[fpc-pascal] HMAC_SHA1 and FPC

[silvioprog]

A small improvement:

uses
  SHA1;

function SHA1Raw(const ABuffer; const ABufferLength: PtrUInt): string;
var
  I: Byte;
  VBytes : TBytes;
  VDigest: TSHA1Digest;
  VContext: TSHA1Context;
begin
  Result := '';
  SHA1Init(VContext);
  SHA1Update(VContext, ABuffer, ABufferLength);
  SHA1Final(VContext, VDigest);
  SetLength(VBytes, 20);
  Move(VDigest, VBytes[0], 20);
  for I := 0 to 19 do
    Result := Result + Char(VBytes[I]);
end;

function HMACSHA1(const AKey, AMessage: string): string;
const
  BLOCK_SIZE = 64;
var
  I: Byte;
  VKey: string;
  VLenght: PtrUInt;
  VOPad, VIPad: string;
begin
  VLenght := Length(AKey);
  if VLenght > BLOCK_SIZE then
  begin
    SetLength(VKey, BLOCK_SIZE);
    FillChar(Pointer(VKey)^, BLOCK_SIZE, #0);
    VKey := SHA1Raw(Pointer(AKey)^, VLenght) + VKey;
  end
  else
  begin
    SetLength(VKey, BLOCK_SIZE - VLenght);
    FillChar(Pointer(VKey)^, BLOCK_SIZE - VLenght, #0);
    VKey := AKey + VKey;
  end;
  SetLength(VOPad, BLOCK_SIZE);
  FillChar(Pointer(VOPad)^, BLOCK_SIZE, $5c);
  SetLength(VIPad, BLOCK_SIZE);
  FillChar(Pointer(VIPad)^, BLOCK_SIZE, $36);
  for I := 1 to BLOCK_SIZE do
  begin
    VOPad[I] := Char(Byte(VOPad[I]) xor Byte(VKey[I]));
    VIPad[I] := Char(Byte(VIPad[I]) xor Byte(VKey[I]));
  end;
  VIPad := VIPad + AMessage;
  Result := SHA1Print(SHA1String(VOPad + SHA1Raw(Pointer(VIPad)^,
Length(VIPad))));
end;

-- 
Silvio Clécio
My public projects - github.com/silvioprog
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