在做超理论坛app的过程中，遇到许多用户反馈在他们的手机上客户端不能访问网络，我问了他们的手机型号和Android系统版本，全部是5.0以下的，之后我自己运行API19（4.4）的Android模拟器，也遇到了同样的错误。
错误信息如下：
javax.net.ssl.SSLHandshakeException: javax.net.ssl.SSLProtocolException: SSL handshake aborted: ssl=0x79f145b0: Failure in SSL library, usually a protocol errorerror:1407742E:SSL routines:SSL23_GET_SERVER_HELLO:tlsv1 alert protocol version
因为之前没有太多接触过网络协议，这个问题也确实很难搜到，所以我找了很久，才找到了原因：Android 4.4及以下的系统默认不支持TLS协议，所以遇到使用TLS协议的网站就无法访问了。
解决方法如下：创建一个SSLSocketFactoryCompat.java文件，内容如下：
import java.io.IOException;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import java.security.GeneralSecurityException;
import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocket;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.X509TrustManager;
public class SSLSocketFactoryCompat extends SSLSocketFactory {
private SSLSocketFactory defaultFactory;
// Android 5.0+ (API level21) provides reasonable default settings
// but it still allows SSLv3
// https://developer.android.com/about/versions/android-5.0-changes.html#ssl
static String protocols[] = null, cipherSuites[] = null;
static {
try {
SSLSocket socket = (SSLSocket)SSLSocketFactory.getDefault().createSocket();
if (socket != null) {
/* set reasonable protocol versions */
// - enable all supported protocols (enables TLSv1.1 and TLSv1.2 on Android <5.0)
// - remove all SSL versions (especially SSLv3) because they're insecure now
List<String> protocols = new LinkedList<>();
for (String protocol : socket.getSupportedProtocols())
if (!protocol.toUpperCase().contains("SSL"))
protocols.add(protocol);
SSLSocketFactoryCompat.protocols = protocols.toArray(new String[protocols.size()]);
/* set up reasonable cipher suites */
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
// choose known secure cipher suites
List<String> allowedCiphers = Arrays.asList(
// TLS 1.2
"TLS_RSA_WITH_AES_256_GCM_SHA384",
"TLS_RSA_WITH_AES_128_GCM_SHA256",
"TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256",
"TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256",
"TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384",
"TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256",
"TLS_ECHDE_RSA_WITH_AES_128_GCM_SHA256",
// maximum interoperability
"TLS_RSA_WITH_3DES_EDE_CBC_SHA",
"TLS_RSA_WITH_AES_128_CBC_SHA",
// additionally
"TLS_RSA_WITH_AES_256_CBC_SHA",
"TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA",
"TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA",
"TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA",
"TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA");
List<String> availableCiphers = Arrays.asList(socket.getSupportedCipherSuites());
// take all allowed ciphers that are available and put them into preferredCiphers
HashSet<String> preferredCiphers = new HashSet<>(allowedCiphers);
preferredCiphers.retainAll(availableCiphers);
/* For maximum security, preferredCiphers should *replace* enabled ciphers (thus disabling
* ciphers which are enabled by default, but have become unsecure), but I guess for
* the security level of DAVdroid and maximum compatibility, disabling of insecure
* ciphers should be a server-side task */
// add preferred ciphers to enabled ciphers
HashSet<String> enabledCiphers = preferredCiphers;
enabledCiphers.addAll(new HashSet<>(Arrays.asList(socket.getEnabledCipherSuites())));
SSLSocketFactoryCompat.cipherSuites = enabledCiphers.toArray(new String[enabledCiphers.size()]);
}
}
} catch (IOException e) {
throw new RuntimeException(e);
}
}
public SSLSocketFactoryCompat(X509TrustManager tm) {
try {
SSLContext sslContext = SSLContext.getInstance("TLS");
sslContext.init(null, (tm != null) ? new X509TrustManager[] { tm } : null, null);
defaultFactory = sslContext.getSocketFactory();
} catch (GeneralSecurityException e) {
throw new AssertionError(); // The system has no TLS. Just give up.
}
}
private void upgradeTLS(SSLSocket ssl) {
// Android 5.0+ (API level21) provides reasonable default settings
// but it still allows SSLv3
// https://developer.android.com/about/versions/android-5.0-changes.html#ssl
if (protocols != null) {
ssl.setEnabledProtocols(protocols);
}
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP && cipherSuites != null) {
ssl.setEnabledCipherSuites(cipherSuites);
}
}
@Override
public String[] getDefaultCipherSuites() {
return cipherSuites;
}
@Override
public String[] getSupportedCipherSuites() {
return cipherSuites;
}
@Override
public Socket createSocket(Socket s, String host, int port, boolean autoClose) throws IOException {
Socket ssl = defaultFactory.createSocket(s, host, port, autoClose);
if (ssl instanceof SSLSocket)
upgradeTLS((SSLSocket)ssl);
return ssl;
}
@Override
public Socket createSocket(String host, int port) throws IOException, UnknownHostException {
Socket ssl = defaultFactory.createSocket(host, port);
if (ssl instanceof SSLSocket)
upgradeTLS((SSLSocket)ssl);
return ssl;
}
@Override
public Socket createSocket(String host, int port, InetAddress localHost, int localPort) throws IOException, UnknownHostException {
Socket ssl = defaultFactory.createSocket(host, port, localHost, localPort);
if (ssl instanceof SSLSocket)
upgradeTLS((SSLSocket)ssl);
return ssl;
}
@Override
public Socket createSocket(InetAddress host, int port) throws IOException {
Socket ssl = defaultFactory.createSocket(host, port);
if (ssl instanceof SSLSocket)
upgradeTLS((SSLSocket)ssl);
return ssl;
}
@Override
public Socket createSocket(InetAddress address, int port, InetAddress localAddress, int localPort) throws IOException {
Socket ssl = defaultFactory.createSocket(address, port, localAddress, localPort);
if (ssl instanceof SSLSocket)
upgradeTLS((SSLSocket)ssl);
return ssl;
}
}
这样就可以解决了～
不知道如果用别人在OkHttp基础上封装好的工具类，比如okhttp-utils还会不会有这个问题，不过我在使用OkHttp之前，是用AsyncHttpClient做网络库的，因为它已经太老而过时所以换到了OkHttp，在使用AsyncHttpClient的时候也遇到了这个问题
