rfc9891v2.txt		rfc9891.txt
	skipping to change at line 187 ¶		skipping to change at line 187 ¶
	individual entity or across a network.		individual entity or across a network.
	* Policies or mechanisms for an ACME server to handle mixed-use		* Policies or mechanisms for an ACME server to handle mixed-use
	certificate signing requests. This specification is focused only		certificate signing requests. This specification is focused only
	on single-use DTN-specific PKIX profiles.		on single-use DTN-specific PKIX profiles.
	1.2. Authorization Strategy		1.2. Authorization Strategy
	The basic unit of data exchange in a DTN is a Bundle [RFC9171], which		The basic unit of data exchange in a DTN is a Bundle [RFC9171], which
	consists of a data payload with accompanying metadata. An EID is		consists of a data payload with accompanying metadata. An EID is
	used as the destination of a Bundle and can indicate both a singleton		used as the destination of a Bundle and can indicate either a
	or a group destination. A Node ID is used to identify the source of		singleton or a group destination. A Node ID is used to identify the
	a Bundle and is used for routing through intermediate nodes,		source of a Bundle and is used for routing through intermediate
	including the final node(s) used to deliver a Bundle to its		nodes, including the final node(s) used to deliver a Bundle to its
	destination endpoint. A Node ID can also be used as an endpoint for		destination endpoint. A Node ID can also be used as an endpoint for
	administrative Bundles. More detailed descriptions of the rationale		Bundles conveying administrative records as explained in Section 6 of
	and capabilities of these networks can be found in the		[RFC9171]. More detailed descriptions of the rationale and
	"Delay-Tolerant Networking Architecture" [RFC4838].		capabilities of these networks can be found in the "Delay-Tolerant
			Networking Architecture" [RFC4838].
	When an ACME client requests a pre-authorization or an order with an		When an ACME client requests a pre-authorization or an order with an
	identifier type "bundleEID" (Section 2), the ACME server offers a		identifier type "bundleEID" (Section 2), the ACME server offers a
	"bp-nodeid-00" challenge type (Section 3) to validate that Node ID.		"bp-nodeid-00" challenge type (Section 3) to validate that Node ID.
	If the ACME client attempts the authorization challenge to validate a		If the ACME client attempts the authorization challenge to validate a
	Node ID, the ACME server sends an ACME Node ID Validation Challenge		Node ID, the ACME server sends an ACME Node ID Validation Challenge
	Bundle with a destination of the Node ID being validated. The BP		Bundle with a destination of the Node ID being validated. The BP
	Agent on that node receives the Challenge Bundle, generates an ACME		Agent on that node receives the Challenge Bundle, generates an ACME
	Key Authorization digest, and sends an ACME Node ID Validation		Key Authorization digest, and sends an ACME Node ID Validation
	Response Bundle in reply. An Integrity Gateway on the client side of		Response Bundle in reply. An Integrity Gateway on the client side of
	skipping to change at line 266 ¶		skipping to change at line 267 ¶
	[RFC8610]. The entire CDDL structure can be extracted from the XML		[RFC8610]. The entire CDDL structure can be extracted from the XML
	version of this document using the XPath expression:		version of this document using the XPath expression:
	'//sourcecode[@type="cddl"]'		'//sourcecode[@type="cddl"]'
	The following initial fragment defines the top-level symbols of this		The following initial fragment defines the top-level symbols of this
	document's CDDL, which includes the example CBOR content.		document's CDDL, which includes the example CBOR content.
	start = acme-record / bundle / tstr		start = acme-record / bundle / tstr
			The definitions for the rule bundle and socket $admin-record are
			taken from Appendix B of [RFC9171].
	1.4. Terminology		1.4. Terminology
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in		"OPTIONAL" in this document are to be interpreted as described in
	BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all		BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
	capitals, as shown here.		capitals, as shown here.
	Because this document combines two otherwise unrelated contexts, ACME		Because this document combines two otherwise unrelated contexts, ACME
	and DTN, when a protocol term applies to one of those areas and is		and DTN, when a protocol term applies to one of those areas and is
	skipping to change at line 512 ¶		skipping to change at line 516 ¶
	Challenge Object (Section 3.1) contained in an authorization		Challenge Object (Section 3.1) contained in an authorization
	object associated with the order in accordance with Section 7.1.4		object associated with the order in accordance with Section 7.1.4
	of [RFC8555].		of [RFC8555].
	3. The ACME client indicates to the administrative element of its BP		3. The ACME client indicates to the administrative element of its BP
	Agent the id-chal that is authorized for use along with the		Agent the id-chal that is authorized for use along with the
	associated token-chal and client account key thumbprint. The		associated token-chal and client account key thumbprint. The
	ACME client waits, if necessary, until the Agent is configured		ACME client waits, if necessary, until the Agent is configured
	before proceeding to the next step.		before proceeding to the next step.
	4. The ACME client POSTs a response object (Section 3.2) to the		4. The ACME client POSTs a Response Object (Section 3.2) to the
	challenge URL on the ACME server in accordance with Section 7.5.1		challenge URL on the ACME server in accordance with Section 7.5.1
	of [RFC8555]. The payload object is constructed in accordance		of [RFC8555]. The payload object is constructed in accordance
	with Section 3.2.		with Section 3.2.
	5. The administrative element waits for a Challenge Bundle to be		5. The administrative element waits for a Challenge Bundle to be
	received with the authorized ACME parameters, including its id-		received with the authorized ACME parameters, including its id-
	chal payload, in accordance with Section 3.3.		chal payload, in accordance with Section 3.3.
	6. The administrative element concatenates token-bundle with token-		6. The administrative element concatenates token-bundle with token-
	chal (each as base64url-encoded text strings) and computes the		chal (each as base64url-encoded text strings) and computes the
	skipping to change at line 562 ¶		skipping to change at line 566 ¶
	accordance with Section 3.2.		accordance with Section 3.2.
	4. The ACME server sends, via the administrative element of its BP		4. The ACME server sends, via the administrative element of its BP
	Agent, one or more Challenge Bundles in accordance with		Agent, one or more Challenge Bundles in accordance with
	Section 3.3. Each Challenge Bundle contains a distinct, random		Section 3.3. Each Challenge Bundle contains a distinct, random
	token-bundle to be able to correlate with a Response Bundle.		token-bundle to be able to correlate with a Response Bundle.
	Computing an expected Key Authorization digest is not necessary		Computing an expected Key Authorization digest is not necessary
	until a response is received with a chosen hash algorithm.		until a response is received with a chosen hash algorithm.
	5. The ACME server waits for a Response Bundle(s) for a limited		5. The ACME server waits for a Response Bundle(s) for a limited
	interval of time (based on the response object of Section 3.2).		interval of time (based on the Response Object of Section 3.2).
	Responses are encoded in accordance with Section 3.4.		Responses are encoded in accordance with Section 3.4.
	6. Once received and decoded, the ACME server checks the contents of		6. Once received and decoded, the ACME server checks the contents of
	each Response Bundle in accordance with Section 3.4.1. After all		each Response Bundle in accordance with Section 3.4.1. After all
	Challenge Bundles have either been responded to or timed-out, the		Challenge Bundles have either been responded to or timed-out, the
	ACME server policy (see Section 3.5) determines whether the		ACME server policy (see Section 3.5) determines whether the
	validation is successful. If validation is not successful, a		validation is successful. If validation is not successful, a
	client may retry the challenge that starts in Step 3.		client may retry the challenge that starts in Step 3.
	When responding to a Challenge Bundle, a BP Agent SHALL send a single		When responding to a Challenge Bundle, a BP Agent SHALL send a single
	skipping to change at line 625 ¶		skipping to change at line 629 ¶
	"token-chal": "tPUZNY4ONIk6LxErRFEjVw"		"token-chal": "tPUZNY4ONIk6LxErRFEjVw"
	}		}
	The token-chal value included in this object applies to the entire		The token-chal value included in this object applies to the entire
	challenge and may correspond with multiple separate token-bundle		challenge and may correspond with multiple separate token-bundle
	values when multiple Challenge Bundles are sent for a single		values when multiple Challenge Bundles are sent for a single
	validation.		validation.
	3.2. DTN Node ID Response Object		3.2. DTN Node ID Response Object
	The DTN Node ID response object is sent by the ACME client when it		The DTN Node ID Response Object is sent by the ACME client when it
	authorizes validation of a Node ID as defined in Section 7.5.1 of		authorizes validation of a Node ID as defined in Section 7.5.1 of
	[RFC8555]. Because a DTN has the potential for significantly longer		[RFC8555]. Because a DTN has the potential for significantly longer
	(but roughly predictable) delays than a non-DTN network, the ACME		(but roughly predictable) delays than a non-DTN network, the ACME
	client is able to inform the ACME server if a particular validation		client is able to inform the ACME server if a particular validation
	round-trip is expected to take longer than non-DTN network delays (on		round-trip is expected to take longer than non-DTN network delays (on
	the order of seconds).		the order of seconds).
	The DTN Node ID response object has the following content:		The DTN Node ID Response Object has the following content:
	rtt (optional, number): An expected Round-Trip Time (RTT), in		rtt (optional, number): An expected Round-Trip Time (RTT), in
	seconds, between sending a Challenge Bundle and receiving a		seconds, between sending a Challenge Bundle and receiving a
	Response Bundle. This value is a hint to the ACME server for how		Response Bundle. This value is a hint to the ACME server for how
	long to wait for responses but is not authoritative. The minimum		long to wait for responses but is not authoritative. The minimum
	RTT value SHALL be zero. There is no special significance to		RTT value SHALL be zero. There is no special significance to
	zero-value RTT, it simply indicates the response is expected in		zero-value RTT, it simply indicates the response is expected in
	less than the least significant unit used by the ACME client.		less than the least significant unit used by the ACME client.
	{		{
	"rtt": 300.0		"rtt": 300.0
	}		}
	A response object SHALL NOT be sent until the BP Agent has been		A Response Object SHALL NOT be sent until the BP Agent has been
	configured to properly respond to the challenge. The RTT value is		configured to properly respond to the challenge. The RTT value is
	meant to indicate any node-specific path delays expected to be		meant to indicate any node-specific path delays expected to be
	encountered from the ACME server. Because there is no requirement on		encountered from the ACME server. Because there is no requirement on
	the path (or paths) regarding which Bundles may traverse between the		the path (or paths) regarding which Bundles may traverse between the
	ACME server and the BP Agent, and the ACME server can attempt some		ACME server and the BP Agent, and the ACME server can attempt some
	path diversity, the RTT value SHOULD be pessimistic.		path diversity, the RTT value SHOULD be pessimistic.
	A default Bundle response interval, used when the object does not		A default Bundle response interval, used when the object does not
	contain an RTT, SHOULD be a configurable parameter of the ACME		contain an RTT, SHOULD be a configurable parameter of the ACME
	server. If the ACME client indicated an RTT value in the object, the		server. If the ACME client indicated an RTT value in the object, the
	skipping to change at line 1019 ¶		skipping to change at line 1023 ¶
	6.2. Threat: BP Node Impersonation		6.2. Threat: BP Node Impersonation
	As described in Section 10.1 of [RFC8555], it is possible for an		As described in Section 10.1 of [RFC8555], it is possible for an
	active attacker to alter data on both ACME client channel and the DTN		active attacker to alter data on both ACME client channel and the DTN
	validation channel.		validation channel.
	The primary mitigation is to delegate Bundle integrity sourcing to a		The primary mitigation is to delegate Bundle integrity sourcing to a
	trusted routing node near, in the sense of Bundle routing topology,		trusted routing node near, in the sense of Bundle routing topology,
	the Bundle source node as defined in Section 4. This is functionally		the Bundle source node as defined in Section 4. This is functionally
	similar to the DKIM signing [RFC6376] and provides some level of		similar to DKIM email signing [RFC6376] and provides some level of
	secure Bundle origination.		secure Bundle origination.
	Another way to mitigate on-path attacks is to attempt validation of		Another way to mitigate on-path attacks is to attempt validation of
	the same Node ID from multiple sources, hopefully via multiple Bundle		the same Node ID from multiple sources, hopefully via multiple Bundle
	routing paths, as defined in Section 3.5. It is not a trivial task		routing paths, as defined in Section 3.5. It is not a trivial task
	to guarantee Bundle routing though, so more advanced techniques such		to guarantee Bundle routing though, so more advanced techniques such
	as onion routing (using Bundle-in-Bundle encapsulation) could be		as onion routing (using Bundle-in-Bundle encapsulation) could be
	employed.		employed.
	6.3. Threat: Bundle Replay		6.3. Threat: Bundle Replay
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