1 /* $OpenBSD: compress.c,v 1.25 2006/08/06 01:13:32 stevesk 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 <sys/types.h>
16
17 #include <stdarg.h>
18 #include <zlib.h>
19
20 #include "log.h"
21 #include "buffer.h"
22 #include "compress.h"
23
24 z_stream incoming_stream;
25 z_stream outgoing_stream;
26 static int compress_init_send_called = 0;
27 static int compress_init_recv_called = 0;
28 static int inflate_failed = 0;
29 static int deflate_failed = 0;
30
31 /*
32 * Initializes compression; level is compression level from 1 to 9
33 * (as in gzip).
34 */
35
36 void
buffer_compress_init_send(int level)37 buffer_compress_init_send(int level)
38 {
39 if (compress_init_send_called == 1)
40 deflateEnd(&outgoing_stream);
41 compress_init_send_called = 1;
42 debug("Enabling compression at level %d.", level);
43 if (level < 1 || level > 9)
44 fatal("Bad compression level %d.", level);
45 deflateInit(&outgoing_stream, level);
46 }
47 void
buffer_compress_init_recv(void)48 buffer_compress_init_recv(void)
49 {
50 if (compress_init_recv_called == 1)
51 inflateEnd(&incoming_stream);
52 compress_init_recv_called = 1;
53 inflateInit(&incoming_stream);
54 }
55
56 /* Frees any data structures allocated for compression. */
57
58 void
buffer_compress_uninit(void)59 buffer_compress_uninit(void)
60 {
61 debug("compress outgoing: raw data %llu, compressed %llu, factor %.2f",
62 (unsigned long long)outgoing_stream.total_in,
63 (unsigned long long)outgoing_stream.total_out,
64 outgoing_stream.total_in == 0 ? 0.0 :
65 (double) outgoing_stream.total_out / outgoing_stream.total_in);
66 debug("compress incoming: raw data %llu, compressed %llu, factor %.2f",
67 (unsigned long long)incoming_stream.total_out,
68 (unsigned long long)incoming_stream.total_in,
69 incoming_stream.total_out == 0 ? 0.0 :
70 (double) incoming_stream.total_in / incoming_stream.total_out);
71 if (compress_init_recv_called == 1 && inflate_failed == 0)
72 inflateEnd(&incoming_stream);
73 if (compress_init_send_called == 1 && deflate_failed == 0)
74 deflateEnd(&outgoing_stream);
75 }
76
77 /*
78 * Compresses the contents of input_buffer into output_buffer. All packets
79 * compressed using this function will form a single compressed data stream;
80 * however, data will be flushed at the end of every call so that each
81 * output_buffer can be decompressed independently (but in the appropriate
82 * order since they together form a single compression stream) by the
83 * receiver. This appends the compressed data to the output buffer.
84 */
85
86 void
buffer_compress(Buffer * input_buffer,Buffer * output_buffer)87 buffer_compress(Buffer * input_buffer, Buffer * output_buffer)
88 {
89 u_char buf[4096];
90 int status;
91
92 /* This case is not handled below. */
93 if (buffer_len(input_buffer) == 0)
94 return;
95
96 /* Input is the contents of the input buffer. */
97 outgoing_stream.next_in = buffer_ptr(input_buffer);
98 outgoing_stream.avail_in = buffer_len(input_buffer);
99
100 /* Loop compressing until deflate() returns with avail_out != 0. */
101 do {
102 /* Set up fixed-size output buffer. */
103 outgoing_stream.next_out = buf;
104 outgoing_stream.avail_out = sizeof(buf);
105
106 /* Compress as much data into the buffer as possible. */
107 status = deflate(&outgoing_stream, Z_PARTIAL_FLUSH);
108 switch (status) {
109 case Z_OK:
110 /* Append compressed data to output_buffer. */
111 buffer_append(output_buffer, buf,
112 sizeof(buf) - outgoing_stream.avail_out);
113 break;
114 default:
115 deflate_failed = 1;
116 fatal("buffer_compress: deflate returned %d", status);
117 /* NOTREACHED */
118 }
119 } while (outgoing_stream.avail_out == 0);
120 }
121
122 /*
123 * Uncompresses the contents of input_buffer into output_buffer. All packets
124 * uncompressed using this function will form a single compressed data
125 * stream; however, data will be flushed at the end of every call so that
126 * each output_buffer. This must be called for the same size units that the
127 * buffer_compress was called, and in the same order that buffers compressed
128 * with that. This appends the uncompressed data to the output buffer.
129 */
130
131 void
buffer_uncompress(Buffer * input_buffer,Buffer * output_buffer)132 buffer_uncompress(Buffer * input_buffer, Buffer * output_buffer)
133 {
134 u_char buf[4096];
135 int status;
136
137 incoming_stream.next_in = buffer_ptr(input_buffer);
138 incoming_stream.avail_in = buffer_len(input_buffer);
139
140 for (;;) {
141 /* Set up fixed-size output buffer. */
142 incoming_stream.next_out = buf;
143 incoming_stream.avail_out = sizeof(buf);
144
145 status = inflate(&incoming_stream, Z_PARTIAL_FLUSH);
146 switch (status) {
147 case Z_OK:
148 buffer_append(output_buffer, buf,
149 sizeof(buf) - incoming_stream.avail_out);
150 break;
151 case Z_BUF_ERROR:
152 /*
153 * Comments in zlib.h say that we should keep calling
154 * inflate() until we get an error. This appears to
155 * be the error that we get.
156 */
157 return;
158 default:
159 inflate_failed = 1;
160 fatal("buffer_uncompress: inflate returned %d", status);
161 /* NOTREACHED */
162 }
163 }
164 }
165