Deploying web servers and reverse proxies

Procedure

1. Install the httpd package:

   # dnf install httpd

   Copy to Clipboard Toggle word wrap

2. If you use firewalld, open the TCP port 80 in the local firewall:

   # firewall-cmd --permanent --add-port=80/tcp
   # firewall-cmd --reload

   Copy to Clipboard Toggle word wrap

3. Enable and start the httpd service:

   # systemctl enable --now httpd

   Copy to Clipboard Toggle word wrap

4. Optional: Add HTML files to the /var/www/html/ directory.

   Note

   When adding content to /var/www/html/, files and directories must be readable by the user under which httpd runs by default. The content owner can be either the root user and root user group, or another user or group of the administrator’s choice. If the content owner is the root user and root user group, the files must be readable by other users. The SELinux context for all the files and directories must be httpd_sys_content_t, which is applied by default to all content within the /var/www directory.

Procedure

1. Install the httpd package:

   # dnf install httpd

   Copy to Clipboard Toggle word wrap

2. Edit the /etc/httpd/conf/httpd.conf file:

   1. Append the following virtual host configuration for the example.com domain:

      <VirtualHost *:80>
          DocumentRoot "/var/www/example.com/"
          ServerName example.com
          CustomLog /var/log/httpd/example.com_access.log combined
          ErrorLog /var/log/httpd/example.com_error.log
      </VirtualHost>

      Copy to Clipboard Toggle word wrap

      These settings configure the following:

      • All settings in the <VirtualHost *:80> directive are specific for this virtual host.
      • DocumentRoot sets the path to the web content of the virtual host.

      • ServerName sets the domains for which this virtual host serves content.

        To set multiple domains, add the ServerAlias parameter to the configuration and specify the additional domains separated with a space in this parameter.

      • CustomLog sets the path to the access log of the virtual host.

      • ErrorLog sets the path to the error log of the virtual host.

        Note

        Apache uses the first virtual host found in the configuration also for requests that do not match any domain set in the ServerName and ServerAlias parameters. This also includes requests sent to the IP address of the server.

3. Append a similar virtual host configuration for the example.net domain:

   <VirtualHost *:80>
       DocumentRoot "/var/www/example.net/"
       ServerName example.net
       CustomLog /var/log/httpd/example.net_access.log combined
       ErrorLog /var/log/httpd/example.net_error.log
   </VirtualHost>

   Copy to Clipboard Toggle word wrap

4. Create the document roots for both virtual hosts:

   # mkdir /var/www/example.com/
   # mkdir /var/www/example.net/

   Copy to Clipboard Toggle word wrap

5. If you set paths in the DocumentRoot parameters that are not within /var/www/, set the httpd_sys_content_t context on both document roots:

   # semanage fcontext -a -t httpd_sys_content_t "/srv/example.com(/.*)?"
   # restorecon -Rv /srv/example.com/
   # semanage fcontext -a -t httpd_sys_content_t "/srv/example.net(/.\*)?"
   # restorecon -Rv /srv/example.net/

   Copy to Clipboard Toggle word wrap

   These commands set the httpd_sys_content_t context on the /srv/example.com/ and /srv/example.net/ directory.

   Note that you must install the policycoreutils-python-utils package to run the restorecon command.

6. If you use firewalld, open port 80 in the local firewall:

   # firewall-cmd --permanent --add-port=80/tcp
   # firewall-cmd --reload

   Copy to Clipboard Toggle word wrap

7. Enable and start the httpd service:

   # systemctl enable --now httpd

   Copy to Clipboard Toggle word wrap

Verification

1. Create a different example file in each virtual host’s document root:

   # echo "vHost example.com" > /var/www/example.com/index.html
   # echo "vHost example.net" > /var/www/example.net/index.html

   Copy to Clipboard Toggle word wrap
2. Use a browser and connect to http://example.com. The web server shows the example file from the example.com virtual host.
3. Use a browser and connect to http://example.net. The web server shows the example file from the example.net virtual host.

Procedure

1. Edit the /etc/httpd/conf/httpd.conf file and add the following settings to the <VirtualHost> directive for which you want to configure client authentication:

   <Directory "/var/www/html/Example/">
     SSLVerifyClient require
   </Directory>

   Copy to Clipboard Toggle word wrap

   The SSLVerifyClient require setting defines that the server must successfully validate the client certificate before the client can access the content in the /var/www/html/Example/ directory.

2. Restart the httpd service:

   # systemctl restart httpd

   Copy to Clipboard Toggle word wrap

Verification

1. Use the curl utility to access the https://example.com/Example/ URL without client authentication:

   $ curl https://example.com/Example/
   curl: (56) OpenSSL SSL_read: error:1409445C:SSL routines:ssl3_read_bytes:tlsv13 alert certificate required, errno 0

   Copy to Clipboard Toggle word wrap

   The error indicates that the web server requires a client certificate authentication.

2. Pass the client private key and certificate, as well as the CA certificate to curl to access the same URL with client authentication:

   $ curl --cacert ca.crt --key client.key --cert client.crt https://example.com/Example/

   Copy to Clipboard Toggle word wrap

   If the request succeeds, curl displays the index.html file stored in the /var/www/html/Example/ directory.

Procedure

1. Install the httpd-manual package:

   # dnf install httpd-manual

   Copy to Clipboard Toggle word wrap

2. Optional: By default, all clients connecting to the Apache HTTP Server can display the manual. To restrict access to a specific IP range, such as the 192.0.2.0/24 subnet, edit the /etc/httpd/conf.d/manual.conf file and add the Require ip 192.0.2.0/24 setting to the <Directory "/usr/share/httpd/manual"> directive:

   <Directory "/usr/share/httpd/manual">
   ...
       Require ip 192.0.2.0/24
   ...
   </Directory>

   Copy to Clipboard Toggle word wrap

3. Restart the httpd service:

   # systemctl restart httpd

   Copy to Clipboard Toggle word wrap

Verification

1. To display the Apache HTTP Server manual, connect with a web browser to http://host_name_or_IP_address/manual/

Procedure

1. Install the nginx package:

   • To install NGINX 1.20 as the initial version of this Application Stream from an RPM package:

     # dnf install nginx

     Copy to Clipboard Toggle word wrap
     Note

     If you have previously enabled an NGINX module stream, this command installs the NGINX version from the enabled stream.

   • To install an alternate later version of NGINX from a module stream:

     1. Display the available NGINX module streams:

        # dnf module list nginx
        ...
        rhel-AppStream
        Name        Stream        Profiles        Summary
        nginx       1.22          common [d]      nginx webserver
        ...
        Hint: [d]efault, [e]nabled, [x]disabled, [i]nstalled

        Copy to Clipboard Toggle word wrap

     2. Enable the selected stream:

        # dnf module enable nginx:stream_version

        Copy to Clipboard Toggle word wrap

     3. Install the nginx package:

        # dnf install nginx

        Copy to Clipboard Toggle word wrap

2. Open the ports on which NGINX should provide its service in the firewall. For example, to open the default ports for HTTP (port 80) and HTTPS (port 443) in firewalld, enter:

   # firewall-cmd --permanent --add-port={80/tcp,443/tcp}
   # firewall-cmd --reload

   Copy to Clipboard Toggle word wrap

3. Enable the nginx service to start automatically when the system boots:

   # systemctl enable nginx

   Copy to Clipboard Toggle word wrap

4. Optional: Start the nginx service:

   # systemctl start nginx

   Copy to Clipboard Toggle word wrap

   If you do not want to use the default configuration, skip this step, and configure NGINX accordingly before you start the service.

Verification

1. Use the dnf utility to verify that the nginx package is installed.

   • In case of the NGINX 1.20 RPM package:

     # dnf list installed nginx
     Installed Packages
     nginx.x86_64    1:1.20.1-4.el9       @rhel-AppStream

     Copy to Clipboard Toggle word wrap

   • In case of a selected NGINX module stream:

     # dnf list installed nginx
     Installed Packages
     nginx.x86_64    1:1.22.1-3.module+el9.2.0+17617+2f289c6c    @rhel-AppStream

     Copy to Clipboard Toggle word wrap

2. Ensure that the ports on which NGINX should provide its service are opened in the firewalld:

   # firewall-cmd --list-ports
   80/tcp 443/tcp

   Copy to Clipboard Toggle word wrap

3. Verify that the nginx service is enabled:

   # systemctl is-enabled nginx
   enabled

   Copy to Clipboard Toggle word wrap

Procedure

1. Edit the /etc/nginx/nginx.conf file:

   1. By default, the /etc/nginx/nginx.conf file already contains a catch-all configuration. If you have deleted this part from the configuration, re-add the following server block to the http block in the /etc/nginx/nginx.conf file:

      server {
          listen       80 default_server;
          listen       [::]:80 default_server;
          server_name  _;
          root         /usr/share/nginx/html;
      }

      Copy to Clipboard Toggle word wrap

      These settings configure the following:

      • The listen directive define which IP address and ports the service listens. In this case, NGINX listens on port 80 on both all IPv4 and IPv6 addresses. The default_server parameter indicates that NGINX uses this server block as the default for requests matching the IP addresses and ports.
      • The server_name parameter defines the host names for which this server block is responsible. Setting server_name to _ configures NGINX to accept any host name for this server block.
      • The root directive sets the path to the web content for this server block.

   2. Append a similar server block for the example.com domain to the http block:

      server {
          server_name  example.com;
          root         /var/www/example.com/;
          access_log   /var/log/nginx/example.com/access.log;
          error_log    /var/log/nginx/example.com/error.log;
      }

      Copy to Clipboard Toggle word wrap
      • The access_log directive defines a separate access log file for this domain.
      • The error_log directive defines a separate error log file for this domain.

   3. Append a similar server block for the example.net domain to the http block:

      server {
          server_name  example.net;
          root         /var/www/example.net/;
          access_log   /var/log/nginx/example.net/access.log;
          error_log    /var/log/nginx/example.net/error.log;
      }

      Copy to Clipboard Toggle word wrap

2. Create the root directories for both domains:

   # mkdir -p /var/www/example.com/
   # mkdir -p /var/www/example.net/

   Copy to Clipboard Toggle word wrap

3. Set the httpd_sys_content_t context on both root directories:

   # semanage fcontext -a -t httpd_sys_content_t "/var/www/example.com(/.*)?"
   # restorecon -Rv /var/www/example.com/
   # semanage fcontext -a -t httpd_sys_content_t "/var/www/example.net(/.\*)?"
   # restorecon -Rv /var/www/example.net/

   Copy to Clipboard Toggle word wrap

   These commands set the httpd_sys_content_t context on the /var/www/example.com/ and /var/www/example.net/ directories.

   Note that you must install the policycoreutils-python-utils package to run the restorecon commands.

4. Create the log directories for both domains:

   # mkdir /var/log/nginx/example.com/
   # mkdir /var/log/nginx/example.net/

   Copy to Clipboard Toggle word wrap

5. Restart the nginx service:

   # systemctl restart nginx

   Copy to Clipboard Toggle word wrap

Verification

1. Create a different example file in each virtual host’s document root:

   # echo "Content for example.com" > /var/www/example.com/index.html
   # echo "Content for example.net" > /var/www/example.net/index.html
   # echo "Catch All content" > /usr/share/nginx/html/index.html

   Copy to Clipboard Toggle word wrap
2. Use a browser and connect to http://example.com. The web server shows the example content from the /var/www/example.com/index.html file.
3. Use a browser and connect to http://example.net. The web server shows the example content from the /var/www/example.net/index.html file.
4. Use a browser and connect to http://IP_address_of_the_server. The web server shows the example content from the /usr/share/nginx/html/index.html file.

Procedure

1. Edit the /etc/nginx/nginx.conf file, and add the following server block to the http block in the configuration:

   server {
       listen              443 ssl;
       server_name         example.com;
       root                /usr/share/nginx/html;
       ssl_certificate     /etc/pki/tls/certs/example.com.crt;
       ssl_certificate_key /etc/pki/tls/private/example.com.key;
   }

   Copy to Clipboard Toggle word wrap

2. Optional: Starting with RHEL 9.3, you can use the ssl_pass_phrase_dialog directive to configure an external program that is called at nginx start for each encrypted private key. Add one of the following lines to the /etc/nginx/nginx.conf file:

   • To call an external program for each encrypted private key file, enter:

     ssl_pass_phrase_dialog exec:<path_to_program>;

     Copy to Clipboard Toggle word wrap

     NGINX calls this program with the following two arguments:

     • The server name specified in the server_name setting.
     • One of the following algorithms: RSA, DSA, EC, DH, or UNK if a cryptographic algorithm cannot be recognized.

   • If you want to manually enter a passphrase for each encrypted private key file, enter:

     ssl_pass_phrase_dialog builtin;

     Copy to Clipboard Toggle word wrap

     This is the default behavior if ssl_pass_phrase_dialog is not configured.

     Note

     The nginx service fails to start if you use this method but have at least one private key protected by a passphrase. In this case, use one of the other methods.

   • If you want systemd to prompt for the passphrase for each encrypted private key when you start the nginx service by using the systemctl utility, enter:

     ssl_pass_phrase_dialog exec:/usr/libexec/nginx-ssl-pass-dialog;

     Copy to Clipboard Toggle word wrap

3. For security reasons, configure that only the root user can access the private key file:

   # chown root:root /etc/pki/tls/private/example.com.key
   # chmod 600 /etc/pki/tls/private/example.com.key

   Copy to Clipboard Toggle word wrap
   Warning

   If the private key was accessed by unauthorized users, revoke the certificate, create a new private key, and request a new certificate. Otherwise, the TLS connection is no longer secure.

4. Restart the nginx service:

   # systemctl restart nginx

   Copy to Clipboard Toggle word wrap

Procedure

1. Edit the /etc/nginx/nginx.conf file and add the following settings to the server block that should provide the reverse proxy:

   location /example {
       proxy_pass https://example.com;
   }

   Copy to Clipboard Toggle word wrap

   The location block defines that NGINX passes all requests in the /example directory to https://example.com.

2. Set the httpd_can_network_connect SELinux boolean parameter to 1 to configure that SELinux allows NGINX to forward traffic:

   # setsebool -P httpd_can_network_connect 1

   Copy to Clipboard Toggle word wrap

3. Restart the nginx service:

   # systemctl restart nginx

   Copy to Clipboard Toggle word wrap

Procedure

1. Edit the /etc/nginx/nginx.conf file and add the following settings:

   http {
       upstream backend {
           least_conn;
           server server1.example.com;
           server server2.example.com;
           server server3.example.com backup;
       }
   
       server {
           location / {
               proxy_pass http://backend;
           }
       }
   }

   Copy to Clipboard Toggle word wrap

   The least_conn directive in the host group named backend defines that NGINX sends requests to server1.example.com or server2.example.com, depending on which host has the least number of active connections. NGINX uses server3.example.com only as a backup in case that the other two hosts are not available.

   With the proxy_pass directive set to http://backend, NGINX acts as a reverse proxy and uses the backend host group to distribute requests based on the settings of this group.

   Instead of the least_conn load balancing method, you can specify:

   • No method to use round robin and distribute requests evenly across servers.
   • ip_hash to send requests from one client address to the same server based on a hash calculated from the first three octets of the IPv4 address or the whole IPv6 address of the client.
   • hash to determine the server based on a user-defined key, which can be a string, a variable, or a combination of both. The consistent parameter configures that NGINX distributes requests across all servers based on the user-defined hashed key value.
   • random to send requests to a randomly selected server.

2. Restart the nginx service:

   # systemctl restart nginx

   Copy to Clipboard Toggle word wrap

Procedure

1. Install the squid package:

   # dnf install squid

   Copy to Clipboard Toggle word wrap

2. Edit the /etc/squid/squid.conf file:

   1. Adapt the localnet access control lists (ACL) to match the IP ranges that should be allowed to use the proxy:

      acl localnet src 192.0.2.0/24
      acl localnet 2001:db8:1::/64

      Copy to Clipboard Toggle word wrap

      By default, the /etc/squid/squid.conf file contains the http_access allow localnet rule that allows using the proxy from all IP ranges specified in localnet ACLs. Note that you must specify all localnet ACLs before the http_access allow localnet rule.

      Important

      Remove all existing acl localnet entries that do not match your environment.

   2. The following ACL exists in the default configuration and defines 443 as a port that uses the HTTPS protocol:

      acl SSL_ports port 443

      Copy to Clipboard Toggle word wrap

      If users should be able to use the HTTPS protocol also on other ports, add an ACL for each of these port:

      acl SSL_ports port port_number

      Copy to Clipboard Toggle word wrap

   3. Update the list of acl Safe_ports rules to configure to which ports Squid can establish a connection. For example, to configure that clients using the proxy can only access resources on port 21 (FTP), 80 (HTTP), and 443 (HTTPS), keep only the following acl Safe_ports statements in the configuration:

      acl Safe_ports port 21
      acl Safe_ports port 80
      acl Safe_ports port 443

      Copy to Clipboard Toggle word wrap

      By default, the configuration contains the http_access deny !Safe_ports rule that defines access denial to ports that are not defined in Safe_ports ACLs.

   4. Configure the cache type, the path to the cache directory, the cache size, and further cache type-specific settings in the cache_dir parameter:

      cache_dir ufs /var/spool/squid 10000 16 256

      Copy to Clipboard Toggle word wrap

      With these settings:

      • Squid uses the ufs cache type.
      • Squid stores its cache in the /var/spool/squid/ directory.
      • The cache grows up to 10000 MB.
      • Squid creates 16 level-1 sub-directories in the /var/spool/squid/ directory.

      • Squid creates 256 sub-directories in each level-1 directory.

        If you do not set a cache_dir directive, Squid stores the cache in memory.

3. If you set a different cache directory than /var/spool/squid/ in the cache_dir parameter:

   1. Create the cache directory:

      # mkdir -p path_to_cache_directory

      Copy to Clipboard Toggle word wrap

   2. Configure the permissions for the cache directory:

      # chown squid:squid path_to_cache_directory

      Copy to Clipboard Toggle word wrap

   3. If you run SELinux in enforcing mode, set the squid_cache_t context for the cache directory:

      # semanage fcontext -a -t squid_cache_t "path_to_cache_directory(/.*)?"
      # restorecon -Rv path_to_cache_directory

      Copy to Clipboard Toggle word wrap

      If the semanage utility is not available on your system, install the policycoreutils-python-utils package.

4. Open the 3128 port in the firewall:

   # firewall-cmd --permanent --add-port=3128/tcp
   # firewall-cmd --reload

   Copy to Clipboard Toggle word wrap

5. Enable and start the squid service:

   # systemctl enable --now squid

   Copy to Clipboard Toggle word wrap

Procedure

1. Install the squid package:

   # dnf install squid

   Copy to Clipboard Toggle word wrap

2. Edit the /etc/squid/squid.conf file:

   1. To configure the basic_ldap_auth helper utility, add the following configuration entry to the top of /etc/squid/squid.conf:

      auth_param basic program /usr/lib64/squid/basic_ldap_auth -b "cn=users,cn=accounts,dc=example,dc=com" -D "uid=proxy_user,cn=users,cn=accounts,dc=example,dc=com" -W /etc/squid/ldap_password -f "(&(objectClass=person)(uid=%s))" -ZZ -H ldap://ldap_server.example.com:389

      Copy to Clipboard Toggle word wrap

      The following describes the parameters passed to the basic_ldap_auth helper utility in the example above:

      • -b base_DN sets the LDAP search base.
      • -D proxy_service_user_DN sets the distinguished name (DN) of the account Squid uses to search for the authenticating user in the directory.
      • -W path_to_password_file sets the path to the file that contains the password of the proxy service user. Using a password file prevents that the password is visible in the operating system’s process list.

      • -f LDAP_filter specifies the LDAP search filter. Squid replaces the %s variable with the user name provided by the authenticating user.

        The (&(objectClass=person)(uid=%s)) filter in the example defines that the user name must match the value set in the uid attribute and that the directory entry contains the person object class.

      • -ZZ enforces a TLS-encrypted connection over the LDAP protocol using the STARTTLS command. Omit the -ZZ in the following situations:

        • The LDAP server does not support encrypted connections.
        • The port specified in the URL uses the LDAPS protocol.
      • The -H LDAP_URL parameter specifies the protocol, the host name or IP address, and the port of the LDAP server in URL format.

   2. Add the following ACL and rule to configure that Squid allows only authenticated users to use the proxy:

      acl ldap-auth proxy_auth REQUIRED
      http_access allow ldap-auth

      Copy to Clipboard Toggle word wrap
      Important

      Specify these settings before the http_access deny all rule.

   3. Remove the following rule to disable bypassing the proxy authentication from IP ranges specified in localnet ACLs:

      http_access allow localnet

      Copy to Clipboard Toggle word wrap

   4. The following ACL exists in the default configuration and defines 443 as a port that uses the HTTPS protocol:

      acl SSL_ports port 443

      Copy to Clipboard Toggle word wrap

      If users should be able to use the HTTPS protocol also on other ports, add an ACL for each of these port:

      acl SSL_ports port port_number

      Copy to Clipboard Toggle word wrap

   5. Update the list of acl Safe_ports rules to configure to which ports Squid can establish a connection. For example, to configure that clients using the proxy can only access resources on port 21 (FTP), 80 (HTTP), and 443 (HTTPS), keep only the following acl Safe_ports statements in the configuration:

      acl Safe_ports port 21
      acl Safe_ports port 80
      acl Safe_ports port 443

      Copy to Clipboard Toggle word wrap

      By default, the configuration contains the http_access deny !Safe_ports rule that defines access denial to ports that are not defined in Safe_ports ACLs.

   6. Configure the cache type, the path to the cache directory, the cache size, and further cache type-specific settings in the cache_dir parameter:

      cache_dir ufs /var/spool/squid 10000 16 256

      Copy to Clipboard Toggle word wrap

      With these settings:

      • Squid uses the ufs cache type.
      • Squid stores its cache in the /var/spool/squid/ directory.
      • The cache grows up to 10000 MB.
      • Squid creates 16 level-1 sub-directories in the /var/spool/squid/ directory.

      • Squid creates 256 sub-directories in each level-1 directory.

        If you do not set a cache_dir directive, Squid stores the cache in memory.

3. If you set a different cache directory than /var/spool/squid/ in the cache_dir parameter:

   1. Create the cache directory:

      # mkdir -p path_to_cache_directory

      Copy to Clipboard Toggle word wrap

   2. Configure the permissions for the cache directory:

      # chown squid:squid path_to_cache_directory

      Copy to Clipboard Toggle word wrap

   3. If you run SELinux in enforcing mode, set the squid_cache_t context for the cache directory:

      # semanage fcontext -a -t squid_cache_t "path_to_cache_directory(/.*)?"
      # restorecon -Rv path_to_cache_directory

      Copy to Clipboard Toggle word wrap

      If the semanage utility is not available on your system, install the policycoreutils-python-utils package.

4. Store the password of the LDAP service user in the /etc/squid/ldap_password file, and set appropriate permissions for the file:

   # echo "password" > /etc/squid/ldap_password
   # chown root:squid /etc/squid/ldap_password
   # chmod 640 /etc/squid/ldap_password

   Copy to Clipboard Toggle word wrap

5. Open the 3128 port in the firewall:

   # firewall-cmd --permanent --add-port=3128/tcp
   # firewall-cmd --reload

   Copy to Clipboard Toggle word wrap

6. Enable and start the squid service:

   # systemctl enable --now squid

   Copy to Clipboard Toggle word wrap

1. Manually start the helper utility with the same settings you used in the auth_param parameter:

   # /usr/lib64/squid/basic_ldap_auth -b "cn=users,cn=accounts,dc=example,dc=com" -D "uid=proxy_user,cn=users,cn=accounts,dc=example,dc=com" -W /etc/squid/ldap_password -f "(&(objectClass=person)(uid=%s))" -ZZ -H ldap://ldap_server.example.com:389

   Copy to Clipboard Toggle word wrap

2. Enter a valid user name and password, and press Enter:

   user_name password

   Copy to Clipboard Toggle word wrap

   If the helper utility returns OK, authentication succeeded.

Procedure

1. Install the following packages:

   # dnf install squid krb5-workstation

   Copy to Clipboard Toggle word wrap

2. Authenticate as the AD domain administrator:

   # kinit administrator@AD.EXAMPLE.COM

   Copy to Clipboard Toggle word wrap

3. Create a keytab for Squid, store it in the /etc/squid/HTTP.keytab file and add the HTTP service principal to the keytab:

   # export KRB5_KTNAME=FILE:/etc/squid/HTTP.keytab
   # net ads keytab CREATE -U administrator
   # net ads keytab ADD HTTP -U administrator

   Copy to Clipboard Toggle word wrap

4. Optional: If system is initially joined to the AD domain with realm (via adcli), use following instructions to add HTTP principal and create a keytab file for squid:

   1. Add the HTTP service principal to the default keytab file /etc/krb5.keytab and verify:

      # adcli update -vvv --domain=ad.example.com --computer-name=PROXY --add-service-principal="HTTP/proxy.ad.example.com" -C
      # klist -kte /etc/krb5.keytab | grep -i HTTP

      Copy to Clipboard Toggle word wrap

   2. Load the /etc/krb5.keytab file, remove all service principals except HTTP, and save the remaining principals into the /etc/squid/HTTP.keytab file:

      # ktutil
      ktutil:  rkt /etc/krb5.keytab
      ktutil:  l -e
      slot | KVNO | Principal
      -----------------------------------------------------------------------------
      1 |    2 |            PROXY$@AD.EXAMPLE.COM (aes128-cts-hmac-sha1-96)
      2 |    2 |            PROXY$@AD.EXAMPLE.COM (aes256-cts-hmac-sha1-96)
      3 |    2 |         host/PROXY@AD.EXAMPLE.COM (aes128-cts-hmac-sha1-96)
      4 |    2 |         host/PROXY@AD.EXAMPLE.COM (aes256-cts-hmac-sha1-96)
      5 |    2 | host/proxy.ad.example.com@AD.EXAMPLE.COM (aes128-cts-hmac-sha1-96)
      6 |    2 | host/proxy.ad.example.com@AD.EXAMPLE.COM (aes256-cts-hmac-sha1-96)
      7 |    2 | HTTP/proxy.ad.example.com@AD.EXAMPLE.COM (aes128-cts-hmac-sha1-96)
      8 |    2 | HTTP/proxy.ad.example.com@AD.EXAMPLE.COM (aes256-cts-hmac-sha1-96)

      Copy to Clipboard Toggle word wrap

      In the interactive shell of ktutil, you can use the different options, until all unwanted principals are removed from keytab, for example:

      ktutil:  delent 1

      Copy to Clipboard Toggle word wrap

      ktutil:  l -e
      
      slot | KVNO | Principal
      -------------------------------------------------------------------------------
      1 |   2 | HTTP/proxy.ad.example.com@AD.EXAMPLE.COM (aes128-cts-hmac-sha1-96)
      2 |   2 | HTTP/proxy.ad.example.com@AD.EXAMPLE.COM (aes256-cts-hmac-sha1-96)
      
      ktutil:  wkt /etc/squid/HTTP.keytab
      ktutil:  q

      Copy to Clipboard Toggle word wrap
      Warning

      The keys in /etc/krb5.keytab might get updated if SSSD or Samba/winbind will update the machine account password. After the update, the key in /etc/squid/HTTP.keytab will stop working, and you will need to perform the ktutil steps again to copy the new keys into the keytab.

5. Set the owner of the keytab file to the squid user:

   # chown squid /etc/squid/HTTP.keytab

   Copy to Clipboard Toggle word wrap

6. Optional: Verify that the keytab file contains the HTTP service principal for the fully-qualified domain name (FQDN) of the proxy server:

   # klist -k /etc/squid/HTTP.keytab
   Keytab name: FILE:/etc/squid/HTTP.keytab
   KVNO Principal
   ---- ---------------------------------------------------
   ...
      2 HTTP/proxy.ad.example.com@AD.EXAMPLE.COM
   ...

   Copy to Clipboard Toggle word wrap

7. Edit the /etc/squid/squid.conf file:

   1. To configure the negotiate_kerberos_auth helper utility, add the following configuration entry to the top of /etc/squid/squid.conf:

      auth_param negotiate program /usr/lib64/squid/negotiate_kerberos_auth -k /etc/squid/HTTP.keytab -s HTTP/proxy.ad.example.com@AD.EXAMPLE.COM

      Copy to Clipboard Toggle word wrap

      The following describes the parameters passed to the negotiate_kerberos_auth helper utility in the example above:

      • -k file sets the path to the key tab file. Note that the squid user must have read permissions on this file.

      • -s HTTP/host_name@kerberos_realm sets the Kerberos principal that Squid uses.

        Optionally, you can enable logging by passing one or both of the following parameters to the helper utility:

      • -i logs informational messages, such as the authenticating user.

      • -d enables debug logging.

        Squid logs the debugging information from the helper utility to the /var/log/squid/cache.log file.

   2. Add the following ACL and rule to configure that Squid allows only authenticated users to use the proxy:

      acl kerb-auth proxy_auth REQUIRED
      http_access allow kerb-auth

      Copy to Clipboard Toggle word wrap
      Important

      Specify these settings before the http_access deny all rule.

   3. Remove the following rule to disable bypassing the proxy authentication from IP ranges specified in localnet ACLs:

      http_access allow localnet

      Copy to Clipboard Toggle word wrap

   4. The following ACL exists in the default configuration and defines 443 as a port that uses the HTTPS protocol:

      acl SSL_ports port 443

      Copy to Clipboard Toggle word wrap

      If users should be able to use the HTTPS protocol also on other ports, add an ACL for each of these port:

      acl SSL_ports port port_number

      Copy to Clipboard Toggle word wrap

   5. Update the list of acl Safe_ports rules to configure to which ports Squid can establish a connection. For example, to configure that clients using the proxy can only access resources on port 21 (FTP), 80 (HTTP), and 443 (HTTPS), keep only the following acl Safe_ports statements in the configuration:

      acl Safe_ports port 21
      acl Safe_ports port 80
      acl Safe_ports port 443

      Copy to Clipboard Toggle word wrap

      By default, the configuration contains the http_access deny !Safe_ports rule that defines access denial to ports that are not defined in Safe_ports ACLs.

   6. Configure the cache type, the path to the cache directory, the cache size, and further cache type-specific settings in the cache_dir parameter:

      cache_dir ufs /var/spool/squid 10000 16 256

      Copy to Clipboard Toggle word wrap

      With these settings:

      • Squid uses the ufs cache type.
      • Squid stores its cache in the /var/spool/squid/ directory.
      • The cache grows up to 10000 MB.
      • Squid creates 16 level-1 sub-directories in the /var/spool/squid/ directory.

      • Squid creates 256 sub-directories in each level-1 directory.

        If you do not set a cache_dir directive, Squid stores the cache in memory.

8. If you set a different cache directory than /var/spool/squid/ in the cache_dir parameter:

   1. Create the cache directory:

      # mkdir -p path_to_cache_directory

      Copy to Clipboard Toggle word wrap

   2. Configure the permissions for the cache directory:

      # chown squid:squid path_to_cache_directory

      Copy to Clipboard Toggle word wrap

   3. If you run SELinux in enforcing mode, set the squid_cache_t context for the cache directory:

      # semanage fcontext -a -t squid_cache_t "path_to_cache_directory(/.*)?"
      # restorecon -Rv path_to_cache_directory

      Copy to Clipboard Toggle word wrap

      If the semanage utility is not available on your system, install the policycoreutils-python-utils package.

9. Open the 3128 port in the firewall:

   # firewall-cmd --permanent --add-port=3128/tcp
   # firewall-cmd --reload

   Copy to Clipboard Toggle word wrap

10. Enable and start the squid service:

    # systemctl enable --now squid

    Copy to Clipboard Toggle word wrap

Troubleshooting steps

1. Obtain a Kerberos ticket for the AD account:

   # kinit user@AD.EXAMPLE.COM

   Copy to Clipboard Toggle word wrap

2. Optional: Display the ticket:

   # klist

   Copy to Clipboard Toggle word wrap

3. Use the negotiate_kerberos_auth_test utility to test the authentication:

   # /usr/lib64/squid/negotiate_kerberos_auth_test proxy.ad.example.com

   Copy to Clipboard Toggle word wrap

   If the helper utility returns a token, the authentication succeeded:

   Token: YIIFtAYGKwYBBQUCoIIFqDC...

   Copy to Clipboard Toggle word wrap

Procedure

1. Edit the /etc/squid/squid.conf file and add the following settings:

   acl domain_deny_list dstdomain "/etc/squid/domain_deny_list.txt"
   http_access deny all domain_deny_list

   Copy to Clipboard Toggle word wrap
   Important

   Add these entries before the first http_access allow statement that allows access to users or clients.

2. Create the /etc/squid/domain_deny_list.txt file and add the domains you want to block. For example, to block access to example.com including subdomains and to block example.net, add:

   .example.com
   example.net

   Copy to Clipboard Toggle word wrap
   Important

   If you referred to the /etc/squid/domain_deny_list.txt file in the squid configuration, this file must not be empty. If the file is empty, Squid fails to start.

3. Restart the squid service:

   # systemctl restart squid

   Copy to Clipboard Toggle word wrap

Procedure

1. Edit the /etc/squid/squid.conf file:

   • To set the port on which the Squid service listens, set the port number in the http_port parameter. For example, to set the port to 8080, set:

     http_port 8080

     Copy to Clipboard Toggle word wrap

   • To configure on which IP address the Squid service listens, set the IP address and port number in the http_port parameter. For example, to configure that Squid listens only on the 192.0.2.1 IP address on port 3128, set:

     http_port 192.0.2.1:3128

     Copy to Clipboard Toggle word wrap

     Add multiple http_port parameters to the configuration file to configure that Squid listens on multiple ports and IP addresses:

     http_port 192.0.2.1:3128
     http_port 192.0.2.1:8080

     Copy to Clipboard Toggle word wrap

2. If you configured that Squid uses a different port as the default (3128):

   1. Open the port in the firewall:

      # firewall-cmd --permanent --add-port=port_number/tcp
      # firewall-cmd --reload

      Copy to Clipboard Toggle word wrap

   2. If you run SELinux in enforcing mode, assign the port to the squid_port_t port type definition:

      # semanage port -a -t squid_port_t -p tcp port_number

      Copy to Clipboard Toggle word wrap

      If the semanage utility is not available on your system, install the policycoreutils-python-utils package.

3. Restart the squid service:

   # systemctl restart squid

   Copy to Clipboard Toggle word wrap