freebsd-nq/share/man/man9/ieee80211_crypto.9

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.\" Copyright (c) 2004 Bruce M. Simpson <bms@spc.org>
.\" Copyright (c) 2004 Darron Broad <darron@kewl.org>
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.\" $FreeBSD$
.\" $Id: ieee80211_crypto.9,v 1.3 2004/03/04 10:42:56 bruce Exp $
.\"
.Dd March 29, 2010
.Dt IEEE80211_CRYPTO 9
.Os
.Sh NAME
.Nm ieee80211_crypto
.Nd 802.11 cryptographic support
.Sh SYNOPSIS
.In net80211/ieee80211_var.h
.\"
.Pp
.Ft void
.Fn ieee80211_crypto_register "const struct ieee80211_cipher *"
.\"
.Ft void
.Fn ieee80211_crypto_unregister "const struct ieee80211_cipher *"
.\"
.Ft int
.Fn ieee80211_crypto_available "int cipher"
.\"
.Pp
.Ft void
.Fo ieee80211_notify_replay_failure
.Fa "struct ieee80211vap *"
.Fa "const struct ieee80211_frame *"
.Fa "const struct ieee80211_key *"
.Fa "uint64_t rsc"
.Fa "int tid"
.Fc
.\"
.Ft void
.Fo ieee80211_notify_michael_failure
.Fa "struct ieee80211vap *"
.Fa "const struct ieee80211_frame *"
.Fa "u_int keyix"
.Fc
.\"
.Ft int
.Fo ieee80211_crypto_newkey
.Fa "struct ieee80211vap *"
.Fa "int cipher"
.Fa "int flags"
.Fa "struct ieee80211_key *"
.Fc
.\"
.Ft int
.Fn ieee80211_crypto_setkey "struct ieee80211vap *" "struct ieee80211_key *"
.\"
.Ft int
.Fn ieee80211_crypto_delkey "struct ieee80211vap *" "struct ieee80211_key *"
.\"
.Ft void
.Fn ieee80211_key_update_begin "struct ieee80211vap *"
.\"
.Ft void
.Fn ieee80211_key_update_end "struct ieee80211vap *"
.\"
.Ft void
.Fn ieee80211_crypto_delglobalkeys "struct ieee80211vap *"
.\"
.Ft void
.Fn ieee80211_crypto_reload_keys "struct ieee80211com *"
.\"
.Pp
.Ft struct ieee80211_key *
.Fn ieee80211_crypto_encap "struct ieee80211_node *" "struct mbuf *"
.\"
.Ft struct ieee80211_key *
.Fn ieee80211_crypto_decap "struct ieee80211_node *" "struct mbuf *" "int flags"
.\"
.Ft int
.Fo ieee80211_crypto_demic
.Fa "struct ieee80211vap *"
.Fa "struct ieee80211_key *"
.Fa "struct mbuf *"
.Fa "int force"
.Fc
.\"
.Ft int
.Fo ieee80211_crypto_enmic
.Fa "struct ieee80211vap *"
.Fa "struct ieee80211_key *"
.Fa "struct mbuf *"
.Fa "int force"
.Fc
.Sh DESCRIPTION
The
.Nm net80211
layer includes comprehensive cryptographic support for 802.11 protocols.
Software implementations of ciphers required by
WPA and 802.11i are provided as well as encap/decap processing of 802.11 frames.
Software ciphers are written as kernel modules and
register with the core crypto support.
The cryptographic framework supports hardware acceleration of ciphers
by drivers with automatic fall-back to software implementations when a
driver is unable to provide necessary hardware services.
.Sh CRYPTO CIPHER MODULES
.Nm net80211
cipher modules register their services using
.Fn ieee80211_crypto_register
and supply a template that describes their operation.
This 
.Vt ieee80211_cipher
structure defines protocol-related state such as the number of bytes
of space in the 802.11 header to reserve/remove during encap/decap
and entry points for setting up keys and doing cryptographic operations.
.Pp
Cipher modules can associate private state to each key through the
.Vt wk_private
structure member.
If state is setup by the module it will be called before a key is destroyed
so it can reclaim resources.
.Pp
Crypto modules can notify the system of two events.
When a packet replay event is recognized
.Fn ieee80211_notify_replay_failure
can be used to signal the event.
When a
.Dv TKIP
Michael failure is detected
.Fn ieee80211_notify_michael_failure
can be invoked.
Drivers may also use these routines to signal events detected by the
hardware.
.Sh CRYPTO KEY MANAGEMENT
The
.Nm net80211
layer implements a per-vap 4-element 
.Dq global key table
and a per-station
.Dq unicast key
for protocols such as WPA, 802.1x, and 802.11i.
The global key table is designed to support legacy WEP operation
and Multicast/Group keys,
though some applications also use it to implement WPA in station mode.
Keys in the global table are identified by a key index in the range 0-3.
Per-station keys are identified by the MAC address of the station and
are typically used for unicast PTK bindings.
.Pp
.Nm net80211
provides
.Xr ioctl 2
operations for managing both global and per-station keys.
Drivers typically do not participate in software key management;
they are involved only when providing hardware acceleration of
cryptographic operations.
.Pp
.Fn ieee80211_crypto_newkey
is used to allocate a new
.Nm net80211
key or reconfigure an existing key.
The cipher must be specified along with any fixed key index.
The
.Nm net80211
layer will handle allocating cipher and driver resources to support the key.
.Pp
Once a key is allocated it's contents can be set using
.Fn ieee80211_crypto_setkey
and deleted with
.Fn ieee80211_crypto_delkey
(with any cipher and driver resources reclaimed).
.Pp
.Fn ieee80211_crypto_delglobalkeys
is used to reclaim all keys in the global key table for a vap; it
typically is used only within the
.Nm net80211
layer.
.Pp
.Fn ieee80211_crypto_reload_keys
handles hardware key state reloading from software key state, such
as required after a suspend/resume cycle.
.Sh DRIVER CRYPTO SUPPORT
Drivers identify ciphers they have hardware support for through the
.Vt ic_cryptocaps
field of the
.Vt ieee80211com
structure.
If hardware support is available then a driver should also fill in the
.Dv iv_key_alloc ,
.Dv iv_key_set ,
and
.Dv iv_key_delete
methods of each
.Vt ieee80211vap
created for use with the device.
In addition the methods
.Dv iv_key_update_begin
and
.Dv iv_key_update_end
can be setup to handle synchronization requirements
for updating hardware key state.
.Pp
When
.Nm net80211
allocates a software key and the driver can accelerate the
cipher operations the
.Dv iv_key_alloc
method will be invoked.
Drivers may return a token that is associated with outbound traffic
(for use in encrypting frames).
Otherwise, e.g. if hardware resources are not available, the driver will
not return a token and
.Nm net80211
will arrange to do the work in software and pass frames
to the driver that are already prepared for transmission.
.Pp
For receive, drivers mark frames with the
.Dv M_WEP
mbuf flag to indicate the hardware has decrypted the payload.
If frames have the 
.Dv IEEE80211_FC1_WEP
bit marked in their 802.11 header and are not tagged with
.Dv M_WEP
then decryption is done in software.
For more complicated scenarios the software key state is consulted; e.g.
to decide if Michael verification needs to be done in software after
the hardware has handled TKIP decryption.
.Pp
Drivers that manage complicated key data structures, e.g. faulting
software keys into a hardware key cache, can safely manipulate software
key state by bracketing their work with calls to
.Fn ieee80211_key_update_begin
and
.Fn ieee80211_key_update_end .
These calls also synchronize hardware key state update
when receive traffic is active.
.Sh SEE ALSO
.Xr ieee80211 9 ,
.Xr ioctl 2 ,
.Xr wlan_ccmp 4 ,
.Xr wlan_tkip 4 ,
.Xr wlan_wep 4