Security
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- The CommuniGate Pro Server ensures that only certain users are allowed to access
certain resources.
The CommuniGate Pro Server can authenticate its users, and it can also reject connections from outside of the "client networks".
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Security |
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These secure methods allow mail clients to send encrypted passwords over non-encrypted and insecure links. If anybody can monitor your network traffic, SASL methods ensure that the real passwords cannot be detected by watching the client-server network traffic.
As an alternative to SASL methods, secure links (SSL/TLS) can be used between the client mailer and the server. When an SSL link is established, the entire network traffic between the server and the client is encrypted, and passwords can be sent in clear text over these secure links.
You can force an account user to use either a SASL authentication method or SSL/TLS links if you enable the Secure Method Required option in the Account Settings. When this option is enabled, the Server rejects all authentication requests that send passwords in the clear text format over insecure links.
The CommuniGate Pro Server supports the following insecure (clear text) SASL authentication methods:
The CommuniGate Pro Server supports the following secure SASL authentication methods:
The CommuniGate Pro Server supports the following SASL-EXTERNAL authentication methods:
The CommuniGate Pro Server supports the non-standard NTLM and MSN SASL methods used in Microsoft® products.
The CommuniGate Pro Server supports the following GSSAPI authentication methods:
The CommuniGate Pro supports the secure APOP authentication method (used mostly for the POP protocol), and the insecure "regular login" method for the protocols that support Clear Text Login.
The CommuniGate Pro Server supports the special WebUser authenticaton method.
Use the WebAdmin Interface to open a Domain Settings page and find the Login Methods panel:
One password is the CommuniGate Pro's "own password ". This password is stored as an element of the Account Settings, and it can be used with the CommuniGate Pro Server only.
The other password is the "OS password". The user may be registered with the Server OS and the CommuniGate Pro Server can check the supplied password against the password set in the Server OS registration information for this user.
An account can have the External Password option enabled. In this case, user authentication is done using any custom authentication program running as a separate process (see below).
The system administrator can enable any set of passwords for any user account. On larger sites, it is better to enable these options using the Server-wide or Domain-wide Default Account Settings.
When several passwords are enabled for an account, the Server first checks the CommuniGate (internal) password, then the OS password, and then tries to use the External Authentication program. If at least one of these passwords matches the password presented with the client application, the application is granted access to that account.
When the U-crpt Password Encryption option is selected, the CommuniGate
passwords are stored using the standard Unix crypt routine. If the
UB-crpt Password Encryption option is selected, an enchanced Blowfish-based
encryption is used.
U-crpt and UB-crpt methods implement a one-way encryption. As a result,
the Server cannot decrypt them into their original (clear text) form, and it cannot use them
for secure (SASL) Authentication Methods. Use these encryption methods
only if you need compatibility with legacy password strings, but cannot use the OS passwords -
it is usually more important to support "on-the-wire" security (using SASL methods), rather then
"on-the-disk" security (using one-way password encryption methods).
U-crpt passwords can contain special prefixes. These prefixes allow you to import passwords
encypted using other password encryption methods.
See the Migration section for more details.
Note: please remember that the plain Unix crypt routine uses only the first 8 symbols of the password string.
If the CommuniGate Password is absent or empty, it cannot be used to log into the Account even if the Use CommuniGate Password option is enabled. But if the user has logged in using the OS Password or the External Authentication method, the user can specify (update) the Account CommuniGate Password. This feature can be used to migrate users from legacy mail systems where you can not compose the list of accounts with non-crypted user passwords.
| Server Operating System | Notes about OS Passwords |
|---|---|
| Microsoft Windows 95/98/ME | OS does not support passwords, the Use OS Password option does not work. |
| Microsoft Windows 200x/XP/NT | The Windows NT domain authentication system is used. The Windows account
used to run the CommuniGate Pro Messaging Server
should have the Act as part of the operating system privilege.
The --BatchLogon command line option can be used to tell the Server to use the LOGON_BATCH authentication method (if the option is not present, the LOGON_NETWORK method is used). The Server checks if the composed OS user name contains the percent (%) symbol.
If the symbol is found, the part of the name before that symbol is used as the Windows
account name, and the part after that symbol is used as the Windows domain name.
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| Unix-based systems | The passwd and shadow or other OS-supported authentication mechanisms are used. |
| OS/400 systems | The user profile authentication mechanisms are used. |
| OpenVMS systems | The supplied user name and password strings are converted to uppercase, and then the OpenVMS authentication mechanisms are used. |
| BeOS | OS does not support passwords, the Use OS Password option does not work. |
The OS passwords are one-way-encrypted passwords. As a result, they cannot be used for Secure Authentication Methods.
To support Kerberos Authentication, you need to add Kerberos Server key(s) to the CommuniGate Pro Server, on the per-domain basis. Create a server "principal" in your KDC database. The principal name should be equal to the name of CommuniGate Pro Domain or one of its Domain Aliases. Export the created key as a keytab file.
Open the Domain Settings using the CommuniGate Pro WebAdmin Interface, and follow the Security and Kerberos links. The list of Domain Kerberos Keys will be displayed:
If the client presents such a Certificate, the E-mail field of the Certificate Subject is interpreted as the name of the CommuniGate Pro Account to log into.
Note: The Certificate Authentication mechanism does NOT run the provided E-mail address via the Router. If it would use the Router, a name in one Domain could be routed to a name in a different Domain, so the Kerberos Keys valid for one Domain would provide access to Accounts in a different Domain. As a side effect, the Account Aliases cannot be used with Certificate Authentication.
Only Accounts with enabled Certificate Authentication method can be accessed using Client Certificates.
See the PKI section for more details.
The External Authenticator can also be used to automatically provision Accounts based on some external data source, and/or to assist with the Router operations.
The External Authenticator program name and its optional parameters should be specified using the WebAdmin Helpers page. Open the General page in the Settings realm, and click the Helpers link:
See the Helper Programs section to learn about these options.
The External Authentication module System Log records are marked with the EXTAUTH tag.
If the External Authentication program is not running, all External Authentication requests are rejected.
To create your own External Authentication program, see the Helpers section to learn about the External Authentication interface protocol.
Sample External Authentication programs and scripts can be found at the http://www.stalker.com/CGAUTH/ site.
To prevent this type of attack, you may want to enable the Hide Unknown Account messages option, located on the Obscure page in the WebAdmin Settings realm:
In order to control, monitor, and maintain the CommuniGate Pro Server, one Postmaster account is usually enough. But you may want to allow other users to connect to the CommuniGate Pro Server: for example, you may want to allow an operator to monitor the Logs, but you do not want to grant that operator all Postmaster access rights.
You should be logged in as the Postmaster, or you should have the "Can Modify Access Rights" right in order to assign access rights.
To grant access rights to a user and/or to revoke those rights, open that user Account (the Account Setting page), and click the Access Rights link. The Access Rights page will appear.
The page lists all Access Rights and the rights granted to the selected user are marked.
The following access rights can be granted only to the users (accounts) in the main domain:
The following access rights can be granted to users in any domain:
Initially, the user Postmaster in the main domain has the Unlimited Access right.
Select the desired Access Rights and click the Update button.
The Access Rights are stored in one file for each domain, the Access.settings file stored in the Settings subdirectory of the domain directory. This makes it easy to check to whom the Server administration rights are granted.
When an access module accepts a connection from an unlisted network address, and this option is selected, the module sends an error code to the client application, and the connection is closed immediately. Links with the rest of the Internet will be used only for mail Transfer and access to Personal File Sites.
When this option is selected, the SMTP AUTH operation can be used only if a client mailer or server connects from the network address included into Client Addresses list.
Note: Before you enable this option, make sure that the address you are using is included into the Client Addresses list: otherwise you will immediately lose access to the Server.
You can also specify the access restrictions on the lower (TCP) connection level. For each service (module), open the Listener page and specify the addresses the service (module) should or should not accept connections from. If a connection comes from an address that is not included into the Grant list or is included into the Deny list, the connection is closed immediately, and no module-level operations are performed.
Impersonating is supported for PLAN and GSSAPI Authentication methods. It can also be used for Real-Time Registration.
When Impersonating is used, the Server checks if the authentication Account credentials are valid, and if the requested service is allowed for that Account. It also checks if the Authentication Account has the CanImpersonate Domain access right.
The WebUser SASL method works only for programs running on the same Server computer, or for programs running on other servers in the CommuniGate Pro Cluster.
The method is a SASL method and requires "immediate" parameters in the authentication protocol command. The first parameter
is the account name, the second parameter, separated with the space symbol, is the WebUser session ID.
The WebUser authenitcaiton operation for the PWD module is:
If the user john@doe.dom has an open WebUser Session with the 114-bXaKw92JK1pZVB5taj1r ID, then the PWD command: