Man in the Middle? - No, thank you!

Many developers in encrypt confidential data on the way to the backend using SSL and have a false sense of security.

While SSL is suitable as a tool to ensure the confidentiality and integrity of data, it must be understood and used correctly. A publication of the University of Texas and Stanford University from October 2012 shows that some serious vulnerabilities can be overlooked, even when using renowned libraries and software packages.

Using an example iOS application the talk shows how attackers can take possession of supposedly safely transmitted data, and how this can be prevented effectively by means of SSL Certificate pinning.

First a few SSL basics and relevant attack vectors are explained, then ways to counteract them. While the example is based on iOS, the concepts can be applied to Android and other platforms, as well.

Transcript

1. No,$thank$you! MAN$IN$THE$MIDDLE$? Daniel$Schneller$–$CenterDevice$GmbH
2. SSL$–$and$you’re$done™
3. SSL$–$and$you’re$done™
4. SSL$–$and$you’re$done™ …are$you?
5. Mac$App$Store
6. Mac$App$Store
7. Mac$App$Store
8. Outbank
9. What$happened$to$SSL?
10. SSL$–$Chain$of$Trust
11. SSL$–$Chain$of$Trust Root$CA$Cer)ficate
12. SSL$–$Chain$of$Trust Root$CA$Cer)ficate $Intermediate$CA$Cer)ficate(s) issues
13. SSL$–$Chain$of$Trust Root$CA$Cer)ficate $Intermediate$CA$Cer)ficate(s) Leaf$Cer)ficate issues issues
14. SSL$–$Chain$of$Trust
15. SSL$–$Chain$of$Trust
16. SSL$–$Chain$of$Trust
17. SSL$–$Chain$of$Trust
18. SSL$–$Chain$of$Trust
19. SSL$–$Chain$of$Trust
20. Just$how$many$Root$CAs$ are$there?
21. System$Roots
22. System$Roots
23. System$Roots Windows$8:$~350 Mozilla:$~160 iOS$6:$~220
24. Man$In$The$Middle?
25. Man$In$The$Middle [Corporate]$Proxy Client
26. Man$In$The$Middle [Corporate]$Proxy Client
27. Man$In$The$Middle [Corporate]$Proxy Client
28. Man$In$The$Middle Website [Corporate]$Proxy Client
29. Man$In$The$Middle Website [Corporate]$Proxy Client
30. Man$In$The$Middle Website [Corporate]$Proxy Client
31. Man$In$The$Middle Website [Corporate]$Proxy Client
32. Man$In$The$Middle
33. Man$In$The$Middle
34. Man$In$The$Middle
35. Man$In$The$Middle
36. Man$In$The$Middle
37. Man$In$The$Middle
38. Consequences •Monitoring •ManipulaZon •Sent$and$received$data$affected •Chain\Of\Trust$formally$verified
39. Good$and$evil •Debugging •Reverse$Engineering •Security$Audits •Learning$and$Understanding
40. ReST$Debugging
41. Good$and$evil •Phishing •IdenZty$The` •Industrial$Espionage •…
42. Mac$App$Store
43. Mac$App$Store
44. Mac$App$Store
45. iTunes
46. iTunes
47. iTunes
48. Demo$1 Video$1 Video$2
49. Countermeasures
50. Reference$CerZficates
51. Reference$CerZficates •Client$bundles$server$cerZficate$as$a$ reference •Compare$reference$and$cerZficate$sent$by$ the$server$ •Connect$only$when$there’s$a$perfect$match
52. Reference$CerZficates $Client$App $Server
53. Reference$CerZficates $Client$App $Server ==
54. Reference$CerZficates SecTrustResultType evaluationResult; OSStatus status = SecTrustEvaluate(srvTrust, &evaluationResult); if (status == errSecSuccess) { if (evaluationResult == kSecTrustResultUnspecified) { // ... } } •Step$1:$$Validate$Chain\of\Trust
55. Reference$CerZficates SecTrustResultType evaluationResult; OSStatus status = SecTrustEvaluate(srvTrust, &evaluationResult); if (status == errSecSuccess) { if (evaluationResult == kSecTrustResultUnspecified) { // ... } } •Step$1:$$Validate$Chain\of\Trust
56. Reference$CerZficates •Step$1:$$Validate$Chain\of\Trust SecTrustResultType evaluationResult; OSStatus status = SecTrustEvaluate(srvTrust, &evaluationResult); if (status == errSecSuccess) { if (evaluationResult == kSecTrustResultUnspecified) { // ... } }
57. Reference$CerZficates •Step$1:$$Validate$Chain\of\Trust SecTrustResultType evaluationResult; OSStatus status = SecTrustEvaluate(srvTrust, &evaluationResult); if (status == errSecSuccess) { if (evaluationResult == kSecTrustResultUnspecified) { // ... } }
58. Reference$CerZficates •Step$1:$$Validate$Chain\of\Trust SecTrustResultType evaluationResult; OSStatus status = SecTrustEvaluate(srvTrust, &evaluationResult); if (status == errSecSuccess) { if (evaluationResult == kSecTrustResultUnspecified) { // ... } }
59. Reference$CerZficates •Step$1:$$Validate$Chain\of\Trust SecTrustResultType evaluationResult; OSStatus status = SecTrustEvaluate(srvTrust, &evaluationResult); if (status == errSecSuccess) { if (evaluationResult == kSecTrustResultUnspecified) { // ... } }
60. NSString *refPath = [[NSBundle mainBundle] pathForResource:@"reference" ofType:@"der"]; NSData *refCertData = [[NSData alloc] initWithContentsOfFile:refPath]; Reference$CerZficates •Step$2:$Load$Reference$CerZficate
61. NSString *refPath = [[NSBundle mainBundle] pathForResource:@"reference" ofType:@"der"]; NSData *refCertData = [[NSData alloc] initWithContentsOfFile:refPath]; Reference$CerZficates •Step$2:$Load$Reference$CerZficate
62. Reference$CerZficates •Step$2:$Load$Reference$CerZficate NSString *refPath = [[NSBundle mainBundle] pathForResource:@"reference" ofType:@"der"]; NSData *refCertData = [[NSData alloc] initWithContentsOfFile:refPath];
63. Reference$CerZficates BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); found = [refCertData isEqualToData:certData]; } •Step$3:$Compare$cerZficates
64. Reference$CerZficates BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); found = [refCertData isEqualToData:certData]; } •Step$3:$Compare$cerZficates
65. Reference$CerZficates •Step$3:$Compare$cerZficates BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); found = [refCertData isEqualToData:certData]; }
66. Reference$CerZficates •Step$3:$Compare$cerZficates BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); found = [refCertData isEqualToData:certData]; }
67. Reference$CerZficates •Step$3:$Compare$cerZficates BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); found = [refCertData isEqualToData:certData]; }
68. Reference$CerZficates •Step$3:$Compare$cerZficates BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); found = [refCertData isEqualToData:certData]; }
69. Reference$CerZficates •Step$3:$Compare$cerZficates BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); found = [refCertData isEqualToData:certData]; }
70. Demo$2 Video
71. FingerprinZng
72. FingerprinZng •Similar$to$Reference$CerZficate$approach •Compares$CerZficate$Fingerprint$against$ reference$value •Server$CerZficate$not$needed$in$the$client •Example:$$Apple$So`ware$Update
73. FingerprinZng$ $Client$App $Server 1122 3344 5566 7788 9900 AABB CCDD EEFF 9988 7766 SHA-1 Hash
74. FingerprinZng$ $Client$App $Server 1122 3344 5566 7788 9900 AABB CCDD EEFF 9988 7766 SHA-1 Hash
75. FingerprinZng$ $Client$App $Server == 1122 3344 5566 7788 9900 AABB CCDD EEFF 9988 7766 SHA-1 Hash 1122 3344 5566 7788 9900 AABB CCDD EEFF 9988 7766
76. FingerprinZng •Schrie$1:$Chain\of\Trust$validieren SecTrustResultType evaluationResult; OSStatus status = SecTrustEvaluate(srvTrust, &evaluationResult); if (status == errSecSuccess) { if (evaluationResult == kSecTrustResultUnspecified) { // ... } }
77. FingerprinZng static NSString* const kReferenceFP = @"AC .... DC"; BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); NSString* fingerprint = [self sha1:certData]; found = [kReferenceFP isEqualToString:fingerprint] } •Schrie$2:$Fingerprint$berechnen
78. FingerprinZng static NSString* const kReferenceFP = @"AC .... DC"; BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); NSString* fingerprint = [self sha1:certData]; found = [kReferenceFP isEqualToString:fingerprint] } •Schrie$2:$Fingerprint$berechnen
79. FingerprinZng •Schrie$2:$Fingerprint$berechnen static NSString* const kReferenceFP = @"AC .... DC"; BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); NSString* fingerprint = [self sha1:certData]; found = [kReferenceFP isEqualToString:fingerprint] }
80. FingerprinZng •Schrie$2:$Fingerprint$berechnen static NSString* const kReferenceFP = @"AC .... DC"; BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); NSString* fingerprint = [self sha1:certData]; found = [kReferenceFP isEqualToString:fingerprint] }
81. FingerprinZng •Schrie$2:$Fingerprint$berechnen static NSString* const kReferenceFP = @"AC .... DC"; BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); NSString* fingerprint = [self sha1:certData]; found = [kReferenceFP isEqualToString:fingerprint] }
82. FingerprinZng •Schrie$2:$Fingerprint$berechnen static NSString* const kReferenceFP = @"AC .... DC"; BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); NSString* fingerprint = [self sha1:certData]; found = [kReferenceFP isEqualToString:fingerprint] }
83. FingerprinZng •Schrie$2:$Fingerprint$berechnen static NSString* const kReferenceFP = @"AC .... DC"; BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); NSString* fingerprint = [self sha1:certData]; found = [kReferenceFP isEqualToString:fingerprint] }
84. FingerprinZng •Schrie$2:$Fingerprint$berechnen static NSString* const kReferenceFP = @"AC .... DC"; BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); NSString* fingerprint = [self sha1:certData]; found = [kReferenceFP isEqualToString:fingerprint] }
85. FingerprinZng •Schrie$2:$Fingerprint$berechnen static NSString* const kReferenceFP = @"AC .... DC"; BOOL found = NO; CFIndex crtCount = SecTrustGetCertificateCount(srvTrust); for (CFIndex j = 0; j < crtCount && !found; j++) { SecCertificateRef cert = SecTrustGetCertificateAtIndex(srvTrust, j); NSData* certData = CFBridgingRelease(SecCertificateCopyData(cert)); NSString* fingerprint = [self sha1:certData]; found = [kReferenceFP isEqualToString:fingerprint] }
86. Demo$3 Video
87. Caveats
88. Caveats •Change$of$CerZficate •Expired •Compromised •Update$app$with$plenty$of$lead$Zme •Temporarily$accept$old$and$new$ cerZficates
89. VariaZon
90. VariaZon •Check$Root\CerZficate$against$reference •Trade\Off:$Flexibility$vs.$Security •Updates$only$required$when$changing$ Root\CA
91. Conclusions
92. Conclusions •SSL$provides •ConfidenZality$(encrypted) •AuthenZcity •CA$system$(usually)$suffiecient •More$Security$=$More$Work
93. Make$informed$ decisions!
94. Links Sample,Code •github.com/dschneller/mitm\no\thank\you Tools •github.com/ADVTOOLS/ADVcerZficator •github.com/ADVTOOLS/ADVTrustStore •www.apple.com/support/iphone/enterprise •technet.microso`.com/en\us/library/ cc754841.aspx
95. Links TLS,Session,Cache •developer.apple.com/library/ios/#qa/qa1727 Root6CA,Lists •support.apple.com/kb/HT5012 •www.mozilla.org/projects/security/certs/ included/ •social.technet.microso`.com/wiki/contents/ arZcles/14215.windows\and\windows\phone\8\ ssl\root\cerZficate\program\member\cas.aspx •Android:$Sepngs–Security–Trusted$CredenZals
96. Thank$you!
97. QuesZons$? daniel.schneller@centerdevice.de $$$$$@dschneller
98. That’s$all.$Really.$:)
99. Demo$1 Standard$SSL,$ MITM$Root\CA$ not$installiert zurück