From abe5e8ecea0325176440765df5b1e1af86f4e292 Mon Sep 17 00:00:00 2001
From: Felix Geyer <debfx@fobos.de>
Date: Mon, 20 Jul 2015 21:02:57 +0200
Subject: [PATCH] Don't write final block(s) if we already have.

---
 src/streams/HashedBlockStream.cpp     |  8 ++++++--
 src/streams/SymmetricCipherStream.cpp | 29 ++++++++++++++++++---------
 src/streams/SymmetricCipherStream.h   |  2 ++
 3 files changed, 27 insertions(+), 12 deletions(-)

diff --git a/src/streams/HashedBlockStream.cpp b/src/streams/HashedBlockStream.cpp
index cd43dc0bf..ec59769aa 100644
--- a/src/streams/HashedBlockStream.cpp
+++ b/src/streams/HashedBlockStream.cpp
@@ -54,7 +54,9 @@ void HashedBlockStream::init()
 
 bool HashedBlockStream::reset()
 {
-    if (isWritable()) {
+    // Write final block(s) only if device is writable and we haven't
+    // already written a final block.
+    if (isWritable() && (!m_buffer.isEmpty() || m_blockIndex != 0)) {
         if (!m_buffer.isEmpty()) {
             if (!writeHashedBlock()) {
                 return false;
@@ -74,7 +76,9 @@ bool HashedBlockStream::reset()
 
 void HashedBlockStream::close()
 {
-    if (isWritable()) {
+    // Write final block(s) only if device is writable and we haven't
+    // already written a final block.
+    if (isWritable() && (!m_buffer.isEmpty() || m_blockIndex != 0)) {
         if (!m_buffer.isEmpty()) {
             writeHashedBlock();
         }
diff --git a/src/streams/SymmetricCipherStream.cpp b/src/streams/SymmetricCipherStream.cpp
index d230920f2..643aa0339 100644
--- a/src/streams/SymmetricCipherStream.cpp
+++ b/src/streams/SymmetricCipherStream.cpp
@@ -25,6 +25,7 @@ SymmetricCipherStream::SymmetricCipherStream(QIODevice* baseDevice, SymmetricCip
     , m_bufferFilling(false)
     , m_error(false)
     , m_isInitalized(false)
+    , m_dataWritten(false)
 {
 }
 
@@ -43,6 +44,16 @@ bool SymmetricCipherStream::init(const QByteArray& key, const QByteArray& iv)
     return m_isInitalized;
 }
 
+void SymmetricCipherStream::resetInternalState()
+{
+    m_buffer.clear();
+    m_bufferPos = 0;
+    m_bufferFilling = false;
+    m_error = false;
+    m_dataWritten = false;
+    m_cipher->reset();
+}
+
 bool SymmetricCipherStream::open(QIODevice::OpenMode mode)
 {
     if (!m_isInitalized) {
@@ -54,27 +65,25 @@ bool SymmetricCipherStream::open(QIODevice::OpenMode mode)
 
 bool SymmetricCipherStream::reset()
 {
-    if (isWritable()) {
+    if (isWritable() && m_dataWritten) {
         if (!writeBlock(true)) {
             return false;
         }
     }
 
-    m_buffer.clear();
-    m_bufferPos = 0;
-    m_bufferFilling = false;
-    m_error = false;
-    m_cipher->reset();
+    resetInternalState();
 
     return true;
 }
 
 void SymmetricCipherStream::close()
 {
-    if (isWritable()) {
+    if (isWritable() && m_dataWritten) {
         writeBlock(true);
     }
 
+    resetInternalState();
+
     LayeredStream::close();
 }
 
@@ -186,6 +195,7 @@ qint64 SymmetricCipherStream::writeData(const char* data, qint64 maxSize)
         return -1;
     }
 
+    m_dataWritten = true;
     qint64 bytesRemaining = maxSize;
     qint64 offset = 0;
 
@@ -214,6 +224,8 @@ qint64 SymmetricCipherStream::writeData(const char* data, qint64 maxSize)
 
 bool SymmetricCipherStream::writeBlock(bool lastBlock)
 {
+    Q_ASSERT(lastBlock || (m_buffer.size() == m_cipher->blockSize()));
+
     if (lastBlock) {
         // PKCS7 padding
         int padLen = m_cipher->blockSize() - m_buffer.size();
@@ -221,9 +233,6 @@ bool SymmetricCipherStream::writeBlock(bool lastBlock)
             m_buffer.append(static_cast<char>(padLen));
         }
     }
-    else if (m_buffer.isEmpty()) {
-        return true;
-    }
 
     if (!m_cipher->processInPlace(m_buffer)) {
         m_error = true;
diff --git a/src/streams/SymmetricCipherStream.h b/src/streams/SymmetricCipherStream.h
index c1865babc..fa446053f 100644
--- a/src/streams/SymmetricCipherStream.h
+++ b/src/streams/SymmetricCipherStream.h
@@ -42,6 +42,7 @@ protected:
     qint64 writeData(const char* data, qint64 maxSize) Q_DECL_OVERRIDE;
 
 private:
+    void resetInternalState();
     bool readBlock();
     bool writeBlock(bool lastBlock);
 
@@ -51,6 +52,7 @@ private:
     bool m_bufferFilling;
     bool m_error;
     bool m_isInitalized;
+    bool m_dataWritten;
 };
 
 #endif // KEEPASSX_SYMMETRICCIPHERSTREAM_H