openssh/compress.c

   1 /*
   2  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   3  * Copyright (c) 1995 Tatu Ylonen <ylo@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 1.15 2001/09/27 11:58:16 markus Exp $");
  16
  17 #include "log.h"
  18 #include "buffer.h"
  19 #include "zlib.h"
  20 #include "compress.h"
  21
  22 static z_stream incoming_stream;
  23 static z_stream outgoing_stream;
  24 static int compress_init_send_called = 0;
  25 static int compress_init_recv_called = 0;
  26
  27 /*
  28  * Initializes compression; level is compression level from 1 to 9
  29  * (as in gzip).
  30  */
  31
  32 void
  33 buffer_compress_init_send(int level)
  34 {
  35         if (compress_init_send_called == 1)
  36                 deflateEnd(&outgoing_stream);
  37         compress_init_send_called = 1;
  38         debug("Enabling compression at level %d.", level);
  39         if (level < 1 || level > 9)
  40                 fatal("Bad compression level %d.", level);
  41         deflateInit(&outgoing_stream, level);
  42 }
  43 void
  44 buffer_compress_init_recv(void)
  45 {
  46         if (compress_init_recv_called == 1)
  47                 inflateEnd(&incoming_stream);
  48         compress_init_recv_called = 1;
  49         inflateInit(&incoming_stream);
  50 }
  51
  52 /* Frees any data structures allocated for compression. */
  53
  54 void
  55 buffer_compress_uninit(void)
  56 {
  57         debug("compress outgoing: raw data %lu, compressed %lu, factor %.2f",
  58               outgoing_stream.total_in, outgoing_stream.total_out,
  59               outgoing_stream.total_in == 0 ? 0.0 :
  60               (double) outgoing_stream.total_out / outgoing_stream.total_in);
  61         debug("compress incoming: raw data %lu, compressed %lu, factor %.2f",
  62               incoming_stream.total_out, incoming_stream.total_in,
  63               incoming_stream.total_out == 0 ? 0.0 :
  64               (double) incoming_stream.total_in / incoming_stream.total_out);
  65         if (compress_init_recv_called == 1)
  66                 inflateEnd(&incoming_stream);
  67         if (compress_init_send_called == 1)
  68                 deflateEnd(&outgoing_stream);
  69 }
  70
  71 /*
  72  * Compresses the contents of input_buffer into output_buffer.  All packets
  73  * compressed using this function will form a single compressed data stream;
  74  * however, data will be flushed at the end of every call so that each
  75  * output_buffer can be decompressed independently (but in the appropriate
  76  * order since they together form a single compression stream) by the
  77  * receiver.  This appends the compressed data to the output buffer.
  78  */
  79
  80 void
  81 buffer_compress(Buffer * input_buffer, Buffer * output_buffer)
  82 {
  83         char buf[4096];
  84         int status;
  85
  86         /* This case is not handled below. */
  87         if (buffer_len(input_buffer) == 0)
  88                 return;
  89
  90         /* Input is the contents of the input buffer. */
  91         outgoing_stream.next_in = (u_char *) buffer_ptr(input_buffer);
  92         outgoing_stream.avail_in = buffer_len(input_buffer);
  93
  94         /* Loop compressing until deflate() returns with avail_out != 0. */
  95         do {
  96                 /* Set up fixed-size output buffer. */
  97                 outgoing_stream.next_out = (u_char *)buf;
  98                 outgoing_stream.avail_out = sizeof(buf);
  99
 100                 /* Compress as much data into the buffer as possible. */
 101                 status = deflate(&outgoing_stream, Z_PARTIAL_FLUSH);
 102                 switch (status) {
 103                 case Z_OK:
 104                         /* Append compressed data to output_buffer. */
 105                         buffer_append(output_buffer, buf,
 106                             sizeof(buf) - outgoing_stream.avail_out);
 107                         break;
 108                 default:
 109                         fatal("buffer_compress: deflate returned %d", status);
 110                         /* NOTREACHED */
 111                 }
 112         } while (outgoing_stream.avail_out == 0);
 113 }
 114
 115 /*
 116  * Uncompresses the contents of input_buffer into output_buffer.  All packets
 117  * uncompressed using this function will form a single compressed data
 118  * stream; however, data will be flushed at the end of every call so that
 119  * each output_buffer.  This must be called for the same size units that the
 120  * buffer_compress was called, and in the same order that buffers compressed
 121  * with that.  This appends the uncompressed data to the output buffer.
 122  */
 123
 124 void
 125 buffer_uncompress(Buffer * input_buffer, Buffer * output_buffer)
 126 {
 127         char buf[4096];
 128         int status;
 129
 130         incoming_stream.next_in = (u_char *) buffer_ptr(input_buffer);
 131         incoming_stream.avail_in = buffer_len(input_buffer);
 132
 133         for (;;) {
 134                 /* Set up fixed-size output buffer. */
 135                 incoming_stream.next_out = (u_char *) buf;
 136                 incoming_stream.avail_out = sizeof(buf);
 137
 138                 status = inflate(&incoming_stream, Z_PARTIAL_FLUSH);
 139                 switch (status) {
 140                 case Z_OK:
 141                         buffer_append(output_buffer, buf,
 142                             sizeof(buf) - incoming_stream.avail_out);
 143                         break;
 144                 case Z_BUF_ERROR:
 145                         /*
 146                          * Comments in zlib.h say that we should keep calling
 147                          * inflate() until we get an error.  This appears to
 148                          * be the error that we get.
 149                          */
 150                         return;
 151                 default:
 152                         fatal("buffer_uncompress: inflate returned %d", status);
 153                         /* NOTREACHED */
 154                 }
 155         }
 156 }