From 8e6485a1bcb0baffdea9e55255a81270b768439c Mon Sep 17 00:00:00 2001
Message-ID: <8e6485a1bcb0baffdea9e55255a81270b768439c.1708356763.git.davide.caratti@gmail.com>
From: Jouni Malinen <j@w1.fi>
Date: Sat, 8 Jul 2023 19:55:32 +0300
Subject: [PATCH] PEAP client: Update Phase 2 authentication requirements

The previous PEAP client behavior allowed the server to skip Phase 2
authentication with the expectation that the server was authenticated
during Phase 1 through TLS server certificate validation. Various PEAP
specifications are not exactly clear on what the behavior on this front
is supposed to be and as such, this ended up being more flexible than
the TTLS/FAST/TEAP cases. However, this is not really ideal when
unfortunately common misconfiguration of PEAP is used in deployed
devices where the server trust root (ca_cert) is not configured or the
user has an easy option for allowing this validation step to be skipped.

Change the default PEAP client behavior to be to require Phase 2
authentication to be successfully completed for cases where TLS session
resumption is not used and the client certificate has not been
configured. Those two exceptions are the main cases where a deployed
authentication server might skip Phase 2 and as such, where a more
strict default behavior could result in undesired interoperability
issues. Requiring Phase 2 authentication will end up disabling TLS
session resumption automatically to avoid interoperability issues.

Allow Phase 2 authentication behavior to be configured with a new phase1
configuration parameter option:
'phase2_auth' option can be used to control Phase 2 (i.e., within TLS
tunnel) behavior for PEAP:
 * 0 = do not require Phase 2 authentication
 * 1 = require Phase 2 authentication when client certificate
   (private_key/client_cert) is no used and TLS session resumption was
   not used (default)
 * 2 = require Phase 2 authentication in all cases

Signed-off-by: Jouni Malinen <j@w1.fi>
---
 src/eap_peer/eap_config.h          |  8 ++++++
 src/eap_peer/eap_peap.c            | 40 +++++++++++++++++++++++++++---
 src/eap_peer/eap_tls_common.c      |  6 +++++
 src/eap_peer/eap_tls_common.h      |  5 ++++
 wpa_supplicant/wpa_supplicant.conf |  7 ++++++
 5 files changed, 63 insertions(+), 3 deletions(-)

--- a/src/eap_peer/eap_config.h
+++ b/src/eap_peer/eap_config.h
@@ -469,6 +469,14 @@ struct eap_peer_config {
 	 * 1 = use cryptobinding if server supports it
 	 * 2 = require cryptobinding
 	 *
+	 * phase2_auth option can be used to control Phase 2 (i.e., within TLS
+	 * tunnel) behavior for PEAP:
+	 * 0 = do not require Phase 2 authentication
+	 * 1 = require Phase 2 authentication when client certificate
+	 *  (private_key/client_cert) is no used and TLS session resumption was
+	 *  not used (default)
+	 * 2 = require Phase 2 authentication in all cases
+	 *
 	 * EAP-WSC (WPS) uses following options: pin=Device_Password and
 	 * uuid=Device_UUID
 	 *
--- a/src/eap_peer/eap_peap.c
+++ b/src/eap_peer/eap_peap.c
@@ -67,6 +67,7 @@ struct eap_peap_data {
 	u8 cmk[20];
 	int soh; /* Whether IF-TNCCS-SOH (Statement of Health; Microsoft NAP)
 		  * is enabled. */
+	enum { NO_AUTH, FOR_INITIAL, ALWAYS } phase2_auth;
 };
 
 
@@ -114,6 +115,19 @@ static void eap_peap_parse_phase1(struct
 		wpa_printf(MSG_DEBUG, "EAP-PEAP: Require cryptobinding");
 	}
 
+	if (os_strstr(phase1, "phase2_auth=0")) {
+		data->phase2_auth = NO_AUTH;
+		wpa_printf(MSG_DEBUG,
+			   "EAP-PEAP: Do not require Phase 2 authentication");
+	} else if (os_strstr(phase1, "phase2_auth=1")) {
+		data->phase2_auth = FOR_INITIAL;
+		wpa_printf(MSG_DEBUG,
+			   "EAP-PEAP: Require Phase 2 authentication for initial connection");
+	} else if (os_strstr(phase1, "phase2_auth=2")) {
+		data->phase2_auth = ALWAYS;
+		wpa_printf(MSG_DEBUG,
+			   "EAP-PEAP: Require Phase 2 authentication for all cases");
+	}
 #ifdef EAP_TNC
 	if (os_strstr(phase1, "tnc=soh2")) {
 		data->soh = 2;
@@ -142,6 +156,7 @@ static void * eap_peap_init(struct eap_s
 	data->force_peap_version = -1;
 	data->peap_outer_success = 2;
 	data->crypto_binding = OPTIONAL_BINDING;
+	data->phase2_auth = FOR_INITIAL;
 
 	if (config && config->phase1)
 		eap_peap_parse_phase1(data, config->phase1);
@@ -454,6 +469,20 @@ static int eap_tlv_validate_cryptobindin
 }
 
 
+static bool peap_phase2_sufficient(struct eap_sm *sm,
+				   struct eap_peap_data *data)
+{
+	if ((data->phase2_auth == ALWAYS ||
+	     (data->phase2_auth == FOR_INITIAL &&
+	      !tls_connection_resumed(sm->ssl_ctx, data->ssl.conn) &&
+	      !data->ssl.client_cert_conf) ||
+	     data->phase2_eap_started) &&
+	    !data->phase2_eap_success)
+		return false;
+	return true;
+}
+
+
 /**
  * eap_tlv_process - Process a received EAP-TLV message and generate a response
  * @sm: Pointer to EAP state machine allocated with eap_peer_sm_init()
@@ -568,6 +597,11 @@ static int eap_tlv_process(struct eap_sm
 					   " - force failed Phase 2");
 				resp_status = EAP_TLV_RESULT_FAILURE;
 				ret->decision = DECISION_FAIL;
+			} else if (!peap_phase2_sufficient(sm, data)) {
+				wpa_printf(MSG_INFO,
+					   "EAP-PEAP: Server indicated Phase 2 success, but sufficient Phase 2 authentication has not been completed");
+				resp_status = EAP_TLV_RESULT_FAILURE;
+				ret->decision = DECISION_FAIL;
 			} else {
 				resp_status = EAP_TLV_RESULT_SUCCESS;
 				ret->decision = DECISION_UNCOND_SUCC;
@@ -887,8 +921,7 @@ continue_req:
 			/* EAP-Success within TLS tunnel is used to indicate
 			 * shutdown of the TLS channel. The authentication has
 			 * been completed. */
-			if (data->phase2_eap_started &&
-			    !data->phase2_eap_success) {
+			if (!peap_phase2_sufficient(sm, data)) {
 				wpa_printf(MSG_DEBUG, "EAP-PEAP: Phase 2 "
 					   "Success used to indicate success, "
 					   "but Phase 2 EAP was not yet "
@@ -1199,8 +1232,9 @@ static struct wpabuf * eap_peap_process(
 static bool eap_peap_has_reauth_data(struct eap_sm *sm, void *priv)
 {
 	struct eap_peap_data *data = priv;
+
 	return tls_connection_established(sm->ssl_ctx, data->ssl.conn) &&
-		data->phase2_success;
+		data->phase2_success && data->phase2_auth != ALWAYS;
 }
 
 
--- a/src/eap_peer/eap_tls_common.c
+++ b/src/eap_peer/eap_tls_common.c
@@ -239,6 +239,12 @@ static int eap_tls_params_from_conf(stru
 
 	sm->ext_cert_check = !!(params->flags & TLS_CONN_EXT_CERT_CHECK);
 
+	if (!phase2)
+		data->client_cert_conf = params->client_cert ||
+			params->client_cert_blob ||
+			params->private_key ||
+			params->private_key_blob;
+
 	return 0;
 }
 
--- a/src/eap_peer/eap_tls_common.h
+++ b/src/eap_peer/eap_tls_common.h
@@ -79,6 +79,11 @@ struct eap_ssl_data {
 	 * tls_v13 - Whether TLS v1.3 or newer is used
 	 */
 	int tls_v13;
+
+	/**
+	 * client_cert_conf: Whether client certificate has been configured
+	 */
+	bool client_cert_conf;
 };
 
 
--- a/wpa_supplicant/wpa_supplicant.conf
+++ b/wpa_supplicant/wpa_supplicant.conf
@@ -1330,6 +1330,13 @@ fast_reauth=1
 #	 * 0 = do not use cryptobinding (default)
 #	 * 1 = use cryptobinding if server supports it
 #	 * 2 = require cryptobinding
+#	'phase2_auth' option can be used to control Phase 2 (i.e., within TLS
+#	tunnel) behavior for PEAP:
+#	 * 0 = do not require Phase 2 authentication
+#	 * 1 = require Phase 2 authentication when client certificate
+#	   (private_key/client_cert) is no used and TLS session resumption was
+#	   not used (default)
+#	 * 2 = require Phase 2 authentication in all cases
 #	EAP-WSC (WPS) uses following options: pin=<Device Password> or
 #	pbc=1.
 #
