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Re: Re: Squid Url Filtering

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On 24/07/2013 12:35 a.m., kannan rbk wrote:
Hi ,

Thank you for your precious time.

We are using squid version 3.1.10 version. Our requirement is
https://xyz.abc.com/gadgets should allow but same "abc.com" domain
other then any request should block. This setup testing via ssl_bump,
but it doesn't work for me. Please help me on this.

Configuration file is below.


acl manager proto cache_object
acl localhost src 127.0.0.1/32 ::1
acl to_localhost dst 127.0.0.0/8 0.0.0.0/32 ::1
acl allowurls url_regex  [-i] \.gadgets$

Problem #1: When testing the URL-path it is better to use urlpath_regex which prevents any problems matching in the domain and username portions of the URL. And also gives Squid a chance to detect and warn about incorrect usage of the ACL.

The problem with urlpath_regex on HTTPS traffic is that the path _does not exist_ in CONNECT requests. Using url_regex instead of urlpath_regex to test the path portion will have no better luck finding it.


Problem #2: you are using "[-i]" in the ACL definition. That exists in the documentation to signify that the "-i" is an optional flag. If you want the regex to be case insensitive, add the -i (without brackets). Otherwise for case sensitive regex omit it entirely.

The result of your leaving the [] brackets in is that the ACL matches any URL containing a "-" OR an "i" *anywhere* in the URL. This has some important side effects later...


Problem #3: your pattern begins \. which means you are searching for the text ".gadgets" at the end of the URL, which can never match "/gadgets" at the start of the URL path segment.

Fix: I think you need to use this instead:
 acl allowurls urlpath_regex -i /gadgets$

acl blkdomain dstdomain .abc.com

# Example rule allowing access from your local networks.
# Adapt to list your (internal) IP networks from where browsing
# should be allowed
acl localnet src 10.0.0.0/8    # RFC1918 possible internal network
acl localnet src 172.16.0.0/12    # RFC1918 possible internal network
acl localnet src 192.168.0.0/16    # RFC1918 possible internal network
acl localnet src fc00::/7       # RFC 4193 local private network range
acl localnet src fe80::/10      # RFC 4291 link-local (directly
plugged) machines

acl SSL_ports port 443
acl Safe_ports port 80        # http
acl Safe_ports port 21        # ftp
acl Safe_ports port 443        # https
acl Safe_ports port 70        # gopher
acl Safe_ports port 210        # wais
acl Safe_ports port 1025-65535    # unregistered ports
acl Safe_ports port 280        # http-mgmt
acl Safe_ports port 488        # gss-http
acl Safe_ports port 591        # filemaker
acl Safe_ports port 777        # multiling http
acl CONNECT method CONNECT

#
# Recommended minimum Access Permission configuration:
http_port 3129  ssl-bump cert=/etc/squid/test.crt key=/etc/squid/test.key
ssl_bump deny blkdomain
ssl_bump allow allowurls

Problem #4: ssl_bump ACLs are run on the CONNECT request details before bumping to determine whether bumping can take place. The allowurls at that point never has access to the URL-path details, so only the [-i] regex pattern error will ever match anything.

Fix: it looks like you can remove this line form your config file entirely. The next ssl_bump line to match anything is an "ssl_bump allow all".

http_access allow allowurls

Problem #5, (side effect of #2). Since any URL with "-" or "i" in it anywhere will match this ACL, this rule being here above the default security protections will allow *anyone* completely free open access to send requests through your proxy. That includes arbitrary CONNECT requests to any domain with a hypen (ie spammers domain "open-proxy.example.com:25").

Fix: This will not be so bad once you fix problem #2, but please consider moving this line down below the default security settings anyway. They are there to protect you from this type of ACL mistake amongst other things.

# Only allow cachemgr access from localhost
http_access allow manager localhost
http_access deny manager
#http_access allow allowurls
# Deny requests to certain unsafe ports
http_access deny !Safe_ports

# Deny CONNECT to other than secure SSL ports
http_access deny CONNECT !SSL_ports

# We strongly recommend the following be uncommented to protect innocent
# web applications running on the proxy server who think the only
# one who can access services on "localhost" is a local user
#http_access deny to_localhost

#
# INSERT YOUR OWN RULE(S) HERE TO ALLOW ACCESS FROM YOUR CLIENTS
#

# Example rule allowing access from your local networks.
# Adapt localnet in the ACL section to list your (internal) IP networks
# from where browsing should be allowed

http_access allow accounts
http_access allow localnet
http_access allow CONNECT

Problem #6: Anyone on your network can send *anything* through your Squid. Even if they are not matching the accounts or localnet ACLs.

Fix: Remove this line. The default security rule we ship with Squid about CONNECT does permit traffic through port-443 or other ports at your discretion.

#http_access allow localhost


http_port 3129  ssl-bump cert=/etc/squid/test.crt key=/etc/squid/test.key
ssl_bump allow allowurls
# Squid normally listens to port 3128
#ssl_bump allow all
#ssl_bump deny allowurls
#ssl_bump deny localhost
ssl_bump deny blkdomain

Problem #7: you already had all the above rules up higher in your config file. You can expect a WARNING or ERROR from Squid about the dulicate port 3129 entry. The access controls will be ignored or never match anything if they ever get tested.

Fix: Please remove the duplicate access lines. You will want to consider removing the many commented-out lines as well. It will all make your config a lot clearer to read and understand.

#ssl_bump deny all
ssl_bump allow all
http_access deny all

always_direct allow all


# And finally deny all other access to this proxy

sslproxy_cert_error allow all
#We recommend you to use at least the following line.
hierarchy_stoplist cgi-bin ?

NOTE: that recommmendation was an oversight. You should remove that hierarchy_stoplist line to make always_direct work a little better.

Amos

# Uncomment and adjust the following to add a disk cache directory.
#cache_dir ufs /var/spool/squid 100 16 256

# Leave coredumps in the first cache dir
coredump_dir /var/spool/squid

# Add any of your own refresh_pattern entries above these.
refresh_pattern ^ftp:        1440    20%    10080
refresh_pattern ^gopher:    1440    0%    1440
refresh_pattern -i (/cgi-bin/|\?) 0    0%    0
refresh_pattern .        0    20%    4320


logformat squid  %ts.%03tu %6tr %>a %>A %Ss/%03>Hs %<st %rm %ru %un %Sh/%<A %mt
cache_log /var/log/squid/cache.log
access_log /var/log/squid/access.log

Regards ,
Bharathikannan R

On Sun, Jul 7, 2013 at 12:20 PM, kannan rbk <kannanrbk.r@xxxxxxxxx> wrote:
Dear Team,

I am using squid proxy(3.1).  Read some articles and blogs , they said
squid cannot support "urlpath_regex , url_regex" because of https
connections are encrypted. Is there any alternative for this?

  How can I block https request based on urls from our network?

I want to allow "zmedia.com/shop" through SSL.

--
Regards,

Bharathikannan R







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