MIME S/MIME Signing Algorithm Properties

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Demonstrates the properties that control S/MIME signing: SigningAlg (the RSA signature scheme, PKCS1-V1_5 or RSASSA-PSS), SigningHashAlg (the message-digest algorithm), Micalg and Protocol (the micalg and protocol parameters of a multipart/signed Content-Type), and UseXPkcs7 (whether historical x-pkcs7 media-type names are used). The properties are configured before creating a detached signature.

var
success: Boolean;
mime: HCkMime;
pfxPassword: PWideChar;
cert: HCkCert;

begin
success := False;

mime := CkMime_Create();
success := CkMime_SetBodyFromPlainText(mime,'This message will be signed.');
if (success = False) then
  begin
    Memo1.Lines.Add(CkMime__lastErrorText(mime));
    Exit;
  end;

//  SigningAlg is the RSA signature scheme.  The default is PKCS1-V1_5; set RSASSA-PSS (or pss) for
//  RSASSA-PSS.
CkMime_putSigningAlg(mime,'PKCS1-V1_5');

//  SigningHashAlg is the message-digest algorithm.  The default is sha256.
CkMime_putSigningHashAlg(mime,'sha256');

//  Micalg and Protocol are the micalg and protocol parameters written into a multipart/signed
//  Content-Type header field.  They are normally set automatically, but can be controlled here.
CkMime_putMicalg(mime,'sha-256');
CkMime_putProtocol(mime,'application/pkcs7-signature');

//  UseXPkcs7 controls whether newly created S/MIME media types use the historical x-pkcs7 names.
CkMime_putUseXPkcs7(mime,False);

//  Load a signing certificate (with private key access) from a PFX.  The PFX password should come
//  from a secure source rather than being hard-coded.
pfxPassword := 'myPfxPassword';
cert := CkCert_Create();
success := CkCert_LoadPfxFile(cert,'qa_data/signer.pfx',pfxPassword);
if (success = False) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

//  Create the detached signature using the algorithms configured above.
success := CkMime_AddDetachedSignature(mime,cert);
if (success = False) then
  begin
    Memo1.Lines.Add(CkMime__lastErrorText(mime));
    Exit;
  end;

Memo1.Lines.Add('Signed with SigningAlg=' + CkMime__signingAlg(mime) + ' SigningHashAlg=' + CkMime__signingHashAlg(mime));

CkMime_Dispose(mime);
CkCert_Dispose(cert);