wpa.h

Go to the documentation of this file.

/*
 * Copyright (c) 2009 Joshua Oreman <oremanj@rwcr.net>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */
 
#ifndef _IPXE_WPA_H
#define _IPXE_WPA_H
 
#include <ipxe/ieee80211.h>
#include <ipxe/list.h>
 
FILE_LICENCE ( GPL2_OR_LATER );
 
/** @file
 *
 * Common definitions for all types of WPA-protected networks.
 */
 
 
/** EAPOL-Key type field for modern 802.11i/RSN WPA packets */
#define EAPOL_KEY_TYPE_RSN      2
 
/** Old EAPOL-Key type field used by WPA1 hardware before 802.11i ratified */
#define EAPOL_KEY_TYPE_WPA      254
 
 
/**
 * @defgroup eapol_key_info EAPOL-Key Info field bits
 * @{
 */
 
/** Key descriptor version, indicating WPA or WPA2 */
#define EAPOL_KEY_INFO_VERSION  0x0007
 
/** Key type bit, indicating pairwise or group */
#define EAPOL_KEY_INFO_TYPE     0x0008
 
/** Key install bit; set on message 3 except when legacy hacks are used */
#define EAPOL_KEY_INFO_INSTALL  0x0040
 
/** Key ACK bit; set when a response is required, on all messages except #4 */
#define EAPOL_KEY_INFO_KEY_ACK  0x0080
 
/** Key MIC bit; set when the MIC field is valid, on messages 3 and 4 */
#define EAPOL_KEY_INFO_KEY_MIC  0x0100
 
/** Secure bit; set when both sides have both keys, on messages 3 and 4 */
#define EAPOL_KEY_INFO_SECURE   0x0200
 
/** Error bit; set on a MIC failure for TKIP */
#define EAPOL_KEY_INFO_ERROR    0x0400
 
/** Request bit; set when authentication is initiated by the Peer (unusual) */
#define EAPOL_KEY_INFO_REQUEST  0x0800
 
/** Key Encrypted bit; set when the Key Data field is encrypted */
#define EAPOL_KEY_INFO_KEY_ENC  0x1000
 
/** SMC Message bit; set when this frame is part of an IBSS SMK handshake */
#define EAPOL_KEY_INFO_SMC_MESS 0x2000
 
 
/** Key descriptor version field value for WPA (TKIP) */
#define EAPOL_KEY_VERSION_WPA   1
 
/** Key descriptor version field value for WPA2 (CCMP) */
#define EAPOL_KEY_VERSION_WPA2  2
 
/** Key type field value for a PTK (pairwise) key handshake */
#define EAPOL_KEY_TYPE_PTK      0x0008
 
/** Key type field value for a GTK (group) key handshake */
#define EAPOL_KEY_TYPE_GTK      0x0000
 
/** @} */
 
 
 
/** An EAPOL-Key packet.
 *
 * These are used for the WPA 4-Way Handshake, whether or not prior
 * authentication has been performed using EAP.
 *
 * On LANs, an eapol_key_pkt is always encapsulated in the data field
 * of an eapol_frame, with the frame's type code set to EAPOL_TYPE_KEY.
 *
 * Unlike 802.11 frame headers, the fields in this structure are
 * stored in big-endian!
 */
struct eapol_key_pkt
{
        /** One of the EAPOL_KEY_TYPE_* defines. */
        u8 type;
 
        /** Bitfield of key characteristics, network byte order */
        u16 info;
 
        /** Length of encryption key to be used, network byte order
         *
         * This is 16 for CCMP, 32 for TKIP, and 5 or 13 for WEP.
         */
        u16 keysize;
 
        /** Monotonically increasing value for EAPOL-Key conversations
         *
         * In another classic demonstration of overengineering, this
         * 8-byte value will rarely be anything above 1. It's stored
         * in network byte order.
         */
        u64 replay;
 
        /** Nonce value
         *
         * This is the authenticator's ANonce in frame 1, the peer's
         * SNonce in frame 2, and 0 in frames 3 and 4.
         */
        u8 nonce[32];
 
        /** Initialization vector
         *
         * This contains the IV used with the Key Encryption Key, or 0
         * if the key is unencrypted or encrypted using an algorithm
         * that does not require an IV.
         */
        u8 iv[16];
 
        /** Receive sequence counter for GTK
         *
         * This is used to synchronize the client's replay counter for
         * ordinary data packets. The first six bytes contain PN0
         * through PN5 for CCMP mode, or TSC0 through TSC5 for TKIP
         * mode. The last two bytes are zero.
         */
        u8 rsc[8];
 
        /** Reserved bytes */
        u8 _reserved[8];
 
        /** Message integrity code over the entire EAPOL frame
         *
         * This is calculated using HMAC-MD5 when the key descriptor
         * version field in @a info is 1, and HMAC-SHA1 ignoring the
         * last 4 bytes of the hash when the version field in @a info
         * is 2.
         */
        u8 mic[16];
 
        /** Length of the @a data field in bytes, network byte order */
        u16 datalen;
 
        /** Key data
         *
         * This is formatted as a series of 802.11 information
         * elements, with cryptographic data encapsulated using a
         * "vendor-specific IE" code and an IEEE-specified OUI.
         */
        u8 data[0];
} __attribute__ (( packed ));
 
 
/** WPA handshaking state */
enum wpa_state {
        /** Waiting for PMK to be set */
        WPA_WAITING = 0,
 
        /** Ready for 4-Way Handshake */
        WPA_READY,
 
        /** Performing 4-Way Handshake */
        WPA_WORKING,
 
        /** 4-Way Handshake succeeded */
        WPA_SUCCESS,
 
        /** 4-Way Handshake failed */
        WPA_FAILURE,
};
 
/** Bitfield indicating a selection of WPA transient keys */
enum wpa_keymask {
        /** Pairwise transient key */
        WPA_PTK = 1,
 
        /** Group transient key */
        WPA_GTK = 2,
};
 
 
/** Length of a nonce */
#define WPA_NONCE_LEN           32
 
/** Length of a TKIP main key */
#define WPA_TKIP_KEY_LEN        16
 
/** Length of a TKIP MIC key */
#define WPA_TKIP_MIC_KEY_LEN    8
 
/** Length of a CCMP key */
#define WPA_CCMP_KEY_LEN        16
 
/** Length of an EAPOL Key Confirmation Key */
#define WPA_KCK_LEN             16
 
/** Length of an EAPOL Key Encryption Key */
#define WPA_KEK_LEN             16
 
/** Usual length of a Pairwise Master Key */
#define WPA_PMK_LEN             32
 
/** Length of a PMKID */
#define WPA_PMKID_LEN           16
 
 
/** Structure of the Temporal Key for TKIP encryption */
struct tkip_tk
{
        /** Main key: input to TKIP Phase 1 and Phase 2 key mixing functions */
        u8 key[WPA_TKIP_KEY_LEN];
 
        /** Michael MIC keys */
        struct {
                /** MIC key for packets from the AP */
                u8 rx[WPA_TKIP_MIC_KEY_LEN];
 
                /** MIC key for packets to the AP */
                u8 tx[WPA_TKIP_MIC_KEY_LEN];
        } __attribute__ (( packed )) mic;
} __attribute__ (( packed ));
 
/** Structure of a generic Temporal Key */
union wpa_tk
{
        /** CCMP key */
        u8 ccmp[WPA_CCMP_KEY_LEN];
 
        /** TKIP keys */
        struct tkip_tk tkip;
};
 
/** Structure of the Pairwise Transient Key */
struct wpa_ptk
{
        /** EAPOL-Key Key Confirmation Key (KCK) */
        u8 kck[WPA_KCK_LEN];
 
        /** EAPOL-Key Key Encryption Key (KEK) */
        u8 kek[WPA_KEK_LEN];
 
        /** Temporal key */
        union wpa_tk tk;
} __attribute__ (( packed ));
 
/** Structure of the Group Transient Key */
struct wpa_gtk
{
        /** Temporal key */
        union wpa_tk tk;
} __attribute__ (( packed ));
 
 
/** Common context for WPA security handshaking
 *
 * Any implementor of a particular handshaking type (e.g. PSK or EAP)
 * must include this structure at the very beginning of their private
 * data context structure, to allow the EAPOL-Key handling code to
 * work. When the preliminary authentication is done, it is necessary
 * to call wpa_start(), passing the PMK (derived from PSK or EAP MSK)
 * as an argument. The handshaker can use its @a step function to
 * monitor @a state in this wpa_ctx structure for success or
 * failure. On success, the keys will be available in @a ptk and @a
 * gtk according to the state of the @a valid bitmask.
 *
 * After an initial success, the parent handshaker does not need to
 * concern itself with rekeying; the WPA common code takes care of
 * that.
 */
struct wpa_common_ctx
{
        /** 802.11 device we are authenticating for */
        struct net80211_device *dev;
 
        /** The Pairwise Master Key to use in handshaking
         *
         * This is set either by running the PBKDF2 algorithm on a
         * passphrase with the SSID as salt to generate a pre-shared
         * key, or by copying the first 32 bytes of the EAP Master
         * Session Key in 802.1X-served authentication.
         */
        u8 pmk[WPA_PMK_LEN];
 
        /** Length of the Pairwise Master Key
         *
         * This is always 32 except with one EAP method which only
         * gives 16 bytes.
         */
        int pmk_len;
 
        /** State of EAPOL-Key handshaking */
        enum wpa_state state;
 
        /** Replay counter for this association
         *
         * This stores the replay counter value for the most recent
         * packet we've accepted. It is initially initialised to ~0 to
         * show we'll accept anything.
         */
        u64 replay;
 
        /** Mask of valid keys after authentication success
         *
         * If the PTK is not valid, the GTK should be used for both
         * unicast and multicast decryption; if the GTK is not valid,
         * multicast packets cannot be decrypted.
         */
        enum wpa_keymask valid;
 
        /** The cipher to use for unicast RX and all TX */
        enum net80211_crypto_alg crypt;
 
        /** The cipher to use for broadcast and multicast RX */
        enum net80211_crypto_alg gcrypt;
 
        /** The Pairwise Transient Key derived from the handshake */
        struct wpa_ptk ptk;
 
        /** The Group Transient Key derived from the handshake */
        struct wpa_gtk gtk;
 
        /** Authenticator-provided nonce */
        u8 Anonce[WPA_NONCE_LEN];
 
        /** Supplicant-generated nonce (that's us) */
        u8 Snonce[WPA_NONCE_LEN];
 
        /** Whether we should refrain from generating another SNonce */
        int have_Snonce;
 
        /** Data in WPA or RSN IE from AP's beacon frame */
        void *ap_rsn_ie;
 
        /** Length of @a ap_rsn_ie */
        int ap_rsn_ie_len;
 
        /** Whether @a ap_rsn_ie is an RSN IE (as opposed to old WPA) */
        int ap_rsn_is_rsn;
 
        /** List entry */
        struct list_head list;
};
 
 
/** WPA handshake key integrity and encryption handler
 *
 * Note that due to the structure of the 4-Way Handshake we never
 * actually need to encrypt key data, only decrypt it.
 */
struct wpa_kie {
        /** Value of version bits in EAPOL-Key info field for which to use
         *
         * This should be one of the @c EAPOL_KEY_VERSION_* constants.
         */
        int version;
 
        /** Calculate MIC over message
         *
         * @v kck       Key Confirmation Key, 16 bytes
         * @v msg       Message to calculate MIC over
         * @v len       Number of bytes to calculate MIC over
         * @ret mic     Calculated MIC, 16 bytes long
         *
         * The @a mic return may point within @a msg, so it must not
         * be filled until the calculation has been performed.
         */
        void ( * mic ) ( const void *kck, const void *msg, size_t len,
                         void *mic );
 
        /** Decrypt key data
         *
         * @v kek       Key Encryption Key, 16 bytes
         * @v iv        Initialisation vector for encryption, 16 bytes
         * @v msg       Message to decrypt (Key Data field)
         * @v len       Length of message
         * @ret msg     Decrypted message in place of original
         * @ret len     Updated to reflect encrypted length
         * @ret rc      Return status code
         *
         * The decrypted message is written over the encrypted one.
         */
        int ( * decrypt ) ( const void *kek, const void *iv, void *msg,
                            u16 *len );
};
 
#define WPA_KIES        __table ( struct wpa_kie, "wpa_kies" )
#define __wpa_kie       __table_entry ( WPA_KIES, 01 )
 
 
 
/**
 * @defgroup wpa_kde Key descriptor element types
 * @{
 */
 
/** Payload structure of the GTK-encapsulating KDE
 *
 * This does not include the IE type, length, or OUI bytes, which are
 * generic to all KDEs.
 */
struct wpa_kde_gtk_encap
{
        /** Key ID and TX bit */
        u8 id;
 
        /** Reserved byte */
        u8 _rsvd;
 
        /** Encapsulated group transient key */
        struct wpa_gtk gtk;
} __attribute__ (( packed ));
 
/** Mask for Key ID in wpa_kde_gtk::id field */
#define WPA_GTK_KID     0x03
 
/** Mask for Tx bit in wpa_kde_gtk::id field */
#define WPA_GTK_TXBIT   0x04
 
 
/** KDE type for an encapsulated Group Transient Key (requires encryption) */
#define WPA_KDE_GTK     _MKOUI ( 0x00, 0x0F, 0xAC, 0x01 )
 
/** KDE type for a MAC address */
#define WPA_KDE_MAC     _MKOUI ( 0x00, 0x0F, 0xAC, 0x03 )
 
/** KDE type for a PMKID */
#define WPA_KDE_PMKID   _MKOUI ( 0x00, 0x0F, 0xAC, 0x04 )
 
/** KDE type for a nonce */
#define WPA_KDE_NONCE   _MKOUI ( 0x00, 0x0F, 0xAC, 0x06 )
 
/** KDE type for a lifetime value */
#define WPA_KDE_LIFETIME _MKOUI ( 0x00, 0x0F, 0xAC, 0x07 )
 
 
/** Any key descriptor element type
 *
 * KDEs follow the 802.11 information element format of a type byte
 * (in this case "vendor-specific", with the requisite OUI+subtype
 * after length) and a length byte whose value does not include the
 * length of the type and length bytes.
 */
struct wpa_kde
{
        /** Information element type: always 0xDD (IEEE80211_IE_VENDOR) */
        u8 ie_type;
 
        /** Length, not including ie_type and length fields */
        u8 len;
 
        /** OUI + type byte */
        u32 oui_type;
 
        /** Payload data */
        union {
                /** For GTK-type KDEs, encapsulated GTK */
                struct wpa_kde_gtk_encap gtk_encap;
 
                /** For MAC-type KDEs, the MAC address */
                u8 mac[ETH_ALEN];
 
                /** For PMKID-type KDEs, the PMKID */
                u8 pmkid[WPA_PMKID_LEN];
 
                /** For Nonce-type KDEs, the nonce */
                u8 nonce[WPA_NONCE_LEN];
 
                /** For Lifetime-type KDEs, the lifetime in seconds
                 *
                 * This is in network byte order!
                 */
                u32 lifetime;
        };
} __attribute__ (( packed ));
 
/** @} */
 
int wpa_make_rsn_ie ( struct net80211_device *dev, union ieee80211_ie **ie );
int wpa_start ( struct net80211_device *dev, struct wpa_common_ctx *ctx,
                const void *pmk, size_t pmk_len );
void wpa_stop ( struct net80211_device *dev );
 
#endif /* _IPXE_WPA_H */