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 "utils/includes.h"
10
11 #include "utils/common.h"
12 #include "eap_peer/eap_defs.h"
13 #include "eap_peer/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 */
eap_hdr_len_valid(const struct wpabuf * msg,size_t min_payload)25 int 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 */
eap_hdr_validate(int vendor,EapType eap_type,const struct wpabuf * msg,size_t * plen)66 const 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 */
eap_msg_alloc(int vendor,EapType type,size_t payload_len,u8 code,u8 identifier)128 struct 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 */
eap_update_len(struct wpabuf * msg)167 void 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 */
eap_get_id(const struct wpabuf * msg)182 u8 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 */
eap_get_type(const struct wpabuf * msg)199 EapType 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
