adding a security policy that allows access if and only if all given security policies allow access. this contributes to b/221149437 and is similar to cl/442582915

Author: marvinliu

binder/src/main/java/io/grpc/binder/SecurityPolicies.java

@@ -187,4 +187,35 @@ private static boolean checkPackageSignature(
     }
     return false;
   }
+
+  /**
+   * Creates a {@link SecurityPolicy} that allows access if and only if *all* of the specified
+   * {@code securityPolicies} allow access.
+   *
+   * @param securityPolicies the security policies that all must allow access.
+   * @throws NullPointerException if any of the inputs are {@code null}.
+   * @throws IllegalArgumentException if {@code securityPolicies} is empty.
+   */
+  public static SecurityPolicy allOf(SecurityPolicy... securityPolicies) {
+    Preconditions.checkNotNull(securityPolicies, "securityPolicies");
+    Preconditions.checkArgument(securityPolicies.length > 0, "securityPolicies must not be empty");
+
+    return allOfSecurityPolicy(securityPolicies);
+  }
+
+  private static SecurityPolicy allOfSecurityPolicy(SecurityPolicy... securityPolicies) {
+    return new SecurityPolicy() {
+      @Override
+      public Status checkAuthorization(int uid) {
+        for (SecurityPolicy policy : securityPolicies) {
+          Status checkAuth = policy.checkAuthorization(uid);
+          if (!checkAuth.isOk()) {
+            return checkAuth;
+          }
+        }
+
+        return Status.OK;
+      }
+    };
+  }
 }

binder/src/test/java/io/grpc/binder/SecurityPoliciesTest.java

@@ -171,4 +171,24 @@ public void testHasSignature_failsIfUidUnknown() throws Exception {
     assertThat(policy.checkAuthorization(OTHER_UID_UNKNOWN).getCode())
       .isEqualTo(Status.UNAUTHENTICATED.getCode());
   }
+
+  @Test
+  public void testAllOf_succeedsIfAllSecurityPoliciesAllowed() throws Exception {
+    policy = SecurityPolicies.allOf(SecurityPolicies.internalOnly());
+
+    assertThat(policy.checkAuthorization(MY_UID).getCode()).isEqualTo(Status.OK.getCode());
+  }
+
+  @Test
+  public void testAllOf_failsIfOneSecurityPoliciesNotAllowed() throws Exception {
+    policy =
+        SecurityPolicies.allOf(
+            SecurityPolicies.internalOnly(),
+            SecurityPolicies.permissionDenied("Not allowed SecurityPolicy"));
+
+    assertThat(policy.checkAuthorization(MY_UID).getCode())
+        .isEqualTo(Status.PERMISSION_DENIED.getCode());
+    assertThat(policy.checkAuthorization(MY_UID).getDescription())
+        .contains("Not allowed SecurityPolicy");
+  }
 }