AFP548

Squid Server using LDAP authentication

fherbert

Add more control to your Squid proxy server by adding LDAP authentication

Using plugable authentication modules and Open Directory you can easily limit who is able to surf the web.The following are the steps I used to install squid proxy server on an OS X.3.5 Open Directory server and enable Squid to use a group created in Workgroup Manager (named “internet”) in order to authenticate and authorize users, giving only users in that group access to the internet. Additionally, I have added the steps I followed to install Dansguardian which are very minimal since Dave Lopata (pkg maintainer) has created an installer package.

Steps to install Squid proxy Server on OS X:

  1. Download squid-2.5.STABLE6.
  2. Download the PAM source code.
  3. Extract the file, and copy the libpam/include/security directory to /usr/include/ directory.
  4. Configure, compile and install squid:
./configure -prefix=/usr/local/squid -enable-basic-auth-helpers=PAM
make
make install
  1. Create the startupitem for squid:
mkdir /Library/StartupItems/squid
cd /Library/StartupItems/squid
  1. Create a new file named StartupParameters.plist with the following contents:
{
Description = "Squid Proxy Server";
Provides = ("squid");
Requires = ("Resolver");
OrderPreference = "None";
Messages =
{
start = "Starting squid server";
stop = "Stopping squid server";
restart = "Restarting squid server";
};
  1. Create a new file named squid with the following contents:
#!/bin/bash

. /etc/rc.common

StartService ()
{
if [ ${SQUID:=-NO-} = -YES- ]; then
ConsoleMessage "Starting Squid Server"
/usr/local/squid/sbin/squid -D
fi
}

StopService ()
{
ConsoleMessage "Stopping Squid Server"
/usr/local/squid/sbin/squid -k kill
}

RestartService () { StopService; StartService; }

RunService "$1"
  1. Ensure the following permissions are set on the two files: 
rwxr-xr-x StartupParameters.plist
rwxr-xr-x squid

Now Install PAM_LDAP module:

  1. Download the pam_ldap source code.
  2. Extract the file and change into the a directory 
guntar -xzvf pam_ldap.tgz
cd pam_ldap-173
  1. Edit the file pam_auth.c

Find the section that starts with (around line 3670)

/* group auth, per Chris's pam_ldap_auth module */
if (session->conf->groupdn != NULL)
{
rc = ldap_compare_s (session->ld,
session->conf->groupdn,
session->conf->groupattr, session->info->userdn);

Change the last line (line number 3675) so that it looks like this:

/* group auth, per Chris's pam_ldap_auth module */
if (session->conf->groupdn != NULL)
{
rc = ldap_compare_s (session->ld,
session->conf->groupdn,
session->conf->groupattr, session->info->username);
  1. Now you will need to compile and install the pam_auth module. 
./configure
make

Once you have completed the make, you will need to modify the Makefile in order for the install command to be executed correctly.

Edit the Makefile by looking for the 2 lines that look something like this:

$(INSTALL_PROGRAM) -o root -g root pam_ldap.so $(DESTDIR)$(libdir)/security/pam_ldap.so.1
$(INSTALL_DATA) -o root -g root $(srcdir)/ldap.conf $(DESTDIR)$(sysconfdir)/ldap.conf;

Replace the word “root” in the above two lines with the number “0” (this is because the install command provided with OS X looks for a UID number not name) then save and exit the file and then run the “make” command.

make install

Now copy the pam_ldap files to the correct place for os x

cd /lib/security
mv * /usr/lib/pam/
cd ..
rm -rf lib/security

Change to the /etc directory, copy the ldap.conf file to ldap.squid.conf and modify the ldap.squid.conf to match your network settings, making sure the following at least are set:

host 127.0.0.1
base dc=your,dc=domain,dc=name
pam_groupdn cn=internet,cn=groups,dc=your,dc=domain,dc=name
pam_member_attribute memberUid

Create a file called “squid” in /etc/pam.d/ directory and insert the following:

#%PAM-1.0
auth required /usr/lib/pam/pam_ldap.so config=/etc/ldap.squid.conf
account required /usr/lib/pam/pam_ldap.so config=/etc/ldap.squid.conf

Now test that the pam_auth module works correctly.

/usr/local/squid/libexec/pam_auth

Enter a valid username and password (using a user that exists in the internet group you specified in the ldap.squid.conf file above).

If the authentication succeeds, you should be greeted with “OK”, if the username or password was incorrect or does not exists on the server, you will be greeted with “ERR”, if the username exists on the server but does not exists in the internet group you have specified, you will be greeted with “ERROR: Unexpected PAM conversation. ‘You must be a memberUid of cn=internet,cn=groups,dc=your,dc=domain,dc=name to login.’ ERR”

That’s all the configuration needed for pam_ldap authentication, now you will need to modify you /usr/local/squid/etc/squid.conf file to use the pam_auth for authentication).

Configuring Squid

  1. Edit your /usr/local/squid/etc/squid.conf to include at least the following: 
auth_param basic program /usr/local/squid/libexec/pam_auth
auth_param basic children 5
auth_param basic realm Squid proxy-caching web server
auth_param basic credentialsttl 2 hours

acl password proxy_auth REQUIRED

http_access allow password

(and below it NOT above it in the config file)

http_access deny all
  1. That’s all the configuration required for squid. Now you will need to set proper permissions of the directories used by squid. 
chown -R nobody /usr/local/squid/var
  1. Create the swap directories 
/usr/local/etc/sbin/squid -z
  1. Now restart the squid service SystemStarter restart squid and point your browser to it and test..
  2. If you have problems, start squid in verbose mode /usr/local/squid/sbin/squid -D -d 3 and check the output for errors.

Installing Dansguardian on OS X server.

Download the Dansguardian OS X package.

Extract the tar file and install the dansguardian package.

All Dansguardian files are installed into the /opt/dansguardian directory.

Since I am running OS X.3.5 Server, it was neccessary to modify the startup/shutdown and restart script for dansguardian. Edit the /System/Library/StartupItems/dansguardian/dansguardian file so that it will use the dansguardian-10.3 binary instead of the link to the dansgaurdian-10.3 binary file. Before I changed this, I could not get the startup script to work..

Configure (you can download a great console from here http://www.lopata.net/filemgmt/) and start dansguardian as required.

fherbert

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