[Cosigned] Fix publicKey unmarshal

[DennyHoang]

Signed-off-by: Denny Hoang [email protected]

Summary

Unmarshaling PublicKeys causes an error:

{"severity":"ERROR","timestamp":"2022-04-06T14:33:44.2084731Z","logger":"cosigned.config-store","caller":"configmap/store.go:148","message":"Error updating image-policies config \"config-image-policies\": \"failed to parse the entry <ENTRY> : math/big: cannot unmarshal \\\"2.7708706494268807e+76\\\" into a *big.Int\"","commit":"9008111","stacktrace":"<STACKTRACE>"}

Ticket Link

Fixes #1717

Notes

I am aware I am temporarily duplicating the function for parsing PEMs into the internal clusterimagepolicy_types file.
I have another branch that will address this alongside consolidating a lot of the clusterimagepolicy logic into the types file.

cc: @hectorj2f @vaikas @coyote240

[vaikas]

To make sure that we do not regress in the future, would you mind adding a test with public keys (existing only tests signing with Fulcio so this was not caught by the existing tests).
https://github.com/sigstore/cosign/blob/main/.github/workflows/kind-cluster-image-policy.yaml#L127

[codecov-commenter]

Codecov Report

Merging #1719 (d0e658f) into main (9008111) will decrease coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1719      +/-   ##
==========================================
- Coverage   29.26%   29.21%   -0.05%     
==========================================
  Files         141      141              
  Lines        8503     8502       -1     
==========================================
- Hits         2488     2484       -4     
- Misses       5742     5744       +2     
- Partials      273      274       +1     

Impacted Files	Coverage Δ
...econciler/clusterimagepolicy/clusterimagepolicy.go	64.00% <ø> (-0.21%)	⬇️
pkg/cosign/tuf/client.go	62.34% <0.00%> (-0.95%)	⬇️

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[vaikas]

Awesomesauce! Thanks!