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correct rule conditions to support syscall variants #1250

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merged 3 commits into from
Jun 10, 2020
Merged

correct rule conditions to support syscall variants #1250

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a300892
rule(macro bin_dir_mkdir): correct condition to catch `mkdirat` case
leogr Jun 4, 2020
564b9d1
rule(macro bin_dir_rename): correct condition to catch all variants
leogr Jun 4, 2020
156521c
rule(Create files below dev): correct condition to catch `openat`
leogr Jun 4, 2020
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33 changes: 23 additions & 10 deletions rules/falco_rules.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,7 @@
- macro: proc_name_exists
condition: (proc.name!="<NA>")

# todo(leogr): we miss "renameat2", but it's not yet supported by sinsp
- macro: rename
condition: evt.type in (rename, renameat)
- macro: mkdir
Expand All @@ -80,17 +81,29 @@

- macro: bin_dir_mkdir
condition: >
(evt.arg[1] startswith /bin/ or
evt.arg[1] startswith /sbin/ or
evt.arg[1] startswith /usr/bin/ or
evt.arg[1] startswith /usr/sbin/)
(evt.arg.path startswith /bin/ or
evt.arg.path startswith /sbin/ or
evt.arg.path startswith /usr/bin/ or
evt.arg.path startswith /usr/sbin/)

- macro: bin_dir_rename
condition: >
evt.arg[1] startswith /bin/ or
evt.arg[1] startswith /sbin/ or
evt.arg[1] startswith /usr/bin/ or
evt.arg[1] startswith /usr/sbin/
(evt.arg.path startswith /bin/ or
evt.arg.path startswith /sbin/ or
evt.arg.path startswith /usr/bin/ or
evt.arg.path startswith /usr/sbin/ or
evt.arg.name startswith /bin/ or
evt.arg.name startswith /sbin/ or
evt.arg.name startswith /usr/bin/ or
evt.arg.name startswith /usr/sbin/ or
evt.arg.oldpath startswith /bin/ or
evt.arg.oldpath startswith /sbin/ or
evt.arg.oldpath startswith /usr/bin/ or
evt.arg.oldpath startswith /usr/sbin/ or
evt.arg.newpath startswith /bin/ or
evt.arg.newpath startswith /sbin/ or
evt.arg.newpath startswith /usr/bin/ or
evt.arg.newpath startswith /usr/sbin/)

- macro: etc_dir
condition: fd.name startswith /etc/
Expand Down Expand Up @@ -1505,7 +1518,7 @@

- rule: Modify binary dirs
desc: an attempt to modify any file below a set of binary directories.
condition: (bin_dir_rename) and modify and not package_mgmt_procs and not exe_running_docker_save
condition: bin_dir_rename and modify and not package_mgmt_procs and not exe_running_docker_save
output: >
File below known binary directory renamed/removed (user=%user.name command=%proc.cmdline
pcmdline=%proc.pcmdline operation=%evt.type file=%fd.name %evt.args container_id=%container.id image=%container.image.repository)
Expand Down Expand Up @@ -2225,7 +2238,7 @@
desc: creating any files below /dev other than known programs that manage devices. Some rootkits hide files in /dev.
condition: >
fd.directory = /dev and
(evt.type = creat or (evt.type = open and evt.arg.flags contains O_CREAT))
(evt.type = creat or ((evt.type = open or evt.type = openat) and evt.arg.flags contains O_CREAT))
and not proc.name in (dev_creation_binaries)
and not fd.name in (allowed_dev_files)
and not fd.name startswith /dev/tty
Expand Down