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NGINX + HTTPS 101The Basics & Getting Started Sept 23, 2015 Nick Sullivan (@grittygrease)
#nginx #nginxconf
NGINX + HTTPS 101
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What is HTTPS?
Protocol Versions
Cipher Suites
Configuring nginx
Bonus: Configuring HSTS
Backend HTTPS
Double Bonus: OCSP Stapling
Checking your configuration
What is HTTPS?
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HTTPS = HTTP + Security• Security: SSL or TLS
• Provides data encryption and server authentication
• Negotiation of keys happens in the “handshake”
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Why set up HTTPS?• User privacy
• SEO bump
• Put in front of HTTPS-incapable services
• General good practice
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😀
😯
What are the downsides?• Operational complexity
• Extra latency (two round-trips for first connection)
• CPU cost
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What you need to set up HTTPS• A set of protocols you support
• A set of ciphers you support in order of preference
• A certificate and a private key signed by a trusted Certificate Authority
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Protocol Versions
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A bit of history• SSL v2.0 released in 1995 by Netscape
• SSL v3.0 released in 1996 fixes major issues with v2
• TLS v1.0 released in 1999 by IETF: minor tweaks to SSLv3
• TLS v1.1 released in 2006 with minor tweaks
• TLS v1.2 released in 2008 with improved hashes and AEAD mode
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A bit of history• SSL v2.0 released in 1995 - Broken by design
• SSL v3.0 released in 1996 - Broken by POODLE (Nov 2014)
• TLS v1.0 released in 1999 - Weakened by BEAST (2011) and Lucky 13 (2013)
• TLS v1.1 released in 2006 - Weakened by Lucky 13 (2013) and RC4 (2013, 2015)
• TLS v1.2 released in 2008 - Only safe with AEAD mode ciphers
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Client Compatibility for TLS 1.2• Chrome >= 30
• Android >= 5.0
• Firefox >= 27
• Internet Explorer/Edge >= 11
• Safari Mac >= 7
• iOS >= 5
• Note: iOS 9 applications require TLS 1.2 support
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~75%
Client Compatibility for TLS 1.0• Basically everything except Windows XP SP2 and earlier
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Configuration options• High security, low compatibility
ssl_protocols TLSv1.2;
• Medium security, high compatibility
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
• Low security, maximum compatibility
ssl_protocols SSLv3 TLSv1 TLSv1.1 TLSv1.2;
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Top Grade
SSL Labs
Cipher Suites
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Cipher Suites• Complicated string describing the type of crypto used
• Defined by openssl (check your ciphers with $ openssl ciphers)
Example:
ECDHE-RSA-AES128-GCM-SHA256: ECDHE-ECDSA-AES128-GCM-SHA256: ECDHE-RSA-AES256-GCM-SHA384: ECDHE-ECDSA-AES256-GCM-SHA384: DHE-RSA-AES128-GCM-SHA256:
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Cipher Suites
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ECDHE-RSA-AES256-GCM-SHA384
Key Exchange - Certificate Key - Transport Cipher - Integrity
Server Cipher Suites• Client lists supported cipher suites in order of preference
• Server takes intersection of client list and server supported cipher list
• Server selects preferred cipher of remaining
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Cipher Suite NegotiationAES256-GCM-SHA384: ECDHE-RSA-AES128-GCM-SHA256: ECDHE-RSA-AES256-GCM-SHA384:
ECDHE-RSA-AES256-GCM-SHA384: ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES128-SHA256: AES256-GCM-SHA384:
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ECDHE-RSA-AES256-GCM-SHA384 AES256-GCM-SHA384
ECDHE-RSA-AES256-GCM-SHA384
Recommended Cipher SuitesCloudFlare’s suggestions:
github.com/cloudflare/sslconfig
EECDH+CHACHA20:EECDH+AES128:RSA+AES128:EECDH+AES256:RSA+AES256:EECDH+3DES:RSA+3DES:!MD5
• Mozilla has their own suggestions:
https://mozilla.github.io/server-side-tls/ssl-config-generator/
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Certificates
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What is a certificate?• Organization name
• Public key
• Issuer name
• Rights
• Validity period
• Hostnames
• Digital signature by issuer
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What is a trusted certificate?• When certificate is issued by a Certificate Authority (CA) that browsers trust
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How do I get a certificate?• Create a key pair
• A private key
• A certificate signing request (contains your public key)
• Get a CA to create a certificate from the CSR
• Usually costs $$$
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How do create a CSR and private key?• Using CFSSL
$ cfssl print-defaults csr > csr.json
$ cfssl genkey csr.json | cfssljson -bare
• Using OpenSSL
$ openssl genrsa -out key.pem 2048
$ openssl req -new -sha256 -key key.pem -out key.csr
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How to get a free certificate• StartSSL.com: follow the instructions, get a headache
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Certificate chain• Need to include all certificates in trust
chain up to the root
• If CA did not provide, try `cfssl bundle`
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Configuring nginx
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NGINX configurations parameters• Basic features
• ssl_certificate, ssl_certificate_key
• ssl_protocols
• ssl_ciphers
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NGINX configurations parameters• Before you start: Find out the version of OpenSSL you are using
• Recommend at least 1.0.1p
$ openssl version
OpenSSL 0.9.8zd 8 Jan 2015
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server {
listen 443 ssl;
ssl_certificate /path/to/signed_cert_plus_intermediates;
ssl_certificate_key /path/to/private_key;
ssl_session_timeout 1d;
ssl_session_cache shared:SSL:50m;
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_ciphers EECDH+CHACHA20:EECDH+AES128:RSA+AES128:EECDH+AES256:RSA+AES256:EECDH+3DES:RSA+3DES:!MD5;
ssl_prefer_server_ciphers on;
}
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Certificate Chain
Private key
• Session caching — faster connections from existing clients
• ssl_session_timeout 1d;
• ssl_session_cache shared:SSL:50m;
• Session tickets — advanced version
• Works with Chrome and Firefox
Extra options
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server {
listen 443 ssl;
ssl_certificate /path/to/signed_cert_plus_intermediates;
ssl_certificate_key /path/to/private_key;
ssl_session_timeout 1d;
ssl_session_cache shared:SSL:50m;
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_ciphers EECDH+CHACHA20:EECDH+AES128:RSA+AES128:EECDH+AES256:RSA+AES256:EECDH+3DES:RSA+3DES:!MD5;
ssl_prefer_server_ciphers on;
}
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Protocols
Ciphers
• Prefer server cipher preference
• ssl_prefer_server_ciphers on;
Additional fields
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Multiple domains, same certificatessl_certificate multiSAN.crt;
ssl_certificate_key multiSAN.key;
server {
listen 443 ssl;
server_name www.example.com;
...
}
server {
listen 443 ssl;
server_name www.example.org;
...
}
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Backend HTTPS
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• Encrypt to the server behind nginx
• Need a list of trusted CAs
Encryption on the backend
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http {
server {
proxy_ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
proxy_ssl_ciphers EECDH+CHACHA20:EECDH+AES128:RSA+AES128:EECDH+AES256:RSA+AES256:EECDH+3DES:RSA+3DES:!MD5;
proxy_ssl_trusted_certificate /etc/ssl/certs/trusted_ca_cert.crt;
proxy_ssl_verify on;
proxy_ssl_verify_depth 2;
proxy_ssl_session_reuse on;
}
}
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Protocols
CiphersTrusted CAs
• Internal CA
• You can create your own certificates for the services behind nginx
• Requires managing your own public key infrastructure
• Public CA
• Need certificate from publicly trusted CA
• Root store already present on machine (e.g. Ubuntu: /etc/ssl/certs/ca-certificates.crt)
Options for trusted CAs
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Checking your configuration
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Bonus: Configuring HSTS
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• HTTP header cached by browser
• Browser always attempts HTTPS
• Maximum age defined in seconds
• Preload list for Chrome and Firefox
• Requires 6 month HSTS
• Requires includeSubdomains
What is HSTS?
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• Prevent hijacking of HTTP
Why?
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• Prevents people from visiting HTTP version of site
• If HTTPS config is broken (expired certificate), site is broken
Risks
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server {
listen 443 ssl;
ssl_certificate /path/to/signed_cert_plus_intermediates;
ssl_certificate_key /path/to/private_key;
ssl_session_timeout 1d;
ssl_session_cache shared:SSL:50m;
# intermediate configuration. tweak to your needs.
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_ciphers EECDH+CHACHA20:EECDH+AES128:RSA+AES128:EECDH+AES256:RSA+AES256:EECDH+3DES:RSA+3DES:!MD5;
ssl_prefer_server_ciphers on;
# HSTS (ngx_http_headers_module is required) (15768000 seconds = 6 months)
add_header Strict-Transport-Security max-age=15768000;
# OCSP Stapling ---
# fetch OCSP records from URL in ssl_certificate and cache them
ssl_stapling on;
ssl_stapling_verify on;
ssl_trusted_certificate /path/to/root_CA_cert_plus_intermediates;
}
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Max-age: 6 months
Double Bonus: Configuring OCSP Stapling
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• Certificates can not only expire, they can be revoked
• OCSP (Online Certificate Status Protocol) can be queried to check status
• Can slow down requests since it requires another connection
• OCSP Stapling: server pre-fetches OSCP response
• Saves a round-trip by the client
What is OCSP Stapling?
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How much faster?DNS (1334ms)
TCP handshake (240ms)
SSL handshake (376ms)
Follow certificate chain (1011ms)
DNS to CA (300ms)
TCP to CA (407ms)
OCSP to CA #1 (598ms)
TCP to CA #2 (317ms)
OCSP to CA #2 (444ms)
Finish SSL handshake (1270ms)
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~30%
server {
listen 443 ssl;
ssl_certificate /path/to/signed_cert_plus_intermediates;
ssl_certificate_key /path/to/private_key;
ssl_session_timeout 1d;
ssl_session_cache shared:SSL:50m;
# intermediate configuration. tweak to your needs.
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_ciphers EECDH+CHACHA20:EECDH+AES128:RSA+AES128:EECDH+AES256:RSA+AES256:EECDH+3DES:RSA+3DES:!MD5;
ssl_prefer_server_ciphers on;
# HSTS (ngx_http_headers_module is required) (15768000 seconds = 6 months)
add_header Strict-Transport-Security max-age=15768000;
# OCSP Stapling ---
# fetch OCSP records from URL in ssl_certificate and cache them
ssl_stapling on;
ssl_stapling_verify on;
ssl_trusted_certificate /path/to/root_CA_cert_plus_intermediates;
}
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Get this file from your CA
Questions?
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NGINX + HTTPS 101The Basics & Getting Started
Nick Sullivan @grittygrease
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