1 /* $OpenBSD: compress.c,v 1.26 2010/09/08 04:13:31 deraadt 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 * Interface to packet compression for ssh.
7 *
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose. Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
13 */
14
15 #include "includes.h"
16
17 #include <sys/types.h>
18
19 #include <stdarg.h>
20
21 #include "log.h"
22 #include "buffer.h"
23 #include "compress.h"
24
25 #include <zlib.h>
26
27 z_stream incoming_stream;
28 z_stream outgoing_stream;
29 static int compress_init_send_called = 0;
30 static int compress_init_recv_called = 0;
31 static int inflate_failed = 0;
32 static int deflate_failed = 0;
33
34 /*
35 * Initializes compression; level is compression level from 1 to 9
36 * (as in gzip).
37 */
38
39 void
buffer_compress_init_send(int level)40 buffer_compress_init_send(int level)
41 {
42 if (compress_init_send_called == 1)
43 deflateEnd(&outgoing_stream);
44 compress_init_send_called = 1;
45 debug("Enabling compression at level %d.", level);
46 if (level < 1 || level > 9)
47 fatal("Bad compression level %d.", level);
48 deflateInit(&outgoing_stream, level);
49 }
50 void
buffer_compress_init_recv(void)51 buffer_compress_init_recv(void)
52 {
53 if (compress_init_recv_called == 1)
54 inflateEnd(&incoming_stream);
55 compress_init_recv_called = 1;
56 inflateInit(&incoming_stream);
57 }
58
59 /* Frees any data structures allocated for compression. */
60
61 void
buffer_compress_uninit(void)62 buffer_compress_uninit(void)
63 {
64 debug("compress outgoing: raw data %llu, compressed %llu, factor %.2f",
65 (unsigned long long)outgoing_stream.total_in,
66 (unsigned long long)outgoing_stream.total_out,
67 outgoing_stream.total_in == 0 ? 0.0 :
68 (double) outgoing_stream.total_out / outgoing_stream.total_in);
69 debug("compress incoming: raw data %llu, compressed %llu, factor %.2f",
70 (unsigned long long)incoming_stream.total_out,
71 (unsigned long long)incoming_stream.total_in,
72 incoming_stream.total_out == 0 ? 0.0 :
73 (double) incoming_stream.total_in / incoming_stream.total_out);
74 if (compress_init_recv_called == 1 && inflate_failed == 0)
75 inflateEnd(&incoming_stream);
76 if (compress_init_send_called == 1 && deflate_failed == 0)
77 deflateEnd(&outgoing_stream);
78 }
79
80 /*
81 * Compresses the contents of input_buffer into output_buffer. All packets
82 * compressed using this function will form a single compressed data stream;
83 * however, data will be flushed at the end of every call so that each
84 * output_buffer can be decompressed independently (but in the appropriate
85 * order since they together form a single compression stream) by the
86 * receiver. This appends the compressed data to the output buffer.
87 */
88
89 void
buffer_compress(Buffer * input_buffer,Buffer * output_buffer)90 buffer_compress(Buffer * input_buffer, Buffer * output_buffer)
91 {
92 u_char buf[4096];
93 int status;
94
95 /* This case is not handled below. */
96 if (buffer_len(input_buffer) == 0)
97 return;
98
99 /* Input is the contents of the input buffer. */
100 outgoing_stream.next_in = buffer_ptr(input_buffer);
101 outgoing_stream.avail_in = buffer_len(input_buffer);
102
103 /* Loop compressing until deflate() returns with avail_out != 0. */
104 do {
105 /* Set up fixed-size output buffer. */
106 outgoing_stream.next_out = buf;
107 outgoing_stream.avail_out = sizeof(buf);
108
109 /* Compress as much data into the buffer as possible. */
110 status = deflate(&outgoing_stream, Z_PARTIAL_FLUSH);
111 switch (status) {
112 case Z_OK:
113 /* Append compressed data to output_buffer. */
114 buffer_append(output_buffer, buf,
115 sizeof(buf) - outgoing_stream.avail_out);
116 break;
117 default:
118 deflate_failed = 1;
119 fatal("buffer_compress: deflate returned %d", status);
120 /* NOTREACHED */
121 }
122 } while (outgoing_stream.avail_out == 0);
123 }
124
125 /*
126 * Uncompresses the contents of input_buffer into output_buffer. All packets
127 * uncompressed using this function will form a single compressed data
128 * stream; however, data will be flushed at the end of every call so that
129 * each output_buffer. This must be called for the same size units that the
130 * buffer_compress was called, and in the same order that buffers compressed
131 * with that. This appends the uncompressed data to the output buffer.
132 */
133
134 void
buffer_uncompress(Buffer * input_buffer,Buffer * output_buffer)135 buffer_uncompress(Buffer * input_buffer, Buffer * output_buffer)
136 {
137 u_char buf[4096];
138 int status;
139
140 incoming_stream.next_in = buffer_ptr(input_buffer);
141 incoming_stream.avail_in = buffer_len(input_buffer);
142
143 for (;;) {
144 /* Set up fixed-size output buffer. */
145 incoming_stream.next_out = buf;
146 incoming_stream.avail_out = sizeof(buf);
147
148 status = inflate(&incoming_stream, Z_PARTIAL_FLUSH);
149 switch (status) {
150 case Z_OK:
151 buffer_append(output_buffer, buf,
152 sizeof(buf) - incoming_stream.avail_out);
153 break;
154 case Z_BUF_ERROR:
155 /*
156 * Comments in zlib.h say that we should keep calling
157 * inflate() until we get an error. This appears to
158 * be the error that we get.
159 */
160 return;
161 default:
162 inflate_failed = 1;
163 fatal("buffer_uncompress: inflate returned %d", status);
164 /* NOTREACHED */
165 }
166 }
167 }
168