将私钥（SecRefKey）转换为 NSData 或 Base64

Question

我有一个 p12 文件，从中提取 PrivateKey、PublicKey 作为 SecKeyRef 和作为 SecCertificateRef 的证书。

P12 文件有一个 ECDSA PrivateKey，我需要用它来签署数据 (ECC)。

所以我使用了一个建议的库： https : //github.com/ricmoo/GMEllipticCurveCrypto

但是我需要用 Base64 或 NSData 上的密钥提供库，我无法提供 SecKeyRef。 我设法使用此处提供的方法为 publicKey 提取 NSData，它有效。

但是我找不到任何方法将指向私有密钥的 SecRefKey 转换为 NSData。 关于如何做到这一点的任何想法，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是免费桥接到NSData ，因此您可以轻松地转换它们。

Answer 2

要为 SEC 导出私钥，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)
}