Skip to content

Fix auth tag issues when using GCM cipher with stream-based methods #48

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 3 commits into from
Nov 19, 2022
Merged

Fix auth tag issues when using GCM cipher with stream-based methods #48

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
408b806
Add test cases for streaming Decode/Encode into DEC's GCM test suite.
denovosoftware Nov 8, 2022
cc3af2f
Address issue in TDECFormattedCipher.DoEncodeDecodeStream where GCM b…
denovosoftware Nov 8, 2022
35a5a5f
Address DEC issue with auth tag not being generated for GCM mode for …
denovosoftware Nov 8, 2022
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
20 changes: 18 additions & 2 deletions Source/DECCipherFormats.pas
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -726,6 +726,7 @@ procedure TDECFormattedCipher.DoEncodeDecodeStream(const Source, Dest: TStream;
const OnProgress: TDECProgressEvent);
var
Buffer: TBytes;
outBuffer: TBytes;
BufferSize, Bytes: Integer;
Max, StartPos, Pos: Int64;
begin
Expand All @@ -737,6 +738,7 @@ procedure TDECFormattedCipher.DoEncodeDecodeStream(const Source, Dest: TStream;
StartPos := Pos;

if DataSize > 0 then
begin
try
if Assigned(OnProgress) then
OnProgress(Max, 0, Started);
Expand All @@ -752,6 +754,11 @@ procedure TDECFormattedCipher.DoEncodeDecodeStream(const Source, Dest: TStream;
SetLength(Buffer, BufferSize)
else
SetLength(Buffer, DataSize);

outBuffer := Buffer;
if (FMode = cmGCM) then
SetLength(outBuffer, Length(Buffer));

while DataSize > 0 do
begin
Bytes := BufferSize;
Expand All @@ -760,8 +767,8 @@ procedure TDECFormattedCipher.DoEncodeDecodeStream(const Source, Dest: TStream;
Source.ReadBuffer(Buffer[0], Bytes);

// The real encryption or decryption routine
CipherProc(Buffer[0], Buffer[0], Bytes);
Dest.WriteBuffer(Buffer[0], Bytes);
CipherProc(Buffer[0], outBuffer[0], Bytes);
Dest.WriteBuffer(outBuffer[0], Bytes);
Dec(DataSize, Bytes);
Inc(Pos, Bytes);

Expand All @@ -770,9 +777,18 @@ procedure TDECFormattedCipher.DoEncodeDecodeStream(const Source, Dest: TStream;
end;
finally
ProtectBytes(Buffer);
if (FMode = cmGCM) then
ProtectBytes(outBuffer);
if Assigned(OnProgress) then
OnProgress(Max, Max, Finished);
end;
end
else
if (FMode = cmGCM) then
begin
Buffer := nil;
CipherProc(Buffer, Buffer, 0);
end;
end;

procedure TDECFormattedCipher.EncodeStream(const Source, Dest: TStream; DataSize: Int64;
Expand Down
153 changes: 152 additions & 1 deletion Unit Tests/Tests/TestDECCipherModesGCM.pas
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -223,7 +223,9 @@ TestTDECGCM = class(TTestCase)
published
procedure TestEncode;
procedure TestDecode;
procedure TestDecodeStream;
procedure TestDecodeAuthenticationFailure;
procedure TestEncodeStream;
procedure TestSetGetDataToAuthenticate;
procedure TestSetGetAuthenticationBitLength;
procedure TestGetStandardAuthenticationTagBitLengths;
Expand Down Expand Up @@ -472,7 +474,9 @@ procedure TestTDECGCM.TestDecode;
BytesOf(TestDataSet.TestData[i].CT)));
FCipherAES.Done;
except
self.Status('CryptKey ' + string(TestDataSet.TestData[i].CryptKey));
on E: Exception do
Status('CryptKey ' + string(TestDataSet.TestData[i].CryptKey) +
' ' + E.ClassName + ': ' + E.Message);
end;

CheckEquals(string(TestDataSet.TestData[i].PT),
Expand Down Expand Up @@ -631,6 +635,153 @@ function TestTDECGCM.IsEqual(const a, b : TBytes):Boolean;
Result := true;
end;

procedure TestTDECGCM.TestDecodeStream;
var
ctbStream: TBytesStream;
ctBytes: TBytes;
TestDataSet : TGCMTestSetEntry;
i : Integer;
DecryptData : TBytes;
ptbStream: TBytesStream;
begin
FTestDataLoader.LoadFile('..\..\Unit Tests\Data\gcmEncryptExtIV128.rsp', FTestDataList);
FTestDataLoader.LoadFile('..\..\Unit Tests\Data\gcmEncryptExtIV192.rsp', FTestDataList);
FTestDataLoader.LoadFile('..\..\Unit Tests\Data\gcmEncryptExtIV256.rsp', FTestDataList);

for TestDataSet in FTestDataList do
begin
for i := Low(TestDataSet.TestData) to High(TestDataSet.TestData) do
begin
ctBytes := TFormat_HexL.Decode(BytesOf(TestDataSet.TestData[i].CT));

try


FCipherAES.Init(BytesOf(TFormat_HexL.Decode(TestDataSet.TestData[i].CryptKey)),
BytesOf(TFormat_HexL.Decode(TestDataSet.TestData[i].InitVector)),
$FF);

FCipherAES.AuthenticationResultBitLength := TestDataSet.Taglen;
FCipherAES.DataToAuthenticate := TFormat_HexL.Decode(
BytesOf(
TestDataSet.TestData[i].AAD));

FCipherAES.ExpectedAuthenticationResult :=
TFormat_HexL.Decode(BytesOf(TestDataSet.TestData[i].TagResult));

ctbStream := TBytesStream.Create(ctBytes);
ptbStream := TBytesStream.Create;

FCipherAES.DecodeStream(ctbStream, ptbStream, ctbStream.Size);

FCipherAES.Done;

DecryptData := ptbStream.Bytes;
SetLength(DecryptData, ptbStream.Size);

except
on E: Exception do
Status('CryptKey ' + string(TestDataSet.TestData[i].CryptKey) +
' ' + E.ClassName + ': ' + E.Message);
end;
FreeAndNil(ptbStream);
FreeAndNil(ctbStream);

CheckEquals(string(TestDataSet.TestData[i].PT),
StringOf(TFormat_HexL.Encode(DecryptData)),
'Plaintext wrong for key ' +
string(TestDataSet.TestData[i].CryptKey) + ' IV ' +
string(TestDataSet.TestData[i].InitVector) + ' PT ' +
string(TestDataSet.TestData[i].PT) + ' AAD ' +
string(TestDataSet.TestData[i].AAD) + ' Exp.: ' +
string(TestDataSet.TestData[i].CT) + ' Act.: ' +
StringOf(TFormat_HexL.Encode(DecryptData)));

// Additional Authentication Data pr�fen
CheckEquals(string(TestDataSet.TestData[i].TagResult),
StringOf(TFormat_HexL.Encode(FCipherAES.CalculatedAuthenticationResult)),
'Authentication tag wrong for key ' +
string(TestDataSet.TestData[i].CryptKey) + ' IV ' +
string(TestDataSet.TestData[i].InitVector) + ' PT ' +
string(TestDataSet.TestData[i].PT) + ' AAD ' +
string(TestDataSet.TestData[i].AAD) + ' Exp.: ' +
string(TestDataSet.TestData[i].TagResult) + ' Act.: ' +
StringOf(TFormat_HexL.Encode(FCipherAES.DataToAuthenticate)));

end;
end;
end;

procedure TestTDECGCM.TestEncodeStream;
var
ctbStream: TBytesStream;
ptBytes: TBytes;
TestDataSet : TGCMTestSetEntry;
i : Integer;
EncryptData : TBytes;
ptbStream: TBytesStream;
begin
FTestDataLoader.LoadFile('..\..\Unit Tests\Data\gcmEncryptExtIV128.rsp', FTestDataList);
FTestDataLoader.LoadFile('..\..\Unit Tests\Data\gcmEncryptExtIV192.rsp', FTestDataList);
FTestDataLoader.LoadFile('..\..\Unit Tests\Data\gcmEncryptExtIV256.rsp', FTestDataList);

for TestDataSet in FTestDataList do
begin
for i := Low(TestDataSet.TestData) to High(TestDataSet.TestData) do
begin
ptBytes := TFormat_HexL.Decode(BytesOf(TestDataSet.TestData[i].PT));

FCipherAES.Init(BytesOf(TFormat_HexL.Decode(TestDataSet.TestData[i].CryptKey)),
BytesOf(TFormat_HexL.Decode(TestDataSet.TestData[i].InitVector)),
$FF);

FCipherAES.AuthenticationResultBitLength := TestDataSet.Taglen;
FCipherAES.DataToAuthenticate := TFormat_HexL.Decode(
BytesOf(
TestDataSet.TestData[i].AAD));

ptbStream := TBytesStream.Create(ptBytes);
ctbStream := TBytesStream.Create;
try
FCipherAES.EncodeStream(ptbStream, ctbStream, ptbStream.Size);

FCipherAES.Done;

EncryptData := ctbStream.Bytes;
SetLength(EncryptData, ctbStream.Size);
except
on E: Exception do
Status('CryptKey ' + string(TestDataSet.TestData[i].CryptKey) +
' ' + E.ClassName + ': ' + E.Message);
end;

FreeAndNil(ptbStream);
FreeAndNil(ctbStream);

CheckEquals(string(TestDataSet.TestData[i].CT),
StringOf(TFormat_HexL.Encode(EncryptData)),
'Cipher text wrong for Key ' +
string(TestDataSet.TestData[i].CryptKey) + ' IV ' +
string(TestDataSet.TestData[i].InitVector) + ' PT ' +
string(TestDataSet.TestData[i].PT) + ' AAD ' +
string(TestDataSet.TestData[i].AAD) + ' Exp.: ' +
string(TestDataSet.TestData[i].CT) + ' Act.: ' +
StringOf(TFormat_HexL.Encode(EncryptData)));

// Additional Authentication Data pr�fen
CheckEquals(string(TestDataSet.TestData[i].TagResult),
StringOf(TFormat_HexL.Encode(FCipherAES.CalculatedAuthenticationResult)),
'Authentication tag wrong for Key ' +
string(TestDataSet.TestData[i].CryptKey) + ' IV ' +
string(TestDataSet.TestData[i].InitVector) + ' PT ' +
string(TestDataSet.TestData[i].PT) + ' AAD ' +
string(TestDataSet.TestData[i].AAD) + ' Exp.: ' +
string(TestDataSet.TestData[i].TagResult) + ' Act.: ' +
StringOf(TFormat_HexL.Encode(FCipherAES.DataToAuthenticate)));
end;
end;
end;

procedure TestTDECGCM.TestGetStandardAuthenticationTagBitLengths;
var
BitLengths: TStandardBitLengths;
Expand Down