gistfile1.m

#import <Foundation/Foundation.h>
#import <Security/Security.h>

static const char *public_key = "-----BEGIN DSA PUBLIC KEY-----\n"
"MIHxMIGoBgcqhkjOOAQBMIGcAkEAvPM8vp7lHRrWFhpso2I/Wrq1qV8TSl7/YITH\n"
"7cHsINCP/xrZZpTlx14pKNkKwEEf3t3bdkKY97NQKRJ+cIRyawIVAMDJQP8l7EVy\n"
"fcqtVnJjJupPIccxAkBhLjwIRUNerlWb0kW357ABc4+65XB90lQIdcwVLGqRsx9A\n"
"wKoeeMUEyVdQhjJMnclvYJU+xqnl2AP9224QOGGLA0QAAkEAkFQyL1jGMfEjer1O\n"
"QjBq7knMY8zHEUVNRbPXBNS5QenFg07rgMUFL/Bj6/876pWvubwpDAcXkiK+SR3A\n"
"FRF/VA==\n"
"-----END DSA PUBLIC KEY-----\n";

/*
-----BEGIN DSA PRIVATE KEY-----
MIH4AgEAAkEAvPM8vp7lHRrWFhpso2I/Wrq1qV8TSl7/YITH7cHsINCP/xrZZpTl
x14pKNkKwEEf3t3bdkKY97NQKRJ+cIRyawIVAMDJQP8l7EVyfcqtVnJjJupPIccx
AkBhLjwIRUNerlWb0kW357ABc4+65XB90lQIdcwVLGqRsx9AwKoeeMUEyVdQhjJM
nclvYJU+xqnl2AP9224QOGGLAkEAkFQyL1jGMfEjer1OQjBq7knMY8zHEUVNRbPX
BNS5QenFg07rgMUFL/Bj6/876pWvubwpDAcXkiK+SR3AFRF/VAIUYOxpRfxp9Y+q
PirXRY83qU9vUXo=
-----END DSA PRIVATE KEY-----
*/

BOOL verify_separate(SecKeyRef publicKey, NSData *base32SignatureData, NSData *digest) {
	BOOL result = NO;
	SecTransformRef decoder = SecDecodeTransformCreate(kSecBase32Encoding, NULL);
	SecTransformSetAttribute(decoder, kSecTransformInputAttributeName, base32SignatureData, NULL);
	CFDataRef signature = SecTransformExecute(decoder, NULL);

	SecTransformRef verifier = SecVerifyTransformCreate(publicKey, signature, NULL);
	SecTransformSetAttribute(verifier, kSecTransformInputAttributeName, digest, NULL);
	SecTransformSetAttribute(verifier, kSecDigestTypeAttribute, kSecDigestSHA1, NULL);

	CFErrorRef error;
	CFBooleanRef transformResult = SecTransformExecute(verifier, &error);
	if (transformResult) {
		result = (transformResult == kCFBooleanTrue);
		CFRelease(transformResult);
	} else if (error) {
		CFShow(error);
	}

	CFRelease(verifier);
	CFRelease(signature);
	CFRelease(decoder);
	return result;
}

BOOL verify_group(SecKeyRef publicKey, NSData *base32SignatureData, NSData *digest) {
	BOOL result = NO;
	SecGroupTransformRef group = SecTransformCreateGroupTransform();

	SecTransformRef decoder = SecDecodeTransformCreate(kSecBase32Encoding, NULL);
	SecTransformSetAttribute(decoder, kSecTransformInputAttributeName, base32SignatureData, NULL);

	SecTransformRef verifier = SecVerifyTransformCreate(publicKey, NULL, NULL);
	SecTransformSetAttribute(verifier, kSecTransformInputAttributeName, digest, NULL);
	SecTransformSetAttribute(verifier, kSecDigestTypeAttribute, kSecDigestSHA1, NULL);

	SecTransformConnectTransforms(decoder, kSecTransformOutputAttributeName,
								  verifier, kSecSignatureAttributeName,
								  group, NULL);

	CFErrorRef error;
	CFBooleanRef transformResult = SecTransformExecute(group, &error);
	if (transformResult) {
		result = (transformResult == kCFBooleanTrue);
		CFRelease(transformResult);
	} else if (error) {
		CFShow(error);
	}

	CFRelease(verifier);
	CFRelease(decoder);
	CFRelease(group);
	return result;
}

int main(int argc, char *argv[]) {
	@autoreleasepool {
		int i;

		NSData *publicKeyData = [NSData dataWithBytes:public_key length:strlen(public_key)];
		SecItemImportExportKeyParameters params = {};
		SecExternalItemType keyType = kSecItemTypePublicKey;
		SecExternalFormat keyFormat = kSecFormatPEMSequence;
		CFArrayRef importArray = NULL;
		
		SecItemImport((CFDataRef)publicKeyData,
		              NULL,
		              &keyFormat,
		              &keyType,
		              0,
		              &params,
		              NULL,
		              &importArray);
		
		SecKeyRef publicKey = (SecKeyRef)CFArrayGetValueAtIndex(importArray, 0);
		
		NSString *base32Signature = @"GAWAEFANCOPCYDRNUWUNG3OPNKNV6RR6QO4UWFICCQMR2YFHMGYWMWWT2OZIOBS7WTMTJ6APNI======";
		NSData *base32SignatureData = [base32Signature dataUsingEncoding:NSUTF8StringEncoding];
		NSData *digest = [@"Test" dataUsingEncoding:NSUTF8StringEncoding];
		
		// This always works
		for (i=0; i < 100; i++) {
			if (!verify_separate(publicKey, base32SignatureData, digest)) {
				NSLog(@"Failed at iteration %d", i);
				return 1;
			}
		}
		
		// This doesn't
		for (i=0; i < 100; i++) {
			if (!verify_group(publicKey, base32SignatureData, digest)) {
				NSLog(@"Failed at iteration %d", i);
				return 1;
			}
		}
		
		NSLog(@"Passed");
		
		CFRelease(importArray);
	}
}