feat: add blob/get (#1484)

Adds support for `blob/get` as defined in
storacha/specs#126

---------

Co-authored-by: Vasco Santos <santos.vasco10@gmail.com>
Co-authored-by: Irakli Gozalishvili <contact@gozala.io>

packages/capabilities/src/blob.js

@@ -137,6 +137,41 @@ export const list = capability({
   },
 })
 
+/**
+ * Capability can be used to get the stored Blob from the (memory)
+ * space identified by `with` field.
+ */
+export const get = capability({
+  can: 'space/blob/get/0/1',
+  /**
+   * DID of the (memory) space where Blob is stored.
+   */
+  with: SpaceDID,
+  nb: Schema.struct({
+    /**
+     * A multihash digest of the blob payload bytes, uniquely identifying blob.
+     */
+    digest: Schema.bytes(),
+  }),
+  derives: (claimed, delegated) => {
+    if (claimed.with !== delegated.with) {
+      return fail(
+        `Expected 'with: "${delegated.with}"' instead got '${claimed.with}'`
+      )
+    } else if (
+      delegated.nb.digest &&
+      !equals(delegated.nb.digest, claimed.nb.digest)
+    ) {
+      return fail(
+        `Link ${
+          claimed.nb.digest ? `${claimed.nb.digest}` : ''
+        } violates imposed ${delegated.nb.digest} constraint.`
+      )
+    }
+    return ok({})
+  },
+})
+
 // ⚠️ We export imports here so they are not omitted in generated typedefs
 // @see https://github.com/microsoft/TypeScript/issues/51548
 export { Schema }

packages/capabilities/src/types.ts

@@ -502,6 +502,7 @@ export type Blob = InferInvokedCapability<typeof BlobCaps.blob>
 export type BlobAdd = InferInvokedCapability<typeof BlobCaps.add>
 export type BlobRemove = InferInvokedCapability<typeof BlobCaps.remove>
 export type BlobList = InferInvokedCapability<typeof BlobCaps.list>
+export type BlobGet = InferInvokedCapability<typeof BlobCaps.get>
 export type ServiceBlob = InferInvokedCapability<typeof W3sBlobCaps.blob>
 export type BlobAllocate = InferInvokedCapability<typeof W3sBlobCaps.allocate>
 export type BlobAccept = InferInvokedCapability<typeof W3sBlobCaps.accept>
@@ -550,6 +551,15 @@ export interface BlobListSuccess extends ListResponse<BlobListItem> {}
 // TODO: make types more specific
 export type BlobListFailure = Ucanto.Failure
 
+// Blob get
+export interface BlobGetSuccess {
+  blob: { digest: Uint8Array; size: number }
+  cause: UnknownLink
+}
+
+// TODO: make types more specific
+export type BlobGetFailure = Ucanto.Failure
+
 // Blob allocate
 export interface BlobAllocateSuccess {
   size: number
@@ -902,6 +912,7 @@ export type ServiceAbilityArray = [
   BlobAdd['can'],
   BlobRemove['can'],
   BlobList['can'],
+  BlobGet['can'],
   ServiceBlob['can'],
   BlobAllocate['can'],
   BlobAccept['can'],

packages/upload-api/src/blob.js

@@ -1,6 +1,7 @@
 import { blobAddProvider } from './blob/add.js'
 import { blobListProvider } from './blob/list.js'
 import { blobRemoveProvider } from './blob/remove.js'
+import { blobGetProvider } from './blob/get.js'
 import * as API from './types.js'
 
 export { BlobNotFound } from './blob/lib.js'
@@ -13,5 +14,10 @@ export function createService(context) {
     add: blobAddProvider(context),
     list: blobListProvider(context),
     remove: blobRemoveProvider(context),
+    get: {
+      0: {
+        1: blobGetProvider(context),
+      },
+    },
   }
 }

packages/upload-api/src/blob/get.js

@@ -0,0 +1,21 @@
+import * as Server from '@ucanto/server'
+import * as Blob from '@web3-storage/capabilities/blob'
+import * as API from '../types.js'
+import { BlobNotFound } from './lib.js'
+import { decode } from 'multiformats/hashes/digest'
+
+/**
+ * @param {API.BlobServiceContext} context
+ * @returns {API.ServiceMethod<API.BlobGet, API.BlobGetSuccess, API.BlobGetFailure>}
+ */
+export function blobGetProvider(context) {
+  return Server.provide(Blob.get, async ({ capability }) => {
+    const { digest } = capability.nb
+    const space = Server.DID.parse(capability.with).did()
+    const res = await context.allocationsStorage.get(space, digest)
+    if (res.error && res.error.name === 'RecordNotFound') {
+      return Server.error(new BlobNotFound(decode(digest)))
+    }
+    return res
+  })
+}

packages/upload-api/src/types.ts

@@ -75,6 +75,9 @@ import {
   BlobRemove,
   BlobRemoveSuccess,
   BlobRemoveFailure,
+  BlobGet,
+  BlobGetSuccess,
+  BlobGetFailure,
   BlobAllocate,
   BlobAllocateSuccess,
   BlobAllocateFailure,
@@ -322,6 +325,11 @@ export interface Service extends StorefrontService, W3sService {
       add: ServiceMethod<BlobAdd, BlobAddSuccess, BlobAddFailure>
       remove: ServiceMethod<BlobRemove, BlobRemoveSuccess, BlobRemoveFailure>
       list: ServiceMethod<BlobList, BlobListSuccess, BlobListFailure>
+      get: {
+        0: {
+          1: ServiceMethod<BlobGet, BlobGetSuccess, BlobGetFailure>
+        }
+      }
     }
   }
   plan: {

packages/upload-api/src/types/blob.ts

@@ -10,6 +10,7 @@ import {
   Multihash,
   BlobListItem,
   BlobRemoveSuccess,
+  BlobGetSuccess,
 } from '@web3-storage/capabilities/types'
 
 import { RecordKeyConflict, ListResponse } from '../types.js'
@@ -21,7 +22,7 @@ export interface AllocationsStorage {
   get: (
     space: DID,
     blobMultihash: Multihash
-  ) => Promise<Result<BlobGetOutput, Failure>>
+  ) => Promise<Result<BlobGetSuccess, Failure>>
   exists: (
     space: DID,
     blobMultihash: Multihash
@@ -59,11 +60,6 @@ export interface BlobAddInput {
 
 export interface BlobAddOutput extends Omit<BlobAddInput, 'space' | 'cause'> {}
 
-export interface BlobGetOutput {
-  blob: { digest: Uint8Array; size: number }
-  cause: UnknownLink
-}
-
 export interface BlobsStorage {
   has: (content: Multihash) => Promise<Result<boolean, Failure>>
   createUploadUrl: (

packages/upload-api/test/handlers/web3.storage.js

@@ -1,10 +1,7 @@
 import * as API from '../../src/types.js'
 import { equals } from 'uint8arrays'
-import { create as createLink } from 'multiformats/link'
 import { Absentee } from '@ucanto/principal'
-import { Digest } from 'multiformats/hashes/digest'
 import { sha256 } from 'multiformats/hashes/sha2'
-import { code as rawCode } from 'multiformats/codecs/raw'
 import { Assert } from '@web3-storage/content-claims/capability'
 import * as BlobCapabilities from '@web3-storage/capabilities/blob'
 import * as W3sBlobCapabilities from '@web3-storage/capabilities/web3.storage/blob'
@@ -225,7 +222,7 @@ export const test = {
       }
 
       // second blob allocate invocation
-      const reallocation = await await W3sBlobCapabilities.allocate
+      const reallocation = await W3sBlobCapabilities.allocate
         .invoke({
           issuer: context.id,
           audience: context.id,
@@ -604,10 +601,6 @@ export const test = {
     const multihash = await sha256.digest(data)
     const digest = multihash.bytes
     const size = data.byteLength
-    const content = createLink(
-      rawCode,
-      new Digest(sha256.code, 32, digest, digest)
-    )
 
     // create service connection
     const connection = connect({
@@ -682,7 +675,7 @@ export const test = {
       equals(
         // @ts-expect-error nb unknown
         delegation.capabilities[0].nb.content.digest,
-        content.multihash.bytes
+        digest
       )
     )
     // @ts-expect-error nb unknown

packages/upload-client/src/blob.js

@@ -423,3 +423,52 @@ export async function remove(
 
   return result.out
 }
+
+/**
+ * Gets a stored Blob file by digest.
+ *
+ * @param {import('./types.js').InvocationConfig} conf Configuration
+ * for the UCAN invocation. An object with `issuer`, `with` and `proofs`.
+ *
+ * The `issuer` is the signing authority that is issuing the UCAN
+ * invocation(s). It is typically the user _agent_.
+ *
+ * The `with` is the resource the invocation applies to. It is typically the
+ * DID of a space.
+ *
+ * The `proofs` are a set of capability delegations that prove the issuer
+ * has the capability to perform the action.
+ *
+ * The issuer needs the `blob/get/0/1` delegated capability.
+ * @param {import('multiformats').MultihashDigest} multihash of the blob
+ * @param {import('./types.js').RequestOptions} [options]
+ */
+export async function get(
+  { issuer, with: resource, proofs, audience },
+  multihash,
+  options = {}
+) {
+  /* c8 ignore next */
+  const conn = options.connection ?? connection
+  const result = await BlobCapabilities.get
+    .invoke({
+      issuer,
+      /* c8 ignore next */
+      audience: audience ?? servicePrincipal,
+      with: SpaceDID.from(resource),
+      nb: {
+        digest: multihash.bytes,
+      },
+      proofs,
+      nonce: options.nonce,
+    })
+    .execute(conn)
+
+  if (!result.out.ok) {
+    throw new Error(`failed ${BlobCapabilities.get.can} invocation`, {
+      cause: result.out.error,
+    })
+  }
+
+  return result.out
+}

packages/upload-client/src/types.ts

@@ -39,6 +39,9 @@ import {
   BlobList,
   BlobListSuccess,
   BlobListFailure,
+  BlobGet,
+  BlobGetSuccess,
+  BlobGetFailure,
   IndexAdd,
   IndexAddSuccess,
   IndexAddFailure,
@@ -106,6 +109,9 @@ export type {
   BlobList,
   BlobListSuccess,
   BlobListFailure,
+  BlobGet,
+  BlobGetSuccess,
+  BlobGetFailure,
   IndexAdd,
   IndexAddSuccess,
   IndexAddFailure,
@@ -161,6 +167,11 @@ export interface Service extends StorefrontService {
       add: ServiceMethod<BlobAdd, BlobAddSuccess, BlobAddFailure>
       remove: ServiceMethod<BlobRemove, BlobRemoveSuccess, BlobRemoveFailure>
       list: ServiceMethod<BlobList, BlobListSuccess, BlobListFailure>
+      get: {
+        0: {
+          1: ServiceMethod<BlobGet, BlobGetSuccess, BlobGetFailure>
+        }
+      }
     }
     index: {
       add: ServiceMethod<IndexAdd, IndexAddSuccess, IndexAddFailure>