Frequently Asked Questions about Bitvise SSH Server
As an administrator of Bitvise SSH Server, you should first become comfortable with the SSH server's log files. Bitvise SSH Server writes warnings and errors into the Application section of the Windows Event Log, but it also writes more detailed information to textual log files. These are located by default in the 'Logs' subdirectory of the SSH server installation directory.
Whenever you have a problem, the SSH server log files are the first place you should look.
- Personal Edition
- Configuring and Running
- File Transfer
- Public Key Authentication
- Account Settings
- Usage Issues and Operation Concerns
- Upgrading and Moving
- Contacting Support
Q00. Where do I get an activation code for personal use?
No activation code is needed to use Bitvise SSH Server for personal use. If your Bitvise SSH Server Control Panel is saying that there is an evaluation period, this means that you installed the product as the Standard Edition. In this case, you need to uninstall Bitvise SSH Server, re-install it again, and choose the Personal Edition this time.
Note that Bitvise SSH Server may be installed in the Personal Edition only by genuine, non-commercial personal users who are not using the SSH server as part of a commercial endeavor, and are not using it in an organization, whether commercial or otherwise. All commercial or organizational use requires a purchased license.
Q01. How do I use Bitvise SSH Server Personal Edition on a domain controller?
The Personal Edition does not support domain accounts, and will not work on a domain controller. If you chose the Personal Edition during installation, you need to uninstall Bitvise SSH Server and then re-install it, this time selecting the Standard Edition. The Standard Edition requires a purchased license, and is not available free of charge for personal use.
Q02. What are the limitations of the Personal Edition?
The Bitvise SSH Server Personal Edition:
- Can use only local Windows accounts (no domains).
- Can configure only one Windows group ('everyone').
- Can configure only one virtual group.
- Has a limit of 10 Windows account entries.
- Has a limit of 10 virtual account entries.
- GSSAPI authentication is disabled (Kerberos and NTLM).
If you are trying to make a decision about whether to use the Personal or Standard Edition, please note that in most cases, this is not a technical decision. All organizations, as well as personal users who do not qualify as non-commercial, must purchase a license for the Standard Edition. The Personal Edition is available only for users who are both personal and non-commercial, and are therefore likely to be unaffected by the above limitations.
Configuring and Running
Q10. After I install Bitvise SSH Server, what do I need to configure before I can start using it?
For a basic, open setup, just start Bitvise SSH Server and it will work. Use one of your existing Windows account names and passwords to log on. For a basic usage case, where you want to use the SSH server for remote administration, the default server settings do not need to be changed. The one exception is the "Open Windows Firewall Setting", described in Q10B.
After you have established a successful connection, consider locking down your settings to prevent SSH access to Windows accounts and features that you do not want to be accessible over SSH. See the page Securing Bitvise SSH Server for more information.
Q10B. I can connect to Bitvise SSH Server from the local network, but not from the internet.
To help prevent inadvertently exposing your SSH server to the internet before it has been properly configured, Bitvise SSH Server will not open its ports to the internet by default. When you are ready to open your server to internet connections, go to Easy SSH server settings, and change the setting "Open Windows Firewall" to "Open port(s) to any computer". If your Windows Firewall is disabled, or if you prefer to manage it manually, change this setting to "Do not change Windows Firewall settings".
If you still cannot connect from the internet after making this change, make sure that your router is properly configured to forward SSH connections to the SSH server. You can configure the router directly through its administrative interface, or if the router can be managed using Universal Plug and Play, you can set Bitvise SSH Server to configure it. To let the SSH server manage the router, enable "Automatically configure router (requires UPnP)" in Easy SSH server settings.
Q10C. A client is able to establish a TCP connection to Bitvise SSH Server, but the session hangs before proceeding to user authentication; or else, the SSH connection fails at a later point, due to an error such as "data integrity failure". What could be causing this behavior?
Ensure that the MTU network setting (Maximal Transmission Unit) is set correctly on all devices involved in the TCP connection between the client and the server. Default MTU settings will work in most cases, but some ways of connecting to the internet require a lower MTU setting. In these cases, an MTU setting that's too large will result in segments of data being cut off, resulting in an inability of the client and the server to establish or maintain an SSH session.
Q11. How do I log in to a Windows domain account?
Specify the username in the standard domain, backslash, account format - for example, 'company\john' - or with a fully qualified name, for example 'email@example.com'. Alternately, add the domain name to the Domain Order setting.
Q11B. How do I log in to a Windows domain account without having to specify a fully qualified username?
The 'Domain order' setting in Advanced settings is provided for this purpose. Configure an entry specifying the domain name where you would like Bitvise SSH Server to start looking up unqualified usernames. You can configure multiple such domain names.
Q12. What client software can I use to connect to Bitvise SSH Server?
You can use any client program that supports SSH, as long as it implements SSH version 2 - the newer and secure version of the protocol. There are multiple types of SSH clients, including terminal session clients, file transfer clients, port forwarding clients, command execution clients, and they come in all sorts of combinations. If your client machine runs Windows, you can use Bitvise SSH Client for most purposes. Our SSH client offers an excellent terminal console, graphical file transfer, dynamic and manual port forwarding, as well as scriptable command-line clients and an FTP-to-SFTP bridge. Also available for Windows is PuTTY, which includes SSH file transfer programs 'pscp' and 'psftp'. On Unix platforms, the OpenSSH package is freely available and provides the 'ssh' program for terminal sessions and port forwarding, as well as 'scp' and 'sftp' for file transfers.
Q13. My Bitvise SSH Server logs show an error like 'Failed to bind listening socket', and I cannot connect to the server.
Such an error indicates that another application is already listening on the port you have configured for Bitvise SSH Server. The default port is 22, and this port is used as default by all SSH servers. It is likely that you already have another SSH server running on your machine, and that it is occupying port 22. You either need to shutdown the other SSH server, or configure Bitvise SSH Server to listen on a different port.
Q14. I can only log in with an administrator account - attempting to log in with a regular account fails.
There are two most common causes.
- You are trying to log in with an account configured in Bitvise SSH Server to use the 'interactive' logon type, but this account does not have the Windows permission to log on locally. On domain controllers, this permission is not granted to regular users by default and must be enabled in the Domain Controller Security Policy.
- You have successfully logged in with an account configured in Bitvise SSH Server to use the 'network' logon type, or you logged in using GSSAPI (Kerberos or NTLM) authentication, but starting the terminal shell failed with an Access Denied error. This is because default filesystem permissions on Windows 2003 servers grant access to cmd.exe and other command line tools only to 'interactive' users. Switch this user or group in Bitvise SSH Server to use the 'interactive' logon type, or modify filesystem permissions for cmd.exe and other command-line tools to allow execution by users logged in with the 'network' logon type.
For more information, please read the Network vs. interactive logon section in the Bitvise SSH Server Users' Guide.
Q15. I'm trying to get some SSH client to work with Bitvise SSH Server. However, the session gets terminated immediately after connecting, and the SSH server logs tell me: 'Unable to create child process: Access is denied.' What is going on?
In order to provide SFTP, SCP, terminal shell, or exec request functionality, Bitvise SSH Server must have permission from Windows to execute a child process in the name of the user. You have probably configured your machine in such a way that, when the user logs in and the SSH server starts impersonating that user, the server loses permission to execute the necessary child processes. In order to use Bitvise SSH Server, you must configure your machine so that the remote user will be able to run executables in the SSH server installation directory; plus, of course, whatever programs you want the user to be able to execute, such as the terminal shell - 'cmd.exe'. Read and execute access is also required to the dynamic load libraries that programs use - in particular, system libraries which reside in the \Windows and \Windows\System32 directories.
Q16. I'm trying to use PowerShell in a terminal session using the 'dumb' terminal type. It doesn't display a command prompt.
When PowerShell detects that its input or output streams have been redirected, it suppresses any prompts that it might normally display. If you want to host an interactive PowerShell prompt inside another application (such as Emacs), use "-" as the argument for the -File parameter. In many shells, this implies "taken from standard input."
powershell -File -
Thanks to Jim Snyder for discovering this solution.
Q17. An SSH client hangs for no apparent reason when connecting to Bitvise SSH Server, and then the session breaks due to an authentication timeout.
If the SSH client is set up to try Kerberos authentication, but Kerberos isn't configured properly between the client and the server, the client might hang when it tries to unsuccessfully figure out how to use Kerberos to authenticate with the server.
To rectify this behavior, you can disable GSSAPI (Kerberos) either in the SSH client, or in the SSH server.
To disable GSSAPI authentication in Bitvise SSH server, find the settings Kerberos 5 authentication and NTLM authentication on the Access control page of Advanced settings, and set them both to Disabled. Disabling both methods will disable GSSAPI authentication for all users. The server won't advertise the GSSAPI algorithms, and the client won't shoot itself in the foot trying to figure out how to authenticate using Kerberos.
Q18. How do I set up Bitvise SSH Server to use a different terminal shell, such as Windows PowerShell, or a Unix-style shell such as Bash?
The default terminal shell used by Bitvise SSH Server is the Windows Command Interpreter, cmd.exe, which is available on all Windows platforms. You can configure a different terminal shell in Advanced SSH Server settings, either individually for a particular user in their account settings entry, or for a group of users in their group settings entry. The two settings you must configure are as follows:
- Terminal shell: The command line to start your desired terminal shell interactively. For example:
"PowerShell.exe"for Windows PowerShell, or for Bash:
"c:\path\to\bash.exe -l"Quotation marks should not be included.
- Exec request prefix: The command line prefix to start a command with the shell non-interactively. For example:
"PowerShell.exe -Command "or for Bash:
"c:\path\to\bash.exe -c "Note the extra spaces at the end: these must be present to properly separate the exec request prefix from the command sent by the SSH client that is appended. Quotation marks should not be included.
To use a terminal shell that doesn't come with Windows, such as Bash, you will need to install it. You can obtain Bash from a variety of sources, such as Cygwin.
For Windows PowerShell, see also Question 16.
Q19. I would like to provide a user with access only to port forwarding, but the client disconnects unless I also allow terminal shell access.
Most clients can be configured to not require a terminal shell when using port forwarding:
- If using OpenSSH, use the "-T" parameter ("Disable pseudo-tty allocation").
- If using plink (part of PuTTY), use the "-N" parameter ("don't start a shell/command").
- If using the graphical PuTTY client, enable Connection > SSH > "Don't start a shell or command at all".
If using Bitvise SSH Client, the session won't be disconnected if a terminal window can't be opened, in the first place. However, if terminal shell and/or SFTP access are not available, you may want to disable the automatic opening of a terminal shell and/or SFTP window. This is configured under Options > On Login.
Q21. When users log in, they can see all drives on my server. How do I limit them to a certain directory?
If using Easy settings, you will need to use the "Virtual filesystem layout" setting under a Windows or virtual account settings entry. Configure this setting to "Limit to root directory", and then configure the Root directory. Alternately, select "Advanced filesystem layout", and you can configure multiple directories.
If using Advanced settings, this feature is configurable either per-account or per-group. When editing account or group settings, click "Virtual filesystem layout" in the configuration tree on the left side of the account or group settings window. If configuring settings for a specific user, as opposed to a group, disable the "Use default layout" checkbox. Edit Mount Points, and change the 'Real root path' setting for the default mount point (virtual mount path "/") to the directory you want the user to be able to access. The user or users will now be able to see only files and subdirectories in that folder.
If you want the user to be able to access multiple directories in independent locations, add additional mount points.
Note that the virtual filesystem limits will affect only users who log in through SFTP or SCP. Users who are allowed terminal shell access, and who access your SSH server this way, will still be able to see the entire filesystem that they are allowed to see based on their Windows filesystem permissions.If you want users to only have file transfer access, you should prevent them from using a terminal shell. See also Securing Bitvise SSH Server.
Q22. What is the difference between SCP and SFTP?
SCP and SFTP are different file transfer protocols. SFTP, despite its name, has no relation to FTP. It is a remote file access protocol which provides rich and fine-grained functionality for managing, accessing, and modifying files on an SSH server. SCP is an adaptation of the Unix utility 'rcp' to run over an SSH session, and provides simplistic file transfer operations only. SFTP is launched by the client opening a session channel and requesting the 'sftp' subsystem. SCP is launched by the client instructing the server to execute the SCP program via an SSH exec request.
In WinSSHD 4, the SCP subsystem was not supported as well as SFTP. Since Bitvise SSH Server 5, support for the two subsystems is integrated, and the same virtual filesystem can be accessed through SFTP or SCP.
Q23. How do I get WinSCP to work with Bitvise SSH Server?
All recent WinSCP versions work fine in SFTP mode. Very old WinSCP versions that only supported SCP can also be made to work if you install the Cygwin bash shell and Cygwin's SCP, and configure the bash shell to be used in the SSH server. However, it is much easier to simply use a recent version of WinSCP, and toggle the setting to make it talk SFTP.
Q24. The SFTP client I tested performs poorly with Bitvise SSH Server. How can I improve performance?
The answer to this question depends on whether you are seeing the server consume 100% CPU during most of the transfer.
If the server is consuming 100% CPU, then you are running into hardware limitations of the server system.
If you are not seeing 100% CPU consumption during most of the transfer, you're running into a limitation of the client. For high-performance transfers, the SFTP client must implement performance optimizations appropriate to available bandwidth and latency. These optimizations include:
- Read/write request sizing.
- Read/write request pipelining.
- SSH channel receive window sizing.
The only performance parameter the SFTP server has control over is its own SSH channel receive window size. However, this only affects the speed of uploads - not downloads - and Bitvise SSH Server is already aggressive in this regard; it's unlikely to bottleneck the client.
If your SFTP client doesn't reach transfer speeds that would cause the server to reach 100% CPU consumption, but network bandwidth is still available, try with a different client. Our Bitvise SSH Client performs aggressive pipelining, which might perform better than some other clients.
Please do not try to improve performance by disabling encryption. The performance impact of encryption is minimal, and disabling it defeats the principal goal of SSH, which is security.
Q25. How do I configure Bitvise SSH Server so that clients can upload files, but not see or modify existing files - a file drop scenario?
This behavior can be configured in Advanced SSH server settings. Under the account or group settings entry for which you want to configure this, open mount point settings under "Virtual filesystem". To implement a file drop scenario, remove permissions to List, Read Existing, Write Existing, and Delete Existing, but enable the permission to Read/Write/Delete New. Also, enable "Show empty directory if no access" (enabled by default).
For more general information, see also Configuring Bitvise SSH Server for SFTP, SCP file transfer.
Q26. I don't want the SSH Server to load the users' Windows profiles during file transfer sessions. How do I prevent the Windows profile from being loaded?
Bitvise SSH Server will load the user's Windows profile if it's asked to provide functionality that requires the Windows profile. To avoid loading the Windows profile, turn off options which require it to be loaded. In Advanced SSH server settings, either in a user or group settings entry, disable the following options:
- Map remote home directory
- Map remembered shares
- Load profile for SCP and SFTP
With all of the above options disabled, the SSH Server will not load the user's Windows profile for file transfer sessions.
Q27. Does Bitvise SSH Server lock files being accessed by a client, to prevent them being accessed by other applications? How do we enable such blocking?
By default, files that clients are accessing via SFTP or SCP will be available for access by other processes. However, some SFTP clients that implement a sufficiently high SFTP version can request different locking.
For most clients that do not implement this, the administrator of the SSH Server can configure settings for a mount point so that files are locked by default. This is done in Advanced SSH server settings, under Virtual filesystem layout settings for the mount point in question, under Provider settings. The parameter that needs to be added is FileShare, with value Disable.
Public Key Authentication
If you are having problems related to public key authentication, you may also want to check our page about Public Keys in SSH.
Q30. Someone wants to use public key authentication to log into the Bitvise SSH Server I'm administering. They have already sent me their public key file. How do I tell the SSH server to use the public key file when that user logs in?
In the Bitvise SSH Server Control Panel, open Advanced settings and go to Access Control > Windows accounts (or Virtual accounts if this is a virtual user). If an entry for this user is not already present, you need to add one. For Windows accounts, the name of the entry must match the Windows username that will be used when logging in. Now, click Edit to open the account entry in a new window, and click the 'Public keys' link. A key management window will open which you can use to import the public key.
Screenshots for importing a client authentication public key:
Please also read this page in the Bitvise SSH Server Users' Guide for important information about how SSH server account and group settings work.
Q31. I am unable to import a user's public key into Bitvise SSH Server's user key management window. I keep getting a dialog box telling me that the public key could not be imported. What could be the problem?
It is most likely that the public key you are trying to import is not in the right format. It might be a private key instead of the public key, or it may be an SSH1 public key file instead of an SSH2 key. The formats supported by Bitvise SSH Server are the standard SSH2 public key format, and the OpenSSH SSH2 public key format. The OpenSSH SSH1 public key format is different and incompatible with SSH2.
Another possible reason you might have trouble importing a public key is if you try to import it into the SSH server's "Manage host keys" interface, instead of into an SSH account settings entry. The SSH server's host key management interface, which is accessible directly from the Bitvise SSH Server Control Panel, is intended to manage host keys that are used to authenticate the SSH server. The place to import a client authentication keypair is into an individual account settings entry, either in Easy or Advanced SSH server settings.
Q32. The client sent their public key, I imported it into SSH Server settings, but public key authentication doesn't work, and they're still being prompted for a password. Help!
Most likely, the user's client software is doing one or more of the following:
- Not attempting to authenticate using a public key because the keypair is not properly configured in the client.
- Attempting to authenticate with a keypair that corresponds to a different public key than the one you imported for this client.
- Attempting to log into an account that does not match the one for which you imported this public key.
To see which problem it is, check the Activity tab of the SSH Server Control Panel, and/or the SSH Server's textual log files. If the client is not attempting to use public key authentication, you will see this as an absence of any public key authentication messages in the logs. If the client is using a different key, log messages will show that the server does not recognize the key they're using. If the client is attempting to log into a different account, there will be discrepancies between the user name provided by the client, and the one for which the public key has been imported in SSH Server settings.
Q33. How do I set up public key authentication with Bitvise SSH Client?
Generate a keypair in the SSH client's User Keypair Manager. Use the Export button to export the public key in standard SSH2 format. Transfer the resulting file onto the machine with Bitvise SSH Server. Follow the instructions in Q30 (above) to import the public key into Bitvise SSH Server. In the SSH client, configure the Login : Authentication : Initial Method setting so that the client will use your generated user keypair for authentication. You can also save your Bitvise SSH Client settings into a profile for convenience. You will now be able to connect with public key authentication.
Q34. When I use password authentication, I can access EFS-encrypted files, and network shares on the server's Local Area Network. But when I use public key authentication, EFS-encrypted files and network shares are inaccessible. How can I access them when using public key authentication?
In order to access EFS-encrypted files, the server needs to provide Windows with your password. Similarly, to provide you with access to network shares on other computers in the server's network, the server needs to authenticate you with the computer providing the network share.
When you log in using password authentication, the SSH server conveys your password to Windows, and your login session is created in a way which allows Windows to access EFS-encrypted files, and pass your login credentials to other Windows computers in the network, providing you with access to network shares.
When you log in using public key authentication, Bitvise SSH Server versions 5.50 and higher are able to create your login session without the SSH server knowing your account password. However, a login session created this way does not have credentials necessary to access EFS-encrypted files and network shares.
One way to solve this is to add your Windows account's password to the SSH server's password cache. You can do this through the "Manage password cache" link on the "Server" tab of the Bitvise SSH Server Control Panel. The server will remember the password you enter indefinitely. When you log in using public key authentication, the server will use the cached password to create a logon session which will have credentials necessary to access network shares. This will work as long as the cached password remains synchronized with the account's actual password.
If you only need access to network shares (but not EFS-encrypted files), another way is to configure the SSH server, through per-group or per-account settings, to explicitly establish connections to one or more network shares, by providing network share access credentials in the SSH server's configuration. This can be done through the "Windows file shares" section of an account or group settings entry, in Advanced SSH server settings.
Q35. How can I let users manage their public keys themselves, without administrative intervention?
Bitvise SSH Server supports two ways for users to manage their client authentication public keys without requiring the administrator's manual intervention.
SSH clients that support the Secure Shell Public Key Subsystem (RFC 4819) can use this functionality to add or remove public keys associated with their account in Bitvise SSH Server settings. This feature is enabled for all accounts by default.
Windows accounts that have write access to their Windows profile directory can use the authorized_keys synchronization mechanism. To enable this, the administrator must enable the setting Synchronize with authorized_keys under Access control in Advanced SSH server settings. Windows users can then store a file named "authorized_keys" in a subdirectory named ".ssh" under their Windows profile directory. When the user's SSH session ends, Bitvise SSH Server will check for the presence of this file, and if it exists, the public keys encoded in this file will replace the public keys configured for the user in SSH server settings. This feature is disabled by default because some users have existing .ssh/authorized_keys files they are not aware of, which would conflict with intended SSH server settings.
Q36. When I examine the SSH server's log entries for a session, I see a logon attempt using the "none" method that fails, followed by a logon attempt using the "publickey" method that fails, followed by public key authentication that succeeds. How can I resolve the two failures?
These failures are a normal part of SSH authentication. First, the client may send a "none" authentication request, which is intended to fail, but provides the client with information about authentication methods supported by the server. Then, the client may attempt public key authentication without a signature, which is also intended to fail, but tells the client whether the server will accept the client's public key. Then, armed with this knowledge, the client sends the actual public key authentication request, which succeeds.
The client could avoid the preliminary requests if it were to assume outright that the server supports public key authentication, and that the server will accept the public key the client is trying to use. In this case, the client can just send the full public key request directly, as its first authentication request.
However, it is perfectly okay for the client to send the preliminary requests. This is a normal part of SSH authentication.
Q37. Public key authentication for Windows accounts does not work unless I enter the account's password in the SSH Server's password cache. Even though Windows has been restarted, the SSH Server Control Panel continues to display the message "Public key authentication, as well as virtual accounts that use a custom security context, will not be fully operational until Windows is restarted."
It is possible that Windows has been configured to not load LSA authentication packages installed by third party programs. This prevents the loading of the SSH Server's authentication package, which it needs to create logon sessions where a password is not available.
To allow the SSH Server's authentication package to load, follow the instructions under "To disable LSA protection" as described in the Microsoft TechNet article Configuring Additional LSA Protection.
Q40. How do Bitvise SSH Server account settings work?
Please read this page in the Bitvise SSH Server Users' Guide for this important explanation.
Q43. How can I limit a user so that they cannot access files outside of a certain directory?
The answer depends on what sort of access you have in mind. For shell access and remote execution, jailing a user is possible only through Windows file system permissions. On the other hand, if you are permitting the user only file transfer access (using SFTP and SCP), you can configure a limited-access virtual filesystem for the user by editing settings for their account or group in Bitvise SSH Server settings. In settings for the individual account or group, open Virtual filesystem layout > Mount points, and set the 'Real root path' setting for the default mount point ('/') to the directory you want them to access.
Q44. How do I use virtual accounts on a domain controller?
On computers that are not domain controllers, Bitvise SSH Server manages a local Windows account to provide a security context for virtual account login sessions. See Q53 for more information about this account.
On domain controllers, the SSH Server cannot create this account because there is no concept of local accounts on a domain controller. If you would like to use virtual accounts on a domain controller, you need to create or designate a domain account which will provide a security context for your virtual account login sessions. You then need to configure this backing account in Advanced SSH Server settings, either individually for each virtual account settings entry, or in a group settings entry used by one or more virtual accounts.
Q45. If I use an explicitly configured backing account to provide a custom security context for virtual accounts, do I need to enter the backing account's password into the SSH Server's password cache?
When you explicitly configure a backing account for virtual users, you can choose to save the password for this backing account in the SSH Server's password cache using the "Manage password cache" interface in the SSH Server Control Panel.
If you configure the password cache, the SSH Server will be able to create virtual account login sessions that will have implicit access to EFS-encrypted files and network resources (e.g. Windows shares) accessible to the backing account. If you do not configure the password cache, the virtual account sessions will still work, but without access to such resources. See also Q34, which describes the same issue when using Windows accounts with public key authentication.
Usage Issues and Operation Concerns
Q51. How can a user change their password remotely?
Bitvise SSH Server supports changing a Windows account password during SSH user authentication by using a client that supports this feature, such as Bitvise SSH Client.
Additionally, Bitvise SSH Server comes with a 'bvPwd' utility which allows any user to change their password if they know what it currently is. The utility can be found in the SSH server installation directory; run it with 'bvPwd -h' for help. Additionally, administrators can use the 'net user' command intrinsic to Windows to change any user's password - type 'net help user' in a Command Prompt for help.
Recent Bitvise SSH Server versions also allow virtual account users to change their passwords using an SSH client that supports this feature, such as Bitvise SSH Client. Virtual account passwords can also be changed by an administrator in Bitvise SSH Server settings or using bsscfg.
Q52. My Bitvise SSH Server log is showing multiple login attempts from an unknown IP address. The log shows the server is accepting these connections and the client is trying to guess a username and password. Your software is letting hackers into my PC!
In order to refuse access to unauthorized users, while still allowing authorized users to log in, the SSH server must accept connection attempts coming from permitted sources, and must allow those connections to reach a point where the client can provide authentication credentials.
When installed with default settings, Bitvise SSH Server will already take several steps to thwart unauthorized attackers.
One way is by imposing a delay between login attempts. The default delay is 3 seconds. Without any other countermeasures, this 3 second delay would ensure that even an account with a weak password, e.g. 6 letters chosen randomly from an alphabet of 26, would on average take years of back-to-back attempts to guess. (Note however that passwords that short are still very weak and are not recommended.)
Another way Bitvise SSH Server tries to thwart attackers is through automatic blocking of IP addresses that have recently initiated multiple failed login attempts. In default settings, the SSH server will block for 1 hour any IP address that initiates more than 20 failed login attempts in 5 minutes.
If you wish to see fewer password guessing attempts, an effective mitigation is to configure your SSH server to accept connections on a port other than 22. This would not be very effective against a determined attacker, but will avoid random hackers looking for low-hanging fruit. Any random port number between 1024 and 65535 is suitable. The only issue is that any legitimate client that tries to connect to your server will then need to be configured with the port number in addition to the host name.
Despite these countermeasures, it is very important to make sure that your accounts are configured with complex passwords, and to lock down your settings so as not to grant access that you don't need to. For more information and for password complexity guidelines, see Securing Bitvise SSH Server.
Q53. When I install Bitvise SSH Server, it creates a local Windows account named BvSsh_VirtualUsers (or similar). What is the purpose of this account?
When you configure virtual users in Bitvise SSH Server settings, the SSH server needs to provide some kind of security context for actions taken by those users when they connect. Advanced SSH server settings allow you to configure a specific Windows account that should be used as security context for virtual users. If you don't take explicit steps to configure this, the SSH server will use as security context a default local Windows account, which it creates and manages for this purpose. In a default (unnamed) SSH server installation, this account is named BvSsh_VirtualUsers. (If your first installation was a version prior to 5.50, the account is named WinSSHD_VirtualUsers.)
You can use Windows Explorer, and other Windows administration tools, to apply Windows filesystem permissions to the BvSsh_VirtualUsers account. In this way, you can control what parts of your system a virtual user will be able to access. These Windows security permissions will apply to virtual users even if they are permitted to use terminal shell or exec requests, in which case, the virtual filesystem configured in SSH server settings does not apply.
You should not attempt to delete the BvSsh_VirtualUsers account, or change its password. Such changes will either be detrimental to your SSH server's operation, and/or will not be effective. Bitvise SSH Server will automatically enable this account when the SSH server is started, and disable it when the server is stopped. The SSH server will also periodically reset the password to this account, and set it to an extremely long, extremely complex random value. It will not be possible to log into this account, other than by allowing the SSH server to use it as security context for a virtual account.
Q54. Bitvise SSH Server's log files are very detailed. How do I extract just the information I'm looking for?
The SSH Server's log files are intended to be machine processable. Log files use the XML format, which can be handled by utilities such as Microsoft Log Parser, or custom applications. It's straightforward to process XML files using any .NET language.
For more information, see also Interpreting SSH Server log files using Microsoft Log Parser.
Q55. I enabled the "Omit server version" setting, but the server still sends the name of the product in the SSH version string. How can I completely remove product information from the version string sent to clients?
We support removing the exact server version number from the SSH version string, but we do not support completely removing the product name.
Any hacker who can exploit a server-specific vulnerability can also identify the server product based on the contents of the KEXINIT packet the server sends. KEXINIT packets are sent in plaintext and have specific patterns which are sufficient not just to identify the make of the server, but also a particular version subset.
Removing the server product name from the version string only serves to deny this information to legitimate clients, where it can be useful.
Upgrading and Moving
Q60. How do I upgrade my Bitvise SSH Server to the latest version?
There are two parts to the upgrade process:
Ensure that you have a license with upgrade access for the SSH server version to which you are upgrading. You can verify your upgrade access expiry date by logging into your License Overview.
If your upgrade access has expired, you will be able to add the desired number of license-years through the "Place a New Order" section under the license information. The expected new upgrade expiry date will be displayed on the page when you enter the desired number of license-years. The full cost will be displayed on the next page, at checkout.
- When you have a license with an activation code suitable for the latest version, download the installer for the latest version from our website. Run the installer on the computer where you want to upgrade your SSH server installation, and follow the process. Apply the new activation code in the Bitvise SSH Server Control Panel, once the upgrade is complete.
Q61. Will my settings and keys be preserved when I upgrade?
In general, yes. The upgrade process is intended to preserve your keypairs, your password cache, and your settings.
We do recommend making a backup of your settings before you upgrade. Settings can be exported using the Export function in the Bitvise SSH Server or WinSSHD Control Panel. A settings backup may be useful if the new version encounters a problem reading your settings, or if you decide to downgrade to the previous version again. The older version may not be able to read your settings once the new version has upgraded them.
Q62. I would like to move my SSH server to a different computer. How do I move my settings, password cache, and keypairs?
Settings. To move Bitvise SSH Server or WinSSHD settings, use the Export feature from the SSH server's Control Panel. On the new Bitvise SSH Server installation, use the Import feature to import the settings. Moving the settings will also move any client authentication public keys configured for user authentication.
Password Cache. In the latest Bitvise SSH Server versions, the password cache is necessary only if you use Windows domain accounts that need to log in using public key authentication, and also need to have implicit access as that account to network resources on other computers on the local network. In the latest Bitvise SSH Server versions, the password cache can be backed up into, and restored from a file, using Bitvise SSH Server Control Panel > Manage password cache > More > Backup items to file. If you want to move the password cache, but are using an older SSH server version which does not support backing up the password cache, you may want to upgrade the existing installation to a version that supports this, before moving.
Host Keypairs. It only makes sense to move keypairs used for SSH server authentication if the SSH clients accessing the server will continue to access the server using the same port, IP address, and/or DNS name. If there will be any change in what address or port the SSH client uses to access the SSH server, the client will need to re-verify the server's host key, so there's no benefit to transferring keypairs to the new installation.
If the clients will continue to access the server at the same address, the host authentication keypairs can be moved through the SSH Server Control Panel > Manage host keys.
Older WinSSHD versions (e.g. versions 4.xx) do not contain a user interface function to export a host authentication keypair. Depending on the version, you may be able to use the "wcfg" command line configuration utility to export the keypair. Alternately, you could upgrade to a more recent version in place, and export the keypair using the new version.
Client Public Keys. Public keys configured for client authentication are part of SSH server settings, and are moved implicitly when you export and import settings.
Q. I read the FAQ, but it didn't help me solve my problem. What do I do?
Contact us through our Contact page, and describe your problem in as detailed manner as possible. The more information you provide, the greater the chance of a swift and effective resolution.