require methods to request AuxRequest capability at startup

Allowing a method to request work from other methods is a powerful
capability which could be misused or exploited, so to slightly limited
the surface let method opt-in into this capability on startup.

6 files changed, 106 insertions, 56 deletions

diff --git a/apt-pkg/acquire-method.cc b/apt-pkg/acquire-method.cc
index 4e034b402..8934d87a0 100644
--- a/apt-pkg/acquire-method.cc
+++ b/apt-pkg/acquire-method.cc
@@ -76,6 +76,9 @@ pkgAcqMethod::pkgAcqMethod(const char *Ver,unsigned long Flags)
    if ((Flags & Removable) == Removable)
       try_emplace(fields, "Removable", "true");
 
+   if ((Flags & AuxRequests) == AuxRequests)
+      try_emplace(fields, "AuxRequests", "true");
+
    SendMessage("100 Capabilities", std::move(fields));
 
    SetNonBlock(STDIN_FILENO,true);
diff --git a/apt-pkg/acquire-method.h b/apt-pkg/acquire-method.h
index fa22085b9..664b95c18 100644
--- a/apt-pkg/acquire-method.h
+++ b/apt-pkg/acquire-method.h
@@ -108,10 +108,16 @@ class pkgAcqMethod
    void PrintStatus(char const * const header, const char* Format, va_list &args) const;
 
    public:
-   enum CnfFlags {SingleInstance = (1<<0),
-                  Pipeline = (1<<1), SendConfig = (1<<2),
-                  LocalOnly = (1<<3), NeedsCleanup = (1<<4), 
-                  Removable = (1<<5)};
+   enum CnfFlags
+   {
+      SingleInstance = (1 << 0),
+      Pipeline = (1 << 1),
+      SendConfig = (1 << 2),
+      LocalOnly = (1 << 3),
+      NeedsCleanup = (1 << 4),
+      Removable = (1 << 5),
+      AuxRequests = (1 << 6)
+   };
 
    void Log(const char *Format,...);
    void Status(const char *Format,...);
diff --git a/apt-pkg/acquire-worker.cc b/apt-pkg/acquire-worker.cc
index 016aebdcd..6cbf8b7aa 100644
--- a/apt-pkg/acquire-worker.cc
+++ b/apt-pkg/acquire-worker.cc
@@ -508,6 +508,26 @@ bool pkgAcquire::Worker::RunMessages()
 	       _error->Error("Method gave invalid Aux Request message");
 	       break;
 	    }
+	    else if (Config->GetAuxRequests() == false)
+	    {
+	       std::vector<Item *> const ItmOwners = Itm->Owners;
+	       Message.append("\nMessage: Method tried to make an Aux Request while not being allowed to do them");
+	       OwnerQ->ItemDone(Itm);
+	       Itm = nullptr;
+	       HandleFailure(ItmOwners, Config, Log, Message, false, false);
+	       ItemDone();
+
+	       std::string Msg = "600 URI Acquire\n";
+	       Msg.reserve(200);
+	       Msg += "URI: " + LookupTag(Message, "Aux-URI", "");
+	       Msg += "\nFilename: /nonexistent/auxrequest.blocked";
+	       Msg += "\n\n";
+	       if (Debug == true)
+		  clog << " -> " << Access << ':' << QuoteString(Msg, "\n") << endl;
+	       OutQueue += Msg;
+	       OutReady = true;
+	       break;
+	    }
 
 	    auto maxsizestr = LookupTag(Message, "MaximumSize", "");
 	    unsigned long long const MaxSize = maxsizestr.empty() ? 0 : strtoull(maxsizestr.c_str(), nullptr, 10);
@@ -554,44 +574,7 @@ bool pkgAcquire::Worker::RunMessages()
 		  errAuthErr = std::find(std::begin(reasons), std::end(reasons), failReason) != std::end(reasons);
 	       }
 	    }
-
-	    for (auto const Owner: ItmOwners)
-	    {
-	       std::string NewURI;
-	       if (errTransient == true && Config->LocalOnly == false && Owner->ModifyRetries() != 0)
-	       {
-		  --Owner->ModifyRetries();
-		  Owner->FailMessage(Message);
-		  auto SavedDesc = Owner->GetItemDesc();
-		  if (Log != nullptr)
-		     Log->Fail(SavedDesc);
-		  if (isDoomedItem(Owner) == false)
-		     OwnerQ->Owner->Enqueue(SavedDesc);
-	       }
-	       else if (Owner->PopAlternativeURI(NewURI))
-	       {
-		  Owner->FailMessage(Message);
-		  auto &desc = Owner->GetItemDesc();
-		  if (Log != nullptr)
-		     Log->Fail(desc);
-		  ChangeSiteIsMirrorChange(NewURI, desc, Owner);
-		  desc.URI = NewURI;
-		  if (isDoomedItem(Owner) == false)
-		     OwnerQ->Owner->Enqueue(desc);
-	       }
-	       else
-	       {
-		  if (errAuthErr && Owner->GetExpectedHashes().empty() == false)
-		     Owner->Status = pkgAcquire::Item::StatAuthError;
-		  else if (errTransient)
-		     Owner->Status = pkgAcquire::Item::StatTransientNetworkError;
-		  auto SavedDesc = Owner->GetItemDesc();
-		  if (isDoomedItem(Owner) == false)
-		     Owner->Failed(Message, Config);
-		  if (Log != nullptr)
-		     Log->Fail(SavedDesc);
-	       }
-	    }
+	    HandleFailure(ItmOwners, Config, Log, Message, errTransient, errAuthErr);
 	    ItemDone();
 
 	    break;
@@ -609,6 +592,49 @@ bool pkgAcquire::Worker::RunMessages()
    return true;
 }
 									/*}}}*/
+void pkgAcquire::Worker::HandleFailure(std::vector<pkgAcquire::Item *> const &ItmOwners, /*{{{*/
+				       pkgAcquire::MethodConfig *const Config, pkgAcquireStatus *const Log,
+				       std::string const &Message, bool const errTransient, bool const errAuthErr)
+{
+   for (auto const Owner : ItmOwners)
+   {
+      std::string NewURI;
+      if (errTransient == true && Config->LocalOnly == false && Owner->ModifyRetries() != 0)
+      {
+	 --Owner->ModifyRetries();
+	 Owner->FailMessage(Message);
+	 auto SavedDesc = Owner->GetItemDesc();
+	 if (Log != nullptr)
+	    Log->Fail(SavedDesc);
+	 if (isDoomedItem(Owner) == false)
+	    OwnerQ->Owner->Enqueue(SavedDesc);
+      }
+      else if (Owner->PopAlternativeURI(NewURI))
+      {
+	 Owner->FailMessage(Message);
+	 auto &desc = Owner->GetItemDesc();
+	 if (Log != nullptr)
+	    Log->Fail(desc);
+	 ChangeSiteIsMirrorChange(NewURI, desc, Owner);
+	 desc.URI = NewURI;
+	 if (isDoomedItem(Owner) == false)
+	    OwnerQ->Owner->Enqueue(desc);
+      }
+      else
+      {
+	 if (errAuthErr && Owner->GetExpectedHashes().empty() == false)
+	    Owner->Status = pkgAcquire::Item::StatAuthError;
+	 else if (errTransient)
+	    Owner->Status = pkgAcquire::Item::StatTransientNetworkError;
+	 auto SavedDesc = Owner->GetItemDesc();
+	 if (isDoomedItem(Owner) == false)
+	    Owner->Failed(Message, Config);
+	 if (Log != nullptr)
+	    Log->Fail(SavedDesc);
+      }
+   }
+}
+									/*}}}*/
 // Worker::Capabilities - 100 Capabilities handler			/*{{{*/
 // ---------------------------------------------------------------------
 /* This parses the capabilities message and dumps it into the configuration
@@ -625,18 +651,13 @@ bool pkgAcquire::Worker::Capabilities(string Message)
    Config->LocalOnly = StringToBool(LookupTag(Message,"Local-Only"),false);
    Config->NeedsCleanup = StringToBool(LookupTag(Message,"Needs-Cleanup"),false);
    Config->Removable = StringToBool(LookupTag(Message,"Removable"),false);
+   Config->SetAuxRequests(StringToBool(LookupTag(Message, "AuxRequests"), false));
 
    // Some debug text
    if (Debug == true)
    {
       clog << "Configured access method " << Config->Access << endl;
-      clog << "Version:" << Config->Version <<
-	      " SingleInstance:" << Config->SingleInstance <<
-	      " Pipeline:" << Config->Pipeline <<
-	      " SendConfig:" << Config->SendConfig <<
-	      " LocalOnly: " << Config->LocalOnly <<
-	      " NeedsCleanup: " << Config->NeedsCleanup <<
-	      " Removable: " << Config->Removable << endl;
+      clog << "Version:" << Config->Version << " SingleInstance:" << Config->SingleInstance << " Pipeline:" << Config->Pipeline << " SendConfig:" << Config->SendConfig << " LocalOnly: " << Config->LocalOnly << " NeedsCleanup: " << Config->NeedsCleanup << " Removable: " << Config->Removable << " AuxRequests: " << Config->GetAuxRequests() << endl;
    }
 
    return true;
diff --git a/apt-pkg/acquire-worker.h b/apt-pkg/acquire-worker.h
index 3c5c1cef6..f04db2b3c 100644
--- a/apt-pkg/acquire-worker.h
+++ b/apt-pkg/acquire-worker.h
@@ -329,6 +329,9 @@ class pkgAcquire::Worker : public WeakPointable
 
 private:
    APT_HIDDEN void PrepareFiles(char const * const caller, pkgAcquire::Queue::QItem const * const Itm);
+   APT_HIDDEN void HandleFailure(std::vector<pkgAcquire::Item *> const &ItmOwners,
+				 pkgAcquire::MethodConfig *const Config, pkgAcquireStatus *const Log,
+				 std::string const &Message, bool const errTransient, bool const errAuthErr);
 };
 
 /** @} */
diff --git a/apt-pkg/acquire.cc b/apt-pkg/acquire.cc
index 5fa456ce3..b25a4434a 100644
--- a/apt-pkg/acquire.cc
+++ b/apt-pkg/acquire.cc
@@ -855,12 +855,25 @@ pkgAcquire::UriIterator pkgAcquire::UriEnd()
 }
 									/*}}}*/
 // Acquire::MethodConfig::MethodConfig - Constructor			/*{{{*/
-// ---------------------------------------------------------------------
-/* */
-pkgAcquire::MethodConfig::MethodConfig() : d(NULL), Next(0), SingleInstance(false),
-   Pipeline(false), SendConfig(false), LocalOnly(false), NeedsCleanup(false),
-   Removable(false)
+class pkgAcquire::MethodConfig::Private
+{
+   public:
+   bool AuxRequests = false;
+};
+pkgAcquire::MethodConfig::MethodConfig() : d(new Private()), Next(0), SingleInstance(false),
+					   Pipeline(false), SendConfig(false), LocalOnly(false), NeedsCleanup(false),
+					   Removable(false)
+{
+}
+									/*}}}*/
+bool pkgAcquire::MethodConfig::GetAuxRequests() const /*{{{*/
+{
+   return d->AuxRequests;
+}
+									/*}}}*/
+void pkgAcquire::MethodConfig::SetAuxRequests(bool const value) /*{{{*/
 {
+   d->AuxRequests = value;
 }
 									/*}}}*/
 // Queue::Queue - Constructor						/*{{{*/
diff --git a/apt-pkg/acquire.h b/apt-pkg/acquire.h
index e58aeef65..1cf4da5bf 100644
--- a/apt-pkg/acquire.h
+++ b/apt-pkg/acquire.h
@@ -636,9 +636,10 @@ class pkgAcquire::UriIterator
 /** \brief Information about the properties of a single acquire method.	{{{*/
 struct pkgAcquire::MethodConfig
 {
+   class Private;
    /** \brief dpointer placeholder (for later in case we need it) */
-   void * const d;
-   
+   Private *const d;
+
    /** \brief The next link on the acquire method list.
     *
     *  \todo Why not an STL container?
@@ -688,6 +689,9 @@ struct pkgAcquire::MethodConfig
     */
    MethodConfig();
 
+   APT_HIDDEN bool GetAuxRequests() const;
+   APT_HIDDEN void SetAuxRequests(bool const value);
+
    virtual ~MethodConfig();
 };
 									/*}}}*/