security.c

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/*
 * Wireless USB Host Controller
 * Security support: encryption enablement, etc
 *
 * Copyright (C) 2006 Intel Corporation
 * Inaky Perez-Gonzalez <[email protected]>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation.
 *
 * 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.
 *
 *
 * FIXME: docs
 */
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/usb/ch9.h>
#include <linux/random.h>
#include <linux/export.h>
#include "wusbhc.h"

static void wusbhc_set_gtk_callback(struct urb *urb);
static void wusbhc_gtk_rekey_done_work(struct work_struct *work);

int wusbhc_sec_create(struct wusbhc *wusbhc)
{
    wusbhc->gtk.descr.bLength = sizeof(wusbhc->gtk.descr) + sizeof(wusbhc->gtk.data);
    wusbhc->gtk.descr.bDescriptorType = USB_DT_KEY;
    wusbhc->gtk.descr.bReserved = 0;

    wusbhc->gtk_index = wusb_key_index(0, WUSB_KEY_INDEX_TYPE_GTK,
                       WUSB_KEY_INDEX_ORIGINATOR_HOST);

    INIT_WORK(&wusbhc->gtk_rekey_done_work, wusbhc_gtk_rekey_done_work);

    return 0;
}


/* Called when the HC is destroyed */
void wusbhc_sec_destroy(struct wusbhc *wusbhc)
{
}


static u32 wusbhc_next_tkid(struct wusbhc *wusbhc, struct wusb_dev *wusb_dev)
{
    u32 *tkid;
    u32 addr;

    if (wusb_dev == NULL) {
        tkid = &wusbhc->gtk_tkid;
        addr = 0;
    } else {
        tkid = &wusb_port_by_idx(wusbhc, wusb_dev->port_idx)->ptk_tkid;
        addr = wusb_dev->addr & 0x7f;
    }

    *tkid = (addr << 8) | ((*tkid + 1) & 0xff);

    return *tkid;
}

static void wusbhc_generate_gtk(struct wusbhc *wusbhc)
{
    const size_t key_size = sizeof(wusbhc->gtk.data);
    u32 tkid;

    tkid = wusbhc_next_tkid(wusbhc, NULL);

    wusbhc->gtk.descr.tTKID[0] = (tkid >>  0) & 0xff;
    wusbhc->gtk.descr.tTKID[1] = (tkid >>  8) & 0xff;
    wusbhc->gtk.descr.tTKID[2] = (tkid >> 16) & 0xff;

    get_random_bytes(wusbhc->gtk.descr.bKeyData, key_size);
}

int wusbhc_sec_start(struct wusbhc *wusbhc)
{
    const size_t key_size = sizeof(wusbhc->gtk.data);
    int result;

    wusbhc_generate_gtk(wusbhc);

    result = wusbhc->set_gtk(wusbhc, wusbhc->gtk_tkid,
                 &wusbhc->gtk.descr.bKeyData, key_size);
    if (result < 0)
        dev_err(wusbhc->dev, "cannot set GTK for the host: %d\n",
            result);

    return result;
}

void wusbhc_sec_stop(struct wusbhc *wusbhc)
{
    cancel_work_sync(&wusbhc->gtk_rekey_done_work);
}


const char *wusb_et_name(u8 x)
{
    switch (x) {
    case USB_ENC_TYPE_UNSECURE: return "unsecure";
    case USB_ENC_TYPE_WIRED:    return "wired";
    case USB_ENC_TYPE_CCM_1:    return "CCM-1";
    case USB_ENC_TYPE_RSA_1:    return "RSA-1";
    default:            return "unknown";
    }
}
EXPORT_SYMBOL_GPL(wusb_et_name);

/*
 * Set the device encryption method
 *
 * We tell the device which encryption method to use; we do this when
 * setting up the device's security.
 */
static int wusb_dev_set_encryption(struct usb_device *usb_dev, int value)
{
    int result;
    struct device *dev = &usb_dev->dev;
    struct wusb_dev *wusb_dev = usb_dev->wusb_dev;

    if (value) {
        value = wusb_dev->ccm1_etd.bEncryptionValue;
    } else {
        /* FIXME: should be wusb_dev->etd[UNSECURE].bEncryptionValue */
        value = 0;
    }
    /* Set device's */
    result = usb_control_msg(usb_dev, usb_sndctrlpipe(usb_dev, 0),
            USB_REQ_SET_ENCRYPTION,
            USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
            value, 0, NULL, 0, 1000 /* FIXME: arbitrary */);
    if (result < 0)
        dev_err(dev, "Can't set device's WUSB encryption to "
            "%s (value %d): %d\n",
            wusb_et_name(wusb_dev->ccm1_etd.bEncryptionType),
            wusb_dev->ccm1_etd.bEncryptionValue,  result);
    return result;
}

/*
 * Set the GTK to be used by a device.
 *
 * The device must be authenticated.
 */
static int wusb_dev_set_gtk(struct wusbhc *wusbhc, struct wusb_dev *wusb_dev)
{
    struct usb_device *usb_dev = wusb_dev->usb_dev;

    return usb_control_msg(
        usb_dev, usb_sndctrlpipe(usb_dev, 0),
        USB_REQ_SET_DESCRIPTOR,
        USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
        USB_DT_KEY << 8 | wusbhc->gtk_index, 0,
        &wusbhc->gtk.descr, wusbhc->gtk.descr.bLength,
        1000);
}


/* FIXME: prototype for adding security */
int wusb_dev_sec_add(struct wusbhc *wusbhc,
             struct usb_device *usb_dev, struct wusb_dev *wusb_dev)
{
    int result, bytes, secd_size;
    struct device *dev = &usb_dev->dev;
    struct usb_security_descriptor *secd, *new_secd;
    const struct usb_encryption_descriptor *etd, *ccm1_etd = NULL;
    const void *itr, *top;
    char buf[64];

    secd = kmalloc(sizeof(*secd), GFP_KERNEL);
    if (secd == NULL) {
        result = -ENOMEM;
        goto out;
    }

    result = usb_get_descriptor(usb_dev, USB_DT_SECURITY,
                    0, secd, sizeof(*secd));
    if (result < sizeof(*secd)) {
        dev_err(dev, "Can't read security descriptor or "
            "not enough data: %d\n", result);
        goto out;
    }
    secd_size = le16_to_cpu(secd->wTotalLength);
    new_secd = krealloc(secd, secd_size, GFP_KERNEL);
    if (new_secd == NULL) {
        dev_err(dev, "Can't allocate space for security descriptors\n");
        goto out;
    }
    secd = new_secd;
    result = usb_get_descriptor(usb_dev, USB_DT_SECURITY,
                    0, secd, secd_size);
    if (result < secd_size) {
        dev_err(dev, "Can't read security descriptor or "
            "not enough data: %d\n", result);
        goto out;
    }
    bytes = 0;
    itr = &secd[1];
    top = (void *)secd + result;
    while (itr < top) {
        etd = itr;
        if (top - itr < sizeof(*etd)) {
            dev_err(dev, "BUG: bad device security descriptor; "
                "not enough data (%zu vs %zu bytes left)\n",
                top - itr, sizeof(*etd));
            break;
        }
        if (etd->bLength < sizeof(*etd)) {
            dev_err(dev, "BUG: bad device encryption descriptor; "
                "descriptor is too short "
                "(%u vs %zu needed)\n",
                etd->bLength, sizeof(*etd));
            break;
        }
        itr += etd->bLength;
        bytes += snprintf(buf + bytes, sizeof(buf) - bytes,
                  "%s (0x%02x/%02x) ",
                  wusb_et_name(etd->bEncryptionType),
                  etd->bEncryptionValue, etd->bAuthKeyIndex);
        if (etd->bEncryptionType == USB_ENC_TYPE_CCM_1)
            ccm1_etd = etd;
    }
    /* This code only supports CCM1 as of now. */
    /* FIXME: user has to choose which sec mode to use?
     * In theory we want CCM */
    if (ccm1_etd == NULL) {
        dev_err(dev, "WUSB device doesn't support CCM1 encryption, "
            "can't use!\n");
        result = -EINVAL;
        goto out;
    }
    wusb_dev->ccm1_etd = *ccm1_etd;
    dev_dbg(dev, "supported encryption: %s; using %s (0x%02x/%02x)\n",
        buf, wusb_et_name(ccm1_etd->bEncryptionType),
        ccm1_etd->bEncryptionValue, ccm1_etd->bAuthKeyIndex);
    result = 0;
out:
    kfree(secd);
    return result;
}

void wusb_dev_sec_rm(struct wusb_dev *wusb_dev)
{
    /* Nothing so far */
}

int wusb_dev_update_address(struct wusbhc *wusbhc, struct wusb_dev *wusb_dev)
{
    int result = -ENOMEM;
    struct usb_device *usb_dev = wusb_dev->usb_dev;
    struct device *dev = &usb_dev->dev;
    u8 new_address = wusb_dev->addr & 0x7F;

    /* Set address 0 */
    result = usb_control_msg(usb_dev, usb_sndctrlpipe(usb_dev, 0),
                 USB_REQ_SET_ADDRESS, 0,
                 0, 0, NULL, 0, 1000 /* FIXME: arbitrary */);
    if (result < 0) {
        dev_err(dev, "auth failed: can't set address 0: %d\n",
            result);
        goto error_addr0;
    }
    result = wusb_set_dev_addr(wusbhc, wusb_dev, 0);
    if (result < 0)
        goto error_addr0;
    usb_set_device_state(usb_dev, USB_STATE_DEFAULT);
    usb_ep0_reinit(usb_dev);

    /* Set new (authenticated) address. */
    result = usb_control_msg(usb_dev, usb_sndctrlpipe(usb_dev, 0),
                 USB_REQ_SET_ADDRESS, 0,
                 new_address, 0, NULL, 0,
                 1000 /* FIXME: arbitrary */);
    if (result < 0) {
        dev_err(dev, "auth failed: can't set address %u: %d\n",
            new_address, result);
        goto error_addr;
    }
    result = wusb_set_dev_addr(wusbhc, wusb_dev, new_address);
    if (result < 0)
        goto error_addr;
    usb_set_device_state(usb_dev, USB_STATE_ADDRESS);
    usb_ep0_reinit(usb_dev);
    usb_dev->authenticated = 1;
error_addr:
error_addr0:
    return result;
}

/*
 *
 *
 */
/* FIXME: split and cleanup */
int wusb_dev_4way_handshake(struct wusbhc *wusbhc, struct wusb_dev *wusb_dev,
                struct wusb_ckhdid *ck)
{
    int result = -ENOMEM;
    struct usb_device *usb_dev = wusb_dev->usb_dev;
    struct device *dev = &usb_dev->dev;
    u32 tkid;
    __le32 tkid_le;
    struct usb_handshake *hs;
    struct aes_ccm_nonce ccm_n;
    u8 mic[8];
    struct wusb_keydvt_in keydvt_in;
    struct wusb_keydvt_out keydvt_out;

    hs = kcalloc(3, sizeof(hs[0]), GFP_KERNEL);
    if (hs == NULL) {
        dev_err(dev, "can't allocate handshake data\n");
        goto error_kzalloc;
    }

    /* We need to turn encryption before beginning the 4way
     * hshake (WUSB1.0[.3.2.2]) */
    result = wusb_dev_set_encryption(usb_dev, 1);
    if (result < 0)
        goto error_dev_set_encryption;

    tkid = wusbhc_next_tkid(wusbhc, wusb_dev);
    tkid_le = cpu_to_le32(tkid);

    hs[0].bMessageNumber = 1;
    hs[0].bStatus = 0;
    memcpy(hs[0].tTKID, &tkid_le, sizeof(hs[0].tTKID));
    hs[0].bReserved = 0;
    memcpy(hs[0].CDID, &wusb_dev->cdid, sizeof(hs[0].CDID));
    get_random_bytes(&hs[0].nonce, sizeof(hs[0].nonce));
    memset(hs[0].MIC, 0, sizeof(hs[0].MIC));    /* Per WUSB1.0[T7-22] */

    result = usb_control_msg(
        usb_dev, usb_sndctrlpipe(usb_dev, 0),
        USB_REQ_SET_HANDSHAKE,
        USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
        1, 0, &hs[0], sizeof(hs[0]), 1000 /* FIXME: arbitrary */);
    if (result < 0) {
        dev_err(dev, "Handshake1: request failed: %d\n", result);
        goto error_hs1;
    }

    /* Handshake 2, from the device -- need to verify fields */
    result = usb_control_msg(
        usb_dev, usb_rcvctrlpipe(usb_dev, 0),
        USB_REQ_GET_HANDSHAKE,
        USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
        2, 0, &hs[1], sizeof(hs[1]), 1000 /* FIXME: arbitrary */);
    if (result < 0) {
        dev_err(dev, "Handshake2: request failed: %d\n", result);
        goto error_hs2;
    }

    result = -EINVAL;
    if (hs[1].bMessageNumber != 2) {
        dev_err(dev, "Handshake2 failed: bad message number %u\n",
            hs[1].bMessageNumber);
        goto error_hs2;
    }
    if (hs[1].bStatus != 0) {
        dev_err(dev, "Handshake2 failed: bad status %u\n",
            hs[1].bStatus);
        goto error_hs2;
    }
    if (memcmp(hs[0].tTKID, hs[1].tTKID, sizeof(hs[0].tTKID))) {
        dev_err(dev, "Handshake2 failed: TKID mismatch "
            "(#1 0x%02x%02x%02x vs #2 0x%02x%02x%02x)\n",
            hs[0].tTKID[0], hs[0].tTKID[1], hs[0].tTKID[2],
            hs[1].tTKID[0], hs[1].tTKID[1], hs[1].tTKID[2]);
        goto error_hs2;
    }
    if (memcmp(hs[0].CDID, hs[1].CDID, sizeof(hs[0].CDID))) {
        dev_err(dev, "Handshake2 failed: CDID mismatch\n");
        goto error_hs2;
    }

    /* Setup the CCM nonce */
    memset(&ccm_n.sfn, 0, sizeof(ccm_n.sfn));   /* Per WUSB1.0[6.5.2] */
    memcpy(ccm_n.tkid, &tkid_le, sizeof(ccm_n.tkid));
    ccm_n.src_addr = wusbhc->uwb_rc->uwb_dev.dev_addr;
    ccm_n.dest_addr.data[0] = wusb_dev->addr;
    ccm_n.dest_addr.data[1] = 0;

    /* Derive the KCK and PTK from CK, the CCM, H and D nonces */
    memcpy(keydvt_in.hnonce, hs[0].nonce, sizeof(keydvt_in.hnonce));
    memcpy(keydvt_in.dnonce, hs[1].nonce, sizeof(keydvt_in.dnonce));
    result = wusb_key_derive(&keydvt_out, ck->data, &ccm_n, &keydvt_in);
    if (result < 0) {
        dev_err(dev, "Handshake2 failed: cannot derive keys: %d\n",
            result);
        goto error_hs2;
    }

    /* Compute MIC and verify it */
    result = wusb_oob_mic(mic, keydvt_out.kck, &ccm_n, &hs[1]);
    if (result < 0) {
        dev_err(dev, "Handshake2 failed: cannot compute MIC: %d\n",
            result);
        goto error_hs2;
    }

    if (memcmp(hs[1].MIC, mic, sizeof(hs[1].MIC))) {
        dev_err(dev, "Handshake2 failed: MIC mismatch\n");
        goto error_hs2;
    }

    /* Send Handshake3 */
    hs[2].bMessageNumber = 3;
    hs[2].bStatus = 0;
    memcpy(hs[2].tTKID, &tkid_le, sizeof(hs[2].tTKID));
    hs[2].bReserved = 0;
    memcpy(hs[2].CDID, &wusb_dev->cdid, sizeof(hs[2].CDID));
    memcpy(hs[2].nonce, hs[0].nonce, sizeof(hs[2].nonce));
    result = wusb_oob_mic(hs[2].MIC, keydvt_out.kck, &ccm_n, &hs[2]);
    if (result < 0) {
        dev_err(dev, "Handshake3 failed: cannot compute MIC: %d\n",
            result);
        goto error_hs2;
    }

    result = usb_control_msg(
        usb_dev, usb_sndctrlpipe(usb_dev, 0),
        USB_REQ_SET_HANDSHAKE,
        USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
        3, 0, &hs[2], sizeof(hs[2]), 1000 /* FIXME: arbitrary */);
    if (result < 0) {
        dev_err(dev, "Handshake3: request failed: %d\n", result);
        goto error_hs3;
    }

    result = wusbhc->set_ptk(wusbhc, wusb_dev->port_idx, tkid,
                 keydvt_out.ptk, sizeof(keydvt_out.ptk));
    if (result < 0)
        goto error_wusbhc_set_ptk;

    result = wusb_dev_set_gtk(wusbhc, wusb_dev);
    if (result < 0) {
        dev_err(dev, "Set GTK for device: request failed: %d\n",
            result);
        goto error_wusbhc_set_gtk;
    }

    /* Update the device's address from unauth to auth */
    if (usb_dev->authenticated == 0) {
        result = wusb_dev_update_address(wusbhc, wusb_dev);
        if (result < 0)
            goto error_dev_update_address;
    }
    result = 0;
    dev_info(dev, "device authenticated\n");

error_dev_update_address:
error_wusbhc_set_gtk:
error_wusbhc_set_ptk:
error_hs3:
error_hs2:
error_hs1:
    memset(hs, 0, 3*sizeof(hs[0]));
    memset(&keydvt_out, 0, sizeof(keydvt_out));
    memset(&keydvt_in, 0, sizeof(keydvt_in));
    memset(&ccm_n, 0, sizeof(ccm_n));
    memset(mic, 0, sizeof(mic));
    if (result < 0)
        wusb_dev_set_encryption(usb_dev, 0);
error_dev_set_encryption:
    kfree(hs);
error_kzalloc:
    return result;
}

/*
 * Once all connected and authenticated devices have received the new
 * GTK, switch the host to using it.
 */
static void wusbhc_gtk_rekey_done_work(struct work_struct *work)
{
    struct wusbhc *wusbhc = container_of(work, struct wusbhc, gtk_rekey_done_work);
    size_t key_size = sizeof(wusbhc->gtk.data);

    mutex_lock(&wusbhc->mutex);

    if (--wusbhc->pending_set_gtks == 0)
        wusbhc->set_gtk(wusbhc, wusbhc->gtk_tkid, &wusbhc->gtk.descr.bKeyData, key_size);

    mutex_unlock(&wusbhc->mutex);
}

static void wusbhc_set_gtk_callback(struct urb *urb)
{
    struct wusbhc *wusbhc = urb->context;

    queue_work(wusbd, &wusbhc->gtk_rekey_done_work);
}

void wusbhc_gtk_rekey(struct wusbhc *wusbhc)
{
    static const size_t key_size = sizeof(wusbhc->gtk.data);
    int p;

    wusbhc_generate_gtk(wusbhc);

    for (p = 0; p < wusbhc->ports_max; p++) {
        struct wusb_dev *wusb_dev;

        wusb_dev = wusbhc->port[p].wusb_dev;
        if (!wusb_dev || !wusb_dev->usb_dev || !wusb_dev->usb_dev->authenticated)
            continue;

        usb_fill_control_urb(wusb_dev->set_gtk_urb, wusb_dev->usb_dev,
                     usb_sndctrlpipe(wusb_dev->usb_dev, 0),
                     (void *)wusb_dev->set_gtk_req,
                     &wusbhc->gtk.descr, wusbhc->gtk.descr.bLength,
                     wusbhc_set_gtk_callback, wusbhc);
        if (usb_submit_urb(wusb_dev->set_gtk_urb, GFP_KERNEL) == 0)
            wusbhc->pending_set_gtks++;
    }
    if (wusbhc->pending_set_gtks == 0)
        wusbhc->set_gtk(wusbhc, wusbhc->gtk_tkid, &wusbhc->gtk.descr.bKeyData, key_size);
}