RFC 8967
MAC Authentication for the Babel Routing Protocol
Pages: ~17
Obsoletes: 7298
Updated by: 9467
IETF/rtg/babel/draft-ietf-babel-hmac-12
Proposed Standard
Obsoletes: 7298
Updated by: 9467
MAC Authentication for the Babel Routing Protocol
Abstract
This document describes a cryptographic authentication mechanism for the Babel routing protocol that has provisions for replay avoidance. This document obsoletes RFC 7298.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8967 .
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info ) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
1. Introduction
By default, the Babel routing protocol [RFC 8966] trusts the information contained in every UDP datagram that it receives on the Babel port. An attacker can redirect traffic to itself or to a different node in the network, causing a variety of potential issues. In particular, an attacker might:
- spoof a Babel packet and redirect traffic by announcing a route with a smaller metric, a larger sequence number, or a longer prefix;
- spoof a malformed packet, which could cause an insufficiently robust implementation to crash or interfere with the rest of the network;
- replay a previously captured Babel packet, which could cause traffic to be redirected or otherwise interfere with the network.
1.1. Applicability
The protocol defined in this document assumes that all interfaces on a given link are equally trusted and share a small set of symmetric keys (usually just one, and two during key rotation). The protocol is inapplicable in situations where asymmetric keying is required, where the trust relationship is partial, or where large numbers of trusted keys are provisioned on a single link at the same time.
This protocol supports incremental deployment (where an insecure Babel network is made secure with no service interruption), and it supports graceful key rotation (where the set of keys is changed with no service interruption).
This protocol does not require synchronised clocks, it does not require persistently monotonic clocks, and it does not require persistent storage except for what might be required for storing cryptographic keys.
1.2. Assumptions and Security Properties
The correctness of the protocol relies on the following assumptions:
- that the Message Authentication Code (MAC) being used is invulnerable to forgery, i.e., that an attacker is unable to generate a packet with a correct MAC without access to the secret key;
- that a node never generates the same index or nonce twice over the lifetime of a key.
- it is invulnerable to spoofing: any Babel packet accepted as authentic is the exact copy of a packet originally sent by an authorised node;
- locally to a single node, it is invulnerable to replay: if a node has previously accepted a given packet, then it will never again accept a copy of this packet or an earlier packet from the same sender;
- among different nodes, it is only vulnerable to immediate replay: if a node A has accepted an authentic packet from C, then a node B will only accept a copy of that packet if B has accepted an older packet from C, and B has received no later packet from C.
1.3. Specification of Requirements
2. Conceptual Overview of the Protocol
When a node B sends out a Babel packet through an interface that is configured for MAC cryptographic protection, it computes one or more MACs (one per key) that it appends to the packet. When a node A receives a packet over an interface that requires MAC cryptographic protection, it independently computes a set of MACs and compares them to the MACs appended to the packet; if there is no match, the packet is discarded.
In order to protect against replay, B maintains a per-interface 32-bit integer known as the "packet counter" (PC). Whenever B sends a packet through the interface, it embeds the current value of the PC within the region of the packet that is protected by the MACs and increases the PC by at least one. When A receives the packet, it compares the value of the PC with the one contained in the previous packet received from B, and unless it is strictly greater, the packet is discarded.
By itself, the PC mechanism is not sufficient to protect against replay. Consider a peer A that has no information about a peer B (e.g., because it has recently rebooted). Suppose that A receives a packet ostensibly from B carrying a given PC; since A has no information about B, it has no way to determine whether the packet is freshly generated or a replay of a previously sent packet.
In this situation, peer A discards the packet and challenges B to prove that it knows the MAC key. It sends a "Challenge Request", a TLV containing a unique nonce, a value that has never been used before and will never be used again. Peer B replies to the Challenge Request with a "Challenge Reply", a TLV containing a copy of the nonce chosen by A, in a packet protected by MAC and containing the new value of B's PC. Since the nonce has never been used before, B's reply proves B's knowledge of the MAC key and the freshness of the PC.
By itself, this mechanism is safe against replay if B never resets its PC. In practice, however, this is difficult to ensure, as persistent storage is prone to failure, and hardware clocks, even when available, are occasionally reset. Suppose that B resets its PC to an earlier value and sends a packet with a previously used PC n. Peer A challenges B, B successfully responds to the challenge, and A accepts the PC equal to n + 1. At this point, an attacker C may send a replayed packet with PC equal to n + 2, which will be accepted by A.
Another mechanism is needed to protect against this attack. In this protocol, every PC is tagged with an "index", an arbitrary string of octets. Whenever B resets its PC, or whenever B doesn't know whether its PC has been reset, it picks an index that it has never used before (either by drawing it randomly or by using a reliable hardware clock) and starts sending PCs with that index. Whenever A detects that B has changed its index, it challenges B again.
With this additional mechanism, this protocol is invulnerable to replay attacks (see Section 1.2).
3. Data Structures
Every Babel node maintains a set of conceptual data structures described in Section 3.2 of RFC 8966. This protocol extends these data structures as follows.
3.1. The Interface Table
Every Babel node maintains an interface table, as described in Section 3.2.3 of RFC 8966. Implementations of this protocol MUST allow each interface to be provisioned with a set of one or more MAC keys and the associated MAC algorithms (see Section 4.1 for suggested algorithms and Section 7 for suggested methods for key generation). In order to allow incremental deployment of this protocol (see Section 5), implementations SHOULD allow an interface to be configured in a mode in which it participates in the MAC authentication protocol but accepts packets that are not authenticated.
This protocol extends each table entry associated with an interface on which MAC authentication has been configured with two new pieces of data:
- a set of one or more MAC keys, each associated with a given MAC algorithm;
- a pair (Index, PC), where Index is an arbitrary string of 0 to 32 octets, and PC is a 32-bit (4-octet) integer.
3.2. The Neighbour Table
Every Babel node maintains a neighbour table, as described in Section 3.2.4 of RFC 8966. This protocol extends each entry in this table with two new pieces of data:
- a pair (Index, PC), where Index is a string of 0 to 32 octets, and PC is a 32-bit (4-octet) integer;
- a Nonce, which is an arbitrary string of 0 to 192 octets, and an associated challenge expiry timer.
4. Protocol Operation
4.1. MAC Computation
A Babel node computes the MAC of a Babel packet as follows.
First, the node builds a pseudo-header that will participate in MAC computation but will not be sent. If the packet is carried over IPv6, the pseudo-header has the following format:
If the packet is carried over IPv4, the pseudo-header has the following format:
Fields:
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Src address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Src port | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + + | Dest address | + + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Dest port | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Src address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Src port | Dest address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Dest port | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- Src address
- The source IP address of the packet.
- Src port
- The source UDP port number of the packet.
- Dest address
- The destination IP address of the packet.
- Src port
- The destination UDP port number of the packet.
4.2. Packet Transmission
A Babel node might delay actually sending TLVs by a small amount, in order to aggregate multiple TLVs in a single packet up to the interface MTU (Section 4 of RFC 8966). For an interface on which MAC protection is configured, the TLV aggregation logic MUST take into account the overhead due to PC TLVs (one in each packet) and MAC TLVs (one per configured key).
Before sending a packet, the following actions are performed:
-
a PC TLV containing the PC and Index associated with the outgoing interface MUST be appended to the packet body;
- the PC MUST be incremented by a strictly positive amount (typically just 1);
- if the PC overflows, a fresh index MUST be generated (as defined in Section 3.1);
- for each key configured on the interface, a MAC is computed as specified in Section 4.1 and stored in a MAC TLV that MUST be appended to the packet trailer (see Section 4.2 of RFC 8966).
4.3. Packet Reception
When a packet is received on an interface that is configured for MAC protection, the following steps are performed before the packet is passed to normal processing:
- First, the receiver checks whether the trailer of the received packet carries at least one MAC TLV; if not, the packet MUST be immediately dropped and processing stops. Then, for each key configured on the receiving interface, the receiver computes the MAC of the packet. It then compares every generated MAC against every MAC included in the packet; if there is at least one match, the packet passes the MAC test; if there is none, the packet MUST be silently dropped and processing stops at this point. In order to avoid memory exhaustion attacks, an entry in the neighbour table MUST NOT be created before the MAC test has passed successfully. The MAC of the packet MUST NOT be computed for each MAC TLV contained in the packet, but only once for each configured key.
- If an entry for the sender does not exist in the neighbour table, it MAY be created at this point (or, alternatively, its creation can be delayed until a challenge needs to be sent, see below).
- The packet body is then parsed a first time. During this "preparse" phase, the packet body is traversed and all TLVs are ignored except PC, Challenge Request, and Challenge Reply TLVs. When a PC TLV is encountered, the enclosed PC and Index are saved for later processing. If multiple PCs are found (which should not happen, see Section 4.2), only the first one is processed, the remaining ones MUST be silently ignored. If a Challenge Request is encountered, a Challenge Reply MUST be scheduled, as described in Section 4.3.1.2. If a Challenge Reply is encountered, it is tested for validity as described in Section 4.3.1.3, and a note is made of the result of the test.
- The preparse phase above yields two pieces of data: the PC and Index from the first PC TLV, and a bit indicating whether the packet contains a successful Challenge Reply. If the packet does not contain a PC TLV, the packet MUST be dropped, and processing stops at this point. If the packet contains a successful Challenge Reply, then the PC and Index contained in the PC TLV MUST be stored in the neighbour table entry corresponding to the sender (which already exists in this case), and the packet is accepted.
- Otherwise, if there is no entry in the neighbour table corresponding to the sender, or if such an entry exists but contains no Index, or if the Index it contains is different from the Index contained in the PC TLV, then a challenge MUST be sent as described in Section 4.3.1.1, the packet MUST be dropped, and processing stops at this stage.
- At this stage, the packet contains no successful Challenge Reply, and the Index contained in the PC TLV is equal to the Index in the neighbour table entry corresponding to the sender. The receiver compares the received PC with the PC contained in the neighbour table; if the received PC is smaller or equal than the PC contained in the neighbour table, the packet MUST be dropped and processing stops (no challenge is sent in this case, since the mismatch might be caused by harmless packet reordering on the link). Otherwise, the PC contained in the neighbour table entry is set to the received PC, and the packet is accepted.
4.3.1. Challenge Requests and Replies
During the preparse stage, the receiver might encounter a mismatched Index, to which it will react by scheduling a Challenge Request. It might encounter a Challenge Request TLV, to which it will reply with a Challenge Reply TLV. Finally, it might encounter a Challenge Reply TLV, which it will attempt to match with a previously sent Challenge Request TLV in order to update the neighbour table entry corresponding to the sender of the packet.
4.3.1.1. Sending Challenges
When it encounters a mismatched Index during the preparse phase, a node picks a nonce that it has never used with any of the keys currently configured on the relevant interface, for example, by drawing a sufficiently large random string of bytes or by consulting a strictly monotonic hardware clock. It MUST then store the nonce in the entry of the neighbour table associated to the neighbour (the entry might need to be created at this stage), initialise the neighbour's challenge expiry timer to 30 seconds, and send a Challenge Request TLV to the unicast address corresponding to the neighbour.
A node MAY aggregate a Challenge Request with other TLVs; in other words, if it has already buffered TLVs to be sent to the unicast address of the neighbour, it MAY send the buffered TLVs in the same packet as the Challenge Request. However, it MUST arrange for the Challenge Request to be sent in a timely manner, as any packets received from that neighbour will be silently ignored until the challenge completes.
A node MUST impose a rate limitation to the challenges it sends; the limit SHOULD default to one Challenge Request every 300 ms and MAY be configurable. This rate limiting serves two purposes. First, since a challenge may be sent in response to a packet replayed by an attacker, it limits the number of challenges that an attacker can cause a node to send. Second, it limits the number of challenges sent when there are multiple packets in flight from a single neighbour.
4.3.1.2. Replying to Challenges
When it encounters a Challenge Request during the preparse phase, a node constructs a Challenge Reply TLV by copying the Nonce from the Challenge Request into the Challenge Reply. It MUST then send the Challenge Reply to the unicast address from which the Challenge Request was sent. A challenge sent to a multicast address MUST be silently ignored.
A node MAY aggregate a Challenge Reply with other TLVs; in other words, if it has already buffered TLVs to be sent to the unicast address of the sender of the Challenge Request, it MAY send the buffered TLVs in the same packet as the Challenge Reply. However, it MUST arrange for the Challenge Reply to be sent in a timely manner (within a few seconds) and SHOULD NOT send any other packets over the same interface before sending the Challenge Reply, as those would be dropped by the challenger.
Since a Challenge Reply might be caused by a replayed Challenge Request, a node MUST impose a rate limitation to the Challenge Replies it sends; the limit SHOULD default to one Challenge Reply for each peer every 300 ms and MAY be configurable.
4.3.1.3. Receiving Challenge Replies
When it encounters a Challenge Reply during the preparse phase, a node consults the neighbour table entry corresponding to the neighbour that sent the Challenge Reply. If no challenge is in progress, i.e., if there is no Nonce stored in the neighbour table entry or the challenge timer has expired, the Challenge Reply MUST be silently ignored, and the challenge has failed.
Otherwise, the node compares the Nonce contained in the Challenge Reply with the Nonce contained in the neighbour table entry. If the two are equal (they have the same length and content), then the challenge has succeeded and the nonce stored in the neighbour table for this neighbour SHOULD be discarded; otherwise, the challenge has failed (and the nonce is not discarded).
4.4. Expiring Per-Neighbour State
The per-neighbour (Index, PC) pair is maintained in the neighbour table, and is normally discarded when the neighbour table entry expires. Implementations MUST ensure that an (Index, PC) pair is discarded within a finite time since the last time a packet has been accepted. In particular, unsuccessful challenges MUST NOT prevent an (Index, PC) pair from being discarded for unbounded periods of time.
A possible implementation strategy for implementations that use a Hello history (Appendix A of [RFC 8966]) is to discard the (Index, PC) pair whenever the Hello history becomes empty. Another implementation strategy is to use a timer that is reset whenever a packet is accepted and to discard the (Index, PC) pair whenever the timer expires. If the latter strategy is used, the timer SHOULD default to a value of 5 minutes and MAY be configurable.
5. Incremental Deployment and Key Rotation
In order to perform incremental deployment, the nodes in the network are first configured in a mode where packets are sent with authentication but not checked on reception. Once all the nodes in the network are configured to send authenticated packets, nodes are reconfigured to reject unauthenticated packets.
In order to perform key rotation, the new key is added to all the nodes. Once this is done, both the old and the new key are sent in all packets, and packets are accepted if they are properly signed by either of the keys. At that point, the old key is removed.
In order to support the procedures described above, implementations of this protocol SHOULD support an interface configuration in which packets are sent authenticated but received packets are accepted without verification, and they SHOULD allow changing the set of keys associated with an interface without a restart.
6. Packet Format
6.1. MAC TLV
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 16 | Length | MAC... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
- Type
- Set to 16 to indicate a MAC TLV.
- Length
- The length of the body, in octets, exclusive of theType and Length fields. The length depends on the MAC algorithm beingused.
- MAC
- The body contains the MAC of the packet, computed asdescribed in Section 4.1.
6.2. PC TLV
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 17 | Length | PC | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Index... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
- Type
- Set to 17 to indicate a PC TLV.
- Length
- The length of the body, in octets, exclusive of theType and Length fields.
- PC
- The Packet Counter (PC), a 32-bit (4-octet) unsignedinteger that is increased with every packet sent over this interface.A fresh index (as defined in Section 3.1) MUST begenerated whenever the PC overflows.
- Index
- The sender's Index, an opaque string of 0 to 32octets.
6.3. Challenge Request TLV
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 18 | Length | Nonce... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
- Type
- Set to 18 to indicate a Challenge Request TLV.
- Length
- The length of the body, in octets, exclusive of theType and Length fields.
- Nonce
- The nonce uniquely identifying the challenge, anopaque string of 0 to 192 octets.
6.4. Challenge Reply TLV
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 19 | Length | Nonce... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
- Type
- Set to 19 to indicate a Challenge Reply TLV.
- Length
- The length of the body, in octets, exclusive of theType and Length fields.
- Nonce
- A copy of the nonce contained in the correspondingChallenge Request.
7. Security Considerations
This document defines a mechanism that provides basic security properties for the Babel routing protocol. The scope of this protocol is strictly limited: it only provides authentication (we assume that routing information is not confidential), it only supports symmetric keying, and it only allows for the use of a small number of symmetric keys on every link. Deployments that need more features, e.g., confidentiality or asymmetric keying, should use a more feature-rich security mechanism such as the one described in [RFC 8968].
This mechanism relies on two assumptions, as described in Section 1.2. First, it assumes that the MAC being used is invulnerable to forgery (Section 1.1 of RFC 6039); at the time of writing, HMAC-SHA256, which is mandatory to implement (Section 4.1), is believed to be safe against practical attacks.
Second, it assumes that indices and nonces are generated uniquely over the lifetime of a key used for MAC computation (more precisely, indices must be unique for a given (key, source) pair, and nonces must be unique for a given (key, source, destination) triple). This property can be satisfied either by using a cryptographically secure random number generator to generate indices and nonces that contain enough entropy (64-bit values are believed to be large enough for all practical applications) or by using a reliably monotonic hardware clock. If uniqueness cannot be guaranteed (e.g., because a hardware clock has been reset), then rekeying is necessary.
The expiry mechanism mandated in Section 4.4 is required to prevent an attacker from delaying an authentic packet by an unbounded amount of time. If an attacker is able to delay the delivery of a packet (e.g., because it is located at a Layer 2 switch), then the packet will be accepted as long as the corresponding (Index, PC) pair is present at the receiver. If the attacker is able to cause the (Index, PC) pair to persist for arbitrary amounts of time (e.g., by repeatedly causing failed challenges), then it is able to delay the packet by arbitrary amounts of time, even after the sender has left the network, which could allow it to redirect or blackhole traffic to destinations previously advertised by the sender.
This protocol exposes large numbers of packets and their MACs to an attacker that is able to capture packets; it is therefore vulnerable to brute-force attacks. Keys must be chosen in a manner that makes them difficult to guess. Ideally, they should have a length of 32 octets (both for HMAC-SHA256 and BLAKE2s), and be chosen randomly. If, for some reason, it is necessary to derive keys from a human-readable passphrase, it is recommended to use a key derivation function that hampers dictionary attacks, such as PBKDF2 [RFC 8018], bcrypt [BCRYPT], or scrypt [RFC 7914]. In that case, only the derived keys should be communicated to the routers; the original passphrase itself should be kept on the host used to perform the key generation (e.g., an administrator's secure laptop computer).
While it is probably not possible to be immune against denial of service (DoS) attacks in general, this protocol includes a number of mechanisms designed to mitigate such attacks. In particular, reception of a packet with no correct MAC creates no local Babel state (Section 4.3). Reception of a replayed packet with correct MAC, on the other hand, causes a challenge to be sent; this is mitigated somewhat by requiring that challenges be rate limited (Section 4.3.1.1).
Receiving a replayed packet with an obsolete index causes an entry to be created in the neighbour table, which, at first sight, makes the protocol susceptible to resource exhaustion attacks (similarly to the familiar "TCP SYN Flooding" attack [RFC 4987]). However, the MAC computation includes the sender address (Section 4.1), and thus the amount of storage that an attacker can force a node to consume is limited by the number of distinct source addresses used with a single MAC key (see also Section 4 of RFC 8966, which mandates that the source address is a link-local IPv6 address or a local IPv4 address).
In order to make this kind of resource exhaustion attacks less effective, implementations may use a separate table of uncompleted challenges that is separate from the neighbour table used by the core protocol (the data structures described in Section 3.2 of RFC 8966 are conceptual, and any data structure that yields the same result may be used). Implementers might also consider using the fact that the nonces included in Challenge Requests and Replies can be fairly large (up to 192 octets), which should in principle allow encoding the per-challenge state as a secure "cookie" within the nonce itself; note, however, that any such scheme will need to prevent cookie replay.
8. IANA Considerations
IANA has allocated the following values in the Babel TLV Types registry:
Table 1
| Type | Name | Reference |
|---|---|---|
| 16 | MAC | RFC 8967 |
| 17 | PC | RFC 8967 |
| 18 | Challenge Request | RFC 8967 |
| 19 | Challenge Reply | RFC 8967 |
9. References
9.1. Normative References
- [RFC2104]
-
H. Krawczyk, M. Bellare, and R. Canetti, "HMAC: Keyed-Hashing for Message Authentication", RFC 2104, DOI 10.17487/RFC2104, February 1997,
<https://www.rfc-editor.org/info/ >.rfc2104 - [RFC2119]
-
S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/ >.rfc2119 - [RFC6234]
-
D. Eastlake 3rd, and T. Hansen, "US Secure Hash Algorithms (SHA and SHA-based HMAC and HKDF)", RFC 6234, DOI 10.17487/RFC6234, May 2011,
<https://www.rfc-editor.org/info/ >.rfc6234 - [RFC7693]
-
M-J. Saarinen, and J-P. Aumasson, "The BLAKE2 Cryptographic Hash and Message Authentication Code (MAC)", RFC 7693, DOI 10.17487/RFC7693, November 2015,
<https://www.rfc-editor.org/info/ >.rfc7693 - [RFC8174]
-
B. Leiba, "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017,
<https://www.rfc-editor.org/info/ >.rfc8174 - [RFC8966]
-
J. Chroboczek, and D. Schinazi, "The Babel Routing Protocol", RFC 8966, DOI 10.17487/RFC8966, January 2021,
<https://www.rfc-editor.org/info/ >.rfc8966
9.2. Informational References
- [BCRYPT]
- P. Niels, and D. Mazières, "A Future-Adaptable Password Scheme", June 1999.
- [RFC4086]
-
D. Eastlake 3rd, J. Schiller, and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, DOI 10.17487/RFC4086, June 2005,
<https://www.rfc-editor.org/info/ >.rfc4086 - [RFC4987]
-
W. Eddy, "TCP SYN Flooding Attacks and Common Mitigations", RFC 4987, DOI 10.17487/RFC4987, August 2007,
<https://www.rfc-editor.org/info/ >.rfc4987 - [RFC6039]
-
V. Manral, M. Bhatia, J. Jaeggli, and R. White, "Issues with Existing Cryptographic Protection Methods for Routing Protocols", RFC 6039, DOI 10.17487/RFC6039, October 2010,
<https://www.rfc-editor.org/info/ >.rfc6039 - [RFC7298]
-
D. Ovsienko, "Babel Hashed Message Authentication Code (HMAC) Cryptographic Authentication", RFC 7298, DOI 10.17487/RFC7298, July 2014,
<https://www.rfc-editor.org/info/ >.rfc7298 - [RFC7914]
-
C. Percival, and S. Josefsson, "The scrypt Password-Based Key Derivation Function", RFC 7914, DOI 10.17487/RFC7914, August 2016,
<https://www.rfc-editor.org/info/ >.rfc7914 - [RFC8018]
-
K. Moriarty, B. Kaliski, and A. Rusch, "PKCS #5: Password-Based Cryptography Specification Version 2.1", RFC 8018, DOI 10.17487/RFC8018, January 2017,
<https://www.rfc-editor.org/info/ >.rfc8018 - [RFC8968]
-
A Décimo, D Schinazi, and J Chroboczek, "Babel Routing Protocol over Datagram Transport Layer Security", RFC 8968, DOI 10.17487/RFC8968, January 2021,
<https://www.rfc-editor.org/info/ >.rfc8968
Acknowledgments
The protocol described in this document is based on the original HMAC protocol defined by Denis Ovsienko [RFC 7298]. The use of a pseudo-header was suggested by David Schinazi. The use of an index to avoid replay was suggested by Markus Stenberg. The authors are also indebted to Antonin Décimo, Donald Eastlake, Toke Høiland-Jørgensen, Florian Horn, Benjamin Kaduk, Dave Taht, and Martin Vigoureux.
Authors' Addresses
Clara Dô
IRIF, University of Paris-Diderot
Paris CEDEX 13 75205
France
Email: clarado_perso@yahoo.fr
Weronika Kolodziejak
IRIF, University of Paris-Diderot
Paris CEDEX 13 75205
France
Juliusz Chroboczek
IRIF, University of Paris-Diderot
Case 7014
Paris CEDEX 13 75205
France
Email: jch@irif.fr
