SAE-PK: Extend SAE functionality for AP validation

This adds core SAE functionality for a new mode of using SAE with a
specially constructed password that contains a fingerprint for an AP
public key and that public key being used to validate an additional
signature in SAE confirm from the AP.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>

hostapd/Android.mk

@@ -250,6 +250,10 @@ endif
 ifdef CONFIG_SAE
 L_CFLAGS += -DCONFIG_SAE
 OBJS += src/common/sae.c
+ifdef CONFIG_SAE_PK
+L_CFLAGS += -DCONFIG_SAE_PK
+OBJS += src/common/sae_pk.c
+endif
 NEED_ECC=y
 NEED_DH_GROUPS=y
 NEED_HMAC_SHA256_KDF=y

hostapd/Makefile

@@ -294,6 +294,10 @@ endif
 ifdef CONFIG_SAE
 CFLAGS += -DCONFIG_SAE
 OBJS += ../src/common/sae.o
+ifdef CONFIG_SAE_PK
+CFLAGS += -DCONFIG_SAE_PK
+OBJS += ../src/common/sae_pk.o
+endif
 NEED_ECC=y
 NEED_DH_GROUPS=y
 NEED_HMAC_SHA256_KDF=y

src/ap/ieee802_11.c

@@ -515,7 +515,7 @@ static struct wpabuf * auth_build_sae_commit(struct hostapd_data *hapd,
 
 	if (update && use_pt &&
 	    sae_prepare_commit_pt(sta->sae, pt, hapd->own_addr, sta->addr,
-				  NULL) < 0)
+				  NULL, NULL) < 0)
 		return NULL;
 
 	if (update && !use_pt &&

src/common/sae.c

@@ -112,6 +112,9 @@ void sae_clear_temp_data(struct sae_data *sae)
 	wpabuf_free(tmp->own_rejected_groups);
 	wpabuf_free(tmp->peer_rejected_groups);
 	os_free(tmp->pw_id);
+#ifdef CONFIG_SAE_PK
+	bin_clear_free(tmp->pw, tmp->pw_len);
+#endif /* CONFIG_SAE_PK */
 	bin_clear_free(tmp, sizeof(*tmp));
 	sae->tmp = NULL;
 }
@@ -1052,10 +1055,17 @@ sae_derive_pt_group(int group, const u8 *ssid, size_t ssid_len,
 
 	wpa_printf(MSG_DEBUG, "SAE: Derive PT - group %d", group);
 
+	if (ssid_len > 32)
+		return NULL;
+
 	pt = os_zalloc(sizeof(*pt));
 	if (!pt)
 		return NULL;
 
+#ifdef CONFIG_SAE_PK
+	os_memcpy(pt->ssid, ssid, ssid_len);
+	pt->ssid_len = ssid_len;
+#endif /* CONFIG_SAE_PK */
 	pt->group = group;
 	pt->ec = crypto_ec_init(group);
 	if (pt->ec) {
@@ -1355,13 +1365,14 @@ int sae_prepare_commit(const u8 *addr1, const u8 *addr2,
 		return -1;
 
 	sae->tmp->h2e = 0;
+	sae->tmp->pk = 0;
 	return sae_derive_commit(sae);
 }
 
 
 int sae_prepare_commit_pt(struct sae_data *sae, const struct sae_pt *pt,
 			  const u8 *addr1, const u8 *addr2,
-			  int *rejected_groups)
+			  int *rejected_groups, const struct sae_pk *pk)
 {
 	if (!sae->tmp)
 		return -1;
@@ -1377,6 +1388,20 @@ int sae_prepare_commit_pt(struct sae_data *sae, const struct sae_pt *pt,
 		return -1;
 	}
 
+#ifdef CONFIG_SAE_PK
+	os_memcpy(sae->tmp->ssid, pt->ssid, pt->ssid_len);
+	sae->tmp->ssid_len = pt->ssid_len;
+	sae->tmp->ap_pk = pk;
+	/* TODO: Could support alternative groups as long as the combination
+	 * meets the requirements. */
+	if (pk && pk->group != sae->group) {
+		wpa_printf(MSG_DEBUG,
+			   "SAE-PK: Reject attempt to use group %d since K_AP use group %d",
+			   sae->group, pk->group);
+		sae->tmp->reject_group = true;
+		return -1;
+	}
+#endif /* CONFIG_SAE_PK */
 	sae->tmp->own_addr_higher = os_memcmp(addr1, addr2, ETH_ALEN) > 0;
 	wpabuf_free(sae->tmp->own_rejected_groups);
 	sae->tmp->own_rejected_groups = NULL;
@@ -1515,7 +1540,7 @@ static int sae_derive_keys(struct sae_data *sae, const u8 *k)
 	const u8 *salt;
 	struct wpabuf *rejected_groups = NULL;
 	u8 keyseed[SAE_MAX_HASH_LEN];
-	u8 keys[SAE_MAX_HASH_LEN + SAE_PMK_LEN];
+	u8 keys[2 * SAE_MAX_HASH_LEN + SAE_PMK_LEN];
 	struct crypto_bignum *tmp;
 	int ret = -1;
 	size_t hash_len, salt_len, prime_len = sae->tmp->prime_len;
@@ -1530,6 +1555,9 @@ static int sae_derive_keys(struct sae_data *sae, const u8 *k)
 	 * KCK || PMK = KDF-Hash-Length(keyseed, "SAE KCK and PMK",
 	 *                      (commit-scalar + peer-commit-scalar) modulo r)
 	 * PMKID = L((commit-scalar + peer-commit-scalar) modulo r, 0, 128)
+	 *
+	 * When SAE-PK is used,
+	 * KCK || PMK || KEK = KDF-Hash-Length(keyseed, "SAE-PK keys", context)
 	 */
 	if (!sae->tmp->h2e)
 		hash_len = SHA256_MAC_LEN;
@@ -1589,15 +1617,32 @@ static int sae_derive_keys(struct sae_data *sae, const u8 *k)
 	 * octets). */
 	crypto_bignum_to_bin(tmp, val, sizeof(val), sae->tmp->order_len);
 	wpa_hexdump(MSG_DEBUG, "SAE: PMKID", val, SAE_PMKID_LEN);
-	if (sae_kdf_hash(hash_len, keyseed, "SAE KCK and PMK",
+	if (!sae->tmp->pk &&
+	    sae_kdf_hash(hash_len, keyseed, "SAE KCK and PMK",
 			 val, sae->tmp->order_len,
 			 keys, hash_len + SAE_PMK_LEN) < 0)
 		goto fail;
+#ifdef CONFIG_SAE_PK
+	if (sae->tmp->pk &&
+	    sae_kdf_hash(hash_len, keyseed, "SAE-PK keys",
+			 val, sae->tmp->order_len,
+			 keys, 2 * hash_len + SAE_PMK_LEN) < 0)
+		goto fail;
+#endif /* CONFIG_SAE_PK */
 	forced_memzero(keyseed, sizeof(keyseed));
 	os_memcpy(sae->tmp->kck, keys, hash_len);
 	sae->tmp->kck_len = hash_len;
 	os_memcpy(sae->pmk, keys + hash_len, SAE_PMK_LEN);
 	os_memcpy(sae->pmkid, val, SAE_PMKID_LEN);
+#ifdef CONFIG_SAE_PK
+	if (sae->tmp->pk) {
+		os_memcpy(sae->tmp->kek, keys + hash_len + SAE_PMK_LEN,
+			  hash_len);
+		sae->tmp->kek_len = hash_len;
+		wpa_hexdump_key(MSG_DEBUG, "SAE: KEK for SAE-PK",
+				sae->tmp->kek, sae->tmp->kek_len);
+	}
+#endif /* CONFIG_SAE_PK */
 	forced_memzero(keys, sizeof(keys));
 	wpa_hexdump_key(MSG_DEBUG, "SAE: KCK",
 			sae->tmp->kck, sae->tmp->kck_len);
@@ -2189,13 +2234,14 @@ static int sae_cn_confirm_ffc(struct sae_data *sae, const u8 *sc,
 }
 
 
-void sae_write_confirm(struct sae_data *sae, struct wpabuf *buf)
+int sae_write_confirm(struct sae_data *sae, struct wpabuf *buf)
 {
 	const u8 *sc;
 	size_t hash_len;
+	int res;
 
 	if (sae->tmp == NULL)
-		return;
+		return -1;
 
 	hash_len = sae->tmp->kck_len;
 
@@ -2206,17 +2252,26 @@ void sae_write_confirm(struct sae_data *sae, struct wpabuf *buf)
 		sae->send_confirm++;
 
 	if (sae->tmp->ec)
-		sae_cn_confirm_ecc(sae, sc, sae->tmp->own_commit_scalar,
+		res = sae_cn_confirm_ecc(sae, sc, sae->tmp->own_commit_scalar,
 					 sae->tmp->own_commit_element_ecc,
 					 sae->peer_commit_scalar,
 					 sae->tmp->peer_commit_element_ecc,
 					 wpabuf_put(buf, hash_len));
 	else
-		sae_cn_confirm_ffc(sae, sc, sae->tmp->own_commit_scalar,
+		res = sae_cn_confirm_ffc(sae, sc, sae->tmp->own_commit_scalar,
 					 sae->tmp->own_commit_element_ffc,
 					 sae->peer_commit_scalar,
 					 sae->tmp->peer_commit_element_ffc,
 					 wpabuf_put(buf, hash_len));
+	if (res)
+		return res;
+
+#ifdef CONFIG_SAE_PK
+	if (sae_write_confirm_pk(sae, buf) < 0)
+		return -1;
+#endif /* CONFIG_SAE_PK */
+
+	return 0;
 }
 
 
@@ -2270,6 +2325,12 @@ int sae_check_confirm(struct sae_data *sae, const u8 *data, size_t len)
 		return -1;
 	}
 
+#ifdef CONFIG_SAE_PK
+	if (sae_check_confirm_pk(sae, data + 2 + hash_len,
+				 len - 2 - hash_len) < 0)
+		return -1;
+#endif /* CONFIG_SAE_PK */
+
 	return 0;
 }
 

src/common/sae.h

@@ -16,11 +16,24 @@
 #define SAE_MAX_ECC_PRIME_LEN 66
 #define SAE_MAX_HASH_LEN 64
 #define SAE_COMMIT_MAX_LEN (2 + 3 * SAE_MAX_PRIME_LEN + 255)
+#ifdef CONFIG_SAE_PK
+#define SAE_CONFIRM_MAX_LEN ((2 + SAE_MAX_HASH_LEN) + 1500)
+#else /* CONFIG_SAE_PK */
 #define SAE_CONFIRM_MAX_LEN (2 + SAE_MAX_HASH_LEN)
+#endif /* CONFIG_SAE_PK */
+#define SAE_PK_M_LEN 16
 
 /* Special value returned by sae_parse_commit() */
 #define SAE_SILENTLY_DISCARD 65535
 
+struct sae_pk {
+	struct wpabuf *m;
+	struct crypto_ec_key *key;
+	int group;
+	struct wpabuf *pubkey; /* DER encoded subjectPublicKey */
+};
+
+
 struct sae_temporary_data {
 	u8 kck[SAE_MAX_HASH_LEN];
 	size_t kck_len;
@@ -47,7 +60,22 @@ struct sae_temporary_data {
 	struct wpabuf *own_rejected_groups;
 	struct wpabuf *peer_rejected_groups;
 	unsigned int h2e:1;
+	unsigned int pk:1;
 	unsigned int own_addr_higher:1;
+
+#ifdef CONFIG_SAE_PK
+	u8 kek[SAE_MAX_HASH_LEN];
+	size_t kek_len;
+	const struct sae_pk *ap_pk;
+	u8 own_addr[ETH_ALEN];
+	u8 peer_addr[ETH_ALEN];
+	u8 *pw;
+	size_t pw_len;
+	size_t lambda;
+	u8 ssid[32];
+	size_t ssid_len;
+	bool reject_group;
+#endif /* CONFIG_SAE_PK */
 };
 
 struct sae_pt {
@@ -58,6 +86,10 @@ struct sae_pt {
 
 	const struct dh_group *dh;
 	struct crypto_bignum *ffc_pt;
+#ifdef CONFIG_SAE_PK
+	u8 ssid[32];
+	size_t ssid_len;
+#endif /* CONFIG_SAE_PK */
 };
 
 enum sae_state {
@@ -86,17 +118,19 @@ int sae_prepare_commit(const u8 *addr1, const u8 *addr2,
 		       const char *identifier, struct sae_data *sae);
 int sae_prepare_commit_pt(struct sae_data *sae, const struct sae_pt *pt,
 			  const u8 *addr1, const u8 *addr2,
-			  int *rejected_groups);
+			  int *rejected_groups, const struct sae_pk *pk);
 int sae_process_commit(struct sae_data *sae);
 int sae_write_commit(struct sae_data *sae, struct wpabuf *buf,
 		     const struct wpabuf *token, const char *identifier);
 u16 sae_parse_commit(struct sae_data *sae, const u8 *data, size_t len,
 		     const u8 **token, size_t *token_len, int *allowed_groups,
 		     int h2e);
-void sae_write_confirm(struct sae_data *sae, struct wpabuf *buf);
+int sae_write_confirm(struct sae_data *sae, struct wpabuf *buf);
 int sae_check_confirm(struct sae_data *sae, const u8 *data, size_t len);
 u16 sae_group_allowed(struct sae_data *sae, int *allowed_groups, u16 group);
 const char * sae_state_txt(enum sae_state state);
+size_t sae_ecc_prime_len_2_hash_len(size_t prime_len);
+size_t sae_ffc_prime_len_2_hash_len(size_t prime_len);
 struct sae_pt * sae_derive_pt(int *groups, const u8 *ssid, size_t ssid_len,
 			      const u8 *password, size_t password_len,
 			      const char *identifier);
@@ -108,4 +142,22 @@ sae_derive_pwe_from_pt_ffc(const struct sae_pt *pt,
 			   const u8 *addr1, const u8 *addr2);
 void sae_deinit_pt(struct sae_pt *pt);
 
+/* sae_pk.c */
+#ifdef CONFIG_SAE_PK
+bool sae_pk_valid_password(const char *pw);
+#else /* CONFIG_SAE_PK */
+static inline bool sae_pk_valid_password(const char *pw)
+{
+	return false;
+}
+#endif /* CONFIG_SAE_PK */
+char * sae_pk_base32_encode(const u8 *src, size_t len_bits);
+u8 * sae_pk_base32_decode(const char *src, size_t len, size_t *out_len);
+int sae_pk_set_password(struct sae_data *sae, const char *password);
+void sae_deinit_pk(struct sae_pk *pk);
+struct sae_pk * sae_parse_pk(const char *val);
+int sae_write_confirm_pk(struct sae_data *sae, struct wpabuf *buf);
+int sae_check_confirm_pk(struct sae_data *sae, const u8 *ies, size_t ies_len);
+int sae_hash(size_t hash_len, const u8 *data, size_t len, u8 *hash);
+
 #endif /* SAE_H */

src/common/sae_pk.c

@@ -0,0 +1,653 @@
+/*
+ * SAE-PK
+ * Copyright (c) 2020, The Linux Foundation
+ *
+ * This software may be distributed under the terms of the BSD license.
+ * See README for more details.
+ */
+
+#include "utils/includes.h"
+#include <stdint.h>
+
+#include "utils/common.h"
+#include "utils/base64.h"
+#include "common/ieee802_11_defs.h"
+#include "common/ieee802_11_common.h"
+#include "crypto/crypto.h"
+#include "crypto/aes.h"
+#include "crypto/aes_siv.h"
+#include "sae.h"
+
+
+/* RFC 4648 base 32 alphabet with lowercase characters */
+static const char *sae_pk_base32_table = "abcdefghijklmnopqrstuvwxyz234567";
+
+
+bool sae_pk_valid_password(const char *pw)
+{
+	int pos;
+
+	/* Minimum password length for SAE-PK is not defined, but the automatic
+	 * password style determination is more reliable if at least one hyphen
+	 * is forced to be present in the password. */
+	if (os_strlen(pw) < 6)
+		return false;
+
+	for (pos = 0; pw[pos]; pos++) {
+		if (pos && pos % 5 == 4) {
+			if (pw[pos] != '-')
+				return false;
+			continue;
+		}
+		if (!os_strchr(sae_pk_base32_table, pw[pos]))
+			return false;
+	}
+	if (pos == 0)
+		return false;
+	return pw[pos - 1] != '-';
+}
+
+
+static char * add_char(const char *start, char *pos, u8 idx, size_t *bits)
+{
+	if (*bits == 0)
+		return pos;
+	if (*bits > 5)
+		*bits -= 5;
+	else
+		*bits = 0;
+
+	if ((pos - start) % 5 == 4)
+		*pos++ = '-';
+	*pos++ = sae_pk_base32_table[idx];
+	return pos;
+}
+
+
+char * sae_pk_base32_encode(const u8 *src, size_t len_bits)
+{
+	char *out, *pos;
+	size_t olen, extra_pad, i;
+	u64 block = 0;
+	u8 val;
+	size_t len = (len_bits + 7) / 8;
+	size_t left = len_bits;
+	int j;
+
+	if (len == 0 || len >= SIZE_MAX / 8)
+		return NULL;
+	olen = len * 8 / 5 + 1;
+	olen += olen / 4; /* hyphen separators */
+	pos = out = os_zalloc(olen + 1);
+	if (!out)
+		return NULL;
+
+	extra_pad = (5 - len % 5) % 5;
+	for (i = 0; i < len + extra_pad; i++) {
+		val = i < len ? src[i] : 0;
+		block <<= 8;
+		block |= val;
+		if (i % 5 == 4) {
+			for (j = 7; j >= 0; j--)
+				pos = add_char(out, pos,
+					       (block >> j * 5) & 0x1f, &left);
+			block = 0;
+		}
+	}
+
+	return out;
+}
+
+
+u8 * sae_pk_base32_decode(const char *src, size_t len, size_t *out_len)
+{
+	u8 dtable[256], *out, *pos, tmp;
+	u64 block = 0;
+	size_t i, count, olen;
+	int pad = 0;
+	size_t extra_pad;
+
+	os_memset(dtable, 0x80, 256);
+	for (i = 0; sae_pk_base32_table[i]; i++)
+		dtable[(u8) sae_pk_base32_table[i]] = i;
+	dtable['='] = 0;
+
+	count = 0;
+	for (i = 0; i < len; i++) {
+		if (dtable[(u8) src[i]] != 0x80)
+			count++;
+	}
+
+	if (count == 0)
+		return NULL;
+	extra_pad = (8 - count % 8) % 8;
+
+	olen = (count + extra_pad) / 8 * 5;
+	pos = out = os_malloc(olen);
+	if (!out)
+		return NULL;
+
+	count = 0;
+	for (i = 0; i < len + extra_pad; i++) {
+		u8 val;
+
+		if (i >= len)
+			val = '=';
+		else
+			val = src[i];
+		tmp = dtable[val];
+		if (tmp == 0x80)
+			continue;
+
+		if (val == '=')
+			pad++;
+		block <<= 5;
+		block |= tmp;
+		count++;
+		if (count == 8) {
+			*pos++ = (block >> 32) & 0xff;
+			*pos++ = (block >> 24) & 0xff;
+			*pos++ = (block >> 16) & 0xff;
+			*pos++ = (block >> 8) & 0xff;
+			*pos++ = block & 0xff;
+			count = 0;
+			block = 0;
+			if (pad) {
+				/* Leave in all the available bits with zero
+				 * padding to full octets from right. */
+				pos -= pad * 5 / 8;
+				break;
+			}
+		}
+	}
+
+	*out_len = pos - out;
+	return out;
+}
+
+
+int sae_pk_set_password(struct sae_data *sae, const char *password)
+{
+	struct sae_temporary_data *tmp = sae->tmp;
+	size_t len;
+
+	len = os_strlen(password);
+	if (!tmp || len < 1)
+		return -1;
+
+	bin_clear_free(tmp->pw, tmp->pw_len);
+	tmp->pw = sae_pk_base32_decode(password, len, &tmp->pw_len);
+	tmp->lambda = len - len / 5;
+	return tmp->pw ? 0 : -1;
+}
+
+
+void sae_deinit_pk(struct sae_pk *pk)
+{
+	if (pk) {
+		wpabuf_free(pk->m);
+		crypto_ec_key_deinit(pk->key);
+		wpabuf_free(pk->pubkey);
+		os_free(pk);
+	}
+}
+
+
+struct sae_pk * sae_parse_pk(const char *val)
+{
+	struct sae_pk *pk;
+	const char *pos;
+	size_t len;
+	unsigned char *der;
+	size_t der_len;
+
+	/* <m-as-hexdump>:<base64-encoded-DER-encoded-key> */
+
+	pos = os_strchr(val, ':');
+	if (!pos || (pos - val) & 0x01)
+		return NULL;
+	len = (pos - val) / 2;
+	if (len != SAE_PK_M_LEN) {
+		wpa_printf(MSG_INFO, "SAE: Unexpected Modifier M length %zu",
+			   len);
+		return NULL;
+	}
+
+	pk = os_zalloc(sizeof(*pk));
+	if (!pk)
+		return NULL;
+	pk->m = wpabuf_alloc(len);
+	if (!pk->m || hexstr2bin(val, wpabuf_put(pk->m, len), len)) {
+		wpa_printf(MSG_INFO, "SAE: Failed to parse m");
+		goto fail;
+	}
+
+	pos++;
+	der = base64_decode(pos, os_strlen(pos), &der_len);
+	if (!der) {
+		wpa_printf(MSG_INFO, "SAE: Failed to base64 decode PK key");
+		goto fail;
+	}
+
+	pk->key = crypto_ec_key_parse_priv(der, der_len);
+	bin_clear_free(der, der_len);
+	if (!pk->key)
+		goto fail;
+	pk->group = crypto_ec_key_group(pk->key);
+	pk->pubkey = crypto_ec_key_get_subject_public_key(pk->key);
+	if (!pk->pubkey)
+		goto fail;
+
+	return pk;
+fail:
+	sae_deinit_pk(pk);
+	return NULL;
+}
+
+
+int sae_hash(size_t hash_len, const u8 *data, size_t len, u8 *hash)
+{
+	if (hash_len == 32)
+		return sha256_vector(1, &data, &len, hash);
+#ifdef CONFIG_SHA384
+	if (hash_len == 48)
+		return sha384_vector(1, &data, &len, hash);
+#endif /* CONFIG_SHA384 */
+#ifdef CONFIG_SHA512
+	if (hash_len == 64)
+		return sha512_vector(1, &data, &len, hash);
+#endif /* CONFIG_SHA512 */
+	return -1;
+}
+
+
+static int sae_pk_hash_sig_data(struct sae_data *sae, size_t hash_len,
+				bool ap, const u8 *m, size_t m_len,
+				const u8 *pubkey, size_t pubkey_len, u8 *hash)
+{
+	struct sae_temporary_data *tmp = sae->tmp;
+	struct wpabuf *sig_data;
+	u8 *pos;
+	int ret = -1;
+
+	/* Signed data for KeyAuth: eleAP || eleSTA || scaAP || scaSTA ||
+	 * M || K_AP || AP-BSSID || STA-MAC */
+	sig_data = wpabuf_alloc(tmp->prime_len * 6 + m_len + pubkey_len +
+				2 * ETH_ALEN);
+	if (!sig_data)
+		goto fail;
+	pos = wpabuf_put(sig_data, 2 * tmp->prime_len);
+	if (crypto_ec_point_to_bin(tmp->ec, ap ? tmp->own_commit_element_ecc :
+				   tmp->peer_commit_element_ecc,
+				   pos, pos + tmp->prime_len) < 0)
+		goto fail;
+	pos = wpabuf_put(sig_data, 2 * tmp->prime_len);
+	if (crypto_ec_point_to_bin(tmp->ec, ap ? tmp->peer_commit_element_ecc :
+				   tmp->own_commit_element_ecc,
+				   pos, pos + tmp->prime_len) < 0)
+		goto fail;
+	if (crypto_bignum_to_bin(ap ? tmp->own_commit_scalar :
+				 sae->peer_commit_scalar,
+				 wpabuf_put(sig_data, tmp->prime_len),
+				 tmp->prime_len, tmp->prime_len) < 0 ||
+	    crypto_bignum_to_bin(ap ? sae->peer_commit_scalar :
+				 tmp->own_commit_scalar,
+				 wpabuf_put(sig_data, tmp->prime_len),
+				 tmp->prime_len, tmp->prime_len) < 0)
+		goto fail;
+	wpabuf_put_data(sig_data, m, m_len);
+	wpabuf_put_data(sig_data, pubkey, pubkey_len);
+	wpabuf_put_data(sig_data, ap ? tmp->own_addr : tmp->peer_addr,
+			ETH_ALEN);
+	wpabuf_put_data(sig_data, ap ? tmp->peer_addr : tmp->own_addr,
+			ETH_ALEN);
+	wpa_hexdump_buf_key(MSG_DEBUG, "SAE-PK: Data to be signed for KeyAuth",
+			    sig_data);
+	if (sae_hash(hash_len, wpabuf_head(sig_data), wpabuf_len(sig_data),
+		     hash) < 0)
+		goto fail;
+	wpa_hexdump(MSG_DEBUG, "SAE-PK: hash(data to be signed)",
+		    hash, hash_len);
+	ret = 0;
+fail:
+	wpabuf_free(sig_data);
+	return ret;
+}
+
+
+int sae_write_confirm_pk(struct sae_data *sae, struct wpabuf *buf)
+{
+	struct sae_temporary_data *tmp = sae->tmp;
+	struct wpabuf *elem = NULL, *sig = NULL;
+	size_t extra;
+	int ret = -1;
+	u8 *encr_mod;
+	size_t encr_mod_len;
+	const struct sae_pk *pk;
+	u8 hash[SAE_MAX_HASH_LEN];
+	size_t hash_len;
+
+	if (!tmp)
+		return -1;
+
+	pk = tmp->ap_pk;
+	if (!pk)
+		return 0;
+
+	if (tmp->kek_len != 32 && tmp->kek_len != 48 && tmp->kek_len != 64) {
+		wpa_printf(MSG_INFO, "SAE-PK: No KEK available for confirm");
+		return -1;
+	}
+
+	if (!tmp->ec) {
+		/* Only ECC groups are supported for SAE-PK in the current
+		 * implementation. */
+		wpa_printf(MSG_INFO,
+			   "SAE-PK: SAE commit did not use an ECC group");
+		return -1;
+	}
+
+	hash_len = sae_ecc_prime_len_2_hash_len(tmp->prime_len);
+	if (sae_pk_hash_sig_data(sae, hash_len, true, wpabuf_head(pk->m),
+				 wpabuf_len(pk->m), wpabuf_head(pk->pubkey),
+				 wpabuf_len(pk->pubkey), hash) < 0)
+		goto fail;
+	sig = crypto_ec_key_sign(pk->key, hash, hash_len);
+	if (!sig)
+		goto fail;
+	wpa_hexdump_buf(MSG_DEBUG, "SAE-PK: KeyAuth = Sig_AP()", sig);
+
+	elem = wpabuf_alloc(1500 + wpabuf_len(sig));
+	if (!elem)
+		goto fail;
+
+	/* EncryptedModifier = AES-SIV-Q(M); no AAD */
+	encr_mod_len = wpabuf_len(pk->m) + AES_BLOCK_SIZE;
+	wpabuf_put_u8(elem, encr_mod_len);
+	encr_mod = wpabuf_put(elem, encr_mod_len);
+	if (aes_siv_encrypt(tmp->kek, tmp->kek_len,
+			    wpabuf_head(pk->m), wpabuf_len(pk->m),
+			    0, NULL, NULL, encr_mod) < 0)
+		goto fail;
+	wpa_hexdump(MSG_DEBUG, "SAE-PK: EncryptedModifier",
+		    encr_mod, encr_mod_len);
+
+	/* FILS Public Key element */
+	wpabuf_put_u8(elem, WLAN_EID_EXTENSION);
+	wpabuf_put_u8(elem, 2 + wpabuf_len(pk->pubkey));
+	wpabuf_put_u8(elem, WLAN_EID_EXT_FILS_PUBLIC_KEY);
+	wpabuf_put_u8(elem, 3); /* Key Type: ECDSA public key */
+	wpabuf_put_buf(elem, pk->pubkey);
+
+	/* FILS Key Confirmation element (KeyAuth) */
+	wpabuf_put_u8(elem, WLAN_EID_EXTENSION);
+	wpabuf_put_u8(elem, 1 + wpabuf_len(sig));
+	wpabuf_put_u8(elem, WLAN_EID_EXT_FILS_KEY_CONFIRM);
+	/* KeyAuth = Sig_AP(eleAP || eleSTA || scaAP || scaSTA || M || K_AP ||
+	 *                  AP-BSSID || STA-MAC) */
+	wpabuf_put_buf(elem, sig);
+
+	/* TODO: fragmentation */
+	extra = 6; /* Vendor specific element header */
+
+	if (wpabuf_tailroom(elem) < extra + wpabuf_len(buf)) {
+		wpa_printf(MSG_INFO,
+			   "SAE-PK: No room in message buffer for SAE-PK element (%zu < %zu)",
+			   wpabuf_tailroom(buf), extra + wpabuf_len(buf));
+		goto fail;
+	}
+
+	/* SAE-PK element */
+	wpabuf_put_u8(buf, WLAN_EID_VENDOR_SPECIFIC);
+	wpabuf_put_u8(buf, 4 + wpabuf_len(elem));
+	wpabuf_put_be32(buf, SAE_PK_IE_VENDOR_TYPE);
+	wpabuf_put_buf(buf, elem);
+
+	ret = 0;
+fail:
+	wpabuf_free(elem);
+	wpabuf_free(sig);
+	return ret;
+
+}
+
+
+static bool sae_pk_valid_fingerprint(struct sae_data *sae,
+				     const u8 *m, size_t m_len,
+				     const u8 *k_ap, size_t k_ap_len)
+{
+	struct sae_temporary_data *tmp = sae->tmp;
+	size_t sec, i;
+	u8 *fingerprint_exp, *hash_data, *pos;
+	size_t hash_len, hash_data_len, fingerprint_bits, fingerprint_bytes;
+	u8 hash[SAE_MAX_HASH_LEN];
+	int res;
+
+	if (!tmp->pw || tmp->pw_len < 1) {
+		wpa_printf(MSG_DEBUG,
+			   "SAE-PK: No PW available for K_AP fingerprint check");
+		return false;
+	}
+
+	/* Fingerprint = L(Hash(SSID || M || K_AP), 0, 8*Sec + 5*Lambda - 2) */
+
+	hash_len = sae_ecc_prime_len_2_hash_len(tmp->prime_len);
+	hash_data_len = tmp->ssid_len + m_len + k_ap_len;
+	hash_data = os_malloc(hash_data_len);
+	if (!hash_data)
+		return false;
+	pos = hash_data;
+	os_memcpy(pos, tmp->ssid, tmp->ssid_len);
+	pos += tmp->ssid_len;
+	os_memcpy(pos, m, m_len);
+	pos += m_len;
+	os_memcpy(pos, k_ap, k_ap_len);
+
+	wpa_hexdump_key(MSG_DEBUG, "SAE-PK: SSID || M || K_AP",
+			hash_data, hash_data_len);
+	res = sae_hash(hash_len, hash_data, hash_data_len, hash);
+	bin_clear_free(hash_data, hash_data_len);
+	if (res < 0)
+		return false;
+	wpa_hexdump(MSG_DEBUG, "SAE-PK: Hash(SSID || M || K_AP)",
+		    hash, hash_len);
+
+	wpa_hexdump_key(MSG_DEBUG, "SAE-PK: PW", tmp->pw, tmp->pw_len);
+	sec = (tmp->pw[0] >> 6) + 2;
+	fingerprint_bits = 8 * sec + 5 * tmp->lambda - 2;
+	wpa_printf(MSG_DEBUG, "SAE-PK: Sec=%zu Lambda=%zu fingerprint_bits=%zu",
+		   sec, tmp->lambda, fingerprint_bits);
+	if (fingerprint_bits > hash_len * 8) {
+		wpa_printf(MSG_INFO,
+			   "SAE-PK: Not enough hash output bits for the fingerprint");
+		return false;
+	}
+	fingerprint_bytes = (fingerprint_bits + 7) / 8;
+	if (fingerprint_bits % 8) {
+		size_t extra;
+
+		/* Zero out the extra bits in the last octet */
+		extra = 8 - fingerprint_bits % 8;
+		pos = &hash[fingerprint_bits / 8];
+		*pos = (*pos >> extra) << extra;
+	}
+	wpa_hexdump(MSG_DEBUG, "SAE-PK: Fingerprint", hash, fingerprint_bytes);
+
+	fingerprint_exp = os_zalloc(sec + tmp->pw_len);
+	if (!fingerprint_exp)
+		return false;
+	pos = fingerprint_exp + sec;
+	for (i = 0; i < tmp->pw_len; i++) {
+		u8 next = i + 1 < tmp->pw_len ? tmp->pw[i + 1] : 0;
+
+		*pos++ = tmp->pw[i] << 2 | next >> 6;
+	}
+
+	wpa_hexdump(MSG_DEBUG, "SAE-PK: Fingerprint_Expected",
+		    fingerprint_exp, fingerprint_bytes);
+	res = os_memcmp_const(hash, fingerprint_exp, fingerprint_bytes);
+	bin_clear_free(fingerprint_exp, tmp->pw_len);
+
+	if (res) {
+		wpa_printf(MSG_DEBUG, "SAE-PK: K_AP fingerprint mismatch");
+		return false;
+	}
+
+	wpa_printf(MSG_DEBUG, "SAE-PK: Valid K_AP fingerprint");
+	return true;
+}
+
+
+int sae_check_confirm_pk(struct sae_data *sae, const u8 *ies, size_t ies_len)
+{
+	struct sae_temporary_data *tmp = sae->tmp;
+	const u8 *sae_pk, *pos, *end, *encr_mod, *k_ap, *key_auth;
+	u8 m[SAE_PK_M_LEN];
+	size_t k_ap_len, key_auth_len;
+	struct crypto_ec_key *key;
+	int res;
+	u8 hash[SAE_MAX_HASH_LEN];
+	size_t hash_len;
+	int group;
+
+	if (!tmp)
+		return -1;
+	if (!tmp->pk || tmp->ap_pk)
+		return 0;
+
+	if (tmp->kek_len != 32 && tmp->kek_len != 48 && tmp->kek_len != 64) {
+		wpa_printf(MSG_INFO, "SAE-PK: No KEK available for confirm");
+		return -1;
+	}
+
+	if (!tmp->ec) {
+		/* Only ECC groups are supported for SAE-PK in the current
+		 * implementation. */
+		wpa_printf(MSG_INFO,
+			   "SAE-PK: SAE commit did not use an ECC group");
+		return -1;
+	}
+
+	wpa_hexdump(MSG_DEBUG, "SAE-PK: Received confirm IEs", ies, ies_len);
+	sae_pk = get_vendor_ie(ies, ies_len, SAE_PK_IE_VENDOR_TYPE);
+	if (!sae_pk) {
+		wpa_printf(MSG_INFO, "SAE-PK: No SAE-PK element included");
+		return -1;
+	}
+	/* TODO: Fragment reassembly */
+	pos = sae_pk + 2;
+	end = pos + sae_pk[1];
+
+	if (end - pos < 4 + 1 + SAE_PK_M_LEN + AES_BLOCK_SIZE) {
+		wpa_printf(MSG_INFO,
+			   "SAE-PK: No room for EncryptedModifier in SAE-PK element");
+		return -1;
+	}
+	pos += 4;
+	if (*pos != SAE_PK_M_LEN + AES_BLOCK_SIZE) {
+		wpa_printf(MSG_INFO,
+			   "SAE-PK: Unexpected EncryptedModifier length %u",
+			   *pos);
+		return -1;
+	}
+	pos++;
+	encr_mod = pos;
+	pos += SAE_PK_M_LEN + AES_BLOCK_SIZE;
+
+	if (end - pos < 4 || pos[0] != WLAN_EID_EXTENSION || pos[1] < 2 ||
+	    pos[1] > end - pos - 2 ||
+	    pos[2] != WLAN_EID_EXT_FILS_PUBLIC_KEY) {
+		wpa_printf(MSG_INFO,
+			   "SAE-PK: No FILS Public Key element in SAE-PK element");
+		return -1;
+	}
+	if (pos[3] != 3) {
+		wpa_printf(MSG_INFO, "SAE-PK: Unsupported public key type %u",
+			   pos[3]);
+		return -1;
+	}
+	k_ap_len = pos[1] - 2;
+	pos += 4;
+	k_ap = pos;
+	pos += k_ap_len;
+
+	if (end - pos < 4 || pos[0] != WLAN_EID_EXTENSION || pos[1] < 1 ||
+	    pos[1] > end - pos - 2 ||
+	    pos[2] != WLAN_EID_EXT_FILS_KEY_CONFIRM) {
+		wpa_printf(MSG_INFO,
+			   "SAE-PK: No FILS Key Confirm element in SAE-PK element");
+		return -1;
+	}
+	key_auth_len = pos[1] - 1;
+	pos += 3;
+	key_auth = pos;
+	pos += key_auth_len;
+
+	if (pos < end) {
+		wpa_hexdump(MSG_DEBUG,
+			    "SAE-PK: Extra data at the end of SAE-PK element",
+			    pos, end - pos);
+	}
+
+	wpa_hexdump(MSG_DEBUG, "SAE-PK: EncryptedModifier",
+		    encr_mod, SAE_PK_M_LEN + AES_BLOCK_SIZE);
+
+	if (aes_siv_decrypt(tmp->kek, tmp->kek_len,
+			    encr_mod, SAE_PK_M_LEN + AES_BLOCK_SIZE,
+			    0, NULL, NULL, m) < 0) {
+		wpa_printf(MSG_INFO,
+			   "SAE-PK: Failed to decrypt EncryptedModifier");
+		return -1;
+	}
+	wpa_hexdump_key(MSG_DEBUG, "SAE-PK: Modifier M", m, SAE_PK_M_LEN);
+
+	wpa_hexdump(MSG_DEBUG, "SAE-PK: Received K_AP", k_ap, k_ap_len);
+	/* TODO: Check against the public key, if one is stored in the network
+	 * profile */
+
+	if (!sae_pk_valid_fingerprint(sae, m, SAE_PK_M_LEN, k_ap, k_ap_len))
+		return -1;
+
+	key = crypto_ec_key_parse_pub(k_ap, k_ap_len);
+	if (!key) {
+		wpa_printf(MSG_INFO, "SAE-PK: Failed to parse K_AP");
+		return -1;
+	}
+
+	group = crypto_ec_key_group(key);
+	/* TODO: Could support alternative groups as long as the combination
+	 * meets the requirements. */
+	if (group != sae->group) {
+		wpa_printf(MSG_INFO,
+			   "SAE-PK: K_AP group %d does not match SAE group %d",
+			   group, sae->group);
+		crypto_ec_key_deinit(key);
+		return -1;
+	}
+
+	wpa_hexdump(MSG_DEBUG, "SAE-PK: Received KeyAuth",
+		    key_auth, key_auth_len);
+
+	hash_len = sae_ecc_prime_len_2_hash_len(tmp->prime_len);
+	if (sae_pk_hash_sig_data(sae, hash_len, false, m, SAE_PK_M_LEN,
+				 k_ap, k_ap_len, hash) < 0) {
+		crypto_ec_key_deinit(key);
+		return -1;
+	}
+
+	res = crypto_ec_key_verify_signature(key, hash, hash_len,
+					     key_auth, key_auth_len);
+	crypto_ec_key_deinit(key);
+
+	if (res != 1) {
+		wpa_printf(MSG_INFO,
+			   "SAE-PK: Invalid or incorrect signature in KeyAuth");
+		return -1;
+	}
+
+	wpa_printf(MSG_DEBUG, "SAE-PK: Valid KeyAuth signature received");
+
+	/* TODO: Store validated public key into network profile */
+
+	return 0;
+}

wpa_supplicant/Android.mk

@@ -235,6 +235,10 @@ endif
 ifdef CONFIG_SAE
 L_CFLAGS += -DCONFIG_SAE
 OBJS += src/common/sae.c
+ifdef CONFIG_SAE_PK
+L_CFLAGS += -DCONFIG_SAE_PK
+OBJS += src/common/sae_pk.c
+endif
 NEED_ECC=y
 NEED_DH_GROUPS=y
 NEED_HMAC_SHA256_KDF=y

wpa_supplicant/Makefile

@@ -267,6 +267,10 @@ endif
 ifdef CONFIG_SAE
 CFLAGS += -DCONFIG_SAE
 OBJS += ../src/common/sae.o
+ifdef CONFIG_SAE_PK
+CFLAGS += -DCONFIG_SAE_PK
+OBJS += ../src/common/sae_pk.o
+endif
 NEED_ECC=y
 NEED_DH_GROUPS=y
 NEED_HMAC_SHA256_KDF=y

wpa_supplicant/sme.c

@@ -157,7 +157,7 @@ static struct wpabuf * sme_auth_build_sae_commit(struct wpa_supplicant *wpa_s,
 	if (use_pt &&
 	    sae_prepare_commit_pt(&wpa_s->sme.sae, ssid->pt,
 				  wpa_s->own_addr, bssid,
-				  wpa_s->sme.sae_rejected_groups) < 0)
+				  wpa_s->sme.sae_rejected_groups, NULL) < 0)
 		return NULL;
 	if (!use_pt &&
 	    sae_prepare_commit(wpa_s->own_addr, bssid,