[jira] [Created] (ZOOKEEPER-3979) Clients can corrupt the audit log

["Damien Diederen (Jira)" <ji...@apache.org>]

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 veryimportant@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=zkcli@CROSSTWINE.COM,veryimportant@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 {{veryimportant@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,zkcli@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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