RSAVerifySignature with optional RSASignModes parameter

General
1

Hello,

Does anybody know if the undocumented, optional RSASignModes parameter to the RSAVerifySignature works? I cannot get it to verify a valid SHA512 signature when passing Crypto.RSASignModes.SHA2_512 for that parameter.

Thank you.

2

You should provide example code here and file a bug report with Xojo.

3

Well, I don’t know if it’s a bug exactly, since the parameter isn’t in the official docs. It’s only in the code completion, so that’s why I’m asking if anybody knows if it’s supported officially.

Here’s a simple code snippet:

Var PublicKey As String = "-----BEGIN PUBLIC KEY-----" + EndOfLine + _
"..." + EndOfLine + _
"-----END PUBLIC KEY-----"

Var Key As String = PublicKey.Trim
Key = Key.ReplaceAll(Encodings.UTF8.Chr(13) + Encodings.UTF8.Chr(10), Encodings.UTF8.Chr(10))
Key = Key.ReplaceAll(Encodings.UTF8.Chr(13), Encodings.UTF8.Chr(10))

Var Lines() As String = Key.Split(Encodings.UTF8.Chr(10))
Lines.RemoveAt(0)
Lines.RemoveAt(Lines.LastIndex)

Key = String.FromArray(Lines, Encodings.UTF8.Chr(10))
Var DecodedKey As String = DecodeBase64(Key)

// Message is a DesktopTextField
Var data As String = Message.Text.Trim

// Signature is a DesktopTextArea
Var decodedSig As String = Signature.Text
decodedSig = decodedSig.Trim
decodedSig = decodedSig.ReplaceLineEndings("")
decodedSig = decodedSig.ReplaceAll(" ", "")
decodedSig = DecodeBase64(decodedSig)

if Crypto.RSAVerifyKey(EncodeHex(DecodedKey)) then
  // NOTE: The 'Crypto.RSASignModes.SHA2_512' parameter below is the one in question
  If Crypto.RSAVerifySignature(EncodeHex(data), EncodeHex(decodedSig), EncodeHex(DecodedKey), Crypto.RSASignModes.SHA2_512) Then
    Status.Text = "Verified!"
  else
    Status.Text = "BAD signature"
  end
else
  Status.Text = "BAD key"
end

Note that the message and signature are valid according to openssl command line tools.

4

Don’t pass the hex encoded strings. Those are for human eyes. Decode the hex and pass the binary strings to the function

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