Cryptography Pitfalls at LASCON 2016

Cryptography Pitfalls at LASCON 2016

58376779023f009fc13d160bb3e82515?s=128

John Downey

November 03, 2016
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  1. Cryptography Pitfalls John Downey | @jtdowney @jtdowney 1

  2. Chicago @jtdowney 2

  3. @jtdowney 3

  4. @jtdowney 4

  5. @jtdowney 5

  6. @jtdowney 6

  7. The views expressed in this presentation are my own, and

    not those of PayPal or any of its affiliates. @jtdowney 7
  8. @jtdowney 8

  9. Confidentiality @jtdowney 9

  10. Authentication @jtdowney 10

  11. Identification @jtdowney 11

  12. Rigorous Science @jtdowney 12

  13. Peer Review @jtdowney 13

  14. @jtdowney 14

  15. You have probably seen the door to a bank vault,

    at least in the movies. You know, 10-inch-thick, hardened steel, with huge bolts to lock it in place. It certainly looks impressive. We often find the digital equivalent of such a vault door installed in a tent. The people standing around it are arguing over how thick the door should be, rather than spending their time looking at the tent. — Cryptography Engineering by Niels Ferguson, Bruce Schneier, and Tadayoshi Kohno @jtdowney 15
  16. • For data in transit • Use TLS (née SSL),

    SSH, or VPN/IPsec • For data at rest • Use GnuPG • Data to be signed • Use GnuPG @jtdowney 16
  17. • Avoid low level libraries • OpenSSL • PyCrypto •

    Bouncy Castle • Use a high level library • NaCL/libsodium (C, Ruby, etc) • Keyczar (Python and Java) @jtdowney 17
  18. @jtdowney 18

  19. Random Number Generation @jtdowney 19

  20. Pitfalls 1. Not using a cryptographically strong random number generator

    2. Broken random number generators 3. Not using random data when it is required @jtdowney 20
  21. @jtdowney 21

  22. @jtdowney 22

  23. Pitfalls 1. Not using a cryptographically strong random number generator

    2. Broken random number generators 3. Not using random data when it is required @jtdowney 23
  24. @jtdowney 24

  25. @jtdowney 25

  26. MD_Update(&m,buf,j); @jtdowney 26

  27. Don't add uninitialised data to the random number generator. This

    stop valgrind from giving error messages in unrelated code. (Closes: #363516) @jtdowney 27
  28. /* DO NOT REMOVE THE FOLLOWING CALL TO MD_Update()! */

    MD_Update(&m,buf,j); /* We know that line may cause programs such as purify and valgrind to complain about use of uninitialized data. The problem is not, it's with the caller. Removing that line will make sure you get really bad randomness and thereby other problems such as very insecure keys. */ @jtdowney 28
  29. @jtdowney 29

  30. @jtdowney 30

  31. @jtdowney 31

  32. @jtdowney 32

  33. Pitfalls 1. Not using a cryptographically strong random number generator

    2. Broken random number generators 3. Not using random data when it is required @jtdowney 33
  34. @jtdowney 34

  35. Recommendations • Use a cryptographically strong random number generator •

    Unix-like • Read from /dev/urandom • Windows • RandomNumberGenerator in System.Security.Cryptography (.NET) • CryptGenRandom (Windows) @jtdowney 35
  36. Hash Functions @jtdowney 36

  37. Pitfalls 1. Using weak/old algorithms 2. Misunderstanding checksums 3. Length

    extension attacks @jtdowney 37
  38. @jtdowney 38

  39. @jtdowney 39

  40. @jtdowney 40

  41. @jtdowney 41

  42. 9EC4C12949A4F31474F299058CE2B22A @jtdowney 42

  43. mission = """ USCYBERCOM plans, coordinates, integrates, synchronizes and conducts

    activities to: direct the operations and defense of specified Department of Defense information networks and; prepare to, and when directed, conduct full spectrum military cyberspace operations in order to enable actions in all domains, ensure US/Allied freedom of action in cyberspace and deny the same to our adversaries. """ md5(mission) # => 9EC4C12949A4F31474F299058CE2B22A @jtdowney 43
  44. Pitfalls 1. Using weak/old algorithms 2. Misunderstanding checksums 3. Length

    extension attacks @jtdowney 44
  45. @jtdowney 45

  46. Pitfalls 1. Using weak/old algorithms 2. Misunderstanding checksums 3. Length

    extension attacks @jtdowney 46
  47. Message Authentication Code (MAC) tag = MAC(key, value) • Takes:

    • key - shared secret • value - value to protected integrity of • Returns: • tag - value that represents the integrity @jtdowney 47
  48. Naive approach tag = sha256(key || value) @jtdowney 48

  49. Length Extension Attacks secret = "my-secret-key" value = "buy 10

    units at $1" signature = sha256(secret + value) @jtdowney 49
  50. Length Extension Attacks secret = "my-secret-key" value = "buy 10

    units at $1<garbage>actually make that at $0" signature = sha256(secret + value) @jtdowney 50
  51. Length Extension Attacks secret = "my-secret-key" value = "buy 10

    units at $1" signature = hmac_sha256(secret, value) @jtdowney 51
  52. @jtdowney 52

  53. @jtdowney 53

  54. Recommendations • Use SHA-256 (SHA-2 family) • Choose HMAC-SHA-256 if

    you want a signature • Stop using MD5 • Don't use SHA-1 in new projects • Phase it out for uses that require collision resistance @jtdowney 54
  55. Ciphers @jtdowney 55

  56. Pitfalls 1. Using old/weak algorithms 2. Using ECB mode for

    block ciphers 3. Not using authenticated encryption @jtdowney 56
  57. @jtdowney 57

  58. @jtdowney 58

  59. @jtdowney 59

  60. Pitfalls 1. Using old/weak algorithms 2. Using ECB mode for

    block ciphers 3. Not using authenticated encryption @jtdowney 60
  61. AES - primitive ciphertext = AES_Encrypt(key, plaintext) plaintext = AES_Decrypt(key,

    ciphertext) • Function over: • key - 128, 192, or 256 bit value • plaintext - 128 bit value • ciphertext - 128 bit value @jtdowney 61
  62. ECB Encrypt while (remaining blocks) { block = ... #

    next 16 byte (128 bit chunk) ouput.append(AES_Encrypt(key, block)) } @jtdowney 62
  63. @jtdowney 63

  64. @jtdowney 64

  65. Pitfalls 1. Using old/weak algorithms 2. Using ECB mode for

    block ciphers 3. Not using authenticated encryption @jtdowney 65
  66. @jtdowney 66

  67. @jtdowney 67

  68. @jtdowney 68

  69. @jtdowney 69

  70. World of hurt @jtdowney 70

  71. Recommendations • Prefer to use box/secret box from NaCL/libsodium •

    Stop using DES • Stop building your own on top of AES • Stop encrypting without protecting integrity @jtdowney 71
  72. What if you have to use AES • Do not

    use ECB mode • Be sure to use authenticated encryption • GCM mode would be a good first choice • Verify the tag/MAC first • Still easy to mess up in a critical way @jtdowney 72
  73. TLS/SSL @jtdowney 73

  74. Pitfalls 1. Not verifying the certificate chain or hostname 2.

    Misconfigured server settings 3. Using a broken library @jtdowney 74
  75. @jtdowney 75

  76. @jtdowney 76

  77. @jtdowney 77

  78. Hostname verification @jtdowney 78

  79. Hostname verification • Check that you got the certificate for

    who you intended to connect to • Hostname verification is protocol dependent • OpenSSL doesn't have it built in @jtdowney 79
  80. Pitfalls 1. Not verifying the certificate chain or hostname 2.

    Misconfigured server settings 3. Using a broken library @jtdowney 80
  81. @jtdowney 81

  82. SSL Labs https://www.ssllabs.com @jtdowney 82

  83. testssl.sh @jtdowney 83

  84. TLS Server Settings https://mozilla.github.io/server-side-tls/ssl-config-generator/ @jtdowney 84

  85. Pitfalls 1. Not verifying the certificate chain or hostname 2.

    Misconfigured server settings 3. Using a broken library @jtdowney 85
  86. @jtdowney 86

  87. @jtdowney 87

  88. Recommendations • Do ensure you're validating connections • Lean on

    a framework/library if possible • But check that it also does the right thing • Setup and automated test to validate this setting (badssl.com) @jtdowney 88
  89. Trust @jtdowney 89

  90. The authenticity of host 'apollo.local (10.0.2.56)' can't be established. RSA

    key fingerprint is 04:63:c1:ba:c7:31:04:12:14:ff:b6:c4:32:cf:44:ec. Are you sure you want to continue connecting (yes/no)? @jtdowney 90
  91. @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

    IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY! Someone could be eavesdropping on you right now (man-in-the-middle attack)! It is also possible that the RSA host key has just been changed. The fingerprint for the RSA key sent by the remote host is 04:63:c1:ba:c7:31:04:12:14:ff:b6:c4:32:cf:44:ec. Please contact your system administrator. @jtdowney 91
  92. @jtdowney 92

  93. Certificate Pinning @jtdowney 93

  94. @jtdowney 94

  95. Recommendations • Think about what organizations you really trust •

    Investigate certificate pinning for your apps @jtdowney 95
  96. Quantum Computers @jtdowney 96

  97. Pitfalls 1. Assuming current crypto will last forever @jtdowney 97

  98. @jtdowney 98

  99. @jtdowney 99

  100. Recommendations • Follow the PQCrypto discussion • Stay away from

    PQCrypto until the industry starts to standardize • Hope that researchers are moving fast enough @jtdowney 100
  101. @jtdowney 101

  102. Stanford Crypto Class http://crypto-class.com @jtdowney 102

  103. Matasano Crypto Challenges http://cryptopals.com @jtdowney 103

  104. Questions John Downey | @jtdowney @jtdowney 104

  105. Images • https://flic.kr/p/6eagaw • https://flic.kr/p/4KWhKn • https://flic.kr/p/9F2BCv • https://flic.kr/p/486xYS •

    https://flic.kr/p/7Ffppm • https://flic.kr/p/8TuJD9 • https://flic.kr/p/4iLJZt • https://flic.kr/p/4pGZuz • https://flic.kr/p/48w7wP • https://flic.kr/p/8aZWNE • https://flic.kr/p/5NRHp • https://flic.kr/p/7p7raq • https://flic.kr/p/aZEE1Z • https://flic.kr/p/7WtwAz • https://flic.kr/p/6AN9mM • https://flic.kr/p/6dt62u • https://flic.kr/p/4ZqwyB • https://flic.kr/p/Bqewr • https://flic.kr/p/ecdhVE • https://flic.kr/p/AV1Nd @jtdowney 105