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
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10 .\" 2. Redistributions in binary form must reproduce the above copyright
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12 .\" documentation and/or other materials provided with the distribution.
13 .\" 3. This work was done expressly for inclusion into FreeBSD. Other use
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15 .\" 4. Absolutely no warranty of function or purpose is made by the author
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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 $
21 .\" $DragonFly: src/lib/libutil/login_cap.3,v 1.3 2004/03/11 12:28:53 hmp Exp $
28 .Nm login_getcapbool ,
29 .Nm login_getcaplist ,
32 .Nm login_getcapsize ,
33 .Nm login_getcaptime ,
35 .Nm login_getclassbyname ,
36 .Nm login_getpwclass ,
38 .Nm login_getuserclass ,
40 .Nd "functions for accessing the login class capabilities database"
47 .Fn login_close "login_cap_t *lc"
49 .Fn login_getclassbyname "const char *nam" "const struct passwd *pwd"
51 .Fn login_getclass "const char *nam"
53 .Fn login_getpwclass "const struct passwd *pwd"
55 .Fn login_getuserclass "const struct passwd *pwd"
57 .Fn login_getcapstr "login_cap_t *lc" "const char *cap" "char *def" "char *error"
59 .Fn login_getcaplist "login_cap_t *lc" "const char *cap" "const char *chars"
61 .Fn login_getpath "login_cap_t *lc" "const char *cap" "char *error"
63 .Fn login_getcaptime "login_cap_t *lc" "const char *cap" "rlim_t def" "rlim_t error"
65 .Fn login_getcapnum "login_cap_t *lc" "const char *cap" "rlim_t def" "rlim_t error"
67 .Fn login_getcapsize "login_cap_t *lc" "const char *cap" "rlim_t def" "rlim_t error"
69 .Fn login_getcapbool "login_cap_t *lc" "const char *cap" "int def"
71 .Fn login_getstyle "login_cap_t *lc" "char *style" "const char *auth"
73 .Fn login_setcryptfmt "login_cap_t *lc" "const char *def" "const char *error"
75 These functions represent a programming interface to the login
76 classes database provided in
78 This database contains capabilities, attributes and default environment
79 and accounting settings for users and programs running as specific users,
80 as determined by the login class field within entries in
81 .Pa /etc/master.passwd .
87 separated fields, the first field in each record being one or more
88 identifiers for the record (which must be unique for the entire database),
89 each separated by a '|', and may optionally include a description as
91 Remaining fields in the record consist of keyword/data pairs.
92 Long lines may be continued with a backslash within empty entries,
93 with the second and subsequent lines optionally indented for readability.
94 This is similar to the format used in
96 except that keywords are not limited to two significant characters,
97 and are usually longer for improved readability.
98 As with termcap entries, multiple records can be linked together
99 (one record including another) using a field containing tc=<recordid>.
100 The result is that the entire record referenced by <recordid> replaces
101 the tc= field at the point at which it occurs.
104 for further details on the format and use of a capabilities database.
108 interface provides a convenient means of retrieving login class
109 records with all tc= references expanded.
110 A program will typically call one of
112 .Fn login_getpwclass ,
113 .Fn login_getuserclass
115 .Fn login_getclassbyname
116 according to its requirements.
117 Each of these functions returns a login capabilities structure,
119 which may subsequently be used to interrogate the database for
120 specific values using the rest of the API.
121 Once the login_cap_t is of no further use, the
123 function should be called to free all resources used.
125 The structure of login_cap_t is defined in login_cap.h, as:
126 .Bd -literal -offset indent
136 member contains a pointer to the name of the login class
138 This may not necessarily be the same as the one requested,
140 .Fn login_getclassbyname ,
141 indirectly via a user's login record using
142 .Fn login_getpwclass ,
146 .Fn login_getuserclass .
147 If the referenced user has no login class specified in
148 .Pa /etc/master.passwd ,
149 the class name is NULL or an empty string.
151 specified does not exist in the database, each of these
152 functions will search for a record with an id of "default",
153 with that name returned in the
156 In addition, if the referenced user has a UID of 0 (normally,
157 "root", although the user name is not considered) then
159 will search for a record with an id of "root" before it searches
160 for the record with the id of "default".
164 field is used internally by the library to contain the
165 expanded login capabilities record.
166 Programs with unusual requirements may wish to use this
169 style functions to access the record directly.
175 function to the authorisation style, according to the requirements
176 of the program handling a login itself.
180 functions return a login_cap_t object which is used to access
181 the matching or default record in the capabilities database.
183 accepts two arguments: the first one is the record identifier of the
184 record to be retrieved, the second is an optional directory name.
187 argument is NULL, an empty string, or a class that does not exist
188 in the supplemental or system login class database, then the system
190 record is returned instead.
193 parameter is NULL, then only the system login class database is
194 used, but when not NULL, the named directory is searched for
195 a login database file called ".login_conf", and capability records
196 contained within it may override the system defaults.
197 This scheme allows users to override some login settings from
198 those in the system login class database by creating class records
199 for their own private class with a record id of `me'.
202 it should be noted that some options cannot by overridden by
203 users for two reasons; many options, such as resource settings
204 and default process priorities, require root privileges
205 in order to take effect, and other fields in the user's file are
206 not be consulted at all during the early phases of login for
207 security or administrative reasons.
210 for more information on which settings a user is able to override.
211 Typically, these are limited purely to the user's default login
212 environment which might otherwise have been overridden in shell
213 startup scripts in any case.
216 merely provides a convenient way for a user to set up their preferred
217 login environment before the shell is invoked on login.
219 If the specified record is NULL, empty or does not exist, and the
220 system has no "default" record available to fall back to, there is a
221 memory allocation error or for some reason
223 is unable to access the login capabilities database, this function
227 .Fn login_getpwclass ,
230 .Fn login_getuserclass
231 retrieve the applicable login class record for the user's passwd
232 entry or class name by calling
233 .Fn login_getclassbyname .
234 On failure, NULL is returned.
235 The difference between these functions is that
236 .Fn login_getuserclass
237 includes the user's overriding
239 that exists in the user's home directory, and
243 restrict lookup only to the system login class database in
244 .Pa /etc/login.conf .
245 As explained earlier,
249 in that it allows the default class for user 'root' as "root"
250 if none has been specified in the password database.
251 Otherwise, if the passwd pointer is NULL, or the user record
252 has no login class, then the system "default" entry is retrieved.
254 Once a program no longer wishes to use a login_cap_t object,
256 may be called to free all resources used by the login class.
258 may be passed a NULL pointer with no harmful side-effects.
260 The remaining functions may be used to retrieve individual
262 Each function takes a login_cap_t object as its first parameter,
263 a capability tag as the second, and remaining parameters being
264 default and error values that are returned if the capability is
266 The type of the additional parameters passed and returned depend
269 of capability each deals with, be it a simple string, a list,
270 a time value, a file or memory size value, a path (consisting of
271 a colon-separated list of directories) or a boolean flag.
274 deals in specific tags and their type.
276 Note that with all functions in this group, you should not call
278 on any pointers returned.
279 Memory allocated during retrieval or processing of capability
280 tags is automatically reused by subsequent calls to functions
281 in this group, or deallocated on calling
283 .Bl -tag -width "login_getcaplist()"
284 .It Fn login_getcapstr
285 This function returns a simple string capability.
286 If the string is not found, then the value in
288 is returned as the default value, or if an error
289 occurs, the value in the
291 parameter is returned.
292 .It Fn login_getcaplist
293 This function returns the value corresponding to the named
294 capability tag as a list of values in a NULL terminated
296 Within the login class database, some tags are of type
298 which consist of one or more comma- or space separated
300 Usually, this function is not called directly from an
301 application, but is used indirectly via
304 This function returns a list of directories separated by colons
306 Capability tags for which this function is called consist of a list of
307 directories separated by spaces.
308 .It Fn login_getcaptime
309 This function returns a
311 associated with a particular capability tag with the value expressed
312 in seconds (the default), minutes, hours, days, weeks or (365 day)
313 years or any combination of these.
314 A suffix determines the units used: S for seconds, M for minutes,
315 H for hours, D for days, W for weeks and Y for 365 day years.
316 Case of the units suffix is ignored.
318 Time values are normally used for setting resource, accounting and
320 If supported by the operating system and compiler (which is true of
322 the value returned is a quad (long long), of type
324 A value "inf" or "infinity" may be used to express an infinite
325 value, in which case RLIM_INFINITY is returned.
326 .It Fn login_getcapnum
327 This function returns a numeric value for a tag, expressed either as
328 tag=<value> or the standard
331 The first format should be used in preference to the second, the
332 second format is provided for compatibility and consistency with the
334 database format where numeric types use the
336 as the delimiter for numeric values.
337 If in the first format, then the value given may be "inf" or
338 "infinity" which results in a return value of RLIM_INFINITY.
339 If the given capability tag cannot be found, the
341 parameter is returned, and if an error occurs, the
343 parameter is returned.
344 .It Fn login_getcapsize
346 returns a value representing a size (typically, file or memory)
347 which may be expressed as bytes (the default), 512 byte blocks,
348 kilobytes, megabytes, gigabytes, and on systems that support the
351 The suffix used determines the units, and multiple values and
352 units may be used in combination (e.g. 1m500k = 1.5 megabytes).
353 A value with no suffix is interpreted as bytes, B as 512-byte
354 blocks, K as kilobytes, M as megabytes, G as gigabytes and T as
357 The error value is returned if there is a login capabilities database
358 error, if an invalid suffix is used, or if a numeric value cannot be
360 .It Fn login_getcapbool
361 This function returns a boolean value tied to a particular flag.
362 It returns 0 if the given capability tag is not present or is
363 negated by the presence of a "tag@" (See
365 for more information on boolean flags), and returns 1 if the tag
367 .It Fn login_getstyle
368 This function is used by the login authorisation system to determine
369 the style of login available in a particular case.
370 The function accepts three parameters, the login_cap entry itself and
371 two optional parameters, and authorisation type 'auth' and 'style', and
372 applies these to determine the authorisation style that best suites
376 If 'auth' is neither NULL nor an empty string, look for a tag of type
377 "auth-<auth>" in the capability record.
378 If not present, then look for the default tag "auth=".
380 If no valid authorisation list was found from the previous step, then
381 default to "passwd" as the authorisation list.
383 If 'style' is not NULL or empty, look for it in the list of authorisation
384 methods found from the pprevious step.
385 If 'style' is NULL or an empty string, then default to "passwd"
388 If 'style' is found in the chosen list of authorisation methods, then
389 return that, otherwise return NULL.
392 This scheme allows the administrator to determine the types of
393 authorisation methods accepted by the system, depending on the
394 means by which the access occurs.
395 For example, the administrator may require skey or kerberos as
396 the authentication method used for access to the system via the
397 network, and standard methods via direct dialup or console
398 logins, significantly reducing the risk of password discovery
399 by "snooping" network packets.
400 .It Fn login_setcryptfmt
402 .Fn login_setcryptfmt
403 function is used to set the
408 If no entry is found,
410 is taken to be used as the fallback.
412 .Xr crypt_set_format 3
413 on the specifier fails,
415 is returned to indicate this.