安卓代码能不能实现关闭SElinux权限

2025-03-26 09:53:09
推荐回答(1个)
回答1:

不可以
1.3 方法1:adb在线修改

关闭 seLinux:

打开seLinux:

Enforcing:seLinux已经打开;
Permissive:seLinux已经关闭;

1.4 方法2: 从kernel中彻底关闭 (用于开机初始化时的seLinux权限问题,要重编bootimage)

修改LINUX/android/kernel/arch/arm64/configs/XXXdefconfig文件(找相应config文件)
去掉CONFIG_SECURITY_SELINUX=y 的配置项

2. 在sepolicy中添加相应权限

2.1 修改依据:
log 信息:
avc: denied { 操作权限 } for pid=7201 comm=“进程名” scontext=u:r:源类型:s0 tcontext=u:r:目标类型:s0 tclass=访问类别 permissive=0

2.2 修改步骤:
找相应的“源类型.te ”文件

有两个位置可能存在相应的te文件:

位置一:LINUX/android/external/sepolicy
位置二:LINUX/android/device/qcom/sepolicy/common

2.3 按如下格式在该文件中添加:

allow 源类型 目标类型:访问类别 {权限};

2.4 举例
Kernel Log:
avc: denied { execheap } for pid=7201 comm="com.baidu.input" scontext=u:r:untrusted_app:s0tcontext=u:r:untrusted_app:s0tclass=processpermissive=0

修改:
在LINUX/android/external/sepolicy/untrusted_app.te 中添加:

[java] view plain copy
allow untrusted_app untrusted_app:process { execheap };

备注:
在这个例子中,由于源类型和目标类型都是untreated_app, 所以也可以写成:

[java] view plain copy
allow untrusted_app self:process { execheap };

3. 添加权限后的neverallowed冲突

3.1 编译报错:
libsepol.check_assertion_helper: neverallow on line xxx ofexternal/sepolicy/domain.te ……

3.2 原因:
新添加的sepolicy项目违反了domain.te 中规定的的总策略原则。所以该条权限策略不能添加,如果强行添加的话有CTS测试失败的风险。

3.3 解决方法:
1.从运行log中找到要访问的目标名称,一般是name字段后的名称
avc: denied { read write } for pid=303 comm="mediaserver"name="tfa9890"dev="tmpfs" ino=3880 scontext=u:r:mediaserver:s0tcontext=u:object_r:device:s0tclass=chr_file permissive=0

2.找到相应的*_contexts文件。

一般有file_contexts, genfs_contexts, property_contexts, service_contexts 等文件

3.在contexts文件中指定要访问的目标为一个“源类型 ”有权限访问的“目标类型”
如:在file_contexts中添加: /dev/tfa9890 u:object_r:audio_device:s0

3.4 举例
添加权限:
在mediaserver.te中添加allow mediaserver device:chr_file { read write open};

编译报错:
libsepol.check_assertion_helper: neverallow on line 258 ofexternal/sepolicy/domain.te (or line 5252 of policy.conf) violated byallow mediaserver device:chr_file { read write open};

违反了domain.te 258的:
neverallow {domain –unconfineddomain –ueventd } device:chr_file { open read write}

运行Log:
avc: denied { read write } for pid=303 comm="mediaserver"name="tfa9890" dev="tmpfs" ino=3880 scontext=u:r:mediaserver:s0 tcontext=u:object_r:device:s0tclass=chr_file permissive=0

修改步骤:

1.目标名称是: tfa9890, 其在系统中的路径是: /dev/tfa9890, 是audio相关的设备文件
2.源类型是mediaserver, 在mediaserver.te 文件中发现其具有 audio_device 目标类型的权限
3.所以在file_contexts 中添加 “/dev/tfa9890 u:object_r:audio_device:s0” 可以解决问题

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