2018-07-02 16:05:52 -04:00
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# rkduck rootkit details
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https://github.com/QuokkaLight/rkduck
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## Environment
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- x86, x86_64
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- Linux kernel 4.x
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2018-07-03 16:40:46 -04:00
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- Debian/Ubuntu, RHEL/CentOS/Fedora
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2018-07-02 16:05:52 -04:00
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## Persistency
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2018-07-03 16:40:46 -04:00
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Boot-time module loading using OS-specific startup files:
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- /etc/modules (debian/ubuntu)
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- https://github.com/linux-rootkits/rkduck/blob/master/forever.sh#L29
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- /etc/rc.modules (redhat/centos/fedora)
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- https://github.com/linux-rootkits/rkduck/blob/master/forever.sh#L32
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Rootkit module runs `forever.sh` helper script at the moment of module unloading:
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- https://github.com/linux-rootkits/rkduck/blob/master/rkduck/duck.c#L47
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## Detection evasion
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Rootkit is trying to evade from detection by:
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- hiding rootkit files by name
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## Management interface
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Implemented via in-kernel `netlink` server (`NETLINK_USER`) :
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- https://github.com/linux-rootkits/rkduck/blob/master/rkduck/crumbs_serv.c#L142
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Supported commands are:
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- hiding/unhiding files
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- https://github.com/linux-rootkits/rkduck/blob/master/rkduck/crumbs_serv.c#L22
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- hiding/unhiding processes
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- https://github.com/linux-rootkits/rkduck/blob/master/rkduck/crumbs_serv.c#L32
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2018-07-04 05:40:34 -04:00
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## Altering system behaviour
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Hooking of system calls by patching syscall-handlers in `sys_call_table[]`:
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- hook `sys_call_table[__NR_write]` (disabled)
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- https://github.com/linux-rootkits/rkduck/blob/master/rkduck/duck.c#L17
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- hook `file->f_op->iterate` for `/` and `/proc` dentries
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- https://github.com/linux-rootkits/rkduck/blob/master/rkduck/duck.c#L25
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- https://github.com/linux-rootkits/rkduck/blob/master/rkduck/duck.c#L29
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- netfilter `NF_INET_PRE_ROUTING/NF_IP_PRI_FIRST` hook used for catching `ICMP` packets
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- https://github.com/linux-rootkits/rkduck/blob/master/rkduck/backdoor.c#L454
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- https://github.com/linux-rootkits/rkduck/blob/master/rkduck/backdoor.c#L379
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## Hiding of files and directories
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Filtering of directory entries:
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- https://github.com/linux-rootkits/rkduck/blob/master/rkduck/vfs.c#L323 (vfs_hide_file)
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- https://github.com/linux-rootkits/rkduck/blob/master/rkduck/vfs.c#L346 (vfs_unhide_file)
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- https://github.com/linux-rootkits/rkduck/blob/master/rkduck/vfs.c#L97 (vfs_hijacked_iterate)
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- https://github.com/linux-rootkits/rkduck/blob/master/rkduck/vfs.c#L59 (vfs_hijacked_filldir)
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- https://github.com/linux-rootkits/rkduck/blob/master/rkduck/vfs.c#L157 (vfs_hijacked_proc_iterate)
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- https://github.com/linux-rootkits/rkduck/blob/master/rkduck/vfs.c#L78 (vfs_hijacked_proc_filldir)
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