vaccess_acl_posix1e -- generate a POSIX.1e ACL access control decision
using vnode parameters
vaccess_acl_posix1e(enum vtype type, uid_t file_uid, gid_t file_gid,
struct acl *acl, mode_t acc_mode, struct ucred *cred, int *privused);
This call implements the logic for the UNIX discretionary file security
model with POSIX.1e ACL extensions. It accepts the vnodes type type,
owning UID file_uid, owning GID file_gid, access ACL for the file acl,
desired access mode acc_mode, requesting credential cred, and an optional
call-by-reference int pointer returning whether or not privilege was
required for successful evaluation of the call; the privused pointer may
be set to NULL by the caller in order not to be informed of privilege
information, or it may point to an integer that will be set to 1 if privilege
is used, and 0 otherwise.
This call is intended to support implementations of VOP_ACCESS(9), which
will use their own access methods to retrieve the vnode properties, and
then invoke vaccess_acl_posix1e() in order to perform the actual check.
Implementations of VOP_ACCESS(9) may choose to implement additional security
mechanisms whose results will be composed with the return value.
The algorithm used by vaccess_acl_posix1e() is based on the POSIX.1e ACL
evaluation algorithm. The algorithm selects a matching entry from the
access ACL, which may then be composed with an available ACL mask entry,
providing UNIX security compatibility.
Once appropriate protections are selected for the current credential, the
requested access mode, in combination with the vnode type, will be compared
with the discretionary rights available for the credential. If the
rights granted by discretionary protections are insufficient, then superuser
privilege, if available for the credential, will also be considered.
vaccess_acl_posix1e() will return 0 on success, or a non-zero error value
[EACCES] Permission denied. An attempt was made to access a
file in a way forbidden by its file access permissions.
[EPERM] Operation not permitted. An attempt was made to perform
an operation limited to processes with appropriate
privileges or to the owner of a file or other
vaccess(9), vnode(9), VOP_ACCESS(9)
This man page and the current implementation of vaccess_acl_posix1e()
were written by Robert Watson.
This man page should include a full description of the POSIX.1e ACL evaluation
algorithm, or cross reference another page that does.
FreeBSD 5.2.1 August 22, 2001 FreeBSD 5.2.1 [ Back ]