EF Core SqlServer connect hang

[oguzhantopcu]

Describe the bug

Can not able to connect SQL Server instance. No exceptions, it just hangs at 'OpenConnection' function indefinitely. Even though I give 10 seconds of timeout, it does not timeout.

No exceptions. Just logs. Trace enabled.

May 13 09:08:46 ubuntu pompa-proxy[4071]: dbug: Microsoft.EntityFrameworkCore.Infrastructure[10401]
May 13 09:08:46 ubuntu pompa-proxy[4071]:       An 'IServiceProvider' was created for internal use by Entity Framework.
May 13 09:08:52 ubuntu pompa-proxy[4071]: info: Microsoft.EntityFrameworkCore.Infrastructure[10403]
May 13 09:08:52 ubuntu pompa-proxy[4071]:       Entity Framework Core 3.1.4 initialized 'OrkaContext' using provider 'Microsoft.EntityFrameworkCore.SqlServer' with options: CommandTimeout=10
May 13 09:08:52 ubuntu pompa-proxy[4071]: dbug: Microsoft.EntityFrameworkCore.Database.Connection[20000]
May 13 09:08:52 ubuntu pompa-proxy[4071]:       Opening connection to database 'ORKA_0996_2020' on server '192.168.0.250\ORKASQL'.

To reproduce

                var context = _serviceLocator.GetInstance<OrkaContext>();
                
                context.Database.OpenConnection();

                _logger.LogInformation("Execution is starting...");

                context.Database.ExecuteSqlRaw(@"...

Expected behavior

A connection should be opened or an exception should be thrown.

Further technical details

Microsoft.Data.SqlClient version: 3.1.4
.NET target: .NET Core 3.1.4
SQL Server version: SQL Server 2012 SP4
Operating system: Ubuntu 20.04 (Client) , Windows Server 2012 (Server)

Additional context
It was working until I have upgraded my ubuntu. At first, I got an SSL exception. I have upgraded the SQL server to SP4 to resolve issue, it did solve problem. but hang problem started.

I can connect to the database from the server's itself by sql server management studio using sql server authentication.
There are windows computers in the office, I can confirm they can connect to the sql server, too.

[oguzhantopcu]

I have following logs in the servers event logs.

It looks like there is a problem at the server side, too.

[oguzhantopcu]

I have resolved my issue by setting MinProtocol = TLSv1.1 at openssl.cnf. BTW MinProtocol = TLSv1.0 did not work, that was the main reason I have struggled with this issue for hours.

But I think infinite hang should be solved. It is up to you.

[cheenamalhotra]

@oguzhantopcu

It really depends on what TLS protocols are mutually supported by Client and Server. Many Linux Clients and Docker images are now removing support for TLS 1.1 and 1.0 by default and TLS 1.2 is set as default. You can either update your SQL Server 2012 to accept/work with TLS 1.2 protocol or modify client to work with TLS 1.1.

But I agree, the hang issue needs a fix, it is known to us and is tracked in #126 so I'll close this as duplicate.

[oguzhantopcu]

Today, I have failed to connect Sql Server 2016. Same exact scenario again, it has broken after ubuntu 20.04 update. There is something wrong here. Sql server 2016 should not have TLS version issues. Again I have downgraded TLS version to v1.1 to make it work.

@cheenamalhotra FYI.

[cheenamalhotra]

You would need to check if your server is accepting TLS 1.2 connections or not, it doesn't seem to do so. If your server does not yet support TLS 1.2 or you have manually disabled it using Registry entries on host machines, you'd notice this behavior.

I'll once again say, you should consider "Updating SQL Servers and Enabling TLS 1.2" as first solution, for enhanced security as TLS 1.1 and 1.0 are declared insecure and not recommended for server-client communication.

[oguzhantopcu]

Unfortunately those are customer machines which I can not free to update/alter settings everytime. AFAIK Sql Server 2016 has TLS 1.2 support by default. That is why I have concerned. And unfortunately the only thing I have about this server is sql login, so i can not check the registry to see whether 1.2 is disabled. Another thing, I had chance to examine the situation on previous machine which has Sql Server 2012 SP4. SP4 has tls 1.2 support, and as I checked the registry on the machine, TLS 1.2 was enabled. 14 May 2020 Per, saat 18:57 tarihinde Cheena Malhotra < notifications@github.com> şunu yazdı:

You would need to check if your server is accepting TLS 1.2 connections or not, it doesn't seem to do so. If your server does not yet support TLS 1.2 or you have manually disabled it using Registry entries on host machines, you'd notice this behavior. I'll once again say, you should consider "Updating SQL Servers and Enabling TLS 1.2" as first solution, for enhanced security as TLS 1.1 and 1.0 are declared insecure and not recommended for server-client communication. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#562 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAWRXBXOFQNO3NDHLR3EIBDRRQIGJANCNFSM4M7SPB4Q> .

-- oguzhan

[cheenamalhotra]

Could you also check if server certificate is not encrypted with SHA1?
Related issue was also reported here: #538 (comment)