1/*
2 * EAP common peer/server definitions
3 * Copyright (c) 2004-2012, Jouni Malinen <j@w1.fi>
4 *
5 * This software may be distributed under the terms of the BSD license.
6 * See README for more details.
7 */
8
9#include "includes.h"
10
11#include "common.h"
12#include "eap_defs.h"
13#include "eap_common.h"
14
15/**
16 * eap_hdr_len_valid - Validate EAP header length field
17 * @msg: EAP frame (starting with EAP header)
18 * @min_payload: Minimum payload length needed
19 * Returns: 1 for valid header, 0 for invalid
20 *
21 * This is a helper function that does minimal validation of EAP messages. The
22 * length field is verified to be large enough to include the header and not
23 * too large to go beyond the end of the buffer.
24 */
25int eap_hdr_len_valid(const struct wpabuf *msg, size_t min_payload)
26{
27	const struct eap_hdr *hdr;
28	size_t len;
29
30	if (msg == NULL)
31		return 0;
32
33	hdr = wpabuf_head(msg);
34
35	if (wpabuf_len(msg) < sizeof(*hdr)) {
36		wpa_printf(MSG_INFO, "EAP: Too short EAP frame");
37		return 0;
38	}
39
40	len = be_to_host16(hdr->length);
41	if (len < sizeof(*hdr) + min_payload || len > wpabuf_len(msg)) {
42		wpa_printf(MSG_INFO, "EAP: Invalid EAP length");
43		return 0;
44	}
45
46	return 1;
47}
48
49
50/**
51 * eap_hdr_validate - Validate EAP header
52 * @vendor: Expected EAP Vendor-Id (0 = IETF)
53 * @eap_type: Expected EAP type number
54 * @msg: EAP frame (starting with EAP header)
55 * @plen: Pointer to variable to contain the returned payload length
56 * Returns: Pointer to EAP payload (after type field), or %NULL on failure
57 *
58 * This is a helper function for EAP method implementations. This is usually
59 * called in the beginning of struct eap_method::process() function to verify
60 * that the received EAP request packet has a valid header. This function is
61 * able to process both legacy and expanded EAP headers and in most cases, the
62 * caller can just use the returned payload pointer (into *plen) for processing
63 * the payload regardless of whether the packet used the expanded EAP header or
64 * not.
65 */
66const u8 * eap_hdr_validate(int vendor, EapType eap_type,
67			    const struct wpabuf *msg, size_t *plen)
68{
69	const struct eap_hdr *hdr;
70	const u8 *pos;
71	size_t len;
72
73	if (!eap_hdr_len_valid(msg, 1))
74		return NULL;
75
76	hdr = wpabuf_head(msg);
77	len = be_to_host16(hdr->length);
78	pos = (const u8 *) (hdr + 1);
79
80	if (*pos == EAP_TYPE_EXPANDED) {
81		int exp_vendor;
82		u32 exp_type;
83		if (len < sizeof(*hdr) + 8) {
84			wpa_printf(MSG_INFO, "EAP: Invalid expanded EAP "
85				   "length");
86			return NULL;
87		}
88		pos++;
89		exp_vendor = WPA_GET_BE24(pos);
90		pos += 3;
91		exp_type = WPA_GET_BE32(pos);
92		pos += 4;
93		if (exp_vendor != vendor || exp_type != (u32) eap_type) {
94			wpa_printf(MSG_INFO, "EAP: Invalid expanded frame "
95				   "type");
96			return NULL;
97		}
98
99		*plen = len - sizeof(*hdr) - 8;
100		return pos;
101	} else {
102		if (vendor != EAP_VENDOR_IETF || *pos != eap_type) {
103			wpa_printf(MSG_INFO, "EAP: Invalid frame type");
104			return NULL;
105		}
106		*plen = len - sizeof(*hdr) - 1;
107		return pos + 1;
108	}
109}
110
111
112/**
113 * eap_msg_alloc - Allocate a buffer for an EAP message
114 * @vendor: Vendor-Id (0 = IETF)
115 * @type: EAP type
116 * @payload_len: Payload length in bytes (data after Type)
117 * @code: Message Code (EAP_CODE_*)
118 * @identifier: Identifier
119 * Returns: Pointer to the allocated message buffer or %NULL on error
120 *
121 * This function can be used to allocate a buffer for an EAP message and fill
122 * in the EAP header. This function is automatically using expanded EAP header
123 * if the selected Vendor-Id is not IETF. In other words, most EAP methods do
124 * not need to separately select which header type to use when using this
125 * function to allocate the message buffers. The returned buffer has room for
126 * payload_len bytes and has the EAP header and Type field already filled in.
127 */
128struct wpabuf * eap_msg_alloc(int vendor, EapType type, size_t payload_len,
129			      u8 code, u8 identifier)
130{
131	struct wpabuf *buf;
132	struct eap_hdr *hdr;
133	size_t len;
134
135	len = sizeof(struct eap_hdr) + (vendor == EAP_VENDOR_IETF ? 1 : 8) +
136		payload_len;
137	buf = wpabuf_alloc(len);
138	if (buf == NULL)
139		return NULL;
140
141	hdr = wpabuf_put(buf, sizeof(*hdr));
142	hdr->code = code;
143	hdr->identifier = identifier;
144	hdr->length = host_to_be16(len);
145
146	if (vendor == EAP_VENDOR_IETF) {
147		wpabuf_put_u8(buf, type);
148	} else {
149		wpabuf_put_u8(buf, EAP_TYPE_EXPANDED);
150		wpabuf_put_be24(buf, vendor);
151		wpabuf_put_be32(buf, type);
152	}
153
154	return buf;
155}
156
157
158/**
159 * eap_update_len - Update EAP header length
160 * @msg: EAP message from eap_msg_alloc
161 *
162 * This function updates the length field in the EAP header to match with the
163 * current length for the buffer. This allows eap_msg_alloc() to be used to
164 * allocate a larger buffer than the exact message length (e.g., if exact
165 * message length is not yet known).
166 */
167void eap_update_len(struct wpabuf *msg)
168{
169	struct eap_hdr *hdr;
170	hdr = wpabuf_mhead(msg);
171	if (wpabuf_len(msg) < sizeof(*hdr))
172		return;
173	hdr->length = host_to_be16(wpabuf_len(msg));
174}
175
176
177/**
178 * eap_get_id - Get EAP Identifier from wpabuf
179 * @msg: Buffer starting with an EAP header
180 * Returns: The Identifier field from the EAP header
181 */
182u8 eap_get_id(const struct wpabuf *msg)
183{
184	const struct eap_hdr *eap;
185
186	if (wpabuf_len(msg) < sizeof(*eap))
187		return 0;
188
189	eap = wpabuf_head(msg);
190	return eap->identifier;
191}
192
193
194/**
195 * eap_get_id - Get EAP Type from wpabuf
196 * @msg: Buffer starting with an EAP header
197 * Returns: The EAP Type after the EAP header
198 */
199EapType eap_get_type(const struct wpabuf *msg)
200{
201	if (wpabuf_len(msg) < sizeof(struct eap_hdr) + 1)
202		return EAP_TYPE_NONE;
203
204	return ((const u8 *) wpabuf_head(msg))[sizeof(struct eap_hdr)];
205}
206