1 files changed, 139 insertions, 0 deletions
diff --git a/src/ap/comeback_token.c b/src/ap/comeback_token.c
new file mode 100644
index 00000000..8d9f21b1
--- /dev/null
+++ b/src/ap/comeback_token.c
@@ -0,0 +1,139 @@
+/*
+ * 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) */