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
27z_stream incoming_stream;
28z_stream outgoing_stream;
29static int compress_init_send_called = 0;
30static int compress_init_recv_called = 0;
31static int inflate_failed = 0;
32static int deflate_failed = 0;
33
34/*
35 * Initializes compression; level is compression level from 1 to 9
36 * (as in gzip).
37 */
38
39void
40buffer_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}
50void
51buffer_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
61void
62buffer_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
89void
90buffer_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
134void
135buffer_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