Fake device properties for MTK trustkernel TEE

MTK doesn't want their devices to boot non-Google GSIs from the **same**
month with the **same** version.

Co-authored-by: Pierre-Hugues Husson <phh@phh.me>

init/Android.bp

@@ -7,6 +7,7 @@ cc_binary {
         
         // SoC-specific quirks
         "quirks/soc/mtk_ril.cpp",
+        "quirks/soc/mtk_trustkernel.cpp",
         "quirks/soc/caf_audio.cpp",
         
         // Device-specific quirks

init/quirks/soc/mtk_trustkernel.cpp

@@ -0,0 +1,73 @@
+#include "../../quirks.h"
+
+#include <android-base/properties.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include <cstdlib>
+#include <filesystem>
+#include <optional>
+#include <string>
+#include <utility>
+
+using namespace std;
+
+#define AVB_PROP_OS_VERSION "com.android.build.boot.os_version"
+#define AVB_PROP_SPL "com.android.build.boot.security_patch"
+
+optional<pair<string, string>> try_get_spl() {
+    string boot_part = "/dev/block/by-name/boot" + android::base::GetProperty("ro.boot.slot_suffix", "");
+
+    // Read from AVB footer, https://github.com/TrebleDroid/device_phh_treble/blob/android-13.0/fixSPL/getSPL.c
+    // First read into memory
+    int fd = open(boot_part.c_str(), O_RDONLY);
+    off_t size = lseek(fd, 0, SEEK_END);
+    lseek(fd, 0, SEEK_SET);
+    char *buf = (char *) malloc(size);
+    read(fd, buf, size);
+
+    // Search for AVB footer property directly in the binary
+    char* p = (char *) memmem(buf, size, AVB_PROP_OS_VERSION, sizeof(AVB_PROP_OS_VERSION));
+    if (p == nullptr)
+        return nullopt;
+
+    p += sizeof(AVB_PROP_OS_VERSION);
+    string os_version(p);
+
+    p = (char *) memmem(buf, size, AVB_PROP_SPL, sizeof(AVB_PROP_SPL));
+    if (p == nullptr)
+        return nullopt;
+
+    p += sizeof(AVB_PROP_SPL);
+    string spl(p);
+
+    return make_pair(os_version, spl);
+}
+
+class MtkTkQuirk : DeviceQuirk {
+public:
+    bool ShouldRun() {
+        return filesystem::exists("/proc/tkcore/tkcore_log");
+    }
+
+    void Run() {
+        android::base::SetProperty("debug.phh.props.ice.trustkernel", "keymaster");
+        android::base::SetProperty("debug.phh.props.teed", "keymaster");
+        android::base::SetProperty("ro.keymaster.brn", "Android");
+        android::base::SetProperty("ro.keymaster.mod", "AOSP on ARM64");
+
+        auto res = try_get_spl();
+
+        if (res) {
+            android::base::SetProperty("ro.keymaster.xxx.release", res->first);
+            android::base::SetProperty("ro.keymaster.xxx.security_patch", res->second);
+        }
+
+        android::base::SetProperty("ctl.restart", "teed");
+    }
+};
+
+LOAD_QUIRK(MtkTkQuirk)

sepolicy/private/keymaster.te

@@ -0,0 +1,7 @@
+# Access to fake keymaster SPL/Android version props -- from TrebleDroid
+get_prop(hal_keymaster, default_prop);
+get_prop(tee, default_prop);
+
+get_prop(hal_keymaster, system_prop);
+
+get_prop(hal_gatekeeper, system_prop);