Name
getspnam, getspnam_r, getspent, getspent_r, setspent, endspent, fgetspent, fgetspent_r, sgetspent, sgetspent_r, putspent, lckpwdf, ulckpwdf — get shadow password file entry
Synopsis
/* General shadow password file API */ #include <shadow.h>
struct spwd
*getspnam( |
const char *name); |
struct spwd
*getspent( |
void); |
void
setspent( |
void); |
void
endspent( |
void); |
struct spwd
*fgetspent( |
FILE *stream); |
struct spwd
*sgetspent( |
const char *s); |
int
putspent( |
const struct spwd *p, |
FILE *stream); |
int
lckpwdf( |
void); |
int
ulckpwdf( |
void); |
/* GNU extension */ #include <shadow.h>
int
getspent_r( |
struct spwd *spbuf, |
| char *buf, | |
| size_t buflen, | |
struct spwd **spbufp); |
int
getspnam_r( |
const char *name, |
| struct spwd *spbuf, | |
| char *buf, | |
| size_t buflen, | |
struct spwd **spbufp); |
int
fgetspent_r( |
FILE *stream, |
| struct spwd *spbuf, | |
| char *buf, | |
| size_t buflen, | |
struct spwd **spbufp); |
int
sgetspent_r( |
const char *s, |
| struct spwd *spbuf, | |
| char *buf, | |
| size_t buflen, | |
struct spwd **spbufp); |
![[Note]](../stylesheet/note.png) |
Note | ||||
|---|---|---|---|---|---|
|
DESCRIPTION
Long ago it was considered safe to have encrypted
passwords openly visible in the password file. When computers
got faster and people got more security-conscious, this was
no longer acceptable. Julianne Frances Haugh implemented the
shadow password suite that keeps the encrypted passwords in
the shadow password database (e.g., the local shadow password
file /etc/shadow, NIS, and
LDAP), readable only by root.
The functions described below resemble those for the traditional password database (e.g., see getpwnam(3) and getpwent(3)).
The getspnam() function
returns a pointer to a structure containing the broken-out
fields of the record in the shadow password database that
matches the username name.
The getspent() function
returns a pointer to the next entry in the shadow password
database. The position in the input stream is initialized by
setspent(). When done reading,
the program may call endspent()
so that resources can be deallocated.
The fgetspent() function is
similar to getspent() but uses
the supplied stream instead of the one implicitly opened by
setspent().
The sgetspent() function
parses the supplied string s into a struct spwd.
The putspent() function
writes the contents of the supplied struct spwd *p as a text line in the shadow
password file format to stream. String entries with
value NULL and numerical entries with value −1 are
written as an empty string.
The lckpwdf() function is
intended to protect against multiple simultaneous accesses of
the shadow password database. It tries to acquire a lock, and
returns 0 on success, or −1 on failure (lock not
obtained within 15 seconds). The ulckpwdf() function releases the lock
again. Note that there is no protection against direct access
of the shadow password file. Only programs that use
lckpwdf() will notice the
lock.
These were the functions that formed the original shadow API. They are widely available.
Reentrant versions
Analogous to the reentrant functions for the password
database, glibc also has reentrant functions for the shadow
password database. The getspnam_r() function is like
getspnam() but stores the
retrieved shadow password structure in the space pointed to
by spbuf. This
shadow password structure contains pointers to strings, and
these strings are stored in the buffer buf of size buflen. A pointer to the
result (in case of success) or NULL (in case no entry was
found or an error occurred) is stored in *spbufp.
The functions getspent_r(), fgetspent_r(), and sgetspent_r() are similarly analogous to
their nonreentrant counterparts.
Some non-glibc systems also have functions with these names, often with different prototypes.
Structure
The shadow password structure is defined in <shadow.h>
as follows:
struct spwd { char * sp_namp;char * sp_pwdp;long sp_lstchg;
(measured in days since
1970-01-01 00:00:00 +0000 (UTC)) */long sp_min;long sp_max;long sp_warn;
to warn user to change it */long sp_inact;
until account is disabled */long sp_expire;
(measured in days since
1970-01-01 00:00:00 +0000 (UTC)) */unsigned long sp_flag;};
RETURN VALUE
The functions that return a pointer return NULL if no more
entries are available or if an error occurs during
processing. The functions which have int as the return value return 0 for success
and −1 for failure, with errno set to indicate the cause of the
error.
For the nonreentrant functions, the return value may point to static area, and may be overwritten by subsequent calls to these functions.
The reentrant functions return zero on success. In case of error, an error number is returned.
ERRORS
- EACCES
-
The caller does not have permission to access the shadow password file.
- ERANGE
-
Supplied buffer is too small.
FILES
/etc/shadow-
local shadow password database file
/etc/.pwd.lock-
lock file
The include file <paths.h>
defines the constant _PATH_SHADOW to the pathname of the shadow
password file.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
getspnam() |
Thread safety | MT-Unsafe race:getspnam locale |
getspent() |
Thread safety |
MT-Unsafe race:getspent race:spentbuf locale |
setspent(),endspent(),
getspent_r()
|
Thread safety | MT-Unsafe race:getspent locale |
fgetspent() |
Thread safety | MT-Unsafe race:fgetspent |
sgetspent() |
Thread safety | MT-Unsafe race:sgetspent |
putspent(),getspnam_r(),
sgetspent_r()
|
Thread safety | MT-Safe locale |
lckpwdf(),ulckpwdf(),
fgetspent_r()
|
Thread safety | MT-Safe |
In the above table, getspent
in race:getspent
signifies that if any of the functions setspent(3), getspent(3), getspent_r(3), or endspent(3) are used in
parallel in different threads of a program, then data races
could occur.
CONFORMING TO
The shadow password database and its associated API are not specified in POSIX.1. However, many other systems provide a similar API.
COLOPHON
This page is part of release 4.07 of the Linux man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
|
Copyright (c) 2003 Andries Brouwer (aebcwi.nl) and Walter Harms (walter.harmsinformatik.uni-oldenburg.de) %%%LICENSE_START(GPL_NOVERSION_ONELINE) Distributed under GPL %%%LICENSE_END |