path: root/methods/rsh.cc

// -*- mode: cpp; mode: fold -*-
// Description								/*{{{*/
/* ######################################################################

   RSH method - Transfer files via rsh compatible program

   Written by Ben Collins <bcollins@debian.org>, Copyright (c) 2000

   This file stated:
   Licensed under the GNU General Public License v2 [no exception clauses]

   We believe that this was intended to be not a statement against future
   versions of the GPL, but meant to exclude the Qt license exception in
   place in APT until that time.

   We received permission from Ben in 2021 to relicense under GPL-2+,
   contributions from Adam Heath and Daniel Hartwig may still have to
   be considered GPL-2 for the time being.

   Other contributions are GPL-2+

   See https://lists.debian.org/deity/2021/04/msg00013.html for details

   ##################################################################### */
									/*}}}*/
// Include Files							/*{{{*/
#include <config.h>

#include <apt-pkg/configuration.h>
#include <apt-pkg/error.h>
#include <apt-pkg/fileutl.h>
#include <apt-pkg/hashes.h>
#include <apt-pkg/strutl.h>

#include "rsh.h"
#include <cerrno>
#include <csignal>
#include <cstdarg>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <sys/stat.h>
#include <sys/time.h>
#include <unistd.h>

#include <apti18n.h>
									/*}}}*/

unsigned long TimeOut = 30;
Configuration::Item const *RshOptions = 0;
time_t RSHMethod::FailTime = 0;
std::string RSHMethod::FailFile;
int RSHMethod::FailFd = -1;

// RSHConn::RSHConn - Constructor					/*{{{*/
// ---------------------------------------------------------------------
/* */
RSHConn::RSHConn(std::string const &pProg, URI Srv) : Len(0), WriteFd(-1), ReadFd(-1),
                            ServerName(Srv), Prog(pProg), Process(-1) {
   Buffer[0] = '\0';
}
									/*}}}*/
// RSHConn::RSHConn - Destructor					/*{{{*/
// ---------------------------------------------------------------------
/* */
RSHConn::~RSHConn()
{
   Close();
}
									/*}}}*/
// RSHConn::Close - Forcibly terminate the connection			/*{{{*/
// ---------------------------------------------------------------------
/* Often this is called when things have gone wrong to indicate that the
   connection is no longer usable. */
void RSHConn::Close()
{
   if (Process == -1)
      return;
   
   close(WriteFd);
   close(ReadFd);
   kill(Process,SIGINT);
   ExecWait(Process,"",true);
   WriteFd = -1;
   ReadFd = -1;
   Process = -1;
}
									/*}}}*/
// RSHConn::Open - Connect to a host					/*{{{*/
// ---------------------------------------------------------------------
/* */
bool RSHConn::Open()
{
   // Use the already open connection if possible.
   if (Process != -1)
      return true;

   if (Connect(ServerName.Host,ServerName.Port,ServerName.User) == false)
      return false;

   return true;
}
									/*}}}*/
// RSHConn::Connect - Fire up rsh and connect				/*{{{*/
// ---------------------------------------------------------------------
/* */
bool RSHConn::Connect(std::string const &Host, unsigned int Port, std::string const &User)
{
   char *PortStr = NULL;
   if (Port != 0)
   {
      if (asprintf (&PortStr, "%d", Port) == -1 || PortStr == NULL)
         return _error->Errno("asprintf", _("Failed"));
   }

   // Create the pipes
   int Pipes[4] = {-1,-1,-1,-1};
   if (pipe(Pipes) != 0 || pipe(Pipes+2) != 0)
   {
      _error->Errno("pipe",_("Failed to create IPC pipe to subprocess"));
      for (int I = 0; I != 4; I++)
	 close(Pipes[I]);
      return false;
   }
   for (int I = 0; I != 4; I++)
      SetCloseExec(Pipes[I],true);
   
   Process = ExecFork();

   // The child
   if (Process == 0)
   {
      const char *Args[400];
      unsigned int i = 0;

      dup2(Pipes[1],STDOUT_FILENO);
      dup2(Pipes[2],STDIN_FILENO);

      // Probably should do
      // dup2(open("/dev/null",O_RDONLY),STDERR_FILENO);

      Args[i++] = Prog.c_str();

      // Insert user-supplied command line options
      Configuration::Item const *Opts = RshOptions;
      if (Opts != 0)
      {
         Opts = Opts->Child;
	 for (; Opts != 0; Opts = Opts->Next)
         {
            if (Opts->Value.empty() == true)
               continue;
            Args[i++] = Opts->Value.c_str();
         }
      }

      if (User.empty() == false) {
         Args[i++] = "-l";
	 Args[i++] = User.c_str();
      }
      if (PortStr != NULL) {
         Args[i++] = "-p";
         Args[i++] = PortStr;
      }
      if (Host.empty() == false) {
         Args[i++] = Host.c_str();
      }
      Args[i++] = "/bin/sh";
      Args[i] = 0;
      execvp(Args[0],(char **)Args);
      exit(100);
   }

   if (PortStr != NULL)
      free(PortStr);

   ReadFd = Pipes[0];
   WriteFd = Pipes[3];
   SetNonBlock(Pipes[0],true);
   SetNonBlock(Pipes[3],true);
   close(Pipes[1]);
   close(Pipes[2]);
   
   return true;
}
bool RSHConn::Connect(std::string const &Host, std::string const &User)
{
   return Connect(Host, 0, User);
}
									/*}}}*/
// RSHConn::ReadLine - Very simple buffered read with timeout		/*{{{*/
// ---------------------------------------------------------------------
/* */
bool RSHConn::ReadLine(std::string &Text)
{
   if (Process == -1 || ReadFd == -1)
      return false;
   
   // Suck in a line
   while (Len < sizeof(Buffer))
   {
      // Scan the buffer for a new line
      for (unsigned int I = 0; I != Len; I++)
      {
         // Escape some special chars
         if (Buffer[I] == 0)
            Buffer[I] = '?';

         // End of line?
         if (Buffer[I] != '\n')
            continue;

         I++;
         Text = std::string(Buffer,I);
         memmove(Buffer,Buffer+I,Len - I);
         Len -= I;
         return true;
      }

      // Wait for some data..
      if (WaitFd(ReadFd,false,TimeOut) == false)
      {
         Close();
         return _error->Error(_("Connection timeout"));
      }

      // Suck it back
      int Res = read(ReadFd,Buffer + Len,sizeof(Buffer) - Len);
      if (Res <= 0)
      {
         _error->Errno("read",_("Read error"));
         Close();
         return false;
      }
      Len += Res;
   }

   return _error->Error(_("A response overflowed the buffer."));
}
									/*}}}*/
// RSHConn::WriteMsg - Send a message with optional remote sync.	/*{{{*/
// ---------------------------------------------------------------------
/* The remote sync flag appends a || echo which will insert blank line
   once the command completes. */
bool RSHConn::WriteMsg(std::string &Text,bool Sync,const char *Fmt,...)
{
   va_list args;
   va_start(args,Fmt);

   // sprintf into a buffer
   char Tmp[1024];
   vsnprintf(Tmp,sizeof(Tmp),Fmt,args);
   va_end(args);

   // concat to create the real msg
   std::string Msg;
   if (Sync == true)
      Msg = std::string(Tmp) + " 2> /dev/null || echo\n";
   else
      Msg = std::string(Tmp) + " 2> /dev/null\n";

   // Send it off
   const char *S = Msg.c_str();
   unsigned long Len = strlen(S);
   unsigned long Start = 0;
   while (Len != 0)
   {
      if (WaitFd(WriteFd,true,TimeOut) == false)
      {
	 
	 Close();
	 return _error->Error(_("Connection timeout"));
      }      
      
      int Res = write(WriteFd,S + Start,Len);
      if (Res <= 0)
      {
         _error->Errno("write",_("Write error"));
         Close();
         return false;
      }

      Len -= Res;
      Start += Res;
   }

   if (Sync == true)
      return ReadLine(Text);
   return true;
}
									/*}}}*/
// RSHConn::Size - Return the size of the file				/*{{{*/
// ---------------------------------------------------------------------
/* Right now for successful transfer the file size must be known in
   advance. */
bool RSHConn::Size(const char *Path,unsigned long long &Size)
{
   // Query the size
	std::string Msg;
   Size = 0;

   if (WriteMsg(Msg,true,"find %s -follow -printf '%%s\\n'",Path) == false)
      return false;
   
   // FIXME: Sense if the bad reply is due to a File Not Found. 
   
   char *End;
   Size = strtoull(Msg.c_str(),&End,10);
   if (End == Msg.c_str())
      return _error->Error(_("File not found"));
   return true;
}
									/*}}}*/
// RSHConn::ModTime - Get the modification time in UTC			/*{{{*/
// ---------------------------------------------------------------------
/* */
bool RSHConn::ModTime(const char *Path, time_t &Time)
{
   Time = time(&Time);
   // Query the mod time
   std::string Msg;

   if (WriteMsg(Msg,true,"TZ=UTC find %s -follow -printf '%%TY%%Tm%%Td%%TH%%TM%%TS\\n'",Path) == false)
      return false;

   // Parse it
   return FTPMDTMStrToTime(Msg.c_str(), Time);
}
									/*}}}*/
// RSHConn::Get - Get a file						/*{{{*/
// ---------------------------------------------------------------------
/* */
bool RSHConn::Get(const char *Path,FileFd &To,unsigned long long Resume,
                  Hashes &Hash,bool &Missing, unsigned long long Size)
{
   Missing = false;

   // Round to a 2048 byte block
   Resume = Resume - (Resume % 2048);

   if (To.Truncate(Resume) == false)
      return false;
   if (To.Seek(0) == false)
      return false;

   if (Resume != 0) {
      if (Hash.AddFD(To,Resume) == false) {
	 _error->Errno("read",_("Problem hashing file"));
	 return false;
      }
   }
   
   // FIXME: Detect file-not openable type errors.
   std::string Jnk;
   if (WriteMsg(Jnk,false,"dd if=%s bs=2048 skip=%u", Path, Resume / 2048) == false)
      return false;

   // Copy loop
   unsigned long long MyLen = Resume;
   unsigned char Buffer[4096];
   while (MyLen < Size)
   {
      // Wait for some data..
      if (WaitFd(ReadFd,false,TimeOut) == false)
      {
         Close();
         return _error->Error(_("Data socket timed out"));
      }

      // Read the data..
      int Res = read(ReadFd,Buffer,sizeof(Buffer));
      if (Res == 0)
      {
	 Close();
	 return _error->Error(_("Connection closed prematurely"));
      }
      
      if (Res < 0)
      {
         if (errno == EAGAIN)
            continue;
         break;
      }
      MyLen += Res;

      Hash.Add(Buffer,Res);
      if (To.Write(Buffer,Res) == false)
      {
         Close();
         return false;
      }
   }

   return true;
}
									/*}}}*/

// RSHMethod::RSHMethod - Constructor					/*{{{*/
RSHMethod::RSHMethod(std::string &&pProg) : aptMethod(std::move(pProg),"1.0",SendConfig | SendURIEncoded)
{
   signal(SIGTERM,SigTerm);
   signal(SIGINT,SigTerm);
   Server = 0;
   FailFd = -1;
}
									/*}}}*/
// RSHMethod::Configuration - Handle a configuration message		/*{{{*/
// ---------------------------------------------------------------------
bool RSHMethod::Configuration(std::string Message)
{
   // enabling privilege dropping for this method requires configuration…
   // … which is otherwise lifted straight from root, so use it by default.
   _config->Set(std::string("Binary::") + Binary + "::APT::Sandbox::User", "");

   if (aptMethod::Configuration(Message) == false)
      return false;

   std::string const timeconf = std::string("Acquire::") + Binary + "::Timeout";
   TimeOut = _config->FindI(timeconf, TimeOut);
   std::string const optsconf = std::string("Acquire::") + Binary + "::Options";
   RshOptions = _config->Tree(optsconf.c_str());

   return true;
}
									/*}}}*/
// RSHMethod::SigTerm - Clean up and timestamp the files on exit	/*{{{*/
// ---------------------------------------------------------------------
/* */
void RSHMethod::SigTerm(int)
{
   if (FailFd == -1)
      _exit(100);

   // Transfer the modification times
   struct timeval times[2];
   times[0].tv_sec = FailTime;
   times[1].tv_sec = FailTime;
   times[0].tv_usec = times[1].tv_usec = 0;
   utimes(FailFile.c_str(), times);
   close(FailFd);

   _exit(100);
}
									/*}}}*/
// RSHMethod::Fetch - Fetch a URI					/*{{{*/
// ---------------------------------------------------------------------
/* */
bool RSHMethod::Fetch(FetchItem *Itm)
{
   URI Get(Itm->Uri);
   auto const File = DecodeSendURI(Get.Path);
   FetchResult Res;
   Res.Filename = Itm->DestFile;
   Res.IMSHit = false;

   // Connect to the server
   if (Server == 0 || Server->Comp(Get) == false) {
      delete Server;
      Server = new RSHConn(Binary, Get);
   }

   // Could not connect is a transient error..
   if (Server->Open() == false) {
      Server->Close();
      Fail(true);
      return true;
   }

   // We say this mainly because the pause here is for the
   // ssh connection that is still going
   Status(_("Connecting to %s"), Get.Host.c_str());

   // Get the files information
   unsigned long long Size;
   if (not Server->Size(File.c_str(), Size) ||
       not Server->ModTime(File.c_str(), FailTime))
   {
      //Fail(true);
      //_error->Error(_("File not found")); // Will be handled by Size
      return false;
   }
   Res.Size = Size;

   // See if it is an IMS hit
   if (Itm->LastModified == FailTime) {
      Res.Size = 0;
      Res.IMSHit = true;
      URIDone(Res);
      return true;
   }

   // See if the file exists
   struct stat Buf;
   if (stat(Itm->DestFile.c_str(),&Buf) == 0) {
      if (Size == (unsigned long long)Buf.st_size && FailTime == Buf.st_mtime) {
	 Res.Size = Buf.st_size;
	 Res.LastModified = Buf.st_mtime;
	 Res.ResumePoint = Buf.st_size;
	 URIDone(Res);
	 return true;
      }

      // Resume?
      if (FailTime == Buf.st_mtime && Size > (unsigned long long)Buf.st_size)
	 Res.ResumePoint = Buf.st_size;
   }

   // Open the file
   Hashes Hash(Itm->ExpectedHashes);
   {
      FileFd Fd(Itm->DestFile,FileFd::WriteAny);
      if (_error->PendingError() == true)
	 return false;
      
      URIStart(Res);

      FailFile = Itm->DestFile;
      (void)(FailFile.c_str()); // Make sure we don't do a malloc in the signal handler
      FailFd = Fd.Fd();

      bool Missing;
      if (not Server->Get(File.c_str(), Fd, Res.ResumePoint, Hash, Missing, Res.Size))
      {
	 Fd.Close();

	 // Timestamp
	 struct timeval times[2];
	 times[0].tv_sec = FailTime;
	 times[1].tv_sec = FailTime;
	 times[0].tv_usec = times[1].tv_usec = 0;
	 utimes(FailFile.c_str(), times);

	 // If the file is missing we hard fail otherwise transient fail
	 if (Missing == true)
	    return false;
	 Fail(true);
	 return true;
      }

      Res.Size = Fd.Size();
      struct timeval times[2];
      times[0].tv_sec = FailTime;
      times[1].tv_sec = FailTime;
      times[0].tv_usec = times[1].tv_usec = 0;
      utimes(Fd.Name().c_str(), times);
      FailFd = -1;
   }

   Res.LastModified = FailTime;
   Res.TakeHashes(Hash);

   URIDone(Res);

   return true;
}
									/*}}}*/

int main(int, const char *argv[])
{
   return RSHMethod(flNotDir(argv[0])).Run();
}