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.

#import <CkoMime.h>
#import <NSString.h>
#import <CkoCert.h>

BOOL success = NO;

CkoMime *mime = [[CkoMime alloc] init];
success = [mime SetBodyFromPlainText: @"This message will be signed."];
if (success == NO) {
    NSLog(@"%@",mime.LastErrorText);
    return;
}

//  SigningAlg is the RSA signature scheme.  The default is PKCS1-V1_5; set RSASSA-PSS (or pss) for
//  RSASSA-PSS.
mime.SigningAlg = @"PKCS1-V1_5";

//  SigningHashAlg is the message-digest algorithm.  The default is sha256.
mime.SigningHashAlg = @"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.
mime.Micalg = @"sha-256";
mime.Protocol = @"application/pkcs7-signature";

//  UseXPkcs7 controls whether newly created S/MIME media types use the historical x-pkcs7 names.
mime.UseXPkcs7 = NO;

//  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.
NSString *pfxPassword = @"myPfxPassword";
CkoCert *cert = [[CkoCert alloc] init];
success = [cert LoadPfxFile: @"qa_data/signer.pfx" password: pfxPassword];
if (success == NO) {
    NSLog(@"%@",cert.LastErrorText);
    return;
}

//  Create the detached signature using the algorithms configured above.
success = [mime AddDetachedSignature: cert];
if (success == NO) {
    NSLog(@"%@",mime.LastErrorText);
    return;
}

NSLog(@"%@%@%@%@",@"Signed with SigningAlg=",mime.SigningAlg,@" SigningHashAlg=",mime.SigningHashAlg);