GTS-FailGtsSecurityHostTestCases#testNoExemptionsForSocketsBetweenCoreAndVendorBan
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【GTS-Fail】GtsSecurityHostTestCases#testNoExemptionsForSocketsBetweenCoreAndVendorBan
【问题描述】
Gts-7.0-r4工具报出失败项
GtsSecurityHostTestCases
com.google.android.security.gts.SELinuxHostTest#testNoExemptionsForSocketsBetweenCoreAndVendorBan
<Failure message="junit.framework.AssertionFailedError: Policy exempts domains from ban on socket communications between core and vendor: [hal_audio_default]">
<StackTrace>junit.framework.AssertionFailedError: Policy exempts domains from ban on socket communications between core and vendor: [hal_audio_default]
at junit.framework.Assert.fail(Assert.java:57)
at junit.framework.TestCase.fail(TestCase.java:227)
at com.google.android.security.gts.SELinuxHostTest.testNoExemptionsForSocketsBetweenCoreAndVendorBan(SELinuxHostTest.java:221)
这里有个坑,报问题的时候说上个版本有,其实最终查证0004版本(2.20前)就有这个失败项了,当时芯片厂商也告知是waiver项了。。。
【问题结论】
是waiver项
失败项是由google的auto-patch代码导致,如果第一次遇到可以咨询aml是否waiver。
AuthBlog:秋城https://www.cnblogs.com/houser0323
【分析详细】
测试逻辑总览
使用linux可执行程序:sepolicy-analyze,对机顶盒中的/sys/fs/selinux/policy文件进行解析,要求不能有返回值,命令是:
sepolicy-analyze policy attribute socket_between_core_and_vendor_violators
即:不允许有type(类型)与该attribute(属性)“socket_between_core_and_vendor_violators”有关联,字面意思:core与vendor的违规socket特权
system/sepolicy/tools/sepolicy-analyze/README
ATTRIBUTE (attribute)
sepolicy-analyze out/target/product//root/sepolicy attribute
Displays the types associated with the specified attribute name.
该权限详细限制在以下代码中有论述,Android TREBLE架构解耦计划相关
system/sepolicy/prebuilts/api/26.0/public/domain.te
system/sepolicy/prebuilts/api/27.0/public/domain.te
system/sepolicy/prebuilts/api/28.0/public/domain.te:
system/sepolicy/public/domain.te
# On full TREBLE devices, socket communications between core components and vendor components are
# not permitted.
full_treble_only(`
# Most general rules first, more specific rules below.
# Core domains are not permitted to initiate communications to vendor domain sockets.
# We are not restricting the use of already established sockets because it is fine for a process
# to obtain an already established socket via some public/official/stable API and then exchange
# data with its peer over that socket. The wire format in this scenario is dicatated by the API
# and thus does not break the core-vendor separation.
梳理测试项逻辑
反编译后定位测试项
./com/google/android/security/gts/SELinuxHostTest.java
public void testNoExemptionsForVendorExecutingCore() throws Exception {
if (isFullTrebleDevice()) {
Set<String> types = sepolicyAnalyzeGetTypesAssociatedWithAttribute("vendor_executes_system_violators");//该语句是测试判断,返回测试结果
if (!types.isEmpty()) {
List<String> sortedTypes = new ArrayList(types);
Collections.sort(sortedTypes);
fail("Policy exempts vendor domains from ban on executing files in /system: " + sortedTypes);//此处assert,原因是容器types有东西,东西就是‘[hal_audio_default]’
}
}
}
看一下方法的测试逻辑:sepolicyAnalyzeGetTypesAssociatedWithAttribute()
通过ProcessBuilder开启一个进程,用于执行linux命令:sepolicy-analyze policy attribute socket_between_core_and_vendor_violators
然后获取这个命令的标准输出进行结果判断
private Set<String> sepolicyAnalyzeGetTypesAssociatedWithAttribute(String attribute) throws Exception {
BufferedReader in;
Throwable th;
Throwable th2;
Set<String> types = new HashSet();
//通过ProcessBuilder开启一个进程,用于执行linux命令:sepolicy-analyze policy attribute socket_between_core_and_vendor_violators
ProcessBuilder pb = new ProcessBuilder(new String[]{this.mSepolicyAnalyze.getAbsolutePath(), this.mDevicePolicyFile.getAbsolutePath(), "attribute", attribute});
......
in = new BufferedReader(new InputStreamReader(p.getInputStream()));
th = null;
while (true) {
try {
String type = in.readLine();
if (type != null) {
types.add(type.trim());//获取有效标准输出,写到结果容器中存储
}}}
......
return types;
......
}
现在基本逻辑就清楚了,只要这个命令执行有结果返回就是不被允许的,现在需要分析这个工具‘sepolicy-analyze’是干嘛的?
在Android工程源码中搜索,我们找到了这个host可执行程序的源码
system/sepolicy/tools/sepolicy-analyze/
结合网络资料以及阅读源码和README文档,澄清测试的命令用途:解析policy文件返回与attribute相关联的type值
system/sepolicy/tools/sepolicy-analyze/README
63 ATTRIBUTE (attribute)
64 sepolicy-analyze out/target/product//root/sepolicy attribute
65
66 Displays the types associated with the specified attribute name.
工程中搜索确认
搜过确认一下到底在哪里使得他们关联的,定位到一下te文件
./system/sepolicy/vendor/hal_audio_default.te:1
type hal_audio_default, domain, socket_between_core_and_vendor_violators;
查证git log,我们发现是如下的commit导致的,是google的auto-path
commit 783f5b52195f0168f4c9db29b5a80ac63fb04020
Author: xxxxxx
Date: Mon Feb 17 11:33:16 2020 +0800
auto patch added:CecAudio
diff --git a/vendor/hal_audio_default.te b/vendor/hal_audio_default.te
index 0dc2170..9da0f1b 100644
--- a/vendor/hal_audio_default.te
+++ b/vendor/hal_audio_default.te
@@ -1,4 +1,4 @@
-type hal_audio_default, domain;
+type hal_audio_default, domain, socket_between_core_and_vendor_violators; #此处添加的关联,问题找到了根源
hal_server_domain(hal_audio_default, hal_audio)
到此,问题很大概率可确认为Google-waiver,因为引入问题的代码是Google的。接下来需向芯片厂商或Google沟通确认
由于报问题的乌龙,事实是该问题很久之前已澄清过,所以这一通分析并木有什么卵用。。。。。。
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