netfilter模块问题

ubuntuer

大致需求是要写个内核模块,截获通过内核的包,就是skb结构,然后分析这个结构,然后决定这个包是drop还是accept或者其它处理....
这个是在2.6.18上测试通过的

#include <linux/module.h> #include <linux/kernel.h> #include <linux/netfilter.h> #include <linux/skbuff.h> #include <linux/ip.h> #include <linux/netdevice.h> #include <linux/if_ether.h> #include <linux/if_packet.h> #include <net/tcp.h> #include <linux/netfilter_ipv4.h> static struct nf_hook_ops nfho; unsigned int hook_func (unsigned int hooknum, &nbsp;&nbsp;&nbsp;&nbsp;   struct sk_buff **skb, &nbsp;&nbsp;&nbsp;&nbsp;   const struct net_device *in, &nbsp;&nbsp;&nbsp;&nbsp;   const struct net_device *out, int (*okfn) (struct sk_buff *)) { &nbsp;&nbsp;struct iphdr *iph = (*skb)->nh.iph; &nbsp;&nbsp;uint32_t iphlen = iph->ihl << 2; &nbsp;&nbsp;struct tcphdr *tcph = NULL; &nbsp;&nbsp; &nbsp;&nbsp;if(!(*skb)) return NF_ACCEPT; &nbsp;&nbsp;if(!((*skb)->nh.iph)) return NF_ACCEPT; &nbsp;&nbsp;switch (iph->protocol) &nbsp;&nbsp;&nbsp;&nbsp;{ &nbsp;&nbsp;&nbsp;&nbsp;case IPPROTO_TCP: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;printk ("It's a TCP PACKET\n"); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tcph = (struct tcphdr*)((uint8_t*)iph + iphlen); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IPPROTO_ICMP: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IPPROTO_UDP: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;printk ("It's a UDP PACKET\n"); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;tcph = (struct tcphdr *)((*skb)->nh.iph+((*skb)->nh.iph->ihl)); &nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;printk ("s_port=%d,d_port=%d!",(int)tcph->source,(int)tcph->dest); &nbsp;&nbsp;&nbsp;&nbsp;printk ("urg=%d",(int)tcph->urg); &nbsp;&nbsp;return NF_ACCEPT; } int init_module () { &nbsp;&nbsp;nfho.hook = hook_func; &nbsp;&nbsp;nfho.hooknum = NF_IP_LOCAL_OUT; &nbsp;&nbsp;nfho.pf = PF_INET; &nbsp;&nbsp;nfho.priority = NF_IP_PRI_FIRST; &nbsp;&nbsp;nf_register_hook (&nfho); &nbsp;&nbsp;return 0; } void cleanup_module () { &nbsp;&nbsp;nf_unregister_hook (&nfho); }

现在就是要在2.6.26核上写个大致的程序的...我自己现在是在target上写的,貌似错的比较离谱...
难道不是写target？？？？

dreamice

你写target没错，target就是实现对一个包的策略的。
但你首先要搞明白一个问题：如何让一个target工作？

emmoblin

我问一下：
2.6.18上测试通过了，在2.6.26上就不行了吗？
最多可能就是头文件变变的事吧。改动不应该那么大啊。

Godbach

LZ要分请什么是target啊。你的这个程序相当于在内核态处理完了数据包。不需要在用户空间的什么程序了。当然，程序本身还有问题

BTW，这个程序和内核版的有个程序怎么一样啊，呵呵

dreamice

原帖由 emmoblin 于 2008-12-20 17:10 发表
我问一下：
2.6.18上测试通过了，在2.6.26上就不行了吗？
最多可能就是头文件变变的事吧。改动不应该那么大啊。

改动可能很大

ubuntuer

#include <linux/module.h> #include <linux/kernel.h> #include <linux/netfilter.h> #include <linux/skbuff.h> #include <linux/ip.h> #include <linux/netdevice.h> #include <linux/if_ether.h> #include <linux/if_packet.h> #include <net/tcp.h> #include <linux/netfilter_ipv4.h> unsigned int winnuke_local_in_func (unsigned int hooknum, &nbsp;&nbsp;&nbsp;&nbsp;   struct sk_buff *skb, &nbsp;&nbsp;&nbsp;&nbsp;   const struct net_device *in, &nbsp;&nbsp;&nbsp;&nbsp;   const struct net_device *out, &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;int (*okfn) (struct sk_buff *)) { &nbsp;&nbsp;struct iphdr *iph ; &nbsp;&nbsp;struct tcphdr *tcph ; &nbsp;&nbsp;struct tcphdr _otcph ; &nbsp;&nbsp; &nbsp;&nbsp;iph = ip_hdr (skb); &nbsp;&nbsp;switch (iph->protocol) &nbsp;&nbsp;&nbsp;&nbsp;{ &nbsp;&nbsp;&nbsp;&nbsp;case IPPROTO_TCP: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;printk ("It's a TCP PACKET\n"); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tcph = skb_header_pointer(skb,ip_hdrlen(skb),sizeof(_otcph),&_otcph); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IPPROTO_ICMP: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return NF_ACCEPT; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IPPROTO_UDP: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return NF_ACCEPT; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;default: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return NF_ACCEPT; &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;printk ("s_port=%d,d_port=%d!",(int)tcph->source,(int)tcph->dest); &nbsp;&nbsp;&nbsp;&nbsp;printk ("urg=%d",(int)tcph->urg); &nbsp;&nbsp;return NF_ACCEPT; } static struct nf_hook_ops winnuke_ops[] __read_mostly = { &nbsp;&nbsp;&nbsp;&nbsp;{ &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;.hook   = winnuke_local_in_func, &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;.owner  = THIS_MODULE, &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;.pf     = PF_INET, &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;.hooknum    = NF_INET_LOCAL_IN, &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;.priority   = NF_IP_PRI_FIRST, &nbsp;&nbsp;&nbsp;&nbsp;}, }; static int __init winnuke_init(void) { &nbsp;&nbsp;int ret; &nbsp;&nbsp;printk("ins winnuke module\n"); &nbsp;&nbsp;ret = nf_register_hook (winnuke_ops); &nbsp;&nbsp;if(ret < 0) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return ret; &nbsp;&nbsp;return 0; } static void __exit winnuke_fini(void) { &nbsp;&nbsp;&nbsp;&nbsp;printk("rm winnuke module\n"); &nbsp;&nbsp;&nbsp;&nbsp;nf_unregister_hook (winnuke_ops); } module_init(winnuke_init); module_exit(winnuke_fini);

dreamice

把你的思路整理一下，总结出来吧

Godbach

看来他这个程序是要做判断是否有WinNuke攻击呢。

dreamice

不清楚，感觉他这个目的性都不是很明确

Godbach

原帖由 dreamice 于 2008-12-23 11:08 发表
不清楚，感觉他这个目的性都不是很明确

看代码：

module_init(winnuke_init);
module_exit(winnuke_fini);

一般的TCP包中目的端口为137，138，139的会被视为Winnuke攻击