I'm trying to access gmail emails using imap and the code is failing at the ssl handshake without showing me any errors. Really appreciate if anyone could please help with this. I've built this using xunit, .NET Core 2.1. I'm using MailKit Nuget
public GMailHandler(string mailServer, int port, bool ssl, string login, string password)
//mailServer = imap.gmail.com
//port = 993
//ssl = true
{
if (ssl)
Client.Connect(mailServer, port);
else
Client.Connect(mailServer, port);
Client.Authenticate(login, password);
Client.Inbox.Open(FolderAccess.ReadOnly);
}
Here's a copy & paste from the MailKit FAQ:
Q: Why do I get "MailKit.Security.SslHandshakeException: An error occurred while attempting to establish an SSL or TLS connection." when I try to Connect?
When you get an exception with that error message, it usually means that you are encountering
one of the following scenarios:
1. The mail server does not support SSL on the specified port.
There are 2 different ways to use SSL/TLS encryption with mail servers.
The first way is to enable SSL/TLS encryption immediately upon connecting to the
SMTP, POP3 or IMAP server. This method requires an "SSL port" because the standard
port defined for the protocol is meant for plain-text communication.
The second way is via a STARTTLS command (aka STLS for POP3) that is optionally
supported by the server.
Below is a table of the protocols supported by MailKit and the standard plain-text ports
(which either do not support any SSL/TLS encryption at all or only via the STARTTLS
command extension) and the SSL ports which require SSL/TLS encryption immediately upon a
successful connection to the remote host.
|Protocol|Standard Port|SSL Port|
|:------:|:-----------:|:------:|
| SMTP | 25 or 587 | 465 |
| POP3 | 110 | 995 |
| IMAP | 143 | 993 |
It is important to use the correct SecureSocketOptions for the port that you are connecting to.
If you are connecting to one of the standard ports above, you will need to use SecureSocketOptions.None,
SecureSocketOptions.StartTls or SecureSocketOptions.StartTlsWhenAvailable.
If you are connecting to one of the SSL ports, you will need to use SecureSocketOptions.SslOnConnect.
You could also try using SecureSocketOptions.Auto which works by choosing the appropriate option to use
by comparing the specified port to the ports in the above table.
2. The mail server that you are connecting to is using an expired (or otherwise untrusted) SSL certificate.
Often times, mail servers will use self-signed certificates instead of using a certificate that
has been signed by a trusted Certificate Authority. Another potential pitfall is when locally
installed anti-virus software replaces the certificate in order to scan web traffic for viruses.
When your system is unable to validate the mail server's certificate because it is not signed
by a known and trusted Certificate Authority, the above error will occur.
You can work around this problem by supplying a custom RemoteCertificateValidationCallback
and setting it on the client's ServerCertificateValidationCallback
property.
In the simplest example, you could do something like this (although I would strongly recommend against it in
production use):
using (var client = new SmtpClient ()) {
client.ServerCertificateValidationCallback = (s,c,h,e) => true;
client.Connect (hostName, port, SecureSocketOptions.Auto);
// ...
}
Most likely you'll want to instead compare the certificate's Thumbprint
property to a known value that you have verified at a prior date.
You could also use this callback to prompt the user (much like you have probably seen web browsers do)
as to whether or not the certificate should be trusted.
3. A Certificate Authority CRL server for one or more of the certificates in the chain is temporarily unavailable.
Most Certificate Authorities are probably pretty good at keeping their CRL and/or OCSP servers up 24/7, but occasionally
they do go down or are otherwise unreachable due to other network problems between you and the server. When this happens,
it becomes impossible to check the revocation status of one or more of the certificates in the chain.
To ignore revocation checks, you can set the
CheckCertificateRevocation
property of the IMAP, POP3 or SMTP client to false before you connect:
using (var client = new SmtpClient ()) {
client.CheckCertificateRevocation = false;
client.Connect (hostName, port, SecureSocketOptions.Auto);
// ...
}
4. The server does not support the same set of SSL/TLS protocols that the client is configured to use.
MailKit attempts to keep up with the latest security recommendations and so is continuously removing older SSL and TLS
protocols that are no longer considered secure from the default configuration. This often means that MailKit's SMTP,
POP3 and IMAP clients will fail to connect to servers that are still using older SSL and TLS protocols. Currently,
the SSL and TLS protocols that are not supported by default are: SSL v2.0, SSL v3.0, and TLS v1.0.
You can override MailKit's default set of supported
SSL and TLS protocols
by setting the value of the SslProtocols
property on your SMTP, POP3 or IMAP client.
For example:
using (var client = new SmtpClient ()) {
// Allow SSLv3.0 and all versions of TLS
client.SslProtocols = SslProtocols.Ssl3 | SslProtocols.Tls | SslProtocols.Tls11 | SslProtocols.Tls12 | SslProtocols.Tls13;
client.Connect ("smtp.gmail.com", 465, true);
// ...
}
await client.ConnectAsync(_emailConfig.SmtpServer, _emailConfig.Port, false);
just set the "useSsl" option to false in the client configuration
Disbaled Avast antivorus software .
This works for me
I solved a similar problem by going through the protocols. As a result, I found out that the MS Exchange server uses Tls 1.0 for backward compatibility. I explicitly set the protocol and the connection passed.
var client = new ImapClient();
client.SslProtocols = System.Security.Authentication.SslProtocols.Tls;
client.Connect("servername", 993, SecureSocketOptions.SslOnConnect);
Trying to get RabbitMQ wired up to play nice with TLS v1.2. Working with both a Java client and a .NET Core client. The Java client is working but the .NET one is pushing back. Here are my factory settings:
var factory = new ConnectionFactory
{
HostName = hostName,
VirtualHost = vHost,
UserName = username,
Password = password,
Port = 5671,
Ssl = {Enabled = true}
};
I’m getting this exception:
System.Security.Authentication.AuthenticationException: A call to SSPI failed, see inner exception.
---> Interop+OpenSsl+SslException: SSL Handshake failed with OpenSSL error - SSL_ERROR_SSL.
---> Interop+Crypto+OpenSslCryptographicException: error:1409442E:SSL routines:SSL3_READ_BYTES:tlsv1 alert protocol version
Looking at the very tail end of the exception message it appears that the TLS version might be old but I have the latest version of RabbitMQ installed – 4.1.1
Dug into the RabbitMQ source for the ConnectionFactory class but cannot find anything relating to setting the TLS version. In my Java app it works thusly: factory.useSslProtocol("TLSv1.2");
Saw in another SO thread that an old version of Erlang might be the cause but I have the latest version (8.1) installed.
Any pointers on where to look next?
UPDATE: Foound the way to set the TLS property:
factory.Ssl.Version = SslProtocols.Tls12;
But now I'm getting a System.Security.Authentication.AuthenticationException: The remote certificate is invalid exception.
this worked for me:
Ssl = new SslOption
{
Version = SslProtocols.Tls12,
Enabled = true,
}
I have a wcf service hosted in a console process.
Service endpoints creation is done through code, in the program.cs file using net tcp binding.
Client side creation of channel is done through code.
This setup works fine in local host. But if I host the service in other machine and if I try to connect to service from some other machine (client IP address is updated) then I get the below error.
System.ServiceModel.EndpointNotFoundException: Could not connect to net.tcp://10.10.1.1:8232/Service/. The connection attempt lasted for a time span of 00:00:00. TCP error code 10061: No connection could be made because the target machine actively refused it 10.10.1.1:8232. ---> System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it 10.10.1.1:8232
Note:
Other scenario => Service and client are running in same machine.
In the service host to add the service endpoint URL address was given as 127.0.0.1.
With this in the client side, if I specify the IP address of the same machine it could not able to connect to the service.
But if I specify localhost instead of 127.0.0.1 in service endpoint configuration, I am able to connect successfully to the service.
I'm not sure why it doesn't work with 127.0.0.1, but works with local host in same machine. Is this expected?
Even after the local host change i could not able to connect to the service present in other machine.
Any suggestions are welcome.
The ports are not blocked by firewall.
** Server side configuration through code **,
var tcpBinding = new NetTcpBinding(SecurityMode.None)
{
MaxBufferPoolSize = int.MaxValue,
MaxBufferSize = int.MaxValue,
MaxReceivedMessageSize = int.MaxValue,
ReaderQuotas =
{
MaxArrayLength = int.MaxValue,
MaxNameTableCharCount = int.MaxValue,
MaxStringContentLength = int.MaxValue,
MaxDepth = int.MaxValue,
MaxBytesPerRead = int.MaxValue
},
ReceiveTimeout = TimeSpan.MaxValue
};
var host = new ServiceHost(typeof(Service));
host.AddServiceEndpoint(typeof(IService), tcpBinding, "net.tcp://localhost:8232/Service/");
host.Open();
Console.ReadLine();
host.Close(); `
** Clinet side configuration **
string endPointAdress = "net.tcp://10.10.1.1:8232/Service";
var ServiceProxy = ChannelFactory.CreateChannel(
tcpBinding, new EndpointAddress(endPointAdress));
*/ tcp binding is same for both client and service.
Can this problem happen due to data contracts? But if it is it should not work for local host as well.
Please correct, if my understanding is wrong.
Solution
Changing the server configuration from
** net.tcp://127.0.0.1:8232/Service/ ** to ** net.tcp://localhost:8232/Service/ **
seems to fix the problem. And the mentioned solution may be helpful to some one. May be some one can help why is this? Thanks all.
I have a server app and sometimes, when the client tries to connect, I get the following error:
NOTE: the "couldn't get stream from client or login failed" is a text that's added by me in catch statement
and the line at which it stops ( sThread : line 96 ) is :
tcpClient = (TcpClient)client;
clientStream = tcpClient.GetStream();
sr = new StreamReader(clientStream);
sw = new StreamWriter(clientStream);
// line 96:
a = sr.ReadLine();
What may be causing this problem? Note that it doesn't happen all the time
I received this error when calling a web-service. The issue was also related to transport level security. I could call the web-service through a website project, but when reusing the same code in a test project I would get a WebException that contained this message. Adding the following line before making the call resolved the issue:
System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;
Edit
System.Net.ServicePointManager.SecurityProtocol - This property
selects the version of the Secure Sockets Layer (SSL) or Transport
Layer Security (TLS) protocol to use for new connections that use the
Secure Hypertext Transfer Protocol (HTTPS) scheme only; existing
connections are not changed.
I believe the SecurityProtocol configuration is important during the TLS handshake when selecting the protocol version.
TLS handshake - This protocol is used to exchange all the information required by both sides for the exchange of the actual application data by TLS.
ClientHello - A client sends a ClientHello message specifying the highest TLS protocol version it supports ...
ServerHello - The server responds with a ServerHello message, containing the chosen protocol version ... The chosen protocol version should be the highest that both the client and server support. For example, if the client supports TLS version 1.1 and the server supports version 1.2, version 1.1 should be selected; version 1.2 should not be selected.
This error usually means that the target machine is running, but the service that you're trying to connect to is not available. (Either it stopped, crashed, or is busy with another request.)
In English:
The connection to the machine (remote host/server/PC that the service runs at) was made but since the service was not available on that machine, the machine didn't know what to do with the request.
If the connection to the machine was not available, you'd see a different error. I forget what it is, but it's along the lines of "Service Unreachable" or "Unavailable".
Edit - added
It IS possible that this is being caused by a firewall blocking the port, but given that you say it's intermittent ("sometimes when the client tries to connect"), that's very unlikely. I didn't include that originally because I had ruled it out mentally before replying.
My specific case scenario was that the Azure app service had the minimum TLS version changed to 1.2
I don't know if that's the default from now on, but changing it back to 1.0 made it work.
You can access the setting inside "SSL Settings".
According to "Hans Vonn" replies.
Adding the following line before making the call resolved the issue:
System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;
After adding Security protocol and working fine but I have to add before every API call which is not healthy. I just upgrade .net framework version at least 4.6 and working as expected do not require to adding before every API call.
Not sure which of the fixes in these blog posts helped, but one of them sorted this issue for me ...
http://briancaos.wordpress.com/2012/07/06/unable-to-read-data-from-the-transport-connection-the-connection-was-closed/
The trick that helped me was to quit using a WebRequest and use a HttpWebRequest instead. The HttpWebRequest allows me to play with 3 important settings:
and
http://briancaos.wordpress.com/2012/06/15/an-existing-connection-was-forcibly-closed-by-the-remote-host/
STEP 1: Disable KeepAlive
STEP 2: Set ProtocolVersion to Version10
STEP 3: Limiting the number of service points
For those who may find this later, after .NET version 4.6, I was running into this problem as well.
Make sure that you check your web.config file for the following lines:
<compilation debug="true" targetFramework="4.5">
...
<httpRuntime targetFramework="4.5" />
If you are running 4.6.x or a higher version of .NET on the server, make sure you adjust these targetFramework values to match the version of the framework on your server. If your versions read less than 4.6.x, then I would recommend you upgrade .NET and use the newer version unless your code is dependent on an older version (which, in that case, you should consider updating it).
I changed the targetFrameworks to 4.7.2 and the problem disappeared:
<compilation debug="true" targetFramework="4.7.2">
...
<httpRuntime targetFramework="4.7.2" />
The newer frameworks sort this issue out by using the best protocol available and blocking insecure or obsolete ones. If the remote service you are trying to connect to or call is giving this error, it could be that they don't support the old protocols anymore.
Calls to HTTPS services from one of our servers were also throwing the "Unable to read data from the transport connection : An existing connection was forcibly closed" exception. HTTP service, though, worked fine. Used Wireshark to see that it was a TLS handshake Failure. Ended up being that the cipher suite on the server needed to be updated.
This solved my problem. I added this line before the request is made:
System.Net.ServicePointManager.Expect100Continue = false;
It seemed there were a proxy in the way of the server that not supported 100-continue behavior.
This won't help for intermittent issues, but may be useful for other people with a similar problem.
I had cloned a VM and started it up on a different network with a new IP address but not changed the bindings in IIS. Fiddler was showing me "Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host" and IE was telling me "Turn on TLS 1.0, TLS 1.1, and TLS 1.2 in Advanced settings". Changing the binding to the new IP address solved it for me.
For some reason, the connection to the server was lost. It could be that the server explicitly closed the connection, or a bug on the server caused it to be closed unexpectedly. Or something between the client and the server (a switch or router) dropped the connection.
It might be server code that caused the problem, and it might not be. If you have access to the server code, you can put some debugging in there to tell you when client connections are closed. That might give you some indication of when and why connections are being dropped.
On the client, you have to write your code to take into account the possibility of the server failing at any time. That's just the way it is: network connections are inherently unreliable.
I was sending the HttpWebRequest from Console App, and UserAgent was
null by (default), so setting UserAgent worked along with setting
SecurityProtocol.
Should set SecurityProtocol before creating HttpWebRequest.
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls;
HttpWebRequest req = (HttpWebRequest)WebRequest.Create("yourpostURL");
req.UserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/93.0.4577.63 Safari/537.36";
The webrequest user agent is null by default. Just google "block empty user agent" and you'll find a strong desire of many web server admins to do just that.
Sending my request with
request.UserAgent = "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:50.0) Gecko/20100101 Firefox/50.0";
fixed the issue.
I get that problem in the past. I'm using PostgreSQL and when I run my program, sometimes it connects and sometimes it throws an error like that.
When I experiment with my code, I put my Connection code at the very first line below the public Form. Here is an example:
BEFORE:
public Form1()
{
//HERE LIES SOME CODES FOR RESIZING MY CONTROLS DURING RUNTIME
//CODE
//CODE AGAIN
//ANOTHER CODE
//CODE NA NAMAN
//CODE PA RIN!
//Connect to Database to generate auto number
NpgsqlConnection iConnect = new NpgsqlConnection("Server=localhost;Port=5432;User ID=postgres;Password=pass;Database=DB");
iConnect.Open();
NpgsqlCommand iQuery = new NpgsqlCommand("Select * from table1", iConnect);
NpgsqlDataReader iRead = iQuery.ExecuteReader();
NpgsqlDataAdapter iAdapter = new NpgsqlDataAdapter(iQuery);
DataSet iDataSet = new DataSet();
iAdapter.Fill(iDataSet, "ID");
MessageBox.Show(iDataSet.Tables["ID"].Rows.Count.ToString());
}
NOW:
public Form1()
{
//Connect to Database to generate auto number
NpgsqlConnection iConnect = new NpgsqlConnection("Server=localhost;Port=5432;User ID=postgres;Password=pass;Database=DB");
iConnect.Open();
NpgsqlCommand iQuery = new NpgsqlCommand("Select * from table1", iConnect);
NpgsqlDataReader iRead = iQuery.ExecuteReader();
NpgsqlDataAdapter iAdapter = new NpgsqlDataAdapter(iQuery);
DataSet iDataSet = new DataSet();
iAdapter.Fill(iDataSet, "ID");
MessageBox.Show(iDataSet.Tables["ID"].Rows.Count.ToString());
//HERE LIES SOME CODES FOR RESIZING MY CONTROLS DURING RUNTIME
//CODE
//CODE AGAIN
//ANOTHER CODE
//CODE NA NAMAN
//CODE PA RIN!
}
I think that the program must read first the connection before doing anything, I don't know, correct me if I'm wrong. But according to my research, it's not a code problem - it was actually from the machine itself.
System.Net.ServicePointManager.Expect100Continue = false;
This issue sometime occurs due the reason of proxy server implemented on web server. To bypass the proxy server by putting this line before calling the send service.
We had a very similar issue whereby a client's website was trying to connect to our Web API service and getting that same message. This started happening completely out of the blue when there had been no code changes or Windows updates on the server where IIS was running.
In our case it turned out that the calling website was using a version of .Net that only supported TLS 1.0 and for some reason the server where our IIS was running stopped appeared to have stopped accepting TLS 1.0 calls. To diagnose that we had to explicitly enable TLS via the registry on the IIS's server and then restart that server. These are the reg keys:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS
1.0\Client] "DisabledByDefault"=dword:00000000 "Enabled"=dword:00000001
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS
1.0\Server] "DisabledByDefault"=dword:00000000 "Enabled"=dword:00000001
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS
1.1\Client] "DisabledByDefault"=dword:00000000 "Enabled"=dword:00000001
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS
1.1\Server] "DisabledByDefault"=dword:00000000 "Enabled"=dword:00000001
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS
1.2\Client] "DisabledByDefault"=dword:00000000 "Enabled"=dword:00000001
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS
1.2\Server] "DisabledByDefault"=dword:00000000 "Enabled"=dword:00000001
If that doesn't do it, you could also experiment with adding the entry for SSL 2.0:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\SSL 2.0\Client]
"DisabledByDefault"=dword:00000000
"Enabled"=dword:00000001
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\SSL 2.0\Server]
"DisabledByDefault"=dword:00000000
"Enabled"=dword:00000001
My answer to another question here has this powershell script that we used to add the entries:
NOTE: Enabling old security protocols is not a good idea, the right answer in our case was to get the client website to update it's code to use TLS 1.2, but the registry entries above can help diagnose the issue in the first place.
The reason this was happening to me was I had a recursive dependency in my DI provider. In my case I had:
services.AddScoped(provider => new CfDbContext(builder.Options));
services.AddScoped(provider => provider.GetService<CfDbContext>());
Fix was to just remove the second scoped service registration
services.AddScoped(provider => new CfDbContext(builder.Options));
Had a similar problem and was getting the following errors depending on what app I used and if we bypassed the firewall / load balancer or not:
HTTPS handshake to [blah] (for #136) failed.
System.IO.IOException Unable to read data from the transport
connection: An existing connection was forcibly closed by the remote
host
and
ReadResponse() failed: The server did not return a complete response for this request. Server returned 0 bytes.
The problem turned out to be that the SSL Server Certificate got missed and wasn't installed on a couple servers.
For me, It was an issue where in the IIS binding it had the IP address of the web server.
I changed it to use all unassigned IPs and my application started to work.
I experienced the error with python clr running mdx query to Microsoft analytic services using adomd
I solved it with help of Hans Vonn and here is the python version:
clr.AddReference("System.Net")
from System.Net import ServicePointManager, SecurityProtocolType
ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls
I received this error simply because I was attempting to make an http connection to an https-only server. Changing the request protocol in the URI from http to https thus resolved it.
This is how I solved the issue:
int i = 0;
while (stream.DataAvailable == true)
{
bytes[i] = ((byte)stream.ReadByte());
i++;
}
data = System.Text.Encoding.ASCII.GetString(bytes, 0, i);
Console.WriteLine("Received: {0}", data);
I had a Third Party application (Fiddler) running to try and see the requests being sent. Closing this application fixed it for me
If you have a https certificate on the domain, make sure you have the https binding to the domain name in IIS.
In IIS -> Select your domain -> Click on Bindings
Site Bindings Window opens up. Add a binding for https.
Try checking if you can establish handshake in the first place. I had this issue before when uploading a file and I only figured out that the issue was the nonexistent route when I removed the upload and checked if it can login given the parameters.
Another option would be to check the error code generated using try-catch block and first catching a WebException.
In my case, the error code was "SendFailure" because of certificate issue on HTTPS url, once I hit HTTP, that got resolved.
https://learn.microsoft.com/en-us/dotnet/api/system.net.webexceptionstatus?redirectedfrom=MSDN&view=netframework-4.8
This problem occurring when the Service is Unavailable within the proxy server. We can bypass the proxy server.
Before start, the service, apply this code line.
System.Net.ServicePointManager.Expect100Continue = false;
Further details
In my case I resolved this problem setting a correct API's url in my application.
It was an error connection between the application and API.
I am getting a timeout exception when trying to use a net tcp endpoint through code
that has no security and is streamed like so:
NetTcpBinding binding = new NetTcpBinding(SecurityMode.None);
binding.TransferMode = TransferMode.Streamed;
binding.SendTimeout = TimeSpan.MaxValue;
the same code would work if i just leave out the SecurityMode.None or choose SecurityMode.Transport, the exception is on a timeout that is too low, i tired adding all the timeouts for recive, send, open, close and set them all to Max and that didnt work.
im using sample code from:
http://csharp-codesamples.com/2009/02/data-transfer-using-self-hosted-wcf-service/
Any explenation as to how to use no security in this scenario would be appriciated.
Thanks,
Totem
Sometimes WCF gives the wrong error message.
Only some security modes work when you are using streaming. You cannot sign a message, when you do not know how long it is.
Transport security mode works and is default, therefore it works when you do not specify the transport mode.
http://msdn.microsoft.com/en-us/library/ms731316.aspx