1. 背景：Android Studio中 Gradle 同步拉取library信息失败
2022-12-14T17:13:14.916+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] Caused by: javax.net.ssl.SSLHandshakeException: Received fatal alert: handshake_failure
2022-12-14T17:13:14.916+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] at org.apache.http.conn.ssl.SSLConnectionSocketFactory.createLayeredSocket(SSLConnectionSocketFactory.java:436)
2022-12-14T17:13:14.916+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] at org.apache.http.conn.ssl.SSLConnectionSocketFactory.connectSocket(SSLConnectionSocketFactory.java:384)
2022-12-14T17:13:14.916+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java:142)
2022-12-14T17:13:14.916+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.connect(PoolingHttpClientConnectionManager.java:374)
2022-12-14T17:13:14.916+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] at org.apache.http.impl.execchain.MainClientExec.establishRoute(MainClientExec.java:393)
2022-12-14T17:13:14.917+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:236)
2022-12-14T17:13:14.917+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:186)
2022-12-14T17:13:14.917+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89)
2022-12-14T17:13:14.917+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110)
2022-12-14T17:13:14.917+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
2022-12-14T17:13:14.917+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83)
2022-12-14T17:13:14.917+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] at org.gradle.internal.resource.transport.http.HttpClientHelper.performHttpRequest(HttpClientHelper.java:141)
2022-12-14T17:13:14.917+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] at org.gradle.internal.resource.transport.http.HttpClientHelper.performHttpRequest(HttpClientHelper.java:121)
2022-12-14T17:13:14.918+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] at org.gradle.internal.resource.transport.http.HttpClientHelper.executeGetOrHead(HttpClientHelper.java:106)
2022-12-14T17:13:14.918+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] at org.gradle.internal.resource.transport.http.HttpClientHelper.performRequest(HttpClientHelper.java:97)
2022-12-14T17:13:14.919+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] ... 50 more
Daemon worker: released lock on root.1
2022-12-14T17:13:14.860+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter]
2022-12-14T17:13:14.862+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] FAILURE: Build failed with an exception.
2022-12-14T17:13:14.863+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter]
2022-12-14T17:13:14.863+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] * What went wrong:
2022-12-14T17:13:14.864+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] Could not determine the dependencies of task ':app:compileJunoUatDebugKotlin'.
2022-12-14T17:13:14.867+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] > Could not resolve all files for configuration ':app:googleplayUatDebugRuntimeClasspath'.
2022-12-14T17:13:14.867+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] > Could not download base-1.1.2-SNAPSHOT.aar (com.your.pkg:base:1.1.2-SNAPSHOT:20210628.100523-1)
2022-12-14T17:13:14.867+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] > Could not get resource 'https://nexus3.***.io/repository/maven-mobile-snapshots/com/your/pkg/base/1.1.2-SNAPSHOT/base-1.1.2-20210628.100523-1.aar'.
2022-12-14T17:13:14.868+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] > Could not HEAD 'https://nexus3.***.io/repository/maven-mobile-snapshots/com/your/pkg/base/1.1.2-SNAPSHOT/base-1.1.2-20210628.100523-1.aar'.
2022-12-14T17:13:14.868+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] > Received fatal alert: handshake_failure
2022-12-14T17:13:14.868+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter]
2022-12-14T17:13:14.868+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] * Try:
2022-12-14T17:13:14.868+0800 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] Run with --scan to get full insights.
2. 查看nexus服务器支持的tls 版本以及客户端的设置
经过在网上搜索，有一些线索。Https握手阶段失败，最直接的想法💡是 客户端与服务器 TLS 版本协商失败。重新看了下客户端JDK的版本已经是JDK11，再 分析 下 nexus 服务器上支持的协议，看到并不存在它所提到的问题。
3. 工具分析
通过 openssl 命令 openssl s_client -connect nexus3.***.io:443 [-servername nexus3.***.io] （带或不带 参数servername）的结果来看, 服务器端是否支持 SNI，即它存在多台虚拟主机，可以根据客户端请求中不同的host，将请求分发给不同的域名（虚拟主机）来处理。
注意到 JDK 1.8中 参数 jsse.enableSNIExtension 默认值为 true。
于是在AS 项目中附加了参数 -Djsse.enableSNIExtension=true 到 org.gradle.jvmargs中。操作完成后重试，发现本地编译偶有成功，但问题依旧存在。
可以使用openssl s_client和不使用-servername选项：
without SNI
$ openssl s_client -connect host:port
use SNI
$ openssl s_client -connect host:port -servername host
如果你获得两个同名的不同证书，则表示支持并正确配置了 SNI。
但是，如果返回的证书中的输出不同，或者没有SNI的调用无法建立SSL连接，则表明需要SNI但没有正确配置。解决此问题可能需要切换到专用 IP 地址。
此时发现 不带 -servername 的命令返回的结果确实是有问题的：
> openssl s_client -connect nexus3.***.io:443 -tlsextdebug
CONNECTED(00000006)
140704677139648:error:1404B410:SSL routines:ST_CONNECT:sslv3 alert handshake failure:/AppleInternal/Library/BuildRoots/810eba08-405a-11ed-86e9-6af958a02716/Library/Caches/com.apple.xbs/Sources/libressl/libressl-3.3/ssl/tls13_lib.c:129:SSL alert number 40
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 7 bytes and written 287 bytes
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
SSL-Session:
Protocol : TLSv1.3
Cipher : 0000
Session-ID:
Session-ID-ctx:
Master-Key:
Start Time: 1671086879
Timeout : 7200 (sec)
Verify return code: 0
4. 和SRE一起解决问题
于是找到公司的SRE同事一起来看，他建议断开cloud flare，设置本地host为固定IP地址后再尝试。果然Jenkins上的编译成功了。回头再看看服务器 不带 -servername 的返回，证书信息也有了。此刻真相大白了：上了cloud flare后 SNI的配置出现了问题！
5. 番外: regression ?!
又有一天看，其它业务组的同事也报出了相同的问题导致Jenkins上打包📦 出错。在升级 gradle 版本到6.8后，发现除了上面的错误外，还额外有一条错误信息是
[org.gradle.internal.buildevents.BuildExceptionReporter] >
The server may not support the client's requested TLS protocol versions: (TLSv1.2, TLSv1.3).
You may need to configure the client to allow other protocols to be used.
See: https://docs.gradle.org/6.8/userguide/build_environment.html#gradle_system_properties
这无疑之中让我想到除了在Jenkins 主机上抓网络数据包外，是不是还有其它办法可以看到更多HTTPS 握手阶段出错的更多细节呢？果然万能的SO给出类似问题的了一条很赞的回复[1], 在JVM中设置参数-Djavax.net.debug=all ，就可以调试 HTTP SSL/TLS 连接了。
在单独指定tls 版本为 TLSv1.3后，再看Jenkins上详细的log 输出:
The server does not support the client's requested TLS protocol versions: (TLSv1.3). You may need to configure the client to allow other protocols to be used. See: https://docs.gradle.org/6.8/userguide/build_environment.html#gradle_system_properties
Received fatal alert: protocol_version
......
[ERROR] [system.err] javax.net.ssl|DEBUG|24|Build operations Thread 2|2023-02-09 10:41:02.495 UTC|SSLSocketInputRecord.java:213|READ: TLSv1.2 alert, length = 2
[ERROR] [system.err] javax.net.ssl|DEBUG|24|Build operations Thread 2|2023-02-09 10:41:02.495 UTC|SSLSocketInputRecord.java:458|Raw read (
[ERROR] [system.err] 0000: 02 46 .F
[ERROR] [system.err] )
[ERROR] [system.err] javax.net.ssl|DEBUG|24|Build operations Thread 2|2023-02-09 10:41:02.495 UTC|SSLSocketInputRecord.java:249|READ: TLSv1.2 alert, length = 2
[ERROR] [system.err] javax.net.ssl|DEBUG|24|Build operations Thread 2|2023-02-09 10:41:02.496 UTC|Alert.java:232|Received alert message (
[ERROR] [system.err] "Alert": {
[ERROR] [system.err] "level" : "fatal",
[ERROR] [system.err] "description": "protocol_version"
[ERROR] [system.err] }
[ERROR] [system.err] )
[ERROR] [system.err] javax.net.ssl|ERROR|24|Build operations Thread 2|2023-02-09 10:41:02.497 UTC|TransportContext.java:313|Fatal (PROTOCOL_VERSION):
Received fatal alert: protocol_version
🆗 至此为止看判断是与服务端协商支持的tls 版本不一致导致的问题，将客户端的tls 版本设置为TLSv1.2后，再次尝试编译，果然就成功了🚀。
