Você está negando o acesso a portas não SSL diretamente no seu arquivo de configuração.
# Deny CONNECT to other than secure SSL ports
http_access deny CONNECT !SSL_ports
Espero que isso ajude.
Eu tenho um problema aqui,
Eu instalei o squid3, mas ele não pode acessar o site http como link , mas ele pode acessar https como link
aqui é meu squid.conf
#acl localnet src 192.168.0.0-192.168.255.0
#
# Recommended minimum configuration:
#
#acl manager proto cache_object
acl localnet src 192.168.0.0-192.168.255.0/24
#acl localhost src 127.0.0.1/32 ::1
#acl to_localhost dst 127.0.0.0/8 0.0.0.0/32 ::1
# 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 allow_domain dstdomain lastpass.com
acl SSL_ports port 443
acl SSL_ports port 832
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 280 # http-mgmt
acl Safe_ports port 488 # gss-http
acl Safe_ports port 591 # filemaker
acl Safe_ports port 777 # multiling http
acl Safe_ports port 593
acl Safe_ports port 8008
acl Safe_ports port 8080
acl Safe_ports port 1025-65535 # unregistered ports
acl winupdate dstdomain .microsoft.com .windowsupdate.com # # windows update
acl CONNECT method CONNECT
#
# Recommended minimum Access Permission configuration:
#
# Only allow cachemgr access from localhost
#http_access allow manager localhost
#http_access deny manager
# 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 localnet
#http_access allow localhost
# And finally deny all other access to this proxy
#http_access deny all
# Squid normally listens to port 3128
#httpd_port 3128
http_port 3128
# We recommend you to use at least the following line.
#hierarchy_stoplist cgi-bin ?
# Uncomment and adjust the following to add a disk cache directory.
cache_dir ufs /var/cache/squid_cache 50000 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
# not include client info in HTTP requests(e.g ipaddress)
#forwarded_for off
## not include information specific to proxy in HTTP requests
#request_header_access Referer deny all
#request_header_access X-Forwarded-For deny all
#request_header_access Via deny all
#request_header_access Cache-Control deny all
# use to apache log format
access_log /var/log/squid/access.log
# memory to use cache
#cache_mem 128 MB
# maximum size of one of cache item.
#maximum_object_size 128 MB
# for Google's too long request or reply.
#reply_header_max_size 50 KB
cache_effective_user squid
cache_effective_group root
obrigado antes