In Apigee deployments we may need to use a forward proxy server for routing southbound traffic from Apigee runtime to target servers via a forward proxy server. In such a requirement we could squid proxy for that purpose. In this article I will outline how to install and configure squid proxy with TLS enabled.
1. Create a CentOS virtual machine either on GCP or on any other cloud platform.
2. Generate a TLS certificate using Let’s Encrypt or use a TLS certificate generated using a different certificate authority.
If you prefer to use Let's Encrypt, you could use Let’s Encrypt bot (certbot) and generate a valid TLS certificate to be installed on Squid. You will need to have access to a real domain name for this purpose.
# Install snapd
sudo dnf install epel-release
sudo dnf upgrade
sudo yum install snapd
sudo systemctl enable --now snapd.socket
sudo ln -s /var/lib/snapd/snap /snap
Reference: https://snapcraft.io/docs/installing-snap-on-centos
# Install Let’s Encrypt certbot
sudo snap install --classic certbot
sudo ln -s /snap/bin/certbot /usr/bin/certbot
# Generate a TLS certificate with manual DNS verification option
sudo certbot --manual --preferred-challenges dns certonly
References:
3. SSH into the CentOS virtual machine and install Squid
yum -y install epel-release
sudo yum update -y
sudo yum install squid -y
Reference: https://wiki.squid-cache.org/KnowledgeBase/CentOS
4. Create a directory for storing the TLS certificates and grant the ownership of that directory to squid user:
sudo mkdir /etc/squid/certs
sudo mv squid-ca-cert-key.pem /etc/squid/certs/.
sudo chown squid:squid -R /etc/squid/certs
5. Combine the certificate chain and private key to a single file:
cat squid-ca-cert.pem squid-ca-key.pem >> squid-ca-cert-key.pem
6. Create a squid SSL database and make sure the squid user can access it:
sudo mkdir /var/lib/squid
sudo /usr/lib64/squid/security_file_certgen -c -s /var/lib/squid/ssl_db -M 20MB
sudo chown squid:squid -R /var/lib/squid/ssl_db
7. Add the following http_port and https_port configurations to /etc/squid/squid.conf:
http_port 3128 ssl-bump \
cert=/etc/squid/certs/squid-ca-cert-key.pem \
generate-host-certificates=off dynamic_cert_mem_cache_size=16MB
https_port 3129 \
cert=/etc/squid/certs/squid-ca-cert-key.pem \
generate-host-certificates=off dynamic_cert_mem_cache_size=16MB
sslcrtd_program /usr/lib64/squid/security_file_certgen -s /var/lib/squid/ssl_db -M 20MB
acl step1 at_step SslBump1
ssl_bump peek step1
ssl_bump bump all
ssl_bump splice all
The complete /etc/squid/squid.conf file will look as follows:
#
# Recommended minimum configuration:
#
# Example rule allowing access from your local networks.
# Adapt to list your (internal) IP networks from where browsing
# should be allowed
acl localnet src 0.0.0.1-0.255.255.255 # RFC 1122 "this" network (LAN)
#acl localnet src 10.0.0.0/8 # RFC 1918 local private network (LAN)
acl localnet src 100.64.0.0/10 # RFC 6598 shared address space (CGN)
acl localnet src 169.254.0.0/16 # RFC 3927 link-local (directly plugged) machines
acl localnet src 172.16.0.0/12 # RFC 1918 local private network (LAN)
acl localnet src 192.168.0.0/16 # RFC 1918 local private network (LAN)
acl localnet src fc00::/7 # RFC 4193 local private network range
acl localnet src fe80::/10 # RFC 4291 link-local (directly plugged) machines
acl localnet src 10.112.0.0/14
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:
#
# 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
# Only allow cachemgr access from localhost
http_access allow localhost manager
http_access deny manager
# 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
http_access allow all
# Squid normally listens to port 3128
http_port 3128 ssl-bump \
cert=/etc/squid/certs/squid-ca-cert-key.pem \
generate-host-certificates=off dynamic_cert_mem_cache_size=16MB
https_port 3129 \
cert=/etc/squid/certs/squid-ca-cert-key.pem \
generate-host-certificates=off dynamic_cert_mem_cache_size=16MB
sslcrtd_program /usr/lib64/squid/security_file_certgen -s /var/lib/squid/ssl_db -M 20MB
acl step1 at_step SslBump1
ssl_bump peek step1
ssl_bump bump all
ssl_bump splice all
# 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
8. Start Squid proxy server in foreground and verify:
sudo squid --foreground -d 2 -f /etc/squid/squid.conf
9. Tail squid access log on a new terminal:
sudo tail -f /var/log/squid/access.log
10. Now, enable the squid service, start it, and confirm it’s running:
sudo systemctl enable squid
sudo systemctl start squid
sudo systemctl status squid.service
Reference: https://elatov.github.io/2019/01/using-squid-to-proxy-ssl-sites/
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