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.Dd December 23, 1999
.Os
.Dt ACL 9
.Sh NAME
.Nm acl
.Nd virtual file system access control lists
.Sh SYNOPSIS
.In sys/param.h
.In sys/vnode.h
.In sys/acl.h
.Pp
.Bd -literal
typedef int     acl_type_t;
typedef int     acl_tag_t;
typedef mode_t  acl_perm_t;
typedef mode_t  *acl_permset_t;

struct acl_entry {
        acl_tag_t       ae_tag;
        uid_t           ae_id;
        acl_perm_t      ae_perm;
};
typedef struct acl_entry        *acl_entry_t;

/* internal ACL structure */
struct acl {
        int                     acl_cnt;
        struct acl_entry        acl_entry[ACL_MAX_ENTRIES];
};

/* external ACL structure */
struct acl_t_struct {
        struct acl              ats_acl;
        int                     ats_cur_entry;
};
typedef struct acl_t_struct *acl_t;

/*
 * Possible valid values for ae_tag field.
 */
#define ACL_UNDEFINED_TAG       0x00000000
#define ACL_USER_OBJ            0x00000001
#define ACL_USER                0x00000002
#define ACL_GROUP_OBJ           0x00000004
#define ACL_GROUP               0x00000008
#define ACL_MASK                0x00000010
#define ACL_OTHER               0x00000020
#define ACL_OTHER_OBJ           ACL_OTHER

/*
 * Possible valid values for acl_type_t arguments.
 */
#define ACL_TYPE_ACCESS         0x00000000
#define ACL_TYPE_DEFAULT        0x00000001
#define ACL_TYPE_AFS            0x00000002
#define ACL_TYPE_CODA           0x00000003
#define ACL_TYPE_NTFS           0x00000004
#define ACL_TYPE_NWFS           0x00000005

/*
 * Possible flags in ae_perm field.
 */
#define ACL_EXECUTE             0x0001
#define ACL_WRITE               0x0002
#define ACL_READ                0x0004
#define ACL_PERM_NONE           0x0000
#define ACL_PERM_BITS           (ACL_EXECUTE | ACL_WRITE | ACL_READ)
#define ACL_POSIX1E_BITS        (ACL_EXECUTE | ACL_WRITE | ACL_READ)

/*
 * Possible entry_id values for acl_get_entry()
 */
#define ACL_FIRST_ENTRY         0
#define ACL_NEXT_ENTRY          1

/*
 * Undefined value in ae_id field
 */
#define ACL_UNDEFINED_ID        ((uid_t)-1)
.Ed
.Sh DESCRIPTION
Access control lists, or ACLs, allow fine-grained specification of rights
for vnodes representing files and directories.  However, as there are a
plethora of file systems with differing ACL semantics, the vnode interface
is aware only of the syntax of ACLs, relying on the underlying file system
to implement the details.  Depending on the underlying file system, each
file or directory may have zero or more ACLs associated with it, named using
the
.Fa type
field of the appropriate vnode ACL calls,
.Xr VOP_ACLCHECK 9 ,
.Xr VOP_GETACL 9 ,
and
.Xr VOP_SETACL 9 .
.Pp
Currently, each ACL is represented in-kernel by a fixed-size acl structure.
An ACL is constructed from a fixed size array of ACL entries, each of which
consists of a set of permissions, principal namespace, and principal
identifier.  Zero or more of these entries may be "defined", depending on
the value of the associated acl_cnt field.
.Sh SEE ALSO
.Xr VFS 9 ,
.Xr VOP_ACLCHECK 9 ,
.Xr VOP_GETACL 9 ,
.Xr VOP_SETACL 9
.Sh AUTHORS
This man page was written by
.An Robert Watson .