bufaux.c revision 294666 
1/* $OpenBSD: bufaux.c,v 1.57 2014/04/16 23:22:45 djm Exp $ */
2/*
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 *                    All rights reserved
6 * Auxiliary functions for storing and retrieving various data types to/from
7 * Buffers.
8 *
9 * As far as I am concerned, the code I have written for this software
10 * can be used freely for any purpose.  Any derived versions of this
11 * software must be clearly marked as such, and if the derived work is
12 * incompatible with the protocol description in the RFC file, it must be
13 * called by a name other than "ssh" or "Secure Shell".
14 *
15 *
16 * SSH2 packet format added by Markus Friedl
17 * Copyright (c) 2000 Markus Friedl.  All rights reserved.
18 *
19 * Redistribution and use in source and binary forms, with or without
20 * modification, are permitted provided that the following conditions
21 * are met:
22 * 1. Redistributions of source code must retain the above copyright
23 *    notice, this list of conditions and the following disclaimer.
24 * 2. Redistributions in binary form must reproduce the above copyright
25 *    notice, this list of conditions and the following disclaimer in the
26 *    documentation and/or other materials provided with the distribution.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
29 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
31 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
33 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
34 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
35 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
36 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
37 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
38 */
39
40#include "includes.h"
41__RCSID("$FreeBSD: stable/10/crypto/openssh/bufaux.c 294666 2016-01-24 15:44:57Z des $");
42
43#include <sys/types.h>
44
45#include <openssl/bn.h>
46
47#include <string.h>
48#include <stdarg.h>
49#include <stdlib.h>
50
51#include "xmalloc.h"
52#include "buffer.h"
53#include "log.h"
54#include "misc.h"
55
56/*
57 * Returns integers from the buffer (msb first).
58 */
59
60int
61buffer_get_short_ret(u_short *ret, Buffer *buffer)
62{
63	u_char buf[2];
64
65	if (buffer_get_ret(buffer, (char *) buf, 2) == -1)
66		return (-1);
67	*ret = get_u16(buf);
68	return (0);
69}
70
71u_short
72buffer_get_short(Buffer *buffer)
73{
74	u_short ret;
75
76	if (buffer_get_short_ret(&ret, buffer) == -1)
77		fatal("buffer_get_short: buffer error");
78
79	return (ret);
80}
81
82int
83buffer_get_int_ret(u_int *ret, Buffer *buffer)
84{
85	u_char buf[4];
86
87	if (buffer_get_ret(buffer, (char *) buf, 4) == -1)
88		return (-1);
89	if (ret != NULL)
90		*ret = get_u32(buf);
91	return (0);
92}
93
94u_int
95buffer_get_int(Buffer *buffer)
96{
97	u_int ret;
98
99	if (buffer_get_int_ret(&ret, buffer) == -1)
100		fatal("buffer_get_int: buffer error");
101
102	return (ret);
103}
104
105int
106buffer_get_int64_ret(u_int64_t *ret, Buffer *buffer)
107{
108	u_char buf[8];
109
110	if (buffer_get_ret(buffer, (char *) buf, 8) == -1)
111		return (-1);
112	if (ret != NULL)
113		*ret = get_u64(buf);
114	return (0);
115}
116
117u_int64_t
118buffer_get_int64(Buffer *buffer)
119{
120	u_int64_t ret;
121
122	if (buffer_get_int64_ret(&ret, buffer) == -1)
123		fatal("buffer_get_int: buffer error");
124
125	return (ret);
126}
127
128/*
129 * Stores integers in the buffer, msb first.
130 */
131void
132buffer_put_short(Buffer *buffer, u_short value)
133{
134	char buf[2];
135
136	put_u16(buf, value);
137	buffer_append(buffer, buf, 2);
138}
139
140void
141buffer_put_int(Buffer *buffer, u_int value)
142{
143	char buf[4];
144
145	put_u32(buf, value);
146	buffer_append(buffer, buf, 4);
147}
148
149void
150buffer_put_int64(Buffer *buffer, u_int64_t value)
151{
152	char buf[8];
153
154	put_u64(buf, value);
155	buffer_append(buffer, buf, 8);
156}
157
158/*
159 * Returns an arbitrary binary string from the buffer.  The string cannot
160 * be longer than 256k.  The returned value points to memory allocated
161 * with xmalloc; it is the responsibility of the calling function to free
162 * the data.  If length_ptr is non-NULL, the length of the returned data
163 * will be stored there.  A null character will be automatically appended
164 * to the returned string, and is not counted in length.
165 */
166void *
167buffer_get_string_ret(Buffer *buffer, u_int *length_ptr)
168{
169	u_char *value;
170	u_int len;
171
172	/* Get the length. */
173	if (buffer_get_int_ret(&len, buffer) != 0) {
174		error("buffer_get_string_ret: cannot extract length");
175		return (NULL);
176	}
177	if (len > 256 * 1024) {
178		error("buffer_get_string_ret: bad string length %u", len);
179		return (NULL);
180	}
181	/* Allocate space for the string.  Add one byte for a null character. */
182	value = xmalloc(len + 1);
183	/* Get the string. */
184	if (buffer_get_ret(buffer, value, len) == -1) {
185		error("buffer_get_string_ret: buffer_get failed");
186		free(value);
187		return (NULL);
188	}
189	/* Append a null character to make processing easier. */
190	value[len] = '\0';
191	/* Optionally return the length of the string. */
192	if (length_ptr)
193		*length_ptr = len;
194	return (value);
195}
196
197void *
198buffer_get_string(Buffer *buffer, u_int *length_ptr)
199{
200	void *ret;
201
202	if ((ret = buffer_get_string_ret(buffer, length_ptr)) == NULL)
203		fatal("buffer_get_string: buffer error");
204	return (ret);
205}
206
207char *
208buffer_get_cstring_ret(Buffer *buffer, u_int *length_ptr)
209{
210	u_int length;
211	char *cp, *ret = buffer_get_string_ret(buffer, &length);
212
213	if (ret == NULL)
214		return NULL;
215	if ((cp = memchr(ret, '\0', length)) != NULL) {
216		/* XXX allow \0 at end-of-string for a while, remove later */
217		if (cp == ret + length - 1)
218			error("buffer_get_cstring_ret: string contains \\0");
219		else {
220			explicit_bzero(ret, length);
221			free(ret);
222			return NULL;
223		}
224	}
225	if (length_ptr != NULL)
226		*length_ptr = length;
227	return ret;
228}
229
230char *
231buffer_get_cstring(Buffer *buffer, u_int *length_ptr)
232{
233	char *ret;
234
235	if ((ret = buffer_get_cstring_ret(buffer, length_ptr)) == NULL)
236		fatal("buffer_get_cstring: buffer error");
237	return ret;
238}
239
240void *
241buffer_get_string_ptr_ret(Buffer *buffer, u_int *length_ptr)
242{
243	void *ptr;
244	u_int len;
245
246	if (buffer_get_int_ret(&len, buffer) != 0)
247		return NULL;
248	if (len > 256 * 1024) {
249		error("buffer_get_string_ptr: bad string length %u", len);
250		return NULL;
251	}
252	ptr = buffer_ptr(buffer);
253	buffer_consume(buffer, len);
254	if (length_ptr)
255		*length_ptr = len;
256	return (ptr);
257}
258
259void *
260buffer_get_string_ptr(Buffer *buffer, u_int *length_ptr)
261{
262	void *ret;
263
264	if ((ret = buffer_get_string_ptr_ret(buffer, length_ptr)) == NULL)
265		fatal("buffer_get_string_ptr: buffer error");
266	return (ret);
267}
268
269/*
270 * Stores and arbitrary binary string in the buffer.
271 */
272void
273buffer_put_string(Buffer *buffer, const void *buf, u_int len)
274{
275	buffer_put_int(buffer, len);
276	buffer_append(buffer, buf, len);
277}
278void
279buffer_put_cstring(Buffer *buffer, const char *s)
280{
281	if (s == NULL)
282		fatal("buffer_put_cstring: s == NULL");
283	buffer_put_string(buffer, s, strlen(s));
284}
285
286/*
287 * Returns a character from the buffer (0 - 255).
288 */
289int
290buffer_get_char_ret(u_char *ret, Buffer *buffer)
291{
292	if (buffer_get_ret(buffer, ret, 1) == -1) {
293		error("buffer_get_char_ret: buffer_get_ret failed");
294		return (-1);
295	}
296	return (0);
297}
298
299int
300buffer_get_char(Buffer *buffer)
301{
302	u_char ch;
303
304	if (buffer_get_char_ret(&ch, buffer) == -1)
305		fatal("buffer_get_char: buffer error");
306	return ch;
307}
308
309/*
310 * Stores a character in the buffer.
311 */
312void
313buffer_put_char(Buffer *buffer, int value)
314{
315	char ch = value;
316
317	buffer_append(buffer, &ch, 1);
318}
319
320/* Pseudo bignum functions */
321
322void *
323buffer_get_bignum2_as_string_ret(Buffer *buffer, u_int *length_ptr)
324{
325	u_int len;
326	u_char *bin, *p, *ret;
327
328	if ((p = bin = buffer_get_string_ret(buffer, &len)) == NULL) {
329		error("%s: invalid bignum", __func__);
330		return NULL;
331	}
332
333	if (len > 0 && (bin[0] & 0x80)) {
334		error("%s: negative numbers not supported", __func__);
335		free(bin);
336		return NULL;
337	}
338	if (len > 8 * 1024) {
339		error("%s: cannot handle BN of size %d", __func__, len);
340		free(bin);
341		return NULL;
342	}
343	/* Skip zero prefix on numbers with the MSB set */
344	if (len > 1 && bin[0] == 0x00 && (bin[1] & 0x80) != 0) {
345		p++;
346		len--;
347	}
348	ret = xmalloc(len);
349	memcpy(ret, p, len);
350	explicit_bzero(p, len);
351	free(bin);
352	return ret;
353}
354
355void *
356buffer_get_bignum2_as_string(Buffer *buffer, u_int *l)
357{
358	void *ret = buffer_get_bignum2_as_string_ret(buffer, l);
359
360	if (ret == NULL)
361		fatal("%s: buffer error", __func__);
362	return ret;
363}
364
365/*
366 * Stores a string using the bignum encoding rules (\0 pad if MSB set).
367 */
368void
369buffer_put_bignum2_from_string(Buffer *buffer, const u_char *s, u_int l)
370{
371	u_char *buf, *p;
372	int pad = 0;
373
374	if (l > 8 * 1024)
375		fatal("%s: length %u too long", __func__, l);
376	/* Skip leading zero bytes */
377	for (; l > 0 && *s == 0; l--, s++)
378		;
379	p = buf = xmalloc(l + 1);
380	/*
381	 * If most significant bit is set then prepend a zero byte to
382	 * avoid interpretation as a negative number.
383	 */
384	if (l > 0 && (s[0] & 0x80) != 0) {
385		*p++ = '\0';
386		pad = 1;
387	}
388	memcpy(p, s, l);
389	buffer_put_string(buffer, buf, l + pad);
390	explicit_bzero(buf, l + pad);
391	free(buf);
392}
393
394
395