xref: /openssl/include/internal/quic_lcidm.h (revision ff3a26b2)
1 /*
2 * Copyright 2023 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (the "License").  You may not use
5 * this file except in compliance with the License.  You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9 
10 #ifndef OSSL_INTERNAL_QUIC_LCIDM_H
11 # define OSSL_INTERNAL_QUIC_LCIDM_H
12 # pragma once
13 
14 # include "internal/e_os.h"
15 # include "internal/time.h"
16 # include "internal/quic_types.h"
17 # include "internal/quic_wire.h"
18 # include "internal/quic_predef.h"
19 
20 # ifndef OPENSSL_NO_QUIC
21 
22 /*
23  * QUIC Local Connection ID Manager
24  * ================================
25  *
26  * This manages connection IDs for the RX side, which is to say that it issues
27  * local CIDs (LCIDs) to a peer which that peer can then use to address us via a
28  * packet DCID. This is as opposed to CID management for the TX side, which
29  * determines which CIDs we use to transmit based on remote CIDs (RCIDs) the
30  * peer sent to us.
31  *
32  * An opaque pointer can be associated with each LCID. Pointer identity
33  * (equality) is used to distinguish distinct connections.
34  *
35  * LCIDs fall into three categories:
36  *
37  *   1. A client's Initial ODCID                       (1)
38  *   2. Our local Initial SCID                         (1)
39  *   3. A CID issued via a NEW_CONNECTION_ID frame     (n)
40  *   4. A server's Retry SCID                          (0..1)
41  *
42  * (1) is enrolled using ossl_quic_lcidm_enrol_odcid() and retired by the time
43  * of handshake completion at the latest. It is needed in case the first
44  * response packet from a server is lost and the client keeps using its Initial
45  * ODCID. There is never more than one of these, and no sequence number is
46  * associated with this temporary LCID.
47  *
48  * (2) is created by a client when it begins connecting, or by a server when it
49  * responds to a new connection request. In the latter case, it is generated by
50  * the server as the preferred DCID for traffic directed towards it. A client
51  * should switch to using this as a RCID as soon as it receives a valid packet
52  * from the server. This LCID has a sequence number of 0.
53  *
54  * (3) is created when we issue a NEW_CONNECTION_ID frame. Arbitrarily many of
55  * these can exist.
56  *
57  * (4) is a special case. When a server issues a retry it generates a new SCID
58  * much as it does for (2). However since retries are supposed to be stateless,
59  * we don't actually register it as an LCID. When the client subsequently
60  * replies with an Initial packet with token in response to the Retry, the
61  * server will handle this as a new connection attempt due to not recognising
62  * the DCID, which is what we want anyway. (The Retry SCID is subsequently
63  * validated as matching the new Initial ODCID via attestation in the encrypted
64  * contents of the opaque retry token.) Thus, the LCIDM is not actually involved
65  * at all here.
66  *
67  * Retirement is as follows:
68  *
69  * (1) is retired automatically when we know it won't be needed anymore. This is
70  * when the handshake is completed at the latest, and could potentially be
71  * earlier.
72  *
73  * Both (2) and (3) are retired normally via RETIRE_CONNECTION_ID frames, as it
74  * has a sequence number of 0.
75  *
76  *
77  * ODCID Peculiarities
78  * -------------------
79  *
80  * Almost all LCIDs are issued by the receiver responsible for routing them,
81  * which means that almost all LCIDs will have the same length (specified in
82  * lcid_len below). The only exception to this is (1); the ODCID is the only
83  * case where we recognise an LCID we didn't ourselves generate. Since an ODCID
84  * is chosen by the peer, it can be any length and doesn't necessarily match the
85  * length we use for LCIDs we generate ourselves.
86  *
87  * Since DCID decoding for short-header packets requires an implicitly known
88  * DCID length, it logically follows that an ODCID can never be used in a 1-RTT
89  * packet. This is fine as by the time the 1-RTT EL is reached the peer should
90  * already have switched away from the ODCID to a CID we generated ourselves,
91  * and if this has not happened we can consider that a protocol violation.
92  *
93  * In any case, this means that the LCIDM must necessarily support LCIDs of
94  * different lengths, even if it always generates LCIDs of a given length.
95  *
96  * An ODCID has no sequence number associated with it. It is the only CID to
97  * lack one.
98  */
99 
100 /*
101  * Creates a new LCIDM. lcid_len is the length to use for LCIDs in bytes, which
102  * may be zero.
103  *
104  * Returns NULL on failure.
105  */
106 QUIC_LCIDM *ossl_quic_lcidm_new(OSSL_LIB_CTX *libctx, size_t lcid_len);
107 
108 /* Frees a LCIDM. */
109 void ossl_quic_lcidm_free(QUIC_LCIDM *lcidm);
110 
111 /* Gets the local CID length this LCIDM was configured to use. */
112 size_t ossl_quic_lcidm_get_lcid_len(const QUIC_LCIDM *lcidm);
113 
114 /*
115  * Determines the number of active LCIDs (i.e,. LCIDs which can be used for
116  * reception) currently associated with the given opaque pointer.
117  */
118 size_t ossl_quic_lcidm_get_num_active_lcid(const QUIC_LCIDM *lcidm,
119                                            void *opaque);
120 
121 /*
122  * Enrol an Initial ODCID sent by the peer. This is the DCID in the first
123  * Initial packet sent by a client. When we receive a client's first Initial
124  * packet, we immediately respond with our own SCID (generated using
125  * ossl_quic_lcidm_generate_initial) to tell the client to switch to using that,
126  * so ideally the ODCID will only be used for a single packet. However since
127  * that response might be lost, we also need to accept additional packets using
128  * the ODCID and need to make sure they get routed to the same connection and
129  * not interpreted as another new connection attempt. Thus before the CID
130  * switchover is confirmed, we also have to handle incoming packets addressed to
131  * the ODCID. This function is used to temporarily enroll the ODCID for a
132  * connection. Such a LCID is considered to have a sequence number of
133  * LCIDM_ODCID_SEQ_NUM internally for our purposes.
134  *
135  * Note that this is the *only* circumstance where we recognise an LCID we did
136  * not generate ourselves, or allow an LCID with a different length to lcid_len.
137  *
138  * An ODCID MUST be at least 8 bytes in length (RFC 9000 s. 7.2).
139  *
140  * This function may only be called once for a given connection.
141  * Returns 1 on success or 0 on failure.
142  */
143 int ossl_quic_lcidm_enrol_odcid(QUIC_LCIDM *lcidm, void *opaque,
144                                 const QUIC_CONN_ID *initial_odcid);
145 
146 /*
147  * Retire a previously enrolled ODCID for a connection. This is generally done
148  * when we know the peer won't be using it any more (when the handshake is
149  * completed at the absolute latest, possibly earlier).
150  *
151  * Returns 1 if there was an enrolled ODCID which was retired and 0 if there was
152  * not or on other failure.
153  */
154 int ossl_quic_lcidm_retire_odcid(QUIC_LCIDM *lcidm, void *opaque);
155 
156 /*
157  * Create the first LCID for a given opaque pointer. The generated LCID is
158  * written to *initial_lcid and associated with the given opaque pointer.
159  *
160  * After this function returns successfully, the caller can for example
161  * register the new LCID with a DEMUX.
162  *
163  * May not be called more than once for a given opaque pointer value.
164  */
165 int ossl_quic_lcidm_generate_initial(QUIC_LCIDM *lcidm,
166                                      void *opaque,
167                                      QUIC_CONN_ID *initial_lcid);
168 
169 /*
170  * Create a subsequent LCID for a given opaque pointer. The information needed
171  * for a NEW_CONN_ID frame informing the peer of the new LCID, including the
172  * LCID itself, is written to *ncid_frame.
173  *
174  * ncid_frame->stateless_reset is not initialised and the caller is responsible
175  * for setting it.
176  *
177  * After this function returns successfully, the caller can for example
178  * register the new LCID with a DEMUX and queue the NEW_CONN_ID frame.
179  */
180 int ossl_quic_lcidm_generate(QUIC_LCIDM *lcidm,
181                              void *opaque,
182                              OSSL_QUIC_FRAME_NEW_CONN_ID *ncid_frame);
183 
184 /*
185  * Retire up to one LCID for a given opaque pointer value. Called repeatedly to
186  * handle a RETIRE_CONN_ID frame.
187  *
188  * If containing_pkt_dcid is non-NULL, this function enforces the requirement
189  * that a CID not be retired by a packet using that CID as the DCID. If
190  * containing_pkt_dcid is NULL, this check is skipped.
191  *
192  * If a LCID is retired as a result of a call to this function, the LCID which
193  * was retired is written to *retired_lcid, the sequence number of the LCID is
194  * written to *retired_seq_num and *did_retire is set to 1. Otherwise,
195  * *did_retire is set to 0. This enables a caller to e.g. unregister the LCID
196  * from a DEMUX. A caller should call this function repeatedly until the
197  * function returns with *did_retire set to 0.
198  *
199  * This call is likely to cause the value returned by
200  * ossl_quic_lcidm_get_num_active_lcid() to go down. A caller may wish to call
201  * ossl_quic_lcidm_generate() repeatedly to bring the number of active LCIDs
202  * back up to some threshold in response after calling this function.
203  *
204  * Returns 1 on success and 0 on failure. If arguments are valid but zero LCIDs
205  * are retired, this is considered a success condition.
206  */
207 int ossl_quic_lcidm_retire(QUIC_LCIDM *lcidm,
208                            void *opaque,
209                            uint64_t retire_prior_to,
210                            const QUIC_CONN_ID *containing_pkt_dcid,
211                            QUIC_CONN_ID *retired_lcid,
212                            uint64_t *retired_seq_num,
213                            int *did_retire);
214 
215 /*
216  * Cull all LCIDM state relating to a given opaque pointer value. This is useful
217  * if connection state is spontaneously freed. The caller is responsible for
218  * e.g. DEMUX state updates.
219  */
220 int ossl_quic_lcidm_cull(QUIC_LCIDM *lcidm, void *opaque);
221 
222 /*
223  * Lookup a LCID. If the LCID is found, writes the associated opaque pointer to
224  * *opaque and the associated sequence number to *seq_num. Returns 1 on success
225  * and 0 if an entry is not found. An output argument may be set to NULL if its
226  * value is not required.
227  *
228  * If the LCID is for an Initial ODCID, *seq_num is set to
229  * LCIDM_ODCID_SEQ_NUM.
230  */
231 #define LCIDM_ODCID_SEQ_NUM     UINT64_MAX
232 
233 int ossl_quic_lcidm_lookup(QUIC_LCIDM *lcidm,
234                            const QUIC_CONN_ID *lcid,
235                            uint64_t *seq_num,
236                            void **opaque);
237 
238 /*
239  * Debug call to manually remove a specific LCID. Should not be needed in normal
240  * usage. Returns 1 if the LCID was successfully found and removed and 0
241  * otherwise.
242  */
243 int ossl_quic_lcidm_debug_remove(QUIC_LCIDM *lcidm,
244                                  const QUIC_CONN_ID *lcid);
245 
246 /*
247  * Debug call to manually add a numbered LCID with a specific CID value and
248  * sequence number. Should not be needed in normal usage. Returns 1 on success
249  * and 0 on failure.
250  */
251 int ossl_quic_lcidm_debug_add(QUIC_LCIDM *lcidm, void *opaque,
252                               const QUIC_CONN_ID *lcid,
253                               uint64_t seq_num);
254 
255 # endif
256 
257 #endif
258