feat(controlplane): CAS download endpoint

[migmartri]

Enables two endpoints in the controlplane APIs GetDownloadURL (gRPC) and /download (http)

GetDownloadURL (gRPC)

The first endpoint will be used by any client to retrieve the CAS download URL, this could be useful for clients as UIs, where a downloadURL could be generated on-demand after an user action.

The returned link includes a temporary download token, valid for only 10 seconds.

$ grpcurl --plaintext -H "authorization: Bearer $TOKEN" -d '{"digest": "sha256:0173a54b14c1f163c3015c9ddd32c781f6074a32986b7bcd5448a719f4e285aa"}' localhost:9000 controlplane.v1.CASRedirectService.GetDownloadURL | jq
{
  "result": {
    "url": "http://0.0.0.0:8001/download/sha256:0173a54b14c1f163c3015c9ddd32c781f6074a32986b7bcd5448a719f4e285aa?t=eyJhbGciOiJFUzUxMiIsInR5cCI6IkpXVCJ9.REDACTED"
  }
}

/download/sha256:[hex] (http)

This endpoint can be used to share links to download items in the CAS. By accessing the link the handler will

• require authentication sending the user to do a oauth roundtrip if needed
• Generate a short-lived download URL using the same logic as GetDownloadURL
• redirect the user to such url

You can see it in action in both a browser below

download.mp4

Refs #293

[migmartri]

note: This change will require users to update their CLIs otherwise their tokens will expire constantly.

I decided to go this way because

• It just affects operators CLI, not the attestation CLI
• Doing the opposite, meaning making long-lived default while short-lived optional is not good practice.
• We are still pre-1.0 so we do not guarantee backwards compatibility.
• I do not think we can detect the version of the CLI yet, so there is no way to show a warning message to the user.

Please let me know if you have any objection on this breaking change.

[danlishka]

Can you please elaborate on "It just affects operators CLI, not the attestation CLI"?
You mean that it does not affect RobotAccount auth based calls?

[migmartri]

Correct

[danlishka]

LGTM

[danlishka]

Why 10 seconds? Just to be on the safe side?

[migmartri]

We need now a longer timeout since the HTTP endpoint handler now will check if the cas backend is valid in some cases, that takes some time.

We have currently configured 10 seconds in the similar gRPC endpoints so I thought of using the same.

[danlishka]

Can you please elaborate on "It just affects operators CLI, not the attestation CLI"?
You mean that it does not affect RobotAccount auth based calls?