check signatures with and without query - fix #1036

@Oneric explained:

> Spec says query params must be included in the signature; Mastodon
> being Mastodon used to always exclude it though and for
> compatibility everyone followed this. At some point GtS decided to
> follow spec instead which caused interop issues, but succeeded in
> getting Mastodon (and others like *oma) to accept incoming requests
> with (and also still without) query params though outgoing requests
> remaing query-param-free. Some still only accept query-param-less
> requests though and GtS uses a retry mechanism to resend any request
> failing with 401 with an query-parama-less signature once. (Also
> see:
> https://docs.gotosocial.org/en/latest/federation/http_signatures/ )
>
> So for incoming requests both versions need to be checked. For
> outgoing requests, unless you want to jump through retry hoops like
> GtS, omitting query-params is the safer bet for now (presumably this
> will only change if Mastodon ever decides to send out requests
> signed with query params)

1 files changed, 27 insertions, 3 deletions

diff --git a/packages/backend/src/server/ActivityPubServerService.ts b/packages/backend/src/server/ActivityPubServerService.ts
index ea534af458..f40fbe8245 100644
--- a/packages/backend/src/server/ActivityPubServerService.ts
+++ b/packages/backend/src/server/ActivityPubServerService.ts
@@ -177,7 +177,7 @@ export class ActivityPubServerService {
 			 this is also inspired by FireFish's `checkFetch`
 		*/
 
-		let signature;
+		let signature: httpSignature.IParsedSignature;
 
 		try {
 			signature = httpSignature.parseRequest(request.raw, {
@@ -230,14 +230,38 @@ export class ActivityPubServerService {
 			return `${logPrefix} signer is suspended: refuse`;
 		}
 
-		let httpSignatureValidated = httpSignature.verifySignature(signature, authUser.key.keyPem);
+		// some fedi implementations include the query (`?foo=bar`) in the
+		// signature, some don't, so we have to handle both cases
+		function verifyWithOrWithoutQuery() {
+			const httpSignatureValidated = httpSignature.verifySignature(signature, authUser!.key!.keyPem);
+			if (httpSignatureValidated) return true;
+
+			const requestUrl = new URL(`http://whatever${request.raw.url}`);
+			if (! requestUrl.search) return false;
+
+			// verification failed, the request URL contained a query, let's try without
+			const semiRawRequest = request.raw;
+			semiRawRequest.url = requestUrl.pathname;
+
+			// no need for try/catch, if the original request parsed, this
+			// one will, too
+			const signatureWithoutQuery = httpSignature.parseRequest(semiRawRequest, {
+				headers: ['(request-target)', 'host', 'date'],
+				authorizationHeaderName: 'signature',
+			});
+
+			return httpSignature.verifySignature(signatureWithoutQuery, authUser!.key!.keyPem);
+		}
+
+		console.warn('starting verification');
+		let httpSignatureValidated = verifyWithOrWithoutQuery();
 
 		// maybe they changed their key? refetch it
 		// TODO rate-limit this using lastFetchedAt
 		if (!httpSignatureValidated) {
 			authUser.key = await this.apDbResolverService.refetchPublicKeyForApId(authUser.user);
 			if (authUser.key != null) {
-				httpSignatureValidated = httpSignature.verifySignature(signature, authUser.key.keyPem);
+				httpSignatureValidated = verifyWithOrWithoutQuery();
 			}
 		}