1 /*
2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4 * All rights reserved
5 * Functions for manipulating fifo buffers (that can grow if needed).
6 *
7 * As far as I am concerned, the code I have written for this software
8 * can be used freely for any purpose. Any derived versions of this
9 * software must be clearly marked as such, and if the derived work is
10 * incompatible with the protocol description in the RFC file, it must be
11 * called by a name other than "ssh" or "Secure Shell".
12 */
13 /*
14 * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
15 * Use is subject to license terms.
16 */
17
18 /* $OpenBSD: buffer.c,v 1.31 2006/08/03 03:34:41 deraadt Exp $ */
19
20 #include "includes.h"
21
22 #include "xmalloc.h"
23 #include "buffer.h"
24 #include "log.h"
25
26 #define BUFFER_MAX_CHUNK 0x100000
27 #define BUFFER_MAX_LEN 0xa00000
28 #define BUFFER_ALLOCSZ 0x008000
29
30 /* Initializes the buffer structure. */
31
32 void
33 buffer_init(Buffer *buffer)
34 {
35 const u_int len = 4096;
36
37 buffer->alloc = 0;
38 buffer->buf = xmalloc(len);
39 buffer->alloc = len;
40 buffer->offset = 0;
41 buffer->end = 0;
42 }
43
44 /* Frees any memory used for the buffer. */
45
46 void
47 buffer_free(Buffer *buffer)
48 {
49 if (buffer->alloc > 0) {
50 memset(buffer->buf, 0, buffer->alloc);
51 buffer->alloc = 0;
52 xfree(buffer->buf);
53 }
54 }
55
56 /*
57 * Clears any data from the buffer, making it empty. This does not actually
58 * zero the memory.
59 */
60
61 void
62 buffer_clear(Buffer *buffer)
63 {
64 buffer->offset = 0;
65 buffer->end = 0;
66 }
67
68 /* Appends data to the buffer, expanding it if necessary. */
69
70 void
71 buffer_append(Buffer *buffer, const void *data, u_int len)
72 {
73 void *p;
74 p = buffer_append_space(buffer, len);
75 memcpy(p, data, len);
76 }
77
78 static int
79 buffer_compact(Buffer *buffer)
80 {
81 /*
82 * If the buffer is quite empty, but all data is at the end, move the
83 * data to the beginning.
84 */
85 if (buffer->offset > MIN(buffer->alloc, BUFFER_MAX_CHUNK)) {
86 memmove(buffer->buf, buffer->buf + buffer->offset,
87 buffer->end - buffer->offset);
88 buffer->end -= buffer->offset;
89 buffer->offset = 0;
90 return (1);
91 }
92 return (0);
93 }
94
95 /*
96 * Appends space to the buffer, expanding the buffer if necessary. This does
97 * not actually copy the data into the buffer, but instead returns a pointer
98 * to the allocated region.
99 */
100
101 void *
102 buffer_append_space(Buffer *buffer, u_int len)
103 {
104 u_int newlen;
105 void *p;
106
107 if (len > BUFFER_MAX_CHUNK)
108 fatal("buffer_append_space: len %u not supported", len);
109
110 /* If the buffer is empty, start using it from the beginning. */
111 if (buffer->offset == buffer->end) {
112 buffer->offset = 0;
113 buffer->end = 0;
114 }
115 restart:
116 /* If there is enough space to store all data, store it now. */
117 if (buffer->end + len < buffer->alloc) {
118 p = buffer->buf + buffer->end;
119 buffer->end += len;
120 return p;
121 }
122
123 /* Compact data back to the start of the buffer if necessary */
124 if (buffer_compact(buffer))
125 goto restart;
126
127 /* Increase the size of the buffer and retry. */
128 newlen = roundup(buffer->alloc + len, BUFFER_ALLOCSZ);
129 if (newlen > BUFFER_MAX_LEN)
130 fatal("buffer_append_space: alloc %u not supported",
131 newlen);
132 buffer->buf = xrealloc(buffer->buf, newlen);
133 buffer->alloc = newlen;
134 goto restart;
135 /* NOTREACHED */
136 }
137
138 /*
139 * Check whether an allocation of 'len' will fit in the buffer
140 * This must follow the same math as buffer_append_space
141 */
142 int
143 buffer_check_alloc(Buffer *buffer, u_int len)
144 {
145 if (buffer->offset == buffer->end) {
146 buffer->offset = 0;
147 buffer->end = 0;
148 }
149 restart:
150 if (buffer->end + len < buffer->alloc)
151 return (1);
152 if (buffer_compact(buffer))
153 goto restart;
154 if (roundup(buffer->alloc + len, BUFFER_ALLOCSZ) <= BUFFER_MAX_LEN)
155 return (1);
156 return (0);
157 }
158
159 /* Returns the number of bytes of data in the buffer. */
160
161 u_int
162 buffer_len(Buffer *buffer)
163 {
164 return buffer->end - buffer->offset;
165 }
166
167 /* Gets data from the beginning of the buffer. */
168
169 int
170 buffer_get_ret(Buffer *buffer, void *buf, u_int len)
171 {
172 if (len > buffer->end - buffer->offset) {
173 error("buffer_get_ret: trying to get more bytes %d than in buffer %d",
174 len, buffer->end - buffer->offset);
175 return (-1);
176 }
177 memcpy(buf, buffer->buf + buffer->offset, len);
178 buffer->offset += len;
179 return (0);
180 }
181
182 void
183 buffer_get(Buffer *buffer, void *buf, u_int len)
184 {
185 if (buffer_get_ret(buffer, buf, len) == -1)
186 fatal("buffer_get: buffer error");
187 }
188
189 /* Consumes the given number of bytes from the beginning of the buffer. */
190
191 int
192 buffer_consume_ret(Buffer *buffer, u_int bytes)
193 {
194 if (bytes > buffer->end - buffer->offset) {
195 error("buffer_consume_ret: trying to get more bytes than in buffer");
196 return (-1);
197 }
198 buffer->offset += bytes;
199 return (0);
200 }
201
202 void
203 buffer_consume(Buffer *buffer, u_int bytes)
204 {
205 if (buffer_consume_ret(buffer, bytes) == -1)
206 fatal("buffer_consume: buffer error");
207 }
208
209 /* Consumes the given number of bytes from the end of the buffer. */
210
211 int
212 buffer_consume_end_ret(Buffer *buffer, u_int bytes)
213 {
214 if (bytes > buffer->end - buffer->offset)
215 return (-1);
216 buffer->end -= bytes;
217 return (0);
218 }
219
220 void
221 buffer_consume_end(Buffer *buffer, u_int bytes)
222 {
223 if (buffer_consume_end_ret(buffer, bytes) == -1)
224 fatal("buffer_consume_end: trying to get more bytes than in buffer");
225 }
226
227 /* Returns a pointer to the first used byte in the buffer. */
228
229 void *
230 buffer_ptr(Buffer *buffer)
231 {
232 return buffer->buf + buffer->offset;
233 }
234
235 /* Dumps the contents of the buffer to stderr. */
236 void
237 buffer_dump(Buffer *buffer)
238 {
239 u_int i;
240 u_char *ucp = buffer->buf;
241
242 for (i = buffer->offset; i < buffer->end; i++) {
243 fprintf(stderr, "%02x", ucp[i]);
244 if ((i-buffer->offset)%16==15)
245 fprintf(stderr, "\n");
246 else if ((i-buffer->offset)%2==1)
247 fprintf(stderr, " ");
248 }
249
250 if (buffer->offset == buffer->end) {
251 /* explicitly state when the buffer is empty */
252 fprintf(stderr, "<EMPTY BUFFER>\n");
253 } else {
254 /* print the terminal '\n' if it wasn't already printed */
255 if ((i - buffer->offset) % 16 != 0)
256 fprintf(stderr, "\n");
257 }
258 /*
259 * We want an extra empty line after the packet dump for better
260 * readability.
261 */
262 fprintf(stderr, "\n");
263 }