add zero-block pass-through option, enabling allow-holes code

git-svn-id: http://encfs.googlecode.com/svn/trunk@14 db9cf616-1c43-0410-9cb8-a902689de0d6

encfs/BlockFileIO.cpp

@@ -189,7 +189,7 @@ bool BlockFileIO::write( const IORequest &req )
     if(lastBlockSize == 0)
 	--lastNonEmptyBlock;
 
-    if( (req.offset > fileSize) && !_allowHoles )
+    if( req.offset > fileSize )
     {
 	// extend file first to fill hole with 0's..
 	const bool forceWrite = false;
@@ -340,7 +340,9 @@ void BlockFileIO::padFile( off_t oldSize, off_t newSize, bool forceWrite )
 	    ++oldLastBlock;
 	}
 
-	// 2
+	// 2, pad zero blocks unless holes are allowed
+        if(!_allowHoles)
+        {
             for(; oldLastBlock != newLastBlock; ++oldLastBlock)
             {
                 rDebug("padding block %" PRIi64, oldLastBlock);
@@ -349,6 +351,7 @@ void BlockFileIO::padFile( off_t oldSize, off_t newSize, bool forceWrite )
                 memset( mb.data, 0, req.dataLen );
                 cacheWriteOneBlock( req );
             }
+        }
 
 	// 3. only necessary if write is forced and block is non 0 length
 	if(forceWrite && newBlockSize)

encfs/BlockFileIO.h

@@ -40,12 +40,12 @@ public:
 
     virtual int blockSize() const;
 
-protected:
-
     // default is false, but setting this to true will allow holes to be stored
     // in the file.  Only works if supported by the underlying FileIO
     // implementation..
-    void allowHoles( bool allow );
+    virtual void allowHoles( bool allow );
+
+protected:
 
     int truncate( off_t size, FileIO *base );
     void padFile( off_t oldSize, off_t newSize, bool forceWrite );

encfs/CipherFileIO.cpp

@@ -372,7 +372,18 @@ bool CipherFileIO::blockRead( unsigned char *buf, int size,
     if (reverseEncryption)
 	return cipher->blockEncode( buf, size, _iv64, key );
     else
+    {
+        if(_allowHoles)
+        {
+            // special case - leave all 0's alone
+            for(int i=0; i<size; ++i)
+                if(buf[i] != 0)
                     return cipher->blockDecode( buf, size, _iv64, key );
+
+            return true;
+        } else
+            return cipher->blockDecode( buf, size, _iv64, key );
+    }
 } 
 
 bool CipherFileIO::streamRead( unsigned char *buf, int size, 

encfs/DirNode.cpp

@@ -726,7 +726,8 @@ shared_ptr<FileNode> DirNode::findOrCreate( const char *plainName)
 		config->uniqueIV,
 		config->externalIVChaining,
 		config->forceDecode,
-		config->reverseEncryption) );
+		config->reverseEncryption,
+                config->allowHoles) );
 		
 	if(config->externalIVChaining)
 	    node->setName(0, 0, iv);

encfs/DirNode.h

@@ -101,6 +101,7 @@ public:
 	bool externalIVChaining;
 	bool forceDecode; // force decoding, even if errors are detected
 	bool reverseEncryption;  
+        bool allowHoles; // allow holes in files
 	Config()
 	    : fsSubVersion(0)
 	    , blockSize(1)
@@ -111,6 +112,7 @@ public:
 	    , externalIVChaining( false )
 	    , forceDecode( false )
 	    , reverseEncryption ( false )
+            , allowHoles( false )
 	    { }
     };
 

encfs/FileNode.cpp

@@ -48,6 +48,7 @@
 using namespace std;
 using namespace rel;
 using namespace rlog;
+using boost::dynamic_pointer_cast;
 
 /*
    TODO: locking at the FileNode level is inefficient, since this precludes
@@ -65,7 +66,8 @@ FileNode::FileNode(DirNode *parent_,
 	const char *plaintextName_, const char *cipherName_, 
 	const shared_ptr<Cipher> &dataCipher, const CipherKey &key, 
 	int blockSize, int blockMACBytes, int blockMACRandBytes, bool uniqueIV,
-	bool externalIVChaining_, bool forceDecode, bool reverseEncryption_ )
+	bool externalIVChaining_, bool forceDecode, bool reverseEncryption_,
+        bool allowHoles )
 {
     pthread_mutex_init( &mutex, 0 );
     
@@ -88,6 +90,9 @@ FileNode::FileNode(DirNode *parent_,
 	io = shared_ptr<FileIO>(new MACFileIO(io, dataCipher, key, 
 		    blockSize,blockMACBytes,blockMACRandBytes,forceDecode));
     }
+
+    if(allowHoles)
+        dynamic_pointer_cast<BlockFileIO>(io)->allowHoles( allowHoles );
 }
 
 FileNode::~FileNode()

encfs/FileNode.h

@@ -43,7 +43,8 @@ public:
 	    bool uniqueIV, // enable per-file initialization vectors
 	    bool externalIVChaining,
 	    bool forceDecode, // decode, even if decoding errors are detected
-	    bool reverseEncryption );
+	    bool reverseEncryption,
+            bool allowHoles );
     ~FileNode();
 
     const char *plaintextName() const;

encfs/FileUtils.cpp

@@ -272,6 +272,8 @@ bool readV5Config( const char *configFile, EncFSConfig *config,
 	    config->blockMACRandBytes = 
 		cfgRdr["blockMACRandBytes"].readInt(0);
 	   
+            config->allowHoles = cfgRdr["allowHoles"].readBool( false );
+
 	    ok = true;
 	} catch( rlog::Error &err)
 	{
@@ -411,6 +413,7 @@ bool writeV5Config( const char *configFile, EncFSConfig *config )
     cfg["uniqueIV"] << config->uniqueIV;
     cfg["chainedIV"] << config->chainedNameIV;
     cfg["externalIV"] << config->externalIVChaining;
+    cfg["allowHoles"] << config->allowHoles;
 
     return cfg.save( configFile );
 }
@@ -680,22 +683,34 @@ int selectBlockSize( const Cipher::CipherAlgorithm &alg )
 }
 
 static
-void selectBlockMAC(int *macBytes, int *macRandBytes)
+bool boolDefaultNo(const char *prompt)
 {
-    // xgroup(setup)
-    cout << _("Enable block authentication code headers\n"
-	"on every block in a file?  This adds about 12 bytes per block\n"
-	"to the storage requirements for a file, and significantly affects\n"
-	"performance but it also means [almost] any modifications or errors\n"
-	"within a block will be caught and will cause a read error.\n"
-	"The default here is No.  \n"
+    cout << prompt << "\n";
+    cout << _("The default here is No.\n"
               "Any response that does not begin with 'y' will mean No: ");
 
     char answer[10];
     fgets( answer, sizeof(answer), stdin );
     cout << "\n";
 
-    if(tolower(answer[0]) == 'y')
+    if(tolower(answer[0]) == 'n')
+	return false;
+    else
+	return true;
+}
+
+static 
+void selectBlockMAC(int *macBytes, int *macRandBytes)
+{
+    // xgroup(setup)
+    bool addMAC = boolDefaultNo(
+            _("Enable block authentication code headers\n"
+	"on every block in a file?  This adds about 12 bytes per block\n"
+	"to the storage requirements for a file, and significantly affects\n"
+	"performance but it also means [almost] any modifications or errors\n"
+	"within a block will be caught and will cause a read error."));
+
+    if(addMAC)
     {
 	*macBytes = 8;
 
@@ -708,6 +723,7 @@ void selectBlockMAC(int *macBytes, int *macRandBytes)
 	    "penalty. \n"
 	    "Select a number of bytes, from 0 (no random bytes) to 8: ");
    
+        char answer[10];
 	int randSize = 0;
 	fgets( answer, sizeof(answer), stdin );
 	cout << "\n";
@@ -727,69 +743,65 @@ void selectBlockMAC(int *macBytes, int *macRandBytes)
 }
 
 static
-bool selectUniqueIV()
+bool boolDefaultYes(const char *prompt)
 {
-    // xgroup(setup)
-    cout << _("Enable per-file initialization vectors?\n"
-	"This adds about 8 bytes per file to the storage requirements.\n"
-	"It should not affect performance except possibly with applications\n"
-	"which rely on block-aligned file io for performance.\n"
-	"The default here is Yes.  \n"
+    cout << prompt << "\n";
+    cout << _("The default here is Yes.\n"
               "Any response that does not begin with 'n' will mean Yes: ");
 
     char answer[10];
     fgets( answer, sizeof(answer), stdin );
     cout << "\n";
 
-    if(tolower(answer[0]) == 'n')
-	return false;
-    else
-	return true;
-}
-
-static 
-bool selectChainedIV()
-{
-    // xgroup(setup)
-    cout << _("Enable filename initialization vector chaining?\n"
-	"This makes filename encoding dependent on the complete path, \n"
-	"rather then encoding each path element individually. \n"
-	"This is normally desireable, therefor the default is Yes. \n"
-	"Any response that does not begin with 'n' will mean Yes: ");
-
-    char answer[10];
-    fgets( answer, sizeof(answer), stdin );
-    cout << "\n";
-
-    if(tolower(answer[0]) == 'n')
-	return false;
-    else
-	return true;
-}
-
-static 
-bool selectExternalChainedIV()
-{
-    // xgroup(setup)
-    cout << _("Enable filename to IV header chaining?\n"
-	"This makes file data encoding dependent on the complete file path.\n"
-	"If a file is renamed, it will not decode sucessfully unless it\n"
-	"was renamed by encfs with the proper key.\n"
-	"If this option is enabled, then hard links will not be supported\n"
-	"in the filesystem.\n"
-	"The default is No. \n"
-	"Any response that does not begin with 'y' will mean No: ");
-
-    char answer[10];
-    fgets( answer, sizeof(answer), stdin );
-    cout << "\n";
-
     if(tolower(answer[0]) == 'y')
 	return true;
     else
 	return false;
 }
 
+static 
+bool selectUniqueIV()
+{
+    // xgroup(setup)
+    return boolDefaultYes(
+            _("Enable per-file initialization vectors?\n"
+	"This adds about 8 bytes per file to the storage requirements.\n"
+	"It should not affect performance except possibly with applications\n"
+	"which rely on block-aligned file io for performance."));
+}
+
+static 
+bool selectChainedIV()
+{
+    // xgroup(setup)
+    return boolDefaultYes(
+            _("Enable filename initialization vector chaining?\n"
+	"This makes filename encoding dependent on the complete path, \n"
+	"rather then encoding each path element individually."));
+}
+
+static 
+bool selectExternalChainedIV()
+{
+    // xgroup(setup)
+    return boolDefaultNo(
+            _("Enable filename to IV header chaining?\n"
+	"This makes file data encoding dependent on the complete file path.\n"
+	"If a file is renamed, it will not decode sucessfully unless it\n"
+	"was renamed by encfs with the proper key.\n"
+	"If this option is enabled, then hard links will not be supported\n"
+	"in the filesystem."));
+}
+
+static 
+bool selectZeroBlockPassThrough()
+{
+    // xgroup(setup)
+    return boolDefaultNo(
+            _("Enable file-hole pass-through?\n"
+	"This avoids writing encrypted blocks when file holes are created."));
+}
+
 RootPtr createV5Config( EncFS_Context *ctx, const std::string &rootDir, 
 	bool enableIdleTracking, bool forceDecode,
 	const std::string &passwordProgram,
@@ -822,6 +834,7 @@ RootPtr createV5Config( EncFS_Context *ctx, const std::string &rootDir,
     bool uniqueIV = false;
     bool chainedIV = false;
     bool externalIV = false;
+    bool allowHoles = false;
     
     if (reverseEncryption)
     {
@@ -861,13 +874,11 @@ RootPtr createV5Config( EncFS_Context *ctx, const std::string &rootDir,
     {
 	// xgroup(setup)
 	cout << _("Standard configuration selected.") << "\n";
-	// look for blowfish with 160 bit key..
-	// block name encoding is now standard as well..
-	// per-file initialization vectors are now standard, as they shouldn't
-	// have any significant performance penalty.
-	keySize = 160;
+	// AES w/ 192 bit key, block name encoding, per-file initialization
+        // vectors are all standard.
+	keySize = 192;
 	blockSize = DefaultBlockSize;
-	alg = findCipherAlgorithm("Blowfish", keySize);
+	alg = findCipherAlgorithm("AES", keySize);
 	blockMACBytes = 0;
 	externalIV = false;
 	nameIOIface = BlockNameIO::CurrentInterface();
@@ -917,10 +928,11 @@ RootPtr createV5Config( EncFS_Context *ctx, const std::string &rootDir,
 		// xgroup(setup)
 		cout << _("External chained IV disabled, as both 'IV chaining'\n"
 		    "and 'unique IV' features are required for this option.") 
-		<< endl;
+                    << "\n";
 		externalIV = false;
 	    }
 	    selectBlockMAC(&blockMACBytes, &blockMACRandBytes);
+            allowHoles = selectZeroBlockPassThrough();
 	}
     }
 
@@ -949,6 +961,7 @@ RootPtr createV5Config( EncFS_Context *ctx, const std::string &rootDir,
     config.uniqueIV = uniqueIV;
     config.chainedNameIV = chainedIV;
     config.externalIVChaining = externalIV;
+    config.allowHoles = allowHoles;
 
     cout << "\n";
     // xgroup(setup)
@@ -1035,6 +1048,7 @@ RootPtr createV5Config( EncFS_Context *ctx, const std::string &rootDir,
     dirNodeConfig->externalIVChaining = config.externalIVChaining;
     dirNodeConfig->forceDecode = forceDecode;
     dirNodeConfig->reverseEncryption = reverseEncryption;
+    dirNodeConfig->allowHoles = config.allowHoles;
 
     rootInfo = RootPtr( new EncFS_Root );
     rootInfo->cipher = cipher;
@@ -1145,6 +1159,11 @@ void showFSInfo( const EncFSConfig &config )
 	// xgroup(diag)
 	cout << _("File data IV is chained to filename IV.\n");
     }
+    if(config.allowHoles)
+    {
+	// xgroup(diag)
+	cout << _("File holes passed through to ciphertext.\n");
+    }
     cout << "\n";
 }
     

encfs/FileUtils.h

@@ -58,6 +58,7 @@ struct EncFSConfig
     bool externalIVChaining; // IV seeding by filename IV chaining
 
     bool chainedNameIV; // filename IV chaining
+    bool allowHoles; // allow holes in files (implicit zero blocks)
 };
 
 enum ConfigType

encfs/MACFileIO.cpp

@@ -30,6 +30,8 @@
 using namespace rlog;
 using namespace rel;
 using namespace std;
+using boost::shared_ptr;
+using boost::dynamic_pointer_cast;
 
 static RLogChannel *Info = DEF_CHANNEL("info/MACFileIO", Log_Info);
 //
@@ -157,6 +159,14 @@ off_t MACFileIO::getSize() const
     return size;
 }
 
+void MACFileIO::allowHoles( bool allow )
+{
+    BlockFileIO::allowHoles( allow );
+    shared_ptr<BlockFileIO> bf = dynamic_pointer_cast<BlockFileIO>( base );
+    if(bf)
+        bf->allowHoles( allow );
+}
+
 ssize_t MACFileIO::readOneBlock( const IORequest &req ) const
 {
     int headerSize = macBytes + randBytes;
@@ -173,10 +183,26 @@ ssize_t MACFileIO::readOneBlock( const IORequest &req ) const
     // get the data from the base FileIO layer
     ssize_t readSize = base->read( tmp );
 
+    // don't store zeros if configured for zero-block pass-through
+    bool skipBlock;
+    if( _allowHoles )
+    {
+        skipBlock = true;
+        for(int i=0; i<readSize; ++i)
+            if(tmp.data[i] != 0)
+            {
+                skipBlock = false;
+                break;
+            }
+    } else
+       skipBlock = false; 
+
     if(readSize > headerSize)
     {
-	// At this point the data has been decoded.  So, compute the MAC of the
-	// block and check against the checksum stored in the header..
+        if(!skipBlock)
+        {
+            // At this point the data has been decoded.  So, compute the MAC of
+            // the block and check against the checksum stored in the header..
             uint64_t mac = cipher->MAC_64( tmp.data + macBytes, 
                     readSize - macBytes, key );
 
@@ -193,11 +219,13 @@ ssize_t MACFileIO::readOneBlock( const IORequest &req ) const
                     if( !warnOnly )
                     {
                         MemoryPool::release( mb );
-		    throw ERROR(_("MAC comparison failure, refusing to read"));
+                        throw ERROR(
+                                _("MAC comparison failure, refusing to read"));
                     }
                     break;
                 }
             }
+        }
 
 	// now copy the data to the output buffer
 	readSize -= headerSize;

encfs/MACFileIO.h

@@ -53,6 +53,8 @@ public:
 
     virtual bool isWritable() const;
 
+    virtual void allowHoles( bool allow );
+
 private:
     virtual ssize_t readOneBlock( const IORequest &req ) const;
     virtual bool writeOneBlock( const IORequest &req );