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feat: Generate Space proofs on the fly, on
access/claim (storacha#1555
) The bulk of the work for storacha/project-tracking#125. This together with [`w3ui` calling `access/claim` on page load](storacha/w3ui#644) will make new spaces appear on the page without logging out. --- ## The Strategy * On `access/confirm`, where we previously created a `*`/`ucan:*` delegation with proofs for each space, we now create one with no proofs. This delegation technically provides no capability, but serves as a signal in `access/claim`. * During `access/claim`, we look for the Agent's `*`/`ucan:*` delegations in the store, and translate them on the fly into ones containing proofs for the relevant spaces. This is legitimate, because `*`/`ucan:*` means the Agent has been granted access to anything the Account can do, it just doesn't have the proofs that Account can do anything yet. We're just putting 2 and 2 together. ## Remaining * [x] We don't validate the `*`/`ucan:*` delegation before recreating it. If `access/confirm` doesn't create an attestation, `access/claim` will still happily make one for its new delegation. That's a (minor?) security issue. If the delegation is in our store, we can probably trust it, but better to care about the attestation. * [x] Tests for all of this. --------- Co-authored-by: Alan Shaw <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,37 +1,164 @@ | ||
| import * as Server from '@ucanto/server' | ||
| import * as Access from '@web3-storage/capabilities/access' | ||
| import * as UCAN from '@ipld/dag-ucan' | ||
| import * as API from '../types.js' | ||
| import * as delegationsResponse from '../utils/delegations-response.js' | ||
| import { createSessionProofs } from './confirm.js' | ||
|
|
||
| /** | ||
| * @param {API.AccessClaimContext} ctx | ||
| */ | ||
| export const provide = (ctx) => | ||
| Server.provide(Access.claim, (input) => claim(input, ctx)) | ||
|
|
||
| /** | ||
| * Checks if the given Principal is an Account. | ||
| * @param {API.Principal} principal | ||
| * @returns {principal is API.Principal<API.DID<'mailto'>>} | ||
| */ | ||
| const isAccount = (principal) => principal.did().startsWith('did:mailto:') | ||
|
|
||
| /** | ||
| * Returns true when the delegation has a `ucan:*` capability. | ||
| * @param {API.Delegation} delegation | ||
| * @returns boolean | ||
| */ | ||
| const isUCANStar = (delegation) => | ||
| delegation.capabilities.some((capability) => capability.with === 'ucan:*') | ||
|
|
||
| /** | ||
| * Returns true when the capability is a `ucan/attest` capability for the given | ||
| * signer. | ||
| * | ||
| * @param {API.Capability} capability | ||
| * @returns {capability is API.UCANAttest} | ||
| */ | ||
| const isUCANAttest = (capability) => capability.can === 'ucan/attest' | ||
|
|
||
| /** | ||
| * @param {API.Input<Access.claim>} input | ||
| * @param {API.AccessClaimContext} ctx | ||
| * @returns {Promise<API.Result<API.AccessClaimSuccess, API.AccessClaimFailure>>} | ||
| */ | ||
| export const claim = async ( | ||
| { invocation }, | ||
| { delegationsStorage: delegations } | ||
| ) => { | ||
| export const claim = async ({ invocation }, { delegationsStorage, signer }) => { | ||
| const claimedAudience = invocation.capabilities[0].with | ||
| const claimedResult = await delegations.find({ audience: claimedAudience }) | ||
| if (claimedResult.error) { | ||
| const storedDelegationsResult = await delegationsStorage.find({ | ||
| audience: claimedAudience, | ||
| }) | ||
|
|
||
| if (storedDelegationsResult.error) { | ||
| return { | ||
| error: { | ||
| name: 'AccessClaimFailure', | ||
| message: 'error finding delegations', | ||
| cause: claimedResult.error, | ||
| cause: storedDelegationsResult.error, | ||
| }, | ||
| } | ||
| } | ||
|
|
||
| const delegationsToReturnByCid = Object.fromEntries( | ||
| storedDelegationsResult.ok.map((delegation) => [delegation.cid, delegation]) | ||
| ) | ||
|
|
||
| // Find any attested ucan:* delegations and replace them with fresh ones. | ||
| for (const delegation of storedDelegationsResult.ok) { | ||
| // Ignore delegations that aren't attestations, and ours. | ||
| const attestCap = delegation.capabilities.find(isUCANAttest) | ||
| if (!(attestCap && attestCap.with === signer.did())) continue | ||
|
|
||
| // Ignore invalid attestations. | ||
| const valid = | ||
| (await UCAN.verifySignature(delegation.data, signer)) && | ||
| !UCAN.isTooEarly(delegation.data) && | ||
| !UCAN.isExpired(delegation.data) | ||
| if (!valid) continue | ||
|
|
||
| // Ignore attestations of delegations we don't have. | ||
| const attestedCid = attestCap.nb.proof | ||
| const attestedDelegation = delegationsToReturnByCid[attestedCid.toString()] | ||
| if (!(attestedDelegation && isUCANStar(attestedDelegation))) continue | ||
|
|
||
| // Create new session proofs for the attested delegation. | ||
| const sessionProofsResult = await createSessionProofsForLogin( | ||
| attestedDelegation, | ||
| delegationsStorage, | ||
| signer | ||
| ) | ||
|
|
||
| // If something went wrong, bail on the entire invocation with the error. | ||
| // NB: This breaks out of the loop, because if this fails at all, we don't | ||
| // need to keep looking. | ||
| if (sessionProofsResult.error) { | ||
| return { | ||
| error: { | ||
| name: 'AccessClaimFailure', | ||
| message: 'error creating session proofs', | ||
| cause: sessionProofsResult.error, | ||
| }, | ||
| } | ||
| } | ||
|
|
||
| // Delete the ones we're replacing... | ||
| delete delegationsToReturnByCid[delegation.cid.toString()] | ||
| delete delegationsToReturnByCid[attestedCid.toString()] | ||
|
|
||
| // ...and add the new ones. | ||
| for (const proof of sessionProofsResult.ok) { | ||
| delegationsToReturnByCid[proof.cid.toString()] = proof | ||
| } | ||
| } | ||
|
|
||
| return { | ||
| ok: { | ||
| delegations: delegationsResponse.encode(claimedResult.ok), | ||
| delegations: delegationsResponse.encode( | ||
| Object.values(delegationsToReturnByCid) | ||
| ), | ||
| }, | ||
| } | ||
| } | ||
|
|
||
| /** | ||
| * @param {API.Delegation} loginDelegation | ||
| * @param {API.DelegationsStorage} delegationsStorage | ||
| * @param {API.Signer} signer | ||
| * @returns {Promise<API.Result<API.Delegation[], API.AccessClaimFailure>>} | ||
| */ | ||
| async function createSessionProofsForLogin( | ||
| loginDelegation, | ||
| delegationsStorage, | ||
| signer | ||
| ) { | ||
| // These should always be Accounts (did:mailto:), but if one's not, skip it. | ||
| if (!isAccount(loginDelegation.issuer)) return { ok: [] } | ||
|
|
||
| const accountDelegationsResult = await delegationsStorage.find({ | ||
| audience: loginDelegation.issuer.did(), | ||
| }) | ||
|
|
||
| if (accountDelegationsResult.error) { | ||
| return { | ||
| error: { | ||
| name: 'AccessClaimFailure', | ||
| message: 'error finding delegations', | ||
| cause: accountDelegationsResult.error, | ||
| }, | ||
| } | ||
| } | ||
|
|
||
| return { | ||
| ok: await createSessionProofs({ | ||
| service: signer, | ||
| account: loginDelegation.issuer, | ||
| agent: loginDelegation.audience, | ||
| facts: loginDelegation.facts, | ||
| capabilities: loginDelegation.capabilities, | ||
| // We include all the delegations to the account so that the agent will | ||
| // have delegation chains to all the delegated resources. | ||
| // We should actually filter out only delegations that support delegated | ||
| // capabilities, but for now we just include all of them since we only | ||
| // implement sudo access anyway. | ||
| delegationProofs: accountDelegationsResult.ok, | ||
| expiration: Infinity, | ||
| }), | ||
| } | ||
| } |
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