Squid 3.3.4 package for pfsense with ssl filtering

Pistolero

Hello!

Anyone know how to make the built-in antivirus work? c-icap keeps crashing with error signal 11 whenever I enable the AV functions. Or, is there any way to make squid not use c-icap and just use clamav, just like Dansguardian?

Thanks!

marcelloc

@Pistolero:

Hello!

Anyone know how to make the built-in antivirus work? c-icap keeps crashing with error signal 11 whenever I enable the AV functions. Or, is there any way to make squid not use c-icap and just use clamav, just like Dansguardian?

Thanks!

You can try old havp or test your squid in i386 pfsense version.

cheonne

i tried installing squid 3.3.10 dev in 2.1.3v i386
no issues found yet
squid starts after configuration.
looks like the missing lib before where now incorporated in the new version

asterix

Anyone has issues while using transparent mode in squid3-dev on amd64? I keep getting Access Denied.

If I configure proxy settings in the browser then it works fine. Just can't use transparent mode. Switching back to squid 3.1.20 works fine.

dig1234

I think there is a mistake in the reverse proxy config, I was having trouble so I read the squid.conf in pbi/…/etc and I found the directive
round-robin
even though I don't want that since my servers are independent of each other. I suggest either add a checkbox for that or remove that directive. Thanks!

smar

@periko:

The 2nd issue I found was with ebay, went I wanted to pay I receive this error:

The following error was encountered while trying to retrieve the URL: ://checkout.payments.ebay.com:443

Failed to establish a secure connection to site-ip

The system returned:

(92) Protocol error (TLS code: X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY)
SSL Certficate error: certificate issuer (CA) not known: /C=US/O=VeriSign, Inc./OU=VeriSign Trust Network/OU=Terms of use at https://www.verisign.com/rpa 10/CN=VeriSign Class 3 Secure Server CA - G3

This proxy and the remote host failed to negotiate a mutually acceptable security settings for handling your request. It is possible that the remote host does not support secure connections, or the proxy is not satisfied with the host security credentials.

What I did was to clear certs folders, empty index.txt, size folder value to 0, latter remove my ca from the browsers, create a new one and start over.

I could pay on ebay, the only issue I have is with my bank now, I will try to add the option that skip some sites from ssl-bump.

I still nervous if I can send this to production.

Can you give me a bit more details on how you resolved this. My SSL intercept seems to be working for most sites, but a few such as the ebay payments, or even the moto360 site (https://moto360.motorola.com/) fail with the same error about not recognising the CA.

Many thanks.

dig1234

For what it's worth, I'm using latest Squid3-dev (3.3.10 pkg 2.2.2) with ssl intercept and am able to browse to that moto360 site with no error.

Can you give me a bit more details on how you resolved this. My SSL intercept seems to be working for most sites, but a few such as the ebay payments, or even the moto360 site (https://moto360.motorola.com/) fail with the same error about not recognising the CA.

Many thanks.

smar

@dig1234:

For what it's worth, I'm using latest Squid3-dev (3.3.10 pkg 2.2.2) with ssl intercept and am able to browse to that moto360 site with no error.

Can you give me a bit more details on how you resolved this. My SSL intercept seems to be working for most sites, but a few such as the ebay payments, or even the moto360 site (https://moto360.motorola.com/) fail with the same error about not recognising the CA.

Many thanks.

That's very odd, as I'm on exactly the same build, and using ssl intercept/transparent. Is there any specific configuration parameters you've changed/added in your squid setup?

Also do you have any problems in posting messages to https sites (e.g. this forum) when going through the proxy? I keep getting an error in posting, and thus have to use a machine that doesn't go through the proxy.

dig1234

Ah, I actually had "do not verify remote cert" set, I did not realize. When I set that I get the same error at moto360.
Perhaps that particular root is not in the store that the squid package is using, if that's the case this should not be difficult to correct..

@smar:

@dig1234:

For what it's worth, I'm using latest Squid3-dev (3.3.10 pkg 2.2.2) with ssl intercept and am able to browse to that moto360 site with no error.

Can you give me a bit more details on how you resolved this. My SSL intercept seems to be working for most sites, but a few such as the ebay payments, or even the moto360 site (https://moto360.motorola.com/) fail with the same error about not recognising the CA.

Many thanks.

That's very odd, as I'm on exactly the same build, and using ssl intercept/transparent. Is there any specific configuration parameters you've changed/added in your squid setup?

Also do you have any problems in posting messages to https sites (e.g. this forum) when going through the proxy? I keep getting an error in posting, and thus have to use a machine that doesn't go through the proxy.

smar

@dig1234:

Ah, I actually had "do not verify remote cert" set, I did not realize. When I set that I get the same error at moto360.
Perhaps that particular root is not in the store that the squid package is using, if that's the case this should not be difficult to correct..

Thanks for spotting that and yes selecting that option allows me to visit such sites. With regards to the certificate squid is complaining about, it is from Thawte, and so one would have assumed it would be included. However, I did notice that the certificate's CN was "Thawte Inc", but non of the Thawte certificates in /usr/local/share/certs had exactly the same CN (the ones there are Thawte Premium Server, Thawte Primary Root etc).

Also are you able to post to https sites, such as this forum, when going through squid? I am still getting the following message unless I use a PC that bypasses the proxy:

Error 403

We're sorry, but we could not fulfill your request for /index.php?action=post2;start=270;board=15 on this server.

You do not have permission to access this server. Before trying again, close your browser, run anti-virus and anti- spyware software and remove any viruses and spyware from your computer.

Your technical support key is: 5688-9cbf-b40c-8ddc

You can use this key to fix this problem yourself.

If you are unable to fix the problem yourself, please contact the WEBMA5TER and be sure to provide the technical support key shown above.

UPDATE: Actually the above posting error seems to be an issue with my Chrome setup, as posting is working fine from IE.

dig1234

I do not have any issue posting from firefox.
Should be pretty simple to just drop that root CA cert in the folder /usr/pbi/squid-amd64/share/certs. I'm just not sure about the naming convention used, seems to be based on a hash. Likely squid uses the filename to locate the correct cert. Just guessing here.

@smar:

UPDATE: Actually the above posting error seems to be an issue with my Chrome setup, as posting is working fine from IE.

pubmsu

Anyone figured out how to do load-balancing of squid traffic for 2.1.x or 2.2 alpha?

eyditharen

I already running squid3 ver 3.3.4, working normal can cache http/https with 1 interface ( use as proxy box ), how to use squid3 working with mikrotik ..

gar2k

new rds protocol 8.0 not work more, any ideas?

xtrgeo

Hi,

can anyone help me on why do I get "proxy refuses connection"??

Squid3-dev package
Squidguard3
System Patch ->squidguard fix

Configs:

# This file is automatically generated by pfSense
# Do not edit manually !

http_port 10.66.106.65:8081
icp_port 7
dns_v4_first on
pid_filename /var/run/squid.pid
cache_effective_user proxy
cache_effective_group proxy
error_default_language el
icon_directory /usr/pbi/squid-amd64/etc/squid/icons
visible_hostname Proxy-
cache_mgr it@skata.gr
access_log /var/squid/logs/access.log
cache_log /var/squid/logs/cache.log
cache_store_log none
netdb_filename /var/squid/logs/netdb.state
pinger_enable on
pinger_program /usr/pbi/squid-amd64/libexec/squid/pinger

logfile_rotate 0
debug_options rotate=0
shutdown_lifetime 3 seconds
# Allow local network(s) on interface(s)
acl localnet src  10.66.106.64/26
uri_whitespace strip

acl dynamic urlpath_regex cgi-bin ?
cache deny dynamic

cache_mem 200 MB
maximum_object_size_in_memory 1024 KB
memory_replacement_policy heap GDSF
cache_replacement_policy heap LFUDA
cache_dir ufs /var/squid/cache 4096 16 256
minimum_object_size 10 KB
maximum_object_size 2048 KB
offline_mode off
cache_swap_low 85
cache_swap_high 95
cache allow all

# No redirector configured

#Remote proxies

# Setup some default acls
# From 3.2 further configuration cleanups have been done to make things easier and safer. The manager, localhost, and to_localhost ACL definitions are now built-in.
# acl localhost src 127.0.0.1/32
acl allsrc src all
acl safeports port 21 70 80 210 280 443 488 563 591 631 777 901  3128 3127 1025-65535 
acl sslports port 443 563  

# From 3.2 further configuration cleanups have been done to make things easier and safer. The manager, localhost, and to_localhost ACL definitions are now built-in.
#acl manager proto cache_object

acl purge method PURGE
acl connect method CONNECT

# Define protocols used for redirects
acl HTTP proto HTTP
acl HTTPS proto HTTPS
acl allowed_subnets src 10.66.106.64/26
http_access allow manager localhost

# Allow external cache managers
acl ext_manager src 10.66.106.65
http_access allow manager ext_manager

http_access deny manager
http_access allow purge localhost
http_access deny purge
http_access deny !safeports
http_access deny CONNECT !sslports

# Always allow localhost connections
# From 3.2 further configuration cleanups have been done to make things easier and safer. 
# The manager, localhost, and to_localhost ACL definitions are now built-in.
# http_access allow localhost

request_body_max_size 0 KB
delay_pools 1
delay_class 1 2
delay_parameters 1 -1/-1 -1/-1
delay_initial_bucket_level 100
delay_access 1 allow allsrc

# Reverse Proxy settings

# Package Integration
url_rewrite_program /usr/pbi/squidguard-squid3-amd64/bin/squidGuard -c /usr/pbi/squidguard-squid3-amd64/etc/squidGuard/squidGuard.conf
url_rewrite_bypass off
url_rewrite_children 16 startup=8 idle=4 concurrency=0

# Custom options before auth

acl sglog url_regex -i sgr=ACCESSDENIED
http_access deny sglog
# Setup allowed acls
# Allow local network(s) on interface(s)
http_access allow allowed_subnets
http_access allow localnet
# Default block all to be sure
http_access deny allsrc

icap_enable on
icap_send_client_ip on
icap_send_client_username on 
icap_client_username_encode off
icap_client_username_header X-Authenticated-User
icap_preview_enable on
icap_preview_size 1024

icap_service service_req reqmod_precache bypass=0 icap://127.0.0.1:1344/squidclamav
icap_service service_resp respmod_precache bypass=0 icap://127.0.0.1:1344/squidclamav

adaptation_access service_req allow all
adaptation_access service_resp allow all

# ============================================================
# SquidGuard configuration file
# This file generated automaticly with SquidGuard configurator
# (C)2006 Serg Dvoriancev
# email: dv_serg@mail.ru
# ============================================================

logdir /var/squidGuard/log
dbhome /var/db/squidGuard

# 
dest blk_BL_adv {
	domainlist blk_BL_adv/domains
	urllist blk_BL_adv/urls
	log block.log
}

# 
dest blk_BL_aggressive {
	domainlist blk_BL_aggressive/domains
	urllist blk_BL_aggressive/urls
	log block.log
}

# 
dest blk_BL_alcohol {
	domainlist blk_BL_alcohol/domains
	urllist blk_BL_alcohol/urls
	log block.log
}

# 
dest blk_BL_anonvpn {
	domainlist blk_BL_anonvpn/domains
	urllist blk_BL_anonvpn/urls
	log block.log
}

# 
dest blk_BL_automobile_bikes {
	domainlist blk_BL_automobile_bikes/domains
	urllist blk_BL_automobile_bikes/urls
	log block.log
}

# 
dest blk_BL_automobile_boats {
	domainlist blk_BL_automobile_boats/domains
	urllist blk_BL_automobile_boats/urls
	log block.log
}

# 
dest blk_BL_automobile_cars {
	domainlist blk_BL_automobile_cars/domains
	urllist blk_BL_automobile_cars/urls
	log block.log
}

# 
dest blk_BL_automobile_planes {
	domainlist blk_BL_automobile_planes/domains
	urllist blk_BL_automobile_planes/urls
	log block.log
}

# 
dest blk_BL_chat {
	domainlist blk_BL_chat/domains
	urllist blk_BL_chat/urls
	log block.log
}

# 
dest blk_BL_costtraps {
	domainlist blk_BL_costtraps/domains
	urllist blk_BL_costtraps/urls
	log block.log
}

# 
dest blk_BL_dating {
	domainlist blk_BL_dating/domains
	urllist blk_BL_dating/urls
	log block.log
}

# 
dest blk_BL_downloads {
	domainlist blk_BL_downloads/domains
	urllist blk_BL_downloads/urls
	log block.log
}

# 
dest blk_BL_drugs {
	domainlist blk_BL_drugs/domains
	urllist blk_BL_drugs/urls
	log block.log
}

# 
dest blk_BL_dynamic {
	domainlist blk_BL_dynamic/domains
	urllist blk_BL_dynamic/urls
	log block.log
}

# 
dest blk_BL_education_schools {
	domainlist blk_BL_education_schools/domains
	urllist blk_BL_education_schools/urls
	log block.log
}

# 
dest blk_BL_finance_banking {
	domainlist blk_BL_finance_banking/domains
	urllist blk_BL_finance_banking/urls
	log block.log
}

# 
dest blk_BL_finance_insurance {
	domainlist blk_BL_finance_insurance/domains
	urllist blk_BL_finance_insurance/urls
	log block.log
}

# 
dest blk_BL_finance_moneylending {
	domainlist blk_BL_finance_moneylending/domains
	urllist blk_BL_finance_moneylending/urls
	log block.log
}

# 
dest blk_BL_finance_other {
	domainlist blk_BL_finance_other/domains
	urllist blk_BL_finance_other/urls
	log block.log
}

# 
dest blk_BL_finance_realestate {
	domainlist blk_BL_finance_realestate/domains
	urllist blk_BL_finance_realestate/urls
	log block.log
}

# 
dest blk_BL_finance_trading {
	domainlist blk_BL_finance_trading/domains
	urllist blk_BL_finance_trading/urls
	log block.log
}

# 
dest blk_BL_fortunetelling {
	domainlist blk_BL_fortunetelling/domains
	urllist blk_BL_fortunetelling/urls
	log block.log
}

# 
dest blk_BL_forum {
	domainlist blk_BL_forum/domains
	urllist blk_BL_forum/urls
	log block.log
}

# 
dest blk_BL_gamble {
	domainlist blk_BL_gamble/domains
	urllist blk_BL_gamble/urls
	log block.log
}

# 
dest blk_BL_government {
	domainlist blk_BL_government/domains
	urllist blk_BL_government/urls
	log block.log
}

# 
dest blk_BL_hacking {
	domainlist blk_BL_hacking/domains
	urllist blk_BL_hacking/urls
	log block.log
}

# 
dest blk_BL_hobby_cooking {
	domainlist blk_BL_hobby_cooking/domains
	urllist blk_BL_hobby_cooking/urls
	log block.log
}

# 
dest blk_BL_hobby_games-misc {
	domainlist blk_BL_hobby_games-misc/domains
	urllist blk_BL_hobby_games-misc/urls
	log block.log
}

# 
dest blk_BL_hobby_games-online {
	domainlist blk_BL_hobby_games-online/domains
	urllist blk_BL_hobby_games-online/urls
	log block.log
}

# 
dest blk_BL_hobby_gardening {
	domainlist blk_BL_hobby_gardening/domains
	urllist blk_BL_hobby_gardening/urls
	log block.log
}

# 
dest blk_BL_hobby_pets {
	domainlist blk_BL_hobby_pets/domains
	urllist blk_BL_hobby_pets/urls
	log block.log
}

# 
dest blk_BL_homestyle {
	domainlist blk_BL_homestyle/domains
	urllist blk_BL_homestyle/urls
	log block.log
}

# 
dest blk_BL_hospitals {
	domainlist blk_BL_hospitals/domains
	urllist blk_BL_hospitals/urls
	log block.log
}

# 
dest blk_BL_imagehosting {
	domainlist blk_BL_imagehosting/domains
	urllist blk_BL_imagehosting/urls
	log block.log
}

# 
dest blk_BL_isp {
	domainlist blk_BL_isp/domains
	urllist blk_BL_isp/urls
	log block.log
}

# 
dest blk_BL_jobsearch {
	domainlist blk_BL_jobsearch/domains
	urllist blk_BL_jobsearch/urls
	log block.log
}

# 
dest blk_BL_library {
	domainlist blk_BL_library/domains
	urllist blk_BL_library/urls
	log block.log
}

# 
dest blk_BL_military {
	domainlist blk_BL_military/domains
	urllist blk_BL_military/urls
	log block.log
}

# 
dest blk_BL_models {
	domainlist blk_BL_models/domains
	urllist blk_BL_models/urls
	log block.log
}

# 
dest blk_BL_movies {
	domainlist blk_BL_movies/domains
	urllist blk_BL_movies/urls
	log block.log
}

# 
dest blk_BL_music {
	domainlist blk_BL_music/domains
	urllist blk_BL_music/urls
	log block.log
}

# 
dest blk_BL_news {
	domainlist blk_BL_news/domains
	urllist blk_BL_news/urls
	log block.log
}

# 
dest blk_BL_podcasts {
	domainlist blk_BL_podcasts/domains
	urllist blk_BL_podcasts/urls
	log block.log
}

# 
dest blk_BL_politics {
	domainlist blk_BL_politics/domains
	urllist blk_BL_politics/urls
	log block.log
}

# 
dest blk_BL_porn {
	domainlist blk_BL_porn/domains
	urllist blk_BL_porn/urls
	log block.log
}

# 
dest blk_BL_radiotv {
	domainlist blk_BL_radiotv/domains
	urllist blk_BL_radiotv/urls
	log block.log
}

# 
dest blk_BL_recreation_humor {
	domainlist blk_BL_recreation_humor/domains
	urllist blk_BL_recreation_humor/urls
	log block.log
}

# 
dest blk_BL_recreation_martialarts {
	domainlist blk_BL_recreation_martialarts/domains
	urllist blk_BL_recreation_martialarts/urls
	log block.log
}

# 
dest blk_BL_recreation_restaurants {
	domainlist blk_BL_recreation_restaurants/domains
	urllist blk_BL_recreation_restaurants/urls
	log block.log
}

# 
dest blk_BL_recreation_sports {
	domainlist blk_BL_recreation_sports/domains
	urllist blk_BL_recreation_sports/urls
	log block.log
}

# 
dest blk_BL_recreation_travel {
	domainlist blk_BL_recreation_travel/domains
	urllist blk_BL_recreation_travel/urls
	log block.log
}

# 
dest blk_BL_recreation_wellness {
	domainlist blk_BL_recreation_wellness/domains
	urllist blk_BL_recreation_wellness/urls
	log block.log
}

# 
dest blk_BL_redirector {
	domainlist blk_BL_redirector/domains
	urllist blk_BL_redirector/urls
	log block.log
}

# 
dest blk_BL_religion {
	domainlist blk_BL_religion/domains
	urllist blk_BL_religion/urls
	log block.log
}

# 
dest blk_BL_remotecontrol {
	domainlist blk_BL_remotecontrol/domains
	urllist blk_BL_remotecontrol/urls
	log block.log
}

# 
dest blk_BL_ringtones {
	domainlist blk_BL_ringtones/domains
	urllist blk_BL_ringtones/urls
	log block.log
}

# 
dest blk_BL_science_astronomy {
	domainlist blk_BL_science_astronomy/domains
	urllist blk_BL_science_astronomy/urls
	log block.log
}

# 
dest blk_BL_science_chemistry {
	domainlist blk_BL_science_chemistry/domains
	urllist blk_BL_science_chemistry/urls
	log block.log
}

# 
dest blk_BL_searchengines {
	domainlist blk_BL_searchengines/domains
	urllist blk_BL_searchengines/urls
	log block.log
}

# 
dest blk_BL_sex_education {
	domainlist blk_BL_sex_education/domains
	urllist blk_BL_sex_education/urls
	log block.log
}

# 
dest blk_BL_sex_lingerie {
	domainlist blk_BL_sex_lingerie/domains
	urllist blk_BL_sex_lingerie/urls
	log block.log
}

# 
dest blk_BL_shopping {
	domainlist blk_BL_shopping/domains
	urllist blk_BL_shopping/urls
	log block.log
}

# 
dest blk_BL_socialnet {
	domainlist blk_BL_socialnet/domains
	urllist blk_BL_socialnet/urls
	log block.log
}

# 
dest blk_BL_spyware {
	domainlist blk_BL_spyware/domains
	urllist blk_BL_spyware/urls
	log block.log
}

# 
dest blk_BL_tracker {
	domainlist blk_BL_tracker/domains
	urllist blk_BL_tracker/urls
	log block.log
}

# 
dest blk_BL_updatesites {
	domainlist blk_BL_updatesites/domains
	urllist blk_BL_updatesites/urls
	log block.log
}

# 
dest blk_BL_urlshortener {
	domainlist blk_BL_urlshortener/domains
	urllist blk_BL_urlshortener/urls
	log block.log
}

# 
dest blk_BL_violence {
	domainlist blk_BL_violence/domains
	urllist blk_BL_violence/urls
	log block.log
}

# 
dest blk_BL_warez {
	domainlist blk_BL_warez/domains
	urllist blk_BL_warez/urls
	log block.log
}

# 
dest blk_BL_weapons {
	domainlist blk_BL_weapons/domains
	urllist blk_BL_weapons/urls
	log block.log
}

# 
dest blk_BL_webmail {
	domainlist blk_BL_webmail/domains
	urllist blk_BL_webmail/urls
	log block.log
}

# 
dest blk_BL_webphone {
	domainlist blk_BL_webphone/domains
	urllist blk_BL_webphone/urls
	log block.log
}

# 
dest blk_BL_webradio {
	domainlist blk_BL_webradio/domains
	urllist blk_BL_webradio/urls
	log block.log
}

# 
dest blk_BL_webtv {
	domainlist blk_BL_webtv/domains
	urllist blk_BL_webtv/urls
	log block.log
}

# 
dest Cat-Custom {
	domainlist Cat-Custom/domains
	redirect http://10.64.132.104/error.php?a=%a&n=%n&i=%i&s=%s&t=%t&u=%u
	log block.log
}

# 
dest Cat-Facebook {
	domainlist Cat-Facebook/domains
	redirect http://10.64.132.104/error.php?a=%a&n=%n&i=%i&s=%s&t=%t&u=%u
	log block.log
}

# 
rew safesearch {
	s@(google..*/search?.*q=.*)@&safe=active@i
	s@(google..*/images.*q=.*)@&safe=active@i
	s@(google..*/groups.*q=.*)@&safe=active@i
	s@(google..*/news.*q=.*)@&safe=active@i
	s@(yandex..*/yandsearch?.*text=.*)@&fyandex=1@i
	s@(search.yahoo..*/search.*p=.*)@&vm=r&v=1@i
	s@(search.live..*/.*q=.*)@&adlt=strict@i
	s@(search.msn..*/.*q=.*)@&adlt=strict@i
	s@(.bing..*/.*q=.*)@&adlt=strict@i
	log block.log
}

# 
acl  {
	# 
	default  {
		pass !Cat-Custom !Cat-Facebook !blk_BL_drugs !blk_BL_gamble !blk_BL_hobby_games-misc !blk_BL_hobby_games-online !blk_BL_porn !blk_BL_sex_education !blk_BL_sex_lingerie !blk_BL_warez all
		redirect http://10.64.132.104/error.php?a=%a&n=%n&i=%i&s=%s&t=%t&u=%u
		log block.log
	}
}

aGeekhere

Hi all read through the whole post.

I have transparent ssl filtering working however I am having issues with update servers like windows update, adobe creative cloud, google update, and others
I tried to create an alias with some of the white listed links for windows updare however they are not working. Is there a better way to white list these update servers? because even if I get aliases working I have to manually find each server, find there link and add it to the aliases. Is there a better way for this? as there could be 100s of update servers in which would need to do this for.

Thanks

webstor

Hi xtrego,

set the icap_service service_req reqmod_precache bypass=0 icap://127.0.0.1:1344/squidclamav to
icap_service service_req reqmod_precache bypass=1 icap://127.0.0.1:1344/squidclamav

and do the same steps to the second row.

dig1234

Bumping this issue, perhaps it should be broken off to a new thread but I'm not sure how.
I just updated to the latest squid package 2.2.8 and the issue remains.
The word "round-robin" appears in the cache_peer lines inside squid.conf this creates a situation where requests are alternately sent to the wrong peer when multiple web servers are added that are not serving the same site… ie they are not load balancing.

I believe the word "round-robin" should either be removed or exposed as a checkbox in the gui under web servers tab.

@dig1234:

I think there is a mistake in the reverse proxy config, I was having trouble so I read the squid.conf in pbi/…/etc and I found the directive
round-robin
even though I don't want that since my servers are independent of each other. I suggest either add a checkbox for that or remove that directive. Thanks!

wcrowder

Squid is a 3.4.9, 3.5 is around the corner…

hyundrax

everything work fine.. but not good caching at all :(

squid3.jpg_thumb