/* * Copyright 2022-2023 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_QUIC_RECORD_RX_H # define OSSL_QUIC_RECORD_RX_H # include # include "internal/quic_wire_pkt.h" # include "internal/quic_types.h" # include "internal/quic_predef.h" # include "internal/quic_record_util.h" # include "internal/quic_demux.h" # ifndef OPENSSL_NO_QUIC /* * QUIC Record Layer - RX * ====================== */ typedef struct ossl_qrx_st OSSL_QRX; typedef struct ossl_qrx_args_st { OSSL_LIB_CTX *libctx; const char *propq; /* Demux which owns the URXEs passed to us. */ QUIC_DEMUX *demux; /* Length of connection IDs used in short-header packets in bytes. */ size_t short_conn_id_len; /* * Maximum number of deferred datagrams buffered at any one time. * Suggested value: 32. */ size_t max_deferred; /* Initial reference PN used for RX. */ QUIC_PN init_largest_pn[QUIC_PN_SPACE_NUM]; /* Initial key phase. For debugging use only; always 0 in real use. */ unsigned char init_key_phase_bit; } OSSL_QRX_ARGS; /* Instantiates a new QRX. */ OSSL_QRX *ossl_qrx_new(const OSSL_QRX_ARGS *args); /* * Frees the QRX. All packets obtained using ossl_qrx_read_pkt must already * have been released by calling ossl_qrx_release_pkt. * * You do not need to call ossl_qrx_remove_dst_conn_id first; this function will * unregister the QRX from the demuxer for all registered destination connection * IDs (DCIDs) automatically. */ void ossl_qrx_free(OSSL_QRX *qrx); /* Setters for the msg_callback and msg_callback_arg */ void ossl_qrx_set_msg_callback(OSSL_QRX *qrx, ossl_msg_cb msg_callback, SSL *msg_callback_ssl); void ossl_qrx_set_msg_callback_arg(OSSL_QRX *qrx, void *msg_callback_arg); /* * Secret Management * ================= * * A QRX has several encryption levels (Initial, Handshake, 0-RTT, 1-RTT) and * two directions (RX, TX). At any given time, key material is managed for each * (EL, RX/TX) combination. * * Broadly, for a given (EL, RX/TX), the following state machine is applicable: * * WAITING_FOR_KEYS --[Provide]--> HAVE_KEYS --[Discard]--> | DISCARDED | * \-------------------------------------[Discard]--> | | * * To transition the RX side of an EL from WAITING_FOR_KEYS to HAVE_KEYS, call * ossl_qrx_provide_secret (for the INITIAL EL, use of * ossl_quic_provide_initial_secret is recommended). * * Once keys have been provisioned for an EL, you call * ossl_qrx_discard_enc_level to transition the EL to the DISCARDED state. You * can also call this function to transition directly to the DISCARDED state * even before any keys have been provisioned for that EL. * * The DISCARDED state is terminal for a given EL; you cannot provide a secret * again for that EL after reaching it. * * Incoming packets cannot be processed and decrypted if they target an EL * not in the HAVE_KEYS state. However, there is a distinction between * the WAITING_FOR_KEYS and DISCARDED states: * * - In the WAITING_FOR_KEYS state, the QRX assumes keys for the given * EL will eventually arrive. Therefore, if it receives any packet * for an EL in this state, it buffers it and tries to process it * again once the EL reaches HAVE_KEYS. * * - In the DISCARDED state, the QRX assumes no keys for the given * EL will ever arrive again. If it receives any packet for an EL * in this state, it is simply discarded. * * If the user wishes to instantiate a new QRX to replace an old one for * whatever reason, for example to take over for an already established QUIC * connection, it is important that all ELs no longer being used (i.e., INITIAL, * 0-RTT, 1-RTT) are transitioned to the DISCARDED state. Otherwise, the QRX * will assume that keys for these ELs will arrive in future, and will buffer * any received packets for those ELs perpetually. This can be done by calling * ossl_qrx_discard_enc_level for all non-1-RTT ELs immediately after * instantiating the QRX. * * The INITIAL EL is not setup automatically when the QRX is instantiated. This * allows the caller to instead discard it immediately after instantiation of * the QRX if it is not needed, for example if the QRX is being instantiated to * take over handling of an existing connection which has already passed the * INITIAL phase. This avoids the unnecessary derivation of INITIAL keys where * they are not needed. In the ordinary case, ossl_quic_provide_initial_secret * should be called immediately after instantiation. */ /* * Provides a secret to the QRX, which arises due to an encryption level change. * enc_level is a QUIC_ENC_LEVEL_* value. To initialise the INITIAL encryption * level, it is recommended to use ossl_quic_provide_initial_secret instead. * * You should seek to call this function for a given EL before packets of that * EL arrive and are processed by the QRX. However, if packets have already * arrived for a given EL, the QRX will defer processing of them and perform * processing of them when this function is eventually called for the EL in * question. * * suite_id is a QRL_SUITE_* value which determines the AEAD function used for * the QRX. * * The secret passed is used directly to derive the "quic key", "quic iv" and * "quic hp" values. * * secret_len is the length of the secret buffer in bytes. The buffer must be * sized correctly to the chosen suite, else the function fails. * * This function can only be called once for a given EL, except for the INITIAL * EL, which can need rekeying when a connection retry occurs. Subsequent calls * for non-INITIAL ELs fail, as do calls made after a corresponding call to * ossl_qrx_discard_enc_level for that EL. The secret for a non-INITIAL EL * cannot be changed after it is set because QUIC has no facility for * introducing additional key material after an EL is setup. QUIC key updates * are managed semi-automatically by the QRX but do require some caller handling * (see below). * * md is for internal use and should be NULL. * * Returns 1 on success or 0 on failure. */ int ossl_qrx_provide_secret(OSSL_QRX *qrx, uint32_t enc_level, uint32_t suite_id, EVP_MD *md, const unsigned char *secret, size_t secret_len); /* * Informs the QRX that it can now discard key material for a given EL. The QRX * will no longer be able to process incoming packets received at that * encryption level. This function is idempotent and succeeds if the EL has * already been discarded. * * Returns 1 on success and 0 on failure. */ int ossl_qrx_discard_enc_level(OSSL_QRX *qrx, uint32_t enc_level); /* * Packet Reception * ================ */ /* Information about a received packet. */ struct ossl_qrx_pkt_st { /* * Points to a logical representation of the decoded QUIC packet header. The * data and len fields point to the decrypted QUIC payload (i.e., to a * sequence of zero or more (potentially malformed) frames to be decoded). */ QUIC_PKT_HDR *hdr; /* * Address the packet was received from. If this is not available for this * packet, this field is NULL (but this can only occur for manually injected * packets). */ const BIO_ADDR *peer; /* * Local address the packet was sent to. If this is not available for this * packet, this field is NULL. */ const BIO_ADDR *local; /* * This is the length of the datagram which contained this packet. Note that * the datagram may have contained other packets than this. The intended use * for this is so that the user can enforce minimum datagram sizes (e.g. for * datagrams containing INITIAL packets), as required by RFC 9000. */ size_t datagram_len; /* The PN which was decoded for the packet, if the packet has a PN field. */ QUIC_PN pn; /* * Time the packet was received, or ossl_time_zero() if the demuxer is not * using a now() function. */ OSSL_TIME time; /* The QRX which was used to receive the packet. */ OSSL_QRX *qrx; /* * The key epoch the packet was received with. Always 0 for non-1-RTT * packets. */ uint64_t key_epoch; /* * This monotonically increases with each datagram received. * It is for diagnostic use only. */ uint64_t datagram_id; }; /* * Tries to read a new decrypted packet from the QRX. * * On success, *pkt points to a OSSL_QRX_PKT structure. The structure should be * freed when no longer needed by calling ossl_qrx_pkt_release(). The structure * is refcounted; to gain extra references, call ossl_qrx_pkt_up_ref(). This * will cause a corresponding number of calls to ossl_qrx_pkt_release() to be * ignored. * * The resources referenced by (*pkt)->hdr, (*pkt)->hdr->data and (*pkt)->peer * have the same lifetime as *pkt. * * Returns 1 on success and 0 on failure. */ int ossl_qrx_read_pkt(OSSL_QRX *qrx, OSSL_QRX_PKT **pkt); /* * Decrement the reference count for the given packet and frees it if the * reference count drops to zero. No-op if pkt is NULL. */ void ossl_qrx_pkt_release(OSSL_QRX_PKT *pkt); /* Increments the reference count for the given packet. */ void ossl_qrx_pkt_up_ref(OSSL_QRX_PKT *pkt); /* * Returns 1 if there are any already processed (i.e. decrypted) packets waiting * to be read from the QRX. */ int ossl_qrx_processed_read_pending(OSSL_QRX *qrx); /* * Returns 1 if there are any unprocessed (i.e. not yet decrypted) packets * waiting to be processed by the QRX. These may or may not result in * successfully decrypted packets once processed. This indicates whether * unprocessed data is buffered by the QRX, not whether any data is available in * a kernel socket buffer. */ int ossl_qrx_unprocessed_read_pending(OSSL_QRX *qrx); /* * Returns the number of UDP payload bytes received from the network so far * since the last time this counter was cleared. If clear is 1, clears the * counter and returns the old value. * * The intended use of this is to allow callers to determine how much credit to * add to their anti-amplification budgets. This is reported separately instead * of in the OSSL_QRX_PKT structure so that a caller can apply * anti-amplification credit as soon as a datagram is received, before it has * necessarily read all processed packets contained within that datagram from * the QRX. */ uint64_t ossl_qrx_get_bytes_received(OSSL_QRX *qrx, int clear); /* * Sets a callback which is called when a packet is received and being validated * before being queued in the read queue. This is called after packet body * decryption and authentication to prevent exposing side channels. pn_space is * a QUIC_PN_SPACE_* value denoting which PN space the PN belongs to. * * If this callback returns 1, processing continues normally. * If this callback returns 0, the packet is discarded. * * Other packets in the same datagram will still be processed where possible. * * The callback is optional and can be unset by passing NULL for cb. * cb_arg is an opaque value passed to cb. */ typedef int (ossl_qrx_late_validation_cb)(QUIC_PN pn, int pn_space, void *arg); int ossl_qrx_set_late_validation_cb(OSSL_QRX *qrx, ossl_qrx_late_validation_cb *cb, void *cb_arg); /* * Forcibly injects a URXE which has been issued by the DEMUX into the QRX for * processing. This can be used to pass a received datagram to the QRX if it * would not be correctly routed to the QRX via standard DCID-based routing; for * example, when handling an incoming Initial packet which is attempting to * establish a new connection. */ void ossl_qrx_inject_urxe(OSSL_QRX *qrx, QUIC_URXE *e); /* * Decryption of 1-RTT packets must be explicitly enabled by calling this * function. This is to comply with the requirement that we not process 1-RTT * packets until the handshake is complete, even if we already have 1-RTT * secrets. Even if a 1-RTT secret is provisioned for the QRX, incoming 1-RTT * packets will be handled as though no key is available until this function is * called. Calling this function will then requeue any such deferred packets for * processing. */ void ossl_qrx_allow_1rtt_processing(OSSL_QRX *qrx); /* * Key Update (RX) * =============== * * Key update on the RX side is a largely but not entirely automatic process. * * Key update is initially triggered by receiving a 1-RTT packet with a * different Key Phase value. This could be caused by an attacker in the network * flipping random bits, therefore such a key update is tentative until the * packet payload is successfully decrypted and authenticated by the AEAD with * the 'next' keys. These 'next' keys then become the 'current' keys and the * 'current' keys then become the 'previous' keys. The 'previous' keys must be * kept around temporarily as some packets may still be in flight in the network * encrypted with the old keys. If the old Key Phase value is X and the new Key * Phase Value is Y (where obviously X != Y), this creates an ambiguity as any * new packet received with a KP of X could either be an attempt to initiate yet * another key update right after the last one, or an old packet encrypted * before the key update. * * RFC 9001 provides some guidance on handling this issue: * * Strategy 1: * Three keys, disambiguation using packet numbers * * "A recovered PN that is lower than any PN from the current KP uses the * previous packet protection keys; a recovered PN that is higher than any * PN from the current KP requires use of the next packet protection * keys." * * Strategy 2: * Two keys and a timer * * "Alternatively, endpoints can retain only two sets of packet protection * keys, swapping previous keys for next after enough time has passed to * allow for reordering in the network. In this case, the KP bit alone can * be used to select keys." * * Strategy 2 is more efficient (we can keep fewer cipher contexts around) and * should cover all actually possible network conditions. It also allows a delay * after we make the 'next' keys our 'current' keys before we generate new * 'next' keys, which allows us to mitigate against malicious peers who try to * initiate an excessive number of key updates. * * We therefore model the following state machine: * * * PROVISIONED * _______________________________ * | | * UNPROVISIONED --|----> NORMAL <----------\ |------> DISCARDED * | | | | * | | | | * | v | | * | UPDATING | | * | | | | * | | | | * | v | | * | COOLDOWN | | * | | | | * | | | | * | \---------------| | * |_______________________________| * * * The RX starts (once a secret has been provisioned) in the NORMAL state. In * the NORMAL state, the current expected value of the Key Phase bit is * recorded. When a flipped Key Phase bit is detected, the RX attempts to * decrypt and authenticate the received packet with the 'next' keys rather than * the 'current' keys. If (and only if) this authentication is successful, we * move to the UPDATING state. (An attacker in the network could flip * the Key Phase bit randomly, so it is essential we do nothing until AEAD * authentication is complete.) * * In the UPDATING state, we know a key update is occurring and record * the new Key Phase bit value as the newly current value, but we still keep the * old keys around so that we can still process any packets which were still in * flight when the key update was initiated. In the UPDATING state, a * Key Phase bit value different to the current expected value is treated not as * the initiation of another key update, but a reference to our old keys. * * Eventually we will be reasonably sure we are not going to receive any more * packets with the old keys. At this point, we can transition to the COOLDOWN * state. This transition occurs automatically after a certain amount of time; * RFC 9001 recommends it be the PTO interval, which relates to our RTT to the * peer. The duration also SHOULD NOT exceed three times the PTO to assist with * maintaining PFS. * * In the COOLDOWN phase, the old keys have been securely erased and only one * set of keys can be used: the current keys. If a packet is received with a Key * Phase bit value different to the current Key Phase Bit value, this is treated * as a request for a Key Update, but this request is ignored and the packet is * treated as malformed. We do this to allow mitigation against malicious peers * trying to initiate an excessive number of Key Updates. The timeout for the * transition from UPDATING to COOLDOWN is recommended as adequate for * this purpose in itself by the RFC, so the normal additional timeout value for * the transition from COOLDOWN to normal is zero (immediate transition). * * A summary of each state: * * Epoch Exp KP Uses Keys KS0 KS1 If Non-Expected KP Bit * ----- ------ --------- ------ ----- ---------------------- * NORMAL 0 0 Keyset 0 Gen 0 Gen 1 → UPDATING * UPDATING 1 1 Keyset 1 Gen 0 Gen 1 Use Keyset 0 * COOLDOWN 1 1 Keyset 1 Erased Gen 1 Ignore Packet (*) * * NORMAL 1 1 Keyset 1 Gen 2 Gen 1 → UPDATING * UPDATING 2 0 Keyset 0 Gen 2 Gen 1 Use Keyset 1 * COOLDOWN 2 0 Keyset 0 Gen 2 Erased Ignore Packet (*) * * (*) Actually implemented by attempting to decrypt the packet with the * wrong keys (which ultimately has the same outcome), as recommended * by RFC 9001 to avoid creating timing channels. * * Note that the key material for the next key generation ("key epoch") is * always kept in the NORMAL state (necessary to avoid side-channel attacks). * This material is derived during the transition from COOLDOWN to NORMAL. * * Note that when a peer initiates a Key Update, we MUST also initiate a Key * Update as per the RFC. The caller is responsible for detecting this condition * and making the necessary calls to the TX side by detecting changes to the * return value of ossl_qrx_get_key_epoch(). * * The above states (NORMAL, UPDATING, COOLDOWN) can themselves be * considered substates of the PROVISIONED state. Providing a secret to the QRX * for an EL transitions from UNPROVISIONED, the initial state, to PROVISIONED * (NORMAL). Dropping key material for an EL transitions from whatever the * current substate of the PROVISIONED state is to the DISCARDED state, which is * the terminal state. * * Note that non-1RTT ELs cannot undergo key update, therefore a non-1RTT EL is * always in the NORMAL substate if it is in the PROVISIONED state. */ /* * Return the current RX key epoch for the 1-RTT encryption level. This is * initially zero and is incremented by one for every Key Update successfully * signalled by the peer. If the 1-RTT EL has not yet been provisioned or has * been discarded, returns UINT64_MAX. * * A necessary implication of this API is that the least significant bit of the * returned value corresponds to the currently expected Key Phase bit, though * callers are not anticipated to have any need of this information. * * It is not possible for the returned value to overflow, as a QUIC connection * cannot support more than 2**62 packet numbers, and a connection must be * terminated if this limit is reached. * * The caller should use this function to detect when the key epoch has changed * and use it to initiate a key update on the TX side. * * The value returned by this function increments specifically at the transition * from the NORMAL to the UPDATING state discussed above. */ uint64_t ossl_qrx_get_key_epoch(OSSL_QRX *qrx); /* * Sets an optional callback which will be called when the key epoch changes. * * The callback is optional and can be unset by passing NULL for cb. * cb_arg is an opaque value passed to cb. pn is the PN of the packet. * Since key update is only supported for 1-RTT packets, the PN is always * in the Application Data PN space. */ typedef void (ossl_qrx_key_update_cb)(QUIC_PN pn, void *arg); int ossl_qrx_set_key_update_cb(OSSL_QRX *qrx, ossl_qrx_key_update_cb *cb, void *cb_arg); /* * Relates to the 1-RTT encryption level. The caller should call this after the * UPDATING state is reached, after a timeout to be determined by the caller. * * This transitions from the UPDATING state to the COOLDOWN state (if * still in the UPDATING state). If normal is 1, then transitions from * the COOLDOWN state to the NORMAL state. Both transitions can be performed at * once if desired. * * If in the normal state, or if in the COOLDOWN state and normal is 0, this is * a no-op and returns 1. Returns 0 if the 1-RTT EL has not been provisioned or * has been dropped. * * It is essential that the caller call this within a few PTO intervals of a key * update occurring (as detected by the caller in a call to * ossl_qrx_key_get_key_epoch()), as otherwise the peer will not be able to * perform a Key Update ever again. */ int ossl_qrx_key_update_timeout(OSSL_QRX *qrx, int normal); /* * Key Expiration * ============== */ /* * Returns the number of seemingly forged packets which have been received by * the QRX. If this value reaches the value returned by * ossl_qrx_get_max_epoch_forged_pkt_count() for a given EL, all further * received encrypted packets for that EL will be discarded without processing. * * Note that the forged packet limit is for the connection lifetime, thus it is * not reset by a key update. It is suggested that the caller terminate the * connection a reasonable margin before the limit is reached. However, the * exact limit imposed does vary by EL due to the possibility that different ELs * use different AEADs. */ uint64_t ossl_qrx_get_cur_forged_pkt_count(OSSL_QRX *qrx); /* * Returns the maximum number of forged packets which the record layer will * permit to be verified using this QRX instance. */ uint64_t ossl_qrx_get_max_forged_pkt_count(OSSL_QRX *qrx, uint32_t enc_level); # endif #endif