1/*
2 * EAP common peer/server definitions
3 * Copyright (c) 2004-2007, Jouni Malinen <j@w1.fi>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 *
9 * Alternatively, this software may be distributed under the terms of BSD
10 * license.
11 *
12 * See README and COPYING for more details.
13 */
14
15#include "includes.h"
16
17#include "common.h"
18#include "eap_defs.h"
19#include "eap_common.h"
20
21/**
22 * eap_hdr_validate - Validate EAP header
23 * @vendor: Expected EAP Vendor-Id (0 = IETF)
24 * @eap_type: Expected EAP type number
25 * @msg: EAP frame (starting with EAP header)
26 * @plen: Pointer to variable to contain the returned payload length
27 * Returns: Pointer to EAP payload (after type field), or %NULL on failure
28 *
29 * This is a helper function for EAP method implementations. This is usually
30 * called in the beginning of struct eap_method::process() function to verify
31 * that the received EAP request packet has a valid header. This function is
32 * able to process both legacy and expanded EAP headers and in most cases, the
33 * caller can just use the returned payload pointer (into *plen) for processing
34 * the payload regardless of whether the packet used the expanded EAP header or
35 * not.
36 */
37const u8 * eap_hdr_validate(int vendor, EapType eap_type,
38			    const struct wpabuf *msg, size_t *plen)
39{
40	const struct eap_hdr *hdr;
41	const u8 *pos;
42	size_t len;
43
44	hdr = wpabuf_head(msg);
45
46	if (wpabuf_len(msg) < sizeof(*hdr)) {
47		wpa_printf(MSG_INFO, "EAP: Too short EAP frame");
48		return NULL;
49	}
50
51	len = be_to_host16(hdr->length);
52	if (len < sizeof(*hdr) + 1 || len > wpabuf_len(msg)) {
53		wpa_printf(MSG_INFO, "EAP: Invalid EAP length");
54		return NULL;
55	}
56
57	pos = (const u8 *) (hdr + 1);
58
59	if (*pos == EAP_TYPE_EXPANDED) {
60		int exp_vendor;
61		u32 exp_type;
62		if (len < sizeof(*hdr) + 8) {
63			wpa_printf(MSG_INFO, "EAP: Invalid expanded EAP "
64				   "length");
65			return NULL;
66		}
67		pos++;
68		exp_vendor = WPA_GET_BE24(pos);
69		pos += 3;
70		exp_type = WPA_GET_BE32(pos);
71		pos += 4;
72		if (exp_vendor != vendor || exp_type != (u32) eap_type) {
73			wpa_printf(MSG_INFO, "EAP: Invalid expanded frame "
74				   "type");
75			return NULL;
76		}
77
78		*plen = len - sizeof(*hdr) - 8;
79		return pos;
80	} else {
81		if (vendor != EAP_VENDOR_IETF || *pos != eap_type) {
82			wpa_printf(MSG_INFO, "EAP: Invalid frame type");
83			return NULL;
84		}
85		*plen = len - sizeof(*hdr) - 1;
86		return pos + 1;
87	}
88}
89
90
91/**
92 * eap_msg_alloc - Allocate a buffer for an EAP message
93 * @vendor: Vendor-Id (0 = IETF)
94 * @type: EAP type
95 * @payload_len: Payload length in bytes (data after Type)
96 * @code: Message Code (EAP_CODE_*)
97 * @identifier: Identifier
98 * Returns: Pointer to the allocated message buffer or %NULL on error
99 *
100 * This function can be used to allocate a buffer for an EAP message and fill
101 * in the EAP header. This function is automatically using expanded EAP header
102 * if the selected Vendor-Id is not IETF. In other words, most EAP methods do
103 * not need to separately select which header type to use when using this
104 * function to allocate the message buffers. The returned buffer has room for
105 * payload_len bytes and has the EAP header and Type field already filled in.
106 */
107struct wpabuf * eap_msg_alloc(int vendor, EapType type, size_t payload_len,
108			      u8 code, u8 identifier)
109{
110	struct wpabuf *buf;
111	struct eap_hdr *hdr;
112	size_t len;
113
114	len = sizeof(struct eap_hdr) + (vendor == EAP_VENDOR_IETF ? 1 : 8) +
115		payload_len;
116	buf = wpabuf_alloc(len);
117	if (buf == NULL)
118		return NULL;
119
120	hdr = wpabuf_put(buf, sizeof(*hdr));
121	hdr->code = code;
122	hdr->identifier = identifier;
123	hdr->length = host_to_be16(len);
124
125	if (vendor == EAP_VENDOR_IETF) {
126		wpabuf_put_u8(buf, type);
127	} else {
128		wpabuf_put_u8(buf, EAP_TYPE_EXPANDED);
129		wpabuf_put_be24(buf, vendor);
130		wpabuf_put_be32(buf, type);
131	}
132
133	return buf;
134}
135
136
137/**
138 * eap_update_len - Update EAP header length
139 * @msg: EAP message from eap_msg_alloc
140 *
141 * This function updates the length field in the EAP header to match with the
142 * current length for the buffer. This allows eap_msg_alloc() to be used to
143 * allocate a larger buffer than the exact message length (e.g., if exact
144 * message length is not yet known).
145 */
146void eap_update_len(struct wpabuf *msg)
147{
148	struct eap_hdr *hdr;
149	hdr = wpabuf_mhead(msg);
150	if (wpabuf_len(msg) < sizeof(*hdr))
151		return;
152	hdr->length = host_to_be16(wpabuf_len(msg));
153}
154
155
156/**
157 * eap_get_id - Get EAP Identifier from wpabuf
158 * @msg: Buffer starting with an EAP header
159 * Returns: The Identifier field from the EAP header
160 */
161u8 eap_get_id(const struct wpabuf *msg)
162{
163	const struct eap_hdr *eap;
164
165	if (wpabuf_len(msg) < sizeof(*eap))
166		return 0;
167
168	eap = wpabuf_head(msg);
169	return eap->identifier;
170}
171
172
173/**
174 * eap_get_id - Get EAP Type from wpabuf
175 * @msg: Buffer starting with an EAP header
176 * Returns: The EAP Type after the EAP header
177 */
178EapType eap_get_type(const struct wpabuf *msg)
179{
180	if (wpabuf_len(msg) < sizeof(struct eap_hdr) + 1)
181		return EAP_TYPE_NONE;
182
183	return ((const u8 *) wpabuf_head(msg))[sizeof(struct eap_hdr)];
184}
185