SPKI: Generate keys

[oncilla]

Add key generation capability for v2 to scion-pki tool.

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This change is 

[lukedirtwalker]

Reviewed 6 of 7 files at r1.
Reviewable status: 6 of 7 files reviewed, 3 unresolved discussions (waiting on @lukedirtwalker and @oncilla)

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go/tools/scion-pki/internal/v2/conf/as.go, line 132 at r1 (raw file):

		return err
	}
	if !a.Issuer.isZero() {

would it make sense to integrate the isZero check directly into validate? basically zero always validates. Would make the code here slightly more streamlined.

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go/tools/scion-pki/internal/v2/keys/cmd.go, line 28 at r1 (raw file):

	Long: `
'keys' can be used to generate all the necessary keys used in the SCION control plane PKI as well
as the AS master key.

do we still have an AS master key? didn't the terminology change?

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go/tools/scion-pki/internal/v2/keys/gen.go, line 110 at r1 (raw file):

	}
	// Check if out directory exists and if not create it.
	_, err = os.Stat(a.outDir)

Wait checking this for every key gen is a bit weird. This should be in the top level gen method.

[lukedirtwalker]

Reviewed 1 of 7 files at r1.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @oncilla)

[oncilla]

Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @lukedirtwalker and @scrye)

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go/tools/scion-pki/internal/v2/conf/as.go, line 132 at r1 (raw file):

Previously, lukedirtwalker (Lukas Vogel) wrote…

would it make sense to integrate the isZero check directly into validate? basically zero always validates. Would make the code here slightly more streamlined.

Done.

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go/tools/scion-pki/internal/v2/keys/cmd.go, line 28 at r1 (raw file):

Previously, lukedirtwalker (Lukas Vogel) wrote…

do we still have an AS master key? didn't the terminology change?

Yes. It is a symmetric key to derive the HF mac key for example.
It is not strictly part of the PKI, but somehow v1 supports it, so I left support in.

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go/tools/scion-pki/internal/v2/keys/gen.go, line 110 at r1 (raw file):

Previously, lukedirtwalker (Lukas Vogel) wrote…

Wait checking this for every key gen is a bit weird. This should be in the top level gen method.

Done.

[lukedirtwalker]

Reviewed 2 of 2 files at r2.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @lukedirtwalker and @scrye)

[lukedirtwalker]

Reviewed 1 of 1 files at r3.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @lukedirtwalker and @scrye)

[lukedirtwalker]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @scrye)