Android SSLSocketFactory for use with custom CA

CustomSSLSocketFactory.java

package com.github.aurae.ssl;

import android.content.Context;
import android.support.annotation.RawRes;

import java.io.IOException;
import java.io.InputStream;
import java.security.KeyStore;
import java.security.SecureRandom;
import java.security.cert.Certificate;
import java.security.cert.CertificateFactory;

import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManagerFactory;

/**
 * Creates an SSLSocketFactory instance for use with a custom CA, which would otherwise be considered "not trustworthy".
 * This can be fed into HttpsURLConnection, as well as networking libraries such as OkHttp's OkHttpClient.
 */
public final class CustomSSLSocketFactory {

	private CustomSSLSocketFactory() {
		throw new AssertionError();
	}

	/**
	 * Creates an SSLSocketFactory instance for use with the CA provided in the resource file.
	 * 
	 * @param context 	Context used to open up the CA file
	 * @param caRawFile	Raw resource file to the CA (in .crt or .cer format, for instance)
	 * @return An SSLSocketFactory which trusts the provided CA when provided to network clients
	 */
	public static SSLSocketFactory create(Context context, @RawRes int caRawFile) {
		InputStream caInput = null;
		try {
			// Generate the CA Certificate from the raw resource file
			caInput = context.getResources().openRawResource(caRawFile);
			Certificate ca = CertificateFactory.getInstance("X.509").generateCertificate(caInput);

			// Load the key store using the CA
			KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
			keyStore.load(null, null);
			keyStore.setCertificateEntry("ca", ca);

			// Initialize the TrustManager with this CA
			TrustManagerFactory tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
			tmf.init(keyStore);

			// Create an SSL context that uses the created trust manager
			SSLContext sslContext = SSLContext.getInstance("TLS");
			sslContext.init(null, tmf.getTrustManagers(), new SecureRandom());
			return sslContext.getSocketFactory();

		} catch (Exception ex) {
			throw new RuntimeException(ex);

		} finally {
			if (caInput != null) {
				try {
					caInput.close();
				} catch (IOException ignored) {
				}
			}
		}
	}
}