Descubrir e identificar hosts IKE (Servidores VPN IPsec)
ike-scan utiliza las herramientas estándar GNU autoconf y automake, por lo que la instalación sigue el proceso normal:
git clone https://github.com/royhills/ike-scan.git para obtener el código fuente del proyectocd ike-scan para entrar al directorio fuenteautoreconf --install para generar un archivo ./configure funcional./configure o ./configure --with-openssl para usar las bibliotecas OpenSSLmake para compilar el proyectomake check para verificar que todo funcione correctamentemake install para instalar (necesitará permisos de root o sudo para esta parte)Si planea realizar descifrado de claves precompartidas, debe configurar ike-scan para usar las funciones hash de OpenSSL en lugar de las incorporadas, porque las de OpenSSL suelen ser más rápidas. Para ello, asegúrese de tener los archivos de inclusión y las bibliotecas de OpenSSL instalados, y ejecute configure como ./configure --with-openssl. El uso de OpenSSL o no no afectará la funcionalidad de ike-scan, solo la velocidad del descifrado de claves precompartidas con psk-crack.
Algunos sistemas operativos instalan los encabezados y bibliotecas de OpenSSL de forma predeterminada; otros requieren que instale un paquete opcional, por ejemplo, en Debian Linux debe instalar el paquete libssl-dev. Alternativamente, puede descargar e instalar el tarball de OpenSSL desde http://www.openssl.org/
Debería compilarse en la mayoría de los sistemas operativos tipo Unix modernos. Funciona en Windows con Cygwin y puede utilizarse como ejecutable independiente de Windows cuando cygwin1.dll está presente.
Si está utilizando el paquete binario de Windows-32, lea también el archivo README-WIN32 que detalla las diferencias al ejecutarse en la plataforma Windows.
Se sabe que el programa se compila y ejecuta en Linux, FreeBSD, OpenBSD, NetBSD, Win32/Cygwin, Solaris, MacOS X, HP Tru64, HP-UX y SCO OpenServer. Para más detalles, consulte la sección "PLATAFORMAS SOPORTADAS" más abajo.
ike-scan descubre hosts IKE y también puede identificarlos utilizando el patrón de retroceso de retransmisión.
ike-scan puede realizar las siguientes funciones:
El concepto de identificación por retroceso de retransmisión se discute con más detalle en el documento sobre identificación por retroceso UDP, que debería estar incluido en el kit de ike-scan como Documento sobre Identificación por Retroceso UDP.
El programa envía solicitudes IKE de fase-1 (Modo Principal o Modo Agresivo) a los hosts especificados y muestra cualquier respuesta recibida. Maneja reintentos y retransmisiones con retroceso para soportar la pérdida de paquetes. También limita la cantidad de ancho de banda utilizado por los paquetes IKE salientes.
IKE es el protocolo de Intercambio de Claves de Internet, que es el mecanismo de intercambio de claves y autenticación utilizado por IPsec. Casi todos los sistemas VPN modernos implementan IPsec, y la gran mayoría de las VPN IPsec utilizan IKE para el intercambio de claves. El Modo Principal es uno de los modos definidos para la fase-1 del intercambio IKE (el otro modo definido es el modo agresivo). La sección 5 del RFC 2409 especifica que el modo principal debe implementarse, por lo tanto, se espera que todas las implementaciones IKE soporten el modo principal. Muchas también soportan el Modo Agresivo.
Para ver la información de uso actual, ejecute el binario de ike-scan de la siguiente manera:ike-scan -h
Additional documentation is provided on the NTA Monitor Wiki
To report bugs or suggest new features, please create a GitHub issue.
The hosts to scan can be specified on the command line or read from an input file using the --file=<fn> option. The program can cope with large numbers of hosts limited only by the amount of memory needed to store the list of host_entry structures. Each host_entry structure requires 45 bytes on a 32-bit system, so a class B network (65534 hosts) would require about 2.8 MB for the list. The hosts can be specified as either IP addresses or hostnames, however the program will store all hosts internally as IP addresses and will only display IP addresses in the output (ike-scan calls gethostbyname(3) to determine the IP address of each host, but this can be disabled with the --nodns option).
The program limits the rate at which it sends IKE packets to ensure that it does not overload the network connection. By default it uses an outbound data rate of 56000 bits per second. This can be changed with the --bandwidth option.
If you want to send packets at a specific rate, you can use the --interval option.
ike-scan generates unique IKE cookies for each host, and it uses these cookies to determine which host the response packets belong to. Note that it does not rely on the source IP address of the response packets because it is possible for a response packet to be sent from a different IP address than it was originally sent to. See the PROGRAM OUTPUT section for an example of this.
The cookies are generated by taking the first 64 bits of an MD5 hash of the current time in seconds and microseconds as returned by gettimeofday(), the unique host number, and the host IP address. This ensures that the cookies are unique with a reasonable degree of certainty.
If --verbose is in effect, any packets that are received with cookies that do not match will result in a message like:
Ignoring 84 bytes from 172.16.2.2 with unknown cookie 195c837e5a39f657
Si --verbose no está activo, dichos paquetes se ignoran silenciosamente.
Este tipo de discrepancia de cookies puede deberse a:
Los paquetes enviados en modo principal contienen un encabezado ISAKMP y una carga útil SA. La carga útil SA contiene una única propuesta, y la propuesta puede contener un número variable de transformaciones, como se detalla a continuación.
Por defecto, la propuesta SA contiene 8 transformaciones. Estas 8 transformaciones representan todas las combinaciones posibles de:
A continuación se muestra un ejemplo de salida de tcpdump del paquete de modo principal enviado por ike-scan utilizando el conjunto de transformaciones predeterminado. Esto muestra las 8 transformaciones y también el orden en que se envían:
16:57:16.024536 192.168.124.8.500 > 172.16.2.2.500: [udp sum ok]isakmp 1.0 msgid 00000000: phase 1 I ident:
(sa: doi=ipsec situation=identity
(p: #1 protoid=isakmp transform=8
(t: #1 id=ike (type=enc value=3des)(type=hash value=sha1)(type=auth value=preshared)(type=group desc value=modp1024)(type=lifetype value=sec)(type=lifeduration len=4 value=00007080))
(t: #2 id=ike (type=enc value=3des)(type=hash value=md5)(type=auth value=preshared)(type=group desc value=modp1024)(type=lifetype value=sec)(type=lifeduration len=4 value=00007080))
(t: #3 id=ike (type=enc value=1des)(type=hash value=sha1)(type=auth value=preshared)(type=group desc value=modp1024)(type=lifetype value=sec)(type=lifeduration len=4 value=00007080))
(t: #4 id=ike (type=enc value=1des)(type=hash value=md5)(type=auth value=preshared)(type=group desc value=modp1024)(type=lifetype value=sec)(type=lifeduration len=4 value=00007080))
(t: #5 id=ike (type=enc value=3des)(type=hash value=sha1)(type=auth value=preshared)(type=group desc value=modp768)(type=lifetype value=sec)(type=lifeduration len=4 value=00007080))
(t: #6 id=ike (type=enc value=3des)(type=hash value=md5)(type=auth value=preshared)(type=group desc value=modp768)(type=lifetype value=sec)(type=lifeduration len=4 value=00007080))
(t: #7 id=ike (type=enc value=1des)(type=hash value=sha1)(type=auth value=preshared)(type=group desc value=modp768)(type=lifetype value=sec)(type=lifeduration len=4 value=00007080))
(t: #8 id=ike (type=enc value=1des)(type=hash value=md5)(type=auth value=preshared)(type=group desc value=modp768)(type=lifetype value=sec)(type=lifeduration len=4 value=00007080)))) (DF) (ttl 64, id 0, len 364)```
Este conjunto de transformaciones predeterminado está diseñado para ser aceptable para la mayoría de las implementaciones de IKE; la mayoría aceptará al menos una de las transformaciones ofrecidas. Sin embargo, a veces es necesario utilizar un método de autenticación diferente (la clave precompartida es la más común, pero no siempre es compatible), y ocasionalmente es necesario especificar un cifrado diferente, como AES de 256 bits. Más raramente puede ser necesario cambiar el tiempo de vida. Finalmente, algunas implementaciones requieren que el cliente envíe una cadena "Vendor ID" específica antes de responder. Esto se puede especificar con la opción --vendor.
El conjunto de transformaciones predeterminado da como resultado una longitud de datos del paquete de 336 bytes que, al agregar los encabezados IP y UDP, proporciona un tamaño total del paquete de 364 bytes.
Es posible especificar el Método de Autenticación con --auth (el valor predeterminado es 1: clave precompartida) y el tiempo de vida de IKE en segundos con --lifetime (el valor predeterminado es 28800 segundos u 8 horas, según lo recomendado por RFC 2407). Si especifica --lifetime como 0, no se incluye ningún atributo de tiempo de vida en las cargas útiles de transformación. Si está especificando transformaciones personalizadas, puede usar esta opción más de una vez para producir cargas útiles de transformación con diferentes tiempos de vida. Cada opción --trans utilizará el valor de tiempo de vida especificado anteriormente.
Es posible especificar un conjunto de transformaciones personalizado con --trans=e[/l],h,a,g donde "e" es el Algoritmo de Cifrado, "l" es la longitud de clave para cifrados de longitud variable, "h" es el Algoritmo Hash, "a" es el Método de Autenticación y "g" es el Grupo DH. Estos se especifican como valores numéricos; consulte el Apéndice A de RFC 2409 para obtener detalles sobre qué valores utilizar.
Por ejemplo: --trans=5,2,1,2 especifica:Enc=5 (3DES-CBC), Hash=2 (SHA1), Auth=1 (shared key), DH Group=2 (modp 1024)
and --trans=7/256,1,1,5 specifies:
Enc=7 (AES), Keylen=256 bits, Hash=MD5, Auth=shared key, DH Group=5 (modp 1536)
Puede usar la opción --trans más de una vez para enviar un número arbitrario de transformaciones personalizadas en la propuesta.
Especificar un conjunto de transformaciones personalizadas anula cualquier método de autenticación especificado con --auth. Sin embargo, todavía usa el valor de vida útil especificado en la última opción --lifetime.
Un ejemplo de un conjunto complejo de transformaciones personalizadas es:--trans=5,2,1,2 --lifetime=0 --trans=7/256,1,3,5 --lifetime=600 --trans=7/128,1,3,5
This would specify the following three transforms:
If a custom transform set is specified, the packet length will differ from the default. Fewer than 8 transforms will make it smaller, and more than 8 transforms will make it larger. If the packet size exceeds the MTU, then it will be fragmented. You may need to increase the --interval setting for large packets to avoid overloading your network connection. Some VPN servers may ignore very long packets.
A custom transform can be useful in the following situations:
The default mode used is Main Mode. However, it is possible to specify Aggressive Mode with the --aggressive option. When this is done, three additional payloads will be included: Key Exchange, Nonce and ID. This will increase the packet size, and you may need to increase --interval to ensure that ike-scan doesn't try to use too much bandwidth as a result. If you use Aggressive Mode, you can also use the following options:
--id Set identification value.--idtype Set identification type (Default 3 (ID_USER_FQDN)).--dhgroup Specify Diffie-Hellman group (Default 2 - MODP 1024).If you use Aggressive Mode, then you can only use one Diffie Hellman group in the transform set. If you specify custom transforms with the --trans option, you should ensure that they all use the same group, and that this group matches the DH group specified with the --dhgroup option, or the default of 2 if --dhgroup is not specified.
IKE hosts may respond in one of two ways:
An example tcpdump output for a "handshake" response is:
16:57:48.068698 172.16.2.2.500 > 192.168.124.8.500: [udp sum ok]isakmp 1.0 msgid 00000000: phase 1 R ident:
(sa: doi=ipsec situation=identity
(p: #1 protoid=isakmp transform=1
(t: #1 id=ike (type=enc value=3des)(type=hash value=sha1)(type=auth value=preshared)(type=group desc value=modp1024)(type=lifetype value=sec)(type=lifeduration len=4 value=00007080)))) (ttl 126, id 37891, len 112)
This shows that the IKE host has responded with an ISAKMP header and an SA payload containing a single proposal. This proposal contains a single transform representing the transform chosen from the proposal sent by ike-scan.
An example tcpdump output for a "notify" response is:
17:12:55.038554 192.168.89.22.500 > 192.168.37.1.500: [udp sum ok]isakmp 1.0 msgid 00000000: phase 1 R inf:
(n: doi=0 proto=1 type=NO-PROPOSAL-CHOSEN) (ttl 52, id 39577, len 68)
This shows that the IKE host has responded with an ISAKMP header and a notify payload. The notify payload is an informational message with the type "NO-PROPOSAL-CHOSEN".
ike-scan does not respond to any of the IKE responses it receives, so the IKE main mode handshake will never complete. Some IKE implementations do not log handshakes that don't complete; these implementations will not log the scanning and therefore the owners of these systems will not be aware of the scanning. It is possible to use ike-scan to determine if a given implementation will log these scanning attempts if you have access to the system logs.
For those hosts that respond, ike-scan records the times of the received IKE responses. The backoff between IKE responses varies between different IKE implementations and can therefore be used as a fingerprint. The --showbackoff option is used to display the backoff times for each host which responded. Note that using the --showbackoff option will cause ike-scan to wait for 60 seconds after the last received packet to ensure that it has seen all of the responses. This 60 second wait can be altered by specifying a different value in seconds to the --showbackoff option.
When all of the packets have been received, the backoff table is displayed, and the program attempts to match the backoff pattern against the known backoff patterns contained in the text file ike-backoff-patterns. It is possible to add new patterns to this file.
Note that only hosts which respond with a handshake can be fingerprinted by backoff timings; hosts which respond with a notify message cannot. This is because notify messages are only ever sent once and are not subject to retransmission with backoff.
If you discover IKE hosts with backoff patterns which are not recognised by ike-scan, then you are encouraged to submit the pattern and details of the IKE implementation to me so I can incorporate it into future versions of ike-scan. You can do this by opening an issue, or a pull request on github.
Note that any packet loss will prevent the backoff fingerprinting from working because the program needs to see all of the responses.
ike-scan can also be used to fingerprint IKE hosts in other ways. For example:
--sport=0) whereas others (e.g. Windows 2000) only respond to IKE requests from source port 500 (actually, Windows 2000 responds to requests from any port, but always sends the responses back to port 500 which amounts to the same thing).--trans. Note however, that the user can usually change the transform set, so this cannot be relied upon by itself.The program output consists of two sections:
--showbackoff is specified).The IKE host detection section contains one line for each host that responds. The response can either be a successful handshake or an informational message. Only the first packet returned by any given host is displayed in this section.
Some examples of the IKE host detection section are:
10.0.1.98 IKE Handshake returned (1 transforms)
10.0.1.22 Notify message 14 (NO-PROPOSAL-CHOSEN)
10.0.1.189 (10.0.1.130) Notify message 9101 (No common authentication method with Firewall.)
In the above example output, host 10.0.1.98 has returned an IKE handshake, 10.0.1.22 has returned notify message 14 (decimal) which corresponds to the RFC-defined error message "NO-PROPOSAL-CHOSEN" (see RFC 2408 section 3.14.1), and 10.0.1.189 has returned a non-standard notify message 9101 but the response has come from the IP address 10.0.1.130 rather than the address which the request was sent to (presumably this is a multi-homed system). Notify message 9101 is not defined by RFC 2408, but it is known to be a Checkpoint proprietary notify code (therefore the system is probably Firewall-1) and the program displays the text included in the notify message.
Some examples of the IKE backoff pattern section are:
IP Address No. Recv time Delta Time
172.16.2.2 1 1042549209.247980 0.000000
172.16.2.2 2 1042549211.239254 1.991274
172.16.2.2 3 1042549213.241935 2.002681
172.16.2.2 4 1042549215.244731 2.002796
172.16.2.2 5 1042549217.247512 2.002781
172.16.2.2 6 1042549219.250254 2.002742
172.16.2.2 7 1042549221.253044 2.002790
172.16.2.2 8 1042549225.258551 4.005507
172.16.2.2 9 1042549229.264074 4.005523
172.16.2.2 10 1042549233.269605 4.005531
172.16.2.2 11 1042549237.275145 4.005540
172.16.2.2 12 1042549241.280654 4.005509
172.16.2.2 Implementation guess: Firewall-1 4.1/NG
IP Address No. Recv time Delta Time
10.0.1.98 1 1042549209.426540 0.000000
10.0.1.98 2 1042549224.425435 14.998895
10.0.1.98 3 1042549239.422251 14.996816
10.0.1.98 Implementation guess: Cisco IOS / PIX
Here, host 172.16.2.2 returned a total of 12 packets and the pattern matched "Firewall-1 4.1/NG", and host 10.0.1.98 returned 3 packets matching the pattern for "Cisco IOS / PIX". The recv time column shows the absolute time when the packet was received in seconds and microseconds since the epoch; delta time shows the elapsed time between packets in seconds and microseconds.
The below example will run IKE detection against the single host 172.16.2.2. No backoff fingerprinting will be done, and all options (timeouts, retrys, transform set Etc) will be the default.
ike-scan 172.16.2.2This will read the target hosts from the file "hostlist.txt".
ike-scan --file=hostlist.txtThis reads the hosts from stdin and performs both IKE detection and backoff fingerprinting. The backoff wait is specified as 20 seconds.
cat hostlist.txt | ike-scan --file=- --showbackoff=20This will run ike-scan against all hosts in the network specified by 172.16.0.0/16 (including network and broadcast addresses). In this case, this will result in a total of 65536 hosts being scanned - from 172.16.0.0 to 172.16.255.255 inclusive.
ike-scan 172.16.0.0/16This uses the range notation to scan a total of 65536 hosts from 172.16.0.0 to 172.16.255.255 inclusive.
ike-scan 172.16.0.0-172.16.255.255ike-scan has been built and tested on the following platforms:
I've also had reports that it builds OK on the following systems:
It should work, or be capable of working, on any Unix-like system which has a 64-bit integer type, supports sockets and has the system calls malloc, gethostbyname, gettimeofday, inet_ntoa, memset, select, socket, and strerror.
If you port ike-scan to a system not listed above, please let me know the details of the changes required so I can add them to future releases.
For an in-depth coverage of IPsec including IKE, I recommend the book "IPsec The New Security Standard for the Internet, Intranets and Virtual Private Networks" by Doraswamy and Harkins, ISBN 0-13-011898-2. I used this book together with the RFCs to learn about IKE.
The following RFCs relate to IKE:
All of these RFCs can be obtained from: http://www.ietf.org/rfc
The best way to contact me is via the ike-scan repository on github.
I would like to hear from you if you have any of the following:
If you need to contact me offline, please email me at [email protected]