draft-ietf-quic-tls-14.txt   draft-ietf-quic-tls-latest.txt 
QUIC Working Group M. Thomson, Ed. QUIC Working Group M. Thomson, Ed.
Internet-Draft Mozilla Internet-Draft Mozilla
Intended status: Standards Track S. Turner, Ed. Intended status: Standards Track S. Turner, Ed.
Expires: February 16, 2019 sn3rd Expires: March 23, 2019 sn3rd
August 15, 2018 September 19, 2018
Using Transport Layer Security (TLS) to Secure QUIC Using Transport Layer Security (TLS) to Secure QUIC
draft-ietf-quic-tls-14 draft-ietf-quic-tls-latest
Abstract Abstract
This document describes how Transport Layer Security (TLS) is used to This document describes how Transport Layer Security (TLS) is used to
secure QUIC. secure QUIC.
Note to Readers Note to Readers
Discussion of this draft takes place on the QUIC working group Discussion of this draft takes place on the QUIC working group
mailing list (quic@ietf.org), which is archived at mailing list (quic@ietf.org), which is archived at
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 16, 2019. This Internet-Draft will expire on March 23, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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4.1.2. Encryption Level Changes . . . . . . . . . . . . . . 11 4.1.2. Encryption Level Changes . . . . . . . . . . . . . . 11
4.1.3. TLS Interface Summary . . . . . . . . . . . . . . . . 11 4.1.3. TLS Interface Summary . . . . . . . . . . . . . . . . 11
4.2. TLS Version . . . . . . . . . . . . . . . . . . . . . . . 12 4.2. TLS Version . . . . . . . . . . . . . . . . . . . . . . . 12
4.3. ClientHello Size . . . . . . . . . . . . . . . . . . . . 13 4.3. ClientHello Size . . . . . . . . . . . . . . . . . . . . 13
4.4. Peer Authentication . . . . . . . . . . . . . . . . . . . 13 4.4. Peer Authentication . . . . . . . . . . . . . . . . . . . 13
4.5. Enabling 0-RTT . . . . . . . . . . . . . . . . . . . . . 14 4.5. Enabling 0-RTT . . . . . . . . . . . . . . . . . . . . . 14
4.6. Rejecting 0-RTT . . . . . . . . . . . . . . . . . . . . . 14 4.6. Rejecting 0-RTT . . . . . . . . . . . . . . . . . . . . . 14
4.7. HelloRetryRequest . . . . . . . . . . . . . . . . . . . . 14 4.7. HelloRetryRequest . . . . . . . . . . . . . . . . . . . . 14
4.8. TLS Errors . . . . . . . . . . . . . . . . . . . . . . . 15 4.8. TLS Errors . . . . . . . . . . . . . . . . . . . . . . . 15
4.9. Discarding Unused Keys . . . . . . . . . . . . . . . . . 15 4.9. Discarding Unused Keys . . . . . . . . . . . . . . . . . 15
5. QUIC Packet Protection . . . . . . . . . . . . . . . . . . . 16 5. Packet Protection . . . . . . . . . . . . . . . . . . . . . . 16
5.1. QUIC Packet Encryption Keys . . . . . . . . . . . . . . . 16 5.1. Packet Protection Keys . . . . . . . . . . . . . . . . . 16
5.1.1. Initial Secrets . . . . . . . . . . . . . . . . . . . 17 5.2. Initial Secrets . . . . . . . . . . . . . . . . . . . . . 17
5.2. QUIC AEAD Usage . . . . . . . . . . . . . . . . . . . . . 17 5.3. AEAD Usage . . . . . . . . . . . . . . . . . . . . . . . 18
5.3. Packet Number Protection . . . . . . . . . . . . . . . . 18 5.4. Packet Number Protection . . . . . . . . . . . . . . . . 19
5.3.1. AES-Based Packet Number Protection . . . . . . . . . 20 5.4.1. AES-Based Packet Number Protection . . . . . . . . . 20
5.3.2. ChaCha20-Based Packet Number Protection . . . . . . . 20 5.4.2. ChaCha20-Based Packet Number Protection . . . . . . . 20
5.4. Receiving Protected Packets . . . . . . . . . . . . . . . 20 5.5. Receiving Protected Packets . . . . . . . . . . . . . . . 20
5.5. Use of 0-RTT Keys . . . . . . . . . . . . . . . . . . . . 21 5.6. Use of 0-RTT Keys . . . . . . . . . . . . . . . . . . . . 21
5.6. Receiving Out-of-Order Protected Frames . . . . . . . . . 21 5.7. Receiving Out-of-Order Protected Frames . . . . . . . . . 21
6. Key Update . . . . . . . . . . . . . . . . . . . . . . . . . 22 6. Key Update . . . . . . . . . . . . . . . . . . . . . . . . . 22
7. Security of Initial Messages . . . . . . . . . . . . . . . . 23 7. Security of Initial Messages . . . . . . . . . . . . . . . . 23
8. QUIC-Specific Additions to the TLS Handshake . . . . . . . . 24 8. QUIC-Specific Additions to the TLS Handshake . . . . . . . . 24
8.1. Protocol and Version Negotiation . . . . . . . . . . . . 24 8.1. Protocol and Version Negotiation . . . . . . . . . . . . 24
8.2. QUIC Transport Parameters Extension . . . . . . . . . . . 24 8.2. QUIC Transport Parameters Extension . . . . . . . . . . . 24
9. Security Considerations . . . . . . . . . . . . . . . . . . . 25 9. Security Considerations . . . . . . . . . . . . . . . . . . . 25
9.1. Packet Reflection Attack Mitigation . . . . . . . . . . . 25 9.1. Packet Reflection Attack Mitigation . . . . . . . . . . . 25
9.2. Peer Denial of Service . . . . . . . . . . . . . . . . . 25 9.2. Peer Denial of Service . . . . . . . . . . . . . . . . . 25
9.3. Packet Number Protection Analysis . . . . . . . . . . . . 26 9.3. Packet Number Protection Analysis . . . . . . . . . . . . 26
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(PSK) and Diffie-Hellman (DH) key exchanges. PSK is the basis for (PSK) and Diffie-Hellman (DH) key exchanges. PSK is the basis for
0-RTT; the latter provides perfect forward secrecy (PFS) when the DH 0-RTT; the latter provides perfect forward secrecy (PFS) when the DH
keys are destroyed. keys are destroyed.
After completing the TLS handshake, the client will have learned and After completing the TLS handshake, the client will have learned and
authenticated an identity for the server and the server is optionally authenticated an identity for the server and the server is optionally
able to learn and authenticate an identity for the client. TLS able to learn and authenticate an identity for the client. TLS
supports X.509 [RFC5280] certificate-based authentication for both supports X.509 [RFC5280] certificate-based authentication for both
server and client. server and client.
The TLS key exchange is resistent to tampering by attackers and it The TLS key exchange is resistant to tampering by attackers and it
produces shared secrets that cannot be controlled by either produces shared secrets that cannot be controlled by either
participating peer. participating peer.
TLS 1.3 provides two basic handshake modes of interest to QUIC: TLS 1.3 provides two basic handshake modes of interest to QUIC:
o A full 1-RTT handshake in which the client is able to send o A full 1-RTT handshake in which the client is able to send
application data after one round trip and the server immediately application data after one round trip and the server immediately
responds after receiving the first handshake message from the responds after receiving the first handshake message from the
client. client.
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o CRYPTO frames MAY appear in packets of any encryption level. o CRYPTO frames MAY appear in packets of any encryption level.
o CONNECTION_CLOSE MAY appear in packets of any encryption level o CONNECTION_CLOSE MAY appear in packets of any encryption level
other than 0-RTT. other than 0-RTT.
o PADDING and PING frames MAY appear in packets of any encryption o PADDING and PING frames MAY appear in packets of any encryption
level. level.
o ACK frames MAY appear in packets of any encryption level other o ACK frames MAY appear in packets of any encryption level other
than 0-RTT, but can only acknowledge packets which appeared in than 0-RTT, but can only acknowledge packets which appeared in
that encryption level. that packet number space.
o STREAM frames MUST ONLY appear in the 0-RTT and 1-RTT levels. o STREAM frames MUST ONLY appear in the 0-RTT and 1-RTT levels.
o All other frame types MUST only appear at the 1-RTT levels. o All other frame types MUST only appear at the 1-RTT levels.
Because packets could be reordered on the wire, QUIC uses the packet Because packets could be reordered on the wire, QUIC uses the packet
type to indicate which level a given packet was encrypted under, as type to indicate which level a given packet was encrypted under, as
shown in Table 1. When multiple packets of different encryption shown in Table 1. When multiple packets of different encryption
levels need to be sent, endpoints SHOULD use coalesced packets to levels need to be sent, endpoints SHOULD use coalesced packets to
send them in the same UDP datagram. send them in the same UDP datagram.
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acceptable provided that the features of TLS 1.3 that are used by acceptable provided that the features of TLS 1.3 that are used by
QUIC are supported by the newer version. QUIC are supported by the newer version.
A badly configured TLS implementation could negotiate TLS 1.2 or A badly configured TLS implementation could negotiate TLS 1.2 or
another older version of TLS. An endpoint MUST terminate the another older version of TLS. An endpoint MUST terminate the
connection if a version of TLS older than 1.3 is negotiated. connection if a version of TLS older than 1.3 is negotiated.
4.3. ClientHello Size 4.3. ClientHello Size
QUIC requires that the first Initial packet from a client contain an QUIC requires that the first Initial packet from a client contain an
entire crytographic handshake message, which for TLS is the entire cryptographic handshake message, which for TLS is the
ClientHello. Though a packet larger than 1200 octets might be ClientHello. Though a packet larger than 1200 octets might be
supported by the path, a client improves the likelihood that a packet supported by the path, a client improves the likelihood that a packet
is accepted if it ensures that the first ClientHello message is small is accepted if it ensures that the first ClientHello message is small
enough to stay within this limit. enough to stay within this limit.
QUIC packet and framing add at least 36 octets of overhead to the QUIC packet and framing add at least 36 octets of overhead to the
ClientHello message. That overhead increases if the client chooses a ClientHello message. That overhead increases if the client chooses a
connection ID without zero length. Overheads also do not include the connection ID without zero length. Overheads also do not include the
token or a connection ID longer than 8 octets, both of which might be token or a connection ID longer than 8 octets, both of which might be
required if a server sends a Retry packet. required if a server sends a Retry packet.
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generate alerts at the "warning" level. generate alerts at the "warning" level.
4.9. Discarding Unused Keys 4.9. Discarding Unused Keys
After QUIC moves to a new encryption level, packet protection keys After QUIC moves to a new encryption level, packet protection keys
for previous encryption levels can be discarded. This occurs several for previous encryption levels can be discarded. This occurs several
times during the handshake, as well as when keys are updated (see times during the handshake, as well as when keys are updated (see
Section 6). Section 6).
Packet protection keys are not discarded immediately when new keys Packet protection keys are not discarded immediately when new keys
are availble. If packets from a lower encryption level contain are available. If packets from a lower encryption level contain
CRYPTO frames, frames that retransmit that data MUST be sent at the CRYPTO frames, frames that retransmit that data MUST be sent at the
same encryption level. Similarly, an endpoint generates same encryption level. Similarly, an endpoint generates
acknowledgements for packets at the same encryption level as the acknowledgements for packets at the same encryption level as the
packet being acknowledged. Thus, it is possible that keys for a packet being acknowledged. Thus, it is possible that keys for a
lower encryption level are needed for a short time after keys for a lower encryption level are needed for a short time after keys for a
newer encryption level are available. newer encryption level are available.
An endpoint cannot discard keys for a given encryption level unless An endpoint cannot discard keys for a given encryption level unless
it has both received and acknowledged all CRYPTO frames for that it has both received and acknowledged all CRYPTO frames for that
encryption level and when all CRYPTO frames for that encryption level encryption level and when all CRYPTO frames for that encryption level
have been acknowledged by its peer. However, this does not guarantee have been acknowledged by its peer. However, this does not guarantee
that no further packets will need to be received or sent at that that no further packets will need to be received or sent at that
encryption level because a peer might not have received all the encryption level because a peer might not have received all the
acknowledgements necessary to reach the same state. acknowledgements necessary to reach the same state.
After all CRYPTO frames for a given encryption level have been sent After all CRYPTO frames for a given encryption level have been sent
and all expected CRYPTO frames received, and all the corresponding and all expected CRYPTO frames received, and all the corresponding
acknowledgments have been received or sent, an endpoint starts a acknowledgments have been received or sent, an endpoint starts a
timer. To limit the effect of packet loss around a change in keys, timer. To limit the effect of packet loss around a change in keys,
endpoints MUST retain packet protection keys for that encryption endpoints MUST retain packet protection keys for that encryption
level for at least three times the current Retramsmission Timeout level for at least three times the current Retransmission Timeout
(RTO) interval as defined in [QUIC-RECOVERY]. Retaining keys for (RTO) interval as defined in [QUIC-RECOVERY]. Retaining keys for
this interval allows packets containing CRYPTO or ACK frames at that this interval allows packets containing CRYPTO or ACK frames at that
encryption level to be sent if packets are determined to be lost or encryption level to be sent if packets are determined to be lost or
new packets require acknowledgment. new packets require acknowledgment.
Though an endpoint might retain older keys, new data MUST be sent at Though an endpoint might retain older keys, new data MUST be sent at
the highest currently-available encryption level. Only ACK frames the highest currently-available encryption level. Only ACK frames
and retransmissions of data in CRYPTO frames are sent at a previous and retransmissions of data in CRYPTO frames are sent at a previous
encryption level. These packets MAY also include PADDING frames. encryption level. These packets MAY also include PADDING frames.
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sent two updates prior will appear to use the same keys. After the sent two updates prior will appear to use the same keys. After the
handshake is complete, endpoints only need to maintain the two latest handshake is complete, endpoints only need to maintain the two latest
sets of packet protection keys and MAY discard older keys. Updating sets of packet protection keys and MAY discard older keys. Updating
keys multiple times rapidly can cause packets to be effectively lost keys multiple times rapidly can cause packets to be effectively lost
if packets are significantly delayed. Because key updates can only if packets are significantly delayed. Because key updates can only
be performed once per round trip time, only packets that are delayed be performed once per round trip time, only packets that are delayed
by more than a round trip will be lost as a result of changing keys; by more than a round trip will be lost as a result of changing keys;
such packets will be marked as lost before this, as they leave a gap such packets will be marked as lost before this, as they leave a gap
in the sequence of packet numbers. in the sequence of packet numbers.
5. QUIC Packet Protection 5. Packet Protection
As with TLS over TCP, QUIC encrypts packets with keys derived from As with TLS over TCP, QUIC protects packets with keys derived from
the TLS handshake, using the AEAD algorithm negotiated by TLS. the TLS handshake, using the AEAD algorithm negotiated by TLS.
5.1. QUIC Packet Encryption Keys 5.1. Packet Protection Keys
QUIC derives packet encryption keys in the same way as TLS 1.3: Each QUIC derives packet protection keys in the same way that TLS derives
encryption level/direction pair has a secret value, which is then record protection keys.
used to derive the traffic keys using as described in Section 7.3 of
[TLS13]
The keys for the Initial encryption level are computed based on the Each encryption level has separate secret values for protection of
client's initial Destination Connection ID, as described in packets sent in each direction. These traffic secrets are derived by
Section 5.1.1. TLS (see Section 7.1 of [TLS13]) and are used by QUIC for all
encryption levels except the Initial encryption level. The secrets
for the Initial encryption level are computed based on the client's
initial Destination Connection ID, as described in Section 5.2.
The keys for other encryption levels are computed in the same fashion The keys used for packet protection are computed from the TLS secrets
as the corresponding TLS keys (see Section 7 of [TLS13]), except that using the method described in Section 7.3 of [TLS13]), except that
the label for HKDF-Expand-Label uses the prefix "quic " rather than the label for HKDF-Expand-Label uses the prefix "quic " rather than
"tls13 ". A different label provides key separation between TLS and "tls13 ". A different label provides key separation between TLS and
QUIC. QUIC.
5.1.1. Initial Secrets For example, where TLS might use a label of
0x002009746c733133206b657900 to derive a key, QUIC uses
0x00200871756963206b657900.
The HKDF-Expand-Label function with a "quic " label is also used to
derive the initial secrets (see Section 5.2) and to derive a packet
number protection key (the "pn" label, see Section 5.4).
5.2. Initial Secrets
Initial packets are protected with a secret derived from the Initial packets are protected with a secret derived from the
Destination Connection ID field from the client's first Initial Destination Connection ID field from the client's first Initial
packet of the connection. Specifically: packet of the connection. Specifically:
initial_salt = 0x9c108f98520a5c5c32968e950e8a2c5fe06d6c38 initial_salt = 0x9c108f98520a5c5c32968e950e8a2c5fe06d6c38
initial_secret = HKDF-Extract(initial_salt, initial_secret = HKDF-Extract(initial_salt,
client_dst_connection_id) client_dst_connection_id)
client_initial_secret = HKDF-Expand-Label(initial_secret, client_initial_secret = HKDF-Expand-Label(initial_secret,
"client in", "", "client in", "",
Hash.length) Hash.length)
server_initial_secret = HKDF-Expand-Label(initial_secret, server_initial_secret = HKDF-Expand-Label(initial_secret,
"server in", "", "server in", "",
Hash.length) Hash.length)
Note that if the server sends a Retry, the client's Initial will
correspond to a new connection and thus use the server provided
Destination Connection ID.
The hash function for HKDF when deriving initial secrets and keys is The hash function for HKDF when deriving initial secrets and keys is
SHA-256 [SHA]. The connection ID used with HKDF-Expand-Label is the SHA-256 [SHA].
initial Destination Connection ID.
The connection ID used with HKDF-Expand-Label is the Destination
Connection ID in the Initial packet sent by the client. This will be
a randomly-selected value unless the client creates the Initial
packet after reciving a Retry packet, where the Destination
Connection ID is selected by the server.
The value of initial_salt is a 20 octet sequence shown in the figure The value of initial_salt is a 20 octet sequence shown in the figure
in hexadecimal notation. Future versions of QUIC SHOULD generate a in hexadecimal notation. Future versions of QUIC SHOULD generate a
new salt value, thus ensuring that the keys are different for each new salt value, thus ensuring that the keys are different for each
version of QUIC. This prevents a middlebox that only recognizes one version of QUIC. This prevents a middlebox that only recognizes one
version of QUIC from seeing or modifying the contents of handshake version of QUIC from seeing or modifying the contents of handshake
packets from future versions. packets from future versions.
Note: The Destination Connection ID is of arbitrary length, and it Note: The Destination Connection ID is of arbitrary length, and it
could be zero length if the server sends a Retry packet with a could be zero length if the server sends a Retry packet with a
zero-length Source Connection ID field. In this case, the Initial zero-length Source Connection ID field. In this case, the Initial
keys provide no assurance to the client that the server received keys provide no assurance to the client that the server received
its packet; the client has to rely on the exchange that included its packet; the client has to rely on the exchange that included
the Retry packet for that property. the Retry packet for that property.
5.2. QUIC AEAD Usage 5.3. AEAD Usage
The Authentication Encryption with Associated Data (AEAD) [AEAD] The Authentication Encryption with Associated Data (AEAD) [AEAD]
function used for QUIC packet protection is the AEAD that is function used for QUIC packet protection is the AEAD that is
negotiated for use with the TLS connection. For example, if TLS is negotiated for use with the TLS connection. For example, if TLS is
using the TLS_AES_128_GCM_SHA256, the AEAD_AES_128_GCM function is using the TLS_AES_128_GCM_SHA256, the AEAD_AES_128_GCM function is
used. used.
QUIC packets are protected prior to applying packet number encryption QUIC packets are protected prior to applying packet number protection
(Section 5.3). The unprotected packet number is part of the (Section 5.4). The unprotected packet number is part of the
associated data (A). When removing packet protection, an endpoint associated data (A). When removing packet protection, an endpoint
first removes the protection from the packet number. first removes the protection from the packet number.
All QUIC packets other than Version Negotiation and Retry packets are All QUIC packets other than Version Negotiation and Retry packets are
protected with an AEAD algorithm [AEAD]. Prior to establishing a protected with an AEAD algorithm [AEAD]. Prior to establishing a
shared secret, packets are protected with AEAD_AES_128_GCM and a key shared secret, packets are protected with AEAD_AES_128_GCM and a key
derived from the destination connection ID in the client's first derived from the destination connection ID in the client's first
Initial packet (see Section 5.1.1). This provides protection against Initial packet (see Section 5.2). This provides protection against
off-path attackers and robustness against QUIC version unaware off-path attackers and robustness against QUIC version unaware
middleboxes, but not against on-path attackers. middleboxes, but not against on-path attackers.
All ciphersuites currently defined for TLS 1.3 - and therefore QUIC - All ciphersuites currently defined for TLS 1.3 - and therefore QUIC -
have a 16-byte authentication tag and produce an output 16 bytes have a 16-byte authentication tag and produce an output 16 bytes
larger than their input. larger than their input.
The key and IV for the packet are computed as described in The key and IV for the packet are computed as described in
Section 5.1. The nonce, N, is formed by combining the packet Section 5.1. The nonce, N, is formed by combining the packet
protection IV with the packet number. The 64 bits of the protection IV with the packet number. The 64 bits of the
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following the header, as described in [QUIC-TRANSPORT]. following the header, as described in [QUIC-TRANSPORT].
The output ciphertext, C, of the AEAD is transmitted in place of P. The output ciphertext, C, of the AEAD is transmitted in place of P.
Some AEAD functions have limits for how many packets can be encrypted Some AEAD functions have limits for how many packets can be encrypted
under the same key and IV (see for example [AEBounds]). This might under the same key and IV (see for example [AEBounds]). This might
be lower than the packet number limit. An endpoint MUST initiate a be lower than the packet number limit. An endpoint MUST initiate a
key update (Section 6) prior to exceeding any limit set for the AEAD key update (Section 6) prior to exceeding any limit set for the AEAD
that is in use. that is in use.
5.3. Packet Number Protection 5.4. Packet Number Protection
QUIC packet numbers are protected using a key that is derived from QUIC packet numbers are protected using a key that is derived from
the current set of secrets. The key derived using the "pn" label is the current set of secrets. The key derived using the "pn" label is
used to protect the packet number from casual observation. The used to protect the packet number from casual observation. The
packet number protection algorithm depends on the negotiated AEAD. packet number protection algorithm depends on the negotiated AEAD.
Packet number protection is applied after packet protection is Packet number protection is applied after packet protection is
applied (see Section 5.2). The ciphertext of the packet is sampled applied (see Section 5.3). The ciphertext of the packet is sampled
and used as input to an encryption algorithm. and used as input to an encryption algorithm.
In sampling the packet ciphertext, the packet number length is In sampling the packet ciphertext, the packet number length is
assumed to be 4 octets (its maximum possible encoded length), unless assumed to be 4 octets (its maximum possible encoded length), unless
there is insufficient space in the packet for sampling. The sampled there is insufficient space in the packet for sampling. The sampled
ciphertext starts after allowing for a 4 octet packet number unless ciphertext starts after allowing for a 4 octet packet number unless
this would cause the sample to extend past the end of the packet. If this would cause the sample to extend past the end of the packet. If
the sample would extend past the end of the packet, the end of the the sample would extend past the end of the packet, the end of the
packet is sampled. packet is sampled.
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the packet number is stored in the first octet of the encoded packet the packet number is stored in the first octet of the encoded packet
number, it may be necessary to progressively decrypt the packet number, it may be necessary to progressively decrypt the packet
number. number.
Before a TLS ciphersuite can be used with QUIC, a packet protection Before a TLS ciphersuite can be used with QUIC, a packet protection
algorithm MUST be specifed for the AEAD used with that ciphersuite. algorithm MUST be specifed for the AEAD used with that ciphersuite.
This document defines algorithms for AEAD_AES_128_GCM, This document defines algorithms for AEAD_AES_128_GCM,
AEAD_AES_128_CCM, AEAD_AES_256_GCM, AEAD_AES_256_CCM (all AES AEADs AEAD_AES_128_CCM, AEAD_AES_256_GCM, AEAD_AES_256_CCM (all AES AEADs
are defined in [AEAD]), and AEAD_CHACHA20_POLY1305 ([CHACHA]). are defined in [AEAD]), and AEAD_CHACHA20_POLY1305 ([CHACHA]).
5.3.1. AES-Based Packet Number Protection 5.4.1. AES-Based Packet Number Protection
This section defines the packet protection algorithm for This section defines the packet protection algorithm for
AEAD_AES_128_GCM, AEAD_AES_128_CCM, AEAD_AES_256_GCM, and AEAD_AES_128_GCM, AEAD_AES_128_CCM, AEAD_AES_256_GCM, and
AEAD_AES_256_CCM. AEAD_AES_128_GCM and AEAD_AES_128_CCM use 128-bit AEAD_AES_256_CCM. AEAD_AES_128_GCM and AEAD_AES_128_CCM use 128-bit
AES [AES] in counter (CTR) mode. AEAD_AES_256_GCM, and AES [AES] in counter (CTR) mode. AEAD_AES_256_GCM, and
AEAD_AES_256_CCM use 256-bit AES in CTR mode. AEAD_AES_256_CCM use 256-bit AES in CTR mode.
This algorithm samples 16 octets from the packet ciphertext. This This algorithm samples 16 octets from the packet ciphertext. This
value is used as the counter input to AES-CTR. value is used as the counter input to AES-CTR.
encrypted_pn = AES-CTR(pn_key, sample, packet_number) encrypted_pn = AES-CTR(pn_key, sample, packet_number)
5.3.2. ChaCha20-Based Packet Number Protection 5.4.2. ChaCha20-Based Packet Number Protection
When AEAD_CHACHA20_POLY1305 is in use, packet number protection uses When AEAD_CHACHA20_POLY1305 is in use, packet number protection uses
the raw ChaCha20 function as defined in Section 2.4 of [CHACHA]. the raw ChaCha20 function as defined in Section 2.4 of [CHACHA].
This uses a 256-bit key and 16 octets sampled from the packet This uses a 256-bit key and 16 octets sampled from the packet
protection output. protection output.
The first 4 octets of the sampled ciphertext are interpreted as a The first 4 octets of the sampled ciphertext are interpreted as a
32-bit number in little-endian order and are used as the block count. 32-bit number in little-endian order and are used as the block count.
The remaining 12 octets are interpreted as three concatenated 32-bit The remaining 12 octets are interpreted as three concatenated 32-bit
numbers in little-endian order and used as the nonce. numbers in little-endian order and used as the nonce.
The encoded packet number is then encrypted with ChaCha20 directly. The encoded packet number is then encrypted with ChaCha20 directly.
In pseudocode: In pseudocode:
counter = DecodeLE(sample[0..3]) counter = DecodeLE(sample[0..3])
nonce = DecodeLE(sample[4..7], sample[8..11], sample[12..15]) nonce = DecodeLE(sample[4..7], sample[8..11], sample[12..15])
encrypted_pn = ChaCha20(pn_key, counter, nonce, packet_number) encrypted_pn = ChaCha20(pn_key, counter, nonce, packet_number)
5.4. Receiving Protected Packets 5.5. Receiving Protected Packets
Once an endpoint successfully receives a packet with a given packet Once an endpoint successfully receives a packet with a given packet
number, it MUST discard all packets in the same packet number space number, it MUST discard all packets in the same packet number space
with higher packet numbers if they cannot be successfully unprotected with higher packet numbers if they cannot be successfully unprotected
with either the same key, or - if there is a key update - the next with either the same key, or - if there is a key update - the next
packet protection key (see Section 6). Similarly, a packet that packet protection key (see Section 6). Similarly, a packet that
appears to trigger a key update, but cannot be unprotected appears to trigger a key update, but cannot be unprotected
successfully MUST be discarded. successfully MUST be discarded.
Failure to unprotect a packet does not necessarily indicate the Failure to unprotect a packet does not necessarily indicate the
existence of a protocol error in a peer or an attack. The truncated existence of a protocol error in a peer or an attack. The truncated
packet number encoding used in QUIC can cause packet numbers to be packet number encoding used in QUIC can cause packet numbers to be
decoded incorrectly if they are delayed significantly. decoded incorrectly if they are delayed significantly.
5.5. Use of 0-RTT Keys 5.6. Use of 0-RTT Keys
If 0-RTT keys are available (see Section 4.5), the lack of replay If 0-RTT keys are available (see Section 4.5), the lack of replay
protection means that restrictions on their use are necessary to protection means that restrictions on their use are necessary to
avoid replay attacks on the protocol. avoid replay attacks on the protocol.
A client MUST only use 0-RTT keys to protect data that is idempotent. A client MUST only use 0-RTT keys to protect data that is idempotent.
A client MAY wish to apply additional restrictions on what data it A client MAY wish to apply additional restrictions on what data it
sends prior to the completion of the TLS handshake. A client sends prior to the completion of the TLS handshake. A client
otherwise treats 0-RTT keys as equivalent to 1-RTT keys, except that otherwise treats 0-RTT keys as equivalent to 1-RTT keys, except that
it MUST NOT send ACKs with 0-RTT keys. it MUST NOT send ACKs with 0-RTT keys.
A client that receives an indication that its 0-RTT data has been A client that receives an indication that its 0-RTT data has been
accepted by a server can send 0-RTT data until it receives all of the accepted by a server can send 0-RTT data until it receives all of the
server's handshake messages. A client SHOULD stop sending 0-RTT data server's handshake messages. A client SHOULD stop sending 0-RTT data
if it receives an indication that 0-RTT data has been rejected. if it receives an indication that 0-RTT data has been rejected.
A server MUST NOT use 0-RTT keys to protect packets; it uses 1-RTT A server MUST NOT use 0-RTT keys to protect packets; it uses 1-RTT
keys to protect acknowledgements of 0-RTT packets. Clients MUST NOT keys to protect acknowledgements of 0-RTT packets. A client MUST NOT
attempt to decrypt 0-RTT packets it receives and instead MUST discard attempt to decrypt 0-RTT packets it receives and instead MUST discard
them. them.
Note: 0-RTT data can be acknowledged by the server as it receives Note: 0-RTT data can be acknowledged by the server as it receives
it, but any packets containing acknowledgments of 0-RTT data it, but any packets containing acknowledgments of 0-RTT data
cannot have packet protection removed by the client until the TLS cannot have packet protection removed by the client until the TLS
handshake is complete. The 1-RTT keys necessary to remove packet handshake is complete. The 1-RTT keys necessary to remove packet
protection cannot be derived until the client receives all server protection cannot be derived until the client receives all server
handshake messages. handshake messages.
5.6. Receiving Out-of-Order Protected Frames 5.7. Receiving Out-of-Order Protected Frames
Due to reordering and loss, protected packets might be received by an Due to reordering and loss, protected packets might be received by an
endpoint before the final TLS handshake messages are received. A endpoint before the final TLS handshake messages are received. A
client will be unable to decrypt 1-RTT packets from the server, client will be unable to decrypt 1-RTT packets from the server,
whereas a server will be able to decrypt 1-RTT packets from the whereas a server will be able to decrypt 1-RTT packets from the
client. client.
However, a server MUST NOT process data from incoming 1-RTT protected However, a server MUST NOT process data from incoming 1-RTT protected
packets before verifying either the client Finished message or - in packets before verifying either the client Finished message or - in
the case that the server has chosen to use a pre-shared key - the the case that the server has chosen to use a pre-shared key - the
skipping to change at page 22, line 15 skipping to change at page 22, line 17
A server could receive packets protected with 0-RTT keys prior to A server could receive packets protected with 0-RTT keys prior to
receiving a TLS ClientHello. The server MAY retain these packets for receiving a TLS ClientHello. The server MAY retain these packets for
later decryption in anticipation of receiving a ClientHello. later decryption in anticipation of receiving a ClientHello.
6. Key Update 6. Key Update
Once the 1-RTT keys are established and the short header is in use, Once the 1-RTT keys are established and the short header is in use,
it is possible to update the keys. The KEY_PHASE bit in the short it is possible to update the keys. The KEY_PHASE bit in the short
header is used to indicate whether key updates have occurred. The header is used to indicate whether key updates have occurred. The
KEY_PHASE bit is initially set to 0 and then inverted with each key KEY_PHASE bit is initially set to 0 and then inverted with each key
update Section 6. update.
The KEY_PHASE bit allows a recipient to detect a change in keying The KEY_PHASE bit allows a recipient to detect a change in keying
material without necessarily needing to receive the first packet that material without necessarily needing to receive the first packet that
triggered the change. An endpoint that notices a changed KEY_PHASE triggered the change. An endpoint that notices a changed KEY_PHASE
bit can update keys and decrypt the packet that contains the changed bit can update keys and decrypt the packet that contains the changed
bit, see Section 6. bit.
An endpoint MUST NOT initiate more than one key update at a time. A An endpoint MUST NOT initiate more than one key update at a time. A
new key cannot be used until the endpoint has received and new key cannot be used until the endpoint has received and
successfully decrypted a packet with a matching KEY_PHASE. successfully decrypted a packet with a matching KEY_PHASE.
A receiving endpoint detects an update when the KEY_PHASE bit doesn't A receiving endpoint detects an update when the KEY_PHASE bit doesn't
match what it is expecting. It creates a new secret (see Section 7.2 match what it is expecting. It creates a new secret (see Section 7.2
of [TLS13]) and the corresponding read key and IV. If the packet can of [TLS13]) and the corresponding read key and IV. If the packet can
be decrypted and authenticated using these values, then the keys it be decrypted and authenticated using these values, then the keys it
uses for packet protection are also updated. The next packet sent by uses for packet protection are also updated. The next packet sent by
skipping to change at page 25, line 46 skipping to change at page 25, line 46
containing a ClientHello MUST be padded to a minimum size. Second, containing a ClientHello MUST be padded to a minimum size. Second,
if responding to an unverified source address, the server is if responding to an unverified source address, the server is
forbidden to send more than three UDP datagrams in its first flight forbidden to send more than three UDP datagrams in its first flight
(see Section 4.7 of [QUIC-TRANSPORT]). Finally, because (see Section 4.7 of [QUIC-TRANSPORT]). Finally, because
acknowledgements of Handshake packets are authenticated, a blind acknowledgements of Handshake packets are authenticated, a blind
attacker cannot forge them. Put together, these defenses limit the attacker cannot forge them. Put together, these defenses limit the
level of amplification. level of amplification.
9.2. Peer Denial of Service 9.2. Peer Denial of Service
QUIC, TLS and HTTP/2 all contain a messages that have legitimate uses QUIC, TLS, and HTTP/2 all contain messages that have legitimate uses
in some contexts, but that can be abused to cause a peer to expend in some contexts, but that can be abused to cause a peer to expend
processing resources without having any observable impact on the processing resources without having any observable impact on the
state of the connection. If processing is disproportionately large state of the connection. If processing is disproportionately large
in comparison to the observable effects on bandwidth or state, then in comparison to the observable effects on bandwidth or state, then
this could allow a malicious peer to exhaust processing capacity this could allow a malicious peer to exhaust processing capacity
without consequence. without consequence.
QUIC prohibits the sending of empty "STREAM" frames unless they are QUIC prohibits the sending of empty "STREAM" frames unless they are
marked with the FIN bit. This prevents "STREAM" frames from being marked with the FIN bit. This prevents "STREAM" frames from being
sent that only waste effort. sent that only waste effort.
skipping to change at page 27, line 41 skipping to change at page 27, line 41
[AES] "Advanced encryption standard (AES)", National Institute [AES] "Advanced encryption standard (AES)", National Institute
of Standards and Technology report, of Standards and Technology report,
DOI 10.6028/nist.fips.197, November 2001. DOI 10.6028/nist.fips.197, November 2001.
[CHACHA] Nir, Y. and A. Langley, "ChaCha20 and Poly1305 for IETF [CHACHA] Nir, Y. and A. Langley, "ChaCha20 and Poly1305 for IETF
Protocols", RFC 8439, DOI 10.17487/RFC8439, June 2018, Protocols", RFC 8439, DOI 10.17487/RFC8439, June 2018,
<https://www.rfc-editor.org/info/rfc8439>. <https://www.rfc-editor.org/info/rfc8439>.
[QUIC-RECOVERY] [QUIC-RECOVERY]
Iyengar, J., Ed. and I. Swett, Ed., "QUIC Loss Detection Iyengar, J., Ed. and I. Swett, Ed., "QUIC Loss Detection
and Congestion Control", draft-ietf-quic-recovery-14 (work and Congestion Control", draft-ietf-quic-recovery-latest
in progress). (work in progress).
[QUIC-TRANSPORT] [QUIC-TRANSPORT]
Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", draft-ietf-quic- Multiplexed and Secure Transport", draft-ietf-quic-
transport-14 (work in progress). transport-latest (work in progress).
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan, [RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol "Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301, Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <https://www.rfc-editor.org/info/rfc7301>. July 2014, <https://www.rfc-editor.org/info/rfc7301>.
skipping to change at page 28, line 46 skipping to change at page 28, line 46
Luykx, A. and K. Paterson, "Limits on Authenticated Luykx, A. and K. Paterson, "Limits on Authenticated
Encryption Use in TLS", March 2016, Encryption Use in TLS", March 2016,
<http://www.isg.rhul.ac.uk/~kp/TLS-AEbounds.pdf>. <http://www.isg.rhul.ac.uk/~kp/TLS-AEbounds.pdf>.
[IMC] Katz, J. and Y. Lindell, "Introduction to Modern [IMC] Katz, J. and Y. Lindell, "Introduction to Modern
Cryptography, Second Edition", ISBN 978-1466570269, Cryptography, Second Edition", ISBN 978-1466570269,
November 2014. November 2014.
[QUIC-HTTP] [QUIC-HTTP]
Bishop, M., Ed., "Hypertext Transfer Protocol (HTTP) over Bishop, M., Ed., "Hypertext Transfer Protocol (HTTP) over
QUIC", draft-ietf-quic-http-14 (work in progress). QUIC", draft-ietf-quic-http-latest (work in progress).
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000, DOI 10.17487/RFC2818, May 2000,
<https://www.rfc-editor.org/info/rfc2818>. <https://www.rfc-editor.org/info/rfc2818>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>. <https://www.rfc-editor.org/info/rfc5280>.
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