CommuniGate Pro
Version 5.2
SysAdmin
 
 
Security

Security

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".

Authentication Methods

The CommuniGate Pro Server supports both clear-text and secure SASL authentication methods for the following TCP-based session-oriented protocols:

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 GSSAPI 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 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 SessionID Authenticaton method.

Use the WebAdmin Interface to open a Domain Settings page and find the Login Methods panel:

Login Methods
CLRTXT CRAM-MD5 DIGEST-MD5 APOP
GSSAPI NTLM MSN SESSIONID
CLRTXT
When this option is selected, the Server advertises all supported non-secure (clear text) authentication methods for this Domain.
CRAM-MD5, DIGEST-MD5
When these options are selected, the Server advertises the secure CRAM-MD5 and DIGEST-MD5 authentication methods for this Domain.
Do not select these options if the Domain Accounts use one-way encrypted passwords, OS Passwords, or other authentication methods that do not support secure authentication methods.
APOP
When this option is selected, the Server provides a special initial prompt for POP and PWD connections. Mail clients can use this prompt to employ the secure APOP authentication method.
Do not select this option if the Domain Accounts use one-way encrypted passwords, OS Passwords, or other authentication methods that do not support secure authentication methods.
GSSAPI
When this option is selected, the Server advertises support for the GSSAPI authentication method.
Do not select this option if the Domain is not set to support GSSAPI methods (for example, you have not specified the required Kerberos Keys).
MSN, NTLM
When these options are selected, the Server advertises the non-standard MSN and NTLM authentication methods (used in some Microsoft products) for this Domain.
Do not select these options if the Domain Accounts use one-way encrypted passwords, OS Passwords, or other authentication methods that do not support secure authentication methods.
Note: The Microsoft Outlook products for various versions of MacOS do not work correctly with the MSN method if more that one account is configured in those products.
Note: Some Microsoft products send incorrect credentials when they detect that the server supports the NTLM SASL method. While those products then resend the correct credentials, the failed login attempts produce Failure-level Log records and may increase the "failed logins" counter too quicky, so the account becomes "temporarily locked".

The Advertise options control only the session-type services (SMTP, POP, IMAP, ACAP, PWD, FTP), and they do not have any effect on the transaction-type services (HTTP, SIP).
The Advertise options control only how the methods are advertised. Client applications can still use all these methods, even if these options are switched off.

SESSIONID
This option enables the SessionID Authentication method for the Domain.

Account Passwords

The CommuniGate Pro Server supports several passwords for each account.

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.


CommuniGate Passwords

CommuniGate passwords are strings stored in the Account Settings. Password strings can be stored in the clear-text format or in encoded format. The Password Encryption Account Setting specifies the encryption to use when the account password is updated. When this setting is changed, the currently stored password is not re-encrypted.

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.


OS Passwords

When the Server checks the OS password, it composes the username string using the Account OS User Name setting. When the default setting * is used, the composed OS user name is the same as the Account name. By changing the OS User Name settings you can use different OS usernames for Accounts in different CommuniGate Pro domains.

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/Vista 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.
If Accounts in the company1.dom CommuniGate Pro domain have the OS User Name setting set to *%comp1, then the OS user name for the CommuniGate Pro Account joe will be joe%comp1, and the CommuniGate Pro Server will use the Windows LogonUser API to try to authenticate the mail client as the Windows user joe in the Windows domain comp1.

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.


Kerberos Authentication

The CommuniGate Pro Server supports the Kerberos authentication method. The Kerberos method is based on the "tickets" that client applications send to the server. These tickets are issued by Kerberos authorities (Key Distribution Centers, KDC) that share a common "key" with the Server. See the Kerberos documentation for the details.

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:

  Realm Issued Version Type
REALM1.COM(3)imap/domain1.com19-05-2004 17:36:336RC4-HMAC
REALM1.COM(3)imap/domain1.com21-05-2004 17:32:359DES-MD5
REALM1.COM(3)imap/domain1.com24-05-2004 12:41:5510DES-MD5
REALM1.COM(3)imap/domain1.com24-05-2004 17:33:2713DES-CRC32

Each Domain can have several Kerberos Keys. To add Keys, click the browser file-select button and select the keytab file exported from KDC. Click the Import Keys button to add keys from the file to the set of the Domain Kerberos Keys.

To remove Keys, mark the Keys using checkboxes and click the Delete Marked button.

Domain Administrators can Add or Remove Kerberos Keys only if they have the KerberosKeys Access Right.

When the Server receives a Kerberos Ticket, it extracts the Server Name ("sname") from the Ticket. If the Server Name has only 1 component (domain.dom), this component is used as the target Domain name (ticket-domain-name). If the Server Name has 2 or more components (service/domain.dom), then the second component is used. The Server then builds a fictitious E-mail address LoginPage@ticket-domain-name and tries to route this address. This is the same routing mechanism as one used for finding the target Domain for HTTP requests.

If the target Domain is found, the Server looks for the proper key in the list of the Kerberos Keys for that Domain. If the Key is found, and the Ticket and Authorization info can be decrypted with that Key, the user is authenticated. The name of the Account is taken from the Client Name specified in the Ticket. That name must be a "simple" name, i.e. it cannot contain @ or % symbols.

CommuniGate Pro adds the name of the target Domain to the retrieved user name and uses the resulting E-mail address as the name of the Account to open.

Note: The Kerberos Authentication mechanism does NOT run the resulting user name 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 in Kerberos tickets.

Only Accounts with enabled Kerberos Authentication method can be accessed using Kerberos tickets.

Integrating with Microsoft Active Directory

You may want to use Microsoft Active Directory as your Kerberos Key Distribution Center (KDC). Follow these steps:

See the Microsoft Knowledge Base artcile Q324144 for more details.

If you want to use Kerberos Authentication (Single Sign-on) with Microsoft browsers, please read the "HTTP-Based Cross-Platform Authentication via the Negotiate Protocol" article in the Microsoft documentation set (MSDN).


Certificate Authentication

The CommuniGate Pro Server supports the Client Certificate authentication method. This method can be used when clients connect to the Server via secure SSL/TLS connections. The Server may request a client to send a Client Certificate (installed on the client computer), signed with the Trusted Certificate selected on the Server for the target Domain.

If a client sends such a Certificate, the E-mail address specified in the Certificate subjectAltName element (if any) or in the Subject element E-mail field can be used for the Certificate-based Authentication. It is 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 Trusted Certificates valid for one Domain would provide access to Accounts in a different Domain. As a side effect, the Account Aliases cannot be used with the Certificate Authentication mechanism.

Only Accounts with enabled Certificate Authentication method can be accessed using Client Certificates.

See the PKI section for more details.


External Authentication

The CommuniGate Pro Server can use an external Helper program for user authentication. That program should be created by your own technical staff and it can implement authentication mechanisms required at your site but not supported directly with the CommuniGate Pro Server.

The External Authenticator can also be used:

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:

External Authentication
Log Level: Program Path:
Time-out: Auto-Restart:

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 Authentication Helpers site.


Account Name Harvesting

Some spammers use 'brute force' attacks on mail systems, sending random names and passwords to system POP, IMAP, and other access ports. If the system sends different error messages for the "unknown account" and "incorrect password" situations, the attacker can harvest a large portion of the system Account names and then use those names for spam mailings.

Use the WebAdmin Interface to configure the Login Security options. Open the General pages in the Settings realm, and find the Login Security panel on the Others page:

Login Security
  Hide 'Account Unknown' messages
Suspend Account after   failed logins within 
Hide Unknown Account messages
If this option is enabled, the Server does not send the Unknown Account and Incorrect Password error messages. Instead, both messages are replaced with the Incorrect Account Name or Password error message.

Account Password Attacks

The CommuniGate Pro server can temporarily disable all types of login operation for an Account that has seen too many incorrect login attempts. The Login Security panel shown above allows you to specify a time period and the number of incorrect login attempts that a user or users can make before the Account is disabled for login operations. The Account is re-enabled after the same period of time.


Granting Access Rights to Users

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 administrator intefraces of your 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 other Account with the "Can Do Everying" 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:

Can Do Everying (the Master right)
If a user is granted this right, it has all access rights to all System components.
Can Modify Server and Module Settings (the Settings right)
This right allows a user to change configuration of all CommuniGate Pro components and modules (SMTP, POP, Router, etc.)
Can Modify Directory Settings (the Directory right)
This right allows a user to change configuration of the System Directory
Can Modify All Domains and Accounts Settings (the All Users right)
This setting specifies if the user is allowed to create, rename and delete Domains, Accounts and other Objects, and to change Domain, Account, and other Object Settings.
Can Monitor (the Monitor right)
This setting specifies if the user is allowed to view Server Logs, to monitor Server Queues, etc.

The following access rights can be granted to users in any domain:

Can Modify This Domain and its Account Settings:
This setting specifies if the user is allowed to create, remove and delete Accounts within its own domain, and to change some of the Domain Settings. You usually assign this right to a user ("domain master") who will manage the domain.

Initially, the user Postmaster in the main domain has the Master 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 who is granted the Server Administration rights.


Restricting Access

If you do not plan to support mobile users, you may want to restrict access to the Server accounts. Use the following option on the Client IP Addresses page:

Logins from Non-Client Addresses
When the "probibit" option is selected, all "login" operations (needed for POP, IMAP, SIP, XMPP, WebUser Interface, ACAP, PWD, etc.) are accepted only from the Server computer itself, and from the Client IP Addresses.

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, Real-Time Signals exchange, and for HTTP access to Account File Storage.

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.

When this option is selected, any Signaling operation that requires authentication can be used only if a client device or server connects from the network address included into Client Addresses list.
Note: Before you enable this option, make sure that the network address you are currently using is included into the Client Addresses list: otherwise you will immediately lose HTTP Admin 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

The CommuniGate Pro Server supports impersonating - a login mode when the credentials are supplied for one Account (the Authentication Account), while a different Account (the Authorisation Account) is being opened.
It can also be used for
Real-Time Registration.

Impersonating is supported for PLAIN and GSSAPI Authentication methods.

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 SessionID Authentication Method

The CommuniGate Pro Server supports the special SessionID Authenticaton method. This method uses the session ID of a WebUser or XIMSS session instead of the Account password.
The method is useful for CGI programs and scripts.
This method is disabled by default (see above).

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 session ID.
The SESSIONID authentication operation for the PWD module is:

AUTH SESSIONID userName session-ID

The SESSIONID authentication operation for the IMAP module is:
AUTHENTICATE SESSIONID bindata
where bindata are base64-encoded parameter data:
userName session-ID

If the user john@doe.dom has an open WebUser Session with the 114-bXaKw92JK1pZVB5taj1r ID, then the PWD command:
AUTH SESSIONID john@doe.dom 114-bXaKw92JK1pZVB5taj1r
opens the john@doe.dom account in this PWD session.


CommuniGate® Pro Guide. Copyright © 1998-2008, Stalker Software, Inc.