eap_mschapv2.c

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/*
 * EAP peer method: EAP-MSCHAPV2 (draft-kamath-pppext-eap-mschapv2-00.txt)
 * Copyright (c) 2004-2006, Jouni Malinen <[e-mail]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 *
 * This file implements EAP peer part of EAP-MSCHAPV2 method (EAP type 26).
 * draft-kamath-pppext-eap-mschapv2-00.txt defines the Microsoft EAP CHAP
 * Extensions Protocol, Version 2, for mutual authentication and key
 * derivation. This encapsulates MS-CHAP-v2 protocol which is defined in
 * RFC 2759. Use of EAP-MSCHAPV2 derived keys with MPPE cipher is described in
 * RFC 3079.
 */

#include "includes.h"

#include "common.h"
#include "eap_i.h"
#include "config_ssid.h"
#include "ms_funcs.h"
#include "wpa_ctrl.h"


#define MSCHAPV2_CHAL_LEN 16
#define MSCHAPV2_NT_RESPONSE_LEN 24

#ifdef _MSC_VER
#pragma pack(push, 1)
#endif /* _MSC_VER */

struct eap_mschapv2_hdr {
	u8 op_code; /* MSCHAPV2_OP_* */
	u8 mschapv2_id; /* usually same as EAP identifier; must be changed
			 * for challenges, but not for success/failure */
	u8 ms_length[2]; /* Note: misaligned; length - 5 */
	/* followed by data */
} STRUCT_PACKED;

/* Response Data field */
struct ms_response {
	u8 peer_challenge[MSCHAPV2_CHAL_LEN];
	u8 reserved[8];
	u8 nt_response[MSCHAPV2_NT_RESPONSE_LEN];
	u8 flags;
} STRUCT_PACKED;

/* Change-Password Data field */
struct ms_change_password {
	u8 encr_password[516];
	u8 encr_hash[16];
	u8 peer_challenge[MSCHAPV2_CHAL_LEN];
	u8 reserved[8];
	u8 nt_response[MSCHAPV2_NT_RESPONSE_LEN];
	u8 flags[2];
} STRUCT_PACKED;

#ifdef _MSC_VER
#pragma pack(pop)
#endif /* _MSC_VER */

#define MSCHAPV2_OP_CHALLENGE 1
#define MSCHAPV2_OP_RESPONSE 2
#define MSCHAPV2_OP_SUCCESS 3
#define MSCHAPV2_OP_FAILURE 4
#define MSCHAPV2_OP_CHANGE_PASSWORD 7

#define ERROR_RESTRICTED_LOGON_HOURS 646
#define ERROR_ACCT_DISABLED 647
#define ERROR_PASSWD_EXPIRED 648
#define ERROR_NO_DIALIN_PERMISSION 649
#define ERROR_AUTHENTICATION_FAILURE 691
#define ERROR_CHANGING_PASSWORD 709

#define PASSWD_CHANGE_CHAL_LEN 16
#define MSCHAPV2_KEY_LEN 16


struct eap_mschapv2_data {
	u8 auth_response[20];
	int auth_response_valid;

	int prev_error;
	u8 passwd_change_challenge[PASSWD_CHANGE_CHAL_LEN];
	int passwd_change_challenge_valid;
	int passwd_change_version;

	/* Optional challenge values generated in EAP-FAST Phase 1 negotiation
	 */
	u8 *peer_challenge;
	u8 *auth_challenge;
	int full_key;

	int phase2;
	u8 master_key[16];
	int master_key_valid;
	int success;

	u8 *prev_challenge;
	size_t prev_challenge_len;
};


static void eap_mschapv2_deinit(struct eap_sm *sm, void *priv);


static void * eap_mschapv2_init(struct eap_sm *sm)
{
	struct eap_mschapv2_data *data;
	data = os_zalloc(sizeof(*data));
	if (data == NULL)
		return NULL;

	data->full_key = sm->mschapv2_full_key;

	if (sm->peer_challenge) {
		data->full_key = 1;
		data->peer_challenge = os_malloc(MSCHAPV2_CHAL_LEN);
		if (data->peer_challenge == NULL) {
			eap_mschapv2_deinit(sm, data);
			return NULL;
		}
		os_memcpy(data->peer_challenge, sm->peer_challenge,
			  MSCHAPV2_CHAL_LEN);
	}

	if (sm->auth_challenge) {
		data->auth_challenge = os_malloc(MSCHAPV2_CHAL_LEN);
		if (data->auth_challenge == NULL) {
			eap_mschapv2_deinit(sm, data);
			return NULL;
		}
		os_memcpy(data->auth_challenge, sm->auth_challenge,
			  MSCHAPV2_CHAL_LEN);
	}

	data->phase2 = sm->init_phase2;

	return data;
}


static void eap_mschapv2_deinit(struct eap_sm *sm, void *priv)
{
	struct eap_mschapv2_data *data = priv;
	os_free(data->peer_challenge);
	os_free(data->auth_challenge);
	os_free(data->prev_challenge);
	os_free(data);
}


static const u8 * eap_mschapv2_remove_domain(const u8 *username, size_t *len)
{
	size_t i;

	/*
	 * MSCHAPv2 does not include optional domain name in the
	 * challenge-response calculation, so remove domain prefix
	 * (if present).
	 */

	for (i = 0; i < *len; i++) {
		if (username[i] == '\\') {
			*len -= i + 1;
			return username + i + 1;
		}
	}

	return username;
}


static void eap_mschapv2_derive_response(
	struct eap_mschapv2_data *data,
	const u8 *username, size_t username_len,
	const u8 *password, size_t password_len,
	const u8 *auth_challenge, const u8 *peer_challenge,
	u8 *nt_response)
{
	u8 password_hash[16], password_hash_hash[16];

	wpa_hexdump(MSG_DEBUG, "EAP-MSCHAPV2: auth_challenge",
		    auth_challenge, MSCHAPV2_CHAL_LEN);
	wpa_hexdump(MSG_DEBUG, "EAP-MSCHAPV2: peer_challenge",
		    peer_challenge, MSCHAPV2_CHAL_LEN);
	wpa_hexdump_ascii(MSG_DEBUG, "EAP-MSCHAPV2: username",
			  username, username_len);
	wpa_hexdump_ascii_key(MSG_DEBUG, "EAP-MSCHAPV2: password",
			      password, password_len);
	generate_nt_response(auth_challenge, peer_challenge,
			     username, username_len,
			     password, password_len, nt_response);
	wpa_hexdump(MSG_DEBUG, "EAP-MSCHAPV2: response", nt_response,
		    MSCHAPV2_NT_RESPONSE_LEN);
	/* Authenticator response is not really needed yet, but calculate it
	 * here so that challenges need not be saved. */
	generate_authenticator_response(password, password_len,
					peer_challenge, auth_challenge,
					username, username_len, nt_response,
					data->auth_response);
	data->auth_response_valid = 1;

	/* Likewise, generate master_key here since we have the needed data
	 * available. */
	nt_password_hash(password, password_len, password_hash);
	hash_nt_password_hash(password_hash, password_hash_hash);
	get_master_key(password_hash_hash, nt_response, data->master_key);
	data->master_key_valid = 1;
}


static u8 * eap_mschapv2_challenge_reply(struct eap_sm *sm,
					 struct eap_mschapv2_data *data, u8 id,
					 u8 mschapv2_id,
					 const u8 *auth_challenge,
					 size_t *respDataLen)
{
	struct eap_hdr *resp;
	struct eap_mschapv2_hdr *ms;
	u8 *rpos, *peer_challenge;
	int ms_len;
	struct ms_response *r;
	size_t username_len, identity_len, password_len;
	const u8 *username, *identity, *password;

	wpa_printf(MSG_DEBUG, "EAP-MSCHAPV2: Generating Challenge Response");

	identity = eap_get_config_identity(sm, &identity_len);
	password = eap_get_config_password(sm, &password_len);
	if (identity == NULL || password == NULL)
		return NULL;

	username_len = identity_len;
	username = eap_mschapv2_remove_domain(identity, &username_len);

	ms_len = sizeof(*ms) + 1 + sizeof(*r) + identity_len;
	resp = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_MSCHAPV2, respDataLen,
			     ms_len, EAP_CODE_RESPONSE, id, &rpos);
	if (resp == NULL)
		return NULL;

	ms = (struct eap_mschapv2_hdr *) rpos;
	ms->op_code = MSCHAPV2_OP_RESPONSE;
	ms->mschapv2_id = mschapv2_id;
	if (data->prev_error) {
		/*
		 * TODO: this does not seem to be enough when processing two
		 * or more failure messages. IAS did not increment mschapv2_id
		 * in its own packets, but it seemed to expect the peer to
		 * increment this for all packets(?).
		 */
		ms->mschapv2_id++;
	}
	WPA_PUT_BE16(ms->ms_length, ms_len);
	rpos = (u8 *) (ms + 1);
	*rpos++ = sizeof(*r); /* Value-Size */

	/* Response */
	r = (struct ms_response *) rpos;
	peer_challenge = r->peer_challenge;
	if (data->peer_challenge) {
		wpa_printf(MSG_DEBUG, "EAP-MSCHAPV2: peer_challenge generated "
			   "in Phase 1");
		peer_challenge = data->peer_challenge;
		os_memset(r->peer_challenge, 0, MSCHAPV2_CHAL_LEN);
	} else if (os_get_random(peer_challenge, MSCHAPV2_CHAL_LEN)) {
		os_free(resp);
		return NULL;
	}
	os_memset(r->reserved, 0, 8);
	if (data->auth_challenge) {
		wpa_printf(MSG_DEBUG, "EAP-MSCHAPV2: auth_challenge generated "
			   "in Phase 1");
		auth_challenge = data->auth_challenge;
	}
	eap_mschapv2_derive_response(data, username, username_len,
				     password, password_len,
				     auth_challenge, peer_challenge,
				     r->nt_response);

	r->flags = 0; /* reserved, must be zero */

	os_memcpy((u8 *) (r + 1), identity, identity_len);
	wpa_printf(MSG_DEBUG, "EAP-MSCHAPV2: TX identifier %d mschapv2_id %d "
		   "(response)", resp->identifier, ms->mschapv2_id);
	return (u8 *) resp;
}


/**
 * eap_mschapv2_process - Process an EAP-MSCHAPv2 challenge message
 * @sm: Pointer to EAP state machine allocated with eap_sm_init()
 * @data: Pointer to private EAP method data from eap_mschapv2_init()
 * @ret: Return values from EAP request validation and processing
 * @req: Pointer to EAP-MSCHAPv2 header from the request
 * @req_len: Length of the EAP-MSCHAPv2 data
 * @id: EAP identifier used in th erequest
 * @respDataLen: Length of the returned EAP response
 * Returns: Pointer to allocated EAP response packet (eapRespData) or %NULL if
 * no reply available
 */
static u8 * eap_mschapv2_challenge(struct eap_sm *sm,
				   struct eap_mschapv2_data *data,
				   struct eap_method_ret *ret,
				   const struct eap_mschapv2_hdr *req,
				   size_t req_len, u8 id, size_t *respDataLen)
{
	size_t len, challenge_len;
	const u8 *pos, *challenge;

	if (eap_get_config_identity(sm, &len) == NULL ||
	    eap_get_config_password(sm, &len) == NULL)
		return NULL;

	wpa_printf(MSG_DEBUG, "EAP-MSCHAPV2: Received challenge");
	if (req_len < sizeof(*req) + 1) {
		wpa_printf(MSG_INFO, "EAP-MSCHAPV2: Too short challenge data "
			   "(len %lu)", (unsigned long) req_len);
		ret->ignore = TRUE;
		return NULL;
	}
	pos = (const u8 *) (req + 1);
	challenge_len = *pos++;
	len = req_len - sizeof(*req) - 1;
	if (challenge_len != MSCHAPV2_CHAL_LEN) {
		wpa_printf(MSG_INFO, "EAP-MSCHAPV2: Invalid challenge length "
			   "%lu", (unsigned long) challenge_len);
		ret->ignore = TRUE;
		return NULL;
	}

	if (len < challenge_len) {
		wpa_printf(MSG_INFO, "EAP-MSCHAPV2: Too short challenge"
			   " packet: len=%lu challenge_len=%lu",
			   (unsigned long) len, (unsigned long) challenge_len);
		ret->ignore = TRUE;
		return NULL;
	}

	if (data->passwd_change_challenge_valid) {
		wpa_printf(MSG_DEBUG, "EAP-MSCHAPV2: Using challenge from the "
			   "failure message");
		challenge = data->passwd_change_challenge;
	} else
		challenge = pos;
	pos += challenge_len;
	len -= challenge_len;
	wpa_hexdump_ascii(MSG_DEBUG, "EAP-MSCHAPV2: Authentication Servername",
		    pos, len);

	ret->ignore = FALSE;
	ret->methodState = METHOD_MAY_CONT;
	ret->decision = DECISION_FAIL;
	ret->allowNotifications = TRUE;

	return eap_mschapv2_challenge_reply(sm, data, id, req->mschapv2_id,
					    challenge, respDataLen);
}


static void eap_mschapv2_password_changed(struct eap_sm *sm,
					  struct eap_mschapv2_data *data)
{
	struct wpa_ssid *config = eap_get_config(sm);
	if (config && config->new_password) {
		wpa_msg(sm->msg_ctx, MSG_INFO,
			WPA_EVENT_PASSWORD_CHANGED
			"EAP-MSCHAPV2: Password changed successfully");
		data->prev_error = 0;
		os_free(config->password);
		config->password = config->new_password;
		config->new_password = NULL;
		config->password_len = config->new_password_len;
		config->new_password_len = 0;
	}
}


/**
 * eap_mschapv2_process - Process an EAP-MSCHAPv2 success message
 * @sm: Pointer to EAP state machine allocated with eap_sm_init()
 * @data: Pointer to private EAP method data from eap_mschapv2_init()
 * @ret: Return values from EAP request validation and processing
 * @req: Pointer to EAP-MSCHAPv2 header from the request
 * @req_len: Length of the EAP-MSCHAPv2 data
 * @id: EAP identifier used in th erequest
 * @respDataLen: Length of the returned EAP response
 * Returns: Pointer to allocated EAP response packet (eapRespData) or %NULL if
 * no reply available
 */
static u8 * eap_mschapv2_success(struct eap_sm *sm,
				 struct eap_mschapv2_data *data,
				 struct eap_method_ret *ret,
				 const struct eap_mschapv2_hdr *req,
				 size_t req_len, u8 id, size_t *respDataLen)
{
	struct eap_hdr *resp;
	struct eap_mschapv2_hdr *ms;
	const u8 *pos;
	u8 recv_response[20];
	size_t len;
	u8 *rpos;

	wpa_printf(MSG_DEBUG, "EAP-MSCHAPV2: Received success");
	len = req_len - sizeof(*req);
	pos = (const u8 *) (req + 1);
	if (!data->auth_response_valid || len < 42 ||
	    pos[0] != 'S' || pos[1] != '=' ||
	    hexstr2bin((char *) (pos + 2), recv_response, 20) ||
	    os_memcmp(data->auth_response, recv_response, 20) != 0) {
		wpa_printf(MSG_WARNING, "EAP-MSCHAPV2: Invalid authenticator "
			   "response in success request");
		ret->methodState = METHOD_DONE;
		ret->decision = DECISION_FAIL;
		return NULL;
	}
	pos += 42;
	len -= 42;
	while (len > 0 && *pos == ' ') {
		pos++;
		len--;
	}
	wpa_hexdump_ascii(MSG_DEBUG, "EAP-MSCHAPV2: Success message",
			  pos, len);
	wpa_printf(MSG_INFO, "EAP-MSCHAPV2: Authentication succeeded");

	/* Note: Only op_code of the EAP-MSCHAPV2 header is included in success
	 * message. */
	resp = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_MSCHAPV2, respDataLen,
			     1, EAP_CODE_RESPONSE, id, &rpos);
	if (resp == NULL) {
		wpa_printf(MSG_DEBUG, "EAP-MSCHAPV2: Failed to allocate "
			   "buffer for success response");
		ret->ignore = TRUE;
		return NULL;
	}

	ms = (struct eap_mschapv2_hdr *) rpos;
	ms->op_code = MSCHAPV2_OP_SUCCESS;

	ret->methodState = METHOD_DONE;
	ret->decision = DECISION_UNCOND_SUCC;
	ret->allowNotifications = FALSE;
	data->success = 1;

	if (data->prev_error == ERROR_PASSWD_EXPIRED)
		eap_mschapv2_password_changed(sm, data);

	return (u8 *) resp;
}


static int eap_mschapv2_failure_txt(struct eap_sm *sm,
				    struct eap_mschapv2_data *data, char *txt)
{
	char *pos, *msg = "";
	int retry = 1;
	struct wpa_ssid *config = eap_get_config(sm);

	/* For example:
	 * E=691 R=1 C=<32 octets hex challenge> V=3 M=Authentication Failure
	 */

	pos = txt;

	if (pos && os_strncmp(pos, "E=", 2) == 0) {