1 .\" Copyright (c) 1995 David Nugent <davidn@blaze.net.au>
2 .\" All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, is permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice immediately at the beginning of the file, without modification,
9 .\" this list of conditions, and the following disclaimer.
10 .\" 2. Redistributions in binary form must reproduce the above copyright
11 .\" notice, this list of conditions and the following disclaimer in the
12 .\" documentation and/or other materials provided with the distribution.
13 .\" 3. This work was done expressly for inclusion into FreeBSD. Other use
14 .\" is permitted provided this notation is included.
15 .\" 4. Absolutely no warranty of function or purpose is made by the author
17 .\" 5. Modifications may be freely made to this file providing the above
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20 .\" $FreeBSD: src/lib/libutil/login_cap.3,v 1.17.2.8 2002/12/29 16:35:36 schweikh Exp $
27 .Nm login_getcapbool ,
28 .Nm login_getcaplist ,
31 .Nm login_getcapsize ,
32 .Nm login_getcaptime ,
34 .Nm login_getclassbyname ,
35 .Nm login_getpwclass ,
37 .Nm login_getuserclass ,
39 .Nd "functions for accessing the login class capabilities database"
46 .Fn login_close "login_cap_t *lc"
48 .Fn login_getclassbyname "const char *nam" "const struct passwd *pwd"
50 .Fn login_getclass "const char *nam"
52 .Fn login_getpwclass "const struct passwd *pwd"
54 .Fn login_getuserclass "const struct passwd *pwd"
56 .Fn login_getcapstr "login_cap_t *lc" "const char *cap" "char *def" "char *error"
58 .Fn login_getcaplist "login_cap_t *lc" "const char *cap" "const char *chars"
60 .Fn login_getpath "login_cap_t *lc" "const char *cap" "char *error"
62 .Fn login_getcaptime "login_cap_t *lc" "const char *cap" "rlim_t def" "rlim_t error"
64 .Fn login_getcapnum "login_cap_t *lc" "const char *cap" "rlim_t def" "rlim_t error"
66 .Fn login_getcapsize "login_cap_t *lc" "const char *cap" "rlim_t def" "rlim_t error"
68 .Fn login_getcapbool "login_cap_t *lc" "const char *cap" "int def"
70 .Fn login_getstyle "login_cap_t *lc" "char *style" "const char *auth"
72 .Fn login_setcryptfmt "login_cap_t *lc" "const char *def" "const char *error"
74 These functions represent a programming interface to the login
75 classes database provided in
77 This database contains capabilities, attributes and default environment
78 and accounting settings for users and programs running as specific users,
79 as determined by the login class field within entries in
80 .Pa /etc/master.passwd .
86 separated fields, the first field in each record being one or more
87 identifiers for the record (which must be unique for the entire database),
88 each separated by a '|', and may optionally include a description as
90 Remaining fields in the record consist of keyword/data pairs.
91 Long lines may be continued with a backslash within empty entries,
92 with the second and subsequent lines optionally indented for readability.
93 This is similar to the format used in
95 except that keywords are not limited to two significant characters,
96 and are usually longer for improved readability.
97 As with termcap entries, multiple records can be linked together
98 (one record including another) using a field containing tc=<recordid>.
99 The result is that the entire record referenced by <recordid> replaces
100 the tc= field at the point at which it occurs.
103 for further details on the format and use of a capabilities database.
107 interface provides a convenient means of retrieving login class
108 records with all tc= references expanded.
109 A program will typically call one of
111 .Fn login_getpwclass ,
112 .Fn login_getuserclass
114 .Fn login_getclassbyname
115 according to its requirements.
116 Each of these functions returns a login capabilities structure,
118 which may subsequently be used to interrogate the database for
119 specific values using the rest of the API.
120 Once the login_cap_t is of no further use, the
122 function should be called to free all resources used.
124 The structure of login_cap_t is defined in login_cap.h, as:
125 .Bd -literal -offset indent
135 member contains a pointer to the name of the login class
137 This may not necessarily be the same as the one requested,
139 .Fn login_getclassbyname ,
140 indirectly via a user's login record using
141 .Fn login_getpwclass ,
145 .Fn login_getuserclass .
146 If the referenced user has no login class specified in
147 .Pa /etc/master.passwd ,
148 the class name is NULL or an empty string.
150 specified does not exist in the database, each of these
151 functions will search for a record with an id of "default",
152 with that name returned in the
155 In addition, if the referenced user has a UID of 0 (normally,
156 "root", although the user name is not considered) then
158 will search for a record with an id of "root" before it searches
159 for the record with the id of "default".
163 field is used internally by the library to contain the
164 expanded login capabilities record.
165 Programs with unusual requirements may wish to use this
168 style functions to access the record directly.
174 function to the authorisation style, according to the requirements
175 of the program handling a login itself.
179 functions return a login_cap_t object which is used to access
180 the matching or default record in the capabilities database.
182 accepts two arguments: the first one is the record identifier of the
183 record to be retrieved, the second is an optional directory name.
186 argument is NULL, an empty string, or a class that does not exist
187 in the supplemental or system login class database, then the system
189 record is returned instead.
192 parameter is NULL, then only the system login class database is
193 used, but when not NULL, the named directory is searched for
194 a login database file called ".login_conf", and capability records
195 contained within it may override the system defaults.
196 This scheme allows users to override some login settings from
197 those in the system login class database by creating class records
198 for their own private class with a record id of `me'.
201 it should be noted that some options cannot by overridden by
202 users for two reasons; many options, such as resource settings
203 and default process priorities, require root privileges
204 in order to take effect, and other fields in the user's file are
205 not be consulted at all during the early phases of login for
206 security or administrative reasons.
209 for more information on which settings a user is able to override.
210 Typically, these are limited purely to the user's default login
211 environment which might otherwise have been overridden in shell
212 startup scripts in any case.
215 merely provides a convenient way for a user to set up their preferred
216 login environment before the shell is invoked on login.
218 If the specified record is NULL, empty or does not exist, and the
219 system has no "default" record available to fall back to, there is a
220 memory allocation error or for some reason
222 is unable to access the login capabilities database, this function
226 .Fn login_getpwclass ,
229 .Fn login_getuserclass
230 retrieve the applicable login class record for the user's passwd
231 entry or class name by calling
232 .Fn login_getclassbyname .
233 On failure, NULL is returned.
234 The difference between these functions is that
235 .Fn login_getuserclass
236 includes the user's overriding
238 that exists in the user's home directory, and
242 restrict lookup only to the system login class database in
243 .Pa /etc/login.conf .
244 As explained earlier,
248 in that it allows the default class for user 'root' as "root"
249 if none has been specified in the password database.
250 Otherwise, if the passwd pointer is NULL, or the user record
251 has no login class, then the system "default" entry is retrieved.
253 Once a program no longer wishes to use a login_cap_t object,
255 may be called to free all resources used by the login class.
257 may be passed a NULL pointer with no harmful side-effects.
259 The remaining functions may be used to retrieve individual
261 Each function takes a login_cap_t object as its first parameter,
262 a capability tag as the second, and remaining parameters being
263 default and error values that are returned if the capability is
265 The type of the additional parameters passed and returned depend
268 of capability each deals with, be it a simple string, a list,
269 a time value, a file or memory size value, a path (consisting of
270 a colon-separated list of directories) or a boolean flag.
273 deals in specific tags and their type.
275 Note that with all functions in this group, you should not call
277 on any pointers returned.
278 Memory allocated during retrieval or processing of capability
279 tags is automatically reused by subsequent calls to functions
280 in this group, or deallocated on calling
282 .Bl -tag -width "login_getcaplist()"
283 .It Fn login_getcapstr
284 This function returns a simple string capability.
285 If the string is not found, then the value in
287 is returned as the default value, or if an error
288 occurs, the value in the
290 parameter is returned.
291 .It Fn login_getcaplist
292 This function returns the value corresponding to the named
293 capability tag as a list of values in a NULL terminated
295 Within the login class database, some tags are of type
297 which consist of one or more comma- or space separated
299 Usually, this function is not called directly from an
300 application, but is used indirectly via
303 This function returns a list of directories separated by colons
305 Capability tags for which this function is called consist of a list of
306 directories separated by spaces.
307 .It Fn login_getcaptime
308 This function returns a
310 associated with a particular capability tag with the value expressed
311 in seconds (the default), minutes, hours, days, weeks or (365 day)
312 years or any combination of these.
313 A suffix determines the units used: S for seconds, M for minutes,
314 H for hours, D for days, W for weeks and Y for 365 day years.
315 Case of the units suffix is ignored.
317 Time values are normally used for setting resource, accounting and
319 If supported by the operating system and compiler (which is true of
321 the value returned is a quad (long long), of type
323 A value "inf" or "infinity" may be used to express an infinite
324 value, in which case RLIM_INFINITY is returned.
325 .It Fn login_getcapnum
326 This function returns a numeric value for a tag, expressed either as
327 tag=<value> or the standard
330 The first format should be used in preference to the second, the
331 second format is provided for compatibility and consistency with the
333 database format where numeric types use the
335 as the delimiter for numeric values.
336 If in the first format, then the value given may be "inf" or
337 "infinity" which results in a return value of RLIM_INFINITY.
338 If the given capability tag cannot be found, the
340 parameter is returned, and if an error occurs, the
342 parameter is returned.
343 .It Fn login_getcapsize
345 returns a value representing a size (typically, file or memory)
346 which may be expressed as bytes (the default), 512 byte blocks,
347 kilobytes, megabytes, gigabytes, and on systems that support the
350 The suffix used determines the units, and multiple values and
351 units may be used in combination (e.g. 1m500k = 1.5 megabytes).
352 A value with no suffix is interpreted as bytes, B as 512-byte
353 blocks, K as kilobytes, M as megabytes, G as gigabytes and T as
356 The error value is returned if there is a login capabilities database
357 error, if an invalid suffix is used, or if a numeric value cannot be
359 .It Fn login_getcapbool
360 This function returns a boolean value tied to a particular flag.
361 It returns 0 if the given capability tag is not present or is
362 negated by the presence of a "tag@" (See
364 for more information on boolean flags), and returns 1 if the tag
366 .It Fn login_getstyle
367 This function is used by the login authorisation system to determine
368 the style of login available in a particular case.
369 The function accepts three parameters, the login_cap entry itself and
370 two optional parameters, and authorisation type 'auth' and 'style', and
371 applies these to determine the authorisation style that best suites
375 If 'auth' is neither NULL nor an empty string, look for a tag of type
376 "auth-<auth>" in the capability record.
377 If not present, then look for the default tag "auth=".
379 If no valid authorisation list was found from the previous step, then
380 default to "passwd" as the authorisation list.
382 If 'style' is not NULL or empty, look for it in the list of authorisation
383 methods found from the pprevious step.
384 If 'style' is NULL or an empty string, then default to "passwd"
387 If 'style' is found in the chosen list of authorisation methods, then
388 return that, otherwise return NULL.
391 This scheme allows the administrator to determine the types of
392 authorisation methods accepted by the system, depending on the
393 means by which the access occurs.
394 For example, the administrator may require skey or kerberos as
395 the authentication method used for access to the system via the
396 network, and standard methods via direct dialup or console
397 logins, significantly reducing the risk of password discovery
398 by "snooping" network packets.
399 .It Fn login_setcryptfmt
401 .Fn login_setcryptfmt
402 function is used to set the
407 If no entry is found,
409 is taken to be used as the fallback.
411 .Xr crypt_set_format 3
412 on the specifier fails,
414 is returned to indicate this.