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rule(Write below etc): whitelist automount writing under /etc/mtab #957

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Dec 5, 2019
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rule(Write below etc): whitelist automount writing under /etc/mtab #957

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4 changes: 4 additions & 0 deletions rules/falco_rules.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -1153,6 +1153,9 @@
- macro: etcd_manager_updating_dns
condition: (container and proc.name=etcd-manager and fd.name=/etc/hosts)

- macro: automount_using_mtab
condition: (proc.pname = automount and fd.name startswith /etc/mtab)
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Suggested change
condition: (proc.pname = automount and fd.name startswith /etc/mtab)
condition: (proc.pname=automount and fd.name=/etc/mtab)

WDYT?

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@leodido leodido Dec 5, 2019 •
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After having spent some hours with Nicolas on this we decided to merge PR as is.

He used startswith because he had automount daemon writing to /etc/mtab.[something] file (which to me seems something happening when the /etc/mtab file cannot be written because it's locked, maybe some other process writing to it?).

In the next days he's going to observe again the original event in order to understand whether it is better to use equal or startswith here.


# Add conditions to this macro (probably in a separate file,
# overwriting this macro) to allow for specific combinations of
# programs writing below specific directories below
Expand Down Expand Up @@ -1269,6 +1272,7 @@
and not jboss_in_container_writing_passwd
and not etcd_manager_updating_dns
and not user_known_write_below_etc_activities
and not automount_using_mtab

- rule: Write below etc
desc: an attempt to write to any file below /etc
Expand Down