From 872609c15110d32ee2d306aeeeffdd4e42ef6fc6 Mon Sep 17 00:00:00 2001
Message-Id: <872609c15110d32ee2d306aeeeffdd4e42ef6fc6.1627507211.git.davide.caratti@gmail.com>
From: Alexander Clouter <alex@digriz.org.uk>
Date: Fri, 16 Oct 2020 09:49:36 +0100
Subject: [PATCH] EAP-TTLS/PEAP peer: Fix failure when using session tickets
 under TLS 1.3

EAP peer does not expect data present when beginning the Phase 2 in
EAP-{TTLS,PEAP} but in TLS 1.3 session tickets are sent after the
handshake completes.

There are several strategies that can be used to handle this, but this
patch picks up from the discussion[1] and implements the proposed use of
SSL_MODE_AUTO_RETRY. SSL_MODE_AUTO_RETRY has already been enabled by
default in OpenSSL 1.1.1, but it needs to be enabled for older versions.

The main OpenSSL wrapper change in tls_connection_decrypt() takes care
of the new possible case with SSL_MODE_AUTO_RETRY for
SSL_ERROR_WANT_READ to indicate that a non-application_data was
processed. That is not really an error case with TLS 1.3, so allow it to
complete and return an empty decrypted application data buffer.
EAP-PEAP/TTLS processing can then use this to move ahead with starting
Phase 2.

[1] https://www.spinics.net/lists/hostap/msg05376.html

Signed-off-by: Alexander Clouter <alex@digriz.org.uk>
---
 src/crypto/tls_openssl.c | 18 ++++++++++++++----
 src/eap_peer/eap_peap.c  |  4 ++++
 src/eap_peer/eap_ttls.c  |  5 +++++
 3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/src/crypto/tls_openssl.c b/src/crypto/tls_openssl.c
index ef872c50e..345a35ee1 100644
--- a/src/crypto/tls_openssl.c
+++ b/src/crypto/tls_openssl.c
@@ -1045,6 +1045,8 @@ void * tls_init(const struct tls_config *conf)
 	SSL_CTX_set_options(ssl, SSL_OP_NO_SSLv2);
 	SSL_CTX_set_options(ssl, SSL_OP_NO_SSLv3);
 
+	SSL_CTX_set_mode(ssl, SSL_MODE_AUTO_RETRY);
+
 #ifdef SSL_MODE_NO_AUTO_CHAIN
 	/* Number of deployed use cases assume the default OpenSSL behavior of
 	 * auto chaining the local certificate is in use. BoringSSL removed this
@@ -4543,10 +4545,18 @@ struct wpabuf * tls_connection_decrypt(void *tls_ctx,
 		return NULL;
 	res = SSL_read(conn->ssl, wpabuf_mhead(buf), wpabuf_size(buf));
 	if (res < 0) {
-		tls_show_errors(MSG_INFO, __func__,
-				"Decryption failed - SSL_read");
-		wpabuf_free(buf);
-		return NULL;
+		int err = SSL_get_error(conn->ssl, res);
+
+		if (err == SSL_ERROR_WANT_READ) {
+			wpa_printf(MSG_DEBUG,
+				   "SSL: SSL_connect - want more data");
+			res = 0;
+		} else {
+			tls_show_errors(MSG_INFO, __func__,
+					"Decryption failed - SSL_read");
+			wpabuf_free(buf);
+			return NULL;
+		}
 	}
 	wpabuf_put(buf, res);
 
diff --git a/src/eap_peer/eap_peap.c b/src/eap_peer/eap_peap.c
index 7c3704369..a13428d37 100644
--- a/src/eap_peer/eap_peap.c
+++ b/src/eap_peer/eap_peap.c
@@ -803,6 +803,10 @@ static int eap_peap_decrypt(struct eap_sm *sm, struct eap_peap_data *data,
 	res = eap_peer_tls_decrypt(sm, &data->ssl, in_data, &in_decrypted);
 	if (res)
 		return res;
+	if (wpabuf_len(in_decrypted) == 0) {
+		wpabuf_free(in_decrypted);
+		return 1;
+	}
 
 continue_req:
 	wpa_hexdump_buf(MSG_DEBUG, "EAP-PEAP: Decrypted Phase 2 EAP",
diff --git a/src/eap_peer/eap_ttls.c b/src/eap_peer/eap_ttls.c
index 642d179c6..3bf1e97e6 100644
--- a/src/eap_peer/eap_ttls.c
+++ b/src/eap_peer/eap_ttls.c
@@ -1441,6 +1441,7 @@ static int eap_ttls_decrypt(struct eap_sm *sm, struct eap_ttls_data *data,
 
 	if ((in_data == NULL || wpabuf_len(in_data) == 0) &&
 	    data->phase2_start) {
+start:
 		return eap_ttls_phase2_start(sm, data, ret, identifier,
 					     out_data);
 	}
@@ -1455,6 +1456,10 @@ static int eap_ttls_decrypt(struct eap_sm *sm, struct eap_ttls_data *data,
 	retval = eap_peer_tls_decrypt(sm, &data->ssl, in_data, &in_decrypted);
 	if (retval)
 		goto done;
+	if (wpabuf_len(in_decrypted) == 0) {
+		wpabuf_free(in_decrypted);
+		goto start;
+	}
 
 continue_req:
 	data->phase2_start = 0;
-- 
2.31.1