jiebi/CodeConvo huggingface dataset:
Code change:
The server operator can only use TLS signature schemes for which the CA will issue credentials. <del> These dependencies cause problems in practice.  Server operators often deploy TLS termination services in locations such as remote data centers or Content Delivery Networks (CDNs) where it may be difficult to detect key compromises.  Short-lived certificates may be used to limit the exposure of keys in these cases. However, short-lived certificates need to be renewed more frequently than long-lived certificates.  If an external CA is unable to issue a certificate in time to replace a deployed certificate, the server would no longer be able to present a valid certificate to clients. With short-lived certificates, there is a smaller window of time to renew a certificates and therefore a higher risk that an outage at a CA will negatively affect the uptime of the service. </del> To reduce the dependency on external CAs, this document proposes a limited delegation mechanism that allows a TLS peer to issue its own credentials within the scope of a certificate issued by an external

Related discussion:
text: The text does not address my concern and will recap my perspective of the discussion. My initial comment was that the reference [KEYLESS] points to a solution that does not work with TLS 1.3 and currently the only effort compatible with TLS 1.3 is draft-mglt-lurk-tls13. I expect this reference to be mentioned and I do not see it in the text proposed text. If the intention with [KEYLESS] is to mention TLS Handshake Proxying techniques, then I argued that other mechanisms be mentioned and among others draft-mglt-lurk-tls12 and draft-mglt-lurk-tls13 that address different versions of TLS. This was my second concern and I do not see any of these references being mentioned. The way I understand your response is that the paper pointed out by [KEYLESS] is not Cloudflare's commercial product but instead a generic TLS Handshake proxying and that you propose to add a reference to an academic paper that discusses the LURK extension for TLS 1.2. I appreciate that other solutions - and in this case LURK, are being considered. I am wondering however why draft-mglt-lurk-tls12 is being replaced by an academic reference [REF2] and why draft-mglt-lurk-tls13 has been omitted. It seems that we are trying to avoid any reference of the work that is happening at the IETF. Is there anything I am missing ? My suggestion for the text OLD: (e.g., a PKCS interface or a remote signing mechanism [KEYLESS]) NEW: (e.g., a PKCS interface or a remote signing mechanism such as [draft-mglt-lurk-tls13] or [draft-mglt-lurk-tls12] ([LURK-TLS12]) or [KEYLESS]) with [KEYLESS] Sullivan, N. and D. Stebila, "An Analysis of TLS Handshake Proxying", IEEE TrustCom/BigDataSE/ISPA 2015, 2015.
Code change:
The server operator can only use TLS signature schemes for which the CA will issue credentials. <del> These dependencies cause problems in practice.  Server operators often deploy TLS termination services in locations such as remote data centers or Content Delivery Networks (CDNs) where it may be difficult to detect key compromises.  Short-lived certificates may be used to limit the exposure of keys in these cases. However, short-lived certificates need to be renewed more frequently than long-lived certificates.  If an external CA is unable to issue a certificate in time to replace a deployed certificate, the server would no longer be able to present a valid certificate to clients. With short-lived certificates, there is a smaller window of time to renew a certificates and therefore a higher risk that an outage at a CA will negatively affect the uptime of the service. </del> To reduce the dependency on external CAs, this document proposes a limited delegation mechanism that allows a TLS peer to issue its own credentials within the scope of a certificate issued by an external

Related discussion:
text: [LURK-TLS12] Boureanu, I., Migault, D., Preda, S., Alamedine, H.A., Mishra, S. Fieau, F., and M. Mannan, "LURK: Server-Controlled TLS Delegation”, IEEE TrustCom 2020, URL, 2020. [draft-mglt-lurk-tls12] IETF draft [draft-mglt-lurk-tls13] IETF draft It is unclear to me what is generic about the paper pointed by [KEYLESS] or [REF1]. In any case, for clarification, the paper clearly refers to Cloudflare commercial products as opposed to a generic mechanism, and this will remain whatever label will be used as a reference. Typically, Cloudflare co-authors the paper appears 12 times in the 8 page paper. The contribution section mentions: """ Our work focuses specifically on the TLS handshake proxying system implemented by CloudFlare in their Keyless SSL product [6], [7] """ The methodology mentions says: """ We tested TLS key proxying using CloudFlare’s implementation, which was implemented with the following three parts: """ """ The different scenarios were set up through CloudFlare’s control panel. In the direct handshake handshake scenario, the site is set up with no reverse proxy. In the scenario where the key is held by the edge server, the same certificate that was used on the origin is uploaded to CloudFlare and the reverse proxy is enabled for the site. """ Cloudflare appears in at least references URL CloudFlare Inc., “CloudFlare Keyless SSL,” Sep. 2014, URL N. Sullivan, “Keyless SSL: The nitty gritty technical details,” Sep. 2014, URL works for me. works for me seems clearer. I suspect earlier clarifications addressed this. thanks that it way clearer. Daniel Migault Ericsson
Code change:
PSKs for TLS 1.3 and non-imported PSKs for earlier versions co-exist for incremental deployment. <del> ImportedIdentity.context MUST include the context used to derive the EPSK, if any exists.  For example, ImportedIdentity.context may </del> <ins> ImportedIdentity.context MUST include the context used to determine the EPSK, if any exists.  For example, ImportedIdentity.context may </ins> include information about peer roles or identities to mitigate Selfie-style reflection attacks Selfie.  See mitigate-selfie for more details.  If the EPSK is a key derived from some other protocol or

Related discussion:
text: I don't love a couple of the ways I phrased things here, so feel free to offer suggestions to improve it! modulo test vectors. (NAME it'll likely take some time to get those vectors. Do you think we should hold this document until that's done?)
This looks good modulo the open issue about incremental deployment. I don't think we need to hold the document up in order to get test vectors. Benjamin Kaduk has entered the following ballot position for draft-ietf-tls-external-psk-importer-06: Yes When responding, please keep the subject line intact and reply to all email addresses included in the To and CC lines. (Feel free to cut this introductory paragraph, however.) Please refer to URL for more information about IESG DISCUSS and COMMENT positions. The document, along with other ballot positions, can be found here: URL COMMENT: Sorry about the large volume of comments; this document is actually in pretty good shape, there are just a bunch of details that can be subtle to get exactly right. I specifically call out the note in Section 4.1 about which HKDF-Expand-Label is to be used, since that would affect the actual derived keys for DTLS 1.3 (and any hypothetical future TLS versions). Section 1 While there is no known way in which the same external PSK might produce related output in TLS 1.3 and prior versions, only limited analysis has been done. Applications SHOULD provision separate PSKs for TLS 1.3 and prior versions. To mitigate against any interference, this document specifies a PSK Importer interface by which external PSKs may be imported and subsequently bound to a specific key derivation function (KDF) and hash function for use in TLS 1.3 [RFC8446] and DTLS 1.3 [DTLS13]. [...] IIRC the main target use cases for this mechanism are for existing external PSKs (violating the "SHOULD" from the first quoted paragraph), as well as deployments that are simplified by only needing to provision a single PSK. Does it make sense to include such clarifying description here?
Code change:
PSKs for TLS 1.3 and non-imported PSKs for earlier versions co-exist for incremental deployment. <del> ImportedIdentity.context MUST include the context used to derive the EPSK, if any exists.  For example, ImportedIdentity.context may </del> <ins> ImportedIdentity.context MUST include the context used to determine the EPSK, if any exists.  For example, ImportedIdentity.context may </ins> include information about peer roles or identities to mitigate Selfie-style reflection attacks Selfie.  See mitigate-selfie for more details.  If the EPSK is a key derived from some other protocol or

Related discussion:
text: (Similarly, is it accurate to say that "[a]pplications SHOULD provision separate PSKs [...], but the mechanism defined in this document provides a partial mitigation for use when that is not possible"? Also, we only use the word "interference" twice in this document (this is the first instance), so it might be worth a couple more words to clarify the nature of the potential interference. Section 3 non-imported keys for TLS versions prior to TLS 1.3. Non-imported and imported PSKs are distinct since their identities are different on the wire. See Section 6 for more details. (side note?) I think the precise story here is a little subtle -- for any given key, the imported and non-imported identities are distinct, but in principle one could construct a non-imported identity that overlaps with an imported identity for a different key (and we say as much at the end of Section 7). This is vanishingly rare to happen by chance, but makes the statement as written not quite categorically true. That said, the change to the binder key derivation (§ 4.2) seems to obviate any potential consequences to such a collision (though the connection attempt would presumably fail). Endpoints which import external keys MUST NOT use either the external keys or the derived keys for any other purpose. Moreover, each IIUC, this is "MUST NOT use the keys that are input to the import process for any purpose other than the importer, and MUST NOT use the derived keys for any purpose other than TLS PSKs". Is it worth spelling it out explicitly like that? external PSK MUST be associated with at most one hash function, as per the rules in Section 4.2.11 from [RFC8446]. See Section 7 for more discussion. Does this requirement apply to the inputs to the importer process, the outputs, or both? Section 3.1 Imported PSK (IPSK): A PSK derived from an EPSK, External Identity, optional context string, target protocol, and target KDF. There is an "External Identity" that is contained within the EPSK itself; is the "External Identity" listed here distinct from that?
Code change:
PSKs for TLS 1.3 and non-imported PSKs for earlier versions co-exist for incremental deployment. <del> ImportedIdentity.context MUST include the context used to derive the EPSK, if any exists.  For example, ImportedIdentity.context may </del> <ins> ImportedIdentity.context MUST include the context used to determine the EPSK, if any exists.  For example, ImportedIdentity.context may </ins> include information about peer roles or identities to mitigate Selfie-style reflection attacks Selfie.  See mitigate-selfie for more details.  If the EPSK is a key derived from some other protocol or

Related discussion:
text: Section 4.1 The PSK Importer interface takes as input an EPSK with External Identity "externalidentity" and base key "epsk", as defined in Section 3.1, along with an optional context, and transforms it into a set of PSKs and imported identities for use in a connection based on target protocols and KDFs. In particular, for each supported target protocol "targetprotocol" and KDF "targetkdf", the importer constructs an ImportedIdentity structure as follows: If I understand correctly the "targetkdf" is supposed to be the KDF associated with the cipher suite(s) the derived PSK will be usable for. This is something of a divergence from RFC 8446, where we assume that the KDF will be HKDF and associate only a hash function with the cipher suite. While discussing a more generic KDF concept seems reasonable (and is directly in line with the cryptographic principles that motivate this work), I'd recommend adding a few more words somewhere in this section to clarify the relationship between the targetkdf and the cipher suite(s), probably in the paragraph that starts "[e]ndpoints SHOULD generate a compatible 'ipskx' for each target ciphersuite they offer". struct { opaque externalidentity; opaque context; uint16 targetprotocol; uint16 targetkdf; } ImportedIdentity; Should we say that this is using the TLS presentation language? ImportedIdentity.context MUST include the context used to derive the EPSK, if any exists. For example, ImportedIdentity.context may (nit?) "derive" suggests a cryptographic key derivation process, but the rest of the prose suggests that this is more a process of "identification" or "determination". Is there a more appropriate word to use? Given an ImportedIdentity and corresponding EPSK with base key "epsk", an Imported PSK IPSK with base key "ipskx" is computed as follows: epskx = HKDF-Extract(0, epsk) ipskx = HKDF-Expand-Label(epskx, "derived psk", Hash(ImportedIdentity), L) I think we need to say that the HKDF-Expand-Label used (i.e., the URL prefix) is the one corresponding to ImportedIdentity.targetprotocol.
Code change:
PSKs for TLS 1.3 and non-imported PSKs for earlier versions co-exist for incremental deployment. <del> ImportedIdentity.context MUST include the context used to derive the EPSK, if any exists.  For example, ImportedIdentity.context may </del> <ins> ImportedIdentity.context MUST include the context used to determine the EPSK, if any exists.  For example, ImportedIdentity.context may </ins> include information about peer roles or identities to mitigate Selfie-style reflection attacks Selfie.  See mitigate-selfie for more details.  If the EPSK is a key derived from some other protocol or

Related discussion:
text: L corresponds to the KDF output length of ImportedIdentity.targetkdf as defined in Section 9. For hash-based KDFs, such as HKDFSHA256(0x0001), this is the length of the hash function output, i.e., 32 octets. This is required for the IPSK to be of length (32 octets for SHA256, not all hash-based KDFs) The identity of "ipskx" as sent on the wire is ImportedIdentity, i.e., the serialized content of ImportedIdentity is used as the content of PskIdentity.identity in the PSK extension. The corresponding TLS 1.3 binder key is "ipskx". In RFC 8446, the "binderkey" is the output of the key schedule, but ipskx is an input to the key schedule. So I think we want to say something like "the corresponding PSK input for the TLS 1.3 key schedule is 'ipskx'". The hash function used for HKDF [RFC5869] is that which is associated with the EPSK. It is not the hash function associated with ImportedIdentity.targetkdf. If no hash function is specified, I predict that someone will mess up the hash function selection while implementing this. Perhaps we could provide test vectors for the full matrix of (EPSK Hash, targetkdf hash) pairs using SHA256/SHA384? SHA-256 [SHA2] MUST be used. Diversifying EPSK by I think we might be able to tolerate the protocol* having a strict requirement that the associated hash function is specified, and provide a recommended value that would be used by people deploying the protocol in the absence of other information. This might in some sense help future-proof the document for the scenario where SHA256 weakens or is broken and the default should change. KDFs, protocols, and context string(s) are known a priori. EPSKs MAY also be imported for early data use if they are bound to protocol settings and configurations that would otherwise be required for early data with normal (ticket-based PSK) resumption.
Code change:
PSKs for TLS 1.3 and non-imported PSKs for earlier versions co-exist for incremental deployment. <del> ImportedIdentity.context MUST include the context used to derive the EPSK, if any exists.  For example, ImportedIdentity.context may </del> <ins> ImportedIdentity.context MUST include the context used to determine the EPSK, if any exists.  For example, ImportedIdentity.context may </ins> include information about peer roles or identities to mitigate Selfie-style reflection attacks Selfie.  See mitigate-selfie for more details.  If the EPSK is a key derived from some other protocol or

Related discussion:
text: Minimally, that means Application-Layer Protocol Negotiation [RFC7301], QUIC RFC 8446 does not limit 0-RTT data to resumption, so I think we just want "if they are bound to the protocol settings and configuration that are required for sending early data". Also, nit: I think we usually refer to the "ALPN value" instead of just "ALPN" being configured. Section 5 If a client or server wish to deprecate a hash function and no longer use it for TLS 1.3, they remove the corresponding KDF from the set of target KDFs used for importing keys. This does not affect the KDF operation used to derive Imported PSKs. Should we also include a paragraph about how to deprecate the Hash used in deriving Imported PSKs? (It's fixed per EPSK, so, "configure a new EPSK", basically.) Section 6 Recall that TLS 1.2 permits computing the TLS PRF with any hash algorithm and PSK. Thus, an EPSK may be used with the same KDF (and underlying HMAC hash algorithm) as TLS 1.3 with importers. However, critically, the derived PSK will not be the same since the importer differentiates the PSK via the identity and target KDF and protocol. Thus, PSKs imported for TLS 1.3 are distinct from those used in TLS 1.2, and thereby avoid cross-protocol collisions. [...] As I read this I recalled that up in Section 1 we say that applications "SHOULD provision separate PSKs for TLS 1.3 and prior versions". The scenario being described here sounds like it can only occur if that SHOULD is ignored, which might be worth reiterating. We also say in § 4.1 that "external PSKs MUST NOT be imported for (D)TLS or prior versions". In light of these two observations, my best interpretation of the quoted text is that it should be equivalent to: NEW: Recall that TLS 1.2 permits computing the TLS PRF with any hash algorithm and PSK.
Code change:
PSKs for TLS 1.3 and non-imported PSKs for earlier versions co-exist for incremental deployment. <del> ImportedIdentity.context MUST include the context used to derive the EPSK, if any exists.  For example, ImportedIdentity.context may </del> <ins> ImportedIdentity.context MUST include the context used to determine the EPSK, if any exists.  For example, ImportedIdentity.context may </ins> include information about peer roles or identities to mitigate Selfie-style reflection attacks Selfie.  See mitigate-selfie for more details.  If the EPSK is a key derived from some other protocol or

Related discussion:
text: Accordingly, a given EPSK might be both used directly as a TLS 1.2 PSK and used with TLS 1.3 via the importer mechanism (noting that this configuration is not recommended, per Section 1), using the same KDF algorithm. However, because the TLS 1.3 importer mechanism includes an additional key-derivation step, the actual PSK used in the TLS 1.3 key schedule will be distinct from the one used in the TLS 1.2 key schedule, so there are no cross-protocol collisions possible. Note that this does not preclude endpoints from using non-imported PSKs for TLS 1.2. For some reason this line implies to me that endpoints might use imported PSKs for TLS 1.2, but this is forbidden by Section 4.1 (as quoted above). Perhaps "does not preclude endpoints from continuing to use TLS 1.2 and the non-imported PSKs it requires"? Section 7 We should probably note that any information placed in ImportedIdentity.context will be visible on the wire in cleartext, and thus that confidential identifiers from other protocols should either not be used or should be protected (e.g., by hashing) prior to use. Externally provisioned PSKs imported into a TLS connection achieve compound authentication of the provisioning process and connection. Context-free PSKs only achieve authentication within the context of a single connection. Do we need to use pskdhke to get the strong compound authentication property, or is it attainable with pskke as well? Section 10.1 I'm not sure why [QUIC] and RFC 5246 are listed as normative references. Appendix B The Selfie attack [Selfie] relies on a misuse of the PSK interface. The PSK interface makes the implicit assumption that each PSK is known only to one client and one server. If multiple clients or multiple servers with distinct roles share a PSK, TLS only authenticates the entire group. A node successfully authenticates its peer as being in the group whether the peer is another node or itself.
Code change:
PSKs for TLS 1.3 and non-imported PSKs for earlier versions co-exist for incremental deployment. <del> ImportedIdentity.context MUST include the context used to derive the EPSK, if any exists.  For example, ImportedIdentity.context may </del> <ins> ImportedIdentity.context MUST include the context used to determine the EPSK, if any exists.  For example, ImportedIdentity.context may </ins> include information about peer roles or identities to mitigate Selfie-style reflection attacks Selfie.  See mitigate-selfie for more details.  If the EPSK is a key derived from some other protocol or

Related discussion:
text: I think it may be useful to call out that the "multiple clients" and "multiple servers" case can occur even when there are only two endpoints that know the key (that is, when they do not have predetermined client/server roles). struct { opaque clientmac; opaque server_mac; } Context; We may not need the whole 16k to hold a MAC address, especially since this is just an example. If an attacker then redirects a ClientHello intended for one node to a different node, the receiver will compute a different context string and the handshake will not complete. Similarly to the above, this could be "a different node (including the node that generated the ClientHello)".
Code change:
likely the receiver will be able to process all the packets in a single pass.  A packet with a short header does not include a length, so it can only be the last packet included in a UDP datagram.  An <del> endpoint SHOULD NOT coalesce multiple packets at the same encryption level. </del> <ins> endpoint SHOULD include multiple frames in a single packet if they are to be sent at the same encryption level, instead of coalescing multiple packets at the same encryption level. </ins> Receivers MAY route based on the information in the first packet contained in a UDP datagram.  Senders MUST NOT coalesce QUIC packets

Related discussion:
text: This uses positive framing for the recommendation to use frames rather than packets. And it makes that recommendation directly, rather than implying it.
Here are three quasi-nits about S 12.2. Handshake, 1-RTT; see Section 4.1.4 of {{QUIC-TLS}}) makes it more likely the receiver will be able to process all the packets in a single pass. A packet with a short header does not include a length, so it can only be the last packet included in a UDP datagram. An endpoint SHOULD NOT coalesce multiple packets at the same encryption level. Is the implication here that you should instead pack all the frames into one packet? UDP datagram. Senders MUST NOT coalesce QUIC packets for different connections into a single UDP datagram. Receivers SHOULD ignore any subsequent packets with a different Destination Connection ID than the first packet in the datagram. Is there a valid reason to have different SCIDs? ({{packet-version}}), and packets with a short header ({{short-header}}) do not contain a Length field and so cannot be followed by other packets in the same UDP datagram. Note also that there is no situation where a Retry or Version Negotiation packet is coalesced with another packet. Should this be a MUST NOT?
Yes. See . I don't see why. It's just a fact, not a conformance requirement.
For (1) I think it would be helpful to say that.
LGTM, one suggestion.