compress.c

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