Securing Your HTTP API with Hawk (PHP Tour Luxembourg 2015)

Spending too much time working on a custom authentication scheme for your API? Concerned about how secure your one-off implementation actually is? Learn more about the Hawk HTTP authentication scheme. It provides partial cryptographic verification for both requests and responses and it is supported by multiple languages. With Hawk securing your HTTP API you can rest easy knowing that your server and clients can trust the data they share so that you can focus on building your application's killer features.

Transcript

1. Securing Your HTTP API with Hawk Beau Simensen @beausimensen joind.in/14270
2. Hawk
3. HTTP Authentication
4. MAC Message Authentication Code
5. Partial Cryptographic Verification
6. Problems
7. Can you trust the channel?
8. Can you trust the channel? HTTPS
9. Do you know who made the request?
10. Do you know who made the request? Cookie
11. Do you know who made the request? HTTP Header
12. Do you know who made the request? From the payload
13. Do you trust the authentication method?
14. Do you trust the authentication method? Hint: If you are using HTTP Basic Auth, the answer is "No."
15. Do you trust the authentication method? Cookie Encryption
16. Do you trust the authentication method? Digest
17. Can you trust the authentication is still valid?
18. POST /buy HTTP/1.1 Host: example.com Content-Type: application/x-www-form-urlencoded;charset=utf-8 Authorization: SomeLegitimateAuthorizationValue item=something_reasonable&qty=1 ... seconds, minutes, days, months, years... POST /buy HTTP/1.1 Host: example.com Content-Type: application/x-www-form-urlencoded;charset=utf-8 Authorization: SomeLegitimateAuthorizationValue item=something_reasonable&qty=1
19. Can you trust the authentication is still valid? Expiration
20. Can you trust the request itself?
21. POST /buy HTTP/1.1 Host: example.com Content-Type: application/x-www-form-urlencoded;charset=utf-8 Authorization: SomeLegitimateAuthorizationValue item=something_reasonable&qty=1 ... versus ... POST /buy HTTP/1.1 Host: example.com Content-Type: application/x-www-form-urlencoded;charset=utf-8 Authorization: SomeLegitimateAuthorizationValue item=something_expensive&qty=3
22. Can you trust the request itself? Nonce
23. Can you trust the request itself? Message signing
24. Can you trust the served response?
25. POST /validate HTTP/1.1 Host: id.example.com Referer: http://id.example.com/login Content-Type: application/x-www-form-urlencoded;charset=utf-8 user=admin&password=pa55word Compare this response... HTTP 302 Location: http://app.example.com ... to this response... HTTP 302 Location: http://id.examp1e.com/login
26. Can you trust the served response? Message signing
27. Solutions
28. AWS Amazon Web Services
29. Custom
30. Query Auth Jeremy Kendall • @JeremyKendall
31. Query Auth is Based on AWS Signature V2
32. Hawk
33. Eran Hammer @eranhammer
34. HTTP Authentication: MAC Access Authentication 1 draft-hammer-oauth-v2-mac-token-05 proposal
35. OAuth 2.0 Former lead author and editor
36. They say the road to hell is paved with good intentions. Well, that’s OAuth 2.0. 1 Eran Hammer, "OAuth 2.0 and the Road to Hell"
37. Does Hawk have a specification? Not so much
38. Welcome to Hawk Where the code is the specification
39. https://github.com/hueniverse/hawk
40. Tent.io
41. Language Support PHP • .NET • Java • JavaScript • Python Ruby • Go • Objective-C • C • Scala
42. https://github.com/dflydev/dflydev-hawk
43. Authentication Is NOT Authorization
44. Looking for an OAuth alternative? Check out Oz https://github.com/hueniverse/oz
45. Replay Attacks
46. This request an be made over and over again. Forever. POST /buy HTTP/1.1 Host: example.com Content-Type: application/x-www-form-urlencoded;charset=utf-8 Authorization: SomeLegitimateAuthorizationValue item=something_expensive&qty=3
47. Nonce + Timestamp
48. Nonce Client generated
49. Nonce Server enforced
50. Nonce unique(identifier, timestamp)
51. Timestamp Requests after expiration time are rejected by server
52. Timestamp Server can purge nonce values once expiration time has passed
53. Timestamp Client's clock must be in sync with the server's clock
54. Timestamp Skew Default 1 minute (+/-)
55. Timestamp Skew Server includes its time in bad timestamp responses
56. Timestamp Skew Client responsible for calculating offset for future requests
57. Credentials id, key, algorithm
58. id Like a username
59. key Like a password
60. key is never transmitted
61. Protect It!
62. Protocol Example
63. Client requests protected resource GET /resource/1?b=1&a=2 HTTP/1.1 Host: example.com:8000
64. Server challenges HTTP/1.1 401 Unauthorized WWW-Authenticate: Hawk
65. Previously obtained Hawk credentials: $credentials = [ 'id' => 'dh37fgj492je', 'key' => 'werxhqb98rpaxn39848xrunpaw3489ruxnpa98w4rxn', 'algorithm' => 'sha256', ];
66. Client generates a timestamp $timestamp = 1353832234;
67. Client generates a nonce $nonce = 'j4h3g2';
68. Normalized request string hawk.1.header\n 1353832234\n j4h3g2\n GET\n /resource/1?b=1&a=2\n example.com\n 8000\n \n some-app-ext-data\n \n
69. MAC is calculated // sha256 $algorithm = $credentials['algorithm']; // werxhqb98rpaxn39848xrunpaw3489ruxnpa98w4rxn $key = $credentials['key']; $hmac = hash_hmac($algorithm, $string, $key, true); $mac = base64_encode($hmac); Resulting MAC: 6R4rV5iE+NPoym+WwjeHzjAGXUtLNIxmo1vpMofpLAE=
70. Client includes authoriztaion header GET /resource/1?b=1&a=2 HTTP/1.1 Host: example.com:8000 Authorization: Hawk id="dh37fgj492je", ts="1353832234", nonce="j4h3g2",... Hawk id="dh37fgj492je", ts="1353832234", nonce="j4h3g2", ext="some-app-ext-data", mac="6R4rV5iE+NPoym+WwjeHzjAGXUtLNIxmo1vpMofpLAE="
71. Payload Validation Optional
72. Calculate hash hawk.1.payload application/json {prop:"Some Value"} Resulting hash: oULrzWdcgjMiuZ93IiKevos00WXKdXsv70Q9YSy6OfY=
73. Normalized request string hawk.1.header\n 1353832234\n j4h3g2\n GET\n /resource/1?b=1&a=2\n example.com\n 8000\n oULrzWdcgjMiuZ93IiKevos00WXKdXsv70Q9YSy6OfY=\n some-app-ext-data\n \n
74. MAC is calculated // sha256 $algorithm = $credentials['algorithm']; // werxhqb98rpaxn39848xrunpaw3489ruxnpa98w4rxn $key = $credentials['key']; $hmac = hash_hmac($algorithm, $string, $key, true); $mac = base64_encode($hmac); Resulting MAC: IJlWMFoE1I4hM5N7nFHpp3n84yU3qM4BTdd6i+Mxo3U=
75. GET /resource/1?b=1&a=2 HTTP/1.1 Host: example.com:8000 Content-type: application/json Authorization: Hawk id="dh37fgj492je", ts="1353832234", nonce="j4h3g2",... {prop: "Some Value"} Hawk id="dh37fgj492je", ts="1353832234", nonce="j4h3g2", hash="IJlWMFoE1I4hM5N7nFHpp3n84yU3qM4BTdd6i+Mxo3U=", ext="some-app-ext-data", mac="6R4rV5iE+NPoym+WwjeHzjAGXUtLNIxmo1vpMofpLAE="
76. Response Validation Optional
77. Server-Authorization uses the same credentials and other artifacts provided by the client ext & hash may be changed
78. Response includes Server-Authorization header HTTP 200 OK Server-Authorization: Hawk mac="XIJRsMl/4oL+nn+vK..." Hawk mac="XIJRsMl/4oL+nn+vKoeVZPdCHXB4yJkNnBbTbHFZUYE=", hash="f9cDF/TDm7TkYRLnGwRMfeDzT6LixQVLvrIKhh0vgmM=" ext="response-specific"
79. Bewit Single URI Authorization
80. Only supports GET & HEAD
81. Generate a Bewit $uri_to_be_shared = 'https://example.com/resource/1?b=1&a=2'; $bewit = $client->createBewit( $credentials, $uri_to_be_shared, 300, // ttl in seconds ['ext' => 'some-app-ext-data'] );
82. Normalized request string hawk.1.bewit\n 1431390129\n // ( now + ttl ) = expiration time! \n // no nonce GET\n /resource/1?b=1&a=2\n example.com\n 8000\n \n some-app-ext-data\n \n
83. MAC built the usual way We've seen this twice already...
84. Encode Bewit $id = 'id1234'; $exp = '1431390129'; $mac = '1VLyBgXcUovTDKwCiYJo+EuYaTZq8LIgICS7jxkGSIw='; $ext = 'some-app-ext-data'; // id1234\1431390129\1VLyBgXcUovTDKwCiYJo+E...jxkGSIw=\some-app-ext-data $bewit = implode('\\', [$id, $exp, $mac, $ext]); // aWQxMj...0LWRhdGE= $encoded = base64_encode($bewit); // aWQxMj...0LWRhdGE $stripped = str_replace( ['+', '/', '=', "\n"], ['-', '_', '', ''], $encoded );
85. Append Bewit to URI to be shared // https://example.com/resource/1?b=1&a=2&bewit=aWQxMj...0LWRhdGE $uri = $uri_to_be_shared . '&bewit='.$bewit;
87. Gotchas
88. Plaintext Credentials
89. Keys Transmission
90. Host Header
91. Only Host & Content-Type Headers are covered by the MAC
92. Bewit cannot be revoked
93. No spec
95. HTTP Authentication
96. MAC Message Authentication Code
97. Partial Cryptographic Verification
98. Increases trust in the request and the response
99. Language Support PHP • .NET • Java • JavaScript • Python Ruby • Go • Objective-C • C • Scala
100. joind.in/14270 questions? @beausimensen • @dflydev • @thatpodcast beau.io/talks • thatpodcast.io
101. Image Credits source • source • source • source • source • source • source • source • source