SQL Server

Add an S/MIME Detached Signature

Demonstrates the Chilkat Mime.AddDetachedSignature method, which creates an S/MIME detached signature. The only argument is the signing Cert, which must have access to its private key. On success the entity becomes a multipart/signed with the content and a separate signature part.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: A detached signature (multipart/signed) keeps the original content readable alongside a separate signature part — so recipients whose software does not understand S/MIME still see the message, they just cannot verify it. That backward compatibility makes detached the usual choice for signed email. The signer proves authorship with a certificate that carries its private key.

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-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

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

    EXEC sp_OAMethod @mime, 'SetBodyFromPlainText', @success OUT, 'This message will be signed.'
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @mime, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @mime
        RETURN
      END
    --  Load the signing certificate (which must have access to its private key) from a PFX file.
    --  The PFX password should come from a secure source rather than being hard-coded.
    DECLARE @pfxPassword nvarchar(4000)
    SELECT @pfxPassword = 'myPfxPassword'
    DECLARE @cert int
    EXEC @hr = sp_OACreate 'Chilkat.Cert', @cert OUT

    EXEC sp_OAMethod @cert, 'LoadPfxFile', @success OUT, 'qa_data/signer.pfx', @pfxPassword
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @cert, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @mime
        EXEC @hr = sp_OADestroy @cert
        RETURN
      END

    --  Create an S/MIME detached signature.  The object becomes a multipart/signed entity with the
    --  original content and a separate signature part.
    EXEC sp_OAMethod @mime, 'AddDetachedSignature', @success OUT, @cert
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @mime, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @mime
        EXEC @hr = sp_OADestroy @cert
        RETURN
      END

    EXEC sp_OAMethod @mime, 'SaveMime', @success OUT, 'qa_output/signed.eml'
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @mime, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @mime
        EXEC @hr = sp_OADestroy @cert
        RETURN
      END

    PRINT 'Detached signature added.'

    EXEC @hr = sp_OADestroy @mime
    EXEC @hr = sp_OADestroy @cert


END
GO