more strict validation (#1)

in an attempt to preempt problems with non-deterministic (de-)serialization.

lib/feed-v1/validation.js

@@ -36,7 +36,12 @@ function validateShape(msg) {
 
 function validateWho(msg) {
   try {
-    base58.decode(msg.metadata.who)
+    const whoBuf = base58.decode(msg.metadata.who)
+    if (whoBuf.length !== 32) {
+      return new Error(
+        `invalid message: decoded "who" should be 32 bytes but was ${whoBuf.length}`
+      )
+    }
   } catch (err) {
     return new Error('invalid message: must have "who" as base58 string')
   }
@@ -44,7 +49,12 @@ function validateWho(msg) {
 
 function validateMsgHash(str) {
   try {
-    base58.decode(str)
+    const hashBuf = Buffer.from(base58.decode(str))
+    if (hashBuf.length !== 16) {
+      return new Error(
+        `invalid message: decoded hash should be 16 bytes but was ${hashBuf.length}`
+      )
+    }
   } catch (err) {
     return new Error(
       `invalid message: msgHash ${str} should have been a base58 string`
@@ -52,21 +62,30 @@ function validateMsgHash(str) {
   }
 }
 
+function validateSize(msg) {
+  const {
+    metadata: { size },
+  } = msg
+  if (!Number.isSafeInteger(size) || size < 0) {
+    return new Error(`invalid message: "size" should be an unsigned integer`)
+  }
+}
+
 function validateSignature(msg) {
   const { sig } = msg
   if (typeof sig !== 'string') {
     return new Error('invalid message: must have sig as a string')
   }
+  let sigBuf
   try {
-    base58.decode(sig)
-  } catch (err) {
-    return new Error('invalid message: sig must be a base58 string')
-  }
-  const sigBuf = Buffer.from(base58.decode(sig))
+    sigBuf = Buffer.from(base58.decode(sig))
     if (sigBuf.length !== 64) {
       // prettier-ignore
       return new Error('invalid message: sig should be 64 bytes but was ' + sigBuf.length + ', on feed: ' + msg.metadata.who);
     }
+  } catch (err) {
+    return new Error('invalid message: sig must be a base58 string')
+  }
 
   const publicKeyBuf = Buffer.from(base58.decode(msg.metadata.who))
   const signableBuf = Buffer.from(stringify(msg.metadata), 'utf8')
@@ -93,9 +112,9 @@ function validateTangle(msg, tangle, tangleId) {
     // prettier-ignore
     return new Error('invalid message: prev must be an array, on feed: ' + msg.metadata.who);
   }
-  if (typeof depth !== 'number') {
+  if (!Number.isSafeInteger(depth) || depth <= 0) {
     // prettier-ignore
-    return new Error('invalid message: depth must be a number, on feed: ' + msg.metadata.who);
+    return new Error('invalid message: depth must be a positive integer, on feed: ' + msg.metadata.who);
   }
   if (tangle.isFeed()) {
     const { type, who } = tangle.getFeed()
@@ -202,6 +221,7 @@ function validate(msg, tangle, msgHash, rootHash) {
   let err
   if ((err = validateShape(msg))) return err
   if ((err = validateWho(msg))) return err
+  if ((err = validateSize(msg))) return err
   if (tangle.size() === 0) {
     if ((err = validateTangleRoot(msg, msgHash, rootHash))) return err
   } else {

protospec.md

@@ -7,11 +7,11 @@ interface Msg {
   content: any | null, // any object, or null
   metadata: {
     hash: ContentHash, // blake3 hash of the `content` object serialized
-    size: number, // byte size of the `content` object serialized
+    size: number, // byte size (unsigned integer) of the `content` object serialized
     tangles: {
       // for each tangle this msg belongs to, identified by the tangle's root
       [rootMsgHash: string]: {
-        depth: number, // maximum distance from this msg to the root
+        depth: number, // maximum distance (positive integer) from this msg to the root
         prev: Array<MsgHash>, // list of msg hashes of existing msgs
       },
     },