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 arguments 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)