From 3f1639da5728073572df25c0741f8266e9a6b15d Mon Sep 17 00:00:00 2001
From: Jouni Malinen <jouni@qca.qualcomm.com>
Date: Tue, 30 Apr 2013 18:17:23 +0300
Subject: [PATCH] WPS NFC: Split DH key generation to a separate function

This allows DH key generation to be shared for other purposes than just
the case of OOB Device Password building. In addition, force the DH
public key buffer to be full 192 octets with zero padding to avoid
issues with the buffer being used in messages sent to a peer device.

Signed-hostap: Jouni Malinen <jouni@qca.qualcomm.com>
---
 src/wps/wps.h        |  1 +
 src/wps/wps_common.c | 36 +++++++++++++++++++++++++++---------
 2 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/src/wps/wps.h b/src/wps/wps.h
index 66242ca43..220f4a83e 100644
--- a/src/wps/wps.h
+++ b/src/wps/wps.h
@@ -856,6 +856,7 @@ struct wpabuf * wps_build_nfc_pw_token(u16 dev_pw_id,
 				       const struct wpabuf *dev_pw);
 struct wpabuf * wps_nfc_token_build(int ndef, int id, struct wpabuf *pubkey,
 				    struct wpabuf *dev_pw);
+int wps_nfc_gen_dh(struct wpabuf **pubkey, struct wpabuf **privkey);
 struct wpabuf * wps_nfc_token_gen(int ndef, int *id, struct wpabuf **pubkey,
 				  struct wpabuf **privkey,
 				  struct wpabuf **dev_pw);
diff --git a/src/wps/wps_common.c b/src/wps/wps_common.c
index 1c0e3ed5a..9919f2668 100644
--- a/src/wps/wps_common.c
+++ b/src/wps/wps_common.c
@@ -634,12 +634,36 @@ struct wpabuf * wps_nfc_token_build(int ndef, int id, struct wpabuf *pubkey,
 }
 
 
+int wps_nfc_gen_dh(struct wpabuf **pubkey, struct wpabuf **privkey)
+{
+	struct wpabuf *priv = NULL, *pub = NULL;
+	void *dh_ctx;
+
+	dh_ctx = dh5_init(&priv, &pub);
+	if (dh_ctx == NULL)
+		return -1;
+	pub = wpabuf_zeropad(pub, 192);
+	if (pub == NULL) {
+		wpabuf_free(priv);
+		return -1;
+	}
+	wpa_hexdump_buf(MSG_DEBUG, "WPS: Generated new DH pubkey", pub);
+	dh5_free(dh_ctx);
+
+	wpabuf_free(*pubkey);
+	*pubkey = pub;
+	wpabuf_free(*privkey);
+	*privkey = priv;
+
+	return 0;
+}
+
+
 struct wpabuf * wps_nfc_token_gen(int ndef, int *id, struct wpabuf **pubkey,
 				  struct wpabuf **privkey,
 				  struct wpabuf **dev_pw)
 {
-	struct wpabuf *priv = NULL, *pub = NULL, *pw;
-	void *dh_ctx;
+	struct wpabuf *pw;
 	u16 val;
 
 	pw = wpabuf_alloc(WPS_OOB_DEVICE_PASSWORD_LEN);
@@ -653,18 +677,12 @@ struct wpabuf * wps_nfc_token_gen(int ndef, int *id, struct wpabuf **pubkey,
 		return NULL;
 	}
 
-	dh_ctx = dh5_init(&priv, &pub);
-	if (dh_ctx == NULL) {
+	if (wps_nfc_gen_dh(pubkey, privkey) < 0) {
 		wpabuf_free(pw);
 		return NULL;
 	}
-	dh5_free(dh_ctx);
 
 	*id = 0x10 + val % 0xfff0;
-	wpabuf_free(*pubkey);
-	*pubkey = pub;
-	wpabuf_free(*privkey);
-	*privkey = priv;
 	wpabuf_free(*dev_pw);
 	*dev_pw = pw;