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Google LLC

1600 Amphitheatre Parkway Mountain View, California 94043 United States of America dallasmccall@google.com

Google LLC

1600 Amphitheatre Parkway Mountain View, California 94043 United States of America dschinazi.ietf@gmail.com

MASQUE Internet-Draft This document describes the CONNECT-IP HTTP method. CONNECT-IP is similar to CONNECT-UDP, but allows transmitting IP packets, without being limited to just TCP like CONNECT or UDP like CONNECT-UDP. Discussion Venues Discussion of this document takes place on the Multiplexed Application Substrate over QUIC Encryption Working Group mailing list (masque@ietf.org), which is archived at . Source for this draft and an issue tracker can be found at .

Introduction This document describes the CONNECT-IP HTTP method. CONNECT-IP is similar to CONNECT-UDP, but allows transmitting IP packets, without being limited to just TCP like CONNECT or UDP like CONNECT-UDP. CONNECT-IP allows endpoints to set up an IP tunnel between one another. This can be used to implement a consumer VPN, point-to-point and point-to-network capabilities as described in .

Conventions and Definitions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here. In this document, we use the term "proxy" to refer to the HTTP server that responds to the CONNECT-IP request. If there are HTTP intermediaries (as defined in Section 2.3 of ) between the client and the proxy, those are referred to as "intermediaries" in this document.

The CONNECT-IP Method The CONNECT-IP method establishes a stream to an endpoint server that then permits the exchange of control data, such as IP address information and other relevant information for successfully transmitting IP datagrams between hosts. The request-target of a CONNECT-IP request is a URI which uses the "https" scheme and a client-specified path. When using HTTP/2 or later, CONNECT-IP requests use HTTP pseudo-headers with the following requirements:

• The ":method" pseudo-header field is set to "CONNECT-IP".
• The ":scheme" pseudo-header field is set to "https".
• The ":path" pseudo-header field is set to the value provided by the client. That value MUST NOT be empty.
• The ":authority" pseudo-header field contains the host and port of the proxy. The target of a CONNECT-IP request is the server providing the CONNECT-IP featureset, not an individual endpoint with which a connection is desired.

A CONNECT-IP request that does not conform to these restrictions is malformed (see , Section 8.1.2.6). Any 2xx (Successful) response indicates that the proxy is willing to open an IP tunnel between it and the client. Any response other than a successful response indicates that the tunnel has not yet been formed. A proxy MUST NOT send any Transfer-Encoding or Content-Length header fields in a 2xx (Successful) response to CONNECT-IP. A client MUST treat a successful response to CONNECT-IP containing any Content-Length or Transfer-Encoding header fields as malformed. A payload within a CONNECT-IP request message has no defined semantics; a CONNECT-IP request with a non-empty payload is malformed. Note that the CONNECT-IP stream is used to convey control messages, but they are not semantically part of the request or response themselves. Responses to the CONNECT-IP method are not cacheable. The lifetime of the tunnel is tied to the CONNECT-IP stream. Closing the stream (via the FIN bit on a QUIC STREAM frame, or a QUIC RESET_STREAM frame) closes the associated tunnel.

Transmitting IP Packets using HTTP Datagrams IP packets are sent using HTTP Datagrams . The HTTP Datagram Payload contains a full IP packet, from the IP Version field until the last byte of the IP Payload. In order to use HTTP Datagrams, the CONNECT-IP client will first decide whether or not to use HTTP Datagram Contexts and then register its context ID (or lack thereof) using the corresponding registration capsule, see . Since HTTP Datagrams require prior negotiation (for example, in HTTP/3 it is necessary to both send and receive the H3_DATAGRAM SETTINGS Parameter), clients MUST NOT send any HTTP Datagrams until they have established support on a given connection. If negotiation of HTTP Datagrams fails (for example if an HTTP/3 SETTINGS frame was received without the H3_DATAGRAM SETTINGS Parameter), the client MUST consider its CONNECT-IP request as failed.

Forwarding of IP Packets Since CONNECT-IP allows the transmission of IP packets over HTTP, CONNECT-IP endpoints will most often forward these packets to and from traditional IP interfaces. As such, CONNECT-IP endpoints act as IP routers. When a CONNECT-IP endpoint receives an HTTP Datagram containing an IP packet, it will parse the packet's IP header, perform any local policy checks (e.g., source address validation), check their routing table to pick an outbound interface, and then use an implementation-specific mechanism (such as raw sockets) to send the IP packet on that interface. Conversely, when a CONNECT-IP endpoint receives an IP packet whose destination address does not match any local addresses, it consults its routing table to pick a forwarding destination, and if the table points to a CONNECT-IP tunnel, the endpoint performs the same forwarding checks before transmitting the packet inside the tunnel. Note that CONNECT-IP endpoints will decrement the IP Hop Count (or TTL) upon encapsulation but not decapsulation. In other words, the Hop Count is decremented right before an IP packet is transmitted in an HTTP Datagram. This prevents infinite loops in the presence of routing loops, and matches the choices in IPsec . Endpoints MAY implement additional filtering policies on the IP packets they forward.

Capsules

ADDRESS_ASSIGN Capsule The ADDRESS_ASSIGN capsule allows an endpoint to inform its peer that it has assigned an IP address to it. It allows assigning a prefix which can contain multiple addresses. This capsule uses a Capsule Type of 0xfff100. Its value uses the following format:

ADDRESS_ASSIGN Capsule Format

IP Version:

IP Version of this address assignment. MUST be either 4 or 6.

IP Address:

Assigned IP address. If the IP Version field has value 4, the IP Address field SHALL have a length of 32 bits. If the IP Version field has value 6, the IP Address field SHALL have a length of 128 bits.

IP Prefix Length:

Length of the IP Prefix assigned, in bits. MUST be lesser or equal to the length of the IP Address field, in bits.

ADDRESS_REQUEST Capsule The ADDRESS_REQUEST capsule allows an endpoint to request assignment of an IP address from its peer. It allows the endpoint to optionally indicate a preference for which address it would get assigned. This capsule uses a Capsule Type of 0xfff101. Its value uses the following format:

ADDRESS_REQUEST Capsule Format

IP Version:

IP Version of this address request. MUST be either 4 or 6.

IP Address:

Requested IP address. If the IP Version field has value 4, the IP Address field SHALL have a length of 32 bits. If the IP Version field has value 6, the IP Address field SHALL have a length of 128 bits.

IP Prefix Length:

Length of the IP Prefix requested, in bits. MUST be lesser or equal to the length of the IP Address field, in bits.

Upon receiving the ADDRESS_REQUEST capsule, an endpoint SHOULD assign an IP address to its peer, and then respond with an ADDRESS_ASSIGN capsule to inform the peer of the assignment.

SHUTDOWN Capsule The SHUTDOWN capsule allows an endpoint to communicate to its peer that it is about to close the CONNECT-IP stream, with a string explaining the reason for the shutdown. This capsule uses a Capsule Type of 0xfff105. Its value uses the following format:

SHUTDOWN Capsule Format

Reason Phrase:

Additional diagnostic information for the shutdown. This SHOULD be a UTF-8 encoded string , though the frame does not carry information, such as language tags, that would aid comprehension by any entity other than the one that created the text.

Note that the SHUTDOWN capsule is informational, the tunnel is only closed when its corresponding CONNECT-IP stream is closed. Endpoints MAY close the tunnel with a reason phrase by sending the SHUTDOWN capsule with the FIN bit set on the underlying QUIC STREAM frame that carried it.

Extensibility Considerations CONNECT-IP can be extended via multiple mechanisms to increase functionality. There are three main ways to extend CONNECT-IP: HTTP headers, Capsule Types, and HTTP Datagram Registration Extension Data. For example, an authentication extension could define an HTTP header that allows endpoints to send authentication credentials to their peer during the creation of the tunnel. Alternatively, one could specify an extension that defines a new Capsule Type which allows exchanging DNS configuration between endpoints. Additionally, an extension to CONNECT-IP can use multiple HTTP Datagram Contexts simultaneously to compress some IP packets by associating the compression context with an HTTP Datagram Context ID.

Security Considerations There are significant risks in allowing arbitrary clients to establish a tunnel to arbitrary servers, as that could allow bad actors to send traffic and have it attributed to the proxy. Proxies that support CONNECT-IP SHOULD restrict its use to authenticated users. The HTTP Authorization header MAY be used to authenticate clients. More complex authentication schemes are out of scope for this document but can be implemented using CONNECT-IP extensions. Since CONNECT-IP endpoints can proxy IP packets send by their peer, they SHOULD follow the guidance in to help prevent denial of service attacks.

IANA Considerations

HTTP Method This document will request IANA to register "CONNECT-IP" in the HTTP Method Registry (IETF review) maintained at <>.

Capsule Type Registrations This document will request IANA to add the following values to the "HTTP Capsule Types" registry created by :

References Normative References In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. The Hypertext Transfer Protocol (HTTP) is a stateless application-level protocol for distributed, collaborative, hypertext information systems. This document provides an overview of HTTP architecture and its associated terminology, defines the "http" and "https" Uniform Resource Identifier (URI) schemes, defines the HTTP/1.1 message syntax and parsing requirements, and describes related security concerns for implementations. A Uniform Resource Identifier (URI) is a compact sequence of characters that identifies an abstract or physical resource. This specification defines the generic URI syntax and a process for resolving URI references that might be in relative form, along with guidelines and security considerations for the use of URIs on the Internet. The URI syntax defines a grammar that is a superset of all valid URIs, allowing an implementation to parse the common components of a URI reference without knowing the scheme-specific requirements of every possible identifier. This specification does not define a generative grammar for URIs; that task is performed by the individual specifications of each URI scheme. [STANDARDS-TRACK] This specification describes an optimized expression of the semantics of the Hypertext Transfer Protocol (HTTP), referred to as HTTP version 2 (HTTP/2). HTTP/2 enables a more efficient use of network resources and a reduced perception of latency by introducing header field compression and allowing multiple concurrent exchanges on the same connection. It also introduces unsolicited push of representations from servers to clients. This specification is an alternative to, but does not obsolete, the HTTP/1.1 message syntax. HTTP's existing semantics remain unchanged. Google LLC Cloudflare The QUIC DATAGRAM extension provides application protocols running over QUIC with a mechanism to send unreliable data while leveraging the security and congestion-control properties of QUIC. However, QUIC DATAGRAM frames do not provide a means to demultiplex application contexts. This document describes how to use QUIC DATAGRAM frames when the application protocol running over QUIC is HTTP/3. It associates datagrams with client-initiated bidirectional streams and defines an optional additional demultiplexing layer. Additionally, this document defines how to convey datagrams over prior versions of HTTP. ISO/IEC 10646-1 defines a large character set called the Universal Character Set (UCS) which encompasses most of the world's writing systems. The originally proposed encodings of the UCS, however, were not compatible with many current applications and protocols, and this has led to the development of UTF-8, the object of this memo. UTF-8 has the characteristic of preserving the full US-ASCII range, providing compatibility with file systems, parsers and other software that rely on US-ASCII values but are transparent to other values. This memo obsoletes and replaces RFC 2279. This paper discusses a simple, effective, and straightforward method for using ingress traffic filtering to prohibit DoS (Denial of Service) attacks which use forged IP addresses to be propagated from 'behind' an Internet Service Provider's (ISP) aggregation point. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. Informative References Google LLC Google LLC Google LLC There is interest among MASQUE working group participants in designing a protocol that can proxy IP traffic over HTTP. This document describes the set of requirements for such a protocol. Discussion of this work is encouraged to happen on the MASQUE IETF mailing list masque@ietf.org or on the GitHub repository which contains the draft: https://github.com/ietf-wg-masque/draft-ietf- masque-ip-proxy-reqs. This document describes an updated version of the "Security Architecture for IP", which is designed to provide security services for traffic at the IP layer. This document obsoletes RFC 2401 (November 1998). [STANDARDS-TRACK] The Hypertext Transfer Protocol (HTTP) is a stateless application- level protocol for distributed, collaborative, hypermedia information systems. This document defines the HTTP Authentication framework.

Examples

Consumer VPN In this scenario, the client will typically receive a single IP address that the proxy has picked from a pool of addresses it maintains. The client will route all traffic through the tunnel. The exchange could look as follows: IP Version = 4 IP Address = 0.0.0.0 IP Prefix Length = 0 <-------- ADDRESS_ASSIGN IP Version = 4 IP Address = 192.0.2.42 IP Prefix Length = 32 ]]>

Acknowledgments The design of CONNECT-IP was inspired by discussions in the MASQUE working group around . The authors would like to thank participants in those discussions for their feedback.