KAUTH(9)

NAME
kauth - kernel authorization framework

SYNOPSIS
#include <sys/kauth.h>

DESCRIPTION
kauth, or kernel authorization, is the subsystem managing all authorization requests inside the kernel. It manages user credentials and rights, and can be used to implement a system-wide security policy. It allows external modules to plug-in the authorization process.

kauth introduces some new concepts, namely “scopes” and “listeners”, which will be detailed together with other useful information for kernel developers in this document.

  Types
Some kauth types include the following:

kauth_cred_t
    Representing credentials that can be associated with an object. Includes user- and group-ids (real, effective, and save) as well as group membership information.

kauth_scope_t
    Describes a scope.

kauth_listener_t
    Describes a listener.

  Terminology
kauth operates in various “scopes”, each scope holding a group of “listeners”.

Each listener works as a callback for when an authorization request within the scope is made. When such a request is made, all listeners on the scope are passed common information such as the credentials of the request context, an identifier for the requested operation, and possibly other information as well.

Every listener examines the passed information and returns its decision regarding the requested operation. It can either return:

KAUTH_RESULT_ALLOW
    The listener allows the operation.
KAUTH_RESULT_DENY
    The listener denies the operation.
KAUTH_RESULT_DEFER
    The listener defers the decision to other listeners.

For an operation to be allowed, at least one listener has to return KAUTH_RESULT_ALLOW while no other listener returned KAUTH_RESULT_DENY.

Scopes manage listeners that operate in the same aspect of the system.

  Kernel Programming Interface
kauth exports a KPI that allows developers both of NetBSD and third-party products to authorize requests, access and modify credentials, create and remove scopes and listeners, and perform other miscellaneous operations on credentials.

  Authorization Requests
kauth provides a single authorization request routine, which all authorization requests go through. This routine dispatches the request to the listeners of the appropriate scope, together with four optional user-data variables, and returns the augmented result.

It is declared as

int kauth_authorize_action(kauth_scope_t scope, kauth_cred_t cred, kauth_action_t op, void *arg0, void *arg1, void *arg2, void *arg3)

An authorization request can return one of two possible values:
0 (zero)
    indicates success; operation is allowed.
EPERM
    indicates failure; operation is denied. See errno(2).

Each scope has its own authorization wrapper, to make it easy to call from various places by eliminating the need to specify the scope and/or cast values. The authorization wrappers are detailed in each scope's section.

kauth_authorize_action() has several special cases, when it will always allow the request. These are for when the request is issued by the kernel itself (indicated by the credentials being either NOCRED or FSCRED), or when there was no definitive decision from any of the listeners (i.e., it was not explicitly allowed or denied) and no security model was loaded.

  Generic Scope
The generic scope, “org.netbsd.kauth.generic”, manages generic authorization requests in the kernel.

The authorization wrapper for this scope is declared as

int kauth_authorize_generic(kauth_cred_t cred, kauth_action_t op, void *arg0)

The following operations are available for this scope:

KAUTH_GENERIC_ISSUSER
    Checks whether the credentials belong to the super-user.

    Using this request is strongly discouraged and should only be done as a temporary place-holder, as it is breaking the separation between the interface for authorization requests from the back-end implementation.

  System Scope
The system scope, “org.netbsd.kauth.system”, manages authorization requests affecting the entire system.

The authorization wrapper for this scope is declared as

int kauth_authorize_system(kauth_cred_t cred, kauth_action_t op, enum kauth_system_req req, void *arg1, void *arg2, void *arg3)

The following requests are available for this scope:

KAUTH_SYSTEM_ACCOUNTING
    Check if enabling/disabling accounting allowed.

KAUTH_SYSTEM_CHROOT
    req can be any of the following:

    KAUTH_REQ_SYSTEM_CHROOT_CHROOT
        Check if calling chroot(2) is allowed.

    KAUTH_REQ_SYSTEM_CHROOT_FCHROOT
        Check if calling fchroot(2) is allowed.

KAUTH_SYSTEM_CPU
    Check CPU-manipulation access.

    req can be any of the following:

    KAUTH_REQ_SYSTEM_CPU_SETSTATE
        Set CPU state, including setting it online or offline.

KAUTH_SYSTEM_DEBUG
    This request concentrates several debugging-related operations.

KAUTH_SYSTEM_DEVMAPPER
    Check if operations on the device mapper dm(4) device are allowed.

KAUTH_SYSTEM_FILEHANDLE
    Check if file handle operations allowed.

KAUTH_SYSTEM_FS_EXTATTR
    Check if starting, stopping, enabling, or disabling extended attributes is allowed. arg1 is a struct mount * of the mount-point on which the operation is performed.

KAUTH_SYSTEM_FS_SNAPSHOT
    Check if setting up a file system snapshot is allowed. arg1 is a struct mount * of the mount-point of which the snapshot is taken, and arg2 is a struct vnode * of the vnode where the snapshot is expected to be.

KAUTH_SYSTEM_FS_QUOTA
    Check if file system quota operations are allowed.

    arg1 is a struct mount * describing the file system mount in question. req can be one of the following:

    KAUTH_REQ_SYSTEM_FS_QUOTA_GET
        Check if retrieving quota information is allowed.

        arg2 is a uid_t with the user-id of the user whose quota information is to be retrieved.

    KAUTH_REQ_SYSTEM_FS_QUOTA_ONOFF
        Check if turning quota on/off is allowed.

    KAUTH_REQ_SYSTEM_FS_QUOTA_MANAGE
        Check if managing the quota by setting the quota/quota use is allowed.

        arg2 is a uid_t with the user-id of the user whose quota/quota use is to be set.

    KAUTH_REQ_SYSTEM_FS_QUOTA_NOLIMIT
        Check if bypassing the quota (not enforcing it) is allowed.

KAUTH_SYSTEM_FS_RESERVEDSPACE
    Check if using the file system reserved space is allowed.

KAUTH_SYSTEM_LFS
    Check if LFS-related operations are allowed. req can be one of the following:

    KAUTH_REQ_SYSTEM_LFS_MARKV
        Check if calling lfs_markv(2) is allowed.

    KAUTH_REQ_SYSTEM_LFS_BMAPV
        Check if calling lfs_bmapv(2) is allowed.

    KAUTH_REQ_SYSTEM_LFS_SEGCLEAN
        Check if calling lfs_segclean(2) is allowed.

    KAUTH_REQ_SYSTEM_LFS_SEGWAIT
        Check if calling lfs_segwait(2) is allowed.

    KAUTH_REQ_SYSTEM_LFS_FCNTL
        Check if operations on LFS through fcntl(2) are allowed.

KAUTH_SYSTEM_MAP_VA_ZERO
    Check if changing the status of memory mapping of virtual address zero is allowed.

KAUTH_SYSTEM_MODULE
    Check if a module request is allowed.

    arg1 is the command.

KAUTH_SYSTEM_MKNOD
    Check if creating devices is allowed.

KAUTH_SYSTEM_MOUNT
    Check if mount-related operations are allowed.

    req can be any of the following:

    KAUTH_REQ_SYSTEM_MOUNT_DEVICE
        Check if mounting a device is allowed. arg1 is a vnode_t * of the device, arg2 is a struct mount * with the mount-point, and arg3 is a mode_t with the desired access mode.

    KAUTH_REQ_SYSTEM_MOUNT_GET
        Check if retrieving information about a mount is allowed. arg1 is a struct mount * with the mount structure in question, arg2 is a void * with file system specific data, if any.

    KAUTH_REQ_SYSTEM_MOUNT_NEW
        Check if mounting a new file system is allowed.

        arg1 is the struct vnode * on which the file system is to be mounted, arg2 is an int with the mount flags, and arg3 is a void * with file system specific data, if any.

    KAUTH_REQ_SYSTEM_MOUNT_UNMOUNT
        Checks if unmounting a file system is allowed.

        arg1 is a struct mount * with the mount in question.

    KAUTH_REQ_SYSTEM_MOUNT_UPDATE
        Checks if updating an existing mount is allowed.

        arg1 is the struct mount * of the existing mount, arg2 is an int with the new mount flags, and arg3 is a void * with file system specific data, if any.

    KAUTH_REQ_SYSTEM_MOUNT_UMAP
        Check if mounting the user and group id remapping file system. See mount_umap(8).

KAUTH_SYSTEM_MQUEUE
    Check if bypassing permissions on a message queue object are allowed. arg1 is a mqueue_t * describing the message queue.

KAUTH_SYSTEM_PSET
    Check processor-set manipulation.

    req can be any of the following:

    KAUTH_REQ_SYSTEM_PSET_ASSIGN
        Change processor-set processor assignment.

    KAUTH_REQ_SYSTEM_PSET_BIND
        Bind an LWP to a processor-set.

    KAUTH_REQ_SYSTEM_PSET_CREATE
        Create a processor-set.

    KAUTH_REQ_SYSTEM_PSET_DESTROY
        Destroy a processor-set.

KAUTH_SYSTEM_REBOOT
    Check if rebooting is allowed.

KAUTH_SYSTEM_SETIDCORE
    Check if changing coredump settings for set-id processes is allowed.

KAUTH_SYSTEM_SEMAPHORE
    Check if access to a kernel semaphore is allowed. arg1 is a ksem_t * describing the semaphore.

KAUTH_SYSTEM_SWAPCTL
    Check if privileged swapctl(2) requests are allowed.

KAUTH_SYSTEM_SYSCTL
    This requests operations related to sysctl(9). req indicates the specific request and can be one of the following:

    KAUTH_REQ_SYSTEM_SYSCTL_ADD
        Check if adding a sysctl(9) node is allowed.

    KAUTH_REQ_SYSTEM_SYSCTL_DELETE
        Check if deleting a sysctl(9) node is allowed.

    KAUTH_REQ_SYSTEM_SYSCTL_DESC
        Check if adding description to a sysctl(9) node is allowed.

    KAUTH_REQ_SYSTEM_SYSCTL_MODIFY
        Check if modifying a sysctl(9) node variable that doesn't have a custom sysctl helper function is allowed.

        This request might be deprecated in the future.

    KAUTH_REQ_SYSTEM_SYSCTL_PRVT
        Check if accessing private sysctl(9) nodes is allowed.

KAUTH_SYSTEM_SYSVIPC
    Check SysV IPC related operations. req indicates the specific request and can be one of the following:

    KAUTH_REQ_SYSTEM_SYSVIPC_BYPASS
        Check if bypassing a SysV IPC object's permissions is allowed. arg1 is a struct ipc_perm * with the object's permissions and arg2 is a mode_t indicating the requested access mode.

    KAUTH_REQ_SYSTEM_SYSVIPC_SHM_LOCK
        Check if shared memory locking is allowed.

    KAUTH_REQ_SYSTEM_SYSVIPC_SHM_UNLOCK
        Check if shared memory unlocking is allowed.

    KAUTH_REQ_SYSTEM_SYSVIPC_MSGQ_OVERSIZE
        Check if oversizing a message queue is allowed. arg1 is a msglen_t indicating the size of the message buffer, and arg2 is a msglen_t indicating the size of the message queue.

KAUTH_SYSTEM_TIME
    This request groups time-related operations. req can be any of the following:

    KAUTH_REQ_SYSTEM_TIME_ADJTIME
        Check if changing the time using adjtime(2) is allowed.

    KAUTH_REQ_SYSTEM_TIME_NTPADJTIME
        Check if setting the time using ntp_adjtime(2) is allowed.

    KAUTH_REQ_SYSTEM_TIME_SYSTEM
        Check if changing the time (usually via settimeofday(2)) is allowed.

        arg1 is a struct timespec * with the new time, arg2 is a struct timeval * with the delta from the current time, arg3 is a bool indicating whether the caller is a device context (e.g. /dev/clockctl) or not.

    KAUTH_REQ_SYSTEM_TIME_RTCOFFSET
        Check if changing the RTC offset is allowed.

    KAUTH_REQ_SYSTEM_TIME_TIMECOUNTERS
        Check if manipulating timecounters is allowed.

KAUTH_SYSTEM_VERIEXEC
    Check if operations on the veriexec(8) subsystem are allowed. req can be one of the following:

    KAUTH_REQ_SYSTEM_VERIEXEC_ACCESS
        Check if access to the veriexec(8) subsystem is allowed.

    KAUTH_REQ_SYSTEM_VERIEXEC_MODIFY
        Check if modifications to the state of veriexec(8) are allowed.

  Process Scope
The process scope, “org.netbsd.kauth.process”, manages authorization requests related to processes in the system.

The authorization wrapper for this scope is declared as

int kauth_authorize_process(kauth_cred_t cred, kauth_action_t op, struct proc *p, void *arg1, void *arg2, void *arg3)

The following operations are available for this scope:

KAUTH_PROCESS_KTRACE
    Checks whether an object with one set of credentials can ktrace(1) another process p, possibly with a different set of credentials.

    If arg1 is KAUTH_REQ_PROCESS_KTRACE_PERSISTENT, this checks if persistent tracing can be done. Persistent tracing maintains the trace across a set-user-id/set-group-id exec(3), and normally requires privileged credentials.

KAUTH_PROCESS_PROCFS
    Checks whether object with passed credentials can use procfs to access process p.

    arg1 is the struct pfsnode * for the target element in the target process, and arg2 is the access type, which can be either KAUTH_REQ_PROCESS_PROCFS_READ, KAUTH_REQ_PROCESS_PROCFS_RW, or KAUTH_REQ_PROCESS_PROCFS_WRITE, indicating control, read, read-write, or write access respectively.

KAUTH_PROCESS_PTRACE
    Checks whether object with passed credentials can use ptrace(2) to access process p.

    arg1 is the ptrace(2) command.

KAUTH_PROCESS_CANSEE
    Checks whether an object with one set of credentials can access information about another process, possibly with a different set of credentials.

    arg1 indicates the class of information being viewed, and can be either of KAUTH_REQ_PROCESS_CANSEE_ARGS, KAUTH_REQ_PROCESS_CANSEE_ENTRY, KAUTH_REQ_PROCESS_CANSEE_ENV, or KAUTH_REQ_PROCESS_CANSEE_OPENFILES.

KAUTH_PROCESS_SCHEDULER_GETAFFINITY
    Checks whether viewing the scheduler affinity is allowed.

KAUTH_PROCESS_SCHEDULER_SETAFFINITY
    Checks whether setting the scheduler affinity is allowed.

KAUTH_PROCESS_SCHEDULER_GETPARAM
    Checks whether viewing the scheduler policy and parameters is allowed.

KAUTH_PROCESS_SCHEDULER_SETPARAM
    Checks whether modifying the scheduler policy and parameters is allowed.

KAUTH_PROCESS_SIGNAL
    Checks whether an object with one set of credentials can post signals to another process.

    p is the process the signal is being posted to, and arg1 is the signal number.

KAUTH_PROCESS_CORENAME
    Controls access to process corename.

    arg1 can be KAUTH_REQ_PROCESS_CORENAME_GET or KAUTH_REQ_PROCESS_CORENAME_SET, indicating access to read or write the process' corename, respectively.

    When modifying the corename, arg2 holds the new corename to be used.

KAUTH_PROCESS_FORK
    Checks if the process can fork. arg1 is an int indicating how many processes exist on the system at the time of the check.

KAUTH_PROCESS_KEVENT_FILTER
    Checks whether setting a process kevent(2) filter is allowed.

KAUTH_PROCESS_NICE
    Checks whether the nice value of p can be changed to arg1.

KAUTH_PROCESS_RLIMIT
    Controls access to process resource limits.

    arg1 can be KAUTH_REQ_PROCESS_RLIMIT_GET or KAUTH_REQ_PROCESS_RLIMIT_SET, indicating access to read or write the process' resource limits, respectively, or KAUTH_REQ_PROCESS_RLIMIT_BYPASS to check if the limit enforcement can be bypassed.

    When modifying resource limits, arg2 is the new value to be used and arg3 indicates which resource limit is to be modified.

KAUTH_PROCESS_SETID
    Check if changing the user- or group-ids, groups, or login-name for p is allowed.

KAUTH_PROCESS_STOPFLAG
    Check if setting the stop flags for exec(3), exit(3), and fork(2) is allowed.

    arg1 indicates the flag, and can be either P_STOPEXEC, P_STOPEXIT, or P_STOPFORK respectively.

  Network Scope
The network scope, “org.netbsd.kauth.network”, manages networking-related authorization requests in the kernel.

The authorization wrapper for this scope is declared as

int kauth_authorize_network(kauth_cred_t cred, kauth_action_t op, enum kauth_network_req req, void *arg1, void *arg2, void *arg3)

The following operations are available for this scope:

KAUTH_NETWORK_ALTQ
    Checks if an ALTQ operation is allowed.

    req indicates the ALTQ subsystem in question, and can be one of the following:

    KAUTH_REQ_NETWORK_ALTQ_AFMAP
    KAUTH_REQ_NETWORK_ALTQ_BLUE
    KAUTH_REQ_NETWORK_ALTQ_CBQ
    KAUTH_REQ_NETWORK_ALTQ_CDNR
    KAUTH_REQ_NETWORK_ALTQ_CONF
    KAUTH_REQ_NETWORK_ALTQ_FIFOQ
    KAUTH_REQ_NETWORK_ALTQ_HFSC
    KAUTH_REQ_NETWORK_ALTQ_JOBS
    KAUTH_REQ_NETWORK_ALTQ_PRIQ
    KAUTH_REQ_NETWORK_ALTQ_RED
    KAUTH_REQ_NETWORK_ALTQ_RIO
    KAUTH_REQ_NETWORK_ALTQ_WFQ

KAUTH_NETWORK_BIND
    Checks if a bind(2) request is allowed.

    req allows to indicate the type of the request to structure listeners and callers easier. Supported request types:

    KAUTH_REQ_NETWORK_BIND_PORT
        Checks if binding to a non-privileged/reserved port is allowed.

    KAUTH_REQ_NETWORK_BIND_PRIVPORT
        Checks if binding to a privileged/reserved port is allowed.

KAUTH_NETWORK_FIREWALL
    Checks if firewall-related operations are allowed.

    req indicates the sub-action, and can be one of the following:

    KAUTH_REQ_NETWORK_FIREWALL_FW
        Modification of packet filtering rules.

    KAUTH_REQ_NETWORK_FIREWALL_NAT
        Modification of NAT rules.

KAUTH_NETWORK_INTERFACE
    Checks if network interface-related operations are allowed.

    arg1 is (optionally) the struct ifnet * associated with the interface. arg2 is (optionally) an int describing the interface-specific operation. arg3 is (optionally) a pointer to the interface-specific request structure. req indicates the sub-action, and can be one of the following:

    KAUTH_REQ_NETWORK_INTERFACE_GET
        Check if retrieving information from the device is allowed.

    KAUTH_REQ_NETWORK_INTERFACE_GETPRIV
        Check if retrieving privileged information from the device is allowed.

    KAUTH_REQ_NETWORK_INTERFACE_SET
        Check if setting parameters on the device is allowed.

    KAUTH_REQ_NETWORK_INTERFACE_SETPRIV
        Check if setting privileged parameters on the device is allowed.

    KAUTH_REQ_NETWORK_INTERFACE_FIRMWARE
        Check if manipulating the firmware on a network interface device is allowed.

    Note that unless the struct ifnet * for the interface was passed in arg1, there's no way to tell what structure arg3 is.

KAUTH_NETWORK_INTERFACE_BRIDGE
    Check if operations performed on the bridge(4) network interface are allowed.

    req can be one of the following:

    KAUTH_REQ_NETWORK_INTERFACE_BRIDGE_GETPRIV
        Check if getting privileges parameters is allowed.

    KAUTH_REQ_NETWORK_INTERFACE_BRIDGE_SETPRIV
        Check if setting privileges parameters is allowed.

KAUTH_NETWORK_INTERFACE_PPP
    Checks if operations performed on the ppp(4) network interface are allowed.

    req can be one of the following:

    KAUTH_REQ_NETWORK_INTERFACE_PPP_ADD
        Checks if adding and enabling a ppp(4) interface to the system is allowed.

KAUTH_NETWORK_INTERFACE_PVC
    Check if operations performed on a PVC device (e.g. en(4)) are allowed. req can be one of the following:

    KAUTH_REQ_NETWORK_INTERFACE_PVC_ADD
        Check if adding a PVC device is allowed.

KAUTH_NETWORK_INTERFACE_SLIP
    Checks if operations performed on the sl(4) network interface are allowed.

    req can be one of the following:

    KAUTH_REQ_NETWORK_INTERFACE_SLIP_ADD
        Checks if adding and enabling a sl(4) interface to the system is allowed.

KAUTH_NETWORK_INTERFACE_STRIP
    Checks if operations performed on the strip(4) network interface are allowed.

    req can be one of the following:

    KAUTH_REQ_NETWORK_INTERFACE_STRIP_ADD
        Check if adding and enabling a strip(4) interface to the system is allowed.

KAUTH_NETWORK_INTERFACE_TUN
    Checks if operations performed on the tun(4) network interface are allowed.

    req can be one of the following:

    KAUTH_REQ_NETWORK_INTERFACE_TUN_ADD
        Checks if adding and enabling a tun(4) interface to the system is allowed.

KAUTH_NETWORK_IPSEC
    Check if operations related to ipsec(4) connections are allowed. req can be one of the following:

    KAUTH_REQ_NETWORK_IPSEC_BYPASS
        Check if bypassing ipsec(4) policy is allowed.

KAUTH_NETWORK_IPV6
    Check if IPv6-specific operations are allowed. req can be one of the following:

    KAUTH_REQ_NETWORK_IPV6_HOPBYHOP
        Check if setting hop-by-hop packet options is allowed.

    KAUTH_REQ_NETWORK_IPV6_JOIN_MULTICAST
        Check if joining a multicast network is allowed.

KAUTH_NETWORK_FORWSRCRT
    Checks whether status of forwarding of source-routed packets can be modified or not.

KAUTH_NETWORK_NFS
    Check if an NFS related operation is allowed.

    req can be any of the following:

    KAUTH_REQ_NETWORK_NFS_EXPORT
        Check if modifying the NFS export table is allowed.

    KAUTH_REQ_NETWORK_NFS_SVC
        Check if access to the NFS nfssvc(2) syscall is allowed.

KAUTH_NETWORK_ROUTE
    Checks if a routing-related request is allowed.

    arg1 is the struct rt_msghdr * for the request.

KAUTH_NETWORK_SMB
    Check if operations related to SMB are allowed.

    req can be one of the following:

    KAUTH_REQ_NETWORK_SMB_SHARE_ACCESS
        Check if accessing an SMB share is allowed.

        arg1 is a struct smb_share * describing the SMB share, and arg2 is a mode_t with the desired access mode.

    KAUTH_REQ_NETWORK_SMB_SHARE_CREATE
        Check if creating an SMB share is allowed.

        arg1 is a struct smb_sharespec * describing the share to be created.

    KAUTH_REQ_NETWORK_SMB_VC_ACCESS
        Check if accessing an SMB VC is allowed.

        arg1 is a struct smb_vc * describing the SMB VC, and arg2 is a mode_t with the desired access mode.

    KAUTH_REQ_NETWORK_SMB_VC_CREATE
        Check if creating an SMB VC is allowed.

        arg1 is a struct smb_vcspec * describing the VC to be created.

KAUTH_NETWORK_SOCKET
    Checks if a socket related operation is allowed.

    req allows to indicate the type of the request to structure listeners and callers easier. Supported request types:

    KAUTH_REQ_NETWORK_SOCKET_RAWSOCK
        Checks if opening a raw socket is allowed.

    KAUTH_REQ_NETWORK_SOCKET_OPEN
        Checks if opening a socket is allowed. arg1, arg2, and arg3 are all int parameters describing the domain, socket type, and protocol, respectively.

    KAUTH_REQ_NETWORK_SOCKET_CANSEE
        Checks if looking at the socket passed is allowed.

        arg1 is a struct socket * describing the socket.

    KAUTH_REQ_NETWORK_SOCKET_DROP
        Checks if a connection can be dropped.

        arg1 is a struct socket * describing the socket.

    KAUTH_REQ_NETWORK_SOCKET_SETPRIV
        Checks if setting privileged socket options is allowed.

        arg1 is a struct socket * describing the socket, arg2 is a u_long describing the socket option.

  Machine-dependent Scope
The machine-dependent (machdep) scope, “org.netbsd.kauth.machdep”, manages machine-dependent authorization requests in the kernel.

The authorization wrapper for this scope is declared as

int kauth_authorize_machdep(kauth_cred_t cred, kauth_action_t op, void *arg0, void *arg1, void *arg2, void *arg3)

The actions on this scope provide a set that may or may not affect all platforms. Below is a list of available actions, along with which platforms are affected by each.

KAUTH_MACHDEP_CACHEFLUSH
    Request to flush the whole CPU cache. Affects m68k Linux emulation.

KAUTH_MACHDEP_CPU_UCODE_APPLY
    Request to apply a CPU microcode to a CPU. This is related to CPU_UCODE, see options(4). Affects i386 and xen.

KAUTH_MACHDEP_IOPERM_GET
    Request to get the I/O permission level. Affects amd64, i386, xen.

KAUTH_MACHDEP_IOPERM_SET
    Request to set the I/O permission level. Affects amd64, i386, xen.

KAUTH_MACHDEP_IOPL
    Request to set the I/O privilege level. Affects amd64, i386, xen.

KAUTH_MACHDEP_LDT_GET
    Request to get the LDT (local descriptor table). Affects amd64, i386, xen.

KAUTH_MACHDEP_LDT_SET
    Request to set the LDT (local descriptor table). Affects amd64, i386, xen.

KAUTH_MACHDEP_MTRR_GET
    Request to get the MTRR (memory type range registers). Affects amd64, i386, xen.

KAUTH_MACHDEP_MTRR_SET
    Request to set the MTRR (memory type range registers). Affects amd64, i386, xen.

KAUTH_MACHDEP_NVRAM
    Request to access (read/write) the NVRAM. Affects i386.

KAUTH_MACHDEP_PXG
    Request to start or stop the pxg(4) CPU. arg0 is true or false, respectively. Affects pmax.

KAUTH_MACHDEP_UNMANAGEDMEM
    Request to access unmanaged memory. Affects alpha, amd64, arm, i386, powerpc, sh3, vax, xen.

  Device Scope
The device scope, “org.netbsd.kauth.device”, manages authorization requests related to devices on the system. Devices can be, for example, terminals, tape drives, Bluetooth accessories, and any other hardware. Network devices specifically are handled by the network scope.

In addition to the standard authorization wrapper:

int kauth_authorize_device(kauth_cred_t cred, kauth_action_t op, void *arg0, void *arg1, void *arg2, void *arg3)

this scope provides authorization wrappers for various device types.

int kauth_authorize_device_tty(kauth_cred_t cred, kauth_action_t op, struct tty *tty)

Authorizes requests for terminal devices on the system. The third argument, tty, is the terminal device in question. It is passed to the listener as arg0. The second argument, op, is the action and can be one of the following:

KAUTH_DEVICE_TTY_OPEN
    Open the terminal device pointed to by tty.

KAUTH_DEVICE_TTY_PRIVSET
    Set privileged settings on the terminal device pointed to by tty.

KAUTH_DEVICE_TTY_STI
    Use the “TIOCSTI” device ioctl(2), allowing to inject characters into the terminal buffer, simulating terminal input.

KAUTH_DEVICE_TTY_VIRTUAL
    Control the virtual console. tty is the current console tty(4).

int kauth_authorize_device_spec(kauth_cred_t cred, enum kauth_device_req req, struct vnode *vp)

Authorizes requests for special files, usually disk devices, but also direct memory access, on the system.

It passes KAUTH_DEVICE_RAWIO_SPEC as the action to the listener, and accepts two arguments. req, passed to the listener as arg0, is access requested, and can be one of KAUTH_REQ_DEVICE_RAWIO_SPEC_READ, KAUTH_REQ_DEVICE_RAWIO_SPEC_WRITE, or KAUTH_REQ_DEVICE_RAWIO_SPEC_RW, representing read, write, or both read/write access respectively. vp is the vnode of the special file in question, and is passed to the listener as arg1.

Keep in mind that it is the responsibility of the security model developer to check whether the underlying device is a disk or the system memory, using iskmemdev():

    if ((vp->v_type == VCHR) &&
        iskmemdev(vp->v_un.vu_specinfo->si_rdev))
    	/* system memory access */

int kauth_authorize_device_passthru(kauth_cred_t cred, dev_t dev, u_long mode, void *data)

Authorizes hardware passthru requests, or user commands passed directly to the hardware. These have the potential of resulting in direct disk and/or memory access.

It passes KAUTH_DEVICE_RAWIO_PASSTHRU as the action to the listener, and accepts three arguments. dev, passed as arg1 to the listener, is the device for which the request is made. mode, passed as arg0 to the listener, is a generic representation of the access mode requested. It can be one or more (binary-OR'd) of the following:

KAUTH_REQ_DEVICE_RAWIO_PASSTHRU_READ
KAUTH_REQ_DEVICE_RAWIO_PASSTHRU_READCONF
KAUTH_REQ_DEVICE_RAWIO_PASSTHRU_WRITE
KAUTH_REQ_DEVICE_RAWIO_PASSTHRU_WRITECONF

data, passed as arg2 to the listener, is device-specific data that may be associated with the request.

  Bluetooth Devices
Authorizing actions relevant to Bluetooth devices is done using the standard authorization wrapper, with the following actions:

KAUTH_DEVICE_BLUETOOTH_BCSP
    Check if operations on a bcsp(4) device are allowed.

    arg0 is an enum kauth_device_req with one of the following values:

    KAUTH_REQ_DEVICE_BLUETOOTH_BCSP_ADD
        Check if adding and enabling a bcsp(4) device is allowed.

KAUTH_DEVICE_BLUETOOTH_BTUART
    Check if operations on a btuart(4) device are allowed.

    arg0 is an enum kauth_device_req with one of the following values:

    KAUTH_REQ_DEVICE_BLUETOOTH_BTUART_ADD
        Check if adding and enabling a btuart(4) device is allowed.

KAUTH_DEVICE_BLUETOOTH_RECV
    Check if a packet can be received from the device.

    arg0 is the packet type. For HCI_CMD_PKT packets, arg1 is the opcode, for HCI_EVENT_PKT packets, arg1 is the event ID, and for HCI_ACLDATA_PKT or HCI_SCODATA_PKT packets, arg1 is the connection handle.

KAUTH_DEVICE_BLUETOOTH_SEND
    Check if a packet can be sent to the device.

    arg0 is a struct hci_unit * describing the HCI unit, arg1 is a hci_cmd_hdr_t * describing the packet header.

KAUTH_DEVICE_BLUETOOTH_SETPRIV
    Check if privileged settings can be changed.

    arg0 is a struct hci_unit * describing the HCI unit, arg1 is a struct btreq * describing the request, and arg2 is a u_long describing the command.

  Kernel random device
Authorization actions relevant to the kernel random device, rnd(4), is done using the standard authorization wrapper, with the following actions:

KAUTH_DEVICE_RND_ADDDATA
    Check if adding data to the entropy pool is allowed.

KAUTH_DEVICE_RND_GETPRIV
    Check if privileged settings and information can be retrieved.

KAUTH_DEVICE_RND_SETPRIV
    Check if privileged settings can be changed.

  Wscons devices
Authorization actions relevant to wscons(4) are done using the standard authorization wrapper, with the following actions:

KAUTH_DEVICE_WSCONS_KEYBOARD_BELL
    Check if setting the default bell is allowed.

KAUTH_DEVICE_WSCONS_KEYBOARD_KEYREPEAT
    Check if setting the default key-repeat is allowed.

  Vnode Scope
The vnode scope, “org.netbsd.kauth.vnode”, authorizes operations made on vnodes representing file system objects.

The authorization wrapper for this scope is declared as

int kauth_authorize_vnode(kauth_cred_t cred, kauth_action_t action, vnode_t *vp, vnode_t *dvp, int fs_decision)

This scope is heavily used in file system code and can potentially affect system-wide performance. Therefore, there are several things developers should know when using it.

First, the action parameter is a bit-mask and multiple actions can be binary-OR'd and authorized in a single call. Two helper functions help generate the action value for a couple of common cases: translating file system access to a kauth action and checking access to a vnode.

The first, kauth_mode_to_action(mode_t access_mode), and returns a kauth_action_t representing the desired access modes. Another function, kauth_access_action(mode_t access_mode, enum vtype v_type, mode_t file_mode), returns a kauth_action_t suitable for use in many file system access(2) implementations. It calls the aforementioned kauth_mode_to_action(), but before returning also adds the KAUTH_VNODE_IS_EXEC flag if needed. See below for the meaning of this flag and how its necessity is determined.

Second, it is recommended to be very careful with adding listeners on this scope. A special parameter, fs_decision, allows different file systems to instrument different policies without adding their own listener. This parameter is special because it also serves as a fall-back decision when no secmodel(9) is present to prevent a fail-open scenario. It can take either an errno(2) value or “KAUTH_VNODE_REMOTEFS”, indicating that the file system on which the authorization is made is remote and cannot provide us with a fall-back decision. In this case, kauth can only short-circuit the request but the file system will have the last word if there is no definitive allow or deny decision.

The value of fs_decision can be hard-coded or determined by calling an internal function implementing a policy. For the latter case, genfs(9) provides a set of helper functions that implement common policies that file systems can use. The calling convention is as follows:

    int error;
    error = kauth_authorize_vnode(..., genfs_can_foo(...));

Actions on the vnode scope are of two types: operations and flags. An operation is similar in concept to actions on other scopes in the sense that it represents an operation desired by the caller. A flag is an indicator of additional information about the vnode that a file system can set in order to allow the listener to make a more informed decision.

Actions include the following:

KAUTH_VNODE_READ_DATA
    Read file data.

KAUTH_VNODE_LIST_DIRECTORY
    Read directory listing. Identical to the above.

KAUTH_VNODE_WRITE_DATA
    Write file data.

KAUTH_VNODE_ADD_FILE
    Add a file to a directory. Identical to the above.

KAUTH_VNODE_EXECUTE
    Execute a file.

KAUTH_VNODE_SEARCH
    Search (enter) a directory. Identical to the above.

KAUTH_VNODE_DELETE
    Delete a file.

KAUTH_VNODE_APPEND_DATA
    Append data to a file.

KAUTH_VNODE_ADD_SUBDIRECTORY
    Add a subdirectory to a directory. Identical to the above.

KAUTH_VNODE_READ_TIMES
    Read the created, last accessed, and last modified times of a file.

KAUTH_VNODE_WRITE_TIMES
    Modify the created, last accessed, or last modified times of a file.

KAUTH_VNODE_READ_FLAGS
    Read file flags.

KAUTH_VNODE_WRITE_FLAGS
    Modify file flags.

KAUTH_VNODE_READ_SYSFLAGS
    Read file system flags.

KAUTH_VNODE_WRITE_SYSFLAGS
    Modify file system flags.

KAUTH_VNODE_RENAME
    Rename a file.

KAUTH_VNODE_CHANGE_OWNERSHIP
    Change ownership of a file.

KAUTH_VNODE_READ_SECURITY
    Read the permissions of a file.

KAUTH_VNODE_WRITE_SECURITY
    Change the permissions of a file, for example by using chmod(2).

KAUTH_VNODE_READ_ATTRIBUTES
    Read attributes of a file.

KAUTH_VNODE_WRITE_ATTRIBUTES
    Modify attributes of a file.

KAUTH_VNODE_READ_EXTATTRIBUTES
    Read extended attributes of a file.

KAUTH_VNODE_WRITE_EXTATTRIBUTES
    Modify extended attributes of a file.

KAUTH_VNODE_RETAIN_SUID
    Check if retaining the set-user-id bit on files after chown(2) is allowed.

KAUTH_VNODE_RETAIN_SGID
    Check if retaining the set-group-id bit on files after chown(2) is allowed.

KAUTH_VNODE_REVOKE
    Revoke a file.

Flags include the following:

KAUTH_VNODE_IS_EXEC
    The vnode is executable.

    The macro FS_OBJECT_CAN_EXEC() can be used to help determine if this flag should be set. This macro determines a file system object to be executable if it is a directory (in which case we say it is searchable) or if it has at least one executable bit set in its mode.

    Setting this flag helps a listener know that a vnode is executable and is used in implementing privileged access to files and directories while maintaining semantics that prevent execution until a file is marked as an executable. An example for using this in listener code is:

        if (privileged) {
        	/* Always allow read/write; execute only if executable. */
        	if ((action & KAUTH_VNODE_EXECUTE) == 0 ||
        	    (action & KAUTH_VNODE_IS_EXEC))
        		result = KAUTH_RESULT_ALLOW;
        }

    Finally, the vnode scope authorization wrapper returns EACCES in case of an error, to maintain file system semantics. File systems can override this value if needed.

KAUTH_VNODE_HAS_SYSFLAGS
    The file system object represented by the vnode has system flags set.

KAUTH_VNODE_ACCESS
    The authorization is advisory only and no actual operation is to be performed. This is not implemented.

  Credentials Scope
The credentials scope, “org.netbsd.kauth.cred”, is a special scope used internally by the kauth framework to provide hooking to credential-related operations.

It is a “notify-only” scope, allowing hooking operations such as initialization of new credentials, credential inheritance during a fork, and copying and freeing of credentials. The main purpose for this scope is to give a security model a way to control the aforementioned operations, especially in cases where the credentials hold security model-private data.

Notifications are made using the following function, which is internal to kauth:

int kauth_cred_hook(kauth_cred_t cred, kauth_action_t action, void *arg0, void *arg1)

With the following actions:

KAUTH_CRED_COPY
    The credentials are being copied. cred are the credentials of the lwp context doing the copy, and arg0 and arg1 are both kauth_cred_t representing the “from” and “to” credentials, respectively.

KAUTH_CRED_FORK
    The credentials are being inherited from a parent to a child process during a fork.

    cred are the credentials of the lwp context doing the fork, and arg0 and arg1 are both struct proc * of the parent and child processes, respectively.

KAUTH_CRED_CHROOT
    The credentials in cred belong to a process whose root directory is changed through change_root() (see vfs(9) ).

    Arg0 is the new struct cwdinfo * of the process.

KAUTH_CRED_FREE
    The credentials in cred are being freed.

KAUTH_CRED_INIT
    The credentials in cred are being initialized.

Since this is a notify-only scope, all listeners are required to return KAUTH_RESULT_ALLOW.

  Credentials Accessors and Mutators
kauth has a variety of accessor and mutator routines to handle kauth_cred_t objects.

The following routines can be used to access and modify the user- and group-ids in a kauth_cred_t:

uid_t kauth_cred_getuid(kauth_cred_t cred)
    Returns the real user-id from cred.

uid_t kauth_cred_geteuid(kauth_cred_t cred)
    Returns the effective user-id from cred.

uid_t kauth_cred_getsvuid(kauth_cred_t cred)
    Returns the saved user-id from cred.

void kauth_cred_setuid(kauth_cred_t cred, uid_t uid)
    Sets the real user-id in cred to uid.

void kauth_cred_seteuid(kauth_cred_t cred, uid_t uid)
    Sets the effective user-id in cred to uid.

void kauth_cred_setsvuid(kauth_cred_t cred, uid_t uid)
    Sets the saved user-id in cred to uid.

gid_t kauth_cred_getgid(kauth_cred_t cred)
    Returns the real group-id from cred.

gid_t kauth_cred_getegid(kauth_cred_t cred)
    Returns the effective group-id from cred.

gid_t kauth_cred_getsvgid(kauth_cred_t cred)
    Returns the saved group-id from cred.

void kauth_cred_setgid(kauth_cred_t cred, gid_t gid)
    Sets the real group-id in cred to gid.

void kauth_cred_setegid(kauth_cred_t cred, gid_t gid)
    Sets the effective group-id in cred to gid.

void kauth_cred_setsvgid(kauth_cred_t cred, gid_t gid)
    Sets the saved group-id in cred to gid.

u_int kauth_cred_getrefcnt(kauth_cred_t cred)
    Return the reference count for cred.

The following routines can be used to access and modify the group list in a kauth_cred_t:

int kauth_cred_ismember_gid(kauth_cred_t cred, gid_t gid, int *resultp)
    Checks if the group-id gid is a member in the group list of cred.

    If it is, resultp will be set to one, otherwise, to zero.

    The return value is an error code, or zero for success.

u_int kauth_cred_ngroups(kauth_cred_t cred)
    Return the number of groups in the group list of cred.

gid_t kauth_cred_group(kauth_cred_t cred, u_int idx)
    Return the group-id of the group at index idx in the group list of cred.

int kauth_cred_setgroups(kauth_cred_t cred, const gid_t *groups, size_t ngroups, uid_t gmuid, enum uio_seg seg)
    Copy ngroups groups from array pointed to by groups to the group list in cred, adjusting the number of groups in cred appropriately. seg should be either UIO_USERSPACE or UIO_SYSSPACE indicating whether groups is a user or kernel space address.

    Any groups remaining will be set to an invalid value.

    gmuid is unused for now, and to maintain interface compatibility with the Darwin KPI.

    The return value is an error code, or zero for success.

int kauth_cred_getgroups(kauth_cred_t cred, gid_t *groups, size_t ngroups, enum uio_seg seg)
    Copy ngroups groups from the group list in cred to the buffer pointed to by groups. seg should be either UIO_USERSPACE or UIO_SYSSPACE indicating whether groups is a user or kernel space address.

    The return value is an error code, or zero for success.

  Credential Private Data
kauth provides an interface to allow attaching security-model private data to credentials.

The use of this interface has two parts that can be divided to direct and indirect control of the private-data. Directly controlling the private data is done by using the below routines, while the indirect control is often dictated by events such as process fork, and is handled by listening on the credentials scope (see above).

Attaching private data to credentials works by registering a key to serve as a unique identifier, distinguishing various sets of private data that may be associated with the credentials. Registering, and deregistering, a key is done by using these routines:

int kauth_register_key(secmodel_t sm, kauth_key_t *keyp)
    Register new key for private data for security model sm. keyp will be used to return the key to be used in further calls.

    The function returns 0 on success and an error code (see errno(2)) on failure.

int kauth_deregister_key(kauth_key_t key)
    Deregister private data key key.

Once registered, private data may be manipulated by the following routines:

void kauth_cred_setdata(kauth_cred_t cred, kauth_key_t key, void *data)
    Set private data for key in cred to be data.

void * kauth_cred_getdata(kauth_cred_t cred, kauth_key_t key)
    Retrieve private data for key in cred.

Note that it is required to use the above routines every time the private data is changed, i.e., using kauth_cred_getdata() and later modifying the private data should be accompanied by a call to kauth_cred_setdata() with the “new” private data.

  Credential Inheritance and Reference Counting
kauth provides an interface for handling shared credentials.

When a kauth_cred_t is first allocated, its reference count is set to 1. However, with time, its reference count can grow as more objects (processes, LWPs, files, etc.) reference it.

The following routines are available for managing credentials reference counting:

void kauth_cred_hold(kauth_cred_t cred)
    Increases reference count to cred by one.

void kauth_cred_free(kauth_cred_t cred)
    Decreases the reference count to cred by one.

    If the reference count dropped to zero, the memory used by cred will be freed.

Credential inheritance happens during a fork(2), and is handled by the following function:

void kauth_proc_fork(struct proc *parent, struct proc *child)

When called, it references the parent's credentials from the child, and calls the credentials scope's hook with the KAUTH_CRED_FORK action to allow security model-specific handling of the inheritance to take place.

  Credentials Memory Management
Data-structures for credentials, listeners, and scopes are allocated from memory pools managed by the pool(9) subsystem.

The kauth_cred_t objects have their own memory management routines:

kauth_cred_t kauth_cred_alloc(void)
    Allocates a new kauth_cred_t, initializes its lock, and sets its reference count to one.

  Conversion Routines
Sometimes it might be necessary to convert a kauth_cred_t to userland's view of credentials, a struct uucred, or vice versa.

The following routines are available for these cases:

void kauth_uucred_to_cred(kauth_cred_t cred, const struct uucred *uucred)
    Convert userland's view of credentials to a kauth_cred_t.

    This includes effective user- and group-ids, a number of groups, and a group list. The reference count is set to one.

    Note that kauth will try to copy as many groups as can be held inside a kauth_cred_t.

void kauth_cred_to_uucred(struct uucred *uucred, const kauth_cred_t cred)
    Convert kauth_cred_t to userland's view of credentials.

    This includes effective user- and group-ids, a number of groups, and a group list.

    Note that kauth will try to copy as many groups as can be held inside a struct uucred.

int kauth_cred_uucmp(kauth_cred_t cred, struct uucred *uucred)
    Compares cred with the userland credentials in uucred.

    Common values that will be compared are effective user- and group-ids, and the group list.

  Miscellaneous Routines
Other routines provided by kauth are:

void kauth_cred_clone(kauth_cred_t cred1, kauth_cred_t cred2)
    Clone credentials from cred1 to cred2, except for the lock and reference count.

kauth_cred_t kauth_cred_dup(kauth_cred_t cred)
    Duplicate cred.

    What this routine does is call kauth_cred_alloc() followed by a call to kauth_cred_clone().

kauth_cred_t kauth_cred_copy(kauth_cred_t cred)
    Works like kauth_cred_dup(), except for a few differences.

    If cred already has a reference count of one, it will be returned. Otherwise, a new kauth_cred_t will be allocated and the credentials from cred will be cloned to it. Last, a call to kauth_cred_free() for cred will be done.

kauth_cred_t kauth_cred_get(void)
    Return the credentials associated with the current LWP. This does not change the reference count of the resulting kauth_cred_t object.

  Scope Management
kauth provides routines to manage the creation and deletion of scopes on the system.

Note that the built-in scopes, the “generic” scope and the “process” scope, can't be deleted.

kauth_scope_t kauth_register_scope(const char *id, kauth_scope_callback_t cb, void *cookie)
    Register a new scope on the system. id is the name of the scope, usually in reverse DNS-like notation. For example, “org.netbsd.kauth.myscope”. cb is the default listener, to which authorization requests for this scope will be dispatched to. cookie is optional user-data that will be passed to all listeners during authorization on the scope.

void kauth_deregister_scope(kauth_scope_t scope)
    Deregister scope from the scopes available on the system, and free the kauth_scope_t object scope.

  Listener Management
Listeners in kauth are authorization callbacks that are called during an authorization request in the scope which they belong to.

When an authorization request is made, all listeners associated with a scope are called to allow, deny, or defer the request.

It is enough for one listener to deny the request in order for the request to be denied; but all listeners are called during an authorization process none-the-less. All listeners are required to allow the request for it to be granted, and in a case where all listeners defer the request — leaving the decision for other listeners — the request is denied.

The following KPI is provided for the management of listeners:

kauth_listener_t kauth_listen_scope(const char *id, kauth_scope_callback_t cb, void *cookie)
    Create a new listener on the scope with the id id, setting the default listener to cb. cookie is optional user-data that will be passed to the listener when called during an authorization request.

void kauth_unlisten_scope(kauth_listener_t listener)
    Removes listener from the scope which it belongs to, ensuring it won't be called again, and frees the kauth_listener_t object listener.

kauth provides no means for synchronization within listeners. It is the programmer's responsibility to make sure data used by the listener is properly locked during its use, as it can be accessed simultaneously from the same listener called multiple times. It is also the programmer's responsibility to do garbage collection after the listener, possibly freeing any allocated data it used.

The common method to do the above is by having a reference count to each listener. On entry to the listener, this reference count should be raised; on exit, lowered.

During the removal of a listener, first kauth_scope_unlisten() should be called to make sure the listener code will not be entered in the future. Then, the code should wait (possibly sleeping) until the reference count drops to zero. When that happens, it is safe to do the final cleanup.

Listeners might sleep, so no locks can be held when calling an authorization wrapper.

EXAMPLES
Older code had no abstraction of the security model, so most privilege checks looked like this:

    if (suser(cred, &acflag) == 0)
    	/* allow privileged operation */

Using the new interface, you must ask for a specific privilege explicitly. For example, checking whether it is possible to open a socket would look something like this:

    if (kauth_authorize_network(cred, KAUTH_NETWORK_SOCKET,
        KAUTH_REQ_NETWORK_SOCKET_OPEN, PF_INET, SOCK_STREAM,
        IPPROTO_TCP) == 0)
    	/* allow opening the socket */

Note that the securelevel implications were also integrated into the kauth framework so you don't have to note anything special in the call to the authorization wrapper, but rather just have to make sure the security model handles the request as you expect it to.

To do that you can just grep(1) in the relevant security model directory and have a look at the code.

EXTENDING KAUTH
Although kauth provides a large set of both detailed and more or less generic requests, it might be needed eventually to introduce more scopes, actions, or requests.

Adding a new scope should happen only when an entire subsystem is introduced and it is assumed other parts of the kernel may want to interfere with its inner-workings. When a subsystem that has the potential of impacting the security of the system is introduced, existing security modules must be updated to also handle actions on the newly added scope.

New actions should be added when sets of operations not covered at all belong in an already existing scope.

Requests (or sub-actions) can be added as subsets of existing actions when an operation that belongs in an already covered area is introduced.

Note that all additions should include updates to this manual, the security models shipped with NetBSD, and the example skeleton security model.

SEE ALSO
secmodel(9)

HISTORY
The kernel authorization framework first appeared in Mac OS X 10.4.

The kernel authorization framework in NetBSD first appeared in NetBSD 4.0, and is a clean-room implementation based on Apple TN2127, available at http://developer.apple.com/technotes/tn2005/tn2127.html

NOTES
As kauth in NetBSD is still under active development, it is likely that the ABI, and possibly the API, will differ between NetBSD versions. Developers are to take notice of this fact in order to avoid building code that expects one version of the ABI and running it in a system with a different one.

AUTHORS
Elad Efrat <elad@NetBSD.org> implemented the kernel authorization framework in NetBSD.

Jason R. Thorpe <thorpej@NetBSD.org> provided guidance and answered questions about the Darwin implementation.