1 /* Copyright (c) 2015, Google Inc.
2  *
3  * Permission to use, copy, modify, and/or distribute this software for any
4  * purpose with or without fee is hereby granted, provided that the above
5  * copyright notice and this permission notice appear in all copies.
6  *
7  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10  * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
14 
15 #include <openssl/ssl.h>
16 
17 #include <assert.h>
18 #include <limits.h>
19 #include <stdlib.h>
20 #include <string.h>
21 
22 #include <openssl/bio.h>
23 #include <openssl/err.h>
24 #include <openssl/mem.h>
25 #include <openssl/type_check.h>
26 
27 #include "internal.h"
28 
29 
30 OPENSSL_COMPILE_ASSERT(0xffff <= INT_MAX, uint16_fits_in_int);
31 
32 OPENSSL_COMPILE_ASSERT((SSL3_ALIGN_PAYLOAD & (SSL3_ALIGN_PAYLOAD - 1)) == 0,
33                        align_to_a_power_of_two);
34 
35 /* setup_buffer initializes |buf| with capacity |cap|, aligned such that data
36  * written after |header_len| is aligned to a |SSL3_ALIGN_PAYLOAD|-byte
37  * boundary. It returns one on success and zero on error. */
setup_buffer(SSL3_BUFFER * buf,size_t header_len,size_t cap)38 static int setup_buffer(SSL3_BUFFER *buf, size_t header_len, size_t cap) {
39   if (buf->buf != NULL || cap > 0xffff) {
40     OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
41     return 0;
42   }
43 
44   /* Add up to |SSL3_ALIGN_PAYLOAD| - 1 bytes of slack for alignment. */
45   buf->buf = OPENSSL_malloc(cap + SSL3_ALIGN_PAYLOAD - 1);
46   if (buf->buf == NULL) {
47     OPENSSL_PUT_ERROR(SSL, ERR_R_MALLOC_FAILURE);
48     return 0;
49   }
50 
51   /* Arrange the buffer such that the record body is aligned. */
52   buf->offset = (0 - header_len - (uintptr_t)buf->buf) &
53                 (SSL3_ALIGN_PAYLOAD - 1);
54   buf->len = 0;
55   buf->cap = cap;
56   return 1;
57 }
58 
consume_buffer(SSL3_BUFFER * buf,size_t len)59 static void consume_buffer(SSL3_BUFFER *buf, size_t len) {
60   if (len > buf->len) {
61     abort();
62   }
63   buf->offset += (uint16_t)len;
64   buf->len -= (uint16_t)len;
65   buf->cap -= (uint16_t)len;
66 }
67 
clear_buffer(SSL3_BUFFER * buf)68 static void clear_buffer(SSL3_BUFFER *buf) {
69   OPENSSL_free(buf->buf);
70   memset(buf, 0, sizeof(SSL3_BUFFER));
71 }
72 
73 OPENSSL_COMPILE_ASSERT(DTLS1_RT_HEADER_LENGTH + SSL3_RT_MAX_ENCRYPTED_LENGTH <=
74                            0xffff,
75                        maximum_read_buffer_too_large);
76 
77 /* setup_read_buffer initializes the read buffer if not already initialized. It
78  * returns one on success and zero on failure. */
setup_read_buffer(SSL * ssl)79 static int setup_read_buffer(SSL *ssl) {
80   SSL3_BUFFER *buf = &ssl->s3->read_buffer;
81 
82   if (buf->buf != NULL) {
83     return 1;
84   }
85 
86   size_t header_len = ssl_record_prefix_len(ssl);
87   size_t cap = SSL3_RT_MAX_ENCRYPTED_LENGTH;
88   if (SSL_IS_DTLS(ssl)) {
89     cap += DTLS1_RT_HEADER_LENGTH;
90   } else {
91     cap += SSL3_RT_HEADER_LENGTH;
92   }
93 
94   return setup_buffer(buf, header_len, cap);
95 }
96 
ssl_read_buffer(SSL * ssl)97 uint8_t *ssl_read_buffer(SSL *ssl) {
98   return ssl->s3->read_buffer.buf + ssl->s3->read_buffer.offset;
99 }
100 
ssl_read_buffer_len(const SSL * ssl)101 size_t ssl_read_buffer_len(const SSL *ssl) {
102   return ssl->s3->read_buffer.len;
103 }
104 
dtls_read_buffer_next_packet(SSL * ssl)105 static int dtls_read_buffer_next_packet(SSL *ssl) {
106   SSL3_BUFFER *buf = &ssl->s3->read_buffer;
107 
108   if (buf->len > 0) {
109     /* It is an error to call |dtls_read_buffer_extend| when the read buffer is
110      * not empty. */
111     OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
112     return -1;
113   }
114 
115   /* Read a single packet from |ssl->rbio|. |buf->cap| must fit in an int. */
116   ssl->rwstate = SSL_READING;
117   int ret = BIO_read(ssl->rbio, buf->buf + buf->offset, (int)buf->cap);
118   if (ret <= 0) {
119     return ret;
120   }
121   ssl->rwstate = SSL_NOTHING;
122   /* |BIO_read| was bound by |buf->cap|, so this cannot overflow. */
123   buf->len = (uint16_t)ret;
124   return 1;
125 }
126 
tls_read_buffer_extend_to(SSL * ssl,size_t len)127 static int tls_read_buffer_extend_to(SSL *ssl, size_t len) {
128   SSL3_BUFFER *buf = &ssl->s3->read_buffer;
129 
130   if (len > buf->cap) {
131     OPENSSL_PUT_ERROR(SSL, SSL_R_BUFFER_TOO_SMALL);
132     return -1;
133   }
134 
135   /* Read until the target length is reached. */
136   while (buf->len < len) {
137     /* The amount of data to read is bounded by |buf->cap|, which must fit in an
138      * int. */
139     ssl->rwstate = SSL_READING;
140     int ret = BIO_read(ssl->rbio, buf->buf + buf->offset + buf->len,
141                        (int)(len - buf->len));
142     if (ret <= 0) {
143       return ret;
144     }
145     ssl->rwstate = SSL_NOTHING;
146     /* |BIO_read| was bound by |buf->cap - buf->len|, so this cannot
147      * overflow. */
148     buf->len += (uint16_t)ret;
149   }
150 
151   return 1;
152 }
153 
ssl_read_buffer_extend_to(SSL * ssl,size_t len)154 int ssl_read_buffer_extend_to(SSL *ssl, size_t len) {
155   /* |ssl_read_buffer_extend_to| implicitly discards any consumed data. */
156   ssl_read_buffer_discard(ssl);
157 
158   if (!setup_read_buffer(ssl)) {
159     return -1;
160   }
161 
162   if (ssl->rbio == NULL) {
163     OPENSSL_PUT_ERROR(SSL, SSL_R_BIO_NOT_SET);
164     return -1;
165   }
166 
167   ERR_clear_system_error();
168 
169   int ret;
170   if (SSL_IS_DTLS(ssl)) {
171     /* |len| is ignored for a datagram transport. */
172     ret = dtls_read_buffer_next_packet(ssl);
173   } else {
174     ret = tls_read_buffer_extend_to(ssl, len);
175   }
176 
177   if (ret <= 0) {
178     /* If the buffer was empty originally and remained empty after attempting to
179      * extend it, release the buffer until the next attempt. */
180     ssl_read_buffer_discard(ssl);
181   }
182   return ret;
183 }
184 
ssl_read_buffer_consume(SSL * ssl,size_t len)185 void ssl_read_buffer_consume(SSL *ssl, size_t len) {
186   SSL3_BUFFER *buf = &ssl->s3->read_buffer;
187 
188   consume_buffer(buf, len);
189   if (!SSL_IS_DTLS(ssl)) {
190     /* The TLS stack never reads beyond the current record, so there will never
191      * be unconsumed data. If read-ahead is ever reimplemented,
192      * |ssl_read_buffer_discard| will require a |memcpy| to shift the excess
193      * back to the front of the buffer, to ensure there is enough space for the
194      * next record. */
195      assert(buf->len == 0);
196   }
197 }
198 
ssl_read_buffer_discard(SSL * ssl)199 void ssl_read_buffer_discard(SSL *ssl) {
200   if (ssl->s3->read_buffer.len == 0) {
201     ssl_read_buffer_clear(ssl);
202   }
203 }
204 
ssl_read_buffer_clear(SSL * ssl)205 void ssl_read_buffer_clear(SSL *ssl) {
206   clear_buffer(&ssl->s3->read_buffer);
207 }
208 
209 
ssl_write_buffer_is_pending(const SSL * ssl)210 int ssl_write_buffer_is_pending(const SSL *ssl) {
211   return ssl->s3->write_buffer.len > 0;
212 }
213 
214 OPENSSL_COMPILE_ASSERT(SSL3_RT_HEADER_LENGTH * 2 +
215                            SSL3_RT_SEND_MAX_ENCRYPTED_OVERHEAD * 2 +
216                            SSL3_RT_MAX_PLAIN_LENGTH <= 0xffff,
217                        maximum_tls_write_buffer_too_large);
218 
219 OPENSSL_COMPILE_ASSERT(DTLS1_RT_HEADER_LENGTH +
220                            SSL3_RT_SEND_MAX_ENCRYPTED_OVERHEAD +
221                            SSL3_RT_MAX_PLAIN_LENGTH <= 0xffff,
222                        maximum_dtls_write_buffer_too_large);
223 
ssl_write_buffer_init(SSL * ssl,uint8_t ** out_ptr,size_t max_len)224 int ssl_write_buffer_init(SSL *ssl, uint8_t **out_ptr, size_t max_len) {
225   SSL3_BUFFER *buf = &ssl->s3->write_buffer;
226 
227   if (buf->buf != NULL) {
228     OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
229     return 0;
230   }
231 
232   size_t header_len = ssl_seal_prefix_len(ssl);
233 
234   /* TODO(davidben): This matches the original behavior in keeping the malloc
235    * size consistent. Does this matter? |cap| could just be |max_len|. */
236   size_t cap = SSL3_RT_MAX_PLAIN_LENGTH + SSL3_RT_SEND_MAX_ENCRYPTED_OVERHEAD;
237   if (SSL_IS_DTLS(ssl)) {
238     cap += DTLS1_RT_HEADER_LENGTH;
239   } else {
240     cap += SSL3_RT_HEADER_LENGTH;
241     if (ssl->mode & SSL_MODE_CBC_RECORD_SPLITTING) {
242       cap += SSL3_RT_HEADER_LENGTH + SSL3_RT_SEND_MAX_ENCRYPTED_OVERHEAD;
243     }
244   }
245 
246   if (max_len > cap) {
247     OPENSSL_PUT_ERROR(SSL, SSL_R_BUFFER_TOO_SMALL);
248     return 0;
249   }
250 
251   if (!setup_buffer(buf, header_len, cap)) {
252     return 0;
253   }
254   *out_ptr = buf->buf + buf->offset;
255   return 1;
256 }
257 
ssl_write_buffer_set_len(SSL * ssl,size_t len)258 void ssl_write_buffer_set_len(SSL *ssl, size_t len) {
259   SSL3_BUFFER *buf = &ssl->s3->write_buffer;
260 
261   if (len > buf->cap) {
262     abort();
263   }
264   buf->len = len;
265 }
266 
tls_write_buffer_flush(SSL * ssl)267 static int tls_write_buffer_flush(SSL *ssl) {
268   SSL3_BUFFER *buf = &ssl->s3->write_buffer;
269 
270   while (buf->len > 0) {
271     ssl->rwstate = SSL_WRITING;
272     int ret = BIO_write(ssl->wbio, buf->buf + buf->offset, buf->len);
273     if (ret <= 0) {
274       return ret;
275     }
276     ssl->rwstate = SSL_NOTHING;
277     consume_buffer(buf, (size_t)ret);
278   }
279   ssl_write_buffer_clear(ssl);
280   return 1;
281 }
282 
dtls_write_buffer_flush(SSL * ssl)283 static int dtls_write_buffer_flush(SSL *ssl) {
284   SSL3_BUFFER *buf = &ssl->s3->write_buffer;
285   if (buf->len == 0) {
286     return 1;
287   }
288 
289   ssl->rwstate = SSL_WRITING;
290   int ret = BIO_write(ssl->wbio, buf->buf + buf->offset, buf->len);
291   if (ret <= 0) {
292     /* If the write failed, drop the write buffer anyway. Datagram transports
293      * can't write half a packet, so the caller is expected to retry from the
294      * top. */
295     ssl_write_buffer_clear(ssl);
296     return ret;
297   }
298   ssl->rwstate = SSL_NOTHING;
299   ssl_write_buffer_clear(ssl);
300   return 1;
301 }
302 
ssl_write_buffer_flush(SSL * ssl)303 int ssl_write_buffer_flush(SSL *ssl) {
304   if (ssl->wbio == NULL) {
305     OPENSSL_PUT_ERROR(SSL, SSL_R_BIO_NOT_SET);
306     return -1;
307   }
308   ERR_clear_system_error();
309 
310   if (SSL_IS_DTLS(ssl)) {
311     return dtls_write_buffer_flush(ssl);
312   } else {
313     return tls_write_buffer_flush(ssl);
314   }
315 }
316 
ssl_write_buffer_clear(SSL * ssl)317 void ssl_write_buffer_clear(SSL *ssl) {
318   clear_buffer(&ssl->s3->write_buffer);
319 }
320