Damien Diederen created ZOOKEEPER-3979:
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Summary: Clients can corrupt the audit log
Key: ZOOKEEPER-3979
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-3979
Project: ZooKeeper
Issue Type: Bug
Components: server
Reporter: Damien Diederen
Assignee: Damien Diederen
As discussed in [this
PR|https://github.com/apache/zookeeper/pull/1503#issuecomment-710549123], it is
possible for a client (authenticated or not) to "SPAM" and corrupt the audit
log.
As far as I can tell, the following works on any server, because the {{digest}}
provider is always active and accepts (almost) arbitrary strings:
{noformat}
addauth digest veryimport...@example.com:whatever
create /dangerousnode
{noformat}
Note that "whatever" in the example above doesn't have to be a known or valid
password. Similarly, the string to the left of {{:}} is not validated in any
way; it is just copied as-is into the {{Id}} associated with the connection.
This results in entries akin to the following in the audit log:
{noformat}
2020-10-15 09:40:43,173 INFO audit.Log4jAuditLogger: session=0x100eefe34a40000
user=zk...@crosstwine.com,veryimport...@example.com,0:0:0:0:0:0:0:1
ip=0:0:0:0:0:0:0:1 operation=create znode=/dangerousnode
znode_type=persistent result=success
{noformat}
Note how the scheme is not mentioned; all that is visible is the "user name"
part of the {{Id}}.
This could lead an hypothetical audit application to conclude that it was okay
for that connection to create {{/dangerousnode}} because it was "seriously"
authenticated as {{veryimport...@example.com}}.
It is possible to use that loophole to corrupt the audit log in various ways,
including creating fake entries. It is not even necessary to use a dedicated
client; {{Ctrl+Q Ctrl+J}} can cause literal newlines to be inserted via
{{zkCli.sh}}:
{noformat}
addauth digest "fakeid^JTHIS REALLY SHOULDN'T BE THERE:whatever"
{noformat}
The result is a "two-line entry" in the audit log:
{noformat}
2020-10-16 21:42:06,546 INFO audit.Log4jAuditLogger: session=0x100f6b85af80001
user="fakeid
THIS REALLY SHOULDN'T BE THERE,zk...@crosstwine.com,0:0:0:0:0:0:0:1
ip=0:0:0:0:0:0:0:1 operation=create znode=/yolo4
znode_type=persistent result=success
{noformat}
I would suggest:
# Adding a setting which allows disabling the {{digest}} provider on production
servers;
# Filtering (or quoting/escaping/censoring) the user names/principals which are
written to the audit log (by scheme, or perhaps by dangerous characters).
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