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PUFFS_CRED(3)	      DragonFly Library Functions Manual	 PUFFS_CRED(3)

NAME
     puffs_cred -- puffs credential and access control routines

LIBRARY
     puffs Convenience Library (libpuffs, -lpuffs)

SYNOPSIS
     #include <puffs.h>

     int
     puffs_cred_getuid(const struct puffs_cred *pcr, uid_t *uid);

     int
     puffs_cred_getgid(const struct puffs_cred *pcr, gid_t *gid);

     int
     puffs_cred_getgroups(const struct puffs_cred *pcr, gid_t *gids,
	 short *ngids);

     bool
     puffs_cred_isuid(const struct puffs_cred *pcr, uid_t uid);

     bool
     puffs_cred_hasgroup(const struct puffs_cred *pcr, gid_t gid);

     bool
     puffs_cred_iskernel(const struct puffs_cred *pcr);

     bool
     puffs_cred_isfs(const struct puffs_cred *pcr);

     bool
     puffs_cred_isjuggernaut(const struct puffs_cred *pcr);

     int
     puffs_access(enum vtype type, mode_t file_mode, uid_t owner, gid_t group,
	 mode_t access_mode, const struct puffs_cred *pcr);

     int
     puffs_access_chown(uid_t owner, gid_t group, uid_t newowner,
	 gid_t newgroup, const struct puffs_cred *pcr);

     int
     puffs_access_chmod(uid_t owner, gid_t group, enum vtype type,
	 mode_t newmode, const struct puffs_cred *pcr);

     int
     puffs_access_times(uid_t owner, gid_t group, mode_t file_mode,
	 int va_utimes_null, const struct puffs_cred *pcr);

DESCRIPTION
     These functions can be used to check operation credentials and perform
     access control.  The structure struct puffs_cred can contain two types of
     credentials: ones belonging to users and ones belonging to the kernel.
     The latter is further divided into generic kernel credentials and file
     system credentials.  The general rule is that these should be treated as
     more powerful than superuser credentials, but the file system is free to
     treat them as it sees fit.

   Credentials
     The puffs_cred_get() family of functions fetch the uid or gid(s) from the
     given credential cookie.  They return 0 for success or -1 for an error
     and set errno.  An error happens when the credentials represent kernel or
     file system credentials and do not contain an uid or gid(s).

     For puffs_cred_getgroups(), the argument gids should point to an array
     with room for *ngids elements.

     The puffs_cred_is() family of functions return 1 if the truth value of
     the function for pcr is true and 0 if it is false.  The function
     puffs_cred_isjuggernaut() is true if pcr describes superuser, kernel or
     file system credentials.

   Access Control
     To help the programmers task of emulating normal kernel file system
     access control semantics, several helper functions are provided to check
     if access is allowed.  They return 0 if access should be permitted or an
     errno value to indicate that access should be denied with the returned
     value.

     puffs_access() is equivalent to the kernel vaccess() function.  The argu-
     ments specify current information of the file to be tested with the
     exception of access_mode, which is a combination of PUFFS_VREAD,
     PUFFS_VWRITE and PUFFS_VEXEC indicating the desired file access mode.

     The rest of the functions provide UFS semantics for operations.
     puffs_access_chown() checks if it is permissible to chown a file with the
     current uid and gid to the new uid and gid with the credentials of pcr.

     puffs_access_chmod() checks against permission to chmod a file of type
     type to the mode newmode.

     Finally, puffs_access_times() checks if it is allowable to update the
     timestamps of a file.  The argument va_utimes_null signals if the flags
     VA_UTIMES_NULL was set in va_vaflags of struct vattr.  If coming from a
     path where this information is unavailable, passing 0 as this argument
     restricts the permission of modification to the owner and superuser.
     Otherwise the function checks for write permissions to the node and
     returns success if the caller has write permissions.

SEE ALSO
     puffs(3), vnode(9)

DragonFly 5.5		       February 5, 2012 		 DragonFly 5.5