以编程方式添加证书颁发机构，同时保留 Android 系统 SSL 证书

StackOverflow上有很多关于这个主题的问题，但我似乎没有找到与我的问题相关的问题。

我有一个需要与HTTPS服务器通信的Android应用程序：有些使用在Android系统密钥库（常见的HTTPS网站）中注册的CA签名，有些使用我拥有的CA签名，但不在Android系统密钥库中（例如具有自动签名证书的服务器）。

我知道如何以编程方式添加我的CA，并强制每个HTTPS连接使用它。我使用以下代码：

public class SslCertificateAuthority {

    public static void addCertificateAuthority(InputStream inputStream) {

        try {
            // Load CAs from an InputStream
            // (could be from a resource or ByteArrayInputStream or ...)
            CertificateFactory cf = CertificateFactory.getInstance("X.509");
            InputStream caInput = new BufferedInputStream(inputStream);
            Certificate ca;
            try {
                ca = cf.generateCertificate(caInput);
            } finally {
                caInput.close();
            }

            // Create a KeyStore containing our trusted CAs
            String keyStoreType = KeyStore.getDefaultType();
            KeyStore keyStore = KeyStore.getInstance(keyStoreType);
            keyStore.load(null, null);
            keyStore.setCertificateEntry("ca", ca);

            // Create a TrustManager that trusts the CAs in our KeyStore
            String tmfAlgorithm = TrustManagerFactory.getDefaultAlgorithm();
            TrustManagerFactory tmf = TrustManagerFactory.getInstance(tmfAlgorithm);
            tmf.init(keyStore);

            // Create an SSLContext that uses our TrustManager
            SSLContext context = SSLContext.getInstance("TLS");
            context.init(null, tmf.getTrustManagers(), null);

            // Tell the URLConnection to use a SocketFactory from our SSLContext
            HttpsURLConnection.setDefaultSSLSocketFactory(context.getSocketFactory());
        } catch (CertificateException e) {
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (KeyStoreException e) {
            e.printStackTrace();
        } catch (KeyManagementException e) {
            e.printStackTrace();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }  

    }

}

但是，这样做会禁用Android系统密钥库的使用，并且我无法再查询与其他CA签名的HTTPS站点。

我尝试在 Android 密钥库中添加我的 CA，使用：

KeyStore.getInstance("AndroidCAStore")

...但是我无法在其中添加我的CA（启动异常）。

我可以使用实例方法而不是静态全局来逐案告知何时必须使用我的 CA。HttpsURLConnection.setSSLSocketFactory(...)HttpsURLConnection.setDefaultSSLSocketFactory(...)

但它根本不实用，特别是因为有时我无法将预配置的对象传递给某些库。HttpsURLConnection

关于我如何做到这一点的一些想法？

编辑 - 回答

好的，按照给出的建议，这是我的工作代码。它可能需要一些增强功能，但它似乎可以作为起点。

public class SslCertificateAuthority {

    private static class UnifiedTrustManager implements X509TrustManager {
        private X509TrustManager defaultTrustManager;
        private X509TrustManager localTrustManager;
        public UnifiedTrustManager(KeyStore localKeyStore) throws KeyStoreException {
            try {
                this.defaultTrustManager = createTrustManager(null);
                this.localTrustManager = createTrustManager(localKeyStore);
            } catch (NoSuchAlgorithmException e) {
                e.printStackTrace();
            }
        }
        private X509TrustManager createTrustManager(KeyStore store) throws NoSuchAlgorithmException, KeyStoreException {
            String tmfAlgorithm = TrustManagerFactory.getDefaultAlgorithm();
            TrustManagerFactory tmf = TrustManagerFactory.getInstance(tmfAlgorithm);
            tmf.init((KeyStore) store);
            TrustManager[] trustManagers = tmf.getTrustManagers();
            return (X509TrustManager) trustManagers[0];
        }
        public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
            try {
                defaultTrustManager.checkServerTrusted(chain, authType);
            } catch (CertificateException ce) {
                localTrustManager.checkServerTrusted(chain, authType);
            }
        }
        @Override
        public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
            try {
                defaultTrustManager.checkClientTrusted(chain, authType);
            } catch (CertificateException ce) {
                localTrustManager.checkClientTrusted(chain, authType);
            }
        }
        @Override
        public X509Certificate[] getAcceptedIssuers() {
            X509Certificate[] first = defaultTrustManager.getAcceptedIssuers();
            X509Certificate[] second = localTrustManager.getAcceptedIssuers();
            X509Certificate[] result = Arrays.copyOf(first, first.length + second.length);
            System.arraycopy(second, 0, result, first.length, second.length);
            return result;
        }
    }

    public static void setCustomCertificateAuthority(InputStream inputStream) {

        try {
            // Load CAs from an InputStream
            // (could be from a resource or ByteArrayInputStream or ...)
            CertificateFactory cf = CertificateFactory.getInstance("X.509");
            InputStream caInput = new BufferedInputStream(inputStream);
            Certificate ca;
            try {
                ca = cf.generateCertificate(caInput);
                System.out.println("ca=" + ((X509Certificate) ca).getSubjectDN());
            } finally {
                caInput.close();
            }

            // Create a KeyStore containing our trusted CAs
            String keyStoreType = KeyStore.getDefaultType();
            KeyStore keyStore = KeyStore.getInstance(keyStoreType);
            keyStore.load(null, null);
            keyStore.setCertificateEntry("ca", ca);

            // Create a TrustManager that trusts the CAs in our KeyStore and system CA
            UnifiedTrustManager trustManager = new UnifiedTrustManager(keyStore);

            // Create an SSLContext that uses our TrustManager
            SSLContext context = SSLContext.getInstance("TLS");
            context.init(null, new TrustManager[]{trustManager}, null);

            // Tell the URLConnection to use a SocketFactory from our SSLContext
            HttpsURLConnection.setDefaultSSLSocketFactory(context.getSocketFactory());

        } catch (CertificateException e) {
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (KeyStoreException e) {
            e.printStackTrace();
        } catch (KeyManagementException e) {
            e.printStackTrace();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}