eap_common.c revision c5ec7f57ead87efa365800228aa0b09a12d9e6c4 
1/*
2 * EAP common peer/server definitions
3 * Copyright (c) 2004-2007, 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_validate - Validate EAP header
17 * @vendor: Expected EAP Vendor-Id (0 = IETF)
18 * @eap_type: Expected EAP type number
19 * @msg: EAP frame (starting with EAP header)
20 * @plen: Pointer to variable to contain the returned payload length
21 * Returns: Pointer to EAP payload (after type field), or %NULL on failure
22 *
23 * This is a helper function for EAP method implementations. This is usually
24 * called in the beginning of struct eap_method::process() function to verify
25 * that the received EAP request packet has a valid header. This function is
26 * able to process both legacy and expanded EAP headers and in most cases, the
27 * caller can just use the returned payload pointer (into *plen) for processing
28 * the payload regardless of whether the packet used the expanded EAP header or
29 * not.
30 */
31const u8 * eap_hdr_validate(int vendor, EapType eap_type,
32			    const struct wpabuf *msg, size_t *plen)
33{
34	const struct eap_hdr *hdr;
35	const u8 *pos;
36	size_t len;
37
38	hdr = wpabuf_head(msg);
39
40	if (wpabuf_len(msg) < sizeof(*hdr)) {
41		wpa_printf(MSG_INFO, "EAP: Too short EAP frame");
42		return NULL;
43	}
44
45	len = be_to_host16(hdr->length);
46	if (len < sizeof(*hdr) + 1 || len > wpabuf_len(msg)) {
47		wpa_printf(MSG_INFO, "EAP: Invalid EAP length");
48		return NULL;
49	}
50
51	pos = (const u8 *) (hdr + 1);
52
53	if (*pos == EAP_TYPE_EXPANDED) {
54		int exp_vendor;
55		u32 exp_type;
56		if (len < sizeof(*hdr) + 8) {
57			wpa_printf(MSG_INFO, "EAP: Invalid expanded EAP "
58				   "length");
59			return NULL;
60		}
61		pos++;
62		exp_vendor = WPA_GET_BE24(pos);
63		pos += 3;
64		exp_type = WPA_GET_BE32(pos);
65		pos += 4;
66		if (exp_vendor != vendor || exp_type != (u32) eap_type) {
67			wpa_printf(MSG_INFO, "EAP: Invalid expanded frame "
68				   "type");
69			return NULL;
70		}
71
72		*plen = len - sizeof(*hdr) - 8;
73		return pos;
74	} else {
75		if (vendor != EAP_VENDOR_IETF || *pos != eap_type) {
76			wpa_printf(MSG_INFO, "EAP: Invalid frame type");
77			return NULL;
78		}
79		*plen = len - sizeof(*hdr) - 1;
80		return pos + 1;
81	}
82}
83
84
85/**
86 * eap_msg_alloc - Allocate a buffer for an EAP message
87 * @vendor: Vendor-Id (0 = IETF)
88 * @type: EAP type
89 * @payload_len: Payload length in bytes (data after Type)
90 * @code: Message Code (EAP_CODE_*)
91 * @identifier: Identifier
92 * Returns: Pointer to the allocated message buffer or %NULL on error
93 *
94 * This function can be used to allocate a buffer for an EAP message and fill
95 * in the EAP header. This function is automatically using expanded EAP header
96 * if the selected Vendor-Id is not IETF. In other words, most EAP methods do
97 * not need to separately select which header type to use when using this
98 * function to allocate the message buffers. The returned buffer has room for
99 * payload_len bytes and has the EAP header and Type field already filled in.
100 */
101struct wpabuf * eap_msg_alloc(int vendor, EapType type, size_t payload_len,
102			      u8 code, u8 identifier)
103{
104	struct wpabuf *buf;
105	struct eap_hdr *hdr;
106	size_t len;
107
108	len = sizeof(struct eap_hdr) + (vendor == EAP_VENDOR_IETF ? 1 : 8) +
109		payload_len;
110	buf = wpabuf_alloc(len);
111	if (buf == NULL)
112		return NULL;
113
114	hdr = wpabuf_put(buf, sizeof(*hdr));
115	hdr->code = code;
116	hdr->identifier = identifier;
117	hdr->length = host_to_be16(len);
118
119	if (vendor == EAP_VENDOR_IETF) {
120		wpabuf_put_u8(buf, type);
121	} else {
122		wpabuf_put_u8(buf, EAP_TYPE_EXPANDED);
123		wpabuf_put_be24(buf, vendor);
124		wpabuf_put_be32(buf, type);
125	}
126
127	return buf;
128}
129
130
131/**
132 * eap_update_len - Update EAP header length
133 * @msg: EAP message from eap_msg_alloc
134 *
135 * This function updates the length field in the EAP header to match with the
136 * current length for the buffer. This allows eap_msg_alloc() to be used to
137 * allocate a larger buffer than the exact message length (e.g., if exact
138 * message length is not yet known).
139 */
140void eap_update_len(struct wpabuf *msg)
141{
142	struct eap_hdr *hdr;
143	hdr = wpabuf_mhead(msg);
144	if (wpabuf_len(msg) < sizeof(*hdr))
145		return;
146	hdr->length = host_to_be16(wpabuf_len(msg));
147}
148
149
150/**
151 * eap_get_id - Get EAP Identifier from wpabuf
152 * @msg: Buffer starting with an EAP header
153 * Returns: The Identifier field from the EAP header
154 */
155u8 eap_get_id(const struct wpabuf *msg)
156{
157	const struct eap_hdr *eap;
158
159	if (wpabuf_len(msg) < sizeof(*eap))
160		return 0;
161
162	eap = wpabuf_head(msg);
163	return eap->identifier;
164}
165
166
167/**
168 * eap_get_id - Get EAP Type from wpabuf
169 * @msg: Buffer starting with an EAP header
170 * Returns: The EAP Type after the EAP header
171 */
172EapType eap_get_type(const struct wpabuf *msg)
173{
174	if (wpabuf_len(msg) < sizeof(struct eap_hdr) + 1)
175		return EAP_TYPE_NONE;
176
177	return ((const u8 *) wpabuf_head(msg))[sizeof(struct eap_hdr)];
178}
179