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      1 /*
      2  * Author: Tatu Ylonen <ylo (at) cs.hut.fi>
      3  * Copyright (c) 1995 Tatu Ylonen <ylo (at) cs.hut.fi>, Espoo, Finland
      4  *                    All rights reserved
      5  * Interface to packet compression for ssh.
      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 #include "includes.h"
     15 RCSID("$OpenBSD: compress.c,v 1.19 2002/03/18 17:31:54 provos Exp $");
     16 
     17 #pragma ident	"%Z%%M%	%I%	%E% SMI"
     18 
     19 #include "log.h"
     20 #include "buffer.h"
     21 #include "zlib.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
     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
     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
     59 buffer_compress_uninit(void)
     60 {
     61 	debug("compress outgoing: raw data %lu, compressed %lu, factor %.2f",
     62 	    outgoing_stream.total_in, outgoing_stream.total_out,
     63 	    outgoing_stream.total_in == 0 ? 0.0 :
     64 	    (double) outgoing_stream.total_out / outgoing_stream.total_in);
     65 	debug("compress incoming: raw data %lu, compressed %lu, factor %.2f",
     66 	    incoming_stream.total_out, incoming_stream.total_in,
     67 	    incoming_stream.total_out == 0 ? 0.0 :
     68 	    (double) incoming_stream.total_in / incoming_stream.total_out);
     69 	if (compress_init_recv_called == 1 && inflate_failed == 0)
     70 		inflateEnd(&incoming_stream);
     71 	if (compress_init_send_called == 1 && deflate_failed == 0)
     72 		deflateEnd(&outgoing_stream);
     73 }
     74 
     75 /*
     76  * Compresses the contents of input_buffer into output_buffer.  All packets
     77  * compressed using this function will form a single compressed data stream;
     78  * however, data will be flushed at the end of every call so that each
     79  * output_buffer can be decompressed independently (but in the appropriate
     80  * order since they together form a single compression stream) by the
     81  * receiver.  This appends the compressed data to the output buffer.
     82  */
     83 
     84 void
     85 buffer_compress(Buffer * input_buffer, Buffer * output_buffer)
     86 {
     87 	u_char buf[4096];
     88 	int status;
     89 
     90 	/* This case is not handled below. */
     91 	if (buffer_len(input_buffer) == 0)
     92 		return;
     93 
     94 	/* Input is the contents of the input buffer. */
     95 	outgoing_stream.next_in = buffer_ptr(input_buffer);
     96 	outgoing_stream.avail_in = buffer_len(input_buffer);
     97 
     98 	/* Loop compressing until deflate() returns with avail_out != 0. */
     99 	do {
    100 		/* Set up fixed-size output buffer. */
    101 		outgoing_stream.next_out = buf;
    102 		outgoing_stream.avail_out = sizeof(buf);
    103 
    104 		/* Compress as much data into the buffer as possible. */
    105 		status = deflate(&outgoing_stream, Z_PARTIAL_FLUSH);
    106 		switch (status) {
    107 		case Z_OK:
    108 			/* Append compressed data to output_buffer. */
    109 			buffer_append(output_buffer, buf,
    110 			    sizeof(buf) - outgoing_stream.avail_out);
    111 			break;
    112 		default:
    113 			deflate_failed = 1;
    114 			fatal("buffer_compress: deflate returned %d", status);
    115 			/* NOTREACHED */
    116 		}
    117 	} while (outgoing_stream.avail_out == 0);
    118 }
    119 
    120 /*
    121  * Uncompresses the contents of input_buffer into output_buffer.  All packets
    122  * uncompressed using this function will form a single compressed data
    123  * stream; however, data will be flushed at the end of every call so that
    124  * each output_buffer.  This must be called for the same size units that the
    125  * buffer_compress was called, and in the same order that buffers compressed
    126  * with that.  This appends the uncompressed data to the output buffer.
    127  */
    128 
    129 void
    130 buffer_uncompress(Buffer * input_buffer, Buffer * output_buffer)
    131 {
    132 	u_char buf[4096];
    133 	int status;
    134 
    135 	incoming_stream.next_in = buffer_ptr(input_buffer);
    136 	incoming_stream.avail_in = buffer_len(input_buffer);
    137 
    138 	for (;;) {
    139 		/* Set up fixed-size output buffer. */
    140 		incoming_stream.next_out = buf;
    141 		incoming_stream.avail_out = sizeof(buf);
    142 
    143 		status = inflate(&incoming_stream, Z_PARTIAL_FLUSH);
    144 		switch (status) {
    145 		case Z_OK:
    146 			buffer_append(output_buffer, buf,
    147 			    sizeof(buf) - incoming_stream.avail_out);
    148 			break;
    149 		case Z_BUF_ERROR:
    150 			/*
    151 			 * Comments in zlib.h say that we should keep calling
    152 			 * inflate() until we get an error.  This appears to
    153 			 * be the error that we get.
    154 			 */
    155 			return;
    156 		default:
    157 			inflate_failed = 1;
    158 			fatal("buffer_uncompress: inflate returned %d", status);
    159 			/* NOTREACHED */
    160 		}
    161 	}
    162 }
    163