SQL Server

Cache a DKIM Public Key from a File

Demonstrates the Chilkat Dkim.LoadPublicKeyFile method, which caches an RSA public key read from a local file for a specific selector and domain. The arguments are the selector, the domain, and the public-key file path. Supported formats include PEM X.509 SubjectPublicKeyInfo and PEM PKCS#1 RSA public key.

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: This is the file-based form of LoadPublicKey, convenient when the key already lives in a .pem file — a saved copy of what the domain publishes in DNS. As with the string form, the cache is keyed on the exact selector and domain, so those must match the signature being verified. Pre-loading keys this way lets a verifier work without any DNS access at all.

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

    --  Demonstrates the Dkim.LoadPublicKeyFile method, which caches an RSA public key read from a
    --  local file for a specific selector and domain.  The 1st argument is the selector, the 2nd is
    --  the domain, and the 3rd is the local public-key file path.

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

    --  Read the public key from a file and cache it under the exact selector and domain.  Supported
    --  formats include PEM X.509 SubjectPublicKeyInfo and PEM PKCS#1 RSA public key.
    EXEC sp_OAMethod @dkim, 'LoadPublicKeyFile', @success OUT, 'myselector', 'example.com', 'qa_data/dkim_public.pem'
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @dkim, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @dkim
        RETURN
      END

    PRINT 'Public key loaded and cached.'

    EXEC @hr = sp_OADestroy @dkim


END
GO