Secure Mobile Users with an Explicit Proxy

Secure Prisma Access mobile users by creating an Explicit Proxy and using a PAC file.
To secure mobile users with an Explicit Proxy, complete the following steps.
Before you configure Explicit Proxy guidelines, be aware of how explicit proxy works and how explicit proxy identifies users, go through the planning checklist, and learn how to set up the Explicit Proxy PAC file.
  1. Configure SAML authentication, including configuring a
    SAML Identity Provider
    and an
    Authentication Profile
    , for Prisma Access. You specify the authentication profile you create in a later step.
    Use the following guidelines when configuring authentication for the IdP and in Panorama:
    • Panorama Guidelines:
      • Be sure that you configure the authentication profile under the
        Explicit_Proxy_Template
        .
      • Use
        mail
        as the user attribute in the IdP server profile and in the
        Authentication Profile
        on Panorama.
      • Explicit Proxy does not support
        Sign SAML Message to IdP
        in the SAML Identity Provider Server Profile.
      • When you configure the Cloud Identity Engine to retrieve user and group mapping information, use
        mail
        or
        userPrincipalName
        as the
        SamAccountName
        in Group Mapping.
      • When configuring
        Group Mapping Settings
        during Explicit Proxy setup, use the same Directory Attribute for Primary Username and email, or Prisma Access does not accurately reflect user counts. For example, given the following user profile:
        sAMAccountName: muser Netbios: example userPrincipalName: muser@example.com mail: mobile.user@example.com
        If, in the Cloud Identity Engine configuration, you use a
        Primary Username
        of
        userPrincipalName
        and an
        E-Mail
        of
        mail
        , the user information that Cortex Data Lake returns in traffic logs and the user information that the ACS returns in authentication logs will be different. In this example, ACS sends the
        mail
        attribute (mobile.user@example.com) to the authentication logs and Cortex Data Lake sends the
        userPrincipalName
        attribute (muser@example.com) to the traffic logs. As a result of this mismatch, your user count will not be accurate in the
        Current Users
        and
        Users (Last 90 days)
        fields when checking the Explicit Proxy status in the Status (
        Panorama
        Cloud Services
        Status
        Status
        page. For this reason, use the same directory attribute for
        Primary Username
        and
        E-Mail
        (for example,
        mail
        ) when specifying
        Group Mapping Settings
        .
      • When using Panorama to manage Prisma Access, the Cloud Identity Engine does not auto-populate user and group information in security policy rules.
    • IdP Guidelines:
      • Use the following URLs when configuring SAML:
        SAML Assertion Consumer Service
        URL:
        https://global.acs.prismaaccess.com/saml/acs
        Entity ID
        URL:
        https://global.acs.prismaaccess.com/saml/metadata
      • If you use Okta as the IdP, use
        mail
        as the login username in the Okta profile.
      • Enter a single sign on URL of
        global.acs.prismaaccess.com
        .
      • Single Logout (SLO) is not supported.
      • To troubleshoot IdP authentication issues, use the IdP’s monitoring and troubleshooting capabilities. The ACS does not log IdP authentication failures.
      • When creating an
        Authentication Profile
        for the SAML IdP, in the
        Advanced
        tab, select
        all
        in the
        Allow List
        or Explicit Proxy will not be able to retrieve group mapping.
  2. Configure Explicit Proxy settings.
    1. Select
      Panorama
      Cloud Services
      Configuration
      Mobile Users—Explicit Proxy
      and click the gear icon to edit Explicit Proxy
      Settings
      .
    2. In the
      Settings
      tab, edit the following settings:
      • (
        Optional
        ) In the Templates section,
        Add
        the template or templates that contains the configuration you want to push for Explicit Proxy.
        By default, Prisma Access creates a new template stack
        Explicit_Proxy_Template_Stack
        and a new template
        Explicit_Proxy_Template
        . If you have existing settings you want to import, import them now. If you are starting with a new Explicit Proxy configuration, make sure that you are using this template when you create and edit your
        Network
        and
        Device
        settings in Panorama.
        You can
        Add
        more than one existing template to the stack and then order them appropriately using
        Move Up
        and
        Move Down
        . Panorama evaluates the templates in the stack from top to bottom, and settings in templates that are higher in the stack take priority over the same settings specified in templates that are lower in the stack. You cannot move the default
        Explicit_Proxy_Template
        from the top of the stack; this prevents you from overriding any required Explicit Proxy settings.
      • In the Device Group section, select the
        Parent Device Group
        that contains the configuration settings you want to push for the Explicit Proxy, or leave the parent device group as
        Shared
        to use the Prisma Access device group shared hierarchy. The
        Device Group Name
        cannot be changed.
      • (
        Optional
        ) Specify a
        Master Device
        .
        Explicit Proxy uses the Cloud Identity Engine to retrieve user and group mapping information. The Cloud Identity Engine does not auto-populate user and group information to security policy rules and to Panorama. To simplify rule creation based on user and group information, you can associate an on-premises or VM-series next generation firewall using a master device.
      • In the License Allocation section, specify the number of mobile users to allocate for Explicit Proxy.
    3. In the
      Group Mapping Settings
      tab,
      Enable Directory Sync Integration
      (now known as the Cloud Identity Engine) to configure Prisma Access to use the Cloud Identity Engine to retrieve user and group information.
      You use the Cloud Identity Engine to populate user and group mapping information for an Explicit Proxy deployment. To configure the Cloud Identity Engine, you set up the Cloud Identity Engine on your AD and associate the Panorama that manages Prisma Access with the Cloud Identity Engine in the hub; then, set up the Cloud Identity Engine in Prisma Access.
      Enter
      mail
      for the Directory Attribute in the
      Primary Username
      field and
      mail
      for the
      E-Mail
      field.
    4. Click
      OK
      when finished.
  3. In the
    Authentication Settings
    tab, configure decryption, X-Authenticated-User (XAU), and authentication settings.
    1. Configure your settings for decrypted traffic.
      • Select
        Decrypt traffic that matches existing decryption rules; for undecrypted traffic, allow traffic only from known IPs registered by authenticated users
        to configure the following decryption rules:
        • Traffic that matches decryption policy rules you have configured with an
          Action
          to
          Decrypt
          or
          Decrypt and Forward
          will be decrypted.
          If a user accesses an undecrypted HTTPS site, and a user has not yet authenticated to Explicit Proxy from that IP address, the user is blocked. However, the user can access a decrypted site, complete authentication, and then access undecrypted sites.
        • Undecrypted traffic is allowed from IP addresses from which mobile user have already authenticated.
        Explicit Proxy requires decryption to authenticate users. Enter the domains that can be decrypted in a custom URL category; then, specify those categories in
        If Authentication traffic is forwarded through Explicit Proxy, specify the domains used in the authentication flow
        .
        Only add the domains that are required for authentication to the Custom URL category you specify, including all ACS and IdP FQDNs. You must add authentication URLs to the Custom URL category, even if you have added them to a decryption policy.
      • To allow all traffic to be decrypted, select
        Decrypt all traffic (Overrides existing decryption rules)
        .
        If you choose this radio button, ensure that:
        • You do not have exceptions in your decryption policy.
        • You are applying source IP address-based restrictions in your security policy.
        Failing to follow these recommendations enables the abuse of Explicit Proxy as an open proxy that can be widely misused as a forwarding service for conducting denial of service attacks.
        • You have at least one SSL Forward Proxy certificate specified as a
          Forward Trust Certificate
          .
          If you do not have a forward trust certificate, create one on Panorama; then,
          Commit and Push
          your changes to Prisma Access. Failure to have a forward trust certificate will cause a commit error when you commit your Explicit Proxy changes.
    2. (
      Optional
      ) If you want to allow traffic from specific IP addresses to use XAU for authentication, create an address object and specify the IP addresses that will use XAU for authentication; then,
      Add
      the address object in the
      Trusted Source Address
      field.
      This option is useful if you are using proxy chaining from a third-party proxy to Explicit Proxy, users have authenticated in that proxy, and the proxy uses XAU headers.
      XAU headers are the only HTTP headers supported for Explicit Proxy header ingestion. X-Forwarded-For (XFF) headers are not supported.
      Make sure that the address object uses IP addresses.
    3. (
      Optional
      ) Specify settings for privacy-sensitive websites by creating security policy rules for those sites, then specifying the
      Security Policy
      or policies for those sites in the
      Enforce Authentication Only
      area.
      For any websites you specify in the in the
      Security Policy
      or policies you add, Explicit Proxy decrypts the websites based on the decryption policies, but does not inspect or log the decrypted traffic.
  4. Click
    Configure
    to configure Explicit Proxy setup.
    1. Specify an
      Explicit Proxy URL
      .
      By default, the name is
      proxyname
      .proxy.prismaaccess.com, where
      proxyname
      is the subdomain you specify, and uses port 8080. If you want to use your organization’s domain name in the Explicit Proxy URL (for example, thisproxy.proxy.mycompany.com), enter a CNAME record your organization’s domain.
      For example, to map a proxy URL named thisproxy.prismaaccess.com to a proxy named thisproxy.proxy.mycompany.com, you would add a CNAME of thisproxy.proxy.prismaaccess.com to the CNAME record in your organization’s domain.
    2. Specify an
      Authentication Profile
      and
      Cookie Lifetime
      .
      • Specify the SAML
        Authentication Profile
        you used in Step 1, or add a
        New
        authentication profile to use with Prisma Access.
        You must configure SAML authentication, including configuring a
        SAML Identity Provider
        (IdP) and an
        Authentication Profile
        , to use an Explicit Proxy.
      • (
        Optional
        ) Specify a
        Cookie Lifetime
        for the cookie that stores the users’ authentication credentials.
        Prisma Access caches the user’s credentials and stores them in the form of a cookie. To change the value, specify the length of time to use in Seconds, Minutes, Hours, or Days.
        To prevent issues with users not being able to download large files before the cookie lifetime expires, or the cookie expiring when users are accessing a single website for a long period of time, Palo Alto Networks recommends that you configure a Cookie Lifetime of at least one day. If Explicit Proxy users have a cookie lifetime expiration issue, they can browse to a different website to re-authenticate to ACS and refresh the ACS cookie.
        If you are downloading a file, and the file download takes longer than the
        Cookie Lifetime
        , the file download will terminate when the lifetime value expires. For this reason, consider using a longer
        Cookie Lifetime
        if you download large files that take a long time to download.
  5. Select the
    Locations
    and the regions associated with those locations where you want to deploy your Explicit Proxy for mobile users. Prisma Access adds a proxy node into each location you select.
    Explicit Proxy supports a subset of all Prisma Access locations. See Explicit Proxy Locations for the list of locations.
    The
    Locations
    tab displays a map. Highlighting the map shows the global regions (Americas, Europe, and Asia Pacific) and the locations available inside each region. Select a region, then select the locations you want to deploy in each region. Limiting your deployment to a single region provides more granular control over deployed regions and allows you to exclude regions as required by your policy or industry regulations. See Prisma Access Locations for the list of regions and locations. You can select a location in a region that is closest to your mobile users, or select a location as required by your policy or industry regulations.
    1. Click the
      Locations
      tab and select a region.
    2. Select one or more Explicit Proxy locations within your selected region using the map.
      Hovering your cursor over a location highlights it. White circles indicate an available location; green circles indicate that you have selected that location.
      In addition to the map view, you can view a list of regions and locations. Choose between the map and list view from the lower left corner. In the list view, the list displays regions sorted by columns, with all locations sorted by region. You can select
      All
      sites within a region (top of the dialog).
    3. Click
      OK
      to add the locations.
  6. Configure security policy rules to enforce your organization’s security policies.
    To make required configuration changes and to control the URLs that mobile users can access from Explicit Proxy, use security policies. Use the following guidelines and requirements when configuring your security policies:
    • Based on your business goals, create security policies for sanctioned internet and SaaS apps using App-ID and user groups that need access to those applications.
    • Attach security profiles to all security policy rules so that you can prevent both known and unknown threats following the security profile best practices.
  7. Commit your changes to Panorama and push the configuration changes to Prisma Access.
    1. Click
      Commit
      Commit and Push
      .
    2. Edit Selections
      and, in the
      Prisma Access
      tab, make sure that
      Explicit Proxy
      is selected in the
      Push Scope
      , then click
      OK
      .
    3. Click
      Commit and Push
      .
  8. Select the PAC file to use with Explicit Proxy.
    1. Select
      Panorama
      Cloud Services
      Configuration
      Mobile Users
      Explicit Proxy
      .
      Be sure that you enter a port of 8080 in the PAC file.
    2. Select the
      Connection Name
      for the Explicit Proxy setup you just configured.
    3. Enter the
      PAC (Proxy Auto-Configuration) File
      to use for Explicit Proxy.
      Be sure that you understand how PAC files work and how to modify them before you upload them to Prisma Access.
      Browse
      and upload the file.
      Prisma Access provides you with a sample PAC file; you can
      Download sample PAC file
      , change the values, and upload that file. See Set Up Your Explicit Proxy PAC File for PAC file requirements and guidelines as we as a description of the contents of the sample PAC file.

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