TLSSSL How and Why

1
TLS/SSL - How and Why

• PCI Flags it but why do we care?
• By MadHat Unspecific

2
SSL How and Why

• What is TLS/SSL?
• How does TLS/SSL work?
• What is the difference between TLS and SSL?
• What is it used for?
• Weak Ciphers
• How this relates to PCI
• Exploitable
• SSL-Cipher-Check (tool from Unspecific.com)

3
What is TLS/SSL?

• Transport Layer Security
• Secure Socket Layers
• Application Layer Protocols
• Public/Asymmetric Key Cryptography
• OSI Layer 6

4
How does TLS/SSL work?

• Encryption Protocol, Key Length, Hashing
  Algorithm
• Authentication
• Handshake
• Request
• Protocols Supported
• Digital Certificate
• Session Keys

5
What is it used for?

• Security Data Integrity
• Prevents Eavesdropping, tampering message
  forgery
• HTTP is most famous as HTTPS
• Any layer 7 protocol, POP3, IMAP, SMTP, FTP
• OpenVPN
• Stunnel
• Ncat (included with Nmap)

6
Weak Ciphers

• Old Protocols
• SSLv2
• Key Strength
• 40bit 56bit ciphers
• RC2, RC4, NULL
• Weak Hash Algorithms
• DES
• ADH - anonymous DH cipher

7
How this relates to PCI Other Standards

• PCI 4.1 - Use strong cryptography and security
  protocols such as SSL/TLS or IPSEC to safeguard
  sensitive cardholder data during transmission
  over open, public networks.

8
Exploitable

• Man in the Middle
• Decryption of Communications

9
SSL-Cipher-Check

• OpenSSL binary
• Checks ALL supported Ciphers
• openssl ciphers
• openssl s_client -protocol -cipher cipher
  -connect hostport
• ssl_dump.logRaw openssl output

10
SSL-Cipher-Check

• ./ssl-cipher-check.pl SSL Cipher Check 1.1
  written by Lee 'MadHat' Heath (at)
  Unspecific.comUsage ./ssl-cipher-check.pl
  -dvwas lthostgt ltportgtdefault port is 443-d
  Add debug info (show it all, lots of stuff)-v
  Verbose. Show more info about what is found-w
  Show only weak ciphers enabled.-a Show all
  ciphers, enabled or not-s Show only the STRONG
  ciphers enabled.

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References

• http//en.wikipedia.org/wiki/Public-key_cryptograp
  hy
• http//en.wikipedia.org/wiki/Transport_Layer_Secur
  ity
• http//www.openssl.org/
• http//www.verisign.com/ssl/ssl-information-center
  /ssl-basics/index.html
• http//en.wikipedia.org/wiki/OSI_model
• http//www.gnu.org/software/gnutls/
• http//openvpn.net/
• http//www.stunnel.org/
• http//lasecwww.epfl.ch/memo/memo_ssl.shtml
• http//www.owasp.org/index.php/Testing_for_SSL-TLS
  
• http//www.unspecific.com/2009/02/16/ssl-cipher-ch
  eck
• http//www.schneier.com/paper-ssl.pdf
• https//www.pcisecuritystandards.org/security_stan
  dards/download.html?idpci_dss_v1-2.pdf

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• Future Meetings/Talks
• T-Shirt
• DefCon