SQL Server

Sign PDF: Choosing RSASSA-PSS or PKCS1-v1_5 and Hash Algorithm

See more PDF Signatures Examples

This example demonstrates how to choose between RSASSA-PSS vs. PKCS1-v1_5 and the hash algorithm when signing a PDF. SQL Server

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

    -- This example requires the Chilkat API to have been previously unlocked.
    -- See Global Unlock Sample for sample code.

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

    -- Load a PDF to be signed.
    -- The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
    EXEC sp_OAMethod @pdf, 'LoadFile', @success OUT, 'qa_data/pdf/hello.pdf'
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @pdf, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @pdf
        RETURN
      END

    -- Options for signing are specified in JSON.
    DECLARE @json int
    EXEC @hr = sp_OACreate 'Chilkat.JsonObject', @json OUT

    -- In most cases, the signingCertificateV2 attribute is needed.
    EXEC sp_OAMethod @json, 'UpdateInt', @success OUT, 'signingCertificateV2', 1

    -- ---------------------------------------------------------------------------------------------------------------------------
    -- This example is the same as the example at Sign a PDF (Simplest Example Possible)
    -- but with the following lines added to specify the signature scheme and hash algorithm.

    -- The signature schemes PKCS-v1_5 and RSASSA-PSS have differences. 
    -- PKCSV1_5 is deterministic. The same message and key will produce an identical signature value each time. 
    -- PSS is randomized and will produce a different signature value each time.

    -- To choose the hash algorithm:
    -- (The typical choices are sha1, sha256, sha384, and sha512.)
    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'hashAlgorithm', 'sha256'

    -- To choose PKCSV1_5:
    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'signingAlgorithm', 'pkcs'
    -- Alternatively, to choose RSASSA-PSS:
    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'signingAlgorithm', 'pss'

    -- If not specified, the default is SHA256 with PKCS-v1_5.

    -- The remainder of this example is the same as the example at Sign a PDF (Simplest Example Possible)
    -- ---------------------------------------------------------------------------------------------------------------------------

    -- Put the signature on page 1, top left
    EXEC sp_OAMethod @json, 'UpdateInt', @success OUT, 'page', 1
    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'appearance.y', 'top'
    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'appearance.x', 'left'

    -- Use a font scale of 10.0
    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'appearance.fontScale', '10.0'

    -- In this example, the appearance of the digital signature will contain three lines:
    -- 1) The signing certificate's common name
    -- 2) The current date/time
    -- 3) Some arbitrary text.
    -- The keyword "cert_cn" is replaced with the Certificate's Subject Common Name.
    -- The keyword "current_dt" is replaced with the current date/time.
    -- Any number of appearance text lines can be added.
    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'appearance.text[0]', 'Digitally signed by: cert_cn'
    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'appearance.text[1]', 'current_dt'
    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'appearance.text[2]', 'The crazy brown fox jumps over the lazy dog.'

    -- Load the signing certificate. (Use your own certificate.)
    DECLARE @cert int
    EXEC @hr = sp_OACreate 'Chilkat.Cert', @cert OUT

    EXEC sp_OAMethod @cert, 'LoadPfxFile', @success OUT, 'qa_data/pfx/myPdfSigningCert.pfx', 'secret'
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @cert, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @pdf
        EXEC @hr = sp_OADestroy @json
        EXEC @hr = sp_OADestroy @cert
        RETURN
      END

    -- Tell the pdf object to use the certificate for signing.
    EXEC sp_OAMethod @pdf, 'SetSigningCert', @success OUT, @cert
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @pdf, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @pdf
        EXEC @hr = sp_OADestroy @json
        EXEC @hr = sp_OADestroy @cert
        RETURN
      END

    EXEC sp_OAMethod @pdf, 'SignPdf', @success OUT, @json, 'qa_output/hello_signed.pdf'
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @pdf, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @pdf
        EXEC @hr = sp_OADestroy @json
        EXEC @hr = sp_OADestroy @cert
        RETURN
      END


    PRINT 'The PDF has been successfully cryptographically signed.'

    -- The appearance of the signature appears in Adobe Acrobat as shown here:

    -- (image:https://example-code.com/images/signature1.jpg/endImage)

    EXEC @hr = sp_OADestroy @pdf
    EXEC @hr = sp_OADestroy @json
    EXEC @hr = sp_OADestroy @cert


END
GO