Objective-C

Verify an XML Signature with Multiple References

See more XML Digital Signatures Examples

Demonstrates how to verify an XML digital signature that contains multiple references. Objective-C

#import <CkoHttp.h>
#import <CkoStringBuilder.h>
#import <CkoXmlDSig.h>

BOOL success = NO;

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

//  An example of an enveloping XML signature with mulitple references is available at
//  https://www.chilkatsoft.com/exampleData/envelopedMultipleRefs.xml

//  This example will show how to verify the signature and all references, and also how
//  to verify each reference individually.  This is useful to distinguish which part
//  of the XML signature validation failed.  It could be that one or more of the references
//  failed because of a hash computation mismatch.  Or it could be that the signature over
//  the SignedInfo failed.  

//  First, let's grab the sample XML signature.
CkoHttp *http = [[CkoHttp alloc] init];
CkoStringBuilder *sbXml = [[CkoStringBuilder alloc] init];
success = [http QuickGetSb: @"https://www.chilkatsoft.com/exampleData/envelopedMultipleRefs.xml" sbContent: sbXml];
if (success != YES) {
    NSLog(@"%@",http.LastErrorText);
    return;
}

//  Load the XML containing the signature to be verified.
CkoXmlDSig *verifier = [[CkoXmlDSig alloc] init];
success = [verifier LoadSignatureSb: sbXml];
if (success != YES) {
    NSLog(@"%@",verifier.LastErrorText);
    return;
}

BOOL verifyReferenceDigests = YES;

//  The quick way to validate all references and the signature over the SignedInfo
//  is to call VerifySignature with verifyReferenceDigests equal to true.
BOOL verified = [verifier VerifySignature: verifyReferenceDigests];
NSLog(@"%@%d",@"Signature and all reference digests verified = ",verified);

//  Let's pretend the call to VerifySignature returned false.  Something did not validate.
//  Was it one or more of the References that did not hash to the correct value?
//  Or was it the signature over the SignedInfo that failed?
//  We can check just the signature over the SignedInfo by passing false to VerifySignature.
//  This allows us to skip the hashing and checking each Reference.  
verifyReferenceDigests = NO;
BOOL signedInfoVerified = [verifier VerifySignature: verifyReferenceDigests];
NSLog(@"%@%d",@"Neglecting the reference hashes, the SignedInfo validation result = ",signedInfoVerified);

//  We can also verify each reference digest separately
int numRefs = [verifier.NumReferences intValue];
int i = 0;
while (i < numRefs) {
    BOOL refDigestVerified = [verifier VerifyReferenceDigest: [NSNumber numberWithInt: i]];
    NSLog(@"%@%d%@%d",@"Reference ",i,@" digest verified = ",refDigestVerified);
    i = i + 1;
}

//  For this sample XML signature with 3 References, we get the following output:

//  Signature and all reference digests verified = True
//  Neglecting the reference hashes, the SignedInfo validation result = True
//  Reference 0 digest verified = True
//  Reference 1 digest verified = True
//  Reference 2 digest verified = True