rework hashsum verification in the acquire system

Having every item having its own code to verify the file(s) it handles
is an errorprune process and easy to break, especially if items move
through various stages (download, uncompress, patching, …). With a giant
rework we centralize (most of) the verification to have a better
enforcement rate and (hopefully) less chance for bugs, but it breaks the
ABI bigtime in exchange – and as we break it anyway, it is broken even
harder.

It shouldn't effect most frontends as they don't deal with the acquire
system at all or implement their own items, but some do and will need to
be patched (might be an opportunity to use apt on-board material).

The theory is simple: Items implement methods to decide if hashes need to
be checked (in this stage) and to return the expected hashes for this
item (in this stage). The verification itself is done in worker message
passing which has the benefit that a hashsum error is now a proper error
for the acquire system rather than a Done() which is later revised to a
Failed().

1 files changed, 286 insertions, 391 deletions

diff --git a/apt-pkg/acquire-item.h b/apt-pkg/acquire-item.h
index 07c86f31b..97d5ea1dd 100644
--- a/apt-pkg/acquire-item.h
+++ b/apt-pkg/acquire-item.h
@@ -6,15 +6,15 @@
    Acquire Item - Item to acquire
 
    When an item is instantiated it will add it self to the local list in
-   the Owner Acquire class. Derived classes will then call QueueURI to 
-   register all the URI's they wish to fetch at the initial moment.   
-   
+   the Owner Acquire class. Derived classes will then call QueueURI to
+   register all the URI's they wish to fetch at the initial moment.
+
    Three item classes are provided to provide functionality for
    downloading of Index, Translation and Packages files.
-   
+
    A Archive class is provided for downloading .deb files. It does Hash
    checking and source location as well as a retry algorithm.
-   
+
    ##################################################################### */
 									/*}}}*/
 #ifndef PKGLIB_ACQUIRE_ITEM_H
@@ -49,7 +49,48 @@ class pkgSourceList;
 class IndexTarget;
 class pkgAcqMetaBase;
 
-/** \brief Represents the process by which a pkgAcquire object should	{{{
+class APT_HIDDEN IndexTarget						/*{{{*/
+/** \brief Information about an index file. */
+{
+   public:
+   /** \brief A URI from which the index file can be downloaded. */
+   std::string const URI;
+
+   /** \brief A description of the index file. */
+   std::string const Description;
+
+   /** \brief A shorter description of the index file. */
+   std::string const ShortDesc;
+
+   /** \brief The key by which this index file should be
+    *  looked up within the meta signature file.
+    */
+   std::string const MetaKey;
+
+   virtual bool IsOptional() const {
+      return false;
+   }
+
+   IndexTarget(std::string const &MetaKey, std::string const &ShortDesc,
+	 std::string const &LongDesc, std::string const &URI) :
+      URI(URI), Description(LongDesc), ShortDesc(ShortDesc), MetaKey(MetaKey) {}
+};
+									/*}}}*/
+class APT_HIDDEN OptionalIndexTarget : public IndexTarget		/*{{{*/
+/** \brief Information about an optional index file. */
+{
+   public:
+   virtual bool IsOptional() const {
+      return true;
+   }
+
+   OptionalIndexTarget(std::string const &MetaKey, std::string const &ShortDesc,
+	 std::string const &LongDesc, std::string const &URI) :
+      IndexTarget(MetaKey, ShortDesc, LongDesc, URI) {}
+};
+									/*}}}*/
+class pkgAcquire::Item : public WeakPointable				/*{{{*/
+/** \brief Represents the process by which a pkgAcquire object should
  *  retrieve a file or a collection of files.
  *
  *  By convention, Item subclasses should insert themselves into the
@@ -61,46 +102,7 @@ class pkgAcqMetaBase;
  *
  *  \see pkgAcquire
  */
-class pkgAcquire::Item : public WeakPointable
-{  
-   friend class pkgAcqMetaBase;
-
-   void *d;
-
-   protected:
-   
-   /** \brief The acquire object with which this item is associated. */
-   pkgAcquire *Owner;
-
-   /** \brief Insert this item into its owner's queue.
-    *
-    *  The method is designed to check if the request would end
-    *  in an IMSHit and if it determines that it would, it isn't
-    *  queueing the Item and instead sets it to completion instantly.
-    *
-    *  \param Item Metadata about this item (its URI and
-    *  description).
-    *  \return true if the item was inserted, false if IMSHit was detected
-    */
-   virtual bool QueueURI(ItemDesc &Item);
-
-   /** \brief Remove this item from its owner's queue. */
-   void Dequeue();
-
-   /** \brief Rename a file without modifying its timestamp.
-    *
-    *  Many item methods call this as their final action.
-    *
-    *  \param From The file to be renamed.
-    *
-    *  \param To The new name of \a From.  If \a To exists it will be
-    *  overwritten.
-    */
-   bool Rename(std::string From,std::string To);
-
-   /** \brief Get the full pathname of the final file for the current URI */
-   virtual std::string GetFinalFilename() const;
-
+{
    public:
 
    /** \brief The current status of this item. */
@@ -125,7 +127,7 @@ class pkgAcquire::Item : public WeakPointable
 	*/
        StatAuthError,
 
-       /** \brief The item was could not be downloaded because of 
+       /** \brief The item was could not be downloaded because of
 	*  a transient network error (e.g. network down)
 	*/
        StatTransientNetworkError,
@@ -153,11 +155,11 @@ class pkgAcquire::Item : public WeakPointable
    std::string ActiveSubprocess;
 
    /** \brief A client-supplied unique identifier.
-    * 
+    *
     *  This field is initalized to 0; it is meant to be filled in by
     *  clients that wish to use it to uniquely identify items.
     *
-    *  \todo it's unused in apt itself
+    *  APT progress reporting will store an ID there as shown in "Get:42 …"
     */
    unsigned long ID;
 
@@ -173,6 +175,7 @@ class pkgAcquire::Item : public WeakPointable
     *  download progress indicator's overall statistics.
     */
    bool Local;
+
    std::string UsedMirror;
 
    /** \brief The number of fetch queues into which this item has been
@@ -185,9 +188,6 @@ class pkgAcquire::Item : public WeakPointable
     */
    unsigned int QueueCounter;
 
-   /** \brief TransactionManager */
-   pkgAcqMetaBase *TransactionManager;
-
    /** \brief The number of additional fetch items that are expected
     *  once this item is done.
     *
@@ -197,15 +197,12 @@ class pkgAcquire::Item : public WeakPointable
     *  progress.
     */
    unsigned int ExpectedAdditionalItems;
-   
+
    /** \brief The name of the file into which the retrieved object
     *  will be written.
     */
    std::string DestFile;
 
-   /** \brief storge name until a transaction is finished */
-   std::string PartialFile;
-
    /** \brief Invoked by the acquire worker when the object couldn't
     *  be fetched.
     *
@@ -219,7 +216,7 @@ class pkgAcquire::Item : public WeakPointable
     *
     *  \sa pkgAcqMethod
     */
-   virtual void Failed(std::string Message,pkgAcquire::MethodConfig *Cnf);
+   virtual void Failed(std::string const &Message,pkgAcquire::MethodConfig const * const Cnf);
 
    /** \brief Invoked by the acquire worker when the object was
     *  fetched successfully.
@@ -234,25 +231,24 @@ class pkgAcquire::Item : public WeakPointable
     *
     *  \param Message Data from the acquire method.  Use LookupTag()
     *  to parse it.
-    *  \param Size The size of the object that was fetched.
     *  \param Hashes The HashSums of the object that was fetched.
     *  \param Cnf The method via which the object was fetched.
     *
     *  \sa pkgAcqMethod
     */
-   virtual void Done(std::string Message, unsigned long long Size, HashStringList const &Hashes,
-		     pkgAcquire::MethodConfig *Cnf);
+   virtual void Done(std::string const &Message, HashStringList const &Hashes,
+		     pkgAcquire::MethodConfig const * const Cnf);
 
    /** \brief Invoked when the worker starts to fetch this object.
     *
     *  \param Message RFC822-formatted data from the worker process.
     *  Use LookupTag() to parse it.
     *
-    *  \param Size The size of the object being fetched.
+    *  \param Hashes The expected hashes of the object being fetched.
     *
     *  \sa pkgAcqMethod
     */
-   virtual void Start(std::string Message,unsigned long long Size);
+   virtual void Start(std::string const &Message, unsigned long long const Size);
 
    /** \brief Custom headers to be sent to the fetch process.
     *
@@ -262,61 +258,55 @@ class pkgAcquire::Item : public WeakPointable
     *  line, so they should (if nonempty) have a leading newline and
     *  no trailing newline.
     */
-#if APT_PKG_ABI >= 413
-   virtual std::string Custom600Headers() const {return std::string();};
-#else
-   virtual std::string Custom600Headers() {return std::string();};
-#endif
+   virtual std::string Custom600Headers() const;
 
    /** \brief A "descriptive" URI-like string.
     *
     *  \return a URI that should be used to describe what is being fetched.
     */
-   virtual std::string DescURI() = 0;
+   virtual std::string DescURI() const = 0;
    /** \brief Short item description.
     *
     *  \return a brief description of the object being fetched.
     */
-   virtual std::string ShortDesc() {return DescURI();}
+   virtual std::string ShortDesc() const;
 
    /** \brief Invoked by the worker when the download is completely done. */
-   virtual void Finished() {};
-   
-   /** \brief HashSums
+   virtual void Finished();
+
+   /** \return HashSums the DestFile is supposed to have in this stage */
+   virtual HashStringList GetExpectedHashes() const = 0;
+   /** \return the 'best' hash for display proposes like --print-uris */
+   std::string HashSum() const;
+
+   /** \return if having no hashes is a hard failure or not
     *
-    *  \return the HashSums of this object, if applicable; otherwise, an
-    *  empty list.
+    * Idealy this is always \b true for every subclass, but thanks to
+    * historical grow we don't have hashes for all files in all cases
+    * in all steps, so it is slightly more complicated than it should be.
     */
-   HashStringList HashSums() const {return ExpectedHashes;};
-   std::string HashSum() const {HashStringList const hashes = HashSums(); HashString const * const hs = hashes.find(NULL); return hs != NULL ? hs->toStr() : ""; };
+   virtual bool HashesRequired() const { return true; }
 
    /** \return the acquire process with which this item is associated. */
-   pkgAcquire *GetOwner() const {return Owner;};
-#if APT_PKG_ABI < 413
-   pkgAcquire *GetOwner() {return Owner;};
-#endif
+   pkgAcquire *GetOwner() const;
 
    /** \return \b true if this object is being fetched from a trusted source. */
-#if APT_PKG_ABI >= 413
-   virtual bool IsTrusted() const {return false;};
-#else
-   virtual bool IsTrusted() {return false;};
-#endif
-   
+   virtual bool IsTrusted() const;
+
    /** \brief Report mirror problem
-    * 
+    *
     *  This allows reporting mirror failures back to a centralized
     *  server. The apt-report-mirror-failure script is called for this
-    * 
+    *
     *  \param FailCode A short failure string that is send
     */
-   void ReportMirrorFailure(std::string FailCode);
+   void ReportMirrorFailure(std::string const &FailCode);
 
    /** \brief Set the name of the current active subprocess
     *
     *  See also #ActiveSubprocess
     */
-   void SetActiveSubprocess(const std::string &subprocess);
+   void SetActiveSubprocess(std::string const &subprocess);
 
    /** \brief Initialize an item.
     *
@@ -325,11 +315,8 @@ class pkgAcquire::Item : public WeakPointable
     *  manually invoke QueueURI() to do so).
     *
     *  \param Owner The new owner of this item.
-    *  \param ExpectedHashes of the file represented by this item
     */
-   Item(pkgAcquire *Owner,
-        HashStringList const &ExpectedHashes=HashStringList(),
-        pkgAcqMetaBase *TransactionManager=NULL);
+   Item(pkgAcquire * const Owner);
 
    /** \brief Remove this item from its owner's queue by invoking
     *  pkgAcquire::Remove.
@@ -337,6 +324,11 @@ class pkgAcquire::Item : public WeakPointable
    virtual ~Item();
 
    protected:
+   /** \brief The acquire object with which this item is associated. */
+   pkgAcquire * const Owner;
+
+   /** \brief The item that is currently being downloaded. */
+   pkgAcquire::ItemDesc Desc;
 
    enum RenameOnErrorState {
       HashSumMismatch,
@@ -354,63 +346,99 @@ class pkgAcquire::Item : public WeakPointable
     */
    bool RenameOnError(RenameOnErrorState const state);
 
+   /** \brief Insert this item into its owner's queue.
+    *
+    *  The method is designed to check if the request would end
+    *  in an IMSHit and if it determines that it would, it isn't
+    *  queueing the Item and instead sets it to completion instantly.
+    *
+    *  \param Item Metadata about this item (its URI and
+    *  description).
+    *  \return true if the item was inserted, false if IMSHit was detected
+    */
+   virtual bool QueueURI(ItemDesc &Item);
+
+   /** \brief Remove this item from its owner's queue. */
+   void Dequeue();
+
+   /** \brief Rename a file without modifying its timestamp.
+    *
+    *  Many item methods call this as their final action.
+    *
+    *  \param From The file to be renamed.
+    *
+    *  \param To The new name of \a From.  If \a To exists it will be
+    *  overwritten. If \a From and \a To are equal nothing happens.
+    */
+   bool Rename(std::string const &From, std::string const &To);
+
+   /** \brief Get the full pathname of the final file for the current URI */
+   virtual std::string GetFinalFilename() const;
+
+   private:
+   void *d;
+
+   friend class pkgAcqMetaBase;
+};
+									/*}}}*/
+class APT_HIDDEN pkgAcqTransactionItem: public pkgAcquire::Item		/*{{{*/
+/** \brief baseclass for the indexes files to manage them all together */
+{
+   protected:
+   IndexTarget const * const Target;
+   HashStringList GetExpectedHashesFor(std::string const MetaKey) const;
+
+   bool QueueURI(pkgAcquire::ItemDesc &Item);
+
+   public:
+   /** \brief storge name until a transaction is finished */
+   std::string PartialFile;
+
+   /** \brief TransactionManager */
+   pkgAcqMetaBase * const TransactionManager;
+
    enum TransactionStates {
       TransactionCommit,
       TransactionAbort,
    };
    virtual bool TransactionState(TransactionStates const state);
 
-   /** \brief The HashSums of the item is supposed to have than done */
-   HashStringList ExpectedHashes;
+   virtual std::string DescURI() const { return Target->URI; }
+   virtual HashStringList GetExpectedHashes() const;
+   virtual std::string GetMetaKey() const;
+   virtual bool HashesRequired() const;
 
-   /** \brief The item that is currently being downloaded. */
-   pkgAcquire::ItemDesc Desc;
-};
-									/*}}}*/
-/** \brief Information about an index patch (aka diff). */		/*{{{*/
-struct APT_HIDDEN DiffInfo {
-   /** The filename of the diff. */
-   std::string file;
 
-   /** The hashes of the diff */
-   HashStringList result_hashes;
-
-   /** The hashes of the file after the diff is applied */
-   HashStringList patch_hashes;
+   pkgAcqTransactionItem(pkgAcquire * const Owner, pkgAcqMetaBase * const TransactionManager, IndexTarget const * const Target);
+   virtual ~pkgAcqTransactionItem();
 
-   /** The size of the file after the diff is applied */
-   unsigned long long result_size;
-
-   /** The size of the diff itself */
-   unsigned long long patch_size;
+   friend class pkgAcqMetaBase;
 };
 									/*}}}*/
-class pkgAcqMetaBase  : public pkgAcquire::Item				/*{{{*/
+class APT_HIDDEN pkgAcqMetaBase : public pkgAcqTransactionItem		/*{{{*/
+/** \brief the manager of a transaction */
 {
    void *d;
 
  protected:
-   std::vector<Item*> Transaction;
+   std::vector<pkgAcqTransactionItem*> Transaction;
 
+   IndexTarget const DataTarget;
+ public:
    /** \brief A package-system-specific parser for the meta-index file. */
    indexRecords *MetaIndexParser;
    indexRecords *LastMetaIndexParser;
+ protected:
 
    /** \brief The index files which should be looked up in the meta-index
     *  and then downloaded.
     */
-   const std::vector<IndexTarget*>* IndexTargets;
+   const std::vector<IndexTarget*>* const IndexTargets;
 
    /** \brief If \b true, the index's signature is currently being verified.
     */
    bool AuthPass;
 
-   /** \brief The URI of the signature file.  Unlike Desc.URI, this is
-    *  never modified; it is used to determine the file that is being
-    *  downloaded.
-    */
-   std::string RealURI;
-
    /** \brief Starts downloading the individual index files.
     *
     *  \param verify If \b true, only indices whose expected hashsum
@@ -419,7 +447,7 @@ class pkgAcqMetaBase  : public pkgAcquire::Item				/*{{{*/
     *  #StatAuthError if there is a mismatch).  If verify is \b false,
     *  no hashsum checking will be performed.
     */
-   void QueueIndexes(bool verify);
+   void QueueIndexes(bool const verify);
 
    /** \brief Called when a file is finished being retrieved.
     *
@@ -430,16 +458,12 @@ class pkgAcqMetaBase  : public pkgAcquire::Item				/*{{{*/
     *  \param Message The message block received from the fetch
     *  subprocess.
     */
-   bool CheckDownloadDone(pkgAcquire::Item * const I, const std::string &Message, HashStringList const &Hashes) const;
+   bool CheckDownloadDone(pkgAcqTransactionItem * const I, const std::string &Message, HashStringList const &Hashes) const;
 
    /** \brief Queue the downloaded Signature for verification */
-   void QueueForSignatureVerify(pkgAcquire::Item * const I, std::string const &File, std::string const &Signature);
+   void QueueForSignatureVerify(pkgAcqTransactionItem * const I, std::string const &File, std::string const &Signature);
 
-#if APT_PKG_ABI >= 413
    virtual std::string Custom600Headers() const;
-#else
-   virtual std::string Custom600Headers();
-#endif
 
    /** \brief Called when authentication succeeded.
     *
@@ -450,7 +474,7 @@ class pkgAcqMetaBase  : public pkgAcquire::Item				/*{{{*/
     *  \param Message The message block received from the fetch
     *  subprocess.
     */
-   bool CheckAuthDone(std::string Message);
+   bool CheckAuthDone(std::string const &Message);
 
    /** Check if the current item should fail at this point */
    bool CheckStopAuthentication(pkgAcquire::Item * const I, const std::string &Message);
@@ -460,7 +484,7 @@ class pkgAcqMetaBase  : public pkgAcquire::Item				/*{{{*/
     *
     *  \return \b true if no fatal errors were encountered.
     */
-   bool VerifyVendor(std::string Message);
+   bool VerifyVendor(std::string const &Message);
 
    virtual bool TransactionState(TransactionStates const state);
 
@@ -468,33 +492,32 @@ class pkgAcqMetaBase  : public pkgAcquire::Item				/*{{{*/
    // This refers more to the Transaction-Manager than the actual file
    bool IMSHit;
 
-   virtual std::string DescURI() {return RealURI; };
    virtual bool QueueURI(pkgAcquire::ItemDesc &Item);
+   virtual HashStringList GetExpectedHashes() const;
+   virtual bool HashesRequired() const;
 
    // transaction code
-   void Add(Item *I);
+   void Add(pkgAcqTransactionItem * const I);
    void AbortTransaction();
-   bool TransactionHasError() APT_PURE;
+   bool TransactionHasError() const;
    void CommitTransaction();
 
    /** \brief Stage (queue) a copy action when the transaction is committed
     */
-   void TransactionStageCopy(Item *I,
-                             const std::string &From, 
+   void TransactionStageCopy(pkgAcqTransactionItem * const I,
+                             const std::string &From,
                              const std::string &To);
    /** \brief Stage (queue) a removal action when the transaction is committed
     */
-   void TransactionStageRemoval(Item *I, const std::string &FinalFile);
+   void TransactionStageRemoval(pkgAcqTransactionItem * const I, const std::string &FinalFile);
 
    /** \brief Get the full pathname of the final file for the current URI */
    virtual std::string GetFinalFilename() const;
 
-   pkgAcqMetaBase(pkgAcquire *Owner,
-                  const std::vector<IndexTarget*>* IndexTargets,
-                  indexRecords* MetaIndexParser,
-		  std::string const &RealURI,
-                  HashStringList const &ExpectedHashes=HashStringList(),
-                  pkgAcqMetaBase *TransactionManager=NULL);
+   pkgAcqMetaBase(pkgAcquire * const Owner, pkgAcqMetaBase * const TransactionManager,
+		  std::vector<IndexTarget*> const * const IndexTargets,
+		  IndexTarget const &DataTarget,
+		  indexRecords* const MetaIndexParser);
 };
 									/*}}}*/
 /** \brief An item that is responsible for downloading the meta-index	{{{
@@ -512,36 +535,24 @@ class APT_HIDDEN pkgAcqMetaIndex : public pkgAcqMetaBase
    void *d;
 
    protected:
-   std::string URIDesc;
-   std::string ShortDesc;
-
-   /** \brief The URI of the meta-index file for the detached signature */
-   std::string MetaIndexSigURI;
-
-   /** \brief A "URI-style" description of the meta-index file */
-   std::string MetaIndexSigURIDesc;
-
-   /** \brief A brief description of the meta-index file */
-   std::string MetaIndexSigShortDesc;
+   IndexTarget const DetachedSigTarget;
 
    /** \brief delayed constructor */
-   void Init(std::string URIDesc, std::string ShortDesc);
-   
+   void Init(std::string const &URIDesc, std::string const &ShortDesc);
+
    public:
+   virtual std::string DescURI() const;
 
    // Specialized action members
-   virtual void Failed(std::string Message,pkgAcquire::MethodConfig *Cnf);
-   virtual void Done(std::string Message,unsigned long long Size, HashStringList const &Hashes,
-		     pkgAcquire::MethodConfig *Cnf);
+   virtual void Failed(std::string const &Message,pkgAcquire::MethodConfig const * const Cnf);
+   virtual void Done(std::string const &Message, HashStringList const &Hashes,
+		     pkgAcquire::MethodConfig const * const Cnf);
    virtual void Finished();
 
    /** \brief Create a new pkgAcqMetaIndex. */
-   pkgAcqMetaIndex(pkgAcquire *Owner,
-                   pkgAcqMetaBase *TransactionManager,
-		   std::string URI,std::string URIDesc, std::string ShortDesc,
-                   std::string MetaIndexSigURI, std::string MetaIndexSigURIDesc, std::string MetaIndexSigShortDesc,
-		   const std::vector<IndexTarget*>* IndexTargets,
-		   indexRecords* MetaIndexParser);
+   pkgAcqMetaIndex(pkgAcquire * const Owner, pkgAcqMetaBase * const TransactionManager,
+		   IndexTarget const &DataTarget, IndexTarget const &DetachedSigTarget,
+		   const std::vector<IndexTarget*>* const IndexTargets, indexRecords * const MetaIndexParser);
 
    friend class pkgAcqMetaSig;
 };
@@ -554,7 +565,7 @@ class APT_HIDDEN pkgAcqMetaIndex : public pkgAcqMetaBase
  *
  *  \sa pkgAcqMetaIndex
  */
-class APT_HIDDEN pkgAcqMetaSig : public pkgAcquire::Item
+class APT_HIDDEN pkgAcqMetaSig : public pkgAcqTransactionItem
 {
    void *d;
 
@@ -565,29 +576,20 @@ class APT_HIDDEN pkgAcqMetaSig : public pkgAcquire::Item
 
    protected:
 
-   /** \brief Long URI description used in the acquire system */
-   std::string URIDesc;
-
-   /** \brief URI used to get the file */
-   std::string RealURI;
-
    /** \brief Get the full pathname of the final file for the current URI */
    virtual std::string GetFinalFilename() const;
 
    public:
-   virtual std::string DescURI() {return RealURI;};
+   virtual bool HashesRequired() const { return false; }
 
    // Specialized action members
-   virtual void Failed(std::string Message,pkgAcquire::MethodConfig *Cnf);
-   virtual void Done(std::string Message,unsigned long long Size,
-                     HashStringList const &Hashes,
-		     pkgAcquire::MethodConfig *Cnf);
+   virtual void Failed(std::string const &Message,pkgAcquire::MethodConfig const * const Cnf);
+   virtual void Done(std::string const &Message, HashStringList const &Hashes,
+		     pkgAcquire::MethodConfig const * const Cnf);
 
    /** \brief Create a new pkgAcqMetaSig. */
-   pkgAcqMetaSig(pkgAcquire *Owner,
-	 pkgAcqMetaBase *TransactionManager,
-	 std::string const &URI,std::string const &URIDesc,
-	 std::string const &ShortDesc, pkgAcqMetaIndex * const MetaIndex);
+   pkgAcqMetaSig(pkgAcquire * const Owner, pkgAcqMetaBase * const TransactionManager, IndexTarget const * const Target,
+	 pkgAcqMetaIndex * const MetaIndex);
    virtual ~pkgAcqMetaSig();
 };
 									/*}}}*/
@@ -596,78 +598,37 @@ class APT_HIDDEN pkgAcqMetaClearSig : public pkgAcqMetaIndex
 {
    void *d;
 
-   /** \brief The URI of the meta-index file for the detached signature */
-   std::string MetaIndexURI;
-
-   /** \brief A "URI-style" description of the meta-index file */
-   std::string MetaIndexURIDesc;
-
-   /** \brief A brief description of the meta-index file */
-   std::string MetaIndexShortDesc;
-
-   /** \brief The URI of the detached meta-signature file if the clearsigned one failed. */
-   std::string MetaSigURI;
-
-   /** \brief A "URI-style" description of the meta-signature file */
-   std::string MetaSigURIDesc;
-
-   /** \brief A brief description of the meta-signature file */
-   std::string MetaSigShortDesc;
+   IndexTarget const ClearsignedTarget;
+   IndexTarget const DetachedDataTarget;
+   IndexTarget const DetachedSigTarget;
 
 public:
-   virtual void Failed(std::string Message,pkgAcquire::MethodConfig *Cnf);
-#if APT_PKG_ABI >= 413
+   virtual void Failed(std::string const &Message,pkgAcquire::MethodConfig const * const Cnf);
    virtual std::string Custom600Headers() const;
-#else
-   virtual std::string Custom600Headers();
-#endif
-   virtual void Done(std::string Message,unsigned long long Size,
-                     HashStringList const &Hashes,
-		     pkgAcquire::MethodConfig *Cnf);
+   virtual void Done(std::string const &Message, HashStringList const &Hashes,
+		     pkgAcquire::MethodConfig const * const Cnf);
 
    /** \brief Create a new pkgAcqMetaClearSig. */
-   pkgAcqMetaClearSig(pkgAcquire *Owner,
-		std::string const &URI, std::string const &URIDesc, std::string const &ShortDesc,
-		std::string const &MetaIndexURI, std::string const &MetaIndexURIDesc, std::string const &MetaIndexShortDesc,
-		std::string const &MetaSigURI, std::string const &MetaSigURIDesc, std::string const &MetaSigShortDesc,
-		const std::vector<IndexTarget*>* IndexTargets,
-		indexRecords* MetaIndexParser);
+   pkgAcqMetaClearSig(pkgAcquire * const Owner,
+		IndexTarget const &ClearsignedTarget,
+		IndexTarget const &DetachedDataTarget,
+		IndexTarget const &DetachedSigTarget,
+		std::vector<IndexTarget*> const * const IndexTargets,
+		indexRecords * const MetaIndexParser);
    virtual ~pkgAcqMetaClearSig();
 };
 									/*}}}*/
-/** \brief Common base class for all classes that deal with fetching 	{{{
-           indexes
- */
-class pkgAcqBaseIndex : public pkgAcquire::Item
+/** \brief Common base class for all classes that deal with fetching indexes	{{{*/
+class APT_HIDDEN pkgAcqBaseIndex : public pkgAcqTransactionItem
 {
    void *d;
 
- protected:
-   /** \brief Pointer to the IndexTarget data
-    */
-   const struct IndexTarget * Target;
-
-   /** \brief Pointer to the indexRecords parser */
-   indexRecords *MetaIndexParser;
-
-   /** \brief The MetaIndex Key */
-   std::string MetaKey;
-
-   /** \brief The URI of the index file to recreate at our end (either
-    *  by downloading it or by applying partial patches).
-    */
-   std::string RealURI;
-
-   bool VerifyHashByMetaKey(HashStringList const &Hashes);
-
+ public:
    /** \brief Get the full pathname of the final file for the current URI */
    virtual std::string GetFinalFilename() const;
 
-   pkgAcqBaseIndex(pkgAcquire *Owner,
-                   pkgAcqMetaBase *TransactionManager,
-                   struct IndexTarget const * const Target,
-                   HashStringList const &ExpectedHashes,
-                   indexRecords *MetaIndexParser);
+   pkgAcqBaseIndex(pkgAcquire * const Owner, pkgAcqMetaBase * const TransactionManager,
+                   IndexTarget const * const Target);
 };
 									/*}}}*/
 /** \brief An item that is responsible for fetching an index file of	{{{
@@ -705,15 +666,12 @@ class APT_HIDDEN pkgAcqDiffIndex : public pkgAcqBaseIndex
    virtual bool TransactionState(TransactionStates const state);
  public:
    // Specialized action members
-   virtual void Failed(std::string Message,pkgAcquire::MethodConfig *Cnf);
-   virtual void Done(std::string Message,unsigned long long Size, HashStringList const &Hashes,
-		     pkgAcquire::MethodConfig *Cnf);
-   virtual std::string DescURI() {return RealURI + "Index";};
-#if APT_PKG_ABI >= 413
+   virtual void Failed(std::string const &Message, pkgAcquire::MethodConfig const * const Cnf);
+   virtual void Done(std::string const &Message, HashStringList const &Hashes,
+		     pkgAcquire::MethodConfig const * const Cnf);
+   virtual std::string DescURI() const {return Target->URI + "Index";};
    virtual std::string Custom600Headers() const;
-#else
-   virtual std::string Custom600Headers();
-#endif
+   virtual std::string GetMetaKey() const;
 
    /** \brief Parse the Index file for a set of Packages diffs.
     *
@@ -725,7 +683,7 @@ class APT_HIDDEN pkgAcqDiffIndex : public pkgAcqBaseIndex
     *  \return \b true if the Index file was successfully parsed, \b
     *  false otherwise.
     */
-   bool ParseDiffIndex(std::string IndexDiffFile);
+   bool ParseDiffIndex(std::string const &IndexDiffFile);
 
    /** \brief Create a new pkgAcqDiffIndex.
     *
@@ -736,18 +694,30 @@ class APT_HIDDEN pkgAcqDiffIndex : public pkgAcqBaseIndex
     *  \param URIDesc A long description of the list file to download.
     *
     *  \param ShortDesc A short description of the list file to download.
-    *
-    *  \param ExpectedHashes The list file's hashsums which are expected.
     */
-   pkgAcqDiffIndex(pkgAcquire *Owner,
-                   pkgAcqMetaBase *TransactionManager,
-                   struct IndexTarget const * const Target,
-                   HashStringList const &ExpectedHashes,
-                   indexRecords *MetaIndexParser);
+   pkgAcqDiffIndex(pkgAcquire * const Owner, pkgAcqMetaBase * const TransactionManager,
+                   IndexTarget const * const Target);
  private:
    APT_HIDDEN void QueueOnIMSHit() const;
 };
 									/*}}}*/
+struct APT_HIDDEN DiffInfo {						/*{{{*/
+   /** The filename of the diff. */
+   std::string file;
+
+   /** The hashes of the diff */
+   HashStringList result_hashes;
+
+   /** The hashes of the file after the diff is applied */
+   HashStringList patch_hashes;
+
+   /** The size of the file after the diff is applied */
+   unsigned long long result_size;
+
+   /** The size of the diff itself */
+   unsigned long long patch_size;
+};
+									/*}}}*/
 /** \brief An item that is responsible for fetching client-merge patches {{{
  *  that need to be applied to a given package index file.
  *
@@ -801,10 +771,12 @@ class APT_HIDDEN pkgAcqIndexMergeDiffs : public pkgAcqBaseIndex
     *  This method will fall back to downloading the whole index file
     *  outright; its arguments are ignored.
     */
-   virtual void Failed(std::string Message,pkgAcquire::MethodConfig *Cnf);
-   virtual void Done(std::string Message,unsigned long long Size, HashStringList const &Hashes,
-	 pkgAcquire::MethodConfig *Cnf);
-   virtual std::string DescURI() {return RealURI + "Index";};
+   virtual void Failed(std::string const &Message,pkgAcquire::MethodConfig const * const Cnf);
+   virtual void Done(std::string const &Message, HashStringList const &Hashes,
+	 pkgAcquire::MethodConfig const * const Cnf);
+   virtual std::string DescURI() const {return Target->URI + "Index";};
+   virtual HashStringList GetExpectedHashes() const;
+   virtual bool HashesRequired() const;
 
    /** \brief Create an index merge-diff item.
     *
@@ -817,22 +789,15 @@ class APT_HIDDEN pkgAcqIndexMergeDiffs : public pkgAcqBaseIndex
     *
     *  \param ShortDesc A brief description of this item.
     *
-    *  \param ExpectedHashes The expected md5sum of the completely
-    *  reconstructed package index file; the index file will be tested
-    *  against this value when it is entirely reconstructed.
-    *
     *  \param patch contains infos about the patch this item is supposed
     *  to download which were read from the index
     *
     *  \param allPatches contains all related items so that each item can
     *  check if it was the last one to complete the download step
     */
-   pkgAcqIndexMergeDiffs(pkgAcquire *Owner,
-                         pkgAcqMetaBase *TransactionManager,
-                         struct IndexTarget const * const Target,
-                         HashStringList const &ExpectedHash,
-                         indexRecords *MetaIndexParser,
-                         DiffInfo const &patch, 
+   pkgAcqIndexMergeDiffs(pkgAcquire * const Owner, pkgAcqMetaBase * const TransactionManager,
+                         IndexTarget const * const Target,
+                         DiffInfo const &patch,
                          std::vector<pkgAcqIndexMergeDiffs*> const * const allPatches);
 };
 									/*}}}*/
@@ -875,7 +840,7 @@ class APT_HIDDEN pkgAcqIndexDiffs : public pkgAcqBaseIndex
     *  \param allDone If \b true, the file was entirely reconstructed,
     *  and its md5sum is verified. 
     */
-   APT_HIDDEN void Finish(bool allDone=false);
+   APT_HIDDEN void Finish(bool const allDone=false);
 
    protected:
 
@@ -905,26 +870,25 @@ class APT_HIDDEN pkgAcqIndexDiffs : public pkgAcqBaseIndex
 
 	 /** \brief The diff is currently being fetched. */
 	 StateFetchDiff,
-	 
-	 /** \brief The diff is currently being uncompressed. */
-	 StateUnzipDiff, // FIXME: No longer used
 
 	 /** \brief The diff is currently being applied. */
 	 StateApplyDiff
    } State;
 
    public:
-   
+
    /** \brief Called when the patch file failed to be downloaded.
     *
     *  This method will fall back to downloading the whole index file
     *  outright; its arguments are ignored.
     */
-   virtual void Failed(std::string Message,pkgAcquire::MethodConfig *Cnf);
+   virtual void Failed(std::string const &Message,pkgAcquire::MethodConfig const * const Cnf);
 
-   virtual void Done(std::string Message,unsigned long long Size, HashStringList const &Hashes,
-		     pkgAcquire::MethodConfig *Cnf);
-   virtual std::string DescURI() {return RealURI + "IndexDiffs";};
+   virtual void Done(std::string const &Message, HashStringList const &Hashes,
+		     pkgAcquire::MethodConfig const * const Cnf);
+   virtual std::string DescURI() const {return Target->URI + "IndexDiffs";};
+   virtual HashStringList GetExpectedHashes() const;
+   virtual bool HashesRequired() const;
 
    /** \brief Create an index diff item.
     *
@@ -940,20 +904,13 @@ class APT_HIDDEN pkgAcqIndexDiffs : public pkgAcqBaseIndex
     *
     *  \param ShortDesc A brief description of this item.
     *
-    *  \param ExpectedHashes The expected hashsums of the completely
-    *  reconstructed package index file; the index file will be tested
-    *  against this value when it is entirely reconstructed.
-    *
     *  \param diffs The remaining diffs from the index of diffs.  They
     *  should be ordered so that each diff appears before any diff
     *  that depends on it.
     */
-   pkgAcqIndexDiffs(pkgAcquire *Owner,
-                    pkgAcqMetaBase *TransactionManager,
-                    struct IndexTarget const * const Target,
-                    HashStringList const &ExpectedHash,
-                    indexRecords *MetaIndexParser,
-		    std::vector<DiffInfo> diffs=std::vector<DiffInfo>());
+   pkgAcqIndexDiffs(pkgAcquire * const Owner, pkgAcqMetaBase * const TransactionManager,
+                    IndexTarget const * const Target,
+		    std::vector<DiffInfo> const &diffs=std::vector<DiffInfo>());
 };
 									/*}}}*/
 /** \brief An acquire item that is responsible for fetching an index	{{{
@@ -981,16 +938,16 @@ class APT_HIDDEN pkgAcqIndex : public pkgAcqBaseIndex
    AllStages Stage;
 
    /** \brief Handle what needs to be done when the download is done */
-   void StageDownloadDone(std::string Message,
+   void StageDownloadDone(std::string const &Message,
                           HashStringList const &Hashes,
-                          pkgAcquire::MethodConfig *Cfg);
+                          pkgAcquire::MethodConfig const * const Cfg);
 
    /** \brief Handle what needs to be done when the decompression/copy is
     *         done 
     */
-   void StageDecompressDone(std::string Message,
+   void StageDecompressDone(std::string const &Message,
                             HashStringList const &Hashes,
-                            pkgAcquire::MethodConfig *Cfg);
+                            pkgAcquire::MethodConfig const * const Cfg);
 
    /** \brief If \b set, this partially downloaded file will be
     *  removed when the download completes.
@@ -1006,7 +963,7 @@ class APT_HIDDEN pkgAcqIndex : public pkgAcqBaseIndex
    std::string CurrentCompressionExtension;
 
    /** \brief Do the changes needed to fetch via AptByHash (if needed) */
-   void InitByHashIfNeeded(const std::string MetaKey);
+   void InitByHashIfNeeded();
 
    /** \brief Auto select the right compression to use */
    void AutoSelectCompression();
@@ -1015,7 +972,7 @@ class APT_HIDDEN pkgAcqIndex : public pkgAcqBaseIndex
    void ReverifyAfterIMS();
 
    /** \brief Validate the downloaded index file */
-   bool ValidateFile(const std::string &FileName);
+   bool ValidateFile(std::string const &FileName);
 
    /** \brief Get the full pathname of the final file for the current URI */
    virtual std::string GetFinalFilename() const;
@@ -1024,82 +981,20 @@ class APT_HIDDEN pkgAcqIndex : public pkgAcqBaseIndex
 
    public:
    // Specialized action members
-   virtual void Failed(std::string Message,pkgAcquire::MethodConfig *Cnf);
-   virtual void Done(std::string Message,unsigned long long Size, 
-                     HashStringList const &Hashes,
-		     pkgAcquire::MethodConfig *Cnf);
-#if APT_PKG_ABI >= 413
+   virtual void Failed(std::string const &Message,pkgAcquire::MethodConfig const * const Cnf);
+   virtual void Done(std::string const &Message, HashStringList const &Hashes,
+		     pkgAcquire::MethodConfig const * const Cnf);
    virtual std::string Custom600Headers() const;
-#else
-   virtual std::string Custom600Headers();
-#endif
-   virtual std::string DescURI() {return Desc.URI;};
+   virtual std::string DescURI() const {return Desc.URI;};
+   virtual std::string GetMetaKey() const;
+
+   pkgAcqIndex(pkgAcquire * const Owner, pkgAcqMetaBase * const TransactionManager,
+               IndexTarget const * const Target);
 
-   /** \brief Create a pkgAcqIndex.
-    *
-    *  \param Owner The pkgAcquire object with which this item is
-    *  associated.
-    *
-    *  \param URI The URI of the index file that is to be downloaded.
-    *
-    *  \param URIDesc A "URI-style" description of this index file.
-    *
-    *  \param ShortDesc A brief description of this index file.
-    *
-    *  \param ExpectedHashes The expected hashsum of this index file.
-    *
-    *  \param compressExt The compression-related extension with which
-    *  this index file should be downloaded, or "" to autodetect
-    *  Compression types can be set with config Acquire::CompressionTypes,
-    *  default is ".lzma" or ".bz2" (if the needed binaries are present)
-    *  fallback is ".gz" or none.
-    */
-   pkgAcqIndex(pkgAcquire *Owner,std::string URI,std::string URIDesc,
-	       std::string ShortDesc, HashStringList const &ExpectedHashes);
-   pkgAcqIndex(pkgAcquire *Owner, pkgAcqMetaBase *TransactionManager,
-               IndexTarget const * const Target,
-               HashStringList const &ExpectedHash,
-               indexRecords *MetaIndexParser);
-               
    void Init(std::string const &URI, std::string const &URIDesc,
              std::string const &ShortDesc);
 };
 									/*}}}*/
-/** \brief Information about an index file. */				/*{{{*/
-class APT_HIDDEN IndexTarget
-{
-   void *d;
-
- public:
-   /** \brief A URI from which the index file can be downloaded. */
-   std::string URI;
-
-   /** \brief A description of the index file. */
-   std::string Description;
-
-   /** \brief A shorter description of the index file. */
-   std::string ShortDesc;
-
-   /** \brief The key by which this index file should be
-    *  looked up within the meta signature file.
-    */
-   std::string MetaKey;
-
-   virtual bool IsOptional() const {
-      return false;
-   }
-};
-									/*}}}*/
-/** \brief Information about an optional index file. */			/*{{{*/
-class APT_HIDDEN OptionalIndexTarget : public IndexTarget
-{
-   void *d;
-
-   virtual bool IsOptional() const {
-      return true;
-   }
-};
-									/*}}}*/
 /** \brief An item that is responsible for fetching a package file.	{{{
  *
  *  If the package file already exists in the cache, nothing will be
@@ -1109,6 +1004,9 @@ class pkgAcqArchive : public pkgAcquire::Item
 {
    void *d;
 
+   bool LocalSource;
+   HashStringList ExpectedHashes;
+
    protected:
    /** \brief The package version being fetched. */
    pkgCache::VerIterator Version;
@@ -1141,7 +1039,7 @@ class pkgAcqArchive : public pkgAcquire::Item
    /** \brief \b true if this version file is being downloaded from a
     *  trusted source.
     */
-   bool Trusted; 
+   bool Trusted;
 
    /** \brief Queue up the next available file for this version. */
    bool QueueNext();
@@ -1151,17 +1049,15 @@ class pkgAcqArchive : public pkgAcquire::Item
 
    public:
 
-   virtual void Failed(std::string Message,pkgAcquire::MethodConfig *Cnf);
-   virtual void Done(std::string Message,unsigned long long Size, HashStringList const &Hashes,
-		     pkgAcquire::MethodConfig *Cnf);
-   virtual std::string DescURI() {return Desc.URI;};
-   virtual std::string ShortDesc() {return Desc.ShortDesc;};
+   virtual void Failed(std::string const &Message,pkgAcquire::MethodConfig const * const Cnf);
+   virtual void Done(std::string const &Message, HashStringList const &Hashes,
+		     pkgAcquire::MethodConfig const * const Cnf);
+   virtual std::string DescURI() const;
+   virtual std::string ShortDesc() const;
    virtual void Finished();
-#if APT_PKG_ABI >= 413
    virtual bool IsTrusted() const;
-#else
-   virtual bool IsTrusted();
-#endif
+   virtual HashStringList GetExpectedHashes() const;
+   virtual bool HashesRequired() const;
 
    /** \brief Create a new pkgAcqArchive.
     *
@@ -1181,8 +1077,8 @@ class pkgAcqArchive : public pkgAcquire::Item
     *  basename in the constructor, and filled in with a fully
     *  qualified filename once the download finishes.
     */
-   pkgAcqArchive(pkgAcquire *Owner,pkgSourceList *Sources,
-		 pkgRecords *Recs,pkgCache::VerIterator const &Version,
+   pkgAcqArchive(pkgAcquire * const Owner,pkgSourceList * const Sources,
+		 pkgRecords * const Recs,pkgCache::VerIterator const &Version,
 		 std::string &StoreFilename);
 };
 									/*}}}*/
@@ -1200,22 +1096,21 @@ class pkgAcqFile : public pkgAcquire::Item
     *  Acquire::Retries.
     */
    unsigned int Retries;
-   
+
    /** \brief Should this file be considered a index file */
    bool IsIndexFile;
 
+   HashStringList const ExpectedHashes;
    public:
-   
+   virtual HashStringList GetExpectedHashes() const;
+   virtual bool HashesRequired() const;
+
    // Specialized action members
-   virtual void Failed(std::string Message,pkgAcquire::MethodConfig *Cnf);
-   virtual void Done(std::string Message,unsigned long long Size, HashStringList const &CalcHashes,
-		     pkgAcquire::MethodConfig *Cnf);
-   virtual std::string DescURI() {return Desc.URI;};
-#if APT_PKG_ABI >= 413
+   virtual void Failed(std::string const &Message,pkgAcquire::MethodConfig const * const Cnf);
+   virtual void Done(std::string const &Message, HashStringList const &CalcHashes,
+		     pkgAcquire::MethodConfig const * const Cnf);
+   virtual std::string DescURI() const {return Desc.URI;};
    virtual std::string Custom600Headers() const;
-#else
-   virtual std::string Custom600Headers();
-#endif
 
    /** \brief Create a new pkgAcqFile object.
     *
@@ -1248,10 +1143,10 @@ class pkgAcqFile : public pkgAcquire::Item
     * is the absolute name to which the file should be downloaded.
     */
 
-   pkgAcqFile(pkgAcquire *Owner, std::string URI, HashStringList const &Hashes, unsigned long long Size,
-	      std::string Desc, std::string ShortDesc,
-	      const std::string &DestDir="", const std::string &DestFilename="",
-	      bool IsIndexFile=false);
+   pkgAcqFile(pkgAcquire * const Owner, std::string const &URI, HashStringList const &Hashes, unsigned long long const Size,
+	      std::string const &Desc, std::string const &ShortDesc,
+	      std::string const &DestDir="", std::string const &DestFilename="",
+	      bool const IsIndexFile=false);
 };
 									/*}}}*/
 /** @} */