snapshot of https://github.com/go-gitea/gitea.git (main, 2026-09-15; blobs > 131072B omitted)

modules/avatar/federated.go

@@ -0,0 +1,55 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package avatar
+
+import (
+	"context"
+	"errors"
+	"net"
+	"strconv"
+	"strings"
+	"time"
+
+	"gitea.dev/modules/cache"
+)
+
+// LookupFederatedHost returns the avatar host from the email domain's SRV record. https://wiki.libravatar.org/api/
+func LookupFederatedHost(ctx context.Context, email string, secure bool) string {
+	_, domain, found := strings.CutLast(email, "@")
+	if !found {
+		return ""
+	}
+	domain = strings.ToLower(domain)
+
+	service, defaultPort := "avatars", uint16(80)
+	if secure {
+		service, defaultPort = "avatars-sec", 443
+	}
+
+	host, _ := cache.GetString(cache.SafeCacheKey("Avatar:SRV:"+service, domain), func() (string, error) {
+		lookupCtx, cancel := context.WithTimeout(ctx, 3*time.Second) // a slow resolver must not stall the request
+		defer cancel()
+
+		// LookupSRV already sorts by priority and randomizes by weight (RFC 2782)
+		_, records, err := net.DefaultResolver.LookupSRV(lookupCtx, service, "tcp", domain)
+		var dnsErr *net.DNSError
+		if err != nil && !(errors.As(err, &dnsErr) && dnsErr.IsNotFound) {
+			return "", err // a timeout or a cancelled request must not cache as "no record"
+		}
+		if err != nil || len(records) == 0 {
+			return "", nil
+		}
+		return srvHost(records[0], defaultPort), nil
+	})
+	return host
+}
+
+// a target of "." means the service is unavailable (RFC 2782)
+func srvHost(record *net.SRV, defaultPort uint16) string {
+	target := strings.TrimSuffix(record.Target, ".")
+	if target == "" || record.Port == defaultPort {
+		return target
+	}
+	return net.JoinHostPort(target, strconv.Itoa(int(record.Port)))
+}