[
https://issues.apache.org/jira/browse/DIRAPI-437?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18120093#comment-18120093
]
Emmanuel Lécharny commented on DIRAPI-437:
------------------------------------------
The API now has a MAX_PDU_SIZE set to 8Mo.
This default value can be changed with a call the the
_LdapConnectionConfig.setMaxPDUSize()_ method:
{code:java}
LdapConnectionConfig config = new LdapConnectionConfig();
// Set the max PDU size to 1MB
config.setMaxPduSize( 1*1024*1024 );
LdapNetworkConnection connection = new LdapNetworkConnection( config );
// And now use the connection to do operation with a limited PDU size
...
{code}
Note: ApacheDS has a configuration parameter that is used to set this limit:
_ads-maxPDUSize_.
> Attacker-declared TLV length drives up-front unbounded byte[] allocation; no
> default PDU cap
> ---------------------------------------------------------------------------------------------
>
> Key: DIRAPI-437
> URL: https://issues.apache.org/jira/browse/DIRAPI-437
> Project: Directory Client API
> Issue Type: Bug
> Affects Versions: 2.1.8
> Reporter: Emmanuel Lécharny
> Priority: Major
> Fix For: 2.1.9
>
>
> A malicious or compromised *LDAP* server (or *MITM* before *StartTLS*) sends
> ~12-20 bytes, e.g. _30 84 7F FF FF F0 (SEQUENCE) 02 84 7F FF FF EA (INTEGER
> declaring ~2GB)_: _treatValueStartState_ executes _new byte[0x7FFFFFEA]
> _before any body bytes arrive.
> The client *JVM OOMs* (_OutOfMemoryError_ bypasses the _DecoderException_
> handlers) or pins ~2 GB per connection while the attacker stalls; a handful
> of connections exhausts any heap. The same bytes from an unauthenticated
> pre-bind client hit any embedding server that did not set _MAX_PDU_SIZE_ATTR_
> _Asn1Decoder.treatValueStartState_ calls
> _currentTlv.getValue().init(length);_
> _BerValue.init_ executes _data = new byte[size]_ using the length taken
> directly from the wire, before a single value byte has arrived.
> The only guard, _length > container.getMaxPDUSize()_ in _treatLengthEndState_
> (:360-363), is vacuous: _AbstractContainer.maxPDUSize_ defaults to
> _Integer.MAX_VALUE_ and _setMaxPDUSize_ is invoked only from
> _LdapProtocolDecoder.decode_ when the embedder has stored the
> _LdapDecoder.MAX_PDU_SIZE_ATTR_ *MINA* session attribute — which nothing in
> this library ever does.
> _LdapNetworkConnection.setBinaryDetector_ and _sessionCreated_ create the
> _LdapMessageContainer_ without touching _maxPDUSize_, and
> _LdapConnectionConfig_ has no PDU-size knob at all, so every client
> connection decodes with an effectively unlimited PDU size; the server role
> has the same default unless the embedder (e.g. *ApacheDS*) opts in.
> The 4-byte length-field cap and negative-length check bound the declared
> length only to <= 0x7FFFFFFF.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
