Re: [Pce] Ben Campbell's Discuss on draft-ietf-pce-pceps-15: (with DISCUSS and COMMENT)
> On Aug 8, 2017, at 6:48 AM, Dhruv Dhody wrote: > > Hi Ben, > >> -Original Message- >> From: Ben Campbell [mailto:b...@nostrum.com] >> Sent: 08 August 2017 03:08 >> To: Dhruv Dhody >> Cc: cmarga...@juniper.net; draft-ietf-pce-pc...@ietf.org; pce@ietf.org; >> The IESG ; pce-cha...@ietf.org >> Subject: Re: [Pce] Ben Campbell's Discuss on draft-ietf-pce-pceps-15: >> (with DISCUSS and COMMENT) >> > (snip) >>>> >>>>> >>>>>> - 3.2: "Implementations MUST support SHA-256 as defined by [SHS] as >>>>>>the hash algorithm for the fingerprint." >>>>>> Do you really intend "MUST support" (meaning you have to be able to >>>>>> handle sha-256, but could allow other hashes) vs "MUST use"? >>>>>> >>>>> [[Dhruv Dhody]] Yes, additional hash algorithm MAY also be >>>> supported/used. >>>>> >>>> >>>> Is there an expectation people will use multiple hash algorithms >>>> side-by- side? Or is this for purposes of hash agility? >>>> >>> [[Dhruv Dhody]] SHA-256 is the current mandatory hash, others might >> become usable and useful as the technology evolves. Do you have any >> suggested change in mind? >>> I see RFC6614 use similar language "Implementations MUST support SHA-1 >> as the hash algorithm for the fingerprint…." >> >> I guess my question is whether the intent is for implementations to be >> able to pick any hash they want, as long as SHA-256 is an option, or do >> you expect everyone to use SHA-256 unless that is replaced at some point >> due to security concerns. If the former, “MUST support…” makes sense. If >> the latter, something like “MUST (or SHOULD) use…” with a caveat that >> future specs might update this if SHA-256 is proven unsafe at some point >> in the future. >> > [[Dhruv Dhody]] I was incorrect in my reply before, it is the latter, as we > also have this text in the security considerations that explains this - > > When using certificate fingerprints to identify PCEPS peers, any two > certificates that produce the same hash value will be considered the > same peer. Therefore, it is important to make sure that the hash > function used is cryptographically uncompromised, so that attackers > are very unlikely to be able to produce a hash collision with a > certificate of their choice. This document mandates support for > SHA-256 as defined by [SHS], but a later revision may demand support > for stronger functions if suitable attacks on it are known. > > So a future revision would update the Hash function to be used. I will update > the text as you suggest. > >> My real concern here is interoperability—if an implementation chooses a >> hash other than SHA-256, how does the peer know what hash to use? >> > [[Dhruv Dhody]] This is a local property and does not need to be exchanged. > The peer provides the certificate, based on local hash function in use, the > hash of DER encoded certificate octets is created and compared to a local > fingerprint configured. Ah, that makes sense, thanks! (And in any case, the question is moot based on the rest of your response.) I can’t remember if I mentioned it, but I have cleared my DISCUSS position and entered a YES. Thanks! Ben. > >>> >>> (snip) >>> > > Regards, > Dhruv ___ Pce mailing list Pce@ietf.org https://www.ietf.org/mailman/listinfo/pce
Re: [Pce] Ben Campbell's Discuss on draft-ietf-pce-pceps-15: (with DISCUSS and COMMENT)
Hi Ben, > -Original Message- > From: Ben Campbell [mailto:b...@nostrum.com] > Sent: 08 August 2017 03:08 > To: Dhruv Dhody > Cc: cmarga...@juniper.net; draft-ietf-pce-pc...@ietf.org; pce@ietf.org; > The IESG ; pce-cha...@ietf.org > Subject: Re: [Pce] Ben Campbell's Discuss on draft-ietf-pce-pceps-15: > (with DISCUSS and COMMENT) > (snip) > >> > >>> > >>>> - 3.2: "Implementations MUST support SHA-256 as defined by [SHS] as > >>>> the hash algorithm for the fingerprint." > >>>> Do you really intend "MUST support" (meaning you have to be able to > >>>> handle sha-256, but could allow other hashes) vs "MUST use"? > >>>> > >>> [[Dhruv Dhody]] Yes, additional hash algorithm MAY also be > >> supported/used. > >>> > >> > >> Is there an expectation people will use multiple hash algorithms > >> side-by- side? Or is this for purposes of hash agility? > >> > > [[Dhruv Dhody]] SHA-256 is the current mandatory hash, others might > become usable and useful as the technology evolves. Do you have any > suggested change in mind? > > I see RFC6614 use similar language "Implementations MUST support SHA-1 > as the hash algorithm for the fingerprint…." > > I guess my question is whether the intent is for implementations to be > able to pick any hash they want, as long as SHA-256 is an option, or do > you expect everyone to use SHA-256 unless that is replaced at some point > due to security concerns. If the former, “MUST support…” makes sense. If > the latter, something like “MUST (or SHOULD) use…” with a caveat that > future specs might update this if SHA-256 is proven unsafe at some point > in the future. > [[Dhruv Dhody]] I was incorrect in my reply before, it is the latter, as we also have this text in the security considerations that explains this - When using certificate fingerprints to identify PCEPS peers, any two certificates that produce the same hash value will be considered the same peer. Therefore, it is important to make sure that the hash function used is cryptographically uncompromised, so that attackers are very unlikely to be able to produce a hash collision with a certificate of their choice. This document mandates support for SHA-256 as defined by [SHS], but a later revision may demand support for stronger functions if suitable attacks on it are known. So a future revision would update the Hash function to be used. I will update the text as you suggest. > My real concern here is interoperability—if an implementation chooses a > hash other than SHA-256, how does the peer know what hash to use? > [[Dhruv Dhody]] This is a local property and does not need to be exchanged. The peer provides the certificate, based on local hash function in use, the hash of DER encoded certificate octets is created and compared to a local fingerprint configured. > > > > (snip) > > Regards, Dhruv ___ Pce mailing list Pce@ietf.org https://www.ietf.org/mailman/listinfo/pce
Re: [Pce] Ben Campbell's Discuss on draft-ietf-pce-pceps-15: (with DISCUSS and COMMENT)
Hi, also inline: Thanks! Ben. > On Aug 4, 2017, at 1:40 PM, Dhruv Dhody wrote: > > Hi Ben, > > Please see inline... > >> -Original Message- >> From: Ben Campbell [mailto:b...@nostrum.com] >> Sent: 03 August 2017 20:57 >> To: Dhruv Dhody >> Cc: The IESG ; cmarga...@juniper.net; draft-ietf-pce- >> pc...@ietf.org; pce@ietf.org; pce-cha...@ietf.org >> Subject: Re: [Pce] Ben Campbell's Discuss on draft-ietf-pce-pceps-15: >> (with DISCUSS and COMMENT) > > (snip) > >>>> >>>> - >>>> - >>>> COMMENT: >>>> - >>>> - >>>> >>>> Substantive: >>>> >>>> - I share Warren's question about why you chose STARTTLS over a >>>> dedicated port, especially since the 2nd to last paragraph in 3.2 >>>> goes out of its way to mention that. What were the tradeoffs involved >>>> that made adding the additional protocol machinery more attractive >>>> than allocating a port number? >>>> >>> [[Dhruv Dhody]] I have added this text - >>> >>> This document uses the standard StartTLS procedure in PCEP, instead >>> of using a different port for the secured session. This is done to >>> avoid requesting allocation of another port number for the PCEPS. >>> The StartTLS procedure makes more efficient use of scarce port >>> numbers and allow simpler configuration of PCEP. >> >> That’s helpful, but it only shows the benefits side of the tradeoff. I >> assume people thought the additional protocol complexity was a reasonable >> cost to bear? >> > [[Dhruv Dhody]] There was substantive discussion on the mailing list > regarding this, as our original proposal requested a new port and we were > advised to use StartTLS instead after discussion with transport/security > folks. See https://www.ietf.org/mail-archive/web/pce/current/msg03540.html. Okay, good enough. > > >> >>> >>>> - 3.2: "Implementations MUST support SHA-256 as defined by [SHS] as >>>> the hash algorithm for the fingerprint." >>>> Do you really intend "MUST support" (meaning you have to be able to >>>> handle sha-256, but could allow other hashes) vs "MUST use"? >>>> >>> [[Dhruv Dhody]] Yes, additional hash algorithm MAY also be >> supported/used. >>> >> >> Is there an expectation people will use multiple hash algorithms side-by- >> side? Or is this for purposes of hash agility? >> > [[Dhruv Dhody]] SHA-256 is the current mandatory hash, others might become > usable and useful as the technology evolves. Do you have any suggested change > in mind? > I see RFC6614 use similar language "Implementations MUST support SHA-1 as the > hash algorithm for the fingerprint…." I guess my question is whether the intent is for implementations to be able to pick any hash they want, as long as SHA-256 is an option, or do you expect everyone to use SHA-256 unless that is replaced at some point due to security concerns. If the former, “MUST support…” makes sense. If the latter, something like “MUST (or SHOULD) use…” with a caveat that future specs might update this if SHA-256 is proven unsafe at some point in the future. My real concern here is interoperability—if an implementation chooses a hash other than SHA-256, how does the peer know what hash to use? > > (snip) > >>>> - 3.4 : "Negotiation of mutual authentication is REQUIRED." >>>> Does that mean that the peers must elect to use mutual >>>> authentication, or that if they want to use it, they must agree to do >>>> so? (The pattern persists throughout the section, but the meaning >>>> seems more obvious for some of the >>>> others.) >>>> >>> [[Dhruv Dhody]] I am also not sure, this was added keeping RFC6614 as >> our reference. >>> Since TLS supports multiple authentication mode, this might be a say >>> mutual as well as server-only authentication should be supported. But >>> not sure about the word negotiation here. I think we can remove this >>> statement, will do so once you confirm. he >> >> The important thing is that the intent of the WG is clear. Do you mean to >> say that the working group intended to allow both server-only and mutual >> authentication, or do you mean to say the working group did not think >> about it? >> > [[Dhruv Dhody]] On further discussion with my co-authors, we feel we should > remove the statement. The previous statement in the draft about mutual > authentication is enough and mutual authentication should be the standard. Okay. > > Regards, > Dhruv > >> […] >> Thanks! >> >> Ben. ___ Pce mailing list Pce@ietf.org https://www.ietf.org/mailman/listinfo/pce
Re: [Pce] Ben Campbell's Discuss on draft-ietf-pce-pceps-15: (with DISCUSS and COMMENT)
Hi Ben, Please see inline... > -Original Message- > From: Ben Campbell [mailto:b...@nostrum.com] > Sent: 03 August 2017 20:57 > To: Dhruv Dhody > Cc: The IESG ; cmarga...@juniper.net; draft-ietf-pce- > pc...@ietf.org; pce@ietf.org; pce-cha...@ietf.org > Subject: Re: [Pce] Ben Campbell's Discuss on draft-ietf-pce-pceps-15: > (with DISCUSS and COMMENT) (snip) > >> > >> - > >> - > >> COMMENT: > >> - > >> - > >> > >> Substantive: > >> > >> - I share Warren's question about why you chose STARTTLS over a > >> dedicated port, especially since the 2nd to last paragraph in 3.2 > >> goes out of its way to mention that. What were the tradeoffs involved > >> that made adding the additional protocol machinery more attractive > >> than allocating a port number? > >> > > [[Dhruv Dhody]] I have added this text - > > > > This document uses the standard StartTLS procedure in PCEP, instead > > of using a different port for the secured session. This is done to > > avoid requesting allocation of another port number for the PCEPS. > > The StartTLS procedure makes more efficient use of scarce port > > numbers and allow simpler configuration of PCEP. > > That’s helpful, but it only shows the benefits side of the tradeoff. I > assume people thought the additional protocol complexity was a reasonable > cost to bear? > [[Dhruv Dhody]] There was substantive discussion on the mailing list regarding this, as our original proposal requested a new port and we were advised to use StartTLS instead after discussion with transport/security folks. See https://www.ietf.org/mail-archive/web/pce/current/msg03540.html. > > > > >> - 3.2: "Implementations MUST support SHA-256 as defined by [SHS] as > >> the hash algorithm for the fingerprint." > >> Do you really intend "MUST support" (meaning you have to be able to > >> handle sha-256, but could allow other hashes) vs "MUST use"? > >> > > [[Dhruv Dhody]] Yes, additional hash algorithm MAY also be > supported/used. > > > > Is there an expectation people will use multiple hash algorithms side-by- > side? Or is this for purposes of hash agility? > [[Dhruv Dhody]] SHA-256 is the current mandatory hash, others might become usable and useful as the technology evolves. Do you have any suggested change in mind? I see RFC6614 use similar language "Implementations MUST support SHA-1 as the hash algorithm for the fingerprint" (snip) > >> - 3.4 : "Negotiation of mutual authentication is REQUIRED." > >> Does that mean that the peers must elect to use mutual > >> authentication, or that if they want to use it, they must agree to do > >> so? (The pattern persists throughout the section, but the meaning > >> seems more obvious for some of the > >> others.) > >> > > [[Dhruv Dhody]] I am also not sure, this was added keeping RFC6614 as > our reference. > > Since TLS supports multiple authentication mode, this might be a say > > mutual as well as server-only authentication should be supported. But > > not sure about the word negotiation here. I think we can remove this > > statement, will do so once you confirm. he > > The important thing is that the intent of the WG is clear. Do you mean to > say that the working group intended to allow both server-only and mutual > authentication, or do you mean to say the working group did not think > about it? > [[Dhruv Dhody]] On further discussion with my co-authors, we feel we should remove the statement. The previous statement in the draft about mutual authentication is enough and mutual authentication should be the standard. Regards, Dhruv > […] > Thanks! > > Ben. ___ Pce mailing list Pce@ietf.org https://www.ietf.org/mailman/listinfo/pce
Re: [Pce] Ben Campbell's Discuss on draft-ietf-pce-pceps-15: (with DISCUSS and COMMENT)
Thanks, please also see inline. I will remove sections that do not seem to need further comment. > On Aug 3, 2017, at 8:35 AM, Dhruv Dhody wrote: > > Hi Ben, > > Thanks for your review. See inline.. > >> -Original Message- >> From: Pce [mailto:pce-boun...@ietf.org] On Behalf Of Ben Campbell >> […] >> >> -- >> DISCUSS: >> -- >> >> -3.4, step 2: "Peer validation always SHOULD include a check on whether >> the locally configured expected DNS name or IP address of >> the peer that is contacted matches its presented >> certificate." >> >> Why is that not a MUST? As it is, this need to at least discuss the risks >> involved if you don't check the identity of the peer cert (here or in the >> security considerations.) >> > [[Dhruv Dhody]] Reworded to say - > > + Implementations MUST follow the rules and guidelines for > peer validation as defined in [RFC6125]. If an expected > DNS name or IP address for the peer is configured, then the > implementations MUST check them against the values in the > presented certificate. Thanks, that would resolve my DISCUSS position. >> >> -- >> COMMENT: >> -- >> >> Substantive: >> >> - I share Warren's question about why you chose STARTTLS over a dedicated >> port, especially since the 2nd to last paragraph in 3.2 goes out of its >> way to mention that. What were the tradeoffs involved that made adding the >> additional protocol machinery more attractive than allocating a port >> number? >> > [[Dhruv Dhody]] I have added this text - > > This document uses the standard StartTLS procedure in PCEP, instead > of using a different port for the secured session. This is done to > avoid requesting allocation of another port number for the PCEPS. > The StartTLS procedure makes more efficient use of scarce port > numbers and allow simpler configuration of PCEP. That’s helpful, but it only shows the benefits side of the tradeoff. I assume people thought the additional protocol complexity was a reasonable cost to bear? > >> - 3.2: "Implementations MUST support SHA-256 as defined by [SHS] as >> the hash algorithm for the fingerprint." >> Do you really intend "MUST support" (meaning you have to be able to handle >> sha-256, but could allow other hashes) vs "MUST use"? >> > [[Dhruv Dhody]] Yes, additional hash algorithm MAY also be supported/used. > Is there an expectation people will use multiple hash algorithms side-by-side? Or is this for purposes of hash agility? >> - 3.5: "Implementations >> that want to support a wide variety of trust models SHOULD expose as >> many details of the presented certificate to the administrator as >> possible >> so that the trust model can be implemented by the administrator." >> "as much as possible" is pretty vague for the a 2119 SHOULD. Since the >> following sentences also include a SHOULD along with considerably more >> detail, I suggest dropping the SHOULD in this sentence, and leaving the >> one in the following sentence. >> > [[Dhruv Dhody]] Ack. > >> - 3.6: Is the exponential backoff requirement part of the procedures in >> 5440? >> The wording suggests that it is not. If so, it needs elaboration here. >> > [[Dhruv Dhody]] It is part of RFC5440, text updated to - > > The initiator SHOULD follow the procedure listed in [RFC5440] to > retry session setup as per the exponential back-off session > establishment retry procedure. > >> Editorial: >> >> - 3.2, paragraph 8: s/"... PCE MUST responds with..."/ "...PCE MUST >> respond with..." >> > [[Dhruv Dhody]] Ack > >> - 3.4 : "Negotiation of mutual authentication is REQUIRED." >> Does that mean that the peers must elect to use mutual authentication, or >> that if they want to use it, they must agree to do so? (The pattern >> persists throughout the section, but the meaning seems more obvious for >> some of the >> others.) >> > [[Dhruv Dhody]] I am also not sure, this was added keeping RFC6614 as our > reference. > Since TLS supports multiple authentication mode, this might be a say mutual > as well as server-only authentication should be supported. But not sure about > the word negotiation here. I think we can remove this statement, will do so > once you confirm. he The important thing is that the intent of the WG is clear. Do you mean to say that the working group intended to allow both server-only and mutual authentication, or do you mean to say the working group did not think about it? […] Thanks! Ben. ___ Pce mailing list Pce@ietf.org https://www.ietf.org/mailman/listinfo/pce
Re: [Pce] Ben Campbell's Discuss on draft-ietf-pce-pceps-15: (with DISCUSS and COMMENT)
Hi Ben, Thanks for your review. See inline.. > -Original Message- > From: Pce [mailto:pce-boun...@ietf.org] On Behalf Of Ben Campbell > Sent: 03 August 2017 04:19 > To: The IESG > Cc: cmarga...@juniper.net; draft-ietf-pce-pc...@ietf.org; pce@ietf.org; > pce-cha...@ietf.org > Subject: [Pce] Ben Campbell's Discuss on draft-ietf-pce-pceps-15: (with > DISCUSS and COMMENT) > > Ben Campbell has entered the following ballot position for > draft-ietf-pce-pceps-15: Discuss > > 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 https://www.ietf.org/iesg/statement/discuss-criteria.html > for more information about IESG DISCUSS and COMMENT positions. > > > The document, along with other ballot positions, can be found here: > https://datatracker.ietf.org/doc/draft-ietf-pce-pceps/ > > > > -- > DISCUSS: > -- > > -3.4, step 2: "Peer validation always SHOULD include a check on whether >the locally configured expected DNS name or IP address of >the peer that is contacted matches its presented >certificate." > > Why is that not a MUST? As it is, this need to at least discuss the risks > involved if you don't check the identity of the peer cert (here or in the > security considerations.) > [[Dhruv Dhody]] Reworded to say - + Implementations MUST follow the rules and guidelines for peer validation as defined in [RFC6125]. If an expected DNS name or IP address for the peer is configured, then the implementations MUST check them against the values in the presented certificate. > > -- > COMMENT: > -- > > Substantive: > > - I share Warren's question about why you chose STARTTLS over a dedicated > port, especially since the 2nd to last paragraph in 3.2 goes out of its > way to mention that. What were the tradeoffs involved that made adding the > additional protocol machinery more attractive than allocating a port > number? > [[Dhruv Dhody]] I have added this text - This document uses the standard StartTLS procedure in PCEP, instead of using a different port for the secured session. This is done to avoid requesting allocation of another port number for the PCEPS. The StartTLS procedure makes more efficient use of scarce port numbers and allow simpler configuration of PCEP. > - 3.2: "Implementations MUST support SHA-256 as defined by [SHS] as > the hash algorithm for the fingerprint." > Do you really intend "MUST support" (meaning you have to be able to handle > sha-256, but could allow other hashes) vs "MUST use"? > [[Dhruv Dhody]] Yes, additional hash algorithm MAY also be supported/used. > - 3.5: "Implementations >that want to support a wide variety of trust models SHOULD expose as >many details of the presented certificate to the administrator as > possible >so that the trust model can be implemented by the administrator." > "as much as possible" is pretty vague for the a 2119 SHOULD. Since the > following sentences also include a SHOULD along with considerably more > detail, I suggest dropping the SHOULD in this sentence, and leaving the > one in the following sentence. > [[Dhruv Dhody]] Ack. > - 3.6: Is the exponential backoff requirement part of the procedures in > 5440? > The wording suggests that it is not. If so, it needs elaboration here. > [[Dhruv Dhody]] It is part of RFC5440, text updated to - The initiator SHOULD follow the procedure listed in [RFC5440] to retry session setup as per the exponential back-off session establishment retry procedure. > Editorial: > > - 3.2, paragraph 8: s/"... PCE MUST responds with..."/ "...PCE MUST > respond with..." > [[Dhruv Dhody]] Ack > - 3.4 : "Negotiation of mutual authentication is REQUIRED." > Does that mean that the peers must elect to use mutual authentication, or > that if they want to use it, they must agree to do so? (The pattern > persists throughout the section, but the meaning seems more obvious for > some of the > others.) > [[Dhruv Dhody]] I am also not sure, this was added keeping RFC6614 as our reference. Since TLS supports multiple authentication mode, this might be a say mutual as well as server-only authentication should be supported. But not sure about the word negotiation here. I think we can remove this statement, will do so once you confirm. > -3.5, 2nd to last paragraph: Please don't use 2119 keywords to describe > pre-existing or external requirements. They should be reserved for the > authoritative specification of a given requirement. > [[Dhruv Dhody]] Ack. Updated. >
