delphi THashSHA2 return a wrong SHA256 on huge file
Data.Cloud.CloudAPI.pas has class function TCloudSHA256Authentication.GetStreamToHashSHA256Hex(const Content: TStream): string; that return wrong SHA 256 on some file.
class function TCloudSHA256Authentication.GetStreamToHashSHA256Hex(const Content: TStream): string;
var
LBytes : TBytes;
Hash: THashSHA2;
begin
LBytes := TBytesStream(Content).Bytes;
//Hash bytes
Hash := THashSHA2.Create;
Hash.Update(LBytes);
Result := Hash.HashAsString;
end;
AWS S3 return error:
The provided x-amz-content-sha256 header does not match what was computed
GetStreamToHashSHA256Hex seems produce a different sha256 from amazon:
<ClientComputedContentSHA256>f43ee89e2b7758057bb1f33eb8546d4c2c118f2ab932de89dbd74aabc0651053</ClientComputedContentSHA256>
<S3ComputedContentSHA256>3bbf5f864cc139cf6392b4623bd782a69d16929db713bffaa68035f8a5c3c0ce</S3ComputedContentSHA256>
I have made some tests wit a myfile.zip (600 MB) ...
TIdHashSHA256 an alternative from Indy return the right SHA256 (same of aws s3), eg.:
var
aFileStream: TFileStream;
aHash: TIdHashSHA256;
begin
aFileStream := TFileStream.Create('C:myfile.zip', fmOpenRead or fmShareDenyWrite);
aHash := TIdHashSHA256.Create;
try
Result := aHash.HashStreamAsHex(aFileStream).ToLower;
finally
aFileStream.Free;
aHash.Free;
end;
end;
hash_file() from PHP return the right SHA256 (same of aws s3), eg.:
hash_file('sha256', 'C:myfile.zip');
but THashSHA2 return a wrong sha256, eg.:
var
LBytes : TBytes;
Hash: THashSHA2;
begin
LBytes := TFile.ReadAllBytes('C:myfile.zip');
Hash := THashSHA2.Create;
Hash.Update(LBytes);
Result := Hash.HashAsString;
end;
why?
UPDATE
this is my bug fix. Import Data.Cloud.CloudAPI.pas into the project and rewrite these function:
uses IdHash, IdHashSHA, IdSSLOpenSSL;
class function TCloudSHA256Authentication.GetHashSHA256Hex( HashString: string): string;
var
aHash: TIdHashSHA256;
begin
LoadOpenSSLLibrary;
try
if not(TIdHashSHA256.IsAvailable) then
raise Exception.Create('HashSHA256 Isn''t available!');
aHash := TIdHashSHA256.Create;
try
Result := aHash.HashStringAsHex(HashString).ToLower;
finally
aHash.Free;
end;
finally
UnLoadOpenSSLLibrary;
end;
end;
class function TCloudSHA256Authentication.GetStreamToHashSHA256Hex(const Content: TStream): string;
var
aHash: TIdHashSHA256;
begin
LoadOpenSSLLibrary;
try
if not(TIdHashSHA256.IsAvailable) then
raise Exception.Create('HashSHA256 Isn''t available!');
aHash := TIdHashSHA256.Create;
try
Result := aHash.HashStreamAsHex(Content).ToLower;
finally
aHash.Free;
end;
finally
UnLoadOpenSSLLibrary;
end;
end;
UPDATE 2
i have also try to implement the FredS suggestion, it works:
class function TCloudSHA256Authentication.GetHashSHA256Hex( HashString: string): string;
var
Content: TStringStream;
Hash: THashSHA2;
LBytes: TArray<Byte>;
Buffer: PByte;
BufLen: Integer;
Readed: Integer;
begin
BufLen := 16 * 1024;
Buffer := AllocMem(BufLen);
Hash := THashSHA2.Create;
Content := TStringStream.Create(HashString);
try
while Content.Position < Content.Size do
begin
Readed := Content.Read(Buffer^, BufLen);
if Readed > 0 then
Hash.update(Buffer^, Readed);
end;
finally
Content.Free;
FreeMem(Buffer);
end;
Result := Hash.HashAsString;
end;
class function TCloudSHA256Authentication.GetStreamToHashSHA256Hex(const Content: TStream): string;
var
LBytes : TBytes;
Hash: THashSHA2;
Buffer: PByte;
BufLen: Integer;
Readed: Integer;
begin
BufLen := 16 * 1024;
Buffer := AllocMem(BufLen);
Hash := THashSHA2.Create;
try
Content.Seek(0, soFromBeginning);
while Content.Position < Content.Size do
begin
Readed := Content.Read(Buffer^, BufLen);
if Readed > 0 then
Hash.update(Buffer^, Readed);
end;
Content.Seek(0, soFromBeginning);
finally
FreeMem(Buffer);
end;
Result := Hash.HashAsString;
end;
I just tested a +1.5 GB file using MS Cyrpto and THashSHA2 on Berlin, they both returned the same hash but MS Crypto like OpenSSL is much faster.
The problem is that the file is too large to hold in TBytes in one chunk. My record helper has TBytes.MaxLen = $F000; {61440} TBytes.MaxLen = $F000; {61440} so you need to use a TFileStream and read the file in chunks into HashSHA2.Update instead.
Update: As per David Heffernan's comment I retested TBytes.MaxLen and it appears to be only limited by available memory.
Practical Example and Speed comparison between MS Crypto and Delphi HashSha2
Note: Requires Jedi API
program SHA2SpeedTest;
{$APPTYPE CONSOLE}
{$R *.res}
uses
JwaWindows, Winapi.Windows, System.SysUtils, System.Classes, System.Diagnostics, System.Hash;
const
SHA256_LEN = 256 div 8;
ChunkSize = $F000;
type
TBytesHelper = record helper for TBytes
public
function BinToHex: string;
end;
function TBytesHelper.BinToHex: string;
var
Len : Integer;
begin
Len := Length(Self);
SetLength(Result, Len * 2));
System.Classes.BinToHex(Self, PChar(Result), Len);
end;
procedure DelphiHash256(const AStream: TStream; out Bytes: TBytes);
var
HashSHA2: THashSHA2;
BytesRead: Integer;
begin
HashSHA2 := THashSHA2.create;
SetLength(Bytes, ChunkSize);
AStream.Position := 0;
repeat
BytesRead := AStream.Read(Bytes, ChunkSize);
if (BytesRead = 0) then Break; // Done
HashSHA2.Update(Bytes, BytesRead);
until False;
Bytes := HashSHA2.HashAsBytes;
end;
function CryptoHash256(const AStream: TStream; out Bytes: TBytes): Boolean;
var
SigLen : Cardinal;
hHash : HCRYPTHASH;
hProv : HCRYPTPROV;
BytesRead: Integer;
begin
hProv := 0; hHash := 0;
Result := False;
If not CryptAcquireContext(hProv, nil, nil, PROV_RSA_AES, CRYPT_VERIFYCONTEXT) then Exit;
try
if not CryptCreateHash(hProv, CALG_SHA_256, 0, 0, hHash) then Exit;
try
SetLength(Bytes, ChunkSize);
AStream.Position := 0;
repeat
BytesRead := AStream.Read(Bytes, ChunkSize);
if (BytesRead = 0) then Break; // Done
if not CryptHashData(hHash, @Bytes[0], BytesRead, 0) then Exit;
until False;
SigLen := SHA256_LEN;
SetLength(Bytes, SigLen);
Result := CryptGetHashParam(hHash, HP_HASHVAL, @Bytes[0], SigLen, 0);
finally
CryptDestroyHash(hHash);
end;
finally
CryptReleaseContext(hProv, 0);
end;
end;
var
Stream: TStream;
Bytes : TBytes;
sw : TStopwatch;
CryptoTicks : int64;
FileName : string;
{* CheckFileName *}
function CheckFileName: boolean;
begin
if (FileName='') then FileName := ParamStr(0);
Result := FileExists(FileName);
if not Result then Writeln('Invalid File name');
end;
begin
repeat
Writeln('Please Enter a valid File name, empty for this Executable');
Readln(FileName);
until CheckFileName;
try
Stream := TFileStream.Create(FileName, fmOpenRead + fmShareDenyNone);
try
WriteLn('Crypto - Calculating Checksum');
sw.Start;
if not CryptoHash256(Stream, Bytes) then raise Exception.Create('Something Happened :)');
sw.Stop;
Writeln(Bytes.BinToHex);
WriteLn('Elapsed: ' + sw.Elapsed.ToString);
CryptoTicks := sw.ElapsedTicks;
WriteLn('Delphi - Calculating Checksum');
sw.Reset; sw.Start;
DelphiHash256(Stream, Bytes);
sw.Stop;
Writeln(Bytes.BinToHex);
WriteLn('Elapsed: ' + sw.Elapsed.ToString);
Writeln(Format('MS Crypto is %d%% faster', [(sw.ElapsedTicks-CryptoTicks) * 100 div CryptoTicks]));
finally
Stream.Free;
end;
Writeln('Hit <Enter> to exit');
Readln;
except
on E: Exception do Writeln(E.ClassName, ': ', E.Message);
end;
end.
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