RFC 5389 PDF

Session Traversal Utilities for NAT (STUN) is a standardized set of methods, including a . The STUN protocol and method were updated in RFC , retaining many of the original specifications as a subset of methods, but removing others. 21 Oct STUN was first defined in RFC (standards) back in , and then revised two times once in RFC (standards) in and again in. Network Working Group J. Rosenberg Request for Comments: Cisco Obsoletes: R. Mahy Category: Standards Track P. Matthews Unaffiliated D.

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A magic cookie mechanism for demultiplexing STUN with application protocols was added by stealing 32 bits from the bit transaction ID defined in RFCallowing the change to be backwards compatible.


Rosenberg Request for Comments: Changes to Client Processing The specific scope of a short-term credential is defined by the application usage. UDP remains the same as before. It impacts a single client, which is frequently not the desired target.

In some cases, a usage will require extensions to STUN. The latter encodes it directly in binary. However, this would require administrators to repopulate their databases.

Since STUN aligns attributes on bit boundaries, attributes whose content is not a multiple of 4 bytes are padded with 1, 2, or 3 bytes of padding so that its value contains a multiple of 4 bytes. Fortunately, STUN requests can be processed statelessly by a server, making such attacks hard to launch.

However, it can only be launched against targets for which packets from the STUN server to the target pass through the attacker, limiting the cases in which it is 5839. When a client has evaluated its external address, rrfc can use this as a candidate for communicating with peers by sharing the external NAT address rather than the private address, which is not reachable from peers on the public network. Assuming the Identity of a Client Forming a Success or Error Response Short- term credentials are obtained through some kind of protocol mechanism between the client and server, preceding the STUN exchange.

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In this specification, the rc STUN client and client are synonymous. The structure of the key when used with long-term credentials facilitates deployment in systems that also utilize SIP.

The method and class are orthogonal, so that for each method, a request, success response, error response, and indication are possible for that method. Of course, once detected, the manipulated packets will be dropped, causing the STUN transaction to effectively fail. 5398 STUN usage must consider whether these attacks are applicable to it, and if so, discuss counter-measures.

In the short-term credential mechanism, the client and the server exchange a username and password through some out-of-band method prior to the STUN exchange. All fields must be in network byte order.

Attributes are divided into two types: The client should retry the request with proper credentials. Sending the Request or 53899 Distribution of this memo is unlimited. In common situations, modification of the reflexive address by an on-path attacker is easy to do.

A short-term credential has an explicit temporal scope, which may be based on a specific amount of time such as 5 minutes 53389 on an event such as termination of a SIP dialog. As a result, the source transport address of the request received by the server will be the public IP address and port created by the NAT closest to the server.

It supports two types of transactions. A STUN client can also send indications. The client, typically operating inside a private networksends a binding request to a STUN server on the public Internet. This attack is, as a result, only useful for observing traffic by attackers on the path from the client to the STUN server, but not generally on the path of packets being routed towards the client.


RFC – part 3 of 3

The message type defines the message rffc request, success response, failure response, or indication and the message method the primary function of the STUN message. STUN is a tool for communications protocols to detect and traverse network address translators that are located in the path between two endpoints of communication. Eavesdropping In this attack, the attacker forces the client to use a reflexive address that routes to itself.

The password from a long-term credential.

However, in order to launch the attack, the attacker must have already been able to observe packets from the client to the STUN rgc. C1 and C0 represent a 2-bit encoding of the class. Technical review of the extension itself is outside the scope of the designated expert responsibility. The attribute contains a list of bit values, each of which represents an attribute type that was not understood by the server.

Forming a Request or Indication This attack would allow the attacker to observe all packets sent to the client. Resends of the same request reuse the same transaction ID, but the client MUST choose a new transaction ID for new transactions unless the new request is bit-wise identical to the previous request and sent from the same transport address to the same IP address.

Network address translation is implemented via ffc number of different address and port mapping schemes, none of which is standardized. The padding bits are ignored, and may be any value.