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server: config entry replication now correctly uses namespaces in comparisons #9024
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…parisons Previously config entries sharing a kind & name but in different namespaces could occasionally cause "stuck states" in replication because the namespace fields were ignored during the differential comparison phase. Example: Two config entries written to the primary: kind=A,name=web,namespace=bar kind=A,name=web,namespace=foo Under the covers these both get saved to memdb, so they are sorted by all 3 components (kind,name,namespace) during natural iteration. This means that before the replication code does it's own incomplete sort, the underlying data IS sorted by namespace ascending (bar comes before foo). After one pass of replication the primary and secondary datacenters have the same set of config entries present. If "kind=A,name=web,namespace=bar" were to be deleted, then things get weird. Before replication the two sides look like: primary: [ kind=A,name=web,namespace=foo ] secondary: [ kind=A,name=web,namespace=bar kind=A,name=web,namespace=foo ] The differential comparison phase walks these two lists in sorted order and first compares "kind=A,name=web,namespace=foo" vs "kind=A,name=web,namespace=bar" and falsely determines they are the SAME and are thus cause an update of "kind=A,name=web,namespace=foo". Then it compares "<nothing>" with "kind=A,name=web,namespace=foo" and falsely determines that the latter should be DELETED. During reconciliation the deletes are processed before updates, and so for a brief moment in the secondary "kind=A,name=web,namespace=foo" is erroneously deleted and then immediately restored. Unfortunately after this replication phase the final state is identical to the initial state, so when it loops around again (rate limited) it repeats the same set of operations indefinitely.
mikemorris
approved these changes
Oct 23, 2020
picatz
approved these changes
Oct 23, 2020
🍒✅ Cherry pick of commit 58387fe onto |
hashicorp-ci
pushed a commit
that referenced
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Oct 23, 2020
…parisons (#9024) Previously config entries sharing a kind & name but in different namespaces could occasionally cause "stuck states" in replication because the namespace fields were ignored during the differential comparison phase. Example: Two config entries written to the primary: kind=A,name=web,namespace=bar kind=A,name=web,namespace=foo Under the covers these both get saved to memdb, so they are sorted by all 3 components (kind,name,namespace) during natural iteration. This means that before the replication code does it's own incomplete sort, the underlying data IS sorted by namespace ascending (bar comes before foo). After one pass of replication the primary and secondary datacenters have the same set of config entries present. If "kind=A,name=web,namespace=bar" were to be deleted, then things get weird. Before replication the two sides look like: primary: [ kind=A,name=web,namespace=foo ] secondary: [ kind=A,name=web,namespace=bar kind=A,name=web,namespace=foo ] The differential comparison phase walks these two lists in sorted order and first compares "kind=A,name=web,namespace=foo" vs "kind=A,name=web,namespace=bar" and falsely determines they are the SAME and are thus cause an update of "kind=A,name=web,namespace=foo". Then it compares "<nothing>" with "kind=A,name=web,namespace=foo" and falsely determines that the latter should be DELETED. During reconciliation the deletes are processed before updates, and so for a brief moment in the secondary "kind=A,name=web,namespace=foo" is erroneously deleted and then immediately restored. Unfortunately after this replication phase the final state is identical to the initial state, so when it loops around again (rate limited) it repeats the same set of operations indefinitely.
🍒✅ Cherry pick of commit 58387fe onto |
hashicorp-ci
pushed a commit
that referenced
this pull request
Oct 23, 2020
…parisons (#9024) Previously config entries sharing a kind & name but in different namespaces could occasionally cause "stuck states" in replication because the namespace fields were ignored during the differential comparison phase. Example: Two config entries written to the primary: kind=A,name=web,namespace=bar kind=A,name=web,namespace=foo Under the covers these both get saved to memdb, so they are sorted by all 3 components (kind,name,namespace) during natural iteration. This means that before the replication code does it's own incomplete sort, the underlying data IS sorted by namespace ascending (bar comes before foo). After one pass of replication the primary and secondary datacenters have the same set of config entries present. If "kind=A,name=web,namespace=bar" were to be deleted, then things get weird. Before replication the two sides look like: primary: [ kind=A,name=web,namespace=foo ] secondary: [ kind=A,name=web,namespace=bar kind=A,name=web,namespace=foo ] The differential comparison phase walks these two lists in sorted order and first compares "kind=A,name=web,namespace=foo" vs "kind=A,name=web,namespace=bar" and falsely determines they are the SAME and are thus cause an update of "kind=A,name=web,namespace=foo". Then it compares "<nothing>" with "kind=A,name=web,namespace=foo" and falsely determines that the latter should be DELETED. During reconciliation the deletes are processed before updates, and so for a brief moment in the secondary "kind=A,name=web,namespace=foo" is erroneously deleted and then immediately restored. Unfortunately after this replication phase the final state is identical to the initial state, so when it loops around again (rate limited) it repeats the same set of operations indefinitely.
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Summary
An operator with
service:write
ACL permissions in a Consul Enterprise cluster can write a malicious config entry that causes infinite raft writes due to issues with the namespace replication logic. This can lead to an operator with access to one namespace to be able to temporarily delete a doppelgänger configuration in another namespace they should not have access to modify.This is CVE-2020-25201
Bug
Previously config entries sharing a kind & name but in different
namespaces could occasionally cause "stuck states" in replication
because the namespace fields were ignored during the differential
comparison phase.
Example:
Two config entries written to the primary:
Under the covers these both get saved to memdb, so they are sorted by
all 3 components (kind,name,namespace) during natural iteration. This
means that before the replication code does it's own incomplete sort,
the underlying data IS sorted by namespace ascending (bar comes before
foo).
After one pass of replication the primary and secondary datacenters have
the same set of config entries present. If
"kind=A,name=web,namespace=bar"
were to be deleted, then things getweird. Before replication the two sides look like:
The differential comparison phase walks these two lists in sorted order
and first compares
"kind=A,name=web,namespace=foo"
vs"kind=A,name=web,namespace=bar"
and falsely determines they are the SAMEand are thus cause an update of
"kind=A,name=web,namespace=foo"
. Then itcompares
"<nothing>"
with"kind=A,name=web,namespace=foo"
and falselydetermines that the latter should be DELETED.
During reconciliation the deletes are processed before updates, and so
for a brief moment in the secondary
"kind=A,name=web,namespace=foo"
iserroneously deleted and then immediately restored.
Unfortunately after this replication phase the final state is identical
to the initial state, so when it loops around again (rate limited) it
repeats the same set of operations indefinitely.