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
 54
 countries Over 22,300
 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
6. CERTIFICATE Electronic document that proves ownership of a public key X.509 - structure TLS/SSL, electronic signatures CERTIFICATE
7. IDENTITY CERTIFICATE
8. PUBLIC KEY CERTIFICATE = IDENTITY + +
9. SIGNED BY CA CERTIFICATE = IDENTITY + PUBLIC KEY + +
10. KEYS ASYMMETRIC CRYPTOGRAPHY
11. KEYS ▸ Private (owner) ▸ Decrypts messages ▸ Calculates signatures ▸ Public (shared) ▸ Encrypts messages ▸ Confirms signatures
12. DIGITAL SIGNATURE ▸ Calculate a digest/hash of the message ▸ Sender encrypts with private key ▸ Recipient decrypts with public key DIGITAL SIGNATURE
13. CERTIFICATE = IDENTITY + PUBLIC KEY + SIGNED BY CA + +
14. CERTIFICATE AUTHORITY CA Trusted entity that issues digital certificates.
15. CA CA CERTIFICATE ▸ Self-signed certificate ▸ Browsers, Android, OSX ▸ Comodo, IdenTrust, Symantec, GoDaddy, Let’s Encrypt ▸ Impact of updates!
16. CA - DOMAIN VS EXTENDED VALIDATION
17. END CERTIFICATE
18. INTERMEDIATE CERTIFICATE
19. ROOT CERTIFICATE
20. CERTIFICATES CERTIFICATE CHAINS
21. CA SUBVERSION ▸ Primary risk key theft ▸ Scheme flawed ▸ HSM for key storage ▸ Offline
22. TRUST ANDROID ▸ Unknown CA ▸ Self-signed ▸ No intermediate cert on server
23. SIGNING ANDROID APPLICATIONS
24. SIGNING ANDROID APPLICATIONS ▸ Generate a key and keystore ▸ Sign your application
25. SIGNING ANDROID APPLICATIONS - NEW KEY STORE
26. SIGNING ANDROID APPLICATIONS - SIGN THE APP
27. SIGNING ANDROID APPLICATIONS - SIGN THE APP ALTERNATIVE ▸ keytool to generate a key ▸ zipalign to align unsigned apk ▸ jarsigner to sign aligned apk
28. SIGN THE APK DECISIONS TO BE MADE ▸ Who will be responsible for the signing key?
29. WE THE DEVELOPERS
30. WE THE DEVELOPERS EXPECTATIONS ▸ Application can be updated throughout its lifetime
31. WE THE DEVELOPERS PREREQUISITES ▸ Signing key must be safe ▸ Signing key must be accessible
32. WE THE DEVELOPERS REALITY ▸ People spill coffee ▸ People switch companies
33. WE THE DEVELOPERS REALITY NIGHTMARE signingConfigs { release { storeFile file("/not_where_you_think_it_is/ks.jks") storePassword "password" keyAlias "my-alias" keyPassword "password" } }
34. GOOGLE PLAY APP SIGNING https://goo.gl/3aCBeC
35. GOOGLE PLAY APP SIGNING DECISION IS PERMANENT
36. GOOGLE PLAY APP SIGNING NEW APPS ▸ Create upload key and sign apk ▸ Google Play App Signing ->Accept ▸ Upload signed apk ▸ Register app signing key!
37. GOOGLE PLAY APP SIGNING EXISTING APPS ▸ Opt-in ▸ Submit signing key to Google and ▸ Create upload key ▸ Update keystores ▸ Continue signing with upload key
38. WE THE DEVELOPERS MITIGATION ▸ Upload key lost/compromised?
39. SIGN THE APK DECISIONS TO BE MADE ▸ Who will be responsible for the signing key? ▸ Applicable to all modules/applications/flavours?
40. SIGN THE APK PROS AND CONS ▸ Modularity ▸ Permission based sharing ▸ update-able ▸ Single point of failure
42. ANDROID KEYSTORE SYSTEM
43. ANDROID KEYSTORE SYSTEM The Android Keystore system safeguards your cryptographic keys from extraction. ANDROID KEYSTORE SYSTEM
44. STORAGE SHOULD I KEEP SENSITIVE DATA IN MY APP?
45. ANDROID KEYSTORE SYSTEM EXTRACTION PREVENTION ▸ System process in charge of cryptographic operations ▸ Key material bound to TEE, SE
46. ANDROID KEYSTORE SYSTEM KEY USE AUTHORIZATIONS ▸ Once defined, immutable ▸ Cryptography ▸ Temporal validity interval ▸ User authentication
47. ANDROID KEYSTORE SYSTEM UTILITY METHODS ▸ KeyInfo.isInsideSecurityHardware() ▸ KeyInfo.isUserAuthenticationRequirementEnforcedBySecureHardware()
48. ANDROID KEYSTORE SYSTEM KEYCHAIN VS ANDROID KEYSTORE PROVIDER ▸ System-wide credentials ▸ System provided UI ▸ App-specific credentials ▸ No interaction ▸ AndroidKeystore API 18
49. 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();
50. 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();
51. 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();
52. LISTING ENTRIES KeyStore ks = KeyStore.getInstance("AndroidKeyStore"); ks.load(null); Enumeration<String> aliases = ks.aliases();
53. LISTING ENTRIES KeyStore ks = KeyStore.getInstance("AndroidKeyStore"); ks.load(null); Enumeration<String> aliases = ks.aliases();
54. SIGNING DATA Signature s = Signature.getInstance("SHA256withECDSA"); s.initSign(((PrivateKeyEntry) entry).getPrivateKey()); s.update(data); byte[] signature = s.sign();
55. SIGNING DATA Signature s = Signature.getInstance("SHA256withECDSA"); s.initSign(((PrivateKeyEntry) entry).getPrivateKey()); s.update(data); byte[] signature = s.sign();
56. VERIFYING SIGNATURES Signature s = Signature.getInstance("SHA256withECDSA"); s.initVerify(((PrivateKeyEntry) entry).getCertificate()); s.update(data); boolean valid = s.verify(signature);
57. VERIFYING SIGNATURES Signature s = Signature.getInstance("SHA256withECDSA"); s.initVerify(((PrivateKeyEntry) entry).getCertificate()); s.update(data); boolean valid = s.verify(signature);
58. KEY ATTESTATION KEY ATTESTATION ▸ Is a key stored in hardware-backed keystore ▸ Small number of devices API 24+
59. TEXT
60. FRAGMENTATION ANDROID P(ANCAKE?) ▸ Key rotation ▸ StrongBox Keymaster (HSM) ▸ …
61. GOOGLE TRANSPARENCY REPORT https://transparencyreport.google.com/
62. QUALYS CHECK YOUR DOMAIN (NOW!) https://www.ssllabs.com/ssltest/analyze.html
63. THANK YOU! Q&A