Sanitize multihash input to Exporter.

package.json

@@ -54,10 +54,12 @@
   },
   "dependencies": {
     "block-stream2": "^1.1.0",
+    "bs58": "^3.0.0",
     "debug": "^2.2.0",
     "field-trip": "0.0.2",
     "ipfs-merkle-dag": "^0.5.0",
     "ipfs-unixfs": "^0.1.0",
+    "is-ipfs": "^0.2.0",
     "isstream": "^0.1.2",
     "readable-stream": "^1.1.13",
     "run-series": "^1.1.4",

src/exporter.js

@@ -3,6 +3,8 @@
 const debug = require('debug')
 const log = debug('exporter')
 log.err = debug('exporter:error')
+const isIPFS = require('is-ipfs')
+const bs58 = require('bs58')
 const UnixFS = require('ipfs-unixfs')
 const series = require('run-series')
 const Readable = require('readable-stream').Readable
@@ -19,6 +21,14 @@ function Exporter (hash, dagService, options) {
     return new Exporter(hash, dagService, options)
   }
 
+  // Sanitize hash.
+  if (!isIPFS.multihash(hash)) {
+    throw new Error('not valid multihash')
+  }
+  if (Buffer.isBuffer(hash)) {
+    hash = bs58.encode(hash)
+  }
+
   Readable.call(this, { objectMode: true })
 
   this.options = options || {}