Keystore SPI: Add SecurityLevelEnum to KeyProperties

This patch adds the SecurityLevelEnum to KeyProperties. This enum can be
used by the public API surface to express levels of enforcements of key
properties. And to select a designated residence for a newly generated
or imported key.

The values UNKNOWN and UNKNOWN_SECURE are used to convey to older target
APIs API levels that have not been defined when they where published.

Test: None
Change-Id: I88681f21b8a8ea9a383d32ba99f3ab7d7c8909c3

4 files changed, 95 insertions, 0 deletions

diff --git a/api/current.txt b/api/current.txt
index c2e75cd14968..560b5f6c5cb0 100644
--- a/api/current.txt
+++ b/api/current.txt
@@ -42868,6 +42868,11 @@ package android.security.keystore {
     field public static final int PURPOSE_SIGN = 4; // 0x4
     field public static final int PURPOSE_VERIFY = 8; // 0x8
     field public static final int PURPOSE_WRAP_KEY = 32; // 0x20
+    field public static final int SECURITY_LEVEL_SOFTWARE = 0; // 0x0
+    field public static final int SECURITY_LEVEL_STRONGBOX = 2; // 0x2
+    field public static final int SECURITY_LEVEL_TRUSTED_ENVIRONMENT = 1; // 0x1
+    field public static final int SECURITY_LEVEL_UNKNOWN = -2; // 0xfffffffe
+    field public static final int SECURITY_LEVEL_UNKNOWN_SECURE = -1; // 0xffffffff
     field public static final String SIGNATURE_PADDING_RSA_PKCS1 = "PKCS1";
     field public static final String SIGNATURE_PADDING_RSA_PSS = "PSS";
   }
diff --git a/core/api/current.txt b/core/api/current.txt
index ab0aec73346b..0aa24cf50830 100644
--- a/core/api/current.txt
+++ b/core/api/current.txt
@@ -41036,6 +41036,11 @@ package android.security.keystore {
     field public static final int PURPOSE_SIGN = 4; // 0x4
     field public static final int PURPOSE_VERIFY = 8; // 0x8
     field public static final int PURPOSE_WRAP_KEY = 32; // 0x20
+    field public static final int SECURITY_LEVEL_SOFTWARE = 0; // 0x0
+    field public static final int SECURITY_LEVEL_STRONGBOX = 2; // 0x2
+    field public static final int SECURITY_LEVEL_TRUSTED_ENVIRONMENT = 1; // 0x1
+    field public static final int SECURITY_LEVEL_UNKNOWN = -2; // 0xfffffffe
+    field public static final int SECURITY_LEVEL_UNKNOWN_SECURE = -1; // 0xffffffff
     field public static final String SIGNATURE_PADDING_RSA_PKCS1 = "PKCS1";
     field public static final String SIGNATURE_PADDING_RSA_PSS = "PSS";
   }
diff --git a/core/java/android/security/keymaster/KeymasterDefs.java b/core/java/android/security/keymaster/KeymasterDefs.java
index f08756a015b2..e32ffa6e9d05 100644
--- a/core/java/android/security/keymaster/KeymasterDefs.java
+++ b/core/java/android/security/keymaster/KeymasterDefs.java
@@ -157,6 +157,11 @@ public final class KeymasterDefs {
     public static final int HW_AUTH_PASSWORD = 1 << 0;
     public static final int HW_AUTH_BIOMETRIC = 1 << 1;
 
+    // Security Levels.
+    public static final int KM_SECURITY_LEVEL_SOFTWARE = 0;
+    public static final int KM_SECURITY_LEVEL_TRUSTED_ENVIRONMENT = 1;
+    public static final int KM_SECURITY_LEVEL_STRONGBOX = 2;
+
     // Error codes.
     public static final int KM_ERROR_OK = 0;
     public static final int KM_ERROR_ROOT_OF_TRUST_ALREADY_SET = -1;
diff --git a/keystore/java/android/security/keystore/KeyProperties.java b/keystore/java/android/security/keystore/KeyProperties.java
index c58a1236d475..63ff866e7a06 100644
--- a/keystore/java/android/security/keystore/KeyProperties.java
+++ b/keystore/java/android/security/keystore/KeyProperties.java
@@ -771,4 +771,84 @@ public abstract class KeyProperties {
         }
         return result;
     }
+
+    /**
+     * @hide
+     */
+    @Retention(RetentionPolicy.SOURCE)
+    @IntDef(prefix = { "SECURITY_LEVEL_" }, value = {
+            SECURITY_LEVEL_UNKNOWN,
+            SECURITY_LEVEL_UNKNOWN_SECURE,
+            SECURITY_LEVEL_SOFTWARE,
+            SECURITY_LEVEL_TRUSTED_ENVIRONMENT,
+            SECURITY_LEVEL_STRONGBOX,
+    })
+    public @interface SecurityLevelEnum {}
+
+    /**
+     * This security level indicates that no assumptions can be made about the security level of the
+     * respective key.
+     */
+    public static final int SECURITY_LEVEL_UNKNOWN = -2;
+    /**
+     * This security level indicates that due to the target API level of the caller no exact
+     * statement can be made about the security level of the key, however, the security level
+     * can be considered is at least equivalent to {@link #SECURITY_LEVEL_TRUSTED_ENVIRONMENT}.
+     */
+    public static final int SECURITY_LEVEL_UNKNOWN_SECURE = -1;
+
+    /** Indicates enforcement by system software. */
+    public static final int SECURITY_LEVEL_SOFTWARE = 0;
+
+    /** Indicates enforcement by a trusted execution environment. */
+    public static final int SECURITY_LEVEL_TRUSTED_ENVIRONMENT = 1;
+
+    /**
+     * Indicates enforcement by environment meeting the Strongbox security profile,
+     * such as a secure element.
+     */
+    public static final int SECURITY_LEVEL_STRONGBOX = 2;
+
+    /**
+     * @hide
+     */
+    public abstract static class SecurityLevel {
+        private SecurityLevel() {}
+
+        /**
+         * @hide
+         */
+        public static int toKeymaster(int securityLevel) {
+            switch (securityLevel) {
+                case SECURITY_LEVEL_SOFTWARE:
+                    return KeymasterDefs.KM_SECURITY_LEVEL_SOFTWARE;
+                case SECURITY_LEVEL_TRUSTED_ENVIRONMENT:
+                    return KeymasterDefs.KM_SECURITY_LEVEL_TRUSTED_ENVIRONMENT;
+                case SECURITY_LEVEL_STRONGBOX:
+                    return KeymasterDefs.KM_SECURITY_LEVEL_STRONGBOX;
+                default:
+                    throw new IllegalArgumentException("Unsupported security level: "
+                            + securityLevel);
+            }
+        }
+
+        /**
+         * @hide
+         */
+        @NonNull
+        public static int fromKeymaster(int securityLevel) {
+            switch (securityLevel) {
+                case KeymasterDefs.KM_SECURITY_LEVEL_SOFTWARE:
+                    return SECURITY_LEVEL_SOFTWARE;
+                case KeymasterDefs.KM_SECURITY_LEVEL_TRUSTED_ENVIRONMENT:
+                    return SECURITY_LEVEL_TRUSTED_ENVIRONMENT;
+                case KeymasterDefs.KM_SECURITY_LEVEL_STRONGBOX:
+                    return SECURITY_LEVEL_STRONGBOX;
+                default:
+                    throw new IllegalArgumentException("Unsupported security level: "
+                            + securityLevel);
+            }
+        }
+    }
+
 }