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GENFS_CAN_ACCESS(9)        Kernel Developer's Manual       GENFS_CAN_ACCESS(9)

NAME
     genfs_can_access - generate an access control decision using vnode
     parameters

SYNOPSIS
     #include <miscfs/genfs/genfs.h>

     int
     genfs_can_access(vnode_t *vp, kauth_cred_t cred, uid_t file_uid,
         gid_t file_gid, mode_t file_mode, struct acl *acl,
         accmode_t accmode);

DESCRIPTION
     This call implements the logic for the UNIX discretionary file security
     model common to many file systems in FreeBSD.  It accepts the vnode vp,
     requesting credential cred, permissions via owning UID file_uid, owning
     GID file_gid, file permissions file_mode, access ACL for the file acl,
     desired access mode accmode,

     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() 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 genfs_can_access() selects a component of the file
     permission bits based on comparing the passed credential, file owner, and
     file group.  If the credential's effective UID matches the file owner,
     then the owner component of the permission bits is selected.  If the UID
     does not match, then the credential's effective GID, followed by
     additional groups, are compared with the file group--if there is a match,
     then the group component of the permission bits is selected.  If neither
     the credential UID or GIDs match the passed file owner and group, then
     the other component of the permission bits is selected.

     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
     super-user privilege, if available for the credential, will also be
     considered.

RETURN VALUES
     genfs_can_access() will return 0 on success, or a non-zero error value on
     failure.

ERRORS
     [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 resource.

SEE ALSO
     genfs(9), genfs_can_access_acl_nfs4(9), genfs_can_access_acl_posix1e(9),
     vnode(9), VOP_ACCESS(9)

AUTHORS
     This manual page and the current implementation of vaccess() were written
     by Robert Watson.

NetBSD 10.99                   January 17, 2022                   NetBSD 10.99