apt/methods/connect.cc

// -*- mode: cpp; mode: fold -*-
// Description								/*{{{*/
// $Id: connect.cc,v 1.10.2.1 2004/01/16 18:58:50 mdz Exp $
/* ######################################################################

   Connect - Replacement connect call

   This was originally authored by Jason Gunthorpe <jgg@debian.org>
   and is placed in the Public Domain, do with it what you will.
      
   ##################################################################### */
									/*}}}*/
// Include Files							/*{{{*/
#include <config.h>

#include <apt-pkg/error.h>
#include <apt-pkg/fileutl.h>
#include <apt-pkg/strutl.h>
#include <apt-pkg/acquire-method.h>
#include <apt-pkg/configuration.h>
#include <apt-pkg/srvrec.h>

#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <sstream>
#include <string.h>
#include<set>
#include<string>

// Internet stuff
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>

#include "connect.h"
#include "rfc2553emu.h"
#include <apti18n.h>
									/*}}}*/

static std::string LastHost;
static int LastPort = 0;
static struct addrinfo *LastHostAddr = 0;
static struct addrinfo *LastUsed = 0;

static std::vector<SrvRec> SrvRecords;

// Set of IP/hostnames that we timed out before or couldn't resolve
static std::set<std::string> bad_addr;

// RotateDNS - Select a new server from a DNS rotation			/*{{{*/
// ---------------------------------------------------------------------
/* This is called during certain errors in order to recover by selecting a 
   new server */
void RotateDNS()
{
   if (LastUsed != 0 && LastUsed->ai_next != 0)
      LastUsed = LastUsed->ai_next;
   else
      LastUsed = LastHostAddr;
}
									/*}}}*/
static bool ConnectionAllowed(char const * const Service, std::string const &Host)/*{{{*/
{
   if (unlikely(Host.empty())) // the only legal empty host (RFC2782 '.' target) is detected by caller
      return false;
   if (APT::String::Endswith(Host, ".onion") && _config->FindB("Acquire::BlockDotOnion", true))
   {
      // TRANSLATOR: %s is e.g. Tor's ".onion" which would likely fail or leak info (RFC7686)
      _error->Error(_("Direct connection to %s domains is blocked by default."), ".onion");
      if (strcmp(Service, "http") == 0)
	_error->Error(_("If you meant to use Tor remember to use %s instead of %s."), "tor+http", "http");
      return false;
   }
   return true;
}
									/*}}}*/
// DoConnect - Attempt a connect operation				/*{{{*/
// ---------------------------------------------------------------------
/* This helper function attempts a connection to a single address. */
static bool DoConnect(struct addrinfo *Addr,std::string const &Host,
		      unsigned long TimeOut,int &Fd,pkgAcqMethod *Owner)
{
   // Show a status indicator
   char Name[NI_MAXHOST];
   char Service[NI_MAXSERV];
   
   Name[0] = 0;   
   Service[0] = 0;
   getnameinfo(Addr->ai_addr,Addr->ai_addrlen,
	       Name,sizeof(Name),Service,sizeof(Service),
	       NI_NUMERICHOST|NI_NUMERICSERV);
   Owner->Status(_("Connecting to %s (%s)"),Host.c_str(),Name);

   // if that addr did timeout before, we do not try it again
   if(bad_addr.find(std::string(Name)) != bad_addr.end())
      return false;

   /* If this is an IP rotation store the IP we are using.. If something goes
      wrong this will get tacked onto the end of the error message */
   if (LastHostAddr->ai_next != 0)
   {
      std::stringstream ss;
      ioprintf(ss, _("[IP: %s %s]"),Name,Service);
      Owner->SetIP(ss.str());
   }
      
   // Get a socket
   if ((Fd = socket(Addr->ai_family,Addr->ai_socktype,
		    Addr->ai_protocol)) < 0)
      return _error->Errno("socket",_("Could not create a socket for %s (f=%u t=%u p=%u)"),
			   Name,Addr->ai_family,Addr->ai_socktype,Addr->ai_protocol);
   
   SetNonBlock(Fd,true);
   if (connect(Fd,Addr->ai_addr,Addr->ai_addrlen) < 0 &&
       errno != EINPROGRESS)
      return _error->Errno("connect",_("Cannot initiate the connection "
			   "to %s:%s (%s)."),Host.c_str(),Service,Name);
   
   /* This implements a timeout for connect by opening the connection
      nonblocking */
   if (WaitFd(Fd,true,TimeOut) == false) {
      bad_addr.insert(bad_addr.begin(), std::string(Name));
      Owner->SetFailReason("Timeout");
      return _error->Error(_("Could not connect to %s:%s (%s), "
			   "connection timed out"),Host.c_str(),Service,Name);
   }

   // Check the socket for an error condition
   unsigned int Err;
   unsigned int Len = sizeof(Err);
   if (getsockopt(Fd,SOL_SOCKET,SO_ERROR,&Err,&Len) != 0)
      return _error->Errno("getsockopt",_("Failed"));
   
   if (Err != 0)
   {
      errno = Err;
      if(errno == ECONNREFUSED)
         Owner->SetFailReason("ConnectionRefused");
      else if (errno == ETIMEDOUT)
	 Owner->SetFailReason("ConnectionTimedOut");
      bad_addr.insert(bad_addr.begin(), std::string(Name));
      return _error->Errno("connect",_("Could not connect to %s:%s (%s)."),Host.c_str(),
			   Service,Name);
   }
   
   return true;
}
									/*}}}*/
// Connect to a given Hostname						/*{{{*/
static bool ConnectToHostname(std::string const &Host, int const Port,
      const char * const Service, int DefPort, int &Fd,
      unsigned long const TimeOut, pkgAcqMethod * const Owner)
{
   if (ConnectionAllowed(Service, Host) == false)
      return false;
   // Convert the port name/number
   char ServStr[300];
   if (Port != 0)
      snprintf(ServStr,sizeof(ServStr),"%i", Port);
   else
      snprintf(ServStr,sizeof(ServStr),"%s", Service);
   
   /* We used a cached address record.. Yes this is against the spec but
      the way we have setup our rotating dns suggests that this is more
      sensible */
   if (LastHost != Host || LastPort != Port)
   {
      Owner->Status(_("Connecting to %s"),Host.c_str());

      // Free the old address structure
      if (LastHostAddr != 0)
      {
	 freeaddrinfo(LastHostAddr);
	 LastHostAddr = 0;
	 LastUsed = 0;
      }
      
      // We only understand SOCK_STREAM sockets.
      struct addrinfo Hints;
      memset(&Hints,0,sizeof(Hints));
      Hints.ai_socktype = SOCK_STREAM;
      Hints.ai_flags = 0;
#ifdef AI_IDN
      if (_config->FindB("Acquire::Connect::IDN", true) == true)
	 Hints.ai_flags |= AI_IDN;
#endif
      // see getaddrinfo(3): only return address if system has such a address configured
      // useful if system is ipv4 only, to not get ipv6, but that fails if the system has
      // no address configured: e.g. offline and trying to connect to localhost.
      if (_config->FindB("Acquire::Connect::AddrConfig", true) == true)
	 Hints.ai_flags |= AI_ADDRCONFIG;
      Hints.ai_protocol = 0;
      
      if(_config->FindB("Acquire::ForceIPv4", false) == true)
         Hints.ai_family = AF_INET;
      else if(_config->FindB("Acquire::ForceIPv6", false) == true)
         Hints.ai_family = AF_INET6;
      else
         Hints.ai_family = AF_UNSPEC;

      // if we couldn't resolve the host before, we don't try now
      if(bad_addr.find(Host) != bad_addr.end()) 
	 return _error->Error(_("Could not resolve '%s'"),Host.c_str());

      // Resolve both the host and service simultaneously
      while (1)
      {
	 int Res;
	 if ((Res = getaddrinfo(Host.c_str(),ServStr,&Hints,&LastHostAddr)) != 0 ||
	     LastHostAddr == 0)
	 {
	    if (Res == EAI_NONAME || Res == EAI_SERVICE)
	    {
	       if (DefPort != 0)
	       {
		  snprintf(ServStr, sizeof(ServStr), "%i", DefPort);
		  DefPort = 0;
		  continue;
	       }
	       bad_addr.insert(bad_addr.begin(), Host);
	       Owner->SetFailReason("ResolveFailure");
	       return _error->Error(_("Could not resolve '%s'"),Host.c_str());
	    }
	    
	    if (Res == EAI_AGAIN)
	    {
	       Owner->SetFailReason("TmpResolveFailure");
	       return _error->Error(_("Temporary failure resolving '%s'"),
				    Host.c_str());
	    }
	    if (Res == EAI_SYSTEM)
	       return _error->Errno("getaddrinfo", _("System error resolving '%s:%s'"),
                                      Host.c_str(),ServStr);
	    return _error->Error(_("Something wicked happened resolving '%s:%s' (%i - %s)"),
				 Host.c_str(),ServStr,Res,gai_strerror(Res));
	 }
	 break;
      }
      
      LastHost = Host;
      LastPort = Port;
   }

   // When we have an IP rotation stay with the last IP.
   struct addrinfo *CurHost = LastHostAddr;
   if (LastUsed != 0)
       CurHost = LastUsed;
   
   while (CurHost != 0)
   {
      if (DoConnect(CurHost,Host,TimeOut,Fd,Owner) == true)
      {
	 LastUsed = CurHost;
	 return true;
      }      
      close(Fd);
      Fd = -1;
      
      // Ignore UNIX domain sockets
      do
      {
	 CurHost = CurHost->ai_next;
      }
      while (CurHost != 0 && CurHost->ai_family == AF_UNIX);

      /* If we reached the end of the search list then wrap around to the
         start */
      if (CurHost == 0 && LastUsed != 0)
	 CurHost = LastHostAddr;
      
      // Reached the end of the search cycle
      if (CurHost == LastUsed)
	 break;
      
      if (CurHost != 0)
	 _error->Discard();
   }   

   if (_error->PendingError() == true)
      return false;   
   return _error->Error(_("Unable to connect to %s:%s:"),Host.c_str(),ServStr);
}
									/*}}}*/
// Connect - Connect to a server					/*{{{*/
// ---------------------------------------------------------------------
/* Performs a connection to the server (including SRV record lookup) */
bool Connect(std::string Host,int Port,const char *Service,
                            int DefPort,int &Fd,
                            unsigned long TimeOut,pkgAcqMethod *Owner)
{
   if (_error->PendingError() == true)
      return false;

   if (ConnectionAllowed(Service, Host) == false)
      return false;

   if(LastHost != Host || LastPort != Port)
   {
      SrvRecords.clear();
      if (_config->FindB("Acquire::EnableSrvRecords", true) == true)
      {
         GetSrvRecords(Host, DefPort, SrvRecords);
	 // RFC2782 defines that a lonely '.' target is an abort reason
	 if (SrvRecords.size() == 1 && SrvRecords[0].target.empty())
	    return _error->Error("SRV records for %s indicate that "
		  "%s service is not available at this domain", Host.c_str(), Service);
      }
   }

   size_t stackSize = 0;
   // try to connect in the priority order of the srv records
   std::string initialHost{std::move(Host)};
   while(SrvRecords.empty() == false)
   {
      _error->PushToStack();
      ++stackSize;
      // PopFromSrvRecs will also remove the server
      Host = PopFromSrvRecs(SrvRecords).target;
      auto const ret = ConnectToHostname(Host, Port, Service, DefPort, Fd, TimeOut, Owner);
      if (ret)
      {
	 while(stackSize--)
	    _error->RevertToStack();
         return true;
      }
   }
   Host = std::move(initialHost);

   // we have no (good) SrvRecords for this host, connect right away
   _error->PushToStack();
   ++stackSize;
   auto const ret = ConnectToHostname(Host, Port, Service, DefPort, Fd,
	 TimeOut, Owner);
   while(stackSize--)
      if (ret)
	 _error->RevertToStack();
      else
	 _error->MergeWithStack();
   return ret;
}