]> git.saurik.com Git - apt.git/blobdiff - apt-pkg/acquire.cc
CMake: Add coverage build type
[apt.git] / apt-pkg / acquire.cc
index 9060d492b8d5bce46a98d795219455b8bb05b3d2..2ad6bc47f91c3a846ce658faeaab84acd37eda6c 100644 (file)
 #include <apt-pkg/strutl.h>
 #include <apt-pkg/fileutl.h>
 
+#include <algorithm>
+#include <numeric>
 #include <string>
 #include <vector>
 #include <iostream>
 #include <sstream>
+#include <iomanip>
+#include <memory>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
-#include <iomanip>
-
+#include <fcntl.h>
+#include <pwd.h>
+#include <grp.h>
 #include <dirent.h>
 #include <sys/time.h>
 #include <sys/select.h>
@@ -47,56 +53,114 @@ using namespace std;
 // Acquire::pkgAcquire - Constructor                                   /*{{{*/
 // ---------------------------------------------------------------------
 /* We grab some runtime state from the configuration space */
-pkgAcquire::pkgAcquire() : LockFD(-1), Queues(0), Workers(0), Configs(0), Log(NULL), ToFetch(0),
+pkgAcquire::pkgAcquire() : LockFD(-1), d(NULL), Queues(0), Workers(0), Configs(0), Log(NULL), ToFetch(0),
                           Debug(_config->FindB("Debug::pkgAcquire",false)),
                           Running(false)
 {
-   string const Mode = _config->Find("Acquire::Queue-Mode","host");
-   if (strcasecmp(Mode.c_str(),"host") == 0)
-      QueueMode = QueueHost;
-   if (strcasecmp(Mode.c_str(),"access") == 0)
-      QueueMode = QueueAccess;
+   Initialize();
 }
-pkgAcquire::pkgAcquire(pkgAcquireStatus *Progress) :  LockFD(-1), Queues(0), Workers(0),
-                          Configs(0), Log(Progress), ToFetch(0),
+pkgAcquire::pkgAcquire(pkgAcquireStatus *Progress) : LockFD(-1), d(NULL), Queues(0), Workers(0),
+                          Configs(0), Log(NULL), ToFetch(0),
                           Debug(_config->FindB("Debug::pkgAcquire",false)),
                           Running(false)
+{
+   Initialize();
+   SetLog(Progress);
+}
+void pkgAcquire::Initialize()
 {
    string const Mode = _config->Find("Acquire::Queue-Mode","host");
    if (strcasecmp(Mode.c_str(),"host") == 0)
       QueueMode = QueueHost;
    if (strcasecmp(Mode.c_str(),"access") == 0)
       QueueMode = QueueAccess;
-   Setup(Progress, "");
+
+   // chown the auth.conf file as it will be accessed by our methods
+   std::string const SandboxUser = _config->Find("APT::Sandbox::User");
+   if (getuid() == 0 && SandboxUser.empty() == false && SandboxUser != "root") // if we aren't root, we can't chown, so don't try it
+   {
+      struct passwd const * const pw = getpwnam(SandboxUser.c_str());
+      struct group const * const gr = getgrnam(ROOT_GROUP);
+      if (pw != NULL && gr != NULL)
+      {
+        std::string const AuthConf = _config->FindFile("Dir::Etc::netrc");
+        if(AuthConf.empty() == false && RealFileExists(AuthConf) &&
+              chown(AuthConf.c_str(), pw->pw_uid, gr->gr_gid) != 0)
+           _error->WarningE("SetupAPTPartialDirectory", "chown to %s:root of file %s failed", SandboxUser.c_str(), AuthConf.c_str());
+      }
+   }
 }
                                                                        /*}}}*/
-// Acquire::Setup - Delayed Constructor                                        /*{{{*/
-// ---------------------------------------------------------------------
-/* Do everything needed to be a complete Acquire object and report the
-   success (or failure) back so the user knows that something is wrong… */
+// Acquire::GetLock - lock directory and prepare for action            /*{{{*/
+static bool SetupAPTPartialDirectory(std::string const &grand, std::string const &parent)
+{
+   std::string const partial = parent + "partial";
+   mode_t const mode = umask(S_IWGRP | S_IWOTH);
+   bool const creation_fail = (CreateAPTDirectoryIfNeeded(grand, partial) == false &&
+        CreateAPTDirectoryIfNeeded(parent, partial) == false);
+   umask(mode);
+   if (creation_fail == true)
+      return false;
+
+   std::string const SandboxUser = _config->Find("APT::Sandbox::User");
+   if (getuid() == 0 && SandboxUser.empty() == false && SandboxUser != "root") // if we aren't root, we can't chown, so don't try it
+   {
+      struct passwd const * const pw = getpwnam(SandboxUser.c_str());
+      struct group const * const gr = getgrnam(ROOT_GROUP);
+      if (pw != NULL && gr != NULL)
+      {
+         // chown the partial dir
+         if(chown(partial.c_str(), pw->pw_uid, gr->gr_gid) != 0)
+            _error->WarningE("SetupAPTPartialDirectory", "chown to %s:root of directory %s failed", SandboxUser.c_str(), partial.c_str());
+      }
+   }
+   if (chmod(partial.c_str(), 0700) != 0)
+      _error->WarningE("SetupAPTPartialDirectory", "chmod 0700 of directory %s failed", partial.c_str());
+
+   return true;
+}
 bool pkgAcquire::Setup(pkgAcquireStatus *Progress, string const &Lock)
 {
    Log = Progress;
+   if (Lock.empty())
+   {
+      string const listDir = _config->FindDir("Dir::State::lists");
+      if (SetupAPTPartialDirectory(_config->FindDir("Dir::State"), listDir) == false)
+        return _error->Errno("Acquire", _("List directory %spartial is missing."), listDir.c_str());
+      string const archivesDir = _config->FindDir("Dir::Cache::Archives");
+      if (SetupAPTPartialDirectory(_config->FindDir("Dir::Cache"), archivesDir) == false)
+        return _error->Errno("Acquire", _("Archives directory %spartial is missing."), archivesDir.c_str());
+      return true;
+   }
+   return GetLock(Lock);
+}
+bool pkgAcquire::GetLock(std::string const &Lock)
+{
+   if (Lock.empty() == true)
+      return false;
 
    // check for existence and possibly create auxiliary directories
    string const listDir = _config->FindDir("Dir::State::lists");
-   string const partialListDir = listDir + "partial/";
    string const archivesDir = _config->FindDir("Dir::Cache::Archives");
-   string const partialArchivesDir = archivesDir + "partial/";
-
-   if (CreateAPTDirectoryIfNeeded(_config->FindDir("Dir::State"), partialListDir) == false &&
-       CreateAPTDirectoryIfNeeded(listDir, partialListDir) == false)
-      return _error->Errno("Acquire", _("List directory %spartial is missing."), listDir.c_str());
 
-   if (CreateAPTDirectoryIfNeeded(_config->FindDir("Dir::Cache"), partialArchivesDir) == false &&
-       CreateAPTDirectoryIfNeeded(archivesDir, partialArchivesDir) == false)
-      return _error->Errno("Acquire", _("Archives directory %spartial is missing."), archivesDir.c_str());
+   if (Lock == listDir)
+   {
+      if (SetupAPTPartialDirectory(_config->FindDir("Dir::State"), listDir) == false)
+        return _error->Errno("Acquire", _("List directory %spartial is missing."), listDir.c_str());
+   }
+   if (Lock == archivesDir)
+   {
+      if (SetupAPTPartialDirectory(_config->FindDir("Dir::Cache"), archivesDir) == false)
+        return _error->Errno("Acquire", _("Archives directory %spartial is missing."), archivesDir.c_str());
+   }
 
-   if (Lock.empty() == true || _config->FindB("Debug::NoLocking", false) == true)
+   if (_config->FindB("Debug::NoLocking", false) == true)
       return true;
 
    // Lock the directory this acquire object will work in
-   LockFD = GetLock(flCombine(Lock, "lock"));
+   if (LockFD != -1)
+      close(LockFD);
+   LockFD = ::GetLock(flCombine(Lock, "lock"));
    if (LockFD == -1)
       return _error->Error(_("Unable to lock directory %s"), Lock.c_str());
 
@@ -205,6 +269,42 @@ void pkgAcquire::Remove(Worker *Work)
    it is constructed which creates a queue (based on the current queue
    mode) and puts the item in that queue. If the system is running then
    the queue might be started. */
+static bool CheckForBadItemAndFailIt(pkgAcquire::Item * const Item,
+      pkgAcquire::MethodConfig const * const Config, pkgAcquireStatus * const Log)
+{
+   auto SavedDesc = Item->GetItemDesc();
+   if (Item->IsRedirectionLoop(SavedDesc.URI))
+   {
+      std::string const Message = "400 URI Failure"
+        "\nURI: " + SavedDesc.URI +
+        "\nFilename: " + Item->DestFile +
+        "\nFailReason: RedirectionLoop";
+
+      Item->Status = pkgAcquire::Item::StatError;
+      Item->Failed(Message, Config);
+      if (Log != nullptr)
+        Log->Fail(SavedDesc);
+      return true;
+   }
+
+   HashStringList const hsl = Item->GetExpectedHashes();
+   if (hsl.usable() == false && Item->HashesRequired() &&
+        _config->Exists("Acquire::ForceHash") == false)
+   {
+      std::string const Message = "400 URI Failure"
+        "\nURI: " + SavedDesc.URI +
+        "\nFilename: " + Item->DestFile +
+        "\nFailReason: WeakHashSums";
+
+      auto SavedDesc = Item->GetItemDesc();
+      Item->Status = pkgAcquire::Item::StatAuthError;
+      Item->Failed(Message, Config);
+      if (Log != nullptr)
+        Log->Fail(SavedDesc);
+      return true;
+   }
+   return false;
+}
 void pkgAcquire::Enqueue(ItemDesc &Item)
 {
    // Determine which queue to put the item in
@@ -213,6 +313,13 @@ void pkgAcquire::Enqueue(ItemDesc &Item)
    if (Name.empty() == true)
       return;
 
+   /* the check for running avoids that we produce errors
+      in logging before we actually have started, which would
+      be easier to implement but would confuse users/implementations
+      so we check the items skipped here in #Startup */
+   if (Running && CheckForBadItemAndFailIt(Item.Owner, Config, Log))
+      return;
+
    // Find the queue structure
    Queue *I = Queues;
    for (; I != 0 && I->Name != Name; I = I->Next);
@@ -287,8 +394,42 @@ string pkgAcquire::QueueName(string Uri,MethodConfig const *&Config)
    if (Config->SingleInstance == true || QueueMode == QueueAccess)
       return U.Access;
 
-   string AccessSchema = U.Access + ':',
-       FullQueueName = AccessSchema + U.Host;
+   string AccessSchema = U.Access + ':';
+   string FullQueueName;
+
+   if (U.Host.empty())
+   {
+      long existing = 0;
+      // check how many queues exist already and reuse empty ones
+      for (Queue const *I = Queues; I != 0; I = I->Next)
+        if (I->Name.compare(0, AccessSchema.length(), AccessSchema) == 0)
+        {
+           if (I->Items == nullptr)
+              return I->Name;
+           ++existing;
+        }
+
+#ifdef _SC_NPROCESSORS_ONLN
+      long cpuCount = sysconf(_SC_NPROCESSORS_ONLN) * 2;
+#else
+      long cpuCount = 10;
+#endif
+      cpuCount = _config->FindI("Acquire::QueueHost::Limit", cpuCount);
+
+      if (cpuCount <= 0 || existing < cpuCount)
+        strprintf(FullQueueName, "%s%ld", AccessSchema.c_str(), existing);
+      else
+      {
+        long const randomQueue = random() % cpuCount;
+        strprintf(FullQueueName, "%s%ld", AccessSchema.c_str(), randomQueue);
+      }
+
+      if (Debug)
+         clog << "Chose random queue " << FullQueueName << " for " << Uri << endl;
+   } else
+   {
+      FullQueueName = AccessSchema + U.Host;
+   }
    unsigned int Instances = 0, SchemaLength = AccessSchema.length();
 
    Queue *I = Queues;
@@ -364,20 +505,30 @@ void pkgAcquire::SetFds(int &Fd,fd_set *RSet,fd_set *WSet)
    }
 }
                                                                        /*}}}*/
-// Acquire::RunFds - Deal with active FDs                              /*{{{*/
+// Acquire::RunFds - compatibility remove on next abi/api break                /*{{{*/
+void pkgAcquire::RunFds(fd_set *RSet,fd_set *WSet)
+{
+   RunFdsSane(RSet, WSet);
+}
+                                                                       /*}}}*/
+// Acquire::RunFdsSane - Deal with active FDs                          /*{{{*/
 // ---------------------------------------------------------------------
 /* Dispatch active FDs over to the proper workers. It is very important
    that a worker never be erased while this is running! The queue class
    should never erase a worker except during shutdown processing. */
-void pkgAcquire::RunFds(fd_set *RSet,fd_set *WSet)
+bool pkgAcquire::RunFdsSane(fd_set *RSet,fd_set *WSet)
 {
+   bool Res = true;
+
    for (Worker *I = Workers; I != 0; I = I->NextAcquire)
    {
       if (I->InFd >= 0 && FD_ISSET(I->InFd,RSet) != 0)
-        I->InFdReady();
+        Res &= I->InFdReady();
       if (I->OutFd >= 0 && FD_ISSET(I->OutFd,WSet) != 0)
-        I->OutFdReady();
+        Res &= I->OutFdReady();
    }
+
+   return Res;
 }
                                                                        /*}}}*/
 // Acquire::Run - Run the fetch sequence                               /*{{{*/
@@ -385,8 +536,129 @@ void pkgAcquire::RunFds(fd_set *RSet,fd_set *WSet)
 /* This runs the queues. It manages a select loop for all of the
    Worker tasks. The workers interact with the queues and items to
    manage the actual fetch. */
+static bool IsAccessibleBySandboxUser(std::string const &filename, bool const ReadWrite)
+{
+   // you would think this is easily to answer with faccessat, right? Wrong!
+   // It e.g. gets groups wrong, so the only thing which works reliable is trying
+   // to open the file we want to open later on…
+   if (unlikely(filename.empty()))
+      return true;
+
+   if (ReadWrite == false)
+   {
+      errno = 0;
+      // can we read a file? Note that non-existing files are "fine"
+      int const fd = open(filename.c_str(), O_RDONLY | O_CLOEXEC);
+      if (fd == -1 && errno == EACCES)
+        return false;
+      close(fd);
+      return true;
+   }
+   else
+   {
+      // the file might not exist yet and even if it does we will fix permissions,
+      // so important is here just that the directory it is in allows that
+      std::string const dirname = flNotFile(filename);
+      if (unlikely(dirname.empty()))
+        return true;
+
+      char const * const filetag = ".apt-acquire-privs-test.XXXXXX";
+      std::string const tmpfile_tpl = flCombine(dirname, filetag);
+      std::unique_ptr<char, decltype(std::free) *> tmpfile { strdup(tmpfile_tpl.c_str()), std::free };
+      int const fd = mkstemp(tmpfile.get());
+      if (fd == -1 && errno == EACCES)
+        return false;
+      RemoveFile("IsAccessibleBySandboxUser", tmpfile.get());
+      close(fd);
+      return true;
+   }
+}
+static void CheckDropPrivsMustBeDisabled(pkgAcquire const &Fetcher)
+{
+   if(getuid() != 0)
+      return;
+
+   std::string const SandboxUser = _config->Find("APT::Sandbox::User");
+   if (SandboxUser.empty() || SandboxUser == "root")
+      return;
+
+   struct passwd const * const pw = getpwnam(SandboxUser.c_str());
+   if (pw == NULL)
+   {
+      _error->Warning(_("No sandbox user '%s' on the system, can not drop privileges"), SandboxUser.c_str());
+      _config->Set("APT::Sandbox::User", "");
+      return;
+   }
+
+   gid_t const old_euid = geteuid();
+   gid_t const old_egid = getegid();
+
+   long const ngroups_max = sysconf(_SC_NGROUPS_MAX);
+   std::unique_ptr<gid_t[]> old_gidlist(new gid_t[ngroups_max]);
+   if (unlikely(old_gidlist == NULL))
+      return;
+   ssize_t old_gidlist_nr;
+   if ((old_gidlist_nr = getgroups(ngroups_max, old_gidlist.get())) < 0)
+   {
+      _error->FatalE("getgroups", "getgroups %lu failed", ngroups_max);
+      old_gidlist[0] = 0;
+      old_gidlist_nr = 1;
+   }
+   if (setgroups(1, &pw->pw_gid))
+      _error->FatalE("setgroups", "setgroups %u failed", pw->pw_gid);
+
+   if (setegid(pw->pw_gid) != 0)
+      _error->FatalE("setegid", "setegid %u failed", pw->pw_gid);
+   if (seteuid(pw->pw_uid) != 0)
+      _error->FatalE("seteuid", "seteuid %u failed", pw->pw_uid);
+
+   for (pkgAcquire::ItemCIterator I = Fetcher.ItemsBegin();
+       I != Fetcher.ItemsEnd(); ++I)
+   {
+      // no need to drop privileges for a complete file
+      if ((*I)->Complete == true || (*I)->Status != pkgAcquire::Item::StatIdle)
+        continue;
+
+      // if destination file is inaccessible all hope is lost for privilege dropping
+      if (IsAccessibleBySandboxUser((*I)->DestFile, true) == false)
+      {
+        _error->WarningE("pkgAcquire::Run", _("Can't drop privileges for downloading as file '%s' couldn't be accessed by user '%s'."),
+              (*I)->DestFile.c_str(), SandboxUser.c_str());
+        _config->Set("APT::Sandbox::User", "");
+        break;
+      }
+
+      // if its the source file (e.g. local sources) we might be lucky
+      // by dropping the dropping only for some methods.
+      URI const source = (*I)->DescURI();
+      if (source.Access == "file" || source.Access == "copy")
+      {
+        std::string const conf = "Binary::" + source.Access + "::APT::Sandbox::User";
+        if (_config->Exists(conf) == true)
+           continue;
+
+        if (IsAccessibleBySandboxUser(source.Path, false) == false)
+        {
+           _error->NoticeE("pkgAcquire::Run", _("Can't drop privileges for downloading as file '%s' couldn't be accessed by user '%s'."),
+                 source.Path.c_str(), SandboxUser.c_str());
+           _config->CndSet("Binary::file::APT::Sandbox::User", "root");
+           _config->CndSet("Binary::copy::APT::Sandbox::User", "root");
+        }
+      }
+   }
+
+   if (seteuid(old_euid) != 0)
+      _error->FatalE("seteuid", "seteuid %u failed", old_euid);
+   if (setegid(old_egid) != 0)
+      _error->FatalE("setegid", "setegid %u failed", old_egid);
+   if (setgroups(old_gidlist_nr, old_gidlist.get()))
+      _error->FatalE("setgroups", "setgroups %u failed", 0);
+}
 pkgAcquire::RunResult pkgAcquire::Run(int PulseIntervall)
 {
+   _error->PushToStack();
+   CheckDropPrivsMustBeDisabled(*this);
+
    Running = true;
    
    for (Queue *I = Queues; I != 0; I = I->Next)
@@ -422,11 +694,10 @@ pkgAcquire::RunResult pkgAcquire::Run(int PulseIntervall)
         _error->Errno("select","Select has failed");
         break;
       }
-            
-      RunFds(&RFds,&WFds);
-      if (_error->PendingError() == true)
-        break;
-      
+
+      if(RunFdsSane(&RFds,&WFds) == false)
+         break;
+
       // Timeout, notify the log class
       if (Res == 0 || (Log != 0 && Log->Update == true))
       {
@@ -451,9 +722,11 @@ pkgAcquire::RunResult pkgAcquire::Run(int PulseIntervall)
 
    // Shut down the items
    for (ItemIterator I = Items.begin(); I != Items.end(); ++I)
-      (*I)->Finished(); 
-   
-   if (_error->PendingError())
+      (*I)->Finished();
+
+   bool const newError = _error->PendingError();
+   _error->MergeWithStack();
+   if (newError)
       return Failed;
    if (WasCancelled)
       return Cancelled;
@@ -507,6 +780,7 @@ bool pkgAcquire::Clean(string Dir)
       // Skip some files..
       if (strcmp(Dir->d_name,"lock") == 0 ||
          strcmp(Dir->d_name,"partial") == 0 ||
+         strcmp(Dir->d_name,"lost+found") == 0 ||
          strcmp(Dir->d_name,".") == 0 ||
          strcmp(Dir->d_name,"..") == 0)
         continue;
@@ -519,7 +793,7 @@ bool pkgAcquire::Clean(string Dir)
       
       // Nothing found, nuke it
       if (I == Items.end())
-        unlink(Dir->d_name);
+        RemoveFile("Clean", Dir->d_name);
    };
    
    closedir(D);
@@ -533,10 +807,10 @@ bool pkgAcquire::Clean(string Dir)
 /* This is the total number of bytes needed */
 APT_PURE unsigned long long pkgAcquire::TotalNeeded()
 {
-   unsigned long long Total = 0;
-   for (ItemCIterator I = ItemsBegin(); I != ItemsEnd(); ++I)
-      Total += (*I)->FileSize;
-   return Total;
+   return std::accumulate(ItemsBegin(), ItemsEnd(), 0llu,
+      [](unsigned long long const T, Item const * const I) {
+        return T + I->FileSize;
+   });
 }
                                                                        /*}}}*/
 // Acquire::FetchNeeded - Number of bytes needed to get                        /*{{{*/
@@ -544,11 +818,13 @@ APT_PURE unsigned long long pkgAcquire::TotalNeeded()
 /* This is the number of bytes that is not local */
 APT_PURE unsigned long long pkgAcquire::FetchNeeded()
 {
-   unsigned long long Total = 0;
-   for (ItemCIterator I = ItemsBegin(); I != ItemsEnd(); ++I)
-      if ((*I)->Local == false)
-        Total += (*I)->FileSize;
-   return Total;
+   return std::accumulate(ItemsBegin(), ItemsEnd(), 0llu,
+      [](unsigned long long const T, Item const * const I) {
+        if (I->Local == false)
+           return T + I->FileSize;
+        else
+           return T;
+   });
 }
                                                                        /*}}}*/
 // Acquire::PartialPresent - Number of partial bytes we already have   /*{{{*/
@@ -556,11 +832,13 @@ APT_PURE unsigned long long pkgAcquire::FetchNeeded()
 /* This is the number of bytes that is not local */
 APT_PURE unsigned long long pkgAcquire::PartialPresent()
 {
-  unsigned long long Total = 0;
-   for (ItemCIterator I = ItemsBegin(); I != ItemsEnd(); ++I)
-      if ((*I)->Local == false)
-        Total += (*I)->PartialSize;
-   return Total;
+   return std::accumulate(ItemsBegin(), ItemsEnd(), 0llu,
+      [](unsigned long long const T, Item const * const I) {
+        if (I->Local == false)
+           return T + I->PartialSize;
+        else
+           return T;
+   });
 }
                                                                        /*}}}*/
 // Acquire::UriBegin - Start iterator for the uri list                 /*{{{*/
@@ -582,27 +860,18 @@ pkgAcquire::UriIterator pkgAcquire::UriEnd()
 // Acquire::MethodConfig::MethodConfig - Constructor                   /*{{{*/
 // ---------------------------------------------------------------------
 /* */
-pkgAcquire::MethodConfig::MethodConfig()
+pkgAcquire::MethodConfig::MethodConfig() : d(NULL), Next(0), SingleInstance(false),
+   Pipeline(false), SendConfig(false), LocalOnly(false), NeedsCleanup(false),
+   Removable(false)
 {
-   SingleInstance = false;
-   Pipeline = false;
-   SendConfig = false;
-   LocalOnly = false;
-   Removable = false;
-   Next = 0;
 }
                                                                        /*}}}*/
 // Queue::Queue - Constructor                                          /*{{{*/
 // ---------------------------------------------------------------------
 /* */
-pkgAcquire::Queue::Queue(string Name,pkgAcquire *Owner) : Name(Name), 
-            Owner(Owner)
+pkgAcquire::Queue::Queue(string const &name,pkgAcquire * const owner) : d(NULL), Next(0),
+   Name(name), Items(0), Workers(0), Owner(owner), PipeDepth(0), MaxPipeDepth(1)
 {
-   Items = 0;
-   Next = 0;
-   Workers = 0;
-   MaxPipeDepth = 1;
-   PipeDepth = 0;
 }
                                                                        /*}}}*/
 // Queue::~Queue - Destructor                                          /*{{{*/
@@ -625,20 +894,34 @@ pkgAcquire::Queue::~Queue()
 /* */
 bool pkgAcquire::Queue::Enqueue(ItemDesc &Item)
 {
+   QItem **OptimalI = &Items;
    QItem **I = &Items;
    // move to the end of the queue and check for duplicates here
-   for (; *I != 0; I = &(*I)->Next)
-      if (Item.URI == (*I)->URI) 
+   for (; *I != 0; ) {
+      if (Item.URI == (*I)->URI)
       {
-        Item.Owner->Status = Item::StatDone;
+        if (_config->FindB("Debug::pkgAcquire::Worker",false) == true)
+           std::cerr << " @ Queue: Action combined for " << Item.URI << " and " << (*I)->URI << std::endl;
+        (*I)->Owners.push_back(Item.Owner);
+        Item.Owner->Status = (*I)->Owner->Status;
         return false;
       }
+      // Determine the optimal position to insert: before anything with a
+      // higher priority.
+      int priority = (*I)->GetPriority();
+
+      I = &(*I)->Next;
+      if (priority >= Item.Owner->Priority()) {
+        OptimalI = I;
+      }
+   }
+
 
    // Create a new item
    QItem *Itm = new QItem;
    *Itm = Item;
-   Itm->Next = 0;
-   *I = Itm;
+   Itm->Next = *OptimalI;
+   *OptimalI = Itm;
    
    Item.Owner->QueueCounter++;   
    if (Items->Next == 0)
@@ -653,13 +936,13 @@ bool pkgAcquire::Queue::Dequeue(Item *Owner)
 {
    if (Owner->Status == pkgAcquire::Item::StatFetching)
       return _error->Error("Tried to dequeue a fetching object");
-       
+
    bool Res = false;
-   
+
    QItem **I = &Items;
    for (; *I != 0;)
    {
-      if ((*I)->Owner == Owner)
+      if (Owner == (*I)->Owner)
       {
         QItem *Jnk= *I;
         *I = (*I)->Next;
@@ -670,7 +953,7 @@ bool pkgAcquire::Queue::Dequeue(Item *Owner)
       else
         I = &(*I)->Next;
    }
-   
+
    return Res;
 }
                                                                        /*}}}*/
@@ -683,10 +966,20 @@ bool pkgAcquire::Queue::Startup()
    if (Workers == 0)
    {
       URI U(Name);
-      pkgAcquire::MethodConfig *Cnf = Owner->GetConfig(U.Access);
-      if (Cnf == 0)
+      pkgAcquire::MethodConfig * const Cnf = Owner->GetConfig(U.Access);
+      if (unlikely(Cnf == nullptr))
         return false;
-      
+
+      // now-running twin of the pkgAcquire::Enqueue call
+      for (QItem *I = Items; I != 0; )
+      {
+        auto const INext = I->Next;
+        for (auto &&O: I->Owners)
+           CheckForBadItemAndFailIt(O, Cnf, Owner->Log);
+        // if an item failed, it will be auto-dequeued invalidation our I here
+        I = INext;
+      }
+
       Workers = new Worker(this,Cnf,Owner->Log);
       Owner->Add(Workers);
       if (Workers->Start() == false)
@@ -747,9 +1040,12 @@ pkgAcquire::Queue::QItem *pkgAcquire::Queue::FindItem(string URI,pkgAcquire::Wor
 bool pkgAcquire::Queue::ItemDone(QItem *Itm)
 {
    PipeDepth--;
-   if (Itm->Owner->Status == pkgAcquire::Item::StatFetching)
-      Itm->Owner->Status = pkgAcquire::Item::StatDone;
-   
+   for (QItem::owner_iterator O = Itm->Owners.begin(); O != Itm->Owners.end(); ++O)
+   {
+      if ((*O)->Status == pkgAcquire::Item::StatFetching)
+        (*O)->Status = pkgAcquire::Item::StatDone;
+   }
+
    if (Itm->Owner->QueueCounter <= 1)
       Owner->Dequeue(Itm->Owner);
    else
@@ -757,7 +1053,7 @@ bool pkgAcquire::Queue::ItemDone(QItem *Itm)
       Dequeue(Itm->Owner);
       Owner->Bump();
    }
-   
+
    return Cycle();
 }
                                                                        /*}}}*/
@@ -772,26 +1068,35 @@ bool pkgAcquire::Queue::Cycle()
 
    if (PipeDepth < 0)
       return _error->Error("Pipedepth failure");
-                          
+
    // Look for a queable item
    QItem *I = Items;
+   int ActivePriority = 0;
    while (PipeDepth < (signed)MaxPipeDepth)
    {
-      for (; I != 0; I = I->Next)
+      for (; I != 0; I = I->Next) {
+        if (I->Owner->Status == pkgAcquire::Item::StatFetching)
+           ActivePriority = std::max(ActivePriority, I->GetPriority());
         if (I->Owner->Status == pkgAcquire::Item::StatIdle)
            break;
-      
+      }
+
       // Nothing to do, queue is idle.
       if (I == 0)
         return true;
-      
+
+      // This item has a lower priority than stuff in the pipeline, pretend
+      // the queue is idle
+      if (I->GetPriority() < ActivePriority)
+        return true;
       I->Worker = Workers;
-      I->Owner->Status = pkgAcquire::Item::StatFetching;
+      for (auto const &O: I->Owners)
+        O->Status = pkgAcquire::Item::StatFetching;
       PipeDepth++;
       if (Workers->QueueItem(I) == false)
         return false;
    }
-   
+
    return true;
 }
                                                                        /*}}}*/
@@ -803,10 +1108,107 @@ void pkgAcquire::Queue::Bump()
    Cycle();
 }
                                                                        /*}}}*/
+HashStringList pkgAcquire::Queue::QItem::GetExpectedHashes() const     /*{{{*/
+{
+   /* each Item can have multiple owners and each owner might have different
+      hashes, even if that is unlikely in practice and if so at least some
+      owners will later fail. There is one situation through which is not a
+      failure and still needs this handling: Two owners who expect the same
+      file, but one owner only knows the SHA1 while the other only knows SHA256. */
+   HashStringList superhsl;
+   for (pkgAcquire::Queue::QItem::owner_iterator O = Owners.begin(); O != Owners.end(); ++O)
+   {
+      HashStringList const hsl = (*O)->GetExpectedHashes();
+      if (hsl.usable() == false)
+        continue;
+      if (superhsl.usable() == false)
+        superhsl = hsl;
+      else
+      {
+        // we merge both lists - if we find disagreement send no hashes
+        HashStringList::const_iterator hs = hsl.begin();
+        for (; hs != hsl.end(); ++hs)
+           if (superhsl.push_back(*hs) == false)
+              break;
+        if (hs != hsl.end())
+        {
+           superhsl.clear();
+           break;
+        }
+      }
+   }
+   return superhsl;
+}
+                                                                       /*}}}*/
+APT_PURE unsigned long long pkgAcquire::Queue::QItem::GetMaximumSize() const   /*{{{*/
+{
+   unsigned long long Maximum = std::numeric_limits<unsigned long long>::max();
+   for (auto const &O: Owners)
+   {
+      if (O->FileSize == 0)
+        continue;
+      Maximum = std::min(Maximum, O->FileSize);
+   }
+   if (Maximum == std::numeric_limits<unsigned long long>::max())
+      return 0;
+   return Maximum;
+}
+                                                                       /*}}}*/
+APT_PURE int pkgAcquire::Queue::QItem::GetPriority() const     /*{{{*/
+{
+   int Priority = 0;
+   for (auto const &O: Owners)
+      Priority = std::max(Priority, O->Priority());
+
+   return Priority;
+}
+                                                                       /*}}}*/
+void pkgAcquire::Queue::QItem::SyncDestinationFiles() const            /*{{{*/
+{
+   /* ensure that the first owner has the best partial file of all and
+      the rest have (potentially dangling) symlinks to it so that
+      everything (like progress reporting) finds it easily */
+   std::string superfile = Owner->DestFile;
+   off_t supersize = 0;
+   for (pkgAcquire::Queue::QItem::owner_iterator O = Owners.begin(); O != Owners.end(); ++O)
+   {
+      if ((*O)->DestFile == superfile)
+        continue;
+      struct stat file;
+      if (lstat((*O)->DestFile.c_str(),&file) == 0)
+      {
+        if ((file.st_mode & S_IFREG) == 0)
+           RemoveFile("SyncDestinationFiles", (*O)->DestFile);
+        else if (supersize < file.st_size)
+        {
+           supersize = file.st_size;
+           RemoveFile("SyncDestinationFiles", superfile);
+           rename((*O)->DestFile.c_str(), superfile.c_str());
+        }
+        else
+           RemoveFile("SyncDestinationFiles", (*O)->DestFile);
+        if (symlink(superfile.c_str(), (*O)->DestFile.c_str()) != 0)
+        {
+           ; // not a problem per-se and no real alternative
+        }
+      }
+   }
+}
+                                                                       /*}}}*/
+std::string pkgAcquire::Queue::QItem::Custom600Headers() const         /*{{{*/
+{
+   /* The others are relatively easy to merge, but this one?
+      Lets not merge and see how far we can run with it…
+      Likely, nobody will ever notice as all the items will
+      be of the same class and hence generate the same headers. */
+   return Owner->Custom600Headers();
+}
+                                                                       /*}}}*/
+
 // AcquireStatus::pkgAcquireStatus - Constructor                       /*{{{*/
 // ---------------------------------------------------------------------
 /* */
-pkgAcquireStatus::pkgAcquireStatus() : d(NULL), Update(true), MorePulses(false)
+pkgAcquireStatus::pkgAcquireStatus() : d(NULL), Percent(-1), Update(true), MorePulses(false)
 {
    Start();
 }
@@ -822,11 +1224,11 @@ bool pkgAcquireStatus::Pulse(pkgAcquire *Owner)
    CurrentBytes = 0;
    TotalItems = 0;
    CurrentItems = 0;
-   
+
    // Compute the total number of bytes to fetch
    unsigned int Unknown = 0;
    unsigned int Count = 0;
-   bool UnfetchedReleaseFiles = false;
+   bool ExpectAdditionalItems = false;
    for (pkgAcquire::ItemCIterator I = Owner->ItemsBegin(); 
         I != Owner->ItemsEnd();
        ++I, ++Count)
@@ -834,17 +1236,10 @@ bool pkgAcquireStatus::Pulse(pkgAcquire *Owner)
       TotalItems++;
       if ((*I)->Status == pkgAcquire::Item::StatDone)
         ++CurrentItems;
-      
-      // Totally ignore local items
-      if ((*I)->Local == true)
-        continue;
 
-      // see if the method tells us to expect more
-      TotalItems += (*I)->ExpectedAdditionalItems;
-
-      // check if there are unfetched Release files
-      if ((*I)->Complete == false && (*I)->ExpectedAdditionalItems > 0)
-         UnfetchedReleaseFiles = true;
+      // do we expect to acquire more files than we know of yet?
+      if ((*I)->ExpectedAdditionalItems > 0)
+         ExpectAdditionalItems = true;
 
       TotalBytes += (*I)->FileSize;
       if ((*I)->Complete == true)
@@ -852,7 +1247,7 @@ bool pkgAcquireStatus::Pulse(pkgAcquire *Owner)
       if ((*I)->FileSize == 0 && (*I)->Complete == false)
         ++Unknown;
    }
-   
+
    // Compute the current completion
    unsigned long long ResumeSize = 0;
    for (pkgAcquire::Worker *I = Owner->WorkersBegin(); I != 0;
@@ -862,9 +1257,9 @@ bool pkgAcquireStatus::Pulse(pkgAcquire *Owner)
       {
         CurrentBytes += I->CurrentSize;
         ResumeSize += I->ResumePoint;
-        
+
         // Files with unknown size always have 100% completion
-        if (I->CurrentItem->Owner->FileSize == 0 && 
+        if (I->CurrentItem->Owner->FileSize == 0 &&
             I->CurrentItem->Owner->Complete == false)
            TotalBytes += I->CurrentSize;
       }
@@ -880,12 +1275,6 @@ bool pkgAcquireStatus::Pulse(pkgAcquire *Owner)
    if (CurrentBytes > TotalBytes)
       CurrentBytes = TotalBytes;
 
-   // debug
-   if (_config->FindB("Debug::acquire::progress", false) == true)
-      std::clog << " Bytes: " 
-                << SizeToStr(CurrentBytes) << " / " << SizeToStr(TotalBytes) 
-                << std::endl;
-   
    // Compute the CPS
    struct timeval NewTime;
    gettimeofday(&NewTime,0);
@@ -905,14 +1294,33 @@ bool pkgAcquireStatus::Pulse(pkgAcquire *Owner)
       Time = NewTime;
    }
 
+   double const OldPercent = Percent;
    // calculate the percentage, if we have too little data assume 1%
-   if (TotalBytes > 0 && UnfetchedReleaseFiles)
+   if (ExpectAdditionalItems)
       Percent = 0;
-   else 
+   else
       // use both files and bytes because bytes can be unreliable
-      Percent = (0.8 * (CurrentBytes/float(TotalBytes)*100.0) + 
+      Percent = (0.8 * (CurrentBytes/float(TotalBytes)*100.0) +
                  0.2 * (CurrentItems/float(TotalItems)*100.0));
 
+   // debug
+   if (_config->FindB("Debug::acquire::progress", false) == true)
+   {
+      std::clog
+         << "["
+         << std::setw(5) << std::setprecision(4) << std::showpoint << Percent 
+         << "]"
+         << " Bytes: "
+         << SizeToStr(CurrentBytes) << " / " << SizeToStr(TotalBytes)
+         << " # Files: "
+         << CurrentItems << " / " << TotalItems
+         << std::endl;
+   }
+
+   double const DiffPercent = Percent - OldPercent;
+   if (DiffPercent < 0.001 && _config->FindB("Acquire::Progress::Diffpercent", false) == true)
+      return true;
+
    int fd = _config->FindI("APT::Status-Fd",-1);
    if(fd > 0) 
    {
@@ -929,15 +1337,14 @@ bool pkgAcquireStatus::Pulse(pkgAcquire *Owner)
         snprintf(msg,sizeof(msg), _("Retrieving file %li of %li (%s remaining)"), i, TotalItems, TimeToStr(ETA).c_str());
       else
         snprintf(msg,sizeof(msg), _("Retrieving file %li of %li"), i, TotalItems);
-        
-      // build the status str
-      status << "dlstatus:" << i
-             << ":"  << std::setprecision(3) << Percent
-             << ":" << msg 
-             << endl;
 
-      std::string const dlstatus = status.str();
-      FileFd::Write(fd, dlstatus.c_str(), dlstatus.size());
+      // build the status str
+      std::ostringstream str;
+      str.imbue(std::locale::classic());
+      str.precision(4);
+      str << "dlstatus" << ':' << std::fixed << i << ':' << Percent << ':' << msg << '\n';
+      auto const dlstatus = str.str();
+      FileFd::Write(fd, dlstatus.data(), dlstatus.size());
    }
 
    return true;
@@ -989,3 +1396,16 @@ void pkgAcquireStatus::Fetched(unsigned long long Size,unsigned long long Resume
    FetchedBytes += Size - Resume;
 }
                                                                        /*}}}*/
+
+pkgAcquire::UriIterator::UriIterator(pkgAcquire::Queue *Q) : d(NULL), CurQ(Q), CurItem(0)
+{
+   while (CurItem == 0 && CurQ != 0)
+   {
+      CurItem = CurQ->Items;
+      CurQ = CurQ->Next;
+   }
+}
+
+APT_CONST pkgAcquire::UriIterator::~UriIterator() {}
+APT_CONST pkgAcquire::MethodConfig::~MethodConfig() {}
+APT_CONST pkgAcquireStatus::~pkgAcquireStatus() {}