the valid range for | |
282 | umasks, i.e. 0000…0777 (in octal as typical in UNIX), or 0…511 (in decimal, how | |
283 | it actually appears in the JSON record). This `umask` is automatically set by | |
284 | [`pam_systemd`](https://www.freedesktop.org/software/systemd/man/pam_systemd.html) | |
285 | for all login sessions of the user. | |
286 | ||
287 | `environment` → An array of strings, each containing an environment variable | |
288 | and its value to set for the user's login session, in a format compatible with | |
289 | [`putenv()`](http://man7.org/linux/man-pages/man3/putenv.3.html). Any | |
290 | environment variable listed here is automatically set by | |
291 | [`pam_systemd`](https://www.freedesktop.org/software/systemd/man/pam_systemd.html) | |
292 | for all login sessions of the user. | |
293 | ||
294 | `timeZone` → A string indicating a preferred timezone to use for the user. When | |
295 | logging in | |
296 | [`pam_systemd`](https://www.freedesktop.org/software/systemd/man/pam_systemd.html) | |
297 | will automatically initialize the `$TZ` environment variable from this | |
298 | string. The string should be a `tzdata` compatible location string, for | |
299 | example: `Europe/Berlin`. | |
300 | ||
301 | `preferredLanguage` → A string indicating the preferred language/locale for the | |
302 | user. When logging in | |
303 | [`pam_systemd`](https://www.freedesktop.org/software/systemd/man/pam_systemd.html) | |
304 | will automatically initialize the `$LANG` environment variable from this | |
305 | string. The string hence should be in a format compatible with this environment | |
306 | variable, for example: `de_DE.UTF8`. | |
307 | ||
308 | `niceLevel` → An integer value in the range -20…19. When logging in | |
309 | [`pam_systemd`](https://www.freedesktop.org/software/systemd/man/pam_systemd.html) | |
310 | will automatically initialize the login process' nice level to this value with, | |
311 | which is then inherited by all the user's processes, see | |
312 | [`setpriority()`](http://man7.org/linux/man-pages/man2/setpriority.2.html) for | |
313 | more information. | |
314 | ||
315 | `resourceLimits` → An object, where each key refers to a Linux resource limit | |
316 | (such as `RLIMIT_NOFILE` and similar). Their values should be an object with | |
317 | two keys `cur` and `max` for the soft and hard resource limit. When logging in | |
318 | [`pam_systemd`](https://www.freedesktop.org/software/systemd/man/pam_systemd.html) | |
319 | will automatically initialize the login process' resource limits to these | |
320 | values, which is then inherited by all the user's processes, see | |
321 | [`setrlimit()`](http://man7.org/linux/man-pages/man2/setrlimit.2.html) for more | |
322 | information. | |
323 | ||
324 | `locked` → A boolean value. If true the user account is locked, the user may | |
325 | not log in. If this field is missing it should be assumed to be false, | |
326 | i.e. logins are permitted. This field corresponds to the `sp_expire` field of | |
327 | `struct spwd` (i.e. the `/etc/shadow` data for a user) being set to zero or | |
328 | one. | |
329 | ||
330 | `notBeforeUSec` → An unsigned 64bit integer value, indicating a time in µs since | |
331 | the UNIX epoch (1970) before which the record should be considered invalid for | |
332 | the purpose of logging in. | |
333 | ||
334 | `notAfterUSec` → Similar, but indicates the point in time *after* which logins | |
335 | shall not be permitted anymore. This corresponds to the `sp_expire` field of | |
336 | `struct spwd`, when it is set to a value larger than one, but provides finer | |
337 | granularity. | |
338 | ||
339 | `storage` → A string, one of `classic`, `luks`, `directory`, `subvolume`, | |
340 | `fscrypt`, `cifs`. Indicates the storage mechanism for the user's home | |
341 | directory. If `classic` the home directory is a plain directory as in classic | |
342 | UNIX. When `directory`, the home directory is a regular directory, but the | |
343 | `~/.identity` file in it contains the user's user record, so that the directory | |
344 | is self-contained. Similar, `subvolume` is a `btrfs` subvolume that also | |
345 | contains a `~/.identity` user record; `fscrypt` is an `fscrypt`-encrypted | |
346 | directory, also containing the `~/.identity` user record; `luks` is a per-user | |
347 | LUKS volume that is mounted as home directory, and `cifs` a home directory | |
348 | mounted from a Windows File Share. The five latter types are primarily used by | |
349 | `systemd-homed` when managing home directories, but may be used if other | |
350 | managers are used too. If this is not set `classic` is the implied default. | |
351 | ||
352 | `diskSize` → An unsigned 64bit integer, indicating the intended home directory | |
353 | disk space in bytes to assign to the user. Depending on the selected storage | |
354 | type this might be implement differently: for `luks` this is the intended size | |
355 | of the file system and LUKS volume, while for the others this likely translates | |
356 | to classic file system quota settings. | |
357 | ||
358 | `diskSizeRelative` → Similar to `diskSize` but takes a relative value, but | |
359 | specifies a fraction of the available disk space on the selected storage medium | |
360 | to assign to the user. This unsigned integer value is normalized to 2^32 = | |
361 | 100%. | |
362 | ||
363 | `skeletonDirectory` → Takes a string with the absolute path to the skeleton | |
364 | directory to populate a new home directory from. This is only used when a home | |
365 | directory is first created, and defaults to `/etc/skel` if not defined. | |
366 | ||
367 | `accessMode` → Takes an unsigned integer in the range 0…511 indicating the UNIX | |
368 | access mask for the home directory when it is first created. | |
369 | ||
370 | `tasksMax` → Takes an unsigned 64bit integer indicating the maximum number of | |
371 | tasks the user may start in parallel during system runtime. This value is | |
372 | enforced on all tasks (i.e. processes and threads) the user starts or that are | |
373 | forked off these processes regardless if the change user identity (for example | |
374 | by setuid binaries/`su`/`sudo` and | |
375 | similar). [`systemd-logind.service`](https://www.freedesktop.org/software/systemd/man/systemd-logind.service.html) | |
376 | enforces this by setting the `TasksMax` slice property for the user's slice | |
377 | `user-$UID.slice`. | |
378 | ||
379 | `memoryHigh`/`memoryMax` → These take unsigned 64bit integers indicating upper | |
380 | memory limits for all processes of the user (plus all processes forked off them | |
381 | that might have changed user identity), in bytes. Enforced by | |
382 | [`systemd-logind.service`](https://www.freedesktop.org/software/systemd/man/systemd-logind.service.html), | |
383 | similar to `tasksMax`. | |
384 | ||
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385 | `cpuWeight`/`ioWeight` → These take unsigned integers in the range 1…10000 |
386 | (defaults to 100) and configure the CPU and IO scheduling weights for the | |
387 | user's processes as a whole. Also enforced by | |
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388 | [`systemd-logind.service`](https://www.freedesktop.org/software/systemd/man/systemd-logind.service.html), |
389 | similar to `tasksMax`, `memoryHigh` and `memoryMax`. | |
390 | ||
391 | `mountNoDevices`/`mountNoSuid`/`mountNoExecute` → Three booleans that control | |
392 | the `nodev`, `nosuid`, `noexec` mount flags of the user's home | |
393 | directories. Note that these booleans are only honored if the home directory | |
394 | is managed by a subsystem such as `systemd-homed.service` that automatically | |
395 | mounts home directories on login. | |
396 | ||
397 | `cifsDomain` → A string indicating the Windows File Sharing domain (CIFS) to | |
398 | use. This is generally useful, but particularly when `cifs` is used as storage | |
399 | mechanism for the user's home directory, see above. | |
400 | ||
401 | `cifsUserName` → A string indicating the Windows File Sharing user name (CIFS) | |
402 | to associate this user record with. This is generally useful, but particularly | |
403 | useful when `cifs` is used as storage mechanism for the user's home directory, | |
404 | see above. | |
405 | ||
406 | `cifsService` → A string indicating the Windows File Share service (CIFS) to | |
407 | mount as home directory of the user on login. | |
408 | ||
409 | `imagePath` → A string with an absolute file system path to the file, directory | |
410 | or block device to use for storage backing the home directory. If the `luks` | |
411 | storage is used this refers to the loopback file or block device node to store | |
412 | the LUKS volume on. For `fscrypt`, `directory`, `subvolume` this refers to the | |
413 | directory to bind mount as home directory on login. Not defined for `classic` | |
414 | or `cifs`. | |
415 | ||
416 | `homeDirectory` → A string with an absolute file system path to the home | |
417 | directory. This is where the image indicated in `imagePath` is mounted to on | |
418 | login and thus indicates the application facing home directory while the home | |
419 | directory is active, and is what the user's `$HOME` environment variable is set | |
420 | to during log-in. It corresponds to the `pw_dir` field of `struct passwd`. | |
421 | ||
422 | `uid` → An unsigned integer in the range 0…4294967295: the numeric UNIX user ID (UID) to | |
423 | use for the user. This corresponds to the `pw_uid` field of `struct passwd`. | |
424 | ||
425 | `gid` → An unsigned integer in the range 0…4294967295: the numeric UNIX group | |
426 | ID (GID) to use for the user. This corresponds to the `pw_gid` field of | |
427 | `struct passwd`. | |
428 | ||
429 | `memberOf` → An array of strings, each indicating a UNIX group this user shall | |
430 | be a member of. The listed strings must be valid group names, but it is not | |
431 | required that all groups listed exist in all contexts: any entry for which no | |
432 | group exists should be silently ignored. | |
433 | ||
434 | `fileSystemType` → A string, one of `ext4`, `xfs`, `btrfs` (possibly others) to | |
435 | use as file system for the user's home directory. This is primarily relevant | |
436 | when the storage mechanism used is `luks` as a file system to use inside the | |
437 | LUKS container must be selected. | |
438 | ||
439 | `partitionUuid` → A string containing a lower-case, text-formatted UUID, referencing | |
440 | the GPT partition UUID the home directory is located in. This is primarily | |
441 | relevant when the storage mechanism used is `luks`. | |
442 | ||
443 | `luksUuid` → A string containing a lower-case, text-formatted UUID, referencing | |
444 | the LUKS volume UUID the home directory is located in. This is primarily | |
445 | relevant when the storage mechanism used is `luks`. | |
446 | ||
447 | `fileSystemUuid` → A string containing a lower-case, text-formatted UUID, | |
448 | referencing the file system UUID the home directory is located in. This is | |
449 | primarily relevant when the storage mechanism used is `luks`. | |
450 | ||
451 | `luksDiscard` → A boolean. If true and `luks` storage is used controls whether | |
452 | the loopback block devices, LUKS and the file system on top shall be used in | |
453 | `discard` mode, i.e. erased sectors should always be returned to the underlying | |
454 | storage. If false and `luks` storage is used turns this behavior off. In | |
455 | addition, depending on this setting an `FITRIM` or `fallocate()` operation is | |
456 | executed to make sure the image matches the selected option. | |
457 | ||
c0440512 LP |
458 | `luksOfflineDiscard` → A boolean. Similar to `luksDiscard`, it controls whether |
459 | to trim/allocate the file system/backing file when deactivating the home | |
460 | directory. | |
461 | ||
812862db LP |
462 | `luksCipher` → A string, indicating the cipher to use for the LUKS storage mechanism. |
463 | ||
464 | `luksCipherMode` → A string, selecting the cipher mode to use for the LUKS storage mechanism. | |
465 | ||
466 | `luksVolumeKeySize` → An unsigned integer, indicating the volume key length in | |
467 | bytes to use for the LUKS storage mechanism. | |
468 | ||
469 | `luksPbkdfHashAlgorithm` → A string, selecting the hash algorithm to use for | |
470 | the PBKDF operation for the LUKS storage mechanism. | |
471 | ||
472 | `luksPbkdfType` → A string, indicating the PBKDF type to use for the LUKS storage mechanism. | |
473 | ||
474 | `luksPbkdfTimeCostUSec` → An unsigned 64bit integer, indicating the intended | |
475 | time cost for the PBKDF operation, when the LUKS storage mechanism is used, in | |
476 | µs. | |
477 | ||
478 | `luksPbkdfMemoryCost` → An unsigned 64bit integer, indicating the intended | |
479 | memory cost for the PBKDF operation, when LUKS storage is used, in bytes. | |
480 | ||
481 | `luksPbkdfParallelThreads` → An unsigned 64bit integer, indicating the intended | |
482 | required parallel threads for the PBKDF operation, when LUKS storage is used. | |
483 | ||
484 | `service` → A string declaring the service that defines or manages this user | |
485 | record. It is recommended to use reverse domain name notation for this. For | |
486 | example, if `systemd-homed` manages a user a string of `io.systemd.Home` is | |
487 | used for this. | |
488 | ||
489 | `rateLimitIntervalUSec` → An unsigned 64bit integer that configures the | |
490 | authentication rate limiting enforced on the user account. This specifies a | |
491 | timer interval (in µs) within which to count authentication attempts. When the | |
492 | counter goes above the value configured n `rateLimitIntervalBurst` log-ins are | |
493 | temporarily refused until the interval passes. | |
494 | ||
495 | `rateLimitIntervalBurst` → An unsigned 64bit integer, closely related to | |
496 | `rateLimitIntervalUSec`, that puts a limit on authentication attempts within | |
497 | the configured time interval. | |
498 | ||
499 | `enforcePasswordPolicy` → A boolean. Configures whether to enforce the system's | |
500 | password policy when creating the home directory for the user or changing the | |
501 | user's password. By default the policy is enforced, but if this field is false | |
502 | it is bypassed. | |
503 | ||
504 | `autoLogin` → A boolean. If true the user record is marked as suitable for | |
505 | auto-login. Systems are supposed to automatically log in a user marked this way | |
506 | during boot, if there's exactly one user on it defined this way. | |
507 | ||
508 | `stopDelayUSec` → An unsigned 64bit integer, indicating the time in µs the | |
509 | per-user service manager is kept around after the user fully logged out. This | |
510 | value is honored by | |
511 | [`systemd-logind.service`](https://www.freedesktop.org/software/systemd/man/systemd-logind.service.html). If | |
512 | set to zero the per-user service manager is immediately terminated when the | |
513 | user logs out, and longer values optimize high-frequency log-ins as the | |
514 | necessary work to set up and tear down a log-in is reduced if the service | |
515 | manager stays running. | |
516 | ||
517 | `killProcesses` → A boolean. If true all processes of the user are | |
518 | automatically killed when the user logs out. This is enforced by | |
519 | [`systemd-logind.service`](https://www.freedesktop.org/software/systemd/man/systemd-logind.service.html). If | |
520 | false any processes left around when the user logs out are left running. | |
521 | ||
522 | `passwordChangeMinUSec`/`passwordChangeMaxUSec` → An unsigned 64bit integer, | |
523 | encoding how much time has to pass at least/at most between password changes of | |
524 | the user. This corresponds with the `sp_min` and `sp_max` fields of `struct | |
525 | spwd` (i.e. the `/etc/shadow` entries of the user), but offers finer | |
526 | granularity. | |
527 | ||
528 | `passwordChangeWarnUSec` → An unsigned 64bit integer, encoding how much time to | |
529 | warn the user before their password expires, in µs. This corresponds with the | |
530 | `sp_warn` field of `struct spwd`. | |
531 | ||
532 | `passwordChangeInactiveUSec` → An unsigned 64bit integer, encoding how much | |
533 | time has to pass after the password expired that the account is | |
534 | deactivated. This corresponds with the `sp_inact` field of `struct spwd`. | |
535 | ||
536 | `passwordChangeNow` → A boolean. If true the user has to change their password | |
537 | on next login. This corresponds with the `sp_lstchg` field of `struct spwd` | |
538 | being set to zero. | |
539 | ||
540 | `pkcs11TokenUri` → An array of strings, each with an RFC 7512 compliant PKCS#11 | |
541 | URI referring to security token (or smart card) of some form, that shall be | |
542 | associated with the user and may be used for authentication. The URI is used to | |
543 | search for an X.509 certificate and associated private key that may be used to | |
544 | decrypt an encrypted secret key that is used to unlock the user's account (see | |
545 | below). It's undefined how precise the URI is: during log-in it is tested | |
546 | against all plugged in security tokens and if there's exactly one matching | |
547 | private key found with it it is used. | |
548 | ||
e1ef1e5d | 549 | `privileged` → An object, which contains the fields of the `privileged` section |
812862db LP |
550 | of the user record, see below. |
551 | ||
552 | `perMachine` → An array of objects, which contain the `perMachine` section of | |
553 | the user record, and thus fields to apply on specific systems only, see below. | |
554 | ||
555 | `binding` → An object, keyed by machine IDs formatted as strings, pointing | |
556 | to objects that contain the `binding` section of the user record, | |
557 | i.e. additional fields that bind the user record to a specific machine, see | |
558 | below. | |
559 | ||
560 | `status` → An object, keyed by machine IDs formatted as strings, pointing to | |
561 | objects that contain the `status` section of the user record, i.e. additional | |
562 | runtime fields that expose the current status of the user record on a specific | |
563 | system, see below. | |
564 | ||
565 | `signature` → An array of objects, which contain cryptographic signatures of | |
566 | the user record, i.e. the fields of the `signature` section of the user record, | |
567 | see below. | |
568 | ||
569 | `secret` → An object, which contains the fields of the `secret` section of the | |
570 | user record, see below. | |
571 | ||
572 | ## Fields in the `privileged` section | |
573 | ||
574 | As mentioned, the `privileged` section is encoded in a sub-object of the user | |
575 | record top-level object, in the `privileged` field. Any data included in this | |
576 | object shall only be visible to the administrator and the user themselves, and | |
577 | be suppressed implicitly when other users get access to a user record. It thus | |
578 | takes the role of the `/etc/shadow` records for each user, which has similarly | |
579 | restrictive access semantics. The following fields are currently defined: | |
580 | ||
581 | `passwordHint` → A user-selected password hint in free-form text. This should | |
582 | be a string like "What's the name of your first pet?", but is entirely for the | |
583 | user to choose. | |
584 | ||
585 | `hashPassword` → An array of strings, each containing a hashed UNIX password | |
586 | string, in the format | |
587 | [`crypt(3)`](http://man7.org/linux/man-pages/man3/crypt.3.html) generates. This | |
588 | corresponds with `sp_pwdp` field of `struct spwd` (and in a way the `pw_passwd` | |
589 | field of `struct passwd`). | |
590 | ||
591 | `sshAuthorizedKeys` → An array of strings, each listing an SSH public key that | |
592 | is authorized to access the account. The strings should follow the same format | |
593 | as the lines in the traditional `~/.ssh/authorized_key` file. | |
594 | ||
595 | `pkcs11EncryptedKey` → An array of objects. Each element of the array should be | |
596 | an object consisting of three string fields: `uri` shall contain a PKCS#11 | |
597 | security token URI, `data` shall contain a Base64 encoded encrypted key and | |
598 | `hashedPassword` shall contain a UNIX password hash to test the key | |
599 | against. Authenticating with a security token against this account shall work | |
600 | as follows: the encrypted secret key is converted from its Base64 | |
601 | representation into binary, then decrypted with the PKCS#11 `C_Decrypt()` | |
602 | function of the PKCS#11 module referenced by the specified URI, using the | |
603 | private key found on the same token. The resulting decrypted key is then | |
604 | Base64-encoded and tested against the specified UNIX hashed password. The | |
605 | Base64-enceded decrypted key may also be used to unlock further resources | |
606 | during log-in, for example the LUKS or `fscrypt` storage backend. It is | |
607 | generally recommended that for each entry in `pkcs11EncryptedKey` there's also | |
608 | a matching one in `pkcs11TokenUri` and vice versa, with the same URI, appearing | |
609 | in the same order, but this should not be required by applications processing | |
610 | user records. | |
611 | ||
612 | ## Fields in the `perMachine` section | |
613 | ||
614 | As mentioned, the `perMachine` section contains settings that shall apply to | |
615 | specific systems only. This is primarily interesting for resource management | |
616 | properties as they tend to require a per-system focus, however they may be used | |
617 | for other purposes too. | |
618 | ||
619 | The `perMachine` field in the top-level object is an array of objects. When | |
620 | processing the user record first the various fields on the top-level object | |
621 | should be used. Then this array should be iterated in order, and the various | |
622 | settings be applied that match either the indicated machine ID or host | |
623 | name. There may be multiple array entries that match a specific system, in | |
624 | which case all the object's setting should be applied. If the same option is | |
625 | set in the top-level object as in a per-machine object the latter wins and | |
626 | entirely undoes the setting in the top-level object (i.e. no merging of | |
627 | properties that are arrays themselves is done). If the same option is set in | |
628 | multiple per-machine objects the one specified later in the array wins (and | |
629 | here too no merging of individual fields is done, the later field always wins | |
630 | in full). | |
631 | ||
632 | The following fields are defined in this section: | |
633 | ||
634 | `matchMachineId` → An array of strings with each a formatted 128bit ID in | |
635 | hex. If any of the specified IDs match the system's local machine ID | |
636 | (i.e. matches `/etc/machine-id`) the fields in this object are honored. | |
637 | ||
638 | `matchHostname` → An array of string with a each a valid hostname. If any of | |
639 | the specified hostnames match the system's local hostname, the fields in this | |
640 | object are honored. If both `matchHostname` and `matchMachineId` are used | |
641 | within the same array entry, the object is honored when either match succeeds, | |
642 | i.e. the two match types are combined in OR, not in AND. | |
643 | ||
644 | These two are the only two fields specific to this section. All other fields | |
645 | that may be used in this section are identical to the equally named ones in the | |
646 | `regular` section (i.e. at the top-level object). Specifically, these are: | |
647 | ||
648 | `iconName`, `location`, `shell`, `umask`, `environment`, `timeZone`, | |
649 | `preferredLanguage`, `niceLevel`, `resourceLimits`, `locked`, `notBeforeUSec`, | |
650 | `notAfterUSec`, `storage`, `diskSize`, `diskSizeRelative`, `skeletonDirectory`, | |
651 | `accessMode`, `tasksMax`, `memoryHigh`, `memoryMax`, `cpuWeight`, `ioWeight`, | |
652 | `mountNoDevices`, `mountNoSuid`, `mountNoExecute`, `cifsDomain`, | |
653 | `cifsUserName`, `cifsService`, `imagePath`, `uid`, `gid`, `memberOf`, | |
654 | `fileSystemType`, `partitionUuid`, `luksUuid`, `fileSystemUuid`, `luksDiscard`, | |
c0440512 LP |
655 | `luksOfflineDiscard`, `luksOfflineDiscard`, `luksCipher`, `luksCipherMode`, |
656 | `luksVolumeKeySize`, `luksPbkdfHashAlgorithm`, `luksPbkdfType`, | |
657 | `luksPbkdfTimeCostUSec`, `luksPbkdfMemoryCost`, `luksPbkdfParallelThreads`, | |
658 | `rateLimitIntervalUSec`, `rateLimitBurst`, `enforcePasswordPolicy`, | |
659 | `autoLogin`, `stopDelayUSec`, `killProcesses`, `passwordChangeMinUSec`, | |
660 | `passwordChangeMaxUSec`, `passwordChangeWarnUSec`, | |
812862db LP |
661 | `passwordChangeInactiveUSec`, `passwordChangeNow`, `pkcs11TokenUri`. |
662 | ||
663 | ## Fields in the `binding` section | |
664 | ||
665 | As mentioned, the `binding` section contains additional fields about the user | |
666 | record, that bind it to the local system. These fields are generally used by a | |
667 | local user manager (such as `systemd-homed.service`) to add in fields that make | |
668 | sense in a local context but not necessarily in a global one. For example, a | |
669 | user record that contains no `uid` field in the regular section is likely | |
670 | extended with one in the `binding` section to assign a local UID if no global | |
671 | UID is defined. | |
672 | ||
673 | All fields in the `binding` section only make sense in a local context and are | |
674 | suppressed when the user record is ported between systems. The `binding` section | |
675 | is generally persisted on the system but not in the home directories themselves | |
676 | and the home directory is supposed to be fully portable and thus not contain | |
677 | the information that `binding` is supposed to contain that binds the portable | |
678 | record to a specific system. | |
679 | ||
680 | The `binding` sub-object on the top-level user record object is keyed by the | |
681 | machine ID the binding is intended for, which point to an object with the | |
682 | fields of the bindings. These fields generally match fields that may also be | |
683 | defined in the `regular` and `perMachine` sections, however override | |
684 | both. Usually, the `binding` value should not contain settings different from | |
685 | those set via `regular` or `perMachine`, however this might happen if some | |
686 | settings are not supported locally (think: `fscrypt` is recorded as intended | |
687 | storage mechanism in the `regular` section, but the local kernel does not | |
688 | support `fscrypt`, hence `directory` was chosen as implicit fallback), or have | |
689 | been changed in the `regular` section through updates (e.g. a home directory | |
690 | was created with `luks` as storage mechanism but later the user record was | |
691 | updated to prefer `subvolume`, which however doesn't change the actual storage | |
692 | used already which is pinned in the `binding` section). | |
693 | ||
694 | The following fields are defined in the `binding` section. They all have an | |
695 | identical format and override their equally named counterparts in the `regular` | |
696 | and `perMachine` sections: | |
697 | ||
698 | `imagePath`, `homeDirectory`, `partitionUuid`, `luksUuid`, `fileSystemUuid`, | |
699 | `uid`, `gid`, `storage`, `fileSystemType`, `luksCipher`, `luksCipherMode`, | |
700 | `luksVolumeKeySize`. | |
701 | ||
702 | ## Fields in the `status` section | |
703 | ||
704 | As mentioned, the `status` section contains additional fields about the user | |
705 | record that are exclusively acquired during runtime, and that expose runtime | |
706 | metrics of the user and similar metadata that shall not be persisted but are | |
707 | only acquired "on-the-fly" when requested. | |
708 | ||
709 | This section is arranged similarly to the `binding` section: the `status` | |
710 | sub-object of the top-level user record object is keyed by the machine ID, | |
711 | which points to the object with the fields defined here. The following fields | |
712 | are defined: | |
713 | ||
714 | `diskUsage` → An unsigned 64bit integer. The currently used disk space of the | |
715 | home directory in bytes. This value might be determined in different ways, | |
716 | depending on the selected storage mechanism. For LUKS storage this is the file | |
717 | size of the loopback file or block device size. For the | |
718 | directory/subvolume/fscrypt storage this is the current disk space used as | |
719 | reported by the file system quota subsystem. | |
720 | ||
721 | `diskFree` → An unsigned 64bit integer, denoting the number of "free" bytes in | |
722 | the disk space allotment, i.e. usually the difference between the disk size as | |
723 | reported by `diskSize` and the used already as reported in `diskFree`, but | |
724 | possibly skewed by metadata sizes, disk compression and similar. | |
725 | ||
726 | `diskSize` → An unsigned 64bit integer, denoting the disk space currently | |
727 | allotted to the user, in bytes. Depending on the storage mechanism this can mean | |
728 | different things (see above). In contrast to the top-level field of the same | |
729 | (or the one in the `perMachine` section), this field reports the current size | |
730 | allotted to the user, not the intended one. The values may differ when user | |
731 | records are updated without the home directory being re-sized. | |
732 | ||
733 | `diskCeiling`/`diskFloor` → Unsigned 64bit integers indicating upper and lower | |
734 | bounds when changing the `diskSize` value, in bytes. These values are typically | |
735 | derived from the underlying data storage, and indicate in which range the home | |
736 | directory may be re-sized in, i.e. in which sensible range the `diskSize` value | |
737 | should be kept. | |
738 | ||
739 | `state` → A string indicating the current state of the home directory. The | |
740 | precise set of values exposed here are up to the service managing the home | |
741 | directory to define (i.e. are up to the service identified with the `service` | |
742 | field below). However, it is recommended to stick to a basic vocabulary here: | |
743 | `inactive` for a home directory currently not mounted, `absent` for a home | |
744 | directory that cannot be mounted currently because it does not exist on the | |
745 | local system, `active` for a home directory that is currently mounted and | |
746 | accessible. | |
747 | ||
748 | `service` → A string identifying the service that manages this user record. For | |
749 | example `systemd-homed.service` sets this to `io.systemd.Home` to all user | |
750 | records it manages. This is particularly relevant to define clearly the context | |
751 | in which `state` lives, see above. Note that this field also exists on the | |
752 | top-level object (i.e. in the `regular` section), which it overrides. The | |
753 | `regular` field should be used if conceptually the user record can only be | |
754 | managed by the specified service, and this `status` field if it can | |
755 | conceptually be managed by different managers, but currently is managed by the | |
756 | specified one. | |
757 | ||
758 | `signedLocally` → A boolean. If true indicates that the user record is signed | |
759 | by a public key for which the private key is available locally. This means that | |
760 | the user record may be modified locally as it can be re-signed with the private | |
761 | key. If false indicates that the user record is signed by a public key | |
762 | recognized by the local manager but whose private key is not available | |
763 | locally. This means the user record cannot be modified locally as it couldn't | |
764 | be signed afterwards. | |
765 | ||
766 | `goodAuthenticationCounter` → An unsigned 64bit integer. This counter is | |
767 | increased by one on every successful authentication attempt, i.e. an | |
768 | authentication attempt where a security token of some form was presented and it | |
769 | was correct. | |
770 | ||
771 | `badAuthenticationCounter` → An unsigned 64bit integer. This counter is | |
772 | increased by one on every unsuccessfully authentication attempt, i.e. an | |
773 | authentication attempt where a security token of some form was presented and it | |
774 | was incorrect. | |
775 | ||
776 | `lastGoodAuthenticationUSec` → An unsigned 64bit integer, indicating the time | |
777 | of the last successful authentication attempt in µs since the UNIX epoch (1970). | |
778 | ||
779 | `lastBadAuthenticationUSec` → Similar, but the timestamp of the last | |
780 | unsuccessfully authentication attempt. | |
781 | ||
782 | `rateLimitBeginUSec` → An unsigned 64bit integer: the µs timestamp since the | |
783 | UNIX epoch (1970) where the most recent rate limiting interval has been | |
784 | started, as configured with `rateLimitIntervalUSec`. | |
785 | ||
786 | `rateLimitCount` → An unsigned 64bit integer, counting the authentication | |
787 | attempts in the current rate limiting interval, see above. If this counter | |
788 | grows beyond the value configured in `rateLimitBurst` authentication attempts | |
789 | are temporarily refused. | |
790 | ||
791 | `removable` → A boolean value. If true the manager of this user record | |
792 | determined the home directory being on removable media. If false it was | |
793 | determined the home directory is in internal built-in media. (This is used by | |
794 | `systemd-logind.service` to automatically pick the right default value for | |
795 | `stopDelayUSec` if the field is not explicitly specified: for home directories | |
796 | on removable media the delay is selected very low to minimize the chance the | |
797 | home directory remains in unclean state if the storage device is removed from | |
798 | the system by the user). | |
799 | ||
800 | ## Fields in the `signature` section | |
801 | ||
802 | As mentioned, the `signature` section of the user record may contain one or | |
803 | more cryptographic signatures of the user record. Like all others, this section | |
804 | is optional, and only used when cryptographic validation of user records shall | |
805 | be used. Specifically, all user records managed by `systemd-homed.service` will | |
806 | carry such signatures and the service refuses managing user records that come | |
807 | without signature or with signatures not recognized by any locally defined | |
808 | public key. | |
809 | ||
810 | The `signature` field in the top-level user record object is an array of | |
811 | objects. Each object encapsulates one signature and has two fields: `data` and | |
812 | `key` (both are strings). The `data` field contains the actual signature, | |
813 | encoded in base64, the `key` field contains a copy of the public key whose | |
814 | private key was used to make the signature, in PEM format. Currently only | |
815 | signatures with Ed25519 keys are defined. | |
816 | ||
817 | Before signing the user record should be brought into "normalized" form, | |
818 | i.e. the keys in all objects should be sorted alphabetically. All redundant | |
819 | white-space and newlines should be removed and the JSON text then signed. | |
820 | ||
821 | The signatures only cover the `regular`, `perMachine` and `privileged` sections | |
822 | of the user records, all other sections (include `signature` itself), are | |
823 | removed before the signature is calculated. | |
824 | ||
825 | Rationale for signing and threat model: while a multi-user operating system | |
826 | like Linux strives for being sufficiently secure even after a user acquired a | |
827 | local login session reality tells us this is not the case. Hence it is | |
828 | essential to restrict carefully which users may gain access to a system and | |
829 | which ones shall not. A minimal level of trust must be established between | |
830 | system, user record and the user themselves before a log-in request may be | |
831 | permitted. In particular if the home directory is provided in its own LUKS2 | |
832 | encapsulated file system it is essential this trust is established before the | |
833 | user logs in (and hence the file system mounted), since file system | |
834 | implementations on Linux are well known to be relatively vulnerable to rogue | |
835 | disk images. User records and home directories in many context are expected to | |
836 | be something shareable between multiple systems, and the transfer between them | |
837 | might not happen via exclusively trusted channels. Hence it's essential that | |
838 | the user record is not manipulated between uses. Finally, resource management | |
839 | (which may be done by the various fields of the user record) is security | |
840 | sensitive, since it should forcefully lock the user into the assigned resource | |
841 | usage and not allow them to use more. The requirement of being able to trust | |
842 | the user record data combined with the potential transfer over untrusted | |
843 | channels suggest a cryptographic signature mechanism where only user records | |
844 | signed by a recognized key are permitted to log in locally. | |
845 | ||
846 | Note that other mechanisms for establishing sufficient trust exist too, and are | |
847 | perfectly valid as well. For example, systems like LDAP/ActiveDirectory | |
848 | generally insist on user record transfer from trusted servers via encrypted TLS | |
849 | channels only. Or traditional UNIX users created locally in `/etc/passwd` never | |
850 | exist outside of the local trusted system, hence transfer and trust in the | |
851 | source are not an issue. The major benefit of operating with signed user | |
852 | records is that they are self-sufficiently trusted, not relying on a secure | |
853 | channel for transfer, and thus being compatible with a more distributed model | |
854 | of home directory transfer, including on USB sticks and such. | |
855 | ||
856 | ## Fields in the `secret` section | |
857 | ||
858 | As mentioned, the `secret` section of the user record should never be persisted | |
859 | nor transferred across machines. It is only defined in short-lived operations, | |
860 | for example when a user record is first created or registered, as the secret | |
861 | key data needs to be available to derive encryption keys from and similar. | |
862 | ||
863 | The `secret` field of the top-level user record contains the following fields: | |
864 | ||
865 | `password` → an array of strings, each containing a plain text password. | |
866 | ||
867 | `pkcs11Pin` → an array of strings, each containing a plain text PIN, suitable | |
868 | for unlocking PKCS#11 security tokens that require that. | |
869 | ||
870 | `pkcs11ProtectedAuthenticationPathPermitted` → a boolean. If set to true allows | |
871 | the receiver to use the PKCS#11 "protected authentication path" (i.e. a | |
872 | physical button/touch element on the security token) for authenticating the | |
873 | user. If false or unset authentication this way shall not be attempted. | |
874 | ||
875 | ## Mapping to `struct passwd` and `struct spwd` | |
876 | ||
877 | When mapping classic UNIX user records (i.e. `struct passwd` and `struct spwd`) | |
878 | to JSON user records the following mappings should be applied: | |
879 | ||
880 | | Structure | Field | Section | Field | Condition | | |
881 | |-----------------|-------------|--------------|------------------------------|----------------------------| | |
882 | | `struct passwd` | `pw_name` | `regular` | `userName` | | | |
883 | | `struct passwd` | `pw_passwd` | `privileged` | `password` | (See notes below) | | |
884 | | `struct passwd` | `pw_uid` | `regular` | `uid` | | | |
885 | | `struct passwd` | `pw_gid` | `regular` | `gid` | | | |
886 | | `struct passwd` | `pw_gecos` | `regular` | `realName` | | | |
887 | | `struct passwd` | `pw_dir` | `regular` | `homeDirectory` | | | |
888 | | `struct passwd` | `pw_shell` | `regular` | `shell` | | | |
889 | | `struct spwd` | `sp_namp` | `regular` | `userName` | | | |
890 | | `struct spwd` | `sp_pwdp` | `privileged` | `password` | (See notes below) | | |
891 | | `struct spwd` | `sp_lstchg` | `regular` | `lastPasswordChangeUSec` | (if `sp_lstchg` > 0) | | |
892 | | `struct spwd` | `sp_lstchg` | `regular` | `passwordChangeNow` | (if `sp_lstchg` == 0) | | |
893 | | `struct spwd` | `sp_min` | `regular` | `passwordChangeMinUSec` | | | |
894 | | `struct spwd` | `sp_max` | `regular` | `passwordChangeMaxUSec` | | | |
895 | | `struct spwd` | `sp_warn` | `regular` | `passwordChangeWarnUSec` | | | |
896 | | `struct spwd` | `sp_inact` | `regular` | `passwordChangeInactiveUSec` | | | |
897 | | `struct spwd` | `sp_expire` | `regular` | `locked` | (if `sp_expire` in [0, 1]) | | |
898 | | `struct spwd` | `sp_expire` | `regular` | `notAfterUSec` | (if `sp_expire` > 1) | | |
899 | ||
900 | At this time almost all Linux machines employ shadow passwords, thus the | |
901 | `pw_passwd` field in `struct passwd` is set to `"x"`, and the actual password | |
902 | is stored in the shadow entry `struct spwd`'s field `sp_pwdp`. | |
903 | ||
904 | ## Extending These Records | |
905 | ||
906 | User records following this specifications are supposed to be extendable for | |
907 | various applications. In general, subsystems are free to introduce their own | |
908 | keys, as long as: | |
909 | ||
910 | * Care should be taken to place the keys in the right section, i.e. the most | |
911 | appropriate for the data field. | |
912 | ||
913 | * Care should be taken to avoid namespace clashes. Please prefix your fields | |
914 | with a short identifier of your project to avoid ambiguities and | |
915 | incompatibilities. | |
916 | ||
917 | * This specification is supposed to be a living specification. If you need | |
918 | additional fields, please consider submitting them upstream for inclusion in | |
919 | this specification. If they are reasonably universally useful, it would be | |
920 | best to list them here. | |
921 | ||
922 | ## Examples | |
923 | ||
924 | The shortest valid user record looks like this: | |
925 | ||
926 | ```json | |
927 | { | |
928 | "userName" : "u" | |
929 | } | |
930 | ``` | |
931 | ||
932 | A reasonable user record for a system user might look like this: | |
933 | ||
934 | ```json | |
935 | { | |
936 | "userName" : "httpd", | |
937 | "uid" : 473, | |
938 | "gid" : 473, | |
939 | "disposition" : "system", | |
940 | "locked" : true | |
941 | } | |
942 | ``` | |
943 | ||
944 | A fully featured user record associated with a home directory managed by | |
945 | `systemd-homed.service` might look like this: | |
946 | ||
947 | ```json | |
948 | { | |
949 | "autoLogin" : true, | |
950 | "binding" : { | |
951 | "15e19cf24e004b949ddaac60c74aa165" : { | |
952 | "fileSystemType" : "ext4", | |
953 | "fileSystemUuid" : "758e88c8-5851-4a2a-b88f-e7474279c111", | |
954 | "gid" : 60232, | |
955 | "homeDirectory" : "/home/grobie", | |
956 | "imagePath" : "/home/grobie.home", | |
957 | "luksCipher" : "aes", | |
958 | "luksCipherMode" : "xts-plain64", | |
959 | "luksUuid" : "e63581ba-79fb-4226-b9de-1888393f7573", | |
960 | "luksVolumeKeySize" : 32, | |
961 | "partitionUuid" : "41f9ce04-c827-4b74-a981-c669f93eb4dc", | |
962 | "storage" : "luks", | |
963 | "uid" : 60232 | |
964 | } | |
965 | }, | |
966 | "disposition" : "regular", | |
967 | "enforcePasswordPolicy" : false, | |
968 | "lastChangeUSec" : 1565950024279735, | |
969 | "memberOf" : [ | |
970 | "wheel" | |
971 | ], | |
972 | "privileged" : { | |
973 | "hashedPassword" : [ | |
974 | "$6$WHBKvAFFT9jKPA4k$OPY4D4TczKN/jOnJzy54DDuOOagCcvxxybrwMbe1SVdm.Bbr.zOmBdATp.QrwZmvqyr8/SafbbQu.QZ2rRvDs/" | |
975 | ] | |
976 | }, | |
977 | "signature" : [ | |
978 | { | |
979 | "data" : "LU/HeVrPZSzi3MJ0PVHwD5m/xf51XDYCrSpbDRNBdtF4fDVhrN0t2I2OqH/1yXiBidXlV0ptMuQVq8KVICdEDw==", | |
980 | "key" : "-----BEGIN PUBLIC KEY-----\nMCowBQYDK2VwAyEA/QT6kQWOAMhDJf56jBmszEQQpJHqDsGDMZOdiptBgRk=\n-----END PUBLIC KEY-----\n" | |
981 | } | |
982 | ], | |
983 | "userName" : "grobie", | |
984 | "status" : { | |
985 | "15e19cf24e004b949ddaac60c74aa165" : { | |
986 | "goodAuthenticationCounter" : 16, | |
987 | "lastGoodAuthenticationUSec" : 1566309343044322, | |
988 | "rateLimitBeginUSec" : 1566309342340723, | |
989 | "rateLimitCount" : 1, | |
990 | "state" : "inactive", | |
991 | "service" : "io.systemd.Home", | |
992 | "diskSize" : 161118667776, | |
993 | "diskCeiling" : 190371729408, | |
994 | "diskFloor" : 5242880, | |
995 | "signedLocally" : true | |
996 | } | |
997 | } | |
998 | } | |
999 | ``` | |
1000 | ||
1001 | When `systemd-homed.service` manages a home directory it will also include a | |
1002 | version of the user record in the home directory itself in the `~/.identity` | |
1003 | file. This version lacks the `binding` and `status` sections which are used for | |
1004 | local management of the user, but are not intended to be portable between | |
1005 | systems. It would hence look like this: | |
1006 | ||
1007 | ```json | |
1008 | { | |
1009 | "autoLogin" : true, | |
1010 | "disposition" : "regular", | |
1011 | "enforcePasswordPolicy" : false, | |
1012 | "lastChangeUSec" : 1565950024279735, | |
1013 | "memberOf" : [ | |
1014 | "wheel" | |
1015 | ], | |
1016 | "privileged" : { | |
1017 | "hashedPassword" : [ | |
1018 | "$6$WHBKvAFFT9jKPA4k$OPY4D4TczKN/jOnJzy54DDuOOagCcvxxybrwMbe1SVdm.Bbr.zOmBdATp.QrwZmvqyr8/SafbbQu.QZ2rRvDs/" | |
1019 | ] | |
1020 | }, | |
1021 | "signature" : [ | |
1022 | { | |
1023 | "data" : "LU/HeVrPZSzi3MJ0PVHwD5m/xf51XDYCrSpbDRNBdtF4fDVhrN0t2I2OqH/1yXiBidXlV0ptMuQVq8KVICdEDw==", | |
1024 | "key" : "-----BEGIN PUBLIC KEY-----\nMCowBQYDK2VwAyEA/QT6kQWOAMhDJf56jBmszEQQpJHqDsGDMZOdiptBgRk=\n-----END PUBLIC KEY-----\n" | |
1025 | } | |
1026 | ], | |
1027 | "userName" : "grobie", | |
1028 | } | |
1029 | ``` |