add extended sysprop overrides

libc/bionic/system_property_api.cpp

@@ -135,3 +135,8 @@ int __system_properties_zygote_reload(void) {
   CHECK(getpid() == gettid());
   return system_properties.EnableOverrides() ? 0 : -1;
 }
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_properties_enable_extended_override(void) {
+  return system_properties.EnableExtendedOverrides() ? 0 : -1;
+}

libc/include/sys/system_properties.h

@@ -240,6 +240,8 @@ int __system_property_update(prop_info* _Nonnull __pi, const char* _Nonnull __va
  * Available since API level 35.
  */
 int __system_properties_zygote_reload(void) __INTRODUCED_IN(35);
+
+int __system_properties_enable_extended_override(void);
 #endif
 
 /**

libc/libc.map.txt

@@ -1612,6 +1612,7 @@ LIBC_V { # introduced=35
     tzfree;
     wcsrtombs_l;
     __system_properties_zygote_reload; # apex
+    __system_properties_enable_extended_override; # apex
 } LIBC_U;
 
 LIBC_36 { # introduced=36

libc/system_properties/include/system_properties/system_properties.h

@@ -53,6 +53,7 @@ class SystemProperties {
 
   bool Init(const char* filename);
   bool EnableOverrides();
+  bool EnableExtendedOverrides();
   bool AreaInit(const char* filename, bool* fsetxattr_failed);
   bool AreaInit(const char* filename, bool* fsetxattr_failed, bool load_default_path);
   uint32_t AreaSerial();
@@ -91,6 +92,7 @@ class SystemProperties {
 
   bool initialized_;
   bool use_appcompat_override_;
+  bool use_extended_override_;
   PropertiesFilename properties_filename_;
   PropertiesFilename appcompat_filename_;
 };

libc/system_properties/system_properties.cpp

@@ -53,6 +53,7 @@
 #define SERIAL_VALUE_LEN(serial) ((serial) >> 24)
 #define APPCOMPAT_PREFIX "ro.appcompat_override."
 #define APPCOMPAT_OVERRIDE_ENV_VAR "BIONIC_APPCOMPAT_OVERRIDE"
+#define EXTENDED_OVERRIDE_ENV_VAR "GOS_HIDE_CARRIER_INFO_PROP_OVERRIDE"
 
 static bool is_dir(const char* pathname) {
   struct stat info;
@@ -81,6 +82,11 @@ bool SystemProperties::Init(const char* filename) {
     use_appcompat_override_ = true;
   }
 
+  if (getenv(EXTENDED_OVERRIDE_ENV_VAR) != nullptr) {
+    use_appcompat_override_ = true;
+    use_extended_override_ = true;
+  }
+
   initialized_ = true;
   return true;
 }
@@ -151,6 +157,33 @@ bool SystemProperties::EnableOverrides() {
   return true;
 }
 
+bool SystemProperties::EnableExtendedOverrides() {
+  CHECK(initialized_);
+  use_appcompat_override_ = true;
+  use_extended_override_ = true;
+  putenv(const_cast<char*>(APPCOMPAT_OVERRIDE_ENV_VAR "=1"));
+  putenv(const_cast<char*>(EXTENDED_OVERRIDE_ENV_VAR "=1"));
+  return true;
+}
+
+static const char* const kHideCarrierInfoDeniedProps[] = {
+    "gsm.sim.operator.alpha",
+    "gsm.sim.operator.numeric",
+    "gsm.sim.operator.iso-country",
+    "gsm.operator.alpha",
+    "gsm.operator.numeric",
+    "gsm.operator.iso-country",
+    "gsm.operator.isroaming",
+    "gsm.sim.state",
+};
+
+static bool is_hide_carrier_info_denied(const char* name) {
+  for (const char* denied : kHideCarrierInfoDeniedProps) {
+    if (strcmp(name, denied) == 0) return true;
+  }
+  return false;
+}
+
 uint32_t SystemProperties::AreaSerial() {
   if (!initialized_) {
     return -1;
@@ -170,6 +203,10 @@ const prop_info* SystemProperties::Find(const char* name) {
     return nullptr;
   }
 
+  if (use_extended_override_ && is_hide_carrier_info_denied(name)) {
+    return nullptr;
+  }
+
   // if appcompat override is enabled, we first try finding APPCOMPAT_PREFIXed system
   // property
   if (use_appcompat_override_) {
@@ -428,6 +465,11 @@ int SystemProperties::Add(const char* name, unsigned int namelen, const char* va
       CHECK(getpid() == 1 || getuid() == 0);
       atomic_thread_fence(memory_order_release);
       memcpy(other_pi->value, value, valuelen + 1);
+      // the high byte of serial encodes value length, we need to update it so readers
+      // (that use SERIAL_VALUE_LEN) return the full overridden string.
+      uint32_t old_serial = atomic_load_explicit(&other_pi->serial, memory_order_relaxed);
+      uint32_t new_serial = (valuelen << 24) | (old_serial & 0x00ffffff);
+      atomic_store_explicit(&other_pi->serial, new_serial, memory_order_release);
     }
   }
 

tests/Android.bp

@@ -1322,6 +1322,54 @@ cc_test {
     ],
 }
 
+// minial static binary for just the system properties tests
+cc_test {
+    name: "bionic-sysprop-tests",
+    gtest: false,
+    defaults: [
+        "bionic_tests_defaults",
+        "large_system_property_node_defaults",
+    ],
+    host_supported: false,
+    test_suites: ["general-tests"],
+
+    srcs: [
+        "gtest_globals.cpp",
+        "gtest_main.cpp",
+        "system_properties_test.cpp",
+        "utils.cpp",
+    ],
+
+    include_dirs: [
+        "bionic/libc",
+    ],
+
+    target: {
+        bionic: {
+            whole_static_libs: [
+                "libasync_safe",
+                "libprocinfo",
+                "libsystemproperties",
+            ],
+        },
+    },
+
+    static_libs: [
+        "libm",
+        "libc",
+        "libdl",
+        "liblog",
+        "libbase",
+        "libgtest_isolated",
+    ],
+
+    static_executable: true,
+    stl: "libc++_static",
+    lto: {
+        never: true,
+    },
+}
+
 // -----------------------------------------------------------------------------
 // Tests to run on the host and linked against glibc. Run with:
 //   cd bionic/tests; mm bionic-unit-tests-glibc-run

tests/system_properties_test.cpp

@@ -227,6 +227,71 @@ TEST(properties, __system_property_getprop_appcompat) {
 #endif  // __BIONIC__
 }
 
+TEST(properties, __system_property_add_extended_override) {
+#if defined(__BIONIC__)
+  SystemPropertiesTest system_properties;
+  ASSERT_TRUE(system_properties.valid());
+
+  ASSERT_EQ(0, system_properties.Add("gsm.sim.operator.numeric", 24, "123456", 6));
+  ASSERT_EQ(0, system_properties.Add("ro.other.prop", 13, "value", 5));
+
+  char propvalue[PROP_VALUE_MAX];
+
+  // before enabling: denied prop is readable
+  ASSERT_EQ(6, system_properties.Get("gsm.sim.operator.numeric", propvalue));
+  ASSERT_STREQ(propvalue, "123456");
+  ASSERT_NE(nullptr, system_properties.Find("gsm.sim.operator.numeric"));
+
+  system_properties.EnableExtendedOverrides();
+
+  // after enabling: denied prop hidden from Find and Get
+  ASSERT_EQ(nullptr, system_properties.Find("gsm.sim.operator.numeric"));
+  ASSERT_EQ(0, system_properties.Get("gsm.sim.operator.numeric", propvalue));
+  ASSERT_STREQ(propvalue, "");
+
+  // non-denied prop unaffected
+  ASSERT_EQ(5, system_properties.Get("ro.other.prop", propvalue));
+  ASSERT_STREQ(propvalue, "value");
+#else   // __BIONIC__
+  GTEST_SKIP() << "bionic-only test";
+#endif  // __BIONIC__
+}
+
+TEST(properties, __system_property_update_extended_override_denylist) {
+#if defined(__BIONIC__)
+  SystemPropertiesTest system_properties;
+  ASSERT_TRUE(system_properties.valid());
+
+  ASSERT_EQ(0, system_properties.Add("gsm.sim.operator.numeric", 24, "123456", 6));
+  ASSERT_EQ(0, system_properties.Add("gsm.version.baseband", 20, "v1", 2));
+
+  // capture prop_info* before enabling override (Find returns nullptr afterward for denied props)
+  const prop_info* denied_pi = system_properties.Find("gsm.sim.operator.numeric");
+  ASSERT_NE(nullptr, denied_pi);
+  const prop_info* allowed_pi = system_properties.Find("gsm.version.baseband");
+  ASSERT_NE(nullptr, allowed_pi);
+
+  system_properties.EnableExtendedOverrides();
+
+  // update underlying values (as init would)
+  system_properties.Update(const_cast<prop_info*>(denied_pi), "654321", 6);
+  system_properties.Update(const_cast<prop_info*>(allowed_pi), "v2", 2);
+
+  char propvalue[PROP_VALUE_MAX];
+
+  // denied prop still hidden after update
+  ASSERT_EQ(nullptr, system_properties.Find("gsm.sim.operator.numeric"));
+  ASSERT_EQ(0, system_properties.Get("gsm.sim.operator.numeric", propvalue));
+  ASSERT_STREQ(propvalue, "");
+
+  // allowed prop updated normally
+  ASSERT_EQ(2, system_properties.Get("gsm.version.baseband", propvalue));
+  ASSERT_STREQ(propvalue, "v2");
+#else   // __BIONIC__
+  GTEST_SKIP() << "bionic-only test";
+#endif  // __BIONIC__
+}
+
 TEST(properties, __system_property_update) {
 #if defined(__BIONIC__)
     SystemPropertiesTest system_properties;