Port MASTG-TEST-0015 to v2 (by @guardsquare)

tests-beta/android/MASVS-CRYPTO/MASTG-TEST-0x15-1.md

@@ -0,0 +1,46 @@
+---
+platform: android
+title: Asymmetric key pair used for multiple purposes
+id: MASTG-TEST-0x15-1
+type: [static, dynamic]
+weakness: MASWE-0012
+---
+
+## Overview
+
+In general, ["a single key shall be used for only one purpose (e.g., encryption, integrity
+authentication, key wrapping, random bit generation, or digital signatures)"](https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-57pt1r5.pdf).
+In the case of asymmetric encryption, reusing the same key pair for multiple different cryptographic processes (e.g. signatures vs encryption) may weaken the security provided by those processes.
+
+This does not apply to the cases where the same process can provide multiple services, e.g., when a single digital signature provides integrity authentication and source authentication.
+Check ["NIST.SP.800-57pt1r5"](https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-57pt1r5.pdf) for details.
+
+## Steps
+
+1. Use either @MASTG-TECH-0014 or @MASTG-TECH-0033 to identify all the instance where asymmetric cryptography is used.
+You can look for uses of:
+    - classes `Cipher`, `MessageDigest`, `Signature`, `KeyPair`, `KeyGenParameterSpec`
+    - interfaces `PrivateKey`, `PublicKey`
+    - functions `getInstance`, `generateKeyPair`
+    - exceptions `KeyStoreException`, `CertificateException`, `NoSuchAlgorithmException`
+    - classes importing `java.security.*`, `javax.crypto.*`, `android.security.*`, `android.security.keystore.*`
+
+## Observation
+
+The observation contains all the uses of each public and private keys with backtraces to know the locations of the `KeyPair` object.
+
+## Evaluation
+
+Reverse engineer the observed backtraces and try to determine the processes and purposes for which each `KeyPair` object is being used:
+
+1. For each identified instance, identify the `KeyPair` objects used and how they are created or generated.
+
+1. For each `PrivateKey` and `PublicKey` identify for which processes it is being used: signing/verification and encryption/decryption.
+    1. If a `KeyStore` is being used, you should check the [`KeyProperties`](https://developer.android.com/reference/android/security/keystore/KeyProperties) that are being defined in the `KeyPair` generation.
+    1. Otherwise, you need to search where the `PrivateKey` and `PublicKey` of each `KeyPair` are being used, and check if they are being used in `Cipher` or `Signature` objects.
+
+The test case fails if the keys of a `KeyPair` is found being used for two distinct processes (i.e., signatures AND encryption).
+
+## References
+
+- [NIST.SP.800 - Recommendation for Key Management (part 1)](https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-57pt1r5.pdf)

tests-beta/android/MASVS-CRYPTO/MASTG-TEST-0x15-2.md

@@ -0,0 +1,45 @@
+---
+platform: android
+title: Symmetric key used for multiple purposes
+id: MASTG-TEST-0x15-2
+type: [static, dynamic]
+weakness: MASWE-0012
+---
+
+## Overview
+
+In general, ["a single key shall be used for only one purpose (e.g., encryption, integrity
+authentication, key wrapping, random bit generation, or digital signatures)"](https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-57pt1r5.pdf).
+Reusing the same key multiple purposes may weaken its security or increase the impact of one key being compromised.
+
+This does not apply to the cases where the same process can provide multiple services, e.g., a single symmetric key can be used to encrypt and authenticate data in a single operation (one authenticated-encryption operation instead of separate encryption and authentication operations).
+Check ["NIST.SP.800-57pt1r5"](https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-57pt1r5.pdf) for details.
+
+## Steps
+
+1. Use either @MASTG-TECH-0014 or @MASTG-TECH-0033 to identify all the where symmetric cryptography is used.
+You can look for uses of:
+    - classes `Cipher`, `Mac`,
+    - interfaces `Key`, `SecretKey`
+    - functions `getInstance`, `generateKey`, `generateKeyPair`
+    - exceptions `KeyStoreException`, `CertificateException`, `NoSuchAlgorithmException`
+    - classes importing `java.security.*`, `javax.crypto.*`, `android.security.*`, `android.security.keystore.*`
+
+## Observation
+
+The observation contains all the uses of each `Key` object with backtraces to know the locations.
+
+## Evaluation
+
+Reverse engineer the observed backtraces and try to determine the "business purpose" for which each `Key` object is being used:
+
+1. For each identified instance, identify the process for which cryptography is being used:
+    - for encryption/decryption - to ensure data confidentiality
+    - for maintenance - to protect keys during certain sensitive operations (such as being imported to the `KeyStore`)
+1. Identify the business logic which uses identified instances of cryptography.
+
+The test case fails if there is a `Key` object that is being used for multiple business purposes.
+
+## References
+
+- [NIST.SP.800 - Recommendation for Key Management (part 1)](https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-57pt1r5.pdf)

tests/android/MASVS-CRYPTO/MASTG-TEST-0015.md

@@ -8,6 +8,9 @@ title: Testing the Purposes of Keys
 masvs_v1_levels:
 - L1
 - L2
+status: deprecated
+covered_by: ['MASTG-TEST-0x15-1','MASTG-TEST-0x15-2']
+deprecation_reason: New version available in MASTG V2
 ---
 
 ## Overview