quic_lcidm.h
/*
* Copyright 2023 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#ifndef OSSL_INTERNAL_QUIC_LCIDM_H
# define OSSL_INTERNAL_QUIC_LCIDM_H
# pragma once
# include "internal/e_os.h"
# include "internal/time.h"
# include "internal/quic_types.h"
# include "internal/quic_wire.h"
# include "internal/quic_predef.h"
# ifndef OPENSSL_NO_QUIC
/*
* QUIC Local Connection ID Manager
* ================================
*
* This manages connection IDs for the RX side, which is to say that it issues
* local CIDs (LCIDs) to a peer which that peer can then use to address us via a
* packet DCID. This is as opposed to CID management for the TX side, which
* determines which CIDs we use to transmit based on remote CIDs (RCIDs) the
* peer sent to us.
*
* An opaque pointer can be associated with each LCID. Pointer identity
* (equality) is used to distinguish distinct connections.
*
* LCIDs fall into three categories:
*
* 1. A client's Initial ODCID (1)
* 2. Our local Initial SCID (1)
* 3. A CID issued via a NEW_CONNECTION_ID frame (n)
* 4. A server's Retry SCID (0..1)
*
* (1) is enrolled using ossl_quic_lcidm_enrol_odcid() and retired by the time
* of handshake completion at the latest. It is needed in case the first
* response packet from a server is lost and the client keeps using its Initial
* ODCID. There is never more than one of these, and no sequence number is
* associated with this temporary LCID.
*
* (2) is created by a client when it begins connecting, or by a server when it
* responds to a new connection request. In the latter case, it is generated by
* the server as the preferred DCID for traffic directed towards it. A client
* should switch to using this as a RCID as soon as it receives a valid packet
* from the server. This LCID has a sequence number of 0.
*
* (3) is created when we issue a NEW_CONNECTION_ID frame. Arbitrarily many of
* these can exist.
*
* (4) is a special case. When a server issues a retry it generates a new SCID
* much as it does for (2). However since retries are supposed to be stateless,
* we don't actually register it as an LCID. When the client subsequently
* replies with an Initial packet with token in response to the Retry, the
* server will handle this as a new connection attempt due to not recognising
* the DCID, which is what we want anyway. (The Retry SCID is subsequently
* validated as matching the new Initial ODCID via attestation in the encrypted
* contents of the opaque retry token.) Thus, the LCIDM is not actually involved
* at all here.
*
* Retirement is as follows:
*
* (1) is retired automatically when we know it won't be needed anymore. This is
* when the handshake is completed at the latest, and could potentially be
* earlier.
*
* Both (2) and (3) are retired normally via RETIRE_CONNECTION_ID frames, as it
* has a sequence number of 0.
*
*
* ODCID Peculiarities
* -------------------
*
* Almost all LCIDs are issued by the receiver responsible for routing them,
* which means that almost all LCIDs will have the same length (specified in
* lcid_len below). The only exception to this is (1); the ODCID is the only
* case where we recognise an LCID we didn't ourselves generate. Since an ODCID
* is chosen by the peer, it can be any length and doesn't necessarily match the
* length we use for LCIDs we generate ourselves.
*
* Since DCID decoding for short-header packets requires an implicitly known
* DCID length, it logically follows that an ODCID can never be used in a 1-RTT
* packet. This is fine as by the time the 1-RTT EL is reached the peer should
* already have switched away from the ODCID to a CID we generated ourselves,
* and if this has not happened we can consider that a protocol violation.
*
* In any case, this means that the LCIDM must necessarily support LCIDs of
* different lengths, even if it always generates LCIDs of a given length.
*
* An ODCID has no sequence number associated with it. It is the only CID to
* lack one.
*/
/*
* Creates a new LCIDM. lcid_len is the length to use for LCIDs in bytes, which
* may be zero.
*
* Returns NULL on failure.
*/
QUIC_LCIDM *ossl_quic_lcidm_new(OSSL_LIB_CTX *libctx, size_t lcid_len);
/* Frees a LCIDM. */
void ossl_quic_lcidm_free(QUIC_LCIDM *lcidm);
/* Gets the local CID length this LCIDM was configured to use. */
size_t ossl_quic_lcidm_get_lcid_len(const QUIC_LCIDM *lcidm);
/*
* Determines the number of active LCIDs (i.e,. LCIDs which can be used for
* reception) currently associated with the given opaque pointer.
*/
size_t ossl_quic_lcidm_get_num_active_lcid(const QUIC_LCIDM *lcidm,
void *opaque);
/*
* Enrol an Initial ODCID sent by the peer. This is the DCID in the first
* Initial packet sent by a client. When we receive a client's first Initial
* packet, we immediately respond with our own SCID (generated using
* ossl_quic_lcidm_generate_initial) to tell the client to switch to using that,
* so ideally the ODCID will only be used for a single packet. However since
* that response might be lost, we also need to accept additional packets using
* the ODCID and need to make sure they get routed to the same connection and
* not interpreted as another new connection attempt. Thus before the CID
* switchover is confirmed, we also have to handle incoming packets addressed to
* the ODCID. This function is used to temporarily enroll the ODCID for a
* connection. Such a LCID is considered to have a sequence number of
* LCIDM_ODCID_SEQ_NUM internally for our purposes.
*
* Note that this is the *only* circumstance where we recognise an LCID we did
* not generate ourselves, or allow an LCID with a different length to lcid_len.
*
* An ODCID MUST be at least 8 bytes in length (RFC 9000 s. 7.2).
*
* This function may only be called once for a given connection.
* Returns 1 on success or 0 on failure.
*/
int ossl_quic_lcidm_enrol_odcid(QUIC_LCIDM *lcidm, void *opaque,
const QUIC_CONN_ID *initial_odcid);
/*
* Retire a previously enrolled ODCID for a connection. This is generally done
* when we know the peer won't be using it any more (when the handshake is
* completed at the absolute latest, possibly earlier).
*
* Returns 1 if there was an enrolled ODCID which was retired and 0 if there was
* not or on other failure.
*/
int ossl_quic_lcidm_retire_odcid(QUIC_LCIDM *lcidm, void *opaque);
/*
* Create the first LCID for a given opaque pointer. The generated LCID is
* written to *initial_lcid and associated with the given opaque pointer.
*
* After this function returns successfully, the caller can for example
* register the new LCID with a DEMUX.
*
* May not be called more than once for a given opaque pointer value.
*/
int ossl_quic_lcidm_generate_initial(QUIC_LCIDM *lcidm,
void *opaque,
QUIC_CONN_ID *initial_lcid);
/*
* Create a subsequent LCID for a given opaque pointer. The information needed
* for a NEW_CONN_ID frame informing the peer of the new LCID, including the
* LCID itself, is written to *ncid_frame.
*
* ncid_frame->stateless_reset is not initialised and the caller is responsible
* for setting it.
*
* After this function returns successfully, the caller can for example
* register the new LCID with a DEMUX and queue the NEW_CONN_ID frame.
*/
int ossl_quic_lcidm_generate(QUIC_LCIDM *lcidm,
void *opaque,
OSSL_QUIC_FRAME_NEW_CONN_ID *ncid_frame);
/*
* Retire up to one LCID for a given opaque pointer value. Called repeatedly to
* handle a RETIRE_CONN_ID frame.
*
* If containing_pkt_dcid is non-NULL, this function enforces the requirement
* that a CID not be retired by a packet using that CID as the DCID. If
* containing_pkt_dcid is NULL, this check is skipped.
*
* If a LCID is retired as a result of a call to this function, the LCID which
* was retired is written to *retired_lcid, the sequence number of the LCID is
* written to *retired_seq_num and *did_retire is set to 1. Otherwise,
* *did_retire is set to 0. This enables a caller to e.g. unregister the LCID
* from a DEMUX. A caller should call this function repeatedly until the
* function returns with *did_retire set to 0.
*
* This call is likely to cause the value returned by
* ossl_quic_lcidm_get_num_active_lcid() to go down. A caller may wish to call
* ossl_quic_lcidm_generate() repeatedly to bring the number of active LCIDs
* back up to some threshold in response after calling this function.
*
* Returns 1 on success and 0 on failure. If arguments are valid but zero LCIDs
* are retired, this is considered a success condition.
*/
int ossl_quic_lcidm_retire(QUIC_LCIDM *lcidm,
void *opaque,
uint64_t retire_prior_to,
const QUIC_CONN_ID *containing_pkt_dcid,
QUIC_CONN_ID *retired_lcid,
uint64_t *retired_seq_num,
int *did_retire);
/*
* Cull all LCIDM state relating to a given opaque pointer value. This is useful
* if connection state is spontaneously freed. The caller is responsible for
* e.g. DEMUX state updates.
*/
int ossl_quic_lcidm_cull(QUIC_LCIDM *lcidm, void *opaque);
/*
* Lookup a LCID. If the LCID is found, writes the associated opaque pointer to
* *opaque and the associated sequence number to *seq_num. Returns 1 on success
* and 0 if an entry is not found. An output argument may be set to NULL if its
* value is not required.
*
* If the LCID is for an Initial ODCID, *seq_num is set to
* LCIDM_ODCID_SEQ_NUM.
*/
#define LCIDM_ODCID_SEQ_NUM UINT64_MAX
int ossl_quic_lcidm_lookup(QUIC_LCIDM *lcidm,
const QUIC_CONN_ID *lcid,
uint64_t *seq_num,
void **opaque);
/*
* Debug call to manually remove a specific LCID. Should not be needed in normal
* usage. Returns 1 if the LCID was successfully found and removed and 0
* otherwise.
*/
int ossl_quic_lcidm_debug_remove(QUIC_LCIDM *lcidm,
const QUIC_CONN_ID *lcid);
/*
* Debug call to manually add a numbered LCID with a specific CID value and
* sequence number. Should not be needed in normal usage. Returns 1 on success
* and 0 on failure.
*/
int ossl_quic_lcidm_debug_add(QUIC_LCIDM *lcidm, void *opaque,
const QUIC_CONN_ID *lcid,
uint64_t seq_num);
# endif
#endif
