From: Jouni Malinen <j@w1.fi>
Date: Wed, 1 Jan 2025 09:17:31 +0000 (+0200)
Subject: EAP-TEAP: Add a compatibility mode for FreeRADIUS
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=795075444fe847e11a04de541c95613335aad7a5;p=thirdparty%2Fhostap.git

EAP-TEAP: Add a compatibility mode for FreeRADIUS

FreeRADIUS (at least the current snapshot of the v3.2.x branch) uses
different style for deriving S-IMCK[j]. It tracks S_IMCK_MSK[j] and
S_IMCK_EMSK[j] variants through all inner methods instead of selecting a
single S_IMCK[j] at the end of each inner method. IMHO, that does not
match what is most likely described in RFC 7170bis, it is a potential
interpretation of the draft and is closer to what wpa_supplicant used to
do earlier. However, that design has a weakness in EMSK derivation from
TEAP since it does not actually get any input from inner methods that do
not derive an EMSK.

Obviously, there should be only a single shared interpretation on how
TEAPv1 is supposed to work, but until we get to that point, it is
convenient to be able to test other parts of the protocol without having
to modify source code to work around differences. Introduce a new
phase1="teap_compat=freeradius" configuration parameter to
wpa_supplicant to allow EAP-TEAP peer behavior to be modified to match
what FreeRADIUS expects.

This compatibility mode was now able to successfully authenticate (and
also to derive matching MSK and EMSK) against FreeRADIUS v3.2.x branch
snapshot with all four combinations of machine(EAP-TLS) and
user(EAP-MSCHAPv2) authentication.

Signed-off-by: Jouni Malinen <j@w1.fi>
---

diff --git a/src/eap_peer/eap_teap.c b/src/eap_peer/eap_teap.c
index d9f8cbddf..8ce7cb7e9 100644
--- a/src/eap_peer/eap_teap.c
+++ b/src/eap_peer/eap_teap.c
@@ -56,6 +56,11 @@ struct eap_teap_data {
 	struct wpabuf *pending_resp;
 	struct wpabuf *server_outer_tlvs;
 	struct wpabuf *peer_outer_tlvs;
+
+	enum teap_compat {
+		TEAP_DEFAULT,
+		TEAP_FREERADIUS,
+	} teap_compat;
 };
 
 
@@ -66,6 +71,9 @@ static void eap_teap_parse_phase1(struct eap_teap_data *data,
 	if (os_strstr(phase1, "teap_test_outer_tlvs=1"))
 		data->test_outer_tlvs = 1;
 #endif /* CONFIG_TESTING_OPTIONS */
+
+	if (os_strstr(phase1, "teap_compat=freeradius"))
+		data->teap_compat = TEAP_FREERADIUS;
 }
 
 
@@ -613,10 +621,28 @@ static int eap_teap_get_cmk(struct eap_sm *sm, struct eap_teap_data *data,
 	}
 
 out:
-	res = eap_teap_derive_imck(data->tls_cs, data->simck,
-				   msk, msk_len, emsk, emsk_len,
-				   data->simck_msk, cmk_msk,
-				   data->simck_emsk, cmk_emsk);
+	if (data->teap_compat == TEAP_FREERADIUS) {
+		u8 tmp_simck[EAP_TEAP_SIMCK_LEN];
+		u8 tmp_cmk[EAP_TEAP_CMK_LEN];
+
+		wpa_printf(MSG_DEBUG,
+			   "EAP-TEAP: FreeRADIUS compatibility: use S-IMCK_MSK[j-1] and S-IMCK_EMSK[j-1] based on MSK/EMSK derivations instead of a single selected S-IMCK[j-1]");
+		res = eap_teap_derive_imck(data->tls_cs, data->simck_msk,
+					   msk, msk_len, emsk, emsk_len,
+					   data->simck_msk, cmk_msk,
+					   tmp_simck, tmp_cmk);
+		if (emsk)
+			res = eap_teap_derive_imck(data->tls_cs,
+						   data->simck_emsk,
+						   msk, msk_len, emsk, emsk_len,
+						   tmp_simck, tmp_cmk,
+						   data->simck_emsk, cmk_emsk);
+	} else {
+		res = eap_teap_derive_imck(data->tls_cs, data->simck,
+					   msk, msk_len, emsk, emsk_len,
+					   data->simck_msk, cmk_msk,
+					   data->simck_emsk, cmk_emsk);
+	}
 	bin_clear_free(msk, msk_len);
 	bin_clear_free(emsk, emsk_len);
 	if (res == 0) {