[SOLVED] Neo4j - The client is unauthorized due to authentication failure

I'm currently running Neo4j version 3.4.9 on a Google Cloud VM instance and I'm having an authentication issue I can't resolve.

My Neo4j server is running fine in the cloud and I can access it directly using Neo4j browser. I have changed the default neo4j user password. I can also successfully query the Neo4j server from the GraphQL playground.

I've checked both the neo4j-driver and neo4jgraphql-js modules and they are both the latest versions. I have also checked my .env file and it has the correct username and password that matches the default neo4j user and the new password I changed to from the default.

I have tried running the Neo4j server without authentication by changing the dbms.security.auth_enabled setting to false in the neo4j.conf file but this hasn't helped.

I have also checked the Neo4j server logs and this is the error on the server side:

2020-07-21 17:59:48.830+0000 ERROR [o.n.b.t.TransportSelectionHandler] Fatal error occurred during protocol selection for connection: [id: 0x2434a10e, L:/10.154.0.2:7687 ! R:/86.151.231.207:63494] javax.net.ssl.SSLException: Received fatal alert: certificate_unknown
io.netty.handler.codec.DecoderException: javax.net.ssl.SSLException: Received fatal alert: certificate_unknown
    at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:459)
    at io.netty.handler.codec.ByteToMessageDecoder.channelInputClosed(ByteToMessageDecoder.java:392)
    at io.netty.handler.codec.ByteToMessageDecoder.channelInputClosed(ByteToMessageDecoder.java:359)
    at io.netty.handler.codec.ByteToMessageDecoder.channelInactive(ByteToMessageDecoder.java:342)
    at io.netty.handler.ssl.SslHandler.channelInactive(SslHandler.java:1028)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:245)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:231)
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelInactive(AbstractChannelHandlerContext.java:224)
    at io.netty.channel.ChannelInboundHandlerAdapter.channelInactive(ChannelInboundHandlerAdapter.java:75)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:245)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:231)
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelInactive(AbstractChannelHandlerContext.java:224)
    at io.netty.channel.DefaultChannelPipeline$HeadContext.channelInactive(DefaultChannelPipeline.java:1429)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:245)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:231)
    at io.netty.channel.DefaultChannelPipeline.fireChannelInactive(DefaultChannelPipeline.java:947)
    at io.netty.channel.AbstractChannel$AbstractUnsafe$8.run(AbstractChannel.java:822)
    at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163)
    at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:404)
    at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:309)
    at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884)
    at java.lang.Thread.run(Thread.java:748)
Caused by: javax.net.ssl.SSLException: Received fatal alert: certificate_unknown
    at sun.security.ssl.Alerts.getSSLException(Alerts.java:214)
    at sun.security.ssl.SSLEngineImpl.fatal(SSLEngineImpl.java:1667)
    at sun.security.ssl.SSLEngineImpl.fatal(SSLEngineImpl.java:1635)
    at sun.security.ssl.SSLEngineImpl.recvAlert(SSLEngineImpl.java:1801)
    at sun.security.ssl.SSLEngineImpl.readRecord(SSLEngineImpl.java:1090)
    at sun.security.ssl.SSLEngineImpl.readNetRecord(SSLEngineImpl.java:913)
    at sun.security.ssl.SSLEngineImpl.unwrap(SSLEngineImpl.java:783)
    at javax.net.ssl.SSLEngine.unwrap(SSLEngine.java:626)
    at io.netty.handler.ssl.SslHandler$SslEngineType$3.unwrap(SslHandler.java:294)
    at io.netty.handler.ssl.SslHandler.unwrap(SslHandler.java:1275)
    at io.netty.handler.ssl.SslHandler.decodeJdkCompatible(SslHandler.java:1177)
    at io.netty.handler.ssl.SslHandler.decode(SslHandler.java:1221)
    at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:489)
    at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:428)

This suggests a certificate error and so I have updated the config_dbms.connector.bolt.tls_level setting in the neo4j.conf file to OPTIONAL but I still get this error. I have also tried setting config_dbms.connector.bolt.tls_level to DISABLED but it doesn't solve the problem and creates lots of others!

One solution I have explored is setting up a certificate for the Neo4j server on GCP but according to this Neo4j guide here you can only do that with a server that has a must have a valid DNS address, which mine doesn't. I didn't specify a hostname on creation and with GCP you can't add one retrospectively.

The only other solution I can think of is to build a fresh VM instance on GCP with a hostname, set up the correct DNS records, get the certificate and point my application at the new Neo4j server.