1 /* $OpenBSD: ssl_packet.c,v 1.15 2022/11/26 16:08:56 tb Exp $ */
2 /*
3 * Copyright (c) 2016, 2017 Joel Sing <jsing@openbsd.org>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18 #include "bytestring.h"
19 #include "ssl_local.h"
20
21 static int
ssl_is_sslv2_client_hello(CBS * header)22 ssl_is_sslv2_client_hello(CBS *header)
23 {
24 uint16_t record_length;
25 uint8_t message_type;
26 CBS cbs;
27
28 CBS_dup(header, &cbs);
29
30 if (!CBS_get_u16(&cbs, &record_length) ||
31 !CBS_get_u8(&cbs, &message_type))
32 return 0;
33
34 /*
35 * The SSLv2 record length field uses variable length (2 or 3 byte)
36 * encoding. Given the size of a client hello, we expect/require the
37 * 2-byte form which is indicated by a one in the most significant bit.
38 */
39 if ((record_length & 0x8000) == 0)
40 return 0;
41 if ((record_length & ~0x8000) < 3)
42 return 0;
43 if (message_type != SSL2_MT_CLIENT_HELLO)
44 return 0;
45
46 return 1;
47 }
48
49 static int
ssl_is_sslv3_handshake(CBS * header)50 ssl_is_sslv3_handshake(CBS *header)
51 {
52 uint16_t record_version;
53 uint8_t record_type;
54 CBS cbs;
55
56 CBS_dup(header, &cbs);
57
58 if (!CBS_get_u8(&cbs, &record_type) ||
59 !CBS_get_u16(&cbs, &record_version))
60 return 0;
61
62 if (record_type != SSL3_RT_HANDSHAKE)
63 return 0;
64 if ((record_version >> 8) != SSL3_VERSION_MAJOR)
65 return 0;
66
67 return 1;
68 }
69
70 static int
ssl_convert_sslv2_client_hello(SSL * s)71 ssl_convert_sslv2_client_hello(SSL *s)
72 {
73 CBB cbb, handshake, client_hello, cipher_suites, compression, session_id;
74 CBS cbs, challenge, cipher_specs, session;
75 uint16_t record_length, client_version, cipher_specs_length;
76 uint16_t session_id_length, challenge_length;
77 unsigned char *client_random = NULL, *data = NULL;
78 size_t data_len, pad_len, len;
79 uint32_t cipher_spec;
80 uint8_t message_type;
81 unsigned char *pad;
82 int ret = -1;
83 int n;
84
85 memset(&cbb, 0, sizeof(cbb));
86
87 CBS_init(&cbs, s->packet, SSL3_RT_HEADER_LENGTH);
88
89 if (!CBS_get_u16(&cbs, &record_length) ||
90 !CBS_get_u8(&cbs, &message_type) ||
91 !CBS_get_u16(&cbs, &client_version))
92 return -1;
93
94 /*
95 * The SSLv2 record length field uses variable length (2 or 3 byte)
96 * encoding. Given the size of a client hello, we expect/require the
97 * 2-byte form which is indicated by a one in the most significant bit.
98 * Also note that the record length value does not include the bytes
99 * used for the record length field.
100 */
101 if ((record_length & 0x8000) == 0)
102 return -1;
103 record_length &= ~0x8000;
104 if (record_length < SSL3_RT_HEADER_LENGTH - 2)
105 return -1;
106 if (message_type != SSL2_MT_CLIENT_HELLO)
107 return -1;
108
109 if (record_length < 9) {
110 SSLerror(s, SSL_R_RECORD_LENGTH_MISMATCH);
111 return -1;
112 }
113 if (record_length > 4096) {
114 SSLerror(s, SSL_R_RECORD_TOO_LARGE);
115 return -1;
116 }
117
118 n = ssl3_packet_extend(s, record_length + 2);
119 if (n != record_length + 2)
120 return n;
121
122 tls1_transcript_record(s, s->packet + 2,
123 s->packet_length - 2);
124 s->mac_packet = 0;
125
126 if (s->msg_callback)
127 s->msg_callback(0, SSL2_VERSION, 0,
128 s->packet + 2, s->packet_length - 2, s,
129 s->msg_callback_arg);
130
131 /* Decode the SSLv2 record containing the client hello. */
132 CBS_init(&cbs, s->packet, s->packet_length);
133
134 if (!CBS_get_u16(&cbs, &record_length))
135 return -1;
136 if (!CBS_get_u8(&cbs, &message_type))
137 return -1;
138 if (!CBS_get_u16(&cbs, &client_version))
139 return -1;
140 if (!CBS_get_u16(&cbs, &cipher_specs_length))
141 return -1;
142 if (!CBS_get_u16(&cbs, &session_id_length))
143 return -1;
144 if (!CBS_get_u16(&cbs, &challenge_length))
145 return -1;
146 if (!CBS_get_bytes(&cbs, &cipher_specs, cipher_specs_length))
147 return -1;
148 if (!CBS_get_bytes(&cbs, &session, session_id_length))
149 return -1;
150 if (!CBS_get_bytes(&cbs, &challenge, challenge_length))
151 return -1;
152 if (CBS_len(&cbs) != 0) {
153 SSLerror(s, SSL_R_RECORD_LENGTH_MISMATCH);
154 return -1;
155 }
156
157 /*
158 * Convert SSLv2 challenge to SSLv3/TLS client random, by truncating or
159 * left-padding with zero bytes.
160 */
161 if ((client_random = malloc(SSL3_RANDOM_SIZE)) == NULL)
162 goto err;
163 if (!CBB_init_fixed(&cbb, client_random, SSL3_RANDOM_SIZE))
164 goto err;
165 if ((len = CBS_len(&challenge)) > SSL3_RANDOM_SIZE)
166 len = SSL3_RANDOM_SIZE;
167 pad_len = SSL3_RANDOM_SIZE - len;
168 if (!CBB_add_space(&cbb, &pad, pad_len))
169 goto err;
170 memset(pad, 0, pad_len);
171 if (!CBB_add_bytes(&cbb, CBS_data(&challenge), len))
172 goto err;
173 if (!CBB_finish(&cbb, NULL, NULL))
174 goto err;
175
176 /* Build SSLv3/TLS record with client hello. */
177 if (!CBB_init(&cbb, SSL3_RT_MAX_PLAIN_LENGTH))
178 goto err;
179 if (!CBB_add_u8(&cbb, SSL3_RT_HANDSHAKE))
180 goto err;
181 if (!CBB_add_u16(&cbb, 0x0301))
182 goto err;
183 if (!CBB_add_u16_length_prefixed(&cbb, &handshake))
184 goto err;
185 if (!CBB_add_u8(&handshake, SSL3_MT_CLIENT_HELLO))
186 goto err;
187 if (!CBB_add_u24_length_prefixed(&handshake, &client_hello))
188 goto err;
189 if (!CBB_add_u16(&client_hello, client_version))
190 goto err;
191 if (!CBB_add_bytes(&client_hello, client_random, SSL3_RANDOM_SIZE))
192 goto err;
193 if (!CBB_add_u8_length_prefixed(&client_hello, &session_id))
194 goto err;
195 if (!CBB_add_u16_length_prefixed(&client_hello, &cipher_suites))
196 goto err;
197 while (CBS_len(&cipher_specs) > 0) {
198 if (!CBS_get_u24(&cipher_specs, &cipher_spec))
199 goto err;
200 if ((cipher_spec & 0xff0000) != 0)
201 continue;
202 if (!CBB_add_u16(&cipher_suites, cipher_spec & 0xffff))
203 goto err;
204 }
205 if (!CBB_add_u8_length_prefixed(&client_hello, &compression))
206 goto err;
207 if (!CBB_add_u8(&compression, 0))
208 goto err;
209 if (!CBB_finish(&cbb, &data, &data_len))
210 goto err;
211
212 if (data_len > s->s3->rbuf.len)
213 goto err;
214
215 s->packet = s->s3->rbuf.buf;
216 s->packet_length = data_len;
217 memcpy(s->packet, data, data_len);
218 ret = 1;
219
220 err:
221 CBB_cleanup(&cbb);
222 free(client_random);
223 free(data);
224
225 return (ret);
226 }
227
228 /*
229 * Potentially do legacy processing on the first packet received by a TLS
230 * server. We return 1 if we want SSLv3/TLS record processing to continue
231 * normally, otherwise we must set an SSLerr and return -1.
232 */
233 int
ssl_server_legacy_first_packet(SSL * s)234 ssl_server_legacy_first_packet(SSL *s)
235 {
236 uint16_t min_version;
237 const char *data;
238 CBS header;
239
240 if (SSL_is_dtls(s))
241 return 1;
242
243 CBS_init(&header, s->packet, SSL3_RT_HEADER_LENGTH);
244
245 if (ssl_is_sslv3_handshake(&header) == 1)
246 return 1;
247
248 /* Only continue if this is not a version locked method. */
249 if (s->method->min_tls_version == s->method->max_tls_version)
250 return 1;
251
252 if (ssl_is_sslv2_client_hello(&header) == 1) {
253 /* Only permit SSLv2 client hellos if TLSv1.0 is enabled. */
254 if (ssl_enabled_tls_version_range(s, &min_version, NULL) != 1) {
255 SSLerror(s, SSL_R_NO_PROTOCOLS_AVAILABLE);
256 return -1;
257 }
258 if (min_version > TLS1_VERSION)
259 return 1;
260
261 if (ssl_convert_sslv2_client_hello(s) != 1) {
262 SSLerror(s, SSL_R_BAD_PACKET_LENGTH);
263 return -1;
264 }
265
266 return 1;
267 }
268
269 /* Ensure that we have SSL3_RT_HEADER_LENGTH (5 bytes) of the packet. */
270 if (CBS_len(&header) != SSL3_RT_HEADER_LENGTH) {
271 SSLerror(s, ERR_R_INTERNAL_ERROR);
272 return -1;
273 }
274 data = (const char *)CBS_data(&header);
275
276 /* Is this a cleartext protocol? */
277 if (strncmp("GET ", data, 4) == 0 ||
278 strncmp("POST ", data, 5) == 0 ||
279 strncmp("HEAD ", data, 5) == 0 ||
280 strncmp("PUT ", data, 4) == 0) {
281 SSLerror(s, SSL_R_HTTP_REQUEST);
282 return -1;
283 }
284 if (strncmp("CONNE", data, 5) == 0) {
285 SSLerror(s, SSL_R_HTTPS_PROXY_REQUEST);
286 return -1;
287 }
288
289 SSLerror(s, SSL_R_UNKNOWN_PROTOCOL);
290
291 return -1;
292 }
293