5.7

1 files changed, 51 insertions, 44 deletions

diff --git a/wx+/zlib_wrap.h b/wx+/zlib_wrap.h
index c229a589..9fa50240 100644
--- a/wx+/zlib_wrap.h
+++ b/wx+/zlib_wrap.h
@@ -1,7 +1,7 @@
 // **************************************************************************
 // * This file is part of the FreeFileSync project. It is distributed under *
 // * GNU General Public License: http://www.gnu.org/licenses/gpl.html       *
-// * Copyright (C) ZenJu (zhnmju123 AT gmx DOT de) - All Rights Reserved    *
+// * Copyright (C) ZenJu (zenju AT gmx DOT de) - All Rights Reserved        *
 // **************************************************************************
 
 #ifndef SIMPLE_H_INCLUDED_18134135134135345489
@@ -55,27 +55,28 @@ template <class BinContainer>
 BinContainer compress(const BinContainer& stream, int level) //throw ZlibInternalError
 {
     BinContainer contOut;
-
-    //save uncompressed stream size for decompression
-    const std::uint64_t uncompressedSize = stream.size(); //use portable number type!
-    contOut.resize(sizeof(uncompressedSize));
-    std::copy(reinterpret_cast<const char*>(&uncompressedSize),
-              reinterpret_cast<const char*>(&uncompressedSize) + sizeof(uncompressedSize),
-              &*contOut.begin());
-
-    const size_t bufferEstimate = impl::zlib_compressBound(stream.size()); //upper limit for buffer size, larger than input size!!!
-
-    contOut.resize(contOut.size() + bufferEstimate);
-
-    const size_t bytesWritten = impl::zlib_compress(&*stream.begin(),
-                                                    stream.size(),
-                                                    &*contOut.begin() + contOut.size() - bufferEstimate,
-                                                    bufferEstimate,
-                                                    level); //throw ZlibInternalError
-    if (bytesWritten < bufferEstimate)
-        contOut.resize(contOut.size() - (bufferEstimate - bytesWritten)); //caveat: unsigned arithmetics
-    //caveat: physical memory consumption still *unchanged*!
-
+    if (!stream.empty()) //don't dereference iterator into empty container!
+    {
+        //save uncompressed stream size for decompression
+        const std::uint64_t uncompressedSize = stream.size(); //use portable number type!
+        contOut.resize(sizeof(uncompressedSize));
+        std::copy(reinterpret_cast<const char*>(&uncompressedSize),
+                  reinterpret_cast<const char*>(&uncompressedSize) + sizeof(uncompressedSize),
+                  &*contOut.begin());
+
+        const size_t bufferEstimate = impl::zlib_compressBound(stream.size()); //upper limit for buffer size, larger than input size!!!
+
+        contOut.resize(contOut.size() + bufferEstimate);
+
+        const size_t bytesWritten = impl::zlib_compress(&*stream.begin(),
+                                                        stream.size(),
+                                                        &*contOut.begin() + contOut.size() - bufferEstimate,
+                                                        bufferEstimate,
+                                                        level); //throw ZlibInternalError
+        if (bytesWritten < bufferEstimate)
+            contOut.resize(contOut.size() - (bufferEstimate - bytesWritten)); //caveat: unsigned arithmetics
+        //caveat: physical memory consumption still *unchanged*!
+    }
     return contOut;
 }
 
@@ -83,31 +84,37 @@ BinContainer compress(const BinContainer& stream, int level) //throw ZlibInterna
 template <class BinContainer>
 BinContainer decompress(const BinContainer& stream) //throw ZlibInternalError
 {
-    //retrieve size of uncompressed data
-    std::uint64_t uncompressedSize = 0; //use portable number type!
-    if (stream.size() < sizeof(uncompressedSize))
-        throw ZlibInternalError();
-    std::copy(&*stream.begin(),
-              &*stream.begin() + sizeof(uncompressedSize),
-              reinterpret_cast<char*>(&uncompressedSize));
-
     BinContainer contOut;
-    try
-    {
-        contOut.resize(uncompressedSize); //throw std::bad_alloc
-    }
-    catch (std::bad_alloc&) //most likely due to data corruption!
+    if (!stream.empty()) //don't dereference iterator into empty container!
     {
-        throw ZlibInternalError();
+        //retrieve size of uncompressed data
+        std::uint64_t uncompressedSize = 0; //use portable number type!
+        if (stream.size() < sizeof(uncompressedSize))
+            throw ZlibInternalError();
+        std::copy(&*stream.begin(),
+                  &*stream.begin() + sizeof(uncompressedSize),
+                  reinterpret_cast<char*>(&uncompressedSize));
+        try
+        {
+            //attention: contOut MUST NOT be empty! Else it will pass a nullptr to zlib_decompress() => Z_STREAM_ERROR although "uncompressedSize == 0"!!!
+            //secondary bug: don't dereference iterator into empty container!
+            if (uncompressedSize == 0) //cannot be 0: compress() directly maps empty -> empty container skipping zlib!
+                throw ZlibInternalError();
+
+            contOut.resize(uncompressedSize); //throw std::bad_alloc
+        }
+        catch (std::bad_alloc&) //most likely due to data corruption!
+        {
+            throw ZlibInternalError();
+        }
+
+        const size_t bytesWritten = impl::zlib_decompress(&*stream.begin() + sizeof(uncompressedSize),
+                                                          stream.size() - sizeof(uncompressedSize),
+                                                          &*contOut.begin(),
+                                                          uncompressedSize); //throw ZlibInternalError
+        if (bytesWritten != uncompressedSize)
+            throw ZlibInternalError();
     }
-
-    const size_t bytesWritten = impl::zlib_decompress(&*stream.begin() + sizeof(uncompressedSize),
-                                                      stream.size() - sizeof(uncompressedSize),
-                                                      &*contOut.begin(),
-                                                      uncompressedSize); //throw ZlibInternalError
-    if (bytesWritten != uncompressedSize)
-        throw ZlibInternalError();
-
     return contOut;
 }
 }