Cryptography Pitfalls at BsidesMSP 2017

Transcript

1. Cryptography
   Pitfalls
   John Downey | @jtdowney
   @jtdowney 1
   

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2. @jtdowney 2
   

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3. @jtdowney 3
   

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4. The views expressed in
   this presentation are my
   own, and not those of
   PayPal or any of its
   affiliates.
   @jtdowney 4
   

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5. @jtdowney 5
   

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6. Confidentiality
   @jtdowney 6
   

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7. Authentication
   @jtdowney 7
   

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8. Identification
   @jtdowney 8
   

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9. Rigorous Science
   @jtdowney 9
   

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10. Peer Review
    @jtdowney 10
    

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11. @jtdowney 11
    

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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
    

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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
    

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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
    

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15. @jtdowney 15
    

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16. Random Number
    Generation
    @jtdowney 16
    

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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
    

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18. @jtdowney 18
    

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19. @jtdowney 19
    

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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
    

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21. @jtdowney 21
    

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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
    

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23. @jtdowney 23
    

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24. @jtdowney 24
    

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25. @jtdowney 25
    

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26. @jtdowney 26
    

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

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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
    

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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
    

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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
    

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31. Hash Functions
    @jtdowney 31
    

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32. Pitfalls
    1. Using weak/old algorithms
    2. Misunderstanding checksums
    3. Length extension attacks
    @jtdowney 32
    

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33. @jtdowney 33
    

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34. @jtdowney 34
    

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35. @jtdowney 35
    

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36. @jtdowney 36
    

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37. 9EC4C12949A4F31474F299058CE2B22A
    @jtdowney 37
    

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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
    

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39. Pitfalls
    1. Using weak/old algorithms
    2. Misunderstanding checksums
    3. Length extension attacks
    @jtdowney 39
    

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40. @jtdowney 40
    

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41. Pitfalls
    1. Using weak/old algorithms
    2. Misunderstanding checksums
    3. Length extension attacks
    @jtdowney 41
    

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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
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43. Naive approach
    tag = sha256(key + value)
    @jtdowney 43
    

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44. Length Extension Attacks
    secret = "my-secret-key"
    value = "buy 10 units at $1"
    signature = sha256(secret + value)
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45. Length Extension Attacks
    secret = "my-secret-key"
    value = "buy 10 units at $1" + " or $0"
    signature = sha256(secret + value)
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46. Fixed
    secret = "my-secret-key"
    value = "buy 10 units at $1"
    signature = hmac_sha256(secret, value)
    @jtdowney 46
    

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47. @jtdowney 47
    

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48. @jtdowney 48
    

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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
    

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50. Ciphers
    @jtdowney 50
    

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51. Pitfalls
    1. Using old/weak algorithms
    2. Using ECB mode for block ciphers
    3. Not using authenticated encryption
    @jtdowney 51
    

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52. @jtdowney 52
    

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53. @jtdowney 53
    

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54. @jtdowney 54
    

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55. Pitfalls
    1. Using old/weak algorithms
    2. Using ECB mode for block ciphers
    3. Not using authenticated encryption
    @jtdowney 55
    

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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
    

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57. ECB Encrypt
    while (remaining blocks) {
    block = ... # next 16 byte (128 bit chunk)
    ouput.append(AES_Encrypt(key, block))
    }
    @jtdowney 57
    

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58. @jtdowney 58
    

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59. @jtdowney 59
    

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60. Pitfalls
    1. Using old/weak algorithms
    2. Using ECB mode for block ciphers
    3. Not using authenticated encryption
    @jtdowney 60
    

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61. @jtdowney 61
    

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62. @jtdowney 62
    

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63. @jtdowney 63
    

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64. @jtdowney 64
    

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65. World of hurt
    @jtdowney 65
    

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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
    

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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
    

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68. TLS/SSL
    @jtdowney 68
    

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69. Pitfalls
    1. Not verifying the certificate chain or
    hostname
    2. Misconfigured server settings
    3. Using a broken library
    @jtdowney 69
    

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70. @jtdowney 70
    

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71. @jtdowney 71
    

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72. @jtdowney 72
    

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73. @jtdowney 73
    

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74. Hostname
    verification
    @jtdowney 74
    

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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
    

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76. Pitfalls
    1. Not verifying the certificate chain or hostname
    2. Misconfigured server settings
    3. Using a broken library
    @jtdowney 76
    

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77. @jtdowney 77
    

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

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

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

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81. Pitfalls
    1. Not verifying the certificate chain or hostname
    2. Misconfigured server settings
    3. Using a broken library
    @jtdowney 81
    

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82. @jtdowney 82
    

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83. @jtdowney 83
    

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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
    

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85. Trust
    @jtdowney 85
    

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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
    

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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
    

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88. @jtdowney 88
    

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89. Certificate
    Pinning
    @jtdowney 89
    

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90. @jtdowney 90
    

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91. Recommendations
    • Think about what organizations you really
    trust
    • Investigate certificate pinning for your apps
    @jtdowney 91
    

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92. @jtdowney 92
    

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

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

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95. Questions
    John Downey | @jtdowney
    @jtdowney 95
    

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96. Bonus Round
    @jtdowney 96
    

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97. Quantum
    Computers
    @jtdowney 97
    

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

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99. @jtdowney 99
    

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100. @jtdowney 100
     

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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
     

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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
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