[bugfix] Use punycode for `host` part of `resource` query param when doing webfinger requests (#3133)

* [bugfix] use punycode when webfingering

* account for punycode when checking if final URI matches expected

* hmm

* fix test

1 files changed, 68 insertions, 0 deletions

diff --git a/internal/util/punycode.go b/internal/util/punycode.go
index 4a595a281..cc1b57a27 100644
--- a/internal/util/punycode.go
+++ b/internal/util/punycode.go
@@ -18,6 +18,7 @@
 package util
 
 import (
+	"net/url"
 	"strings"
 
 	"golang.org/x/net/idna"
@@ -42,3 +43,70 @@ func DePunify(domain string) (string, error) {
 	out, err := idna.ToUnicode(domain)
 	return strings.ToLower(out), err
 }
+
+// URIMatches returns true if the expected URI matches
+// any of the given URIs, taking account of punycode.
+func URIMatches(expect *url.URL, uris ...*url.URL) (bool, error) {
+	// Normalize expect to punycode.
+	expectPuny, err := PunifyURI(expect)
+	if err != nil {
+		return false, err
+	}
+	expectStr := expectPuny.String()
+
+	for _, uri := range uris {
+		uriPuny, err := PunifyURI(uri)
+		if err != nil {
+			return false, err
+		}
+
+		if uriPuny.String() == expectStr {
+			// Looks good.
+			return true, nil
+		}
+	}
+
+	// Didn't match.
+	return false, nil
+}
+
+// PunifyURI returns a copy of the given URI
+// with the 'host' part converted to punycode.
+func PunifyURI(in *url.URL) (*url.URL, error) {
+	// Take a copy of in.
+	out := new(url.URL)
+	*out = *in
+
+	// Normalize host to punycode.
+	var err error
+	out.Host, err = Punify(in.Host)
+	return out, err
+}
+
+// PunifyURIStr returns a copy of the given URI
+// string with the 'host' part converted to punycode.
+func PunifyURIStr(in string) (string, error) {
+	inURI, err := url.Parse(in)
+	if err != nil {
+		return "", err
+	}
+
+	outURIPuny, err := Punify(inURI.Host)
+	if err != nil {
+		return "", err
+	}
+
+	if outURIPuny == in {
+		// Punify did nothing, so in was
+		// already punified, return as-is.
+		return in, nil
+	}
+
+	// Take a copy of in.
+	outURI := new(url.URL)
+	*outURI = *inURI
+
+	// Normalize host to punycode.
+	outURI.Host = outURIPuny
+	return outURI.String(), err
+}