Hansel & Gretel do TLS - PHPBenelux 2020

Effective encryption is a vital component of a safe and secure internet, especially since the arrival of HTTP/2. Many sites and mobile apps still don't use TLS to encrypt their traffic, often citing some kind of fear over the complexity of it all, or if they do, they make a mess of it, resulting in a literal false sense of security. The basics of TLS encryption are straightforward, but the practical realities run into a bewildering forest of acronyms. This talk gives you a breadcrumb trail through the backwoods of TLS, OCSP, ECDHE, ALPN, HTTP/2, HSTS, CT, and more, including the latest changes in TLS 1.3.

You'll get an overview of what problems TLS solves, how it works, its component pieces, how they fit together, where vulnerabilities and mitigations apply, and what tools and resources can help you get up to speed, and keep the wicked witch away!

This presentation was given at PHPBenelux 2020 in Antwerp, Belgium.

Transcript

1. by
   Marcus Bointon
   Synchromedia Limited,
   Smartmessages.net,
   Radically Open Security
   

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2. Marcus Bointon - TLS
   PHPBenelux 2020
   What is TLS?
   Transport Layer Security protocol
   The new(ish) name for SSL - Since 1999
   Versions: SSLv2, SSLv3, TLSv1.0, TLSv1.1, TLSv1.2, TLSv1.3
   A set of standards for security & encryption
   Can wrap around any higher-level protocol
   HTTP, SMTP, FTP, IMAP, DNS, etc
   Popular implementations: OpenSSL, LibreSSL, BoringSSL
   

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3. Marcus Bointon - TLS
   PHPBenelux 2020
   Why use TLS?
   Provides confidentiality, authenticity & integrity
   Better performance with HTTP/2
   Google will rank you higher
   Required for iOS apps
   Chrome 50 disabled HTTP GeoLocation
   Keeps the wicked witch out
   

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4. Marcus Bointon - TLS
   PHPBenelux 2020
   Toolkit: Hashes, MACs, Ciphers & KX
   Hashes produce a fixed-length digest from data; integrity
   MD5, SHA1, SHA2 (SHA256, SHA384, SHA512)
   Message Authentication Code (MAC): data + a key; authenticity
   HMAC-MD5, HMAC-SHA256, Poly1305
   Ciphers; encryption algorithms; confidentiality
   Integer factoring, elliptic curve ("EC"), symmetric, asymmetric
   RC4, AES, 3DES, RSA, ChaCha20
   Key Exchange
   RSA, Diffie-Hellman ("DH"), x25519, x448, EC, "Ephemeral", ECDHE
   

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5. Marcus Bointon - TLS
   PHPBenelux 2020
   New in TLS 1.3
   Removal of all weak and legacy algorithms & extensions
   Moar encryption
   Lower handshake overhead
   PFS-only
   Elliptic curve ciphers as standard
   Downgrade protection
   

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6. PHPBenelux 2020 Marcus Bointon - TLS
   TLS 1.3 Handshake
   ClientHello
   Cipher Suite List
   Key Share
   ServerHello
   Cipher Suite
   Key Share
   Certificate & Signature
   Server Finished
   Client Finished
   HTTP Request
   HTTP Response
   200ms
   

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7. PHPBenelux 2020 Marcus Bointon - TLS
   TLS 1.3 Resumption
   ClientHello
   Session ticket
   Key Share
   HTTP GET
   ServerHello
   Key Share
   Server Finished
   HTTP Response
   0-RTT!
   

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8. PHPBenelux 2020 Marcus Bointon - TLS
   Diffie-Hellman Key Exchange
   Alice
   Bob
   Random
   colour
   Secret
   colour
   +
   +
   +
   +
   =
   =
   =
   =
   Secret
   colour
   Common
   secret
   Exchange
   intermediate colours
   

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9. Marcus Bointon - TLS
   PHPBenelux 2020
   Creating certificates
   Create a public/private key pair
   At least 2048 bits for RSA
   Create a certificate signing request (CSR)
   Use SHA-2 signature
   Sign the CSR to create a public certificate
   Yourself…
   By a Certificate Authority (CA)
   

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10. Marcus Bointon - TLS
    PHPBenelux 2020
    Intermediate
    CA certificate
    Certificate chains
    Browser & OS
    certificate store
    Root CA
    certificate
    Site certificate
    Server
    certificate store
    Root CA
    certificate
    

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11. Marcus Bointon - TLS
    PHPBenelux 2020
    CRLs, OCSP & Stapling
    How to find out if a cert has been revoked?
    Browser asks the CA — OCSP
    Our site becomes dependent on CA's site
    CA's site becomes a privacy leak risk
    Get the server to ask the CA in advance
    Staple the proof of validity to the certificate
    Can't fake it because it's signed by the CA
    Browser Server
    CA
    Browser Server
    CA
    

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12. Marcus Bointon - TLS
    PHPBenelux 2020
    Use TLS by default, keeps things simple
    Don’t use protocol-relative URLs (//…)
    Avoid mixed mode: https + http
    HSTS & CSP can auto-upgrade
    Create proxies if HTTPS not available
    Cookies: set httponly, secure, samesite flags
    Deploying TLS - App concerns
    

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13. Marcus Bointon - TLS
    PHPBenelux 2020
    https://mozilla.github.io/server-side-tls/ssl-config-generator/
    Redirect to secure site
    Use SNI + SAN to host multiple domains on one IP
    Create DH params for forward secrecy
    At least TLSv1.2 - disable old & weak ciphers
    Enable TLS session caching
    Staple CA certs for OCSP
    Deploying TLS - Server config
    

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14. Marcus Bointon - TLS
    PHPBenelux 2020
    Deploying TLS - Improving security
    HTTP Strict Transport Security (HSTS) header
    “We always encrypt”
    Certificate Authority Authorisation in DNS
    “Permit only these CAs to issue certs”
    Content Security Policy (CSP) header
    “Permit only these sources”
    Expect-CT header
    Check that the cert was issued correctly
    

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15. Marcus Bointon - TLS
    PHPBenelux 2020
    Testing TLS
    Click the padlock!
    openssl s_client
    Qualys SSL Labs: https://www.ssllabs.com/ssltest/
    https://hstspreload.appspot.com/
    observatory.mozilla.org, testssl.sh, crt.sh, report-uri.com,
    securityheaders.com, webbkoll.dataskydd.net
    

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16. PHPBenelux 2020 Marcus Bointon - TLS
    TLS overhead - old way
    

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17. PHPBenelux 2020 Marcus Bointon - TLS
    TLS overhead - new way
    

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18. Marcus Bointon - TLS
    PHPBenelux 2020
    TLS Summary
    It can be free
    It’s fast(er) - use HTTP/2
    Use TLS everywhere by default
    Simple measures maximise security
    Help Hansel & Gretel make it to your site safely
    

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19. Marcus Bointon - TLS
    PHPBenelux 2020
    ...and they all lived happily ever after
    

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20. PHPBenelux 2020 Marcus Bointon - TLS
    Thank you
    Feedback: https://joind.in/talk/b7924
    Marcus Bointon
    marcus@synchromedia.co.uk
    @SynchroM & @PrivacySpider
    Synchro on GitHub & Stack Exchange
    

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