SPKI: TRC signature combination

[oncilla]

Add support for combining TRC signature parts into a final signed TRC.

The version to sign can be provided via command line flag.
If no version is specified, the tool searches the newest TRC
configuration file and uses its version.

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This change is 

[lukedirtwalker]

Reviewed 10 of 10 files at r1.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @oncilla)

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go/tools/scion-pki/internal/v2/trcs/combine.go, line 69 at r1 (raw file):

		for fname, part := range parts[isd] {
			if !bytes.Equal(proto.Signed.EncodedTRC, part.EncodedTRC) {
				pkicmn.QuietPrint("Ignoring signed in %s. Payload is different\n", fname)

isn't a continue needed here? why isn't that catched by a unit test?

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

}

func (v validator) Validate(combined map[addr.ISD]signedMeta) error {

I think a short comment about what this validates would be helpful.

[oncilla]

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

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go/tools/scion-pki/internal/v2/trcs/combine.go, line 69 at r1 (raw file):

Previously, lukedirtwalker (Lukas Vogel) wrote…

isn't a continue needed here? why isn't that catched by a unit test?

ugh, right. Great catch.
This branch was never executed in the test. Fixed now.

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

Previously, lukedirtwalker (Lukas Vogel) wrote…

I think a short comment about what this validates would be helpful.

Done.

[lukedirtwalker]

Reviewed 3 of 3 files at r2.
Reviewable status: complete! all files reviewed, all discussions resolved