apt-inst/contrib/extracttar.cc

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 // $Id: extracttar.cc,v 1.8.2.1 2004/01/16 18:58:50 mdz Exp $
   4 /* ######################################################################
   5
   6    Extract a Tar - Tar Extractor
   7
   8    Some performance measurements showed that zlib performed quite poorly
   9    in comparison to a forked gzip process. This tar extractor makes use
  10    of the fact that dup'd file descriptors have the same seek pointer
  11    and that gzip will not read past the end of a compressed stream,
  12    even if there is more data. We use the dup property to track extraction
  13    progress and the gzip feature to just feed gzip a fd in the middle
  14    of an AR file.
  15
  16    ##################################################################### */
  17                                                                         /*}}}*/
  18 // Include Files                                                        /*{{{*/
  19 #include<config.h>
  20
  21 #include <apt-pkg/dirstream.h>
  22 #include <apt-pkg/extracttar.h>
  23 #include <apt-pkg/error.h>
  24 #include <apt-pkg/strutl.h>
  25 #include <apt-pkg/configuration.h>
  26 #include <apt-pkg/fileutl.h>
  27
  28 #include <string.h>
  29 #include <algorithm>
  30 #include <string>
  31 #include <unistd.h>
  32 #include <signal.h>
  33 #include <fcntl.h>
  34 #include <iostream>
  35
  36 #include <apti18n.h>
  37                                                                         /*}}}*/
  38
  39 using namespace std;
  40
  41 // The on disk header for a tar file.
  42 struct ExtractTar::TarHeader
  43 {
  44    char Name[100];
  45    char Mode[8];
  46    char UserID[8];
  47    char GroupID[8];
  48    char Size[12];
  49    char MTime[12];
  50    char Checksum[8];
  51    char LinkFlag;
  52    char LinkName[100];
  53    char MagicNumber[8];
  54    char UserName[32];
  55    char GroupName[32];
  56    char Major[8];
  57    char Minor[8];
  58 };
  59
  60 // ExtractTar::ExtractTar - Constructor                                 /*{{{*/
  61 // ---------------------------------------------------------------------
  62 /* */
  63 ExtractTar::ExtractTar(FileFd &Fd,unsigned long long Max,string DecompressionProgram)
  64         : File(Fd), MaxInSize(Max), DecompressProg(DecompressionProgram)
  65 {
  66    GZPid = -1;
  67    Eof = false;
  68 }
  69                                                                         /*}}}*/
  70 // ExtractTar::ExtractTar - Destructor                                  /*{{{*/
  71 // ---------------------------------------------------------------------
  72 /* */
  73 ExtractTar::~ExtractTar()
  74 {
  75    // Error close
  76    Done();
  77 }
  78                                                                         /*}}}*/
  79 // ExtractTar::Done - Reap the gzip sub process                         /*{{{*/
  80 bool ExtractTar::Done(bool)
  81 {
  82    return Done();
  83 }
  84 bool ExtractTar::Done()
  85 {
  86    return InFd.Close();
  87 }
  88                                                                         /*}}}*/
  89 // ExtractTar::StartGzip - Startup gzip                                 /*{{{*/
  90 // ---------------------------------------------------------------------
  91 /* This creates a gzip sub process that has its input as the file itself.
  92    If this tar file is embedded into something like an ar file then
  93    gzip will efficiently ignore the extra bits. */
  94 bool ExtractTar::StartGzip()
  95 {
  96    if (DecompressProg.empty())
  97    {
  98       InFd.OpenDescriptor(File.Fd(), FileFd::ReadOnly, FileFd::None, false);
  99       return true;
 100    }
 101
 102    std::vector<APT::Configuration::Compressor> const compressors = APT::Configuration::getCompressors();
 103    std::vector<APT::Configuration::Compressor>::const_iterator compressor = compressors.begin();
 104    for (; compressor != compressors.end(); ++compressor) {
 105       if (compressor->Name == DecompressProg) {
 106          return InFd.OpenDescriptor(File.Fd(), FileFd::ReadOnly, *compressor, false);
 107       }
 108    }
 109
 110    return _error->Error(_("Cannot find a configured compressor for '%s'"),
 111                         DecompressProg.c_str());
 112
 113 }
 114                                                                         /*}}}*/
 115 // ExtractTar::Go - Perform extraction                                  /*{{{*/
 116 // ---------------------------------------------------------------------
 117 /* This reads each 512 byte block from the archive and extracts the header
 118    information into the Item structure. Then it resolves the UID/GID and
 119    invokes the correct processing function. */
 120 bool ExtractTar::Go(pkgDirStream &Stream)
 121 {
 122    if (StartGzip() == false)
 123       return false;
 124
 125    // Loop over all blocks
 126    string LastLongLink, ItemLink;
 127    string LastLongName, ItemName;
 128    while (1)
 129    {
 130       bool BadRecord = false;
 131       unsigned char Block[512];
 132       if (InFd.Read(Block,sizeof(Block),true) == false)
 133          return false;
 134
 135       if (InFd.Eof() == true)
 136          break;
 137
 138       // Get the checksum
 139       TarHeader *Tar = (TarHeader *)Block;
 140       unsigned long CheckSum;
 141       if (StrToNum(Tar->Checksum,CheckSum,sizeof(Tar->Checksum),8) == false)
 142          return _error->Error(_("Corrupted archive"));
 143
 144       /* Compute the checksum field. The actual checksum is blanked out
 145          with spaces so it is not included in the computation */
 146       unsigned long NewSum = 0;
 147       memset(Tar->Checksum,' ',sizeof(Tar->Checksum));
 148       for (int I = 0; I != sizeof(Block); I++)
 149          NewSum += Block[I];
 150
 151       /* Check for a block of nulls - in this case we kill gzip, GNU tar
 152          does this.. */
 153       if (NewSum == ' '*sizeof(Tar->Checksum))
 154          return Done();
 155
 156       if (NewSum != CheckSum)
 157          return _error->Error(_("Tar checksum failed, archive corrupted"));
 158
 159       // Decode all of the fields
 160       pkgDirStream::Item Itm;
 161       if (StrToNum(Tar->Mode,Itm.Mode,sizeof(Tar->Mode),8) == false ||
 162           (Base256ToNum(Tar->UserID,Itm.UID,8) == false &&
 163              StrToNum(Tar->UserID,Itm.UID,sizeof(Tar->UserID),8) == false) ||
 164           (Base256ToNum(Tar->GroupID,Itm.GID,8) == false &&
 165              StrToNum(Tar->GroupID,Itm.GID,sizeof(Tar->GroupID),8) == false) ||
 166           (Base256ToNum(Tar->Size,Itm.Size,12) == false &&
 167              StrToNum(Tar->Size,Itm.Size,sizeof(Tar->Size),8) == false) ||
 168           (Base256ToNum(Tar->MTime,Itm.MTime,12) == false &&
 169              StrToNum(Tar->MTime,Itm.MTime,sizeof(Tar->MTime),8) == false) ||
 170           StrToNum(Tar->Major,Itm.Major,sizeof(Tar->Major),8) == false ||
 171           StrToNum(Tar->Minor,Itm.Minor,sizeof(Tar->Minor),8) == false)
 172          return _error->Error(_("Corrupted archive"));
 173
 174       // Grab the filename and link target: use last long name if one was
 175       // set, otherwise use the header value as-is, but remember that it may
 176       // fill the entire 100-byte block and needs to be zero-terminated.
 177       // See Debian Bug #689582.
 178       if (LastLongName.empty() == false)
 179          Itm.Name = (char *)LastLongName.c_str();
 180       else
 181          Itm.Name = (char *)ItemName.assign(Tar->Name, sizeof(Tar->Name)).c_str();
 182       if (Itm.Name[0] == '.' && Itm.Name[1] == '/' && Itm.Name[2] != 0)
 183          Itm.Name += 2;
 184
 185       if (LastLongLink.empty() == false)
 186          Itm.LinkTarget = (char *)LastLongLink.c_str();
 187       else
 188          Itm.LinkTarget = (char *)ItemLink.assign(Tar->LinkName, sizeof(Tar->LinkName)).c_str();
 189
 190       // Convert the type over
 191       switch (Tar->LinkFlag)
 192       {
 193          case NormalFile0:
 194          case NormalFile:
 195          Itm.Type = pkgDirStream::Item::File;
 196          break;
 197
 198          case HardLink:
 199          Itm.Type = pkgDirStream::Item::HardLink;
 200          break;
 201
 202          case SymbolicLink:
 203          Itm.Type = pkgDirStream::Item::SymbolicLink;
 204          break;
 205
 206          case CharacterDevice:
 207          Itm.Type = pkgDirStream::Item::CharDevice;
 208          break;
 209
 210          case BlockDevice:
 211          Itm.Type = pkgDirStream::Item::BlockDevice;
 212          break;
 213
 214          case Directory:
 215          Itm.Type = pkgDirStream::Item::Directory;
 216          break;
 217
 218          case FIFO:
 219          Itm.Type = pkgDirStream::Item::FIFO;
 220          break;
 221
 222          case GNU_LongLink:
 223          {
 224             unsigned long long Length = Itm.Size;
 225             unsigned char Block[512];
 226             while (Length > 0)
 227             {
 228                if (InFd.Read(Block,sizeof(Block),true) == false)
 229                   return false;
 230                if (Length <= sizeof(Block))
 231                {
 232                   LastLongLink.append(Block,Block+sizeof(Block));
 233                   break;
 234                }
 235                LastLongLink.append(Block,Block+sizeof(Block));
 236                Length -= sizeof(Block);
 237             }
 238             continue;
 239          }
 240
 241          case GNU_LongName:
 242          {
 243             unsigned long long Length = Itm.Size;
 244             unsigned char Block[512];
 245             while (Length > 0)
 246             {
 247                if (InFd.Read(Block,sizeof(Block),true) == false)
 248                   return false;
 249                if (Length < sizeof(Block))
 250                {
 251                   LastLongName.append(Block,Block+sizeof(Block));
 252                   break;
 253                }
 254                LastLongName.append(Block,Block+sizeof(Block));
 255                Length -= sizeof(Block);
 256             }
 257             continue;
 258          }
 259
 260          default:
 261          BadRecord = true;
 262          _error->Warning(_("Unknown TAR header type %u, member %s"),(unsigned)Tar->LinkFlag,Tar->Name);
 263          break;
 264       }
 265
 266       int Fd = -1;
 267       if (BadRecord == false)
 268          if (Stream.DoItem(Itm,Fd) == false)
 269             return false;
 270
 271       // Copy the file over the FD
 272       unsigned long long Size = Itm.Size;
 273       while (Size != 0)
 274       {
 275          unsigned char Junk[32*1024];
 276          unsigned long Read = min(Size, (unsigned long long)sizeof(Junk));
 277          if (InFd.Read(Junk,((Read+511)/512)*512) == false)
 278             return false;
 279
 280          if (BadRecord == false)
 281          {
 282             if (Fd > 0)
 283             {
 284                if (write(Fd,Junk,Read) != (signed)Read)
 285                   return Stream.Fail(Itm,Fd);
 286             }
 287             else
 288             {
 289                /* An Fd of -2 means to send to a special processing
 290                   function */
 291                if (Fd == -2)
 292                   if (Stream.Process(Itm,Junk,Read,Itm.Size - Size) == false)
 293                      return Stream.Fail(Itm,Fd);
 294             }
 295          }
 296
 297          Size -= Read;
 298       }
 299
 300       // And finish up
 301       if (BadRecord == false)
 302          if (Stream.FinishedFile(Itm,Fd) == false)
 303             return false;
 304
 305       LastLongName.erase();
 306       LastLongLink.erase();
 307    }
 308
 309    return Done();
 310 }
 311                                                                         /*}}}*/