Originální popis anglicky:
getspnam, getspnam_r, getspent, getspent_r, setspent, endspent, fgetspent,
fgetspent_r, sgetspent, sgetspent_r, putspent, lckpwdf, ulckpwdf - get shadow
password file entry
Návod, kniha: Linux Programmer's Manual
/* 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 *fp);
struct spwd *sgetspent(const char *s);
int putspent(struct spwd *p, FILE *fp);
int lckpwdf(void);
int ulckpwdf(void);
/* GNU extension */
#define _SVID_SOURCE /* or _BSD_SOURCE */
#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 *fp, 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);
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
/etc/shadow, readable only by root.
The access routines described below resemble those for
/etc/passwd. This
shadow password setup has been superseded by PAM (pluggable authentication
modules), and the file
/etc/nsswitch.conf now describes the sources to
be used.
The
getspnam() function returns a pointer to a structure containing the
broken out fields of a line from
/etc/shadow for the entry that matches
the user name
name.
The
getspent() function returns a pointer to the next entry in the shadow
password file. 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 the stream
fp. 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 access of
the shadow password database. It tries to acquire a lock, and returns 0 on
success, -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 routines that formed the original shadow API. They are widely
available.
Analogous to the "reentrant" routines for the password file, glibc
also has reentrant versions here. The
getspnam_r() function is like
getspnam() but stores the retrieved shadow passwd structure in the
space pointed to by
spbuf. This shadow passwd 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 completely analogous.
Some non-glibc systems also have functions with these names, often with
different prototypes.
The shadow passwd structure is defined in
<shadow.h> as follows:
struct spwd {
char *sp_namp; /* Login name */
char *sp_pwdp; /* Encrypted password */
long sp_lstchg; /* Date of last change */
long sp_min; /* Min #days between changes */
long sp_max; /* Max #days between changes */
long sp_warn; /* #days before pwd expires
to warn user to change it */
long sp_inact; /* #days after pwd expires
until account is disabled */
long sp_expire; /* #days since 1970-01-01
until account is disabled */
unsigned long sp_flag; /* Reserved */
};
Routines return NULL if no more entries are available or if an error occurs
during processing. Routines which have
int as the return value return 0
for success and -1 for failure.
For the non-reentrant 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 value
is returned.
- ERANGE
- Supplied buffer is too small.
- /etc/shadow
- 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.
getgrnam(3),
getpwnam(3),
getpwnam_r(3),
shadow(5)
