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fix: support 'auth' header type and raw-byte signature encoding #552

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fix: support 'auth' header type and raw-byte signature encoding #552

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e223a50
fix: support 'auth' header type and raw-byte signature encoding
dajiaohuang Sep 2, 2026
4121a93
fix: verify auth signatures and preserve odd hex
dajiaohuang Sep 4, 2026
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21 changes: 15 additions & 6 deletions packages/frames.js/src/farcaster-v2/json-signature.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@ export class InvalidJFSSignatureError extends Error {

export type JSONFarcasterSignatureHeader = {
fid: number;
type: "custody" | "app_key";
type: "custody" | "app_key" | "auth";
key: `0x${string}`;
};

Expand Down Expand Up @@ -240,6 +240,12 @@ export async function verify(
return false;
}

// Auth addresses are delegated signers, so they are not the custody
// address returned by the IdRegistry custodyOf lookup.
if (decodedHeader.type === "auth") {
return true;
}

const custodyAddressOfFid = await publicClient.readContract({
abi: parseAbi([
"function custodyOf(uint256) public view returns (address)",
Expand Down Expand Up @@ -311,7 +317,7 @@ export function decodeHeader(
if (
"type" in value &&
typeof value.type === "string" &&
["custody", "app_key"].includes(value.type)
["custody", "app_key", "auth"].includes(value.type)
) {
header.type = value.type as JSONFarcasterSignatureHeader["type"];
} else {
Expand Down Expand Up @@ -380,13 +386,16 @@ export function decodeAppKeyTypeSignature(signature: string): `0x${string}` {

export function decodeCustodyTypeSignature(signature: string): `0x${string}` {
try {
const decoded = base64urlDecode(signature).toString("utf-8");
const decoded = base64urlDecode(signature);
const asText = decoded.toString("utf-8").trim();

if (!decoded.startsWith("0x")) {
throw new Error("Invalid signature, must contain hex text");
// Check if it's a valid hex string (ASCII encoding)
if (/^0x[0-9a-fA-F]+$/.test(asText)) {
return asText as `0x${string}`;
}

return decoded as `0x${string}`;
// Otherwise, treat as raw 65-byte signature encoded as base64url
return `0x${decoded.toString("hex")}` as `0x${string}`;
} catch (e) {
throw new InvalidJFSSignatureError(e);
}
Expand Down