SSL Labs Assessment Policy v2017

Part 1: New Grading Approach

• Use the entire A-F range, and A+ for exceptional configuration
• Reasonably well-configured servers get A+, A, and B.
• Servers with problems get grades C to F.
• Severity of a problem strongly influences the grade.
• Meanings of different grades:
  • A+ - exceptional configuration, security leader
  • A - good configuration
  • B - server supports obsolete crypto, but doesn't use it with modern clients
  • C - server relies on obsolete cryptography
  • D - low-severity problem
  • E - medium-severity problem
  • F - high-severity problem
• Additional grades:
  • T - for a server that doesn't have a publicly trusted certificate
  • M - for a server that doesn't have a valid certificate

Part 2: Baseline Configuration

Key and certificate:

• Strong private key (min. 2048-bit RSA or 256-bit ECDSA)
• Strong signature (SHA2)
• Valid publicly-trusted certificate
• Complete certificate chain
• Revocation information (except for short-lived certificates)

Protocol and configuration:

• TLS v1.2
• 128-bit cipher suites
• AEAD cipher suites
• Cipher suite preference (best possible suite is negotiated)
• Forward secrecy
• Strong key exchange
• Secure renegotiation
• Session/ticket longevity

For HTTP:

• HTTP Strict Transport Security
• No mixed content
• Secure session cookies

Part 3: Exceptional Configuration

• HSTS with long duration (6+ months), included subdomains and preloaded
• Third-party mixed content is expressly forbidden via CSP
• Protection against CRIME in place

Candidates:

• Must-staple
• HPKP
• TLS 1.3

Part 4: Problems

• SSL v2
• SSL v3 (POODLE)
• TLS v1.0
• Insecure renegotiation
• BEAST
• CRIME, TIME, BREACH
• Lucky 13
• RC4
• POODLE TLS
• FREAK
• Logjam
• SLOTH
• DROWN
• Heartbleed

Appendix: Implementation rules

Component classification:

• delight:
• expected: absence of feature makes the configuration obsolete
• obsolete: should not be used when better options are available
• weak: stronger should not be used
• insecure: must not be used

Classification

• TLS 1.2: expected

• SSLv3: obsolete

• SSLv2: insecure

• RSA key exchange (no forward secrecy): weak

• KX strength < 2048 bits: obsolete

• KX strength < 1024 bits: weak

• KX strength <= 768 bits: insecure

• Known DH parameters 10248 bits: weak

• Auth strength < 2048 bits: weak

• Auth strength < 1024 bits: insecure

• Cert signature SHA1: weak

• Cert signature MD5, MD2: insecure

• Ciphers below 128 bits (excluding 3DES): insecure

• Ciphers that use 64-bit blocks (e.g., 3DES): weak

• RC4: insecure

• Anonymous suites: insecure

• CBC suites: obsolete

• Secure renegotiation not supported: obsolete