I would like tu use squid as a transparent proxy.

I change squid conf as:


httpd_accel_host virtual
httpd_accel_port 80
httpd_accel_with_proxy on
httpd_accel_uses_host_header on

Then I would like request an authentication from user (if they was
already authenticated for domain I don't want authentication)

auth_param ntlm program /usr/lib/squid/ntlm_auth
auth_param ntlm children 5
auth_param ntlm max_challenge_reuses 0
auth_param ntlm max_challenge_lifetime 15 minutes
auth_param ntlm use_ntlm_negotiate on
auth_param basic program /usr/lib/squid/ntlm_auth
auth_param basic children 5
auth_param basic realm Squid proxy-caching web server
auth_param basic credentialsttl 2 hours

#ACL per auth
acl squid_access proxy_auth REQUIRED
http_access allow squid_access

Then I configure iptables as:

$IPTABLES -A INPUT -p tcp --dport 3128 -j ACCEPT
$IPTABLES -t nat -A PREROUTING -i eth2 -p tcp --dport 80 -j REDIRECT
--to-port 3128 #eth2 --> didattica

when I try to start squid I obtain an error:

]# squid -N -d1
2006/11/21 15:59:36| Starting Squid Cache version 2.5.STABLE14 for
2006/11/21 15:59:36| Process ID 5631
2006/11/21 15:59:36| With 1024 file descriptors available
2006/11/21 15:59:36| Performing DNS Tests...
2006/11/21 15:59:36| Successful DNS name lookup tests...
2006/11/21 15:59:36| DNS Socket created at, port 32945, FD 4
2006/11/21 15:59:36| Adding nameserver from /etc/resolv.conf
2006/11/21 15:59:36| Adding nameserver from
2006/11/21 15:59:36| helperStatefulOpenServers: Starting 5 'ntlm_auth'
2006/11/21 15:59:36| WARNING: Cannot run '/usr/lib/squid/ntlm_auth'

I don't know any solution.