ENS avatar resolution fails when querying using an address

[TomAFrench]

Describe the bug

Resolving an ENS avatar with provider.getAvatar(nameOrAddress) using an ENS name works correctly, however if the address this name resolves to is passed then the avatar will be returned as null.

ethers.js/packages/providers/src.ts/base-provider.ts

Lines 1756 to 1779 in 0578a88

	async getAvatar(nameOrAddress: string): Promise<null | string> {
	let resolver: Resolver = null;
	if (isHexString(nameOrAddress)) {
	// Address; reverse lookup
	const address = this.formatter.address(nameOrAddress);
	const reverseName = address.substring(2).toLowerCase() + ".addr.reverse";
	const resolverAddress = await this._getResolver(reverseName);
	if (!resolverAddress) { return null; }
	resolver = new Resolver(this, resolverAddress, "_", address);
	} else {
	// ENS name; forward lookup
	resolver = await this.getResolver(nameOrAddress);
	if (!resolver) { return null; }
	}
	const avatar = await resolver.getAvatar();
	if (avatar == null) { return null; }
	return avatar.url;
	}

It looks to me like we're looking up the reverse record for the address provided and getting its resolver, we then query for the avatar field on here. This makes the assumption that the reverse and forwards resolvers are the same which is unlikely to be correct.

We also pass "_" as the name and so we use an incorrect namehash when pulling the avatar field.

Reproduction steps

Failing test case here: TomAFrench@50c7832

Fix

Based on the fact that we need the user's namehash in order to query the avatar, I think we have to go all they way up to the ENS name and then query using that.

I've made a PR to do this at #2582

Search Terms
ens, avatar

[TomAFrench]

Just noticed this link from when you added avatar support: https://gist.github.com/Arachnid/9db60bd75277969ee1689c8742b75182

To determine the avatar URI for an Ethereum address, the client MUST reverse-resolve the address by querying the ENS registry for the resolver of <address>.addr.reverse, where <address> is the lowercase hex-encoded Ethereum address, without leading '0x'. Then, the client calls .text(namehash('<address>.addr.reverse'), 'avatar') to retrieve the avatar URI for the address.

If a resolver is returned for the reverse record, but calling text causes a revert or returns an empty string, the client MUST call .name(namehash('<address>.addr.reverse')).

Looks like it's correct to attempt to find an avatar on the reverse resolver first however we're not passing the correct name (<address>.addr.reverse) in order to calculate the namehash so this will always fail currently.

[TomAFrench]

I've added an attempt to read an avatar from the reverse record, however we could save some calls if we create a getName method on Resolver so we don't need to look up the reverse record twice. I'm happy to do do this if you're fine with it.

[ricmoo]

I definitely need to look more into this and check with Nick too. This seems like it is a bug, but I want to make sure we do the right thing.

[ricmoo]

This should have been fixed in v5.6.0.

If you still have any problems, please re-open this issue.

Thanks! :)