Good morning, I use successfully squid to authenticate AD users in a domain .dom3.dom2.dom1.com and it works fine. The server is debian etch with squid 2.7.STABLE6 and the clients are Windows (ntlm) and Linux (squid_kerb_auth). On Linux client pc I installed samba+winbind. The users accounts and computers accounts are on a domain .dom3.dom2.dom1.com. Now things have changed, the users accounts are on parent domain (.domain.com) and the computers accounts are in child domain (.child.domain.com). The .domain.com is a root domain of forest. The forest is in a mixed mode (windows 2008 and windows 2003). I have installed a server with debian lenny with squid 2.7.STABLE9. The configure options are: --prefix=/usr/local/squid --enable-auth=negotiate ntlm --enable-ntlm-auth-helpers=SMB --enable-negotiate-auth-helpers=squid_kerb_auth --enable-default-err-language=Italian --enable-err-languages=Italian English --enable-async-io --with-pthreads --enable-storeio=ufs aufs diskd null --with-large-files This is my squid.conf auth_param negotiate program /usr/local/squid/libexec/squid_kerb_auth -d -s HTTP/squid.domain.com@.domain.com auth_param negotiate children 10 auth_param negotiate keep_alive on auth_param ntlm program /usr/local/squid/libexec/ntlm_auth domain/server1 child/server2 auth_param ntlm children 30 auth_param ntlm keep_alive off acl out proxy_auth REQUIRED acl autkrb src 192.168.47.36 http_access allow out autkrb This is my krb5.conf [libdefaults] default_realm = DOMAIN.COM # The following krb5.conf variables are only for MIT Kerberos. krb4_config = /etc/krb.conf krb4_realms = /etc/krb.realms kdc_timesync = 1 ccache_type = 4 forwardable = true proxiable = true dns_lookup_realm = false dns_lookup_kdc = false ticket_lifetime = 24h clockskew = 600 [realms] DOMAIN.COM = { kdc = srv1.domain.com admin_server = srv1.domain.com default_domain = domain.com } CHILD.DOMAIN.COM = { kdc = serv1.child.domain.com admin_server = serv1.child.domain.com } [domain_realm] .domain.com = DOMAIN.COM domain.com = DOMAIN.COM .child.domain.com = CHILD.DOMAIN.COM child.domain.com = CHILD.DOMAIN.COM I also added the following lines to squid start script. KRB5_KTNAME=/usr/local/squid/etc/squid20100714.keytab export KRB5_KTNAME The dns are configured as parent windows domain doami.com. On client each time I try to use firefox, the server squid gives me the following error: squid_kerb_auth: gss_accept_sec_context() failed: Unspecified GSS failure. Minor code may provide more information. No error in the browser I see the pop-up for username and password. What does means this error? Have any ideas? Thanks for your help Nikkognt