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 comparision 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/macros.h>
  27
  28 #include <stdlib.h>
  29 #include <unistd.h>
  30 #include <signal.h>
  31 #include <fcntl.h>
  32 #include <iostream>
  33
  34 #include <apti18n.h>
  35                                                                         /*}}}*/
  36
  37 using namespace std;
  38
  39 // The on disk header for a tar file.
  40 struct ExtractTar::TarHeader
  41 {
  42    char Name[100];
  43    char Mode[8];
  44    char UserID[8];
  45    char GroupID[8];
  46    char Size[12];
  47    char MTime[12];
  48    char Checksum[8];
  49    char LinkFlag;
  50    char LinkName[100];
  51    char MagicNumber[8];
  52    char UserName[32];
  53    char GroupName[32];
  54    char Major[8];
  55    char Minor[8];
  56 };
  57
  58 // ExtractTar::ExtractTar - Constructor                                 /*{{{*/
  59 // ---------------------------------------------------------------------
  60 /* */
  61 ExtractTar::ExtractTar(FileFd &Fd,unsigned long Max,string DecompressionProgram) : File(Fd),
  62                          MaxInSize(Max), DecompressProg(DecompressionProgram)
  63
  64 {
  65    GZPid = -1;
  66    InFd = -1;
  67    Eof = false;
  68 }
  69                                                                         /*}}}*/
  70 // ExtractTar::ExtractTar - Destructor                                  /*{{{*/
  71 // ---------------------------------------------------------------------
  72 /* */
  73 ExtractTar::~ExtractTar()
  74 {
  75    // Error close
  76    Done(true);
  77 }
  78                                                                         /*}}}*/
  79 // ExtractTar::Done - Reap the gzip sub process                         /*{{{*/
  80 // ---------------------------------------------------------------------
  81 /* If the force flag is given then error messages are suppressed - this
  82    means we hit the end of the tar file but there was still gzip data. */
  83 bool ExtractTar::Done(bool Force)
  84 {
  85    InFd.Close();
  86    if (GZPid <= 0)
  87       return true;
  88
  89    /* If there is a pending error then we are cleaning up gzip and are
  90       not interested in it's failures */
  91    if (_error->PendingError() == true)
  92       Force = true;
  93
  94    // Make sure we clean it up!
  95    kill(GZPid,SIGINT);
  96    string confvar = string("dir::bin::") + DecompressProg;
  97    if (ExecWait(GZPid,_config->Find(confvar.c_str(),DecompressProg.c_str()).c_str(),
  98                 Force) == false)
  99    {
 100       GZPid = -1;
 101       return Force;
 102    }
 103
 104    GZPid = -1;
 105    return true;
 106 }
 107                                                                         /*}}}*/
 108 // ExtractTar::StartGzip - Startup gzip                                 /*{{{*/
 109 // ---------------------------------------------------------------------
 110 /* This creates a gzip sub process that has its input as the file itself.
 111    If this tar file is embedded into something like an ar file then
 112    gzip will efficiently ignore the extra bits. */
 113 bool ExtractTar::StartGzip()
 114 {
 115    int Pipes[2];
 116    if (pipe(Pipes) != 0)
 117       return _error->Errno("pipe",_("Failed to create pipes"));
 118
 119    // Fork off the process
 120    GZPid = ExecFork();
 121
 122    // Spawn the subprocess
 123    if (GZPid == 0)
 124    {
 125       // Setup the FDs
 126       dup2(Pipes[1],STDOUT_FILENO);
 127       dup2(File.Fd(),STDIN_FILENO);
 128       int Fd = open("/dev/null",O_RDWR);
 129       if (Fd == -1)
 130          _exit(101);
 131       dup2(Fd,STDERR_FILENO);
 132       close(Fd);
 133       SetCloseExec(STDOUT_FILENO,false);
 134       SetCloseExec(STDIN_FILENO,false);
 135       SetCloseExec(STDERR_FILENO,false);
 136
 137       const char *Args[3];
 138       string confvar = string("dir::bin::") + DecompressProg;
 139       string argv0 = _config->Find(confvar.c_str(),DecompressProg.c_str());
 140       Args[0] = argv0.c_str();
 141       Args[1] = "-d";
 142       Args[2] = 0;
 143       execvp(Args[0],(char **)Args);
 144       cerr << _("Failed to exec gzip ") << Args[0] << endl;
 145       _exit(100);
 146    }
 147
 148    // Fix up our FDs
 149    InFd.Fd(Pipes[0]);
 150    close(Pipes[1]);
 151    return true;
 152 }
 153                                                                         /*}}}*/
 154 // ExtractTar::Go - Perform extraction                                  /*{{{*/
 155 // ---------------------------------------------------------------------
 156 /* This reads each 512 byte block from the archive and extracts the header
 157    information into the Item structure. Then it resolves the UID/GID and
 158    invokes the correct processing function. */
 159 bool ExtractTar::Go(pkgDirStream &Stream)
 160 {
 161    if (StartGzip() == false)
 162       return false;
 163
 164    // Loop over all blocks
 165    string LastLongLink;
 166    string LastLongName;
 167    while (1)
 168    {
 169       bool BadRecord = false;
 170       unsigned char Block[512];
 171       if (InFd.Read(Block,sizeof(Block),true) == false)
 172          return false;
 173
 174       if (InFd.Eof() == true)
 175          break;
 176
 177       // Get the checksum
 178       TarHeader *Tar = (TarHeader *)Block;
 179       unsigned long CheckSum;
 180       if (StrToNum(Tar->Checksum,CheckSum,sizeof(Tar->Checksum),8) == false)
 181          return _error->Error(_("Corrupted archive"));
 182
 183       /* Compute the checksum field. The actual checksum is blanked out
 184          with spaces so it is not included in the computation */
 185       unsigned long NewSum = 0;
 186       memset(Tar->Checksum,' ',sizeof(Tar->Checksum));
 187       for (int I = 0; I != sizeof(Block); I++)
 188          NewSum += Block[I];
 189
 190       /* Check for a block of nulls - in this case we kill gzip, GNU tar
 191          does this.. */
 192       if (NewSum == ' '*sizeof(Tar->Checksum))
 193          return Done(true);
 194
 195       if (NewSum != CheckSum)
 196          return _error->Error(_("Tar checksum failed, archive corrupted"));
 197
 198       // Decode all of the fields
 199       pkgDirStream::Item Itm;
 200       if (StrToNum(Tar->Mode,Itm.Mode,sizeof(Tar->Mode),8) == false ||
 201           (Base256ToNum(Tar->UserID,Itm.UID,8) == false &&
 202              StrToNum(Tar->UserID,Itm.UID,sizeof(Tar->UserID),8) == false) ||
 203           (Base256ToNum(Tar->GroupID,Itm.GID,8) == false &&
 204              StrToNum(Tar->GroupID,Itm.GID,sizeof(Tar->GroupID),8) == false) ||
 205           (Base256ToNum(Tar->Size,Itm.Size,12) == false &&
 206              StrToNum(Tar->Size,Itm.Size,sizeof(Tar->Size),8) == false) ||
 207           (Base256ToNum(Tar->MTime,Itm.MTime,12) == false &&
 208              StrToNum(Tar->MTime,Itm.MTime,sizeof(Tar->MTime),8) == false) ||
 209           StrToNum(Tar->Major,Itm.Major,sizeof(Tar->Major),8) == false ||
 210           StrToNum(Tar->Minor,Itm.Minor,sizeof(Tar->Minor),8) == false)
 211          return _error->Error(_("Corrupted archive"));
 212
 213       // Grab the filename
 214       if (LastLongName.empty() == false)
 215          Itm.Name = (char *)LastLongName.c_str();
 216       else
 217       {
 218          Tar->Name[sizeof(Tar->Name)-1] = 0;
 219          Itm.Name = Tar->Name;
 220       }
 221       if (Itm.Name[0] == '.' && Itm.Name[1] == '/' && Itm.Name[2] != 0)
 222          Itm.Name += 2;
 223
 224       // Grab the link target
 225       Tar->Name[sizeof(Tar->LinkName)-1] = 0;
 226       Itm.LinkTarget = Tar->LinkName;
 227
 228       if (LastLongLink.empty() == false)
 229          Itm.LinkTarget = (char *)LastLongLink.c_str();
 230
 231       // Convert the type over
 232       switch (Tar->LinkFlag)
 233       {
 234          case NormalFile0:
 235          case NormalFile:
 236          Itm.Type = pkgDirStream::Item::File;
 237          break;
 238
 239          case HardLink:
 240          Itm.Type = pkgDirStream::Item::HardLink;
 241          break;
 242
 243          case SymbolicLink:
 244          Itm.Type = pkgDirStream::Item::SymbolicLink;
 245          break;
 246
 247          case CharacterDevice:
 248          Itm.Type = pkgDirStream::Item::CharDevice;
 249          break;
 250
 251          case BlockDevice:
 252          Itm.Type = pkgDirStream::Item::BlockDevice;
 253          break;
 254
 255          case Directory:
 256          Itm.Type = pkgDirStream::Item::Directory;
 257          break;
 258
 259          case FIFO:
 260          Itm.Type = pkgDirStream::Item::FIFO;
 261          break;
 262
 263          case GNU_LongLink:
 264          {
 265             unsigned long Length = Itm.Size;
 266             unsigned char Block[512];
 267             while (Length > 0)
 268             {
 269                if (InFd.Read(Block,sizeof(Block),true) == false)
 270                   return false;
 271                if (Length <= sizeof(Block))
 272                {
 273                   LastLongLink.append(Block,Block+sizeof(Block));
 274                   break;
 275                }
 276                LastLongLink.append(Block,Block+sizeof(Block));
 277                Length -= sizeof(Block);
 278             }
 279             continue;
 280          }
 281
 282          case GNU_LongName:
 283          {
 284             unsigned long Length = Itm.Size;
 285             unsigned char Block[512];
 286             while (Length > 0)
 287             {
 288                if (InFd.Read(Block,sizeof(Block),true) == false)
 289                   return false;
 290                if (Length < sizeof(Block))
 291                {
 292                   LastLongName.append(Block,Block+sizeof(Block));
 293                   break;
 294                }
 295                LastLongName.append(Block,Block+sizeof(Block));
 296                Length -= sizeof(Block);
 297             }
 298             continue;
 299          }
 300
 301          default:
 302          BadRecord = true;
 303          _error->Warning(_("Unknown TAR header type %u, member %s"),(unsigned)Tar->LinkFlag,Tar->Name);
 304          break;
 305       }
 306
 307       int Fd = -1;
 308       if (BadRecord == false)
 309          if (Stream.DoItem(Itm,Fd) == false)
 310             return false;
 311
 312       // Copy the file over the FD
 313       unsigned long Size = Itm.Size;
 314       while (Size != 0)
 315       {
 316          unsigned char Junk[32*1024];
 317          unsigned long Read = min(Size,(unsigned long)sizeof(Junk));
 318          if (InFd.Read(Junk,((Read+511)/512)*512) == false)
 319             return false;
 320
 321          if (BadRecord == false)
 322          {
 323             if (Fd > 0)
 324             {
 325                if (write(Fd,Junk,Read) != (signed)Read)
 326                   return Stream.Fail(Itm,Fd);
 327             }
 328             else
 329             {
 330                /* An Fd of -2 means to send to a special processing
 331                   function */
 332                if (Fd == -2)
 333                   if (Stream.Process(Itm,Junk,Read,Itm.Size - Size) == false)
 334                      return Stream.Fail(Itm,Fd);
 335             }
 336          }
 337
 338          Size -= Read;
 339       }
 340
 341       // And finish up
 342       if (BadRecord == false)
 343          if (Stream.FinishedFile(Itm,Fd) == false)
 344             return false;
 345
 346       LastLongName.erase();
 347       LastLongLink.erase();
 348    }
 349
 350    return Done(false);
 351 }
 352                                                                         /*}}}*/