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+// -*- mode: cpp; mode: fold -*-
+// Description /*{{{*/
+/* ######################################################################
+
+ Extract a Tar - Tar Extractor
+
+ Some performance measurements showed that zlib performed quite poorly
+ in comparison to a forked gzip process. This tar extractor makes use
+ of the fact that dup'd file descriptors have the same seek pointer
+ and that gzip will not read past the end of a compressed stream,
+ even if there is more data. We use the dup property to track extraction
+ progress and the gzip feature to just feed gzip a fd in the middle
+ of an AR file.
+
+ ##################################################################### */
+ /*}}}*/
+// Include Files /*{{{*/
+#include <config.h>
+
+#include <apt-pkg/configuration.h>
+#include <apt-pkg/dirstream.h>
+#include <apt-pkg/error.h>
+#include <apt-pkg/extracttar.h>
+#include <apt-pkg/fileutl.h>
+#include <apt-pkg/strutl.h>
+
+#include <algorithm>
+#include <iostream>
+#include <string>
+#include <fcntl.h>
+#include <signal.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <apti18n.h>
+ /*}}}*/
+
+using namespace std;
+
+// The on disk header for a tar file.
+struct ExtractTar::TarHeader
+{
+ char Name[100];
+ char Mode[8];
+ char UserID[8];
+ char GroupID[8];
+ char Size[12];
+ char MTime[12];
+ char Checksum[8];
+ char LinkFlag;
+ char LinkName[100];
+ char MagicNumber[8];
+ char UserName[32];
+ char GroupName[32];
+ char Major[8];
+ char Minor[8];
+};
+
+// We need to read long names (names and link targets) into memory, so let's
+// have a limit (shamelessly stolen from libarchive) to avoid people OOMing
+// us with large streams.
+static const unsigned long long APT_LONGNAME_LIMIT = 1048576llu;
+
+// A file size limit that we allow extracting. Currently, that's 128 GB.
+// We also should leave some wiggle room for code adding files to it, and
+// possibly conversion for signed, so this should not be larger than like 2**62.
+static const unsigned long long APT_FILESIZE_LIMIT = 1llu << 37;
+
+// ExtractTar::ExtractTar - Constructor /*{{{*/
+// ---------------------------------------------------------------------
+/* */
+ExtractTar::ExtractTar(FileFd &Fd,unsigned long long Max,string DecompressionProgram)
+ : File(Fd), MaxInSize(Max), DecompressProg(DecompressionProgram)
+{
+ GZPid = -1;
+ Eof = false;
+}
+ /*}}}*/
+// ExtractTar::ExtractTar - Destructor /*{{{*/
+// ---------------------------------------------------------------------
+/* */
+ExtractTar::~ExtractTar()
+{
+ // Error close
+ Done();
+}
+ /*}}}*/
+// ExtractTar::Done - Reap the gzip sub process /*{{{*/
+bool ExtractTar::Done()
+{
+ return InFd.Close();
+}
+ /*}}}*/
+// ExtractTar::StartGzip - Startup gzip /*{{{*/
+// ---------------------------------------------------------------------
+/* This creates a gzip sub process that has its input as the file itself.
+ If this tar file is embedded into something like an ar file then
+ gzip will efficiently ignore the extra bits. */
+bool ExtractTar::StartGzip()
+{
+ if (DecompressProg.empty())
+ {
+ InFd.OpenDescriptor(File.Fd(), FileFd::ReadOnly, FileFd::None, false);
+ return true;
+ }
+
+ std::vector<APT::Configuration::Compressor> const compressors = APT::Configuration::getCompressors();
+ std::vector<APT::Configuration::Compressor>::const_iterator compressor = compressors.begin();
+ for (; compressor != compressors.end(); ++compressor) {
+ if (compressor->Name == DecompressProg) {
+ return InFd.OpenDescriptor(File.Fd(), FileFd::ReadOnly, *compressor, false);
+ }
+ }
+
+ return _error->Error(_("Cannot find a configured compressor for '%s'"),
+ DecompressProg.c_str());
+
+}
+ /*}}}*/
+// ExtractTar::Go - Perform extraction /*{{{*/
+// ---------------------------------------------------------------------
+/* This reads each 512 byte block from the archive and extracts the header
+ information into the Item structure. Then it resolves the UID/GID and
+ invokes the correct processing function. */
+bool ExtractTar::Go(pkgDirStream &Stream)
+{
+ if (StartGzip() == false)
+ return false;
+
+ // Loop over all blocks
+ string LastLongLink, ItemLink;
+ string LastLongName, ItemName;
+ while (1)
+ {
+ bool BadRecord = false;
+ unsigned char Block[512];
+ if (InFd.Read(Block,sizeof(Block),true) == false)
+ return false;
+
+ if (InFd.Eof() == true)
+ break;
+
+ // Get the checksum
+ TarHeader *Tar = (TarHeader *)Block;
+ unsigned long CheckSum;
+ if (StrToNum(Tar->Checksum,CheckSum,sizeof(Tar->Checksum),8) == false)
+ return _error->Error(_("Corrupted archive"));
+
+ /* Compute the checksum field. The actual checksum is blanked out
+ with spaces so it is not included in the computation */
+ unsigned long NewSum = 0;
+ memset(Tar->Checksum,' ',sizeof(Tar->Checksum));
+ for (int I = 0; I != sizeof(Block); I++)
+ NewSum += Block[I];
+
+ /* Check for a block of nulls - in this case we kill gzip, GNU tar
+ does this.. */
+ if (NewSum == ' '*sizeof(Tar->Checksum))
+ return Done();
+
+ if (NewSum != CheckSum)
+ return _error->Error(_("Tar checksum failed, archive corrupted"));
+
+ // Decode all of the fields
+ pkgDirStream::Item Itm;
+ if (StrToNum(Tar->Mode,Itm.Mode,sizeof(Tar->Mode),8) == false ||
+ (Base256ToNum(Tar->UserID,Itm.UID,8) == false &&
+ StrToNum(Tar->UserID,Itm.UID,sizeof(Tar->UserID),8) == false) ||
+ (Base256ToNum(Tar->GroupID,Itm.GID,8) == false &&
+ StrToNum(Tar->GroupID,Itm.GID,sizeof(Tar->GroupID),8) == false) ||
+ (Base256ToNum(Tar->Size,Itm.Size,12) == false &&
+ StrToNum(Tar->Size,Itm.Size,sizeof(Tar->Size),8) == false) ||
+ (Base256ToNum(Tar->MTime,Itm.MTime,12) == false &&
+ StrToNum(Tar->MTime,Itm.MTime,sizeof(Tar->MTime),8) == false) ||
+ StrToNum(Tar->Major,Itm.Major,sizeof(Tar->Major),8) == false ||
+ StrToNum(Tar->Minor,Itm.Minor,sizeof(Tar->Minor),8) == false)
+ return _error->Error(_("Corrupted archive"));
+
+ // Security check. Prevents overflows below the code when rounding up in skip/copy code,
+ // and provides modest protection against decompression bombs.
+ if (Itm.Size > APT_FILESIZE_LIMIT)
+ return _error->Error("Tar member too large: %llu > %llu bytes", Itm.Size, APT_FILESIZE_LIMIT);
+
+ // Grab the filename and link target: use last long name if one was
+ // set, otherwise use the header value as-is, but remember that it may
+ // fill the entire 100-byte block and needs to be zero-terminated.
+ // See Debian Bug #689582.
+ if (LastLongName.empty() == false)
+ Itm.Name = (char *)LastLongName.c_str();
+ else
+ Itm.Name = (char *)ItemName.assign(Tar->Name, sizeof(Tar->Name)).c_str();
+ if (Itm.Name[0] == '.' && Itm.Name[1] == '/' && Itm.Name[2] != 0)
+ Itm.Name += 2;
+
+ if (LastLongLink.empty() == false)
+ Itm.LinkTarget = (char *)LastLongLink.c_str();
+ else
+ Itm.LinkTarget = (char *)ItemLink.assign(Tar->LinkName, sizeof(Tar->LinkName)).c_str();
+
+ // Convert the type over
+ switch (Tar->LinkFlag)
+ {
+ case NormalFile0:
+ case NormalFile:
+ Itm.Type = pkgDirStream::Item::File;
+ break;
+
+ case HardLink:
+ Itm.Type = pkgDirStream::Item::HardLink;
+ break;
+
+ case SymbolicLink:
+ Itm.Type = pkgDirStream::Item::SymbolicLink;
+ break;
+
+ case CharacterDevice:
+ Itm.Type = pkgDirStream::Item::CharDevice;
+ break;
+
+ case BlockDevice:
+ Itm.Type = pkgDirStream::Item::BlockDevice;
+ break;
+
+ case Directory:
+ Itm.Type = pkgDirStream::Item::Directory;
+ break;
+
+ case FIFO:
+ Itm.Type = pkgDirStream::Item::FIFO;
+ break;
+
+ case GNU_LongLink:
+ {
+ unsigned long long Length = Itm.Size;
+ unsigned char Block[512];
+ if (Length > APT_LONGNAME_LIMIT)
+ return _error->Error("Long name to large: %llu bytes > %llu bytes", Length, APT_LONGNAME_LIMIT);
+ while (Length > 0)
+ {
+ if (InFd.Read(Block,sizeof(Block),true) == false)
+ return false;
+ if (Length <= sizeof(Block))
+ {
+ LastLongLink.append(Block,Block+sizeof(Block));
+ break;
+ }
+ LastLongLink.append(Block,Block+sizeof(Block));
+ Length -= sizeof(Block);
+ }
+ continue;
+ }
+
+ case GNU_LongName:
+ {
+ unsigned long long Length = Itm.Size;
+ unsigned char Block[512];
+ if (Length > APT_LONGNAME_LIMIT)
+ return _error->Error("Long name to large: %llu bytes > %llu bytes", Length, APT_LONGNAME_LIMIT);
+ while (Length > 0)
+ {
+ if (InFd.Read(Block,sizeof(Block),true) == false)
+ return false;
+ if (Length < sizeof(Block))
+ {
+ LastLongName.append(Block,Block+sizeof(Block));
+ break;
+ }
+ LastLongName.append(Block,Block+sizeof(Block));
+ Length -= sizeof(Block);
+ }
+ continue;
+ }
+
+ default:
+ BadRecord = true;
+ _error->Warning(_("Unknown TAR header type %u"), (unsigned)Tar->LinkFlag);
+ break;
+ }
+
+ int Fd = -1;
+ if (not BadRecord && not Stream.DoItem(Itm, Fd))
+ return false;
+
+ if (Fd == -1 || Fd < -2 || BadRecord)
+ {
+ if (Itm.Size > 0 && not InFd.Skip(((Itm.Size + (sizeof(Block) - 1)) / sizeof(Block)) * sizeof(Block)))
+ return false;
+ }
+ else if (Itm.Size != 0)
+ {
+ // Copy the file over the FD
+ auto Size = Itm.Size;
+ unsigned char Junk[32*1024];
+ do
+ {
+ auto const Read = std::min<unsigned long long>(Size, sizeof(Junk));
+ if (not InFd.Read(Junk, ((Read + (sizeof(Block) - 1)) / sizeof(Block)) * sizeof(Block)))
+ return false;
+
+ if (Fd > 0)
+ {
+ if (not FileFd::Write(Fd, Junk, Read))
+ return Stream.Fail(Itm, Fd);
+ }
+ // An Fd of -2 means to send to a special processing function
+ else if (Fd == -2)
+ {
+ if (not Stream.Process(Itm, Junk, Read, Itm.Size - Size))
+ return Stream.Fail(Itm, Fd);
+ }
+
+ Size -= Read;
+ } while (Size != 0);
+ }
+
+ // And finish up
+ if (not BadRecord && not Stream.FinishedFile(Itm, Fd))
+ return false;
+ LastLongName.erase();
+ LastLongLink.erase();
+ }
+
+ return Done();
+}
+ /*}}}*/
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