/*

 * hostapd / Comeback token mechanism for SAE

 * Copyright (c) 2002-2017, Jouni Malinen <j@w1.fi>

 *

 * This software may be distributed under the terms of the BSD license.

 * See README for more details.

 */

#include "utils/includes.h"

#include "utils/common.h"

#include "hostapd.h"

#include "crypto/sha256.h"

#include "crypto/random.h"

#include "common/ieee802_11_defs.h"

#include "comeback_token.h"

#if defined(CONFIG_SAE) || defined(CONFIG_PASN)

static int comeback_token_hash(const u8 *comeback_key, const u8 *addr, u8 *idx)

{

  u8 hash[SHA256_MAC_LEN];

  if (hmac_sha256(comeback_key, COMEBACK_KEY_SIZE,

      addr, ETH_ALEN, hash) < 0)

    return -1;

  *idx = hash[0];

  return 0;

}

int check_comeback_token(const u8 *comeback_key,

       u16 *comeback_pending_idx, const u8 *addr,

       const u8 *token, size_t token_len)

{

  u8 mac[SHA256_MAC_LEN];

  const u8 *addrs[2];

  size_t len[2];

  u16 token_idx;

  u8 idx;

  if (token_len != SHA256_MAC_LEN ||

      comeback_token_hash(comeback_key, addr, &idx) < 0)

    return -1;

  token_idx = comeback_pending_idx[idx];

  if (token_idx == 0 || token_idx != WPA_GET_BE16(token)) {

    wpa_printf(MSG_DEBUG,

         "Comeback: Invalid anti-clogging token from "

         MACSTR " - token_idx 0x%04x, expected 0x%04x",

         MAC2STR(addr), WPA_GET_BE16(token), token_idx);

    return -1;

  }

  addrs[0] = addr;

  len[0] = ETH_ALEN;

  addrs[1] = token;

  len[1] = 2;

  if (hmac_sha256_vector(comeback_key, COMEBACK_KEY_SIZE,

             2, addrs, len, mac) < 0 ||

      os_memcmp_const(token + 2, &mac[2], SHA256_MAC_LEN - 2) != 0)

    return -1;

  comeback_pending_idx[idx] = 0; /* invalidate used token */

  return 0;

}

struct wpabuf *

auth_build_token_req(struct os_reltime *last_comeback_key_update,

         u8 *comeback_key, u16 comeback_idx,

         u16 *comeback_pending_idx, size_t idx_len,

         int group, const u8 *addr, int h2e)

{

  struct wpabuf *buf;

  u8 *token;

  struct os_reltime now;

  u8 idx[2];

  const u8 *addrs[2];

  size_t len[2];

  u8 p_idx;

  u16 token_idx;

  os_get_reltime(&now);

  if (!os_reltime_initialized(last_comeback_key_update) ||

      os_reltime_expired(&now, last_comeback_key_update, 60) ||

      comeback_idx == 0xffff) {

    if (random_get_bytes(comeback_key, COMEBACK_KEY_SIZE) < 0)

      return NULL;

    wpa_hexdump(MSG_DEBUG, "Comeback: Updated token key",

          comeback_key, COMEBACK_KEY_SIZE);

    *last_comeback_key_update = now;

    comeback_idx = 0;

    os_memset(comeback_pending_idx, 0, idx_len);

  }

  buf = wpabuf_alloc(sizeof(le16) + 3 + SHA256_MAC_LEN);

  if (buf == NULL)

    return NULL;

  if (group)

    wpabuf_put_le16(buf, group); /* Finite Cyclic Group */

  if (h2e) {

    /* Encapsulate Anti-clogging Token field in a container IE */

    wpabuf_put_u8(buf, WLAN_EID_EXTENSION);

    wpabuf_put_u8(buf, 1 + SHA256_MAC_LEN);

    wpabuf_put_u8(buf, WLAN_EID_EXT_ANTI_CLOGGING_TOKEN);

  }

  if (comeback_token_hash(comeback_key, addr, &p_idx) < 0) {

    wpabuf_free(buf);

    return NULL;

  }

  token_idx = comeback_pending_idx[p_idx];

  if (!token_idx) {

    comeback_idx++;

    token_idx = comeback_idx;

    comeback_pending_idx[p_idx] = token_idx;

  }

  WPA_PUT_BE16(idx, token_idx);

  token = wpabuf_put(buf, SHA256_MAC_LEN);

  addrs[0] = addr;

  len[0] = ETH_ALEN;

  addrs[1] = idx;

  len[1] = sizeof(idx);

  if (hmac_sha256_vector(comeback_key, COMEBACK_KEY_SIZE,

             2, addrs, len, token) < 0) {

    wpabuf_free(buf);

    return NULL;

  }

  WPA_PUT_BE16(token, token_idx);

  return buf;

}

#endif /* defined(CONFIG_SAE) || defined(CONFIG_PASN) */