Cryptography Pitfalls at BsidesMSP 2017

Cryptography Pitfalls at BsidesMSP 2017

58376779023f009fc13d160bb3e82515?s=128

John Downey

June 25, 2017
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  1. Cryptography Pitfalls John Downey | @jtdowney @jtdowney 1

  2. @jtdowney 2

  3. @jtdowney 3

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

    not those of PayPal or any of its affiliates. @jtdowney 4
  5. @jtdowney 5

  6. Confidentiality @jtdowney 6

  7. Authentication @jtdowney 7

  8. Identification @jtdowney 8

  9. Rigorous Science @jtdowney 9

  10. Peer Review @jtdowney 10

  11. @jtdowney 11

  12. 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 12
  13. • For data in transit • Use TLS, SSH, or

    VPN/IPsec • For data at rest • Use GnuPG • Data to be signed • Use GnuPG @jtdowney 13
  14. • Avoid low level libraries • OpenSSL • PyCrypto •

    Bouncy Castle • Use a high level library • NaCL/libsodium (C, Ruby, PHP, etc) • Keyczar (C++, Python, and Java) @jtdowney 14
  15. @jtdowney 15

  16. Random Number Generation @jtdowney 16

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

    2. Not using random data when it is required 3. Broken random number generators @jtdowney 17
  18. @jtdowney 18

  19. @jtdowney 19

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

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

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

    2. Not using random data when it is required 3. Broken random number generators @jtdowney 22
  23. @jtdowney 23

  24. @jtdowney 24

  25. @jtdowney 25

  26. @jtdowney 26

  27. MD_Update(&m,buf,j); @jtdowney 27

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

    stop valgrind from giving error messages in unrelated code. (Closes: #363516) @jtdowney 28
  29. /* 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 29
  30. Recommendations • Use a cryptographically strong random number generator •

    Unix-like • Read from /dev/urandom • Windows • RandomNumberGenerator in System.Security.Cryptography (.NET) • CryptGenRandom • Java use java.security.SecureRandom @jtdowney 30
  31. Hash Functions @jtdowney 31

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

    extension attacks @jtdowney 32
  33. @jtdowney 33

  34. @jtdowney 34

  35. @jtdowney 35

  36. @jtdowney 36

  37. 9EC4C12949A4F31474F299058CE2B22A @jtdowney 37

  38. 9EC4C12949A4F31474F299058CE2B22A 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. @jtdowney 38
  39. Pitfalls 1. Using weak/old algorithms 2. Misunderstanding checksums 3. Length

    extension attacks @jtdowney 39
  40. @jtdowney 40

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

    extension attacks @jtdowney 41
  42. 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 42
  43. Naive approach tag = sha256(key + value) @jtdowney 43

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

    units at $1" signature = sha256(secret + value) @jtdowney 44
  45. Length Extension Attacks secret = "my-secret-key" value = "buy 10

    units at $1" + " or $0" signature = sha256(secret + value) @jtdowney 45
  46. Fixed secret = "my-secret-key" value = "buy 10 units at

    $1" signature = hmac_sha256(secret, value) @jtdowney 46
  47. @jtdowney 47

  48. @jtdowney 48

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

    you want a signature • Use BLAKE2b if you need speed • Stop using MD5 • Stop using SHA1 @jtdowney 49
  50. Ciphers @jtdowney 50

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

    block ciphers 3. Not using authenticated encryption @jtdowney 51
  52. @jtdowney 52

  53. @jtdowney 53

  54. @jtdowney 54

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

    block ciphers 3. Not using authenticated encryption @jtdowney 55
  56. 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 56
  57. ECB Encrypt while (remaining blocks) { block = ... #

    next 16 byte (128 bit chunk) ouput.append(AES_Encrypt(key, block)) } @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. @jtdowney 61

  62. @jtdowney 62

  63. @jtdowney 63

  64. @jtdowney 64

  65. World of hurt @jtdowney 65

  66. 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 66
  67. 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 67
  68. TLS/SSL @jtdowney 68

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

    Misconfigured server settings 3. Using a broken library @jtdowney 69
  70. @jtdowney 70

  71. @jtdowney 71

  72. @jtdowney 72

  73. @jtdowney 73

  74. Hostname verification @jtdowney 74

  75. 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 75
  76. Pitfalls 1. Not verifying the certificate chain or hostname 2.

    Misconfigured server settings 3. Using a broken library @jtdowney 76
  77. @jtdowney 77

  78. SSL Labs https://www.ssllabs.com @jtdowney 78

  79. testssl.sh https://testssl.sh @jtdowney 79

  80. TLS Server Settings https://mozilla.github.io/server-side-tls/ssl-config-generator/ @jtdowney 80

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

    Misconfigured server settings 3. Using a broken library @jtdowney 81
  82. @jtdowney 82

  83. @jtdowney 83

  84. 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 84
  85. Trust @jtdowney 85

  86. 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 86
  87. @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ 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 87
  88. @jtdowney 88

  89. Certificate Pinning @jtdowney 89

  90. @jtdowney 90

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

    Investigate certificate pinning for your apps @jtdowney 91
  92. @jtdowney 92

  93. Stanford Crypto Class http://crypto-class.com @jtdowney 93

  94. Matasano Crypto Challenges http://cryptopals.com @jtdowney 94

  95. Questions John Downey | @jtdowney @jtdowney 95

  96. Bonus Round @jtdowney 96

  97. Quantum Computers @jtdowney 97

  98. Pitfalls 1. Assuming current crypto will last forever @jtdowney 98

  99. @jtdowney 99

  100. @jtdowney 100

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

    PQCrypto until the industry starts to standardize • Hope that researchers are moving fast enough @jtdowney 101
  102. 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 • https://flic.kr/p/5tWgh4 @jtdowney 102