shadow
1. shadow.3.man
Manpage of SHADOW
SHADOW
Section: Library Calls (3)Updated: 02/16/2011
Index Return to Main Contents
NAME
shadow, getspnam - encrypted password file routinesSYNTAX
#include <shadow.h>
struct spwd *getspent();
struct spwd *getspnam(char *name);
void setspent();
void endspent();
struct spwd *fgetspent(FILE *fp);
struct spwd *sgetspent(char *cp);
int putspent(struct spwd *p, FILE *fp);
int lckpwdf();
DESCRIPTION
shadow manipulates the contents of the shadow password file, /etc/shadow. The structure in the #include file is:
-
struct spwd { char *sp_namp; /* user login name */ char *sp_pwdp; /* encrypted password */ long int sp_lstchg; /* last password change */ long int sp_min; /* days until change allowed. */ long int sp_max; /* days before change required */ long int sp_warn; /* days warning for expiration */ long int sp_inact; /* days before account inactive */ long int sp_expire; /* date when account expires */ unsigned long int sp_flag; /* reserved for future use */ }
The meanings of each field are:
- * sp_namp - pointer to null-terminated user name
- * sp_pwdp - pointer to null-terminated password
- * sp_lstchg - days since Jan 1, 1970 password was last changed
- * sp_min - days before which password may not be changed
- * sp_max - days after which password must be changed
- * sp_warn - days before password is to expire that user is warned of pending password expiration
- * sp_inact - days after password expires that account is considered inactive and disabled
- * sp_expire - days since Jan 1, 1970 when account will be disabled
- * sp_flag - reserved for future use
DESCRIPTION
getspent, getspname, fgetspent, and sgetspent each return a pointer to a struct spwd. getspent returns the next entry from the file, and fgetspent returns the next entry from the given stream, which is assumed to be a file of the proper format. sgetspent returns a pointer to a struct spwd using the provided string as input. getspnam searches from the current position in the file for an entry matching name.
setspent and endspent may be used to begin and end, respectively, access to the shadow password file.
The lckpwdf and ulckpwdf routines should be used to insure exclusive access to the /etc/shadow file. lckpwdf attempts to acquire a lock using pw_lock for up to 15 seconds. It continues by attempting to acquire a second lock using spw_lock for the remainder of the initial 15 seconds. Should either attempt fail after a total of 15 seconds, lckpwdf returns -1. When both locks are acquired 0 is returned.
DIAGNOSTICS
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.
CAVEATS
These routines may only be used by the superuser as access to the shadow password file is restricted.
FILES
/etc/shadow
- Secure user account information.
SEE ALSO
Index
This document was created by man2html using the manual pages.
Time: 17:07:51 GMT, January 19, 2012
2. shadow.5.man
Manpage of SHADOW
SHADOW
Section: File Formats and Conversions (5)Updated: 02/16/2011
Index Return to Main Contents
NAME
shadow - shadowed password fileDESCRIPTION
shadow is a file which contains the password information for the system's accounts and optional aging information.
This file must not be readable by regular users if password security is to be maintained.
Each line of this file contains 9 fields, separated by colons (lq:rq), in the following order:
login name
- It must be a valid account name, which exist on the system.
encrypted password
-
Refer to
crypt(3)
for details on how this string is interpreted.
If the password field contains some string that is not a valid result of crypt(3), for instance ! or *, the user will not be able to use a unix password to log in (but the user may log in the system by other means).
This field may be empty, in which case no passwords are required to authenticate as the specified login name. However, some applications which read the /etc/shadow file may decide not to permit any access at all if the password field is empty.
A password field which starts with a exclamation mark means that the password is locked. The remaining characters on the line represent the password field before the password was locked.
date of last password change
-
The date of the last password change, expressed as the number of days since Jan 1, 1970.
The value 0 has a special meaning, which is that the user should change her pasword the next time she will log in the system.
An empty field means that password aging features are disabled.
minimum password age
-
The minimum password age is the number of days the user will have to wait before she will be allowed to change her password again.
An empty field and value 0 mean that there are no minimum password age.
maximum password age
-
The maximum password age is the number of days after which the user will have to change her password.
After this number of days is elapsed, the password may still be valid. The user should be asked to change her password the next time she will log in.
An empty field means that there are no maximum password age, no password warning period, and no password inactivity period (see below).
If the maximum password age is lower than the minimum password age, the user cannot change her password.
password warning period
-
The number of days before a password is going to expire (see the maximum password age above) during which the user should be warned.
An empty field and value 0 mean that there are no password warning period.
password inactivity period
-
The number of days after a password has expired (see the maximum password age above) during which the password should still be accepted (and the user should update her password during the next login).
After expiration of the password and this expiration period is elapsed, no login is possible using the current user's password. The user should contact her administrator.
An empty field means that there are no enforcement of an inactivity period.
account expiration date
-
The date of expiration of the account, expressed as the number of days since Jan 1, 1970.
Note that an account expiration differs from a password expiration. In case of an acount expiration, the user shall not be allowed to login. In case of a password expiration, the user is not allowed to login using her password.
An empty field means that the account will never expire.
The value 0 should not be used as it is interpreted as either an account with no expiration, or as an expiration on Jan 1, 1970.
reserved field
- This field is reserved for future use.
FILES
/etc/passwd
- User account information.
/etc/shadow
- Secure user account information.
/etc/shadow-
-
Backup file for /etc/shadow.
Note that this file is used by the tools of the shadow toolsuite, but not by all user and password management tools.
SEE ALSO
chage(1), login(1), passwd(1), passwd(5), pwck(8), pwconv(8), pwunconv(8), su(1), sulogin(8).
Index
This document was created by man2html using the manual pages.
Time: 17:07:51 GMT, January 19, 2012
