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LOGIN_CAP(3)           FreeBSD Library Functions Manual           LOGIN_CAP(3)

     login_close, login_getcapbool, login_getcaplist, login_getcapnum,
     login_getcapstr, login_getcapsize, login_getcaptime, login_getclass,
     login_getclassbyname, login_getpwclass, login_getstyle,
     login_getuserclass, login_setcryptfmt -- functions for accessing the
     login class capabilities database

     System Utilities Library (libutil, -lutil)

     #include <sys/types.h>
     #include <login_cap.h>

     login_close(login_cap_t *lc);

     login_cap_t *
     login_getclassbyname(const char *nam, const struct passwd *pwd);

     login_cap_t *
     login_getclass(const char *nam);

     login_cap_t *
     login_getpwclass(const struct passwd *pwd);

     login_cap_t *
     login_getuserclass(const struct passwd *pwd);

     char *
     login_getcapstr(login_cap_t *lc, const char *cap, char *def,
         char *error);

     char **
     login_getcaplist(login_cap_t *lc, const char *cap, const char *chars);

     char *
     login_getpath(login_cap_t *lc, const char *cap, char *error);

     login_getcaptime(login_cap_t *lc, const char *cap, rlim_t def,
         rlim_t error);

     login_getcapnum(login_cap_t *lc, const char *cap, rlim_t def,
         rlim_t error);

     login_getcapsize(login_cap_t *lc, const char *cap, rlim_t def,
         rlim_t error);

     login_getcapbool(login_cap_t *lc, const char *cap, int def);

     char *
     login_getstyle(login_cap_t *lc, char *style, const char *auth);

     const char *
     login_setcryptfmt(login_cap_t *lc, const char *def, const char *error);

     These functions represent a programming interface to the login classes
     database provided in login.conf(5).  This database contains capabilities,
     attributes and default environment and accounting settings for users and
     programs running as specific users, as determined by the login class
     field within entries in /etc/master.passwd.

     Entries in login.conf(5) consist of colon `:' separated fields, the first
     field in each record being one or more identifiers for the record (which
     must be unique for the entire database), each separated by a '|', and may
     optionally include a description as the last 'name'.  Remaining fields in
     the record consist of keyword/data pairs.  Long lines may be continued
     with a backslash within empty entries, with the second and subsequent
     lines optionally indented for readability.  This is similar to the format
     used in termcap(5), except that keywords are not limited to two signifi-
     cant characters, and are usually longer for improved readability.  As
     with termcap entries, multiple records can be linked together (one record
     including another) using a field containing tc=<recordid>.  The result is
     that the entire record referenced by <recordid> replaces the tc= field at
     the point at which it occurs.  See getcap(3) for further details on the
     format and use of a capabilities database.

     The login_cap interface provides a convenient means of retrieving login
     class records with all tc= references expanded.  A program will typically
     call one of login_getclass(), login_getpwclass(), login_getuserclass() or
     login_getclassbyname() according to its requirements.  Each of these
     functions returns a login capabilities structure, login_cap_t, which may
     subsequently be used to interrogate the database for specific values
     using the rest of the API.  Once the login_cap_t is of no further use,
     the login_close() function should be called to free all resources used.

     The structure of login_cap_t is defined in login_cap.h, as:

           typedef struct {
                   char *lc_class;
                   char *lc_cap;
                   char *lc_style;
           } login_cap_t;

     The lc_class member contains a pointer to the name of the login class
     retrieved.  This may not necessarily be the same as the one requested,
     either directly via login_getclassbyname(), indirectly via a user's login
     record using login_getpwclass(), by class name using login_getclass(), or
     login_getuserclass().  If the referenced user has no login class speci-
     fied in /etc/master.passwd, the class name is NULL or an empty string.
     If the class specified does not exist in the database, each of these
     functions will search for a record with an id of "default", with that
     name returned in the lc_class field.  In addition, if the referenced user
     has a UID of 0 (normally, "root", although the user name is not consid-
     ered) then login_getpwclass() will search for a record with an id of
     "root" before it searches for the record with the id of "default".

     The lc_cap field is used internally by the library to contain the
     expanded login capabilities record.  Programs with unusual requirements
     may wish to use this with the lower-level getcap() style functions to
     access the record directly.

     The lc_style field is set by the login_getstyle() function to the autho-
     risation style, according to the requirements of the program handling a
     login itself.

     As noted above, the get*class() functions return a login_cap_t object
     which is used to access the matching or default record in the capabili-
     ties database.  getclassbyname() accepts two arguments: the first one is
     the record identifier of the record to be retrieved, the second is an
     optional directory name.  If the first name argument is NULL, an empty
     string, or a class that does not exist in the supplemental or system
     login class database, then the system default record is returned instead.
     If the second dir parameter is NULL, then only the system login class
     database is used, but when not NULL, the named directory is searched for
     a login database file called ".login_conf", and capability records con-
     tained within it may override the system defaults.  This scheme allows
     users to override some login settings from those in the system login
     class database by creating class records for their own private class with
     a record id of `me'.  In the context of a login, it should be noted that
     some options cannot by overridden by users for two reasons; many options,
     such as resource settings and default process priorities, require root
     privileges in order to take effect, and other fields in the user's file
     are not be consulted at all during the early phases of login for security
     or administrative reasons.  See login.conf(5) for more information on
     which settings a user is able to override.  Typically, these are limited
     purely to the user's default login environment which might otherwise have
     been overridden in shell startup scripts in any case.  The user's
     .login_conf merely provides a convenient way for a user to set up their
     preferred login environment before the shell is invoked on login.

     If the specified record is NULL, empty or does not exist, and the system
     has no "default" record available to fall back to, there is a memory
     allocation error or for some reason cgetent(3) is unable to access the
     login capabilities database, this function returns NULL.

     The functions login_getpwclass(), login_getclass() and
     login_getuserclass() retrieve the applicable login class record for the
     user's passwd entry or class name by calling login_getclassbyname().  On
     failure, NULL is returned.  The difference between these functions is
     that login_getuserclass() includes the user's overriding .login_conf that
     exists in the user's home directory, and login_getpwclass() and
     login_getclass() restrict lookup only to the system login class database
     in /etc/login.conf.  As explained earlier, login_getpwclass() only dif-
     fers from login_getclass() in that it allows the default class for user
     'root' as "root" if none has been specified in the password database.
     Otherwise, if the passwd pointer is NULL, or the user record has no login
     class, then the system "default" entry is retrieved.

     Once a program no longer wishes to use a login_cap_t object,
     login_close() may be called to free all resources used by the login
     class.  login_close() may be passed a NULL pointer with no harmful side-

     The remaining functions may be used to retrieve individual capability
     records.  Each function takes a login_cap_t object as its first parame-
     ter, a capability tag as the second, and remaining parameters being
     default and error values that are returned if the capability is not
     found.  The type of the additional parameters passed and returned depend
     on the type of capability each deals with, be it a simple string, a list,
     a time value, a file or memory size value, a path (consisting of a colon-
     separated list of directories) or a boolean flag.  The manpage for
     login.conf(5) deals in specific tags and their type.

     Note that with all functions in this group, you should not call free(3)
     on any pointers returned.  Memory allocated during retrieval or process-
     ing of capability tags is automatically reused by subsequent calls to
     functions in this group, or deallocated on calling login_close().

     login_getcapstr()   This function returns a simple string capability.  If
                         the string is not found, then the value in def is
                         returned as the default value, or if an error occurs,
                         the value in the error parameter is returned.

     login_getcaplist()  This function returns the value corresponding to the
                         named capability tag as a list of values in a NULL
                         terminated array.  Within the login class database,
                         some tags are of type list, which consist of one or
                         more comma- or space separated values.  Usually, this
                         function is not called directly from an application,
                         but is used indirectly via login_getstyle().

     login_getpath()     This function returns a list of directories separated
                         by colons `&:'.  Capability tags for which this func-
                         tion is called consist of a list of directories sepa-
                         rated by spaces.

     login_getcaptime()  This function returns a time value associated with a
                         particular capability tag with the value expressed in
                         seconds (the default), minutes, hours, days, weeks or
                         (365 day) years or any combination of these.  A suf-
                         fix determines the units used: S for seconds, M for
                         minutes, H for hours, D for days, W for weeks and Y
                         for 365 day years.  Case of the units suffix is

                         Time values are normally used for setting resource,
                         accounting and session limits.  If supported by the
                         operating system and compiler (which is true of
                         FreeBSD), the value returned is a quad (long long),
                         of type rlim_t.  A value "inf" or "infinity" may be
                         used to express an infinite value, in which case
                         RLIM_INFINITY is returned.

     login_getcapnum()   This function returns a numeric value for a tag,
                         expressed either as tag=<value> or the standard
                         cgetnum() format tag#<value>.  The first format
                         should be used in preference to the second, the sec-
                         ond format is provided for compatibility and consis-
                         tency with the getcap(3) database format where
                         numeric types use the `#' as the delimiter for
                         numeric values.  If in the first format, then the
                         value given may be "inf" or "infinity" which results
                         in a return value of RLIM_INFINITY.  If the given
                         capability tag cannot be found, the def parameter is
                         returned, and if an error occurs, the error parameter
                         is returned.

     login_getcapsize()  login_getcapsize() returns a value representing a
                         size (typically, file or memory) which may be
                         expressed as bytes (the default), 512 byte blocks,
                         kilobytes, megabytes, gigabytes, and on systems that
                         support the long long type, terabytes.  The suffix
                         used determines the units, and multiple values and
                         units may be used in combination (e.g. 1m500k = 1.5
                         megabytes).  A value with no suffix is interpreted as
                         bytes,  B as 512-byte blocks, K as kilobytes, M as
                         megabytes, G as gigabytes and T as terabytes.  Case
                         is ignored.  The error value is returned if there is
                         a login capabilities database error, if an invalid
                         suffix is used, or if a numeric value cannot be

     login_getcapbool()  This function returns a boolean value tied to a par-
                         ticular flag.  It returns 0 if the given capability
                         tag is not present or is negated by the presence of a
                         "tag@" (See getcap(3) for more information on boolean
                         flags), and returns 1 if the tag is found.

     login_getstyle()    This function is used by the login authorisation sys-
                         tem to determine the style of login available in a
                         particular case.  The function accepts three parame-
                         ters, the login_cap entry itself and two optional
                         parameters, and authorisation type 'auth' and
                         'style', and applies these to determine the authori-
                         sation style that best suites these rules.

                         +o   If 'auth' is neither NULL nor an empty string,
                             look for a tag of type "auth-<auth>" in the capa-
                             bility record.  If not present, then look for the
                             default tag "auth=".

                         +o   If no valid authorisation list was found from the
                             previous step, then default to "passwd" as the
                             authorisation list.

                         +o   If 'style' is not NULL or empty, look for it in
                             the list of authorisation methods found from the
                             pprevious step.  If 'style' is NULL or an empty
                             string, then default to "passwd" authorisation.

                         +o   If 'style' is found in the chosen list of autho-
                             risation methods, then return that, otherwise
                             return NULL.

                         This scheme allows the administrator to determine the
                         types of authorisation methods accepted by the sys-
                         tem, depending on the means by which the access
                         occurs.  For example, the administrator may require
                         skey or kerberos as the authentication method used
                         for access to the system via the network, and stan-
                         dard methods via direct dialup or console logins,
                         significantly reducing the risk of password discovery
                         by "snooping" network packets.

                         The login_setcryptfmt() function is used to set the
                         crypt(3) format using the `passwd_format' configura-
                         tion entry.  If no entry is found, def is taken to be
                         used as the fallback.  If calling crypt_set_format(3)
                         on the specifier fails, error is returned to indicate

     crypt(3), getcap(3), login_class(3), login.conf(5), termcap(5)

FreeBSD 4.10                   December 27, 1996                  FreeBSD 4.10


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