Sign here, please!

An application ID might define your app among all others, but its signature is what proves and confirms its identity and integrity. From working in distributed teams to fending off fraudulent clones of your application, you eventually come to understand the importance of signatures.

In this talk we’ll take a deep dive into the Android keystore system, certificates and signatures, and go over key points necessary for any application’s long and productive life. Also, we will cover some security tips and tricks that will help ensure your app is safe to use, even if the users are faced with its evil twin.

At the end you should walk away with a deeper insight into everyday mechanisms that are often taken for granted, and the impact that they have on your users’ security.

Transcript

1. SIGN HERE, PLEASE! ANA BAOTIĆ @abaotic
4. Present in
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 highly committed employees 6th
 largest software & services vendor in Europe 1,813
 m EUR sales revenues in 2016 176
 m EUR operating profit in 2016 1bln
 EUR market capitalization • Founded in 1991 • 6th largest software producer in Europe • Traded on the WSE, included in the WIG20 blue chip index • International presence ASSECO at a glance
5. CERTIFICATE @abaotic
6. CERTIFICATE Electronic document that proves ownership of a public key CERTIFICATE @abaotic
7. CERTIFICATE Electronic document that proves ownership of a public key X.509 - structure CERTIFICATE @abaotic
8. CERTIFICATE Electronic document that proves ownership of a public key X.509 - structure TLS, electronic signatures CERTIFICATE @abaotic
9. IDENTITY CERTIFICATE @abaotic
10. PUBLIC KEY CERTIFICATE = IDENTITY + + @abaotic
11. KEYS ASYMMETRIC CRYPTOGRAPHY @abaotic
12. KEYS ASYMMETRIC CRYPTOGRAPHY 13924097109571903750931790573190570913759031790579374037105973109570931750937109570… f(x) @abaotic
13. KEYS - ASYMMETRIC CRYPTOGRAPHY ▸ Private (owner) ▸ Public (shared) @abaotic
14. KEYS ▸ Private (owner) ▸ Decrypts messages ▸ Public (shared) ▸ Encrypts messages @abaotic
15. KEYS ▸ Private (owner) ▸ Decrypts messages ▸ Calculates signatures ▸ Public (shared) ▸ Encrypts messages ▸ Confirms signatures @abaotic
16. DIGITAL SIGNATURE ▸ authentication, non-repudiation and integrity DIGITAL SIGNATURE @abaotic
17. DIGITAL SIGNATURE ▸ authentication, non-repudiation and integrity ▸ Calculate a digest/hash of the message DIGITAL SIGNATURE @abaotic
18. DIGITAL SIGNATURE ▸ authentication, non-repudiation and integrity ▸ Calculate a digest/hash of the message ▸ Sender encrypts with private key DIGITAL SIGNATURE @abaotic
19. DIGITAL SIGNATURE ▸ authentication, non-repudiation and integrity ▸ Calculate a digest/hash of the message ▸ Sender encrypts with private key ▸ Recipient decrypts with public key DIGITAL SIGNATURE @abaotic
20. SIGNED BY CA CERTIFICATE = IDENTITY + PUBLIC KEY + + @abaotic
21. CERTIFICATE = IDENTITY + PUBLIC KEY + SIGNED BY CA + + @abaotic
22. CERTIFICATE AUTHORITY CA Trusted entity that issues digital certificates. @abaotic
23. CA CA CERTIFICATE ▸ Self-signed certificate ▸ Browsers, Android, OSX ▸ Comodo, IdenTrust, Symantec, GoDaddy, Let’s Encrypt ▸ Impact of updates! @abaotic
24. END CERTIFICATE
25. INTERMEDIATE CERTIFICATE
26. ROOT CERTIFICATE
27. CERTIFICATES CERTIFICATE CHAINS @abaotic
28. CA - DOMAIN VS EXTENDED VALIDATION @abaotic
29. CA SUBVERSION ▸ Primary risk key theft ▸ Scheme flawed ▸ HSM for key storage ▸ Offline @abaotic
30. TRUST ANDROID ▸ Unknown CA/Self-signed ▸ No intermediate cert on server @abaotic
31. SIGNING ANDROID APPLICATIONS @abaotic
32. SIGNING ANDROID APPLICATIONS ▸ Generate a key and keystore ▸ Sign your application @abaotic
33. SIGNING ANDROID APPLICATIONS - NEW KEY STORE @abaotic
34. SIGNING ANDROID APPLICATIONS - SIGN THE APP @abaotic
35. SIGNING ANDROID APPLICATIONS - SIGN THE APP ALTERNATIVE ▸ keytool to generate a key ▸ zipalign to align unsigned apk ▸ jarsigner to sign aligned apk @abaotic
36. SIGN THE APK DECISIONS TO BE MADE ▸ Who will be responsible for the signing key? @abaotic
37. WE THE DEVELOPERS
38. WE THE DEVELOPERS EXPECTATIONS ▸ Application can be updated throughout its lifetime @abaotic
39. WE THE DEVELOPERS PREREQUISITES ▸ Signing key must be safe ▸ Signing key must be accessible @abaotic
40. WE THE DEVELOPERS REALITY ▸ People spill coffee ▸ People switch companies @abaotic
41. WE THE DEVELOPERS REALITY NIGHTMARE signingConfigs { release { storeFile file("/not_where_you_think_it_is/ks.jks") storePassword "password" keyAlias "my-alias" keyPassword "password" } } @abaotic
42. GOOGLE PLAY APP SIGNING https://goo.gl/3aCBeC
43. GOOGLE PLAY APP SIGNING DECISION IS PERMANENT @abaotic
44. GOOGLE PLAY APP SIGNING NEW APPS ▸ Create upload key and sign apk ▸ Google Play App Signing ->Accept ▸ Upload signed apk ▸ Register app signing key! @abaotic
45. GOOGLE PLAY APP SIGNING EXISTING APPS ▸ Opt-in ▸ Submit signing key to Google and ▸ Create upload key ▸ Update keystores ▸ Continue signing with upload key @abaotic
46. WE THE DEVELOPERS MITIGATION ▸ Upload key lost/compromised? @abaotic
47. SIGN THE APK DECISIONS TO BE MADE ▸ Who will be responsible for the signing key? ▸ Applicable to all modules/applications/flavours? @abaotic
48. SIGN THE APK PROS AND CONS ▸ Modularity ▸ Permission based sharing ▸ update-able ▸ Single point of failure @abaotic
50. ANDROID KEYSTORE SYSTEM @abaotic
51. ANDROID KEYSTORE SYSTEM The Android Keystore system safeguards your cryptographic keys from extraction. ANDROID KEYSTORE SYSTEM @abaotic
52. STORAGE SHOULD I KEEP SENSITIVE DATA IN MY APP? @abaotic
53. ANDROID KEYSTORE SYSTEM EXTRACTION PREVENTION ▸ System process in charge of cryptographic operations ▸ Key material bound to TEE, SE @abaotic
54. ANDROID KEYSTORE SYSTEM KEY USE AUTHORIZATIONS ▸ Once defined, immutable ▸ Cryptography ▸ Temporal validity interval ▸ User authentication @abaotic
55. ANDROID KEYSTORE SYSTEM UTILITY METHODS ▸ KeyInfo.isInsideSecurityHardware() ▸ KeyInfo.isUserAuthenticationRequirementEnforcedBySecureHardware() @abaotic
56. ANDROID KEYSTORE SYSTEM KEYCHAIN VS ANDROID KEYSTORE PROVIDER ▸ System-wide credentials ▸ System provided UI ▸ App-specific credentials ▸ No interaction ▸ AndroidKeystore API 18 @abaotic
57. KEY PAIR ENTRY IN KEYSTORE KeyPairGenerator kpg = KeyPairGenerator.getInstance( KeyProperties.KEY_ALGORITHM_EC, "AndroidKeyStore"); kpg.initialize(new KeyGenParameterSpec.Builder( alias, KeyProperties.PURPOSE_SIGN | KeyProperties.PURPOSE_VERIFY) .setDigests(KeyProperties.DIGEST_SHA256, KeyProperties.DIGEST_SHA512) .build()); KeyPair kp = kpg.generateKeyPair(); GENERATE KEYPAIR @abaotic
58. KEY PAIR ENTRY IN KEYSTORE KeyPairGenerator kpg = KeyPairGenerator.getInstance( KeyProperties.KEY_ALGORITHM_EC, "AndroidKeyStore"); kpg.initialize(new KeyGenParameterSpec.Builder( alias, KeyProperties.PURPOSE_SIGN | KeyProperties.PURPOSE_VERIFY) .setDigests(KeyProperties.DIGEST_SHA256, KeyProperties.DIGEST_SHA512) .build()); KeyPair kp = kpg.generateKeyPair(); GENERATE KEYPAIR @abaotic
59. KEY PAIR ENTRY IN KEYSTORE KeyPairGenerator kpg = KeyPairGenerator.getInstance( KeyProperties.KEY_ALGORITHM_EC, "AndroidKeystore"); kpg.initialize(new KeyGenParameterSpec.Builder( alias, KeyProperties.PURPOSE_SIGN | KeyProperties.PURPOSE_VERIFY) .setDigests(KeyProperties.DIGEST_SHA256, KeyProperties.DIGEST_SHA512) .build()); KeyPair kp = kpg.generateKeyPair(); GENERATE KEYPAIR @abaotic
60. LISTING ENTRIES KeyStore ks = KeyStore.getInstance("AndroidKeyStore"); ks.load(null); Enumeration<String> aliases = ks.aliases(); LIST ENTRIES @abaotic
61. LISTING ENTRIES KeyStore ks = KeyStore.getInstance("AndroidKeyStore"); ks.load(null); Enumeration<String> aliases = ks.aliases(); LIST ENTRIES @abaotic
62. SIGNING DATA Signature s = Signature.getInstance("SHA256withECDSA"); s.initSign(((PrivateKeyEntry) entry).getPrivateKey()); s.update(data); byte[] signature = s.sign(); SIGN DATA @abaotic
63. SIGNING DATA Signature s = Signature.getInstance("SHA256withECDSA"); s.initSign(((PrivateKeyEntry) entry).getPrivateKey()); s.update(data); byte[] signature = s.sign(); SIGN DATA @abaotic
64. VERIFYING SIGNATURES Signature s = Signature.getInstance("SHA256withECDSA"); s.initVerify(((PrivateKeyEntry) entry).getCertificate()); s.update(data); boolean valid = s.verify(signature); VERIFY SIGNATURES @abaotic
65. VERIFYING SIGNATURES Signature s = Signature.getInstance("SHA256withECDSA"); s.initVerify(((PrivateKeyEntry) entry).getCertificate()); s.update(data); boolean valid = s.verify(signature); VERIFY SIGNATURES @abaotic
66. KEY ATTESTATION KEY ATTESTATION ▸ Is a key stored in hardware-backed keystore ▸ Small number of devices API 24+ @abaotic
67. TEXT
68. FRAGMENTATION ANDROID P(ANCAKE?) ▸ Key rotation ▸ StrongBox Keymaster (HSM) ▸ … @abaotic
69. GOOGLE TRANSPARENCY REPORT https://transparencyreport.google.com/ @abaotic
70. QUALIS CHECK YOUR DOMAIN (NOW!) https://www.ssllabs.com/ssltest @abaotic
72. THANK YOU! Q&A @abaotic