SQL Server

Check if an Email Was Received Digitally Signed

Demonstrates the read-only Chilkat Email.ReceivedSigned property, which is true if the email was originally received carrying one or more digital signatures. Knowing a message was signed is separate from knowing the signature checked out, so this example also reads SignaturesValid to report whether the signed content verified.

Background: A digital signature on an email (S/MIME) provides two things: authenticity (it was really sent by the holder of a particular certificate) and integrity (the content was not altered in transit). The sender signs a hash of the message with their private key; the recipient verifies it with the sender's public certificate. ReceivedSigned simply tells you a signature is present — verifying it is a separate step exposed through SignaturesValid.

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--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @iTmp0 int
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

    --  Demonstrates the read-only Email.ReceivedSigned property, which is true if this
    --  email was originally received with a digital signature.  Use SignaturesValid to
    --  determine whether the signed content actually verified.

    DECLARE @email int
    EXEC @hr = sp_OACreate 'Chilkat.Email', @email OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    EXEC sp_OAMethod @email, 'LoadEml', @success OUT, 'qa_data/eml/signed.eml'
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @email, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @email
        RETURN
      END

    EXEC sp_OAGetProperty @email, 'ReceivedSigned', @iTmp0 OUT
    IF @iTmp0 = 1
      BEGIN

        PRINT 'This email was received with a digital signature.'
        EXEC sp_OAGetProperty @email, 'SignaturesValid', @iTmp0 OUT
        IF @iTmp0 = 1
          BEGIN

            PRINT 'All signatures are valid.'
          END
        ELSE
          BEGIN

            PRINT 'One or more signatures are NOT valid.'
          END
      END
    ELSE
      BEGIN

        PRINT 'This email was not signed.'
      END

    --  Note: Paths such as "qa_data/..." are relative local filesystem paths,
    --  relative to the current working directory of the running application.

    EXEC @hr = sp_OADestroy @email


END
GO