将私钥(SecRefKey)转换为NSData或Base64

Question

我有一个p12文件，我从中提取私钥，公钥作为SecKeyRef和证书作为SecCertificateRef。

P12 文件有一个 ECDSA 私钥，我需要使用它来签署数据 （ECC）。

所以我正在使用一个建议的库：https://github.com/ricmoo/GMEllipticCurveCrypto

但是我需要用 Base64 或 NSData 上的密钥为库提供，我不能提供 SecKeyRef。我设法使用此处提供的方法提取公钥的 NSData，它有效。

但是我找不到任何方法将指向私钥的SecRefKey转换为NSData。关于如何执行此操作的任何想法，或者，使用带有 SecKeyRefs 的 ECC 在 iOS 中签名和验证数据。

---

作为参考，此方法将 P12 转换为 iOS SecRefs：

- (BOOL)storeDetailsForP12CertificateData:(NSData *)certData password:(NSString*)pass identifier:(NSString*)identifier{    
    SecKeyRef publicKey, privateKey;
    SecCertificateRef certRef;
    //Extract keys and Certificate
    NSMutableDictionary * options = [[NSMutableDictionary alloc] init];
    [options setObject:pass forKey:(id)kSecImportExportPassphrase];
    CFArrayRef items = CFArrayCreate(NULL, 0, 0, NULL);
    OSStatus securityError = SecPKCS12Import((CFDataRef) certData,
                                             (CFDictionaryRef)options, &items);
    CFDictionaryRef identityDict = CFArrayGetValueAtIndex(items, 0);
    SecIdentityRef identityApp =
    (SecIdentityRef)CFDictionaryGetValue(identityDict,
                                         kSecImportItemIdentity);
    assert(securityError == noErr);
    //get private key
    SecIdentityCopyPrivateKey(identityApp, &privateKey);
    //get certificate
    SecIdentityCopyCertificate(identityApp, &certRef);
    //evaluate certificate.
    CFArrayRef certs = CFArrayCreate(kCFAllocatorDefault, (const void **) &certRef, 1, NULL);
    SecPolicyRef policy = SecPolicyCreateBasicX509();
    SecTrustRef trust;
    SecTrustCreateWithCertificates(certs, policy, &trust);
    (CFRelease(certs));
    SecTrustResultType trustResult;
    SecTrustEvaluate(trust, &trustResult);
    //get publickey
    publicKey = SecTrustCopyPublicKey(trust);
    //clean memory
    (CFRelease(trust));
    (CFRelease(policy));
    if (!publicKey || !privateKey || !certRef) {
        return NO;
    } else {
        KeyData *details = [[KeyData alloc] init];
        details.publicKey = publicKey;
        details.privateKey = privateKey;
        details.certificate = certRef;
        details.fileData = certData;
        return YES;
    }
}

Answer 1

看起来你只需要使用SecKeyCopyExternalRepresentation：

/*!
    @function SecKeyCopyExternalRepresentation
    @abstract Create an external representation for the given key suitable for the key's type.
    @param key The key to be exported.
    @param error On error, will be populated with an error object describing the failure.
    See "Security Error Codes" (SecBase.h).
    @result A CFData representing the key in a format suitable for that key type.
    @discussion This function may fail if the key is not exportable (e.g., bound to a smart card or Secure Enclave).
    The format in which the key will be exported depends on the type of key:
    * kSecAttrKeyTypeRSA                 PKCS#1 format
    * kSecAttrKeyTypeECSECPrimeRandom    SEC1 format (www.secg.org)
 */
CFDataRef _Nullable SecKeyCopyExternalRepresentation(SecKeyRef key, CFErrorRef *error)

请注意，CFDataRef是桥接到NSData的免费电话，因此您可以轻松转换它们。

Answer 2

要导出 SEC 的私钥，您需要检索 SecKey 并将其转换为 base64（并将结果格式化为每行最多 64 个字符。这里是 Swift 5 代码：

var keyResult: CFTypeRef?
var statusCode = SecItemCopyMatching(attributes as CFDictionary, &keyResult)
if statusCode == noErr && keyResult != nil {
       if let privateKey = SecKeyCopyExternalRepresentation(keyResult as! SecKey, nil) as Data? {
            print("Private Key: ((privateKey.base64EncodedString()))")
       }
       return (keyResult as! SecKey)
}