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make sure the underlying stream is only written when the write transaction is commited. Avoids corrupted files when cancelling Yubichallenge during saving (#4)

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This commit is contained in:
Philipp Crocoll
2018-07-09 12:34:21 +02:00
parent dc39f874ac
commit caf42d423f
1 changed files with 35 additions and 54 deletions
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89
src/Kp2aBusinessLogic/Io/CachingFileStorage.cs
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@@ -345,57 +345,7 @@ namespace keepass2android.Io
private class CachedWriteTransaction: IWriteTransaction
{
private class CachedWriteMemoryStream : MemoryStream
{
private readonly IOConnectionInfo ioc;
private readonly CachingFileStorage _cachingFileStorage;
private readonly bool _useFileTransaction;
private bool _closed;
public CachedWriteMemoryStream(IOConnectionInfo ioc, CachingFileStorage cachingFileStorage, bool useFileTransaction)
{
this.ioc = ioc;
_cachingFileStorage = cachingFileStorage;
_useFileTransaction = useFileTransaction;
}
public override void Close()
{
if (_closed) return;
//write file to cache:
//(note: this might overwrite local changes. It's assumed that a sync operation or check was performed before
string hash;
using (var hashingStream = new HashingStreamEx(File.Create(_cachingFileStorage.CachedFilePath(ioc)), true, new SHA256Managed()))
{
Position = 0;
CopyTo(hashingStream);
hashingStream.Close();
hash = MemUtil.ByteArrayToHexString(hashingStream.Hash);
}
File.WriteAllText(_cachingFileStorage.VersionFilePath(ioc), hash);
//update file on remote. This might overwrite changes there as well, see above.
Position = 0;
if (_cachingFileStorage.IsCached(ioc))
{
//if the file already is in the cache, it's ok if writing to remote fails.
_cachingFileStorage.TryUpdateRemoteFile(this, ioc, _useFileTransaction, hash);
}
else
{
//if not, we don't accept a failure (e.g. invalid credentials would always remain a problem)
_cachingFileStorage.UpdateRemoteFile(this, ioc, _useFileTransaction, hash);
}
base.Close();
_closed = true;
}
}
private readonly IOConnectionInfo _ioc;
private readonly bool _useFileTransaction;
@@ -429,17 +379,48 @@ namespace keepass2android.Io
public Stream OpenFile()
{
_memoryStream = new CachedWriteMemoryStream(_ioc, _cachingFileStorage, _useFileTransaction);
_memoryStream = new MemoryStream();
return _memoryStream;
}
public void CommitWrite()
{
//the transaction is committed in the stream's Close
_committed = true;
_memoryStream.Close();
//write file to cache:
//(note: this might overwrite local changes. It's assumed that a sync operation or check was performed before
byte[] output = _memoryStream.ToArray();
string hash;
using (var hashingStream = new HashingStreamEx(File.Create(_cachingFileStorage.CachedFilePath(_ioc)), true, new SHA256Managed()))
{
hashingStream.Write(output, 0, output.Length);
hashingStream.Close();
hash = MemUtil.ByteArrayToHexString(hashingStream.Hash);
}
File.WriteAllText(_cachingFileStorage.VersionFilePath(_ioc), hash);
//create another memory stream which is open for reading again
MemoryStream openMemStream = new MemoryStream(output);
//update file on remote. This might overwrite changes there as well, see above.
if (_cachingFileStorage.IsCached(_ioc))
{
//if the file already is in the cache, it's ok if writing to remote fails.
_cachingFileStorage.TryUpdateRemoteFile(openMemStream, _ioc, _useFileTransaction, hash);
}
else
{
//if not, we don't accept a failure (e.g. invalid credentials would always remain a problem)
_cachingFileStorage.UpdateRemoteFile(openMemStream, _ioc, _useFileTransaction, hash);
}
openMemStream.Dispose();
}
}
}
public IWriteTransaction OpenWriteTransaction(IOConnectionInfo ioc, bool useFileTransaction)