compress.c

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