Enhancement for attached signatures

signature_body.md

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+# 77-signature_body: Attached signatures
+
+Utilise signature body in allow list for attached signatures. 
+
+<!--
+This is the title of your enhancement.  Keep it short, simple, and descriptive.  A good
+title can help communicate what the enhancement is and should be considered as part of
+any review.
+-->
+
+<!--
+A table of contents is helpful for quickly jumping to sections of a enhancement and for
+highlighting any additional information provided beyond the standard enhancement
+template.
+-->
+
+<!-- toc -->
+- [Release Signoff Checklist](#release-signoff-checklist)
+- [Summary](#summary)
+- [Motivation](#motivation)
+  - [Goals](#goals)
+  - [Non-Goals](#non-goals)
+- [Proposal](#proposal)
+  - [User Stories (optional)](#user-stories-optional)
+    - [Story 1](#story-1)
+    - [Story 2](#story-2)
+  - [Notes/Constraints/Caveats (optional)](#notesconstraintscaveats-optional)
+  - [Risks and Mitigations](#risks-and-mitigations)
+- [Design Details](#design-details)
+  - [Test Plan](#test-plan)
+  - [Upgrade / Downgrade Strategy](#upgrade--downgrade-strategy)
+- [Drawbacks](#drawbacks)
+- [Alternatives](#alternatives)
+- [Infrastructure Needed (optional)](#infrastructure-needed-optional)
+<!-- /toc -->
+
+## Release Signoff Checklist
+
+<!--
+**ACTION REQUIRED:** In order to merge code into a release, there must be an
+issue in [keylime/enhancements] referencing this enhancement and targeting a release**.
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+For enhancements that make changes to code or processes/procedures in core
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+Signoff checklist to be completed.
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+- [ ] Enhancement issue in release milestone, which links to pull request in [keylime/enhancements]
+- [ ] Core members have approved the issue with the label `in-progress`
+- [ ] Design details are appropriately documented
+- [ ] Test plan is in place
+- [ ] User-facing documentation has been created in [keylime/keylime-docs]
+
+<!--
+**Note:** This checklist is iterative and should be reviewed and updated every time this enhancement is being considered for a milestone.
+-->
+
+## Summary
+
+This proposal introduces a method to sign over the body of an allow-list
+and then attach a signature and public key ID or X509 certificate.
+
+It uses the same manifest layout as supply chain projects [intoto](https://in-toto.io/)
+and [The update framework](https://theupdateframework.io/).
+<!--
+This section is incredibly important for producing high quality user-focused
+documentation such as release notes or a development roadmap.  It should be
+possible to collect this information before implementation begins in order to
+avoid requiring implementers to split their attention between writing release
+notes and implementing the feature itself. Reviewers
+should help to ensure that the tone and content of the `Summary` section is
+useful for a wide audience.
+
+A good summary is probably at least a paragraph in length.
+-->
+
+## Motivation
+
+The current implementation leverages seperate keys to the list itself. While
+suitable for some cases, it is also useful to have a single package where the
+list and the signature travel in the same payload.
+
+<!--
+This section is for explicitly listing the motivation, goals and non-goals of
+this enhancement.  Describe why the change is important and the benefits to users.
+-->
+
+### Proposal
+
+User produces a cryptographic signature by 'passing over' the body of an allow/exclude
+list. The signature and public key id (sha256 hash of pubKey), or an X509 cert (base64)
+are then attached to the allowlist.
+
+The verifier upon discovery of a `"signed"` body and `"signatures"` keys, will validate
+the `signed` section.
+
+This proposal borrows from the existing signing conventions
+established by the [intoto project](https://github.com/in-toto/docs/blob/master/in-toto-spec.md#4-document-formats).
+
+```json
+{
+    "signatures": [
+        {
+         "keyid": <KEYID>,
+         "keytype" : <KEYTYPE>,
+         "sig": <SIGNATURE>
+        }
+    ],
+    "signed": {
+        "meta": {
+        "version": 872
+        },
+        "release": 774.75,
+        "hashes": {
+        ",'Sr": []
+        },
+        "excludes": [],
+        "keyrings": {
+        "}": "xxx"
+        },
+        "ima": {
+        "ignored_keyrings": [],
+        "log_hash_alg": "xxx"
+        },
+        "ima-buf": {
+        "": "xxx"
+        },
+        "verification-keys": []
+    }
+}
+```
+#### signatures
+
+The `signatures`` section lists there json keys:
+
+##### keyid
+
+* keyid: The keyid can be one of two. 
+1. A sha256 hash of a public key (therefore acting as a map). This allows an out-of-band public key
+2. A base64 encoded X509 v3 certificate in PEM format. This is in-band and can be chained to CA for identity.
+
+For the first method (sha256 hash) the public key will be stored within the verifier at:
+
+`/var/lib/keylime/signing_keys/{hash-of-pubkey}.pkey`
+
+For the second method a store is not required, the public key can be extracted from the X509 certificate
+
+For a later stage, we can look to have a chain verification from the the signing cert to a CA.
+
+##### keytype
+
+keytype is a string denoting a public key signature system.
+
+We define three key types at present: "rsa", "ed25519", and "ecdsa".
+
+##### sig
+
+The `sig` section is a base64 encoded signature (see signed below for details around signature generation)
+
+#### signed
+
+The signed body contains all content that is to be signed.
+
+The signature functionality, extracts all characters (including whitespace) and encodes it to a base64 string
+
+A signature is then generated by signing the base64 string. This is then placed into `sig` section within the
+`signatures` body.
+
+### verification
+
+The verification flow, will play out as follows
+
+1. The verifier will check to see if the signature and signed bodies exist
+2. The verifier will either decode the x509 certificate and extract the public key, or will capture
+   the sha256 digest and load the mapped key from `/var/lib/keylime/signing_keys/{hash-of-pubkey}.pkey`
+3. The verifier will then perform a verification of the signature against the `signed` body
+4. If any of the steps above fail, then a verifier API will return a failure code.
+
+### Non-Goals
+
+<!--
+What is out of scope for this enhancement?  Listing non-goals helps to focus discussion
+and make progress.
+-->
+No immediate plan to implement signing into the tenant and no extra flags are required,
+the verifier will check for the signature and signed body and only attempt to validate
+if they exist.
+
+### User Stories (optional)
+
+<!--
+Detail the things that people will be able to do if this enhancement is implemented.
+Include as much detail as possible so that people can understand the "how" of
+the system.  The goal here is to make this feel real for users without getting
+bogged down.
+-->
+
+I as a user would like to have attached signatures.
+
+#### Story 1
+
+#### Story 2
+
+### Notes/Constraints/Caveats (optional)
+
+<!--
+What are the caveats to the proposal?
+What are some important details that didn't come across above.
+Go in to as much detail as necessary here.
+This might be a good place to talk about core concepts and how they relate.
+-->
+
+### Risks and Mitigations
+
+<!--
+What are the risks of this proposal and how do we mitigate.  Think broadly.
+For example, consider both security and how this will impact the larger
+enhancement ecosystem.
+
+How will security be reviewed and by whom?
+-->
+
+## Design Details
+
+<!--
+This section should contain enough information that the specifics of your
+change are understandable.  This may include API specs (though not always
+required) or even code snippets.  If there's any ambiguity about HOW your
+proposal will be implemented, this is the place to discuss them.
+-->
+
+### Test Plan
+
+<!--
+**Note:** *Not required until targeted at a release.*
+
+Consider the following in developing a test plan for this enhancement:
+- Will there be e2e and integration tests, in addition to unit tests?
+- How will it be tested in isolation vs with other components?
+
+No need to outline all of the test cases, just the general strategy.  Anything
+that would count as tricky in the implementation and anything particularly
+challenging to test should be called out.
+
+All code is expected to have adequate tests (eventually with coverage
+expectations).
+-->
+
+Unit test will be provided to verify serialization of json input and 
+signature verification.
+
+### Upgrade / Downgrade Strategy
+
+<!--
+If applicable, how will the component be upgraded and downgraded? Make sure
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+
+Consider the following in developing an upgrade/downgrade strategy for this enhancement
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+
+### Dependency requirements
+
+<!--
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+If the package is not available in the supported Operated systems, the PR will not be merged into master. 
+
+Adding the package in `requirements.txt` is not sufficent for master which is where we tag releases from. 
+
+You may however be able to work within an experimental branch until a package is made available. If this is
+the case, please outline it in this enhancement.
+
+-->
+
+No new dependencies will be required. 
+
+## Drawbacks
+
+<!--
+Why should this enhancement _not_ be implemented?
+-->
+
+## Alternatives
+
+<!--
+What other approaches did you consider and why did you rule them out?  These do
+not need to be as detailed as the proposal, but should include enough
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+-->
+
+## Infrastructure Needed (optional)
+
+<!--
+Use this section if you need things infrastructure related specific to your enhancement.  Examples include a
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