apt-inst/extract.cc

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 // $Id: extract.cc,v 1.2 2001/02/20 07:03:16 jgg Exp $
   4 /* ######################################################################
   5
   6    Archive Extraction Directory Stream
   7
   8    Extraction for each file is a bit of an involved process. Each object
   9    undergoes an atomic backup, overwrite, erase sequence. First the
  10    object is unpacked to '.dpkg.new' then the original is hardlinked to
  11    '.dpkg.tmp' and finally the new object is renamed to overwrite the old
  12    one. From an external perspective the file never ceased to exist.
  13    After the archive has been sucessfully unpacked the .dpkg.tmp files
  14    are erased. A failure causes all the .dpkg.tmp files to be restored.
  15
  16    Decisions about unpacking go like this:
  17       - Store the original filename in the file listing
  18       - Resolve any diversions that would effect this file, all checks
  19         below apply to the diverted name, not the real one.
  20       - Resolve any symlinked configuration files.
  21       - If the existing file does not exist then .dpkg-tmp is checked for.
  22         [Note, this is reduced to only check if a file was expected to be
  23          there]
  24       - If the existing link/file is not a directory then it is replaced
  25         irregardless
  26       - If the existing link/directory is being replaced by a directory then
  27         absolutely nothing happens.
  28       - If the existing link/directory is being replaced by a link then
  29         absolutely nothing happens.
  30       - If the existing link/directory is being replaced by a non-directory
  31         then this will abort if the package is not the sole owner of the
  32         directory. [Note, this is changed to not happen if the directory
  33         non-empty - that is, it only includes files that are part of this
  34         package - prevents removing user files accidentally.]
  35       - If the non-directory exists in the listing database and it
  36         does not belong to the current package then an overwrite condition
  37         is invoked.
  38
  39    As we unpack we record the file list differences in the FL cache. If
  40    we need to unroll the the FL cache knows which files have been unpacked
  41    and can undo. When we need to erase then it knows which files have not
  42    been unpacked.
  43
  44    ##################################################################### */
  45                                                                         /*}}}*/
  46 // Include Files                                                        /*{{{*/
  47 #ifdef __GNUG__
  48 #pragma implementation "apt-pkg/extract.h"
  49 #endif
  50 #include <apt-pkg/extract.h>
  51 #include <apt-pkg/error.h>
  52 #include <apt-pkg/debversion.h>
  53
  54 #include <sys/stat.h>
  55 #include <stdio.h>
  56 #include <unistd.h>
  57 #include <errno.h>
  58 #include <dirent.h>
  59                                                                         /*}}}*/
  60
  61 static const char *TempExt = "dpkg-tmp";
  62 //static const char *NewExt = "dpkg-new";
  63
  64 // Extract::pkgExtract - Constructor                                    /*{{{*/
  65 // ---------------------------------------------------------------------
  66 /* */
  67 pkgExtract::pkgExtract(pkgFLCache &FLCache,pkgCache::VerIterator Ver) :
  68                        FLCache(FLCache), Ver(Ver)
  69 {
  70    FLPkg = FLCache.GetPkg(Ver.ParentPkg().Name(),true);
  71    if (FLPkg.end() == true)
  72       return;
  73    Debug = true;
  74 }
  75                                                                         /*}}}*/
  76 // Extract::DoItem - Handle a single item from the stream               /*{{{*/
  77 // ---------------------------------------------------------------------
  78 /* This performs the setup for the extraction.. */
  79 bool pkgExtract::DoItem(Item &Itm,int &Fd)
  80 {
  81    char Temp[sizeof(FileName)];
  82
  83    /* Strip any leading/trailing /s from the filename, then copy it to the
  84       temp buffer and re-apply the leading / We use a class variable
  85       to store the new filename for use by the three extraction funcs */
  86    char *End = FileName+1;
  87    const char *I = Itm.Name;
  88    for (; *I != 0 && *I == '/'; I++);
  89    *FileName = '/';
  90    for (; *I != 0 && End < FileName + sizeof(FileName); I++, End++)
  91       *End = *I;
  92    if (End + 20 >= FileName + sizeof(FileName))
  93       return _error->Error("The path %s is too long",Itm.Name);
  94    for (; End > FileName && End[-1] == '/'; End--);
  95    *End = 0;
  96    Itm.Name = FileName;
  97
  98    /* Lookup the file. Nde is the file [group] we are going to write to and
  99       RealNde is the actual node we are manipulating. Due to diversions
 100       they may be entirely different. */
 101    pkgFLCache::NodeIterator Nde = FLCache.GetNode(Itm.Name,End,0,false,false);
 102    pkgFLCache::NodeIterator RealNde = Nde;
 103
 104    // See if the file is already in the file listing
 105    unsigned long FileGroup = RealNde->File;
 106    for (; RealNde.end() == false && FileGroup == RealNde->File; RealNde++)
 107       if (RealNde.RealPackage() == FLPkg)
 108          break;
 109
 110    // Nope, create an entry
 111    if (RealNde.end() == true)
 112    {
 113       RealNde = FLCache.GetNode(Itm.Name,End,FLPkg.Offset(),true,false);
 114       if (RealNde.end() == true)
 115          return false;
 116       RealNde->Flags |= pkgFLCache::Node::NewFile;
 117    }
 118
 119    /* Check if this entry already was unpacked. The only time this should
 120       ever happen is if someone has hacked tar to support capabilities, in
 121       which case this needs to be modified anyhow.. */
 122    if ((RealNde->Flags & pkgFLCache::Node::Unpacked) ==
 123        pkgFLCache::Node::Unpacked)
 124       return _error->Error("Unpacking %s more than once",Itm.Name);
 125
 126    if (Nde.end() == true)
 127       Nde = RealNde;
 128
 129    /* Consider a diverted file - We are not permitted to divert directories,
 130       but everything else is fair game (including conf files!) */
 131    if ((Nde->Flags & pkgFLCache::Node::Diversion) != 0)
 132    {
 133       if (Itm.Type == Item::Directory)
 134          return _error->Error("The directory %s is diverted",Itm.Name);
 135
 136       /* A package overwriting a diversion target is just the same as
 137          overwriting a normally owned file and is checked for below in
 138          the overwrites mechanism */
 139
 140       /* If this package is trying to overwrite the target of a diversion,
 141          that is never, ever permitted */
 142       pkgFLCache::DiverIterator Div = Nde.Diversion();
 143       if (Div.DivertTo() == Nde)
 144          return _error->Error("The package is trying to write to the "
 145                               "diversion target %s/%s",Nde.DirN(),Nde.File());
 146
 147       // See if it is us and we are following it in the right direction
 148       if (Div->OwnerPkg != FLPkg.Offset() && Div.DivertFrom() == Nde)
 149       {
 150          Nde = Div.DivertTo();
 151          End = FileName + snprintf(FileName,sizeof(FileName)-20,"%s/%s",
 152                                    Nde.DirN(),Nde.File());
 153          if (End <= FileName)
 154             return _error->Error("The diversion path is too long");
 155       }
 156    }
 157
 158    // Deal with symlinks and conf files
 159    if ((RealNde->Flags & pkgFLCache::Node::NewConfFile) ==
 160        pkgFLCache::Node::NewConfFile)
 161    {
 162       string Res = flNoLink(Itm.Name);
 163       if (Res.length() > sizeof(FileName))
 164          return _error->Error("The path %s is too long",Res.c_str());
 165       if (Debug == true)
 166          clog << "Followed conf file from " << FileName << " to " << Res << endl;
 167       Itm.Name = strcpy(FileName,Res.c_str());
 168    }
 169
 170    /* Get information about the existing file, and attempt to restore
 171       a backup if it does not exist */
 172    struct stat LExisting;
 173    bool EValid = false;
 174    if (lstat(Itm.Name,&LExisting) != 0)
 175    {
 176       // This is bad news.
 177       if (errno != ENOENT)
 178          return _error->Errno("stat","Failed to stat %s",Itm.Name);
 179
 180       // See if we can recover the backup file
 181       if (Nde.end() == false)
 182       {
 183          snprintf(Temp,sizeof(Temp),"%s.%s",Itm.Name,TempExt);
 184          if (rename(Temp,Itm.Name) != 0 && errno != ENOENT)
 185             return _error->Errno("rename","Failed to rename %s to %s",
 186                                  Temp,Itm.Name);
 187          if (stat(Itm.Name,&LExisting) != 0)
 188          {
 189             if (errno != ENOENT)
 190                return _error->Errno("stat","Failed to stat %s",Itm.Name);
 191          }
 192          else
 193             EValid = true;
 194       }
 195    }
 196    else
 197       EValid = true;
 198
 199    /* If the file is a link we need to stat its destination, get the
 200       existing file modes */
 201    struct stat Existing = LExisting;
 202    if (EValid == true && S_ISLNK(Existing.st_mode))
 203    {
 204       if (stat(Itm.Name,&Existing) != 0)
 205       {
 206          if (errno != ENOENT)
 207             return _error->Errno("stat","Failed to stat %s",Itm.Name);
 208          Existing = LExisting;
 209       }
 210    }
 211
 212    // We pretend a non-existing file looks like it is a normal file
 213    if (EValid == false)
 214       Existing.st_mode = S_IFREG;
 215
 216    /* Okay, at this point 'Existing' is the stat information for the
 217       real non-link file */
 218
 219    /* The only way this can be a no-op is if a directory is being
 220       replaced by a directory or by a link */
 221    if (S_ISDIR(Existing.st_mode) != 0 &&
 222        (Itm.Type == Item::Directory || Itm.Type == Item::SymbolicLink))
 223       return true;
 224
 225    /* Non-Directory being replaced by non-directory. We check for over
 226       writes here. */
 227    if (Nde.end() == false)
 228    {
 229       if (HandleOverwrites(Nde) == false)
 230          return false;
 231    }
 232
 233    /* Directory being replaced by a non-directory - this needs to see if
 234       the package is the owner and then see if the directory would be
 235       empty after the package is removed [ie no user files will be
 236       erased] */
 237    if (S_ISDIR(Existing.st_mode) != 0)
 238    {
 239       if (CheckDirReplace(Itm.Name) == false)
 240          return _error->Error("The directory %s is being replaced by a non-directory",Itm.Name);
 241    }
 242
 243    if (Debug == true)
 244       clog << "Extract " << string(Itm.Name,End) << endl;
 245 /*   if (Count != 0)
 246       return _error->Error("Done");*/
 247
 248    return true;
 249 }
 250                                                                         /*}}}*/
 251 // Extract::Finished - Sequence finished, erase the temp files          /*{{{*/
 252 // ---------------------------------------------------------------------
 253 /* */
 254 bool pkgExtract::Finished()
 255 {
 256    return true;
 257 }
 258                                                                         /*}}}*/
 259 // Extract::Aborted - Sequence aborted, undo all our unpacking          /*{{{*/
 260 // ---------------------------------------------------------------------
 261 /* This undoes everything that was done by all calls to the DoItem method
 262    and restores the File Listing cache to its original form. It bases its
 263    actions on the flags value for each node in the cache. */
 264 bool pkgExtract::Aborted()
 265 {
 266    if (Debug == true)
 267       clog << "Aborted, backing out" << endl;
 268
 269    pkgFLCache::NodeIterator Files = FLPkg.Files();
 270    map_ptrloc *Last = &FLPkg->Files;
 271
 272    /* Loop over all files, restore those that have been unpacked from their
 273       dpkg-tmp entires */
 274    while (Files.end() == false)
 275    {
 276       // Locate the hash bucket for the node and locate its group head
 277       pkgFLCache::NodeIterator Nde(FLCache,FLCache.HashNode(Files));
 278       for (; Nde.end() == false && Files->File != Nde->File; Nde++);
 279       if (Nde.end() == true)
 280          return _error->Error("Failed to locate node in its hash bucket");
 281
 282       if (snprintf(FileName,sizeof(FileName)-20,"%s/%s",
 283                    Nde.DirN(),Nde.File()) <= 0)
 284          return _error->Error("The path is too long");
 285
 286       // Deal with diversions
 287       if ((Nde->Flags & pkgFLCache::Node::Diversion) != 0)
 288       {
 289          pkgFLCache::DiverIterator Div = Nde.Diversion();
 290
 291          // See if it is us and we are following it in the right direction
 292          if (Div->OwnerPkg != FLPkg.Offset() && Div.DivertFrom() == Nde)
 293          {
 294             Nde = Div.DivertTo();
 295             if (snprintf(FileName,sizeof(FileName)-20,"%s/%s",
 296                          Nde.DirN(),Nde.File()) <= 0)
 297                return _error->Error("The diversion path is too long");
 298          }
 299       }
 300
 301       // Deal with overwrites+replaces
 302       for (; Nde.end() == false && Files->File == Nde->File; Nde++)
 303       {
 304          if ((Nde->Flags & pkgFLCache::Node::Replaced) ==
 305              pkgFLCache::Node::Replaced)
 306          {
 307             if (Debug == true)
 308                clog << "De-replaced " << FileName << " from " << Nde.RealPackage()->Name << endl;
 309             Nde->Flags &= ~pkgFLCache::Node::Replaced;
 310          }
 311       }
 312
 313       // Undo the change in the filesystem
 314       if (Debug == true)
 315          clog << "Backing out " << FileName;
 316
 317       // Remove a new node
 318       if ((Files->Flags & pkgFLCache::Node::NewFile) ==
 319          pkgFLCache::Node::NewFile)
 320       {
 321          if (Debug == true)
 322             clog << " [new node]" << endl;
 323          pkgFLCache::Node *Tmp = Files;
 324          Files++;
 325          *Last = Tmp->NextPkg;
 326          Tmp->NextPkg = 0;
 327
 328          FLCache.DropNode(Tmp - FLCache.NodeP);
 329       }
 330       else
 331       {
 332          if (Debug == true)
 333             clog << endl;
 334
 335          Last = &Files->NextPkg;
 336          Files++;
 337       }
 338    }
 339
 340    return true;
 341 }
 342                                                                         /*}}}*/
 343 // Extract::Fail - Extraction of a file Failed                          /*{{{*/
 344 // ---------------------------------------------------------------------
 345 /* */
 346 bool pkgExtract::Fail(Item &Itm,int Fd)
 347 {
 348    return pkgDirStream::Fail(Itm,Fd);
 349 }
 350                                                                         /*}}}*/
 351 // Extract::FinishedFile - Finished a file                              /*{{{*/
 352 // ---------------------------------------------------------------------
 353 /* */
 354 bool pkgExtract::FinishedFile(Item &Itm,int Fd)
 355 {
 356    return pkgDirStream::FinishedFile(Itm,Fd);
 357 }
 358                                                                         /*}}}*/
 359 // Extract::HandleOverwrites - See if a replaces covers this overwrite  /*{{{*/
 360 // ---------------------------------------------------------------------
 361 /* Check if the file is in a package that is being replaced by this
 362    package or if the file is being overwritten. Note that if the file
 363    is really a directory but it has been erased from the filesystem
 364    this will fail with an overwrite message. This is a limitation of the
 365    dpkg file information format.
 366
 367    XX If a new package installs and another package replaces files in this
 368    package what should we do? */
 369 bool pkgExtract::HandleOverwrites(pkgFLCache::NodeIterator Nde,
 370                                   bool DiverCheck)
 371 {
 372    pkgFLCache::NodeIterator TmpNde = Nde;
 373    unsigned long DiverOwner = 0;
 374    unsigned long FileGroup = Nde->File;
 375    const char *FirstOwner = 0;
 376    for (; Nde.end() == false && FileGroup == Nde->File; Nde++)
 377    {
 378       if ((Nde->Flags & pkgFLCache::Node::Diversion) != 0)
 379       {
 380          /* Store the diversion owner if this is the forward direction
 381             of the diversion */
 382          if (DiverCheck == true)
 383             DiverOwner = Nde.Diversion()->OwnerPkg;
 384          continue;
 385       }
 386
 387       pkgFLCache::PkgIterator FPkg(FLCache,Nde.RealPackage());
 388       if (FPkg.end() == true || FPkg == FLPkg)
 389          continue;
 390
 391       /* This tests trips when we are checking a diversion to see
 392          if something has already been diverted by this diversion */
 393       if (FPkg.Offset() == DiverOwner)
 394          continue;
 395       FirstOwner = FPkg.Name();
 396
 397       // Now see if this package matches one in a replace depends
 398       pkgCache::DepIterator Dep = Ver.DependsList();
 399       bool Ok = false;
 400       for (; Dep.end() == false; Dep++)
 401       {
 402          if (Dep->Type != pkgCache::Dep::Replaces)
 403             continue;
 404
 405          // Does the replaces apply to this package?
 406          if (strcmp(Dep.TargetPkg().Name(),FPkg.Name()) != 0)
 407              continue;
 408
 409          /* Check the version for match. I do not think CurrentVer can be
 410             0 if we are here.. */
 411          pkgCache::PkgIterator Pkg = Dep.TargetPkg();
 412          if (Pkg->CurrentVer == 0)
 413          {
 414             _error->Warning("Overwrite package match with no version for %s",Pkg.Name());
 415             continue;
 416          }
 417
 418          // Replaces is met
 419          if (debVS.CheckDep(Pkg.CurrentVer().VerStr(),Dep->CompareOp,Dep.TargetVer()) == true)
 420          {
 421             if (Debug == true)
 422                clog << "Replaced file " << Nde.DirN() << '/' << Nde.File() << " from " << Pkg.Name() << endl;
 423             Nde->Flags |= pkgFLCache::Node::Replaced;
 424             Ok = true;
 425             break;
 426          }
 427       }
 428
 429       // Negative Hit
 430       if (Ok == false)
 431          return _error->Error("File %s/%s overwrites the one in the package %s",
 432                               Nde.DirN(),Nde.File(),FPkg.Name());
 433    }
 434
 435    /* If this is a diversion we might have to recurse to process
 436       the other side of it */
 437    if ((TmpNde->Flags & pkgFLCache::Node::Diversion) != 0)
 438    {
 439       pkgFLCache::DiverIterator Div = TmpNde.Diversion();
 440       if (Div.DivertTo() == TmpNde)
 441          return HandleOverwrites(Div.DivertFrom(),true);
 442    }
 443
 444    return true;
 445 }
 446                                                                         /*}}}*/
 447 // Extract::CheckDirReplace - See if this directory can be erased       /*{{{*/
 448 // ---------------------------------------------------------------------
 449 /* If this directory is owned by a single package and that package is
 450    replacing it with something non-directoryish then dpkg allows this.
 451    We increase the requirement to be that the directory is non-empty after
 452    the package is removed */
 453 bool pkgExtract::CheckDirReplace(string Dir,unsigned int Depth)
 454 {
 455    // Looping?
 456    if (Depth > 40)
 457       return false;
 458
 459    if (Dir[Dir.size() - 1] != '/')
 460       Dir += '/';
 461
 462    DIR *D = opendir(Dir.c_str());
 463    if (D == 0)
 464       return _error->Errno("opendir","Unable to read %s",Dir.c_str());
 465
 466    string File;
 467    for (struct dirent *Dent = readdir(D); Dent != 0; Dent = readdir(D))
 468    {
 469       // Skip some files
 470       if (strcmp(Dent->d_name,".") == 0 ||
 471           strcmp(Dent->d_name,"..") == 0)
 472          continue;
 473
 474       // Look up the node
 475       File = Dir + Dent->d_name;
 476       pkgFLCache::NodeIterator Nde = FLCache.GetNode(File.begin(),
 477                                                      File.end(),0,false,false);
 478
 479       // The file is not owned by this package
 480       if (Nde.end() != false || Nde.RealPackage() != FLPkg)
 481       {
 482          closedir(D);
 483          return false;
 484       }
 485
 486       // See if it is a directory
 487       struct stat St;
 488       if (lstat(File.c_str(),&St) != 0)
 489       {
 490          closedir(D);
 491          return _error->Errno("lstat","Unable to stat %s",File.c_str());
 492       }
 493
 494       // Recurse down directories
 495       if (S_ISDIR(St.st_mode) != 0)
 496       {
 497          if (CheckDirReplace(File,Depth + 1) == false)
 498          {
 499             closedir(D);
 500             return false;
 501          }
 502       }
 503    }
 504
 505    // No conflicts
 506    closedir(D);
 507    return true;
 508 }
 509                                                                         /*}}}*/