1 files changed, 80 insertions, 0 deletions
diff --git a/internal/federation/dereferencing/finger.go b/internal/federation/dereferencing/finger.go
new file mode 100644
index 000000000..9613d2975
--- /dev/null
+++ b/internal/federation/dereferencing/finger.go
@@ -0,0 +1,80 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package dereferencing
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/url"
+	"strings"
+
+	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
+	"github.com/superseriousbusiness/gotosocial/internal/util"
+)
+
+func (d *deref) fingerRemoteAccount(ctx context.Context, username string, targetUsername string, targetHost string) (accountDomain string, accountURI *url.URL, err error) {
+	t, err := d.transportController.NewTransportForUsername(ctx, username)
+	if err != nil {
+		err = fmt.Errorf("fingerRemoteAccount: error getting transport for %s: %s", username, err)
+		return
+	}
+
+	b, err := t.Finger(ctx, targetUsername, targetHost)
+	if err != nil {
+		err = fmt.Errorf("fingerRemoteAccount: error fingering @%s@%s: %s", targetUsername, targetHost, err)
+		return
+	}
+
+	resp := &apimodel.WellKnownResponse{}
+	if err = json.Unmarshal(b, resp); err != nil {
+		err = fmt.Errorf("fingerRemoteAccount: could not unmarshal server response as WebfingerAccountResponse while dereferencing @%s@%s: %s", targetUsername, targetHost, err)
+		return
+	}
+
+	if len(resp.Links) == 0 {
+		err = fmt.Errorf("fingerRemoteAccount: no links found in webfinger response %s", string(b))
+		return
+	}
+
+	if resp.Subject == "" {
+		err = fmt.Errorf("fingerRemoteAccount: no subject found in webfinger response %s", string(b))
+		return
+	}
+
+	_, accountDomain, err = util.ExtractWebfingerParts(resp.Subject)
+	if err != nil {
+		err = fmt.Errorf("fingerRemoteAccount: error extracting webfinger subject parts: %s", err)
+	}
+
+	// look through the links for the first one that matches what we need
+	for _, l := range resp.Links {
+		if l.Rel == "self" && (strings.EqualFold(l.Type, "application/activity+json") || strings.EqualFold(l.Type, "application/ld+json; profile=\"https://www.w3.org/ns/activitystreams\"")) {
+			if uri, thiserr := url.Parse(l.Href); thiserr == nil && (uri.Scheme == "http" || uri.Scheme == "https") {
+				// found it!
+				accountURI = uri
+				return
+			}
+		}
+	}
+
+	err = errors.New("fingerRemoteAccount: no match found in webfinger response")
+	return
+}