IPFS Links and Validation¶

Many users will want to use decentralized file storage for their arbitrable DApps and will store Evidence and MetaEvidence on IPFS.

There are several things to keep in mind when using IPFS with Archon

IPFS Gateways¶

Most browsers do not currently support interacting with the ipfs network directly. Therefore, in order to fetch data from the ipfs network, we need to use an IPFS Gateway. Gateways are “standard” http URI’s that return data from the ipfs network based on the ipfs path.

It is important that you choose a gateway that you trust, as a malicious gateway can return tampered data. Please heed the warning below:

Warning

Archon considers data returned directly from a valid ipfs URI pre-validated. This is because hash validation is built into the protocol. As we need to use gateways to interact with the ipfs network at this time, MAKE SURE YOU SET A GATEWAY THAT YOU TRUST, or otherwise re-validate your ipfs hashes yourself.

The default gateway set is https://gateway.ipfs.io. This is the gateway provided by the Protocol Labs staff.

To set a custom gateway, use archon.setIpfsGateway(uri). See documentation on setting a gateway here

IPFS URIs¶

IPFS URIs are recognized in any of these formats:

/ipfs/Qm...../foo/bar
ipfs:/ipfs/Qm...../foo/bar
fs:/ipfs/Qm...../foo/bar

Gateway URI’s == Bad¶

It is not recommended that you link directly to an IPFS gateway as the fileURI in Evidence or MetaEvidence. It will not be able to be verified using Archon without a custom hashing function. The IPFS protocol does transformations on the data before hashing, therefore a hash can not be verified naively using the resulting IPFS multihash and the original file contents. In addition IPFS data should be able to be fetched by any gateway or node in the network, and a user should be able to use any gateway or node that they trust. Therefore hardcoding a gateway, which may not be trusted by the consumer, would require additional validation regardless.

Archon treats all http(s):// URI’s the same, and will try to validate the hash as if they were standard hashes.

Bad:

const evidenceJSON = {
  fileURI: "https://gateway.ipfs.io/ipfs/QmQhJRhvwgBPRdee18pK6QDECysFPuvuDLZMSeexdUfEiH"
}

archon.utils.validateFileFromURI(evidenceJSON.fileURI).then(data => {console.log(data.isValid)})
> false

Good:

const evidenceJSON = {
  fileURI: "/ipfs/QmQhJRhvwgBPRdee18pK6QDECysFPuvuDLZMSeexdUfEiH"
}

archon.setIpfsGateway('https://gateway.ipfs.io')
archon.utils.validateFileFromURI(evidenceJSON.fileURI).then(data => {console.log(data.isValid)})
> true

Not Recommended:

const ipfsHasher = data => {...}
const evidenceJSON = {
  fileURI: "https://gateway.ipfs.io/ipfs/QmQhJRhvwgBPRdee18pK6QDECysFPuvuDLZMSeexdUfEiH"
}

archon.utils.validateFileFromURI(
  evidenceJSON.fileURI,
  { customHashFn: ipfsHasher }
).then(data => {
  console.log(data.isValid)
})
> true