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HTTP

The HTTP proxy employed in the Endian UTM Appliance is squid, whose primary ability is to cache web requests to speed up future requests of the same page, though it has many more functionalities that allows its seamless integration with the other services described in the remainder of this section. The HTTP proxy settings page is composed of six tabs that organise a myriad of options: Configuration, Access Policy, Authentication, Web Filter, AD join, and HTTPS Proxy.

Configuration

A click on the Enable HTTP Proxy grey switch swoff starts the HTTP proxy. After some seconds, necessary to start all required services, a number of controls appear in the Configuration tab, grouped into six panels: Each panel has a title, followed by a ? that shows a tooltip, and can be expanded or collapsed by clicking on the expand or collapse icons located on the left of the labels.

Transparent and Non Transparent Proxy.

A transparent proxy is a proxy system combined with a gateway: Besides retrieving and caching resources, a transparent proxy allows to carry out many useful operations on the web page or resource that the client is requesting: To filter its contents, to scan it and look for viruses, or even to block information, combining different services running on the gateway. Moreover, all these activities are accomplished without requiring the user to configure in any way the client she is using.

Non-transparent proxies on the contrary, rely on the collaboration of the client to be used (e.g., configuring the proxy settings on the web browser), requiring that the user specify by hand the location of the proxy in the setting of the browser, or she will not be able to access the Internet.

See also

The configuration of a transparent proxy is explained in this tutorial Transparent HTTP Proxy Basic Setup.

Note

In the New Mini Arm the Cache management panel (see further on) does not appear, therefore some of the option described here will not be available .

The first setting is to select from a drop-down menu how the users in each enabled zone -GREEN, ORANGE, BLUE- can access the proxy (No drop-down menu is available for non-enabled zones):

not transparent
The proxy server is available to anyone with no need to log in, but the clients need to configure their browser manually or tell the browser to search for a proxy (i.e., using either PAC or the WPAD protocol to set up the browser’s proxy settings).
transparent
The proxy server is available to anyone and no browser configuration is needed: All the HTTP traffic is intercepted and forwarded to the proxy server, that is in charge of retrieving the requested web pages and serve them to the clients.
transparent (keep original source IP address)
This configuration is very similar to the previous option, with the only difference that every packet that leaves the proxy keeps some of the client’s original information: Its IP address, plus the zone and interface from which the traffic originated.
inactive
The proxy is not active for that zone.

Note

Some browsers, including Internet Explorer and Firefox, are able to automatically detect proxy servers by using WPAD. Most browsers also support PAC, through a special URL. When using an Endian UTM Appliance as the proxy server, this URL looks like this: http://<GREENIP>/proxy.pac.

Proxy settings

In the Proxy settings panel there are some global configuration options for the proxy services:

Port used by proxy
The TCP port on which the proxy server is listening for connections, which defaults to 8080.
Error Language
The language in which error messages are displayed, which defaults to the one chosen in Menubar ‣ System ‣ GUI settings.
Visible Hostname used by proxy
The hostname assumed by the proxy server, also reported at the bottom of error messages.
Email used for notification (cache admin)

The email address shown by the proxy server in error messages.

Note

The cache admin e-mail address is not present in the Mini appliances, since cache management is not available there.

Maximum download size (incoming in KB)
The limit for HTTP file downloads. 0 means unlimited.
Maximum upload size (outgoing in KB)
The limit for HTTP file uploads (e.g., those used by HTML forms with file uploads). 0 means unlimited.
Keep source IP address
This option affects all the zones that are configured as non-transparent mode. When ticked, all the packets coming from the proxy will keep some information of the requester (client): Its IP address and the zone/interface from which the traffic originated.

Allowed ports and ssl ports

Configuration option for the ports the clients are allowed to use when browsing:

Allowed Ports (from client)
The TCP destination ports to which the proxy server will accept connections when using HTTP. One port or one port range per line are accepted, comments are allowed and start with a #, ending at the end of the line.
Allowed SSL Ports (from client)
The TCP destination ports to which the proxy server will accept connections when using HTTPS. One port or port range per line are accepted, comments are allowed and start with a #, ending at the end of the line.

Log settings

Configuration option to enable the logging facility and choosing what to log.

HTTP proxy logging
Log all the URLs being accessed through the proxy. It is a master switch, hence the following four options are enabled and can be configured only if logging is enabled, which is not by default (recall that the more is logged, the more space on the Endian UTM Appliance’s hard disk is needed).
Query term logging
Log the parameters in the URL (such as ?id=123).
Useragent logging
Log the user agent sent by each browser.
Contentfilter logging
Log when the content of web pages is filtered.
Firewall logging (transparent proxies only)
Let the firewall log the outgoing web accesses, i.e., those directed through the RED interface to the Internet. This options only works for transparent proxies.

Bypass transparent proxy

In this panel some exception to the transparent proxy can be defined: which sources (i.e., clients) and destinations (i.e., remote servers) should be ignored by the proxy, even if it is enabled in that zone.

Bypass transparent proxy from SUBNET/IP/MAC
The sources that should not be subject to the transparent proxy. Entries can be single IP addresses, subnets, or MAC Addresses.
Bypass transparent proxy to SUBNET/IP

The destinations that are not subject to the transparent proxy. Entries can be single IP addresses or subnets.

Hint

Use CIDR notation to enter subnets.

Cache management

Configuration options for the space occupied on disk by the cache and the size of the objects stored.

Cache size on harddisk (MB)
The amount in megabytes that the proxy should allocate for caching web sites on the hard disk.
Clear cache
Click on the clear cache button to immediately erase the cache on disk.
Cache size within memory (MB)
The amount in megabytes of memory that the proxy should allocate for caching web sites in the system memory.
Do not cache this destination
The resources downloaded from these sites will never be stored in the cache. Entries can be domain names or single IP addresses (without subnet).
Maximum object size (KB)
The upper size limit in megabytes of a single object that should be cached.
Minimum object size (KB)
The lower size limit in megabytes of a single object that should be cached.

Note

Objects whose size does not fall within the above defined ranges will never be stored in the cache on disk, but downloaded each time they are requested by a client.

Cache offline mode

When this option is enabled, the proxy will never try to update cached objects from the remote web server, therefore clients will be able to browse cached, static websites even after the uplink went down.

Warning

This option proves useful to surf the Internet while the uplink is down, if the page requested has been cached before. However, this option may cause some trouble when trying to refresh a page, even with a working uplink, since the HTTP proxy would always serve the cached page. The only possibility to have a refreshed copy of a web page is in this case to clear the cache of the proxy server.

Upstream proxy

If there is another proxy server in the LAN, it can be contacted before actually requesting the original resource. This panel contains configuration options for the connection between the Endian UTM Appliance and the upstream proxy.

Upstream proxy
Tick this checkbox to enable an upstream proxy and show more options. When enabled, before retrieving a remote web page that is not already in its cache, the Endian UTM Appliance’s proxy contacts the upstream proxy it to ask for that page.
Upstream server
The hostname or IP address of the upstream server.
Upstream port
The port on which the proxy is listening on the upstream server.
Upstream username / password
If authentication for the upstream proxy is required, specify the credentials here
Client username forwarding
Tick the checkbox to forward the username to the upstream proxy.
Client IP forwarding
Tick the checkbox to forward the client IP address to the upstream proxy.

Access policy

The accesses policies are applied to every client that is connecting through the proxy, regardless of its authentication. An access policy rule is a time-based scheme that permits or prohibits accesses depending on diverse parameters about the user (e.g., the source or destination of the traffic), and the client used or the content downloaded (e.g., the user agent, the mime types, virus scanning, and content filtering).

A list of the already defined rules is displayed on the page. Any rule can specify if the web access is blocked or allowed, and in the latter case a filter type can be activated and selected. The table carries the following information for each rule listed therein: The progressive identification number (#), the name (Policy), the source and destination interested, the authentication type, if required, the periods in which is active, the user agents matched, and the available actions.

Note

The policies are evaluated from top to bottom, therefore their order is important.

To add a new access policy rule, simply click on Add Access policy: A form will open, in which to configure all the parameters:

Source Type
The sources of the traffic to which this rule applies. It can be <ANY>, a zone, a list of networks, IP addresses or MAC addresses.
Destination Type
The destinations of the traffic to which this rule will be applied. This can be either <ANY>, a zone, or a list of networks, IP addresses, or domains.
Authentication

The type of authentication to apply to the clients. It can be disabled, in which case no authentication is required, group based or user based. One or more users or groups, to which to apply the policy, can then be selected among the existent ones from the list that will show up.

Hint

Authentication is only local, hence before being able to use it, at least one user or group must be created in the Authentication tab.

Time restriction

Decide whether the rule has effect on specific days and/or a time period. By default a rule is always active, but its validity can be limited to either an interval or to some days of the week.

By ticking the checkbox, the following options become available:

Active days

Select one ore more days of the week.

Hint

To select two or more days, hold the CTRL keys and click the mouse button on the name of the day.

Start hour, Stop hour, Start minute, Stop minute
To fine-tune the interval of the day during which the access policy is active, select the start and end times from these drop-down menus.
Useragents
The allowed clients and browsers, as identified by their user agent, i.e., their identification string.
Mimetypes

A list of the MIME types of incoming files that should be blocked, one per line. MIME types can only be blocked (i.e., blacklisted) but not allowed (i.e., whitelisted), therefore this option is only available in Deny access policies. This option allows to block any files not corresponding to the company policy (e.g., multimedia files).

Note

The list of the available MIME types can be found in the /etc/mime.types file on any Linux box, on the official IANA web page, and also in RFC 2045 and RFC 2046.

Access policy
Select whether the rule should allow or deny the web access from the drop-down menu . When set to Deny access, the Mimetypes option above is activated.
Filter profile
This drop-down menu, available when the Access policy has been set to Allow access, allows to select what type of check should the rule perform. Available options are: none for no check and virus detection only to scan only for viruses. Moreover, if any content filter profile has been created (see section Web Filter below), it can be applied to the rule.
Policy status
Whether the rule is enabled or disabled. Disabled rules will not be applied, the default is to enable the rule.
Position
The place where the new rule should be inserted: Lower positions have higher priority.

Authentication

The Endian UTM Appliance’s proxy supports four different authentication types, that are shown in the drop-down menu at the top of the page: Local Authentication (NCSA), LDAP (v2, v3, Novell eDirectory, AD), Windows Active Directory (NTLM) and RADIUS. The NCSA type stores the access credentials on the Endian UTM Appliance, whereas the other methods rely on an external server: In those cases it is mandatory to provide all the necessary information to access that server.

Underneath the drop-down menu from which to select the authentication type, two panels are present. The one above, Authentication settings contains common configuration items, while the one below changes upon the selection of the authentication type, presenting the settings that are peculiar to each method.

Authentication settings

The common items that can be configured in this panel are:

Authentication realm

The text shown in the authentication dialog and used as the realm of kerberos or winbind when joining an Active Directory Domain. When Windows Active Directory is used for authentication, the FQDN of the PDC should be used.

Hint

If the server name is localauth and the domain name is example.org, the FQDN is localauth.example.org.

Number of Authentication Children
The maximum number of authentication processes that can run simultaneously.
Authentication cache TTL (in minutes)
The time in minutes during which the authentication data should be cached, before being deleted.
Number of different IPs per user
The maximum number of IP addresses from which a user can connect to the proxy simultaneously.
User / IP cache TTL (in minutes)
The time in minutes an IP address is associated with the logged in user.

Once the common configuration form have been filled in, depending on the authentication type chosen it is possible to configure the specific settings for the authentication type selected. Local Authentication (NCSA), Windows Active Directory (NTLM), LDAP (v2, v3, Novell eDirectory, AD), RADIUS.

NCSA specific settings

NCSA user management

When clicking on the manage users button the management GUI for the users is opened, which consists of a simple list of the existing users, if any was created.

Above the table, click on the Add NCSA user link to add more users: Simply provide a username and password in the form.

Click on the Apply button to save any change made to the users.

NCSA group management

When clicking on the manage groups button the management GUI for the groups is opened which consists of a simple list of the existing groups and their members, if any was created.

Above the table, click on the Add NCSA group link to add more groups. A group is created by entering a group name and selecting one or more users that should belong to that group. A user may belong to more than one group.

Warning

While the same user can be legally part of one or more groups, care must be taken that the the groups the user belongs to do not define contrasting access policies. As an example, consider a user member of two groups, one with the policy to allows access to the website www.example.org, while the second group’s policy blocks the access to that web page. In this case, it is not easy to predict whether that user will be granted or not access to the site. The management of these issues is left to the designer of the access policies.

Min password length
The minimum length for the local user’s password, which is by default 6 characters long.

NTLM specific settings

Domainname of AD server
The active directory domain to join. The server’s FQDN should be used.
Join AD Domain
Click on the join domain button to join the domain. This action should be done only after the authentication settings have been saved and applied. This will open the AD join tab.
Domain name for legacy systems

Write here the domain name if the Active Directory is on a Windows 2000 or older system.

New in version 5.0.

PDC hostname of AD server
The hostname the PDC.
PDC IP address of AD server
The IP address of the PDC.

Note

Both hostname and IP address are needed to create the DNS entry to access the Primary Domain Controller.

BDC hostname of AD server
The hostname the PDC.
BDC IP address of AD server
The IP address of the PDC.

Note

Both hostname and IP address are needed to create the DNS entry to access the Backup Domain Controller.

Requirements for the use of NTLM.

In order to be able to use Windows’ native authentication with active directory (NTLM), a few conditions must be satisfied:

  • The authentication settings need to be saved and applied before trying to join the domain.
  • The Endian UTM Appliance must join the domain.
  • The system clocks on the Endian UTM Appliance and on the active directory server must be synchronised.
  • The authentication realm must be a FQDN.
  • The PDC hostname has to be set to the netbios name of the Active Directory server.

Hint

The Endian UTM Appliance clock can be synchronised with the clock of the Active Directory server by issuing the following command from the shell:

net time set -S IP_OF_AD_SERVER

See also

The setup of a realm using NTLM authentication is described in this tutorial.

NTLM authentication with Windows Vista and Windows 7.

The HTTP Proxy in the Endian UTM Appliance uses negotiated NTLMv2, while both Windows Vista and Windows 7 allow by default only straight NTLMv2. As a result, a client using one of these operating systems may fail to authenticate to the HTTP proxy even when supplying the correct credentials. The following changes to the client configuration are required to correctly authenticate:

  1. Start ‣ gpedit.msc (run as administrator)
  2. Go to: Computer configuration ‣ Windows Settings ‣ Security Settings ‣ Local Policies ‣ Security Options
  3. Find the configuration option Network Security: LAN MANAGER Authentication Level
  4. Select the value “Send LM * NTLM - use NTLMv2 session security if negotiated”

After applying these changes the client browser should correctly authenticate using the AD login name for the HTTP Proxy.

LDAP specific settings

LDAP server
The IP address or FQDN of the LDAP server.
Port of LDAP server
The port on which the server is listening. The default value is 389.
Bind DN settings
The base distinguished name, this is the start point of the search.
LDAP type
This drop-down menu allows the choice of the type of the authentication server among Active Directory Server, LDAP version 3, LDAP version 2, or Novell eDirectory Server.
Bind DN username
The fully Distinguished Name of a user, which must have the permission to read user attributes
Bind DN password
The password of the bind DN user.
user objectClass
The objectClass that the bind DN user must belong to.
group objectClass
The objectClass that the bind DN group must belong to.

RADIUS specific settings

RADIUS server
The IP address or URL of the RADIUS server.
Port of RADIUS server
The port on which the RADIUS server is listening. Defaults to 1645.
Identifier
An additional identifier.
Shared secret
The password to be used.

Web Filter

The Endian UTM Appliance’s content filter abilities are based on the Cyren URL filtering solution, that uses two filtering techniques which can be customised for each filter profile.

The first one consists of an advanced method of web pages categorisation, based on their content, while the second method uses a combination of white- and blacklists URLs and domains: All the URLs requested by a client are looked up in this list and are only served if they are found in the whitelist.

Note

If the system has not yet been registered to Endian Network, the URL filter lists can not be downloaded. In this case, an informative message appears: By clicking on it, the registration form will open.

A profile is needed to be able to use the content filter. There is a Default profile available, which allows access to every web page and should never be deleted. Additional profiles, that are needed when defining new access policies, can easily be created.

On the page, there is a list of the existing profiles, accompanied by a remark and by the available actions.

Above the table, there is a Add new profile link: When clicked, the link is replaced by the Profile Editor, that is used to configure a new profile, with the list of existing profiles shifting to the bottom of the page. The following settings can be defined:

Profile name
The name given to the profile.
Activate antivirus scan
Enable the antivirus in the content filter.
SafeSearch Enforcement

In this multiselect box it is possible to enable the SafeSearch Enforcement functionality for the supported search engines, which currently are:

  • Bing
  • DuckDuckGo
  • Google
  • Yahoo
  • Yandex

SafeSearch Enforcement

With the use of the standard web filtering functionality it is already possible to filter inappropriate web sites for children or students. However, this does not affect results such as the preview images from the search engines.

These images are indeed cached and it is impossible to know from which website they have been retrieved; therefore the category-based filter cannot blocked them. To still be able to block inappropriate or offensive content many search engines include a SafeSearch functionality that, when enabled, will simply not include these results.

Since most search engines today are automatically using HTTPS, to it is necessary to enable the HTTPS Proxy.

The next settings come in form of panels, that can be expanded or collapsed by clicking on the expand or collapse icons to the left of their title.

URL Filter

Choose the categories to activate for applying the content filter. On the far right of the category’s name, icons show if the contained items are being considered actaccept or not actdeny for content filtering, or partially allowed partial. Those arrows can be clicked to quickly toggle the status of all the items.

Each category contains additional sub-categories, accessible by clicking on the category’s name,that can be individually selected.

The description of the sub-categories can be found on Cyren’s website.

Custom black- and whitelists

In these textfields, personalised lists of web pages can be added.

Allow the following sites
Web pages that are whitelisted, i.e., always served to the client.
Block the following sites
Web pages that are blacklisted, i.e., never served to the client.

Content filtering may cause both false positives and false negatives, hence list domains that should always be blocked or allowed can be entered here. This policy will be applied regardless of the results of the content filter’s analysis.

AD join

In this section it is possible to supply the credentials required to join the Active Directory Server, an operation that is only possible if in the Authentication tab the option Windows Active Directory (NTLM) has been selected.

Username of ADS admin
The username of the Active Directory Server.
Password of ADS admin
The password of Active Directory Server. It is not shown by default, but it can be displayed by ticking the checkbox on the right of the text field.

After supplying the credentials, click on the Join ADS button to connect.

HTTPS Proxy

New in version 5.0.5: URL Filtering option.

In this page it is possible to configure the HTTPS proxy server and the way it intercepts and applies content filtering to SSL-encrypted traffic, i.e., traffic through the 443 port.

The page is initially divided in three panels, the first one to choose the operating mode of the HTTPS proxy, the other related to the certificate needed in the Decrypt and scan mode.

HTTPS proxy operating mode

Choose form the drop-down menu how the proxy should analyse the HTTPS encrypted traffic. The following options are available:

  • Disabled. The HTTPS proxy will not analyse the traffic.
  • URL filtering only. In this modality, described below, the HTTP proxy will only apply content filtering to the pages, but not decrypt them.
  • Decrypt and scan. The HTTPS proxy will decrypt and fully inspect the pages.

Once the modality has been chosen, click on Save, then on the Apply button in the green callout.

The URL Filtering mode

The URL Filtering mode allows to apply content filtering to HTTPS pages in a less invasive way compared to the Decrypt and scan mode; it is also easier to deploy, but it can be less effective. In details, this are the differences from the Decrypt and scan mode:

  • No need to install certificates on the clients. This means that the traffic will not be decrypted.
  • As a consequence, there will be no antivirus check on the HTTPS pages.
  • When a page is blocked by the proxy, the browser will receive a Connection refused error message.
  • Whitelists and Blacklists for both the HTTPS and HTTP Proxies are defined in the Access policy and Web Filter tabs.

To correctly allow the URL Filtering mode to operate, the clients using the proxy must be configured to use the Endian UTM Appliance as their DNS server. If they do not, then the DNS Proxy must be enabled on the Endian UTM Appliance for all the zones that use the HTTP(S) Proxy.

When enabled as Decrypt and scan mode, squid will intercept all clients’ requests and forward them to the remote server, like in the case of HTTP requests. The only difference is that for HTTPS requests, an intermediate certificate is needed for the client to connect via HTTPS to the Endian UTM Appliance, which then can deliver the request, retrieve the remote resource, control it, and then send it to the client who requested it.

The following additional options are available for this mode:

Accept every certificate
This option allows the Endian UTM Appliance to automatically accept all the certificates from the remote server, even those that are not valid or outdated.
Forward HTTPS connections directly to the Upstream proxy

When this option is used, the HTTPS traffic will be managed directly by the upstream proxy, otherwise it is managed by the Endian UTM Appliance.

Note

This option only works if an upstream proxy has been defined in the upstream proxy (See Menubar ‣ Proxy ‣ HTTP ‣ Configuration ‣ Upstream proxy).

Bypass HTTPS proxy for destinations
Write in the textfield the IP address or domain names of remote web sites that should be not be checked by the HTTPS proxy, one per line.

The two panels at the bottom are used only for the Decrypt and scan mode and allow to manage the certificate that will be used by the Endian UTM Appliance.

Warning

The upload or the creation of a new certificate implies to invalidate any previously uploaded or created certificate. It will also be necessary to deploy the new certificate to all the clients.

Upload proxy certificate
To use an existent certificate, click on Browse…, choose the certificate on the local hard disk, then click on Upload to copy the certificate to the Endian UTM Appliance.
Create a new certificate
To create a new certificate from scratch, click on this button. A confirmation dialog box appears, requiring a confirmation. Click on OK to proceed or on Cancel to close the dialog box and go back.

After the certificate has been uploaded or created, a new option in the form of a hyperlink will appear next to the Upload proxy certificate label:

Download
Click this hyperlink to download the certificate, which will be needed by the the clients.

See also

In the knowledge base these tutorials are available:

How to set up the HTTPS proxy (only decrypt and scan mode),

URL Filtering For The HTTPS Proxy and

How to access HSTS-enabled sites

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