Purple Pi OH Android11 ROOT 方法

前言

为了让应用程序可以直接调用su执行系统命令和获取root权限，本文基于Purple Pi OH主板的Android SDK，介绍如果修改和编译一个root版本的Android11系统,以下为sdk源码修改方法。

Purple Pi OH作为一款兼容树莓派的开源主板，采用瑞芯微RK3566 (Cortex-A55) 四核64位超强CPU,主频最高达1.8 GHz,算力高达1Tops，支持INT8/INT16，支持TensorFlow/MXNet/PyTorch/Caffe框架，多路视频输出和输入，支持4K、H.265/H.264视频解码，接口丰富。

玩法丰富，支持OpenHarmony、Ubuntu、Debian、Android等多种系统,提供丰富开源资料。

产品规格书：Purple Pi OH 产品手册

关闭selinux

device/rockchip/common/BoardConfig.mk

diff --git a/device/rockchip/common/BoardConfig.mk b/device/rockchip/common/BoardConfig.mk
index e03c54f6a0..4fc6dc9868 100755
--- a/device/rockchip/common/BoardConfig.mk
+++ b/device/rockchip/common/BoardConfig.mk
@@ -59,7 +59,7 @@ BOARD_BOOT_HEADER_VERSION ?= 2
 BOARD_MKBOOTIMG_ARGS :=
 BOARD_PREBUILT_DTBOIMAGE ?= $(TARGET_DEVICE_DIR)/dtbo.img
 BOARD_ROCKCHIP_VIRTUAL_AB_ENABLE ?= false
-BOARD_SELINUX_ENFORCING ?= true
+BOARD_SELINUX_ENFORCING ?= false

 # Use the non-open-source parts, if they're present

注释用户组权限检测system/extras/su/su.cpp

diff --git a/system/extras/su/su.cpp b/system/extras/su/su.cpp
index 1a1ab6bf40..af3d2a68c7 100644
--- a/system/extras/su/su.cpp
+++ b/system/extras/su/su.cpp
@@ -80,8 +80,8 @@ void extract_uidgids(const char* uidgids, uid_t* uid, gid_t* gid, gid_t* gids, i
 }

 int main(int argc, char** argv) {
- uid_t current_uid = getuid();
- if (current_uid != AID_ROOT && current_uid != AID_SHELL) error(1, 0, "not allowed");
+ //uid_t current_uid = getuid();
+ //if (current_uid != AID_ROOT && current_uid != AID_SHELL) error(1, 0, "not allowed");

     // Handle -h and --help.
     ++argv;

给su文件默认授予root权限

system/core/libcutils/fs_config.cpp

diff --git a/system/core/libcutils/fs_config.cpp b/system/core/libcutils/fs_config.cpp
index 5805a4d19b..92e93e76ff 100644
--- a/system/core/libcutils/fs_config.cpp
+++ b/system/core/libcutils/fs_config.cpp
@@ -188,7 +188,7 @@ static const struct fs_path_config android_files[] = {
     // the following two files are INTENTIONALLY set-uid, but they
     // are NOT included on user builds.
     { 06755, AID_ROOT, AID_ROOT, 0, "system/xbin/procmem" },
- { 04750, AID_ROOT, AID_SHELL, 0, "system/xbin/su" },
+ { 06755, AID_ROOT, AID_SHELL, 0, "system/xbin/su" },

     // the following files have enhanced capabilities and ARE included
     // in user builds.

frameworks/base/core/jni/com_android_internal_os_Zygote.cpp
 

diff --git a/frameworks/base/core/jni/com_android_internal_os_Zygote.cpp b/frameworks/base/core/jni/com_android_internal_os_Zygote.cpp
index 9eede83e21..d161e6fad3 100644
--- a/frameworks/base/core/jni/com_android_internal_os_Zygote.cpp
+++ b/frameworks/base/core/jni/com_android_internal_os_Zygote.cpp
@@ -656,7 +656,7 @@ static void EnableKeepCapabilities(fail_fn_t fail_fn) {
 }

 static void DropCapabilitiesBoundingSet(fail_fn_t fail_fn) {
- for (int i = 0; prctl(PR_CAPBSET_READ, i, 0, 0, 0) >= 0; i++) {;
+/* for (int i = 0; prctl(PR_CAPBSET_READ, i, 0, 0, 0) >= 0; i++) {;
     if (prctl(PR_CAPBSET_DROP, i, 0, 0, 0) == -1) {
       if (errno == EINVAL) {
         ALOGE("prctl(PR_CAPBSET_DROP) failed with EINVAL. Please verify "
@@ -665,7 +665,7 @@ static void DropCapabilitiesBoundingSet(fail_fn_t fail_fn) {
         fail_fn(CREATE_ERROR("prctl(PR_CAPBSET_DROP, %d) failed: %s", i, strerror(errno)));
       }
     }
- }
+ }*/
 }

kernel/security/commoncap.c

diff --git a/kernel/security/commoncap.c b/kernel/security/commoncap.c
index 876cfe01d9..ce87b1b780 100644
--- a/kernel/security/commoncap.c
+++ b/kernel/security/commoncap.c
@@ -1166,12 +1166,12 @@ int cap_task_setnice(struct task_struct *p, int nice)
 static int cap_prctl_drop(unsigned long cap)
 {
        struct cred *new;
-
+/*
        if (!ns_capable(current_user_ns(), CAP_SETPCAP))
                return -EPERM;
        if (!cap_valid(cap))
                return -EINVAL;
-
+*/
        new = prepare_creds();
        if (!new)
                return -ENOMEM;

编译镜像

修改后需要重新编译内核和AOSP，Android编译需要选择rk3566_r-userdebug版本

source build/envsetup.sh
lunch rk3566_r-userdebug

检测验证root是否成功

可在应用程序中调用 /system/xbin/su来测试系统是否root成功

public static void RootCommand() {
        Process process = null;
        try {
            process = Runtime.getRuntime().exec("/system/xbin/su");
            process.waitFor();
        } catch (IOException | InterruptedException e) {
            e.printStackTrace();
        } finally {
            if (process != null) {
                process.destroy();
            }
        }
}

root的系统可正常执行，而非root的系统会提示没有权限

java.io.IOException: Cannot run program "/system/xbin/su": error=13, Permission denied