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This all makes sense. PEP 740 mentions: > In their previously supported form on PyPI, PGP signatures satisfied considerations (1) and (3) above but not (2) (o

by opello 2y ago

This all makes sense. PEP 740 mentions: > In their previously supported form on PyPI, PGP signatures satisfied considerations (1) and (3) above but not (2) (owing to the need for external keyservers and key distribution) or (4) (due to PGP signatures typically being constructed over just an input file, without any associated signed metadata). It seems to me that the infrastructure investment in sigstore.dev vs. PGP seems arbitrary. For example, on the PGP side, PyPI keyserver and tooling to validate uploads as to address (2) above. And (4) being handled similar to PEP 740 with say signatures for provenance objects. Maybe the sigstore is "just way better" but it doesn't exactly seem so cut-and-dried of a technical argument from the things discussed in these commends and the linked material. It's perfectly responsible to make a choice. It seems unclear just what the scope of work difference would be despite there being a somewhat implicit suggestion across the discussions and links in the comments that it was great. Maybe that's an unreasonable level of detail to expect? But with what seems to come across as "dogging on PGP" it seems what I've found disappointing with my casual brush with this particular instance of PGP coming up in the news.

woodruffw 2y ago
(2) is addressed by Sigstore having its own infrastructure and a full-time rotation staff. PyPI doesn't need to run or operationalize anything, which is a significant relief compared to the prospect of having to operationalize a PGP keyserver with volunteer staffing. (I'm intentionally glossing over details here, like the fact that PyPI doesn't need to perform any online operations to validate Sigstore's signatures. The bottom line is that everything about it is operationally simpler and more modern than could be shaped out of the primitives PGP offers.) (4) could be done with PGP, but would go against the long-standing pattern of "sign the file" that most PGP tooling is ossified around. It also doesn't change the fact that PGP's signing defaults aren't great, that there's a huge tail of junk signing keys out there, and that to address those problems PyPI would need to be in the business of parsing PGP packets during package upload. That's just not a good use of anybody's time.
- opello 2y ago
  > having its own infrastructure This seems like a different brand of the keyserver network? > PyPI doesn't need to run or operationalize anything So it's not a new operational dependency because it's index metadata? That seems more like an implementation detail (aside from the imagined PGP keyserver dependency) that seems accommodatable given either system. > like the fact that PyPI doesn't need to perform any online operations to validate Sigstore's signatures I may be missing something subtle (or glaring) but "online operations" would be interactions with some other service or a non-PSF service? Or simply a service not-wholly-pypi? Regardless, the index seems like it must be a "verifier" for design consideration (2) from PEP 740 to hold, which would mean that the index must perform the verification step on the uploaded data--which seems inconsequentially different between an imagined PGP system (other than it would have to access the imagined PyPI keyserver) and sigstore/in-toto. > ... PyPI would need to be in the business of parsing PGP packets during package upload. But the sigstore analog is the JSON array of in-toto attestation statement objects.
  - woodruffw 2y ago
    > This seems like a different brand of the keyserver network? It serves a vaguely similar purpose, if that's what you mean. That shouldn't be surprising, since this is all PKI-shaped problems under the hood. To reiterate: the operational constraints here are (1) simplicity and reliability for PyPI, plus secure defaults for the signing scheme itself. Running a PGP keyserver would not offer (1), and PGP as an ecosystem does not offer (2). This is even before desired properties, like strong identity binding, which PGP cannot offer in its current form. > "online operations" would be interactions with some other service or a non-PSF service? Or simply a service not-wholly-pypi? In the PGP setting, that means PyPI would need to pull from a keyserver. That keyserver would need to be one that PyPI doesn't control in order for the threat model to be coherent. In the PEP 740 setting, PyPI does not need to pull any material from anywhere besides what the uploader is providing: the signatures in the attestations uploaded are signed with an attacked ephemeral signing certificate, which has a trusted publisher as its identity. That signing certificate can then be chained to an already established root of trust, in "normal" X.509 PKI fashion. You could approximate this design with PGP, but none of the primitives currently exist (or if they exist, are inoperational). > But the sigstore analog is the JSON array of in-toto attestation statement objects. Yes. Believe it or not, a big ugly JSON blob is simpler than dealing with PGP's mess of packet versions and formats.

by opello 2y ago

woodruffw 2y ago

(2) is addressed by Sigstore having its own infrastructure and a full-time rotation staff. PyPI doesn't need to run or operationalize anything, which is a significant relief compared to the prospect of having to operationalize a PGP keyserver with volunteer staffing. (I'm intentionally glossing over details here, like the fact that PyPI doesn't need to perform any online operations to validate Sigstore's signatures. The bottom line is that everything about it is operationally simpler and more modern than could be shaped out of the primitives PGP offers.) (4) could be done with PGP, but would go against the long-standing pattern of "sign the file" that most PGP tooling is ossified around. It also doesn't change the fact that PGP's signing defaults aren't great, that there's a huge tail of junk signing keys out there, and that to address those problems PyPI would need to be in the business of parsing PGP packets during package upload. That's just not a good use of anybody's time.

opello 2y ago
> having its own infrastructure This seems like a different brand of the keyserver network? > PyPI doesn't need to run or operationalize anything So it's not a new operational dependency because it's index metadata? That seems more like an implementation detail (aside from the imagined PGP keyserver dependency) that seems accommodatable given either system. > like the fact that PyPI doesn't need to perform any online operations to validate Sigstore's signatures I may be missing something subtle (or glaring) but "online operations" would be interactions with some other service or a non-PSF service? Or simply a service not-wholly-pypi? Regardless, the index seems like it must be a "verifier" for design consideration (2) from PEP 740 to hold, which would mean that the index must perform the verification step on the uploaded data--which seems inconsequentially different between an imagined PGP system (other than it would have to access the imagined PyPI keyserver) and sigstore/in-toto. > ... PyPI would need to be in the business of parsing PGP packets during package upload. But the sigstore analog is the JSON array of in-toto attestation statement objects.
- woodruffw 2y ago
  > This seems like a different brand of the keyserver network? It serves a vaguely similar purpose, if that's what you mean. That shouldn't be surprising, since this is all PKI-shaped problems under the hood. To reiterate: the operational constraints here are (1) simplicity and reliability for PyPI, plus secure defaults for the signing scheme itself. Running a PGP keyserver would not offer (1), and PGP as an ecosystem does not offer (2). This is even before desired properties, like strong identity binding, which PGP cannot offer in its current form. > "online operations" would be interactions with some other service or a non-PSF service? Or simply a service not-wholly-pypi? In the PGP setting, that means PyPI would need to pull from a keyserver. That keyserver would need to be one that PyPI doesn't control in order for the threat model to be coherent. In the PEP 740 setting, PyPI does not need to pull any material from anywhere besides what the uploader is providing: the signatures in the attestations uploaded are signed with an attacked ephemeral signing certificate, which has a trusted publisher as its identity. That signing certificate can then be chained to an already established root of trust, in "normal" X.509 PKI fashion. You could approximate this design with PGP, but none of the primitives currently exist (or if they exist, are inoperational). > But the sigstore analog is the JSON array of in-toto attestation statement objects. Yes. Believe it or not, a big ugly JSON blob is simpler than dealing with PGP's mess of packet versions and formats.