Fix hash mismatch error on matching link pointer #480
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On load, the default IPLD Link System checks the hash of loaded data against the given hash to assure that they match. The actual hash is calculated using the given link's `LinkPrototype.BuildLink`, and then is directly compared with the given link via `==`. Because the comparison is done by value, if the given link is a pointer the comparison fails which will result in false-positive hash mismatch error. To address this issue, instead of directly comparing objects using `==` check that their `Binary` value, i.e. their densest possible encoding, is equal. Add tests that assert the issue is fixed and works with existing link representations.
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| @@ -205,7 +205,7 @@ func (lsys *LinkSystem) Fill(lnkCtx LinkContext, lnk datamodel.Link, na datamode | |||
| // (Then do a bit of a jig to build a link out of it -- because that's what we do the actual hash equality check on.) | |||
| hash := hasher.Sum(nil) | |||
| lnk2 := lnk.Prototype().BuildLink(hash) | |||
| if lnk2 != lnk { | |||
| if lnk2.Binary() != lnk.Binary() { | |||
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should this be a bytes.Equal check?
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How come?
.Binary() returns string.
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hah, TIL bytes.Equal() is basically a string cmp: https://cs.opensource.google/go/go/+/refs/tags/go1.19.3:src/bytes/bytes.go;l=18-21
so I guess this is fine because we end up with the same thing
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On load, the default IPLD Link System checks the hash of loaded data against the given hash to assure that they match. The actual hash is calculated using the given link's
LinkPrototype.BuildLink, and then is directly compared with the given link via==.Because the comparison is done by value, if the given link is a pointer the comparison fails which will result in false-positive hash mismatch error.
To address this issue, instead of directly comparing objects using
==check that theirBinaryvalue, i.e. their densest possible encoding, is equal. Add tests that assert the issue is fixed and works with existing link representations.