From 6b3abd9def453b4fd9ffcabba4fc8699ce1a6025 Mon Sep 17 00:00:00 2001
From: TowyTowy <towy@airreps.link>
Date: Thu, 9 Jul 2026 12:43:12 +0200
Subject: [PATCH] fix(api): keep reverse-proxy path prefix in paging next url

When gotify runs behind a reverse proxy that strips a subpath before
forwarding (e.g. Caddy `uri strip_prefix /gotify`), the incoming request
path no longer contains the prefix, so the `next` paging url emitted by
GetMessages dropped it (e.g. `/message` instead of `/gotify/message`).

Honor the X-Forwarded-Prefix header, which such proxies can set to
announce the stripped prefix, when constructing the `next` url so it
keeps pointing at the externally reachable path. Behavior is unchanged
when the header is absent.

Fixes #664

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 api/message.go      | 16 +++++++++++++++-
 api/message_test.go | 27 +++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/api/message.go b/api/message.go
index ca818109..ee3c1ef0 100644
--- a/api/message.go
+++ b/api/message.go
@@ -105,7 +105,7 @@ func buildWithPaging(ctx *gin.Context, paging *pagingParams, messages []*model.M
 		useMessages = messages[:len(messages)-1]
 		since = useMessages[len(useMessages)-1].ID
 		url := location.Get(ctx)
-		url.Path = ctx.Request.URL.Path
+		url.Path = withForwardedPrefix(ctx, ctx.Request.URL.Path)
 		query := url.Query()
 		query.Add("limit", strconv.Itoa(paging.Limit))
 		query.Add("since", strconv.FormatUint(uint64(since), 10))
@@ -118,6 +118,20 @@ func buildWithPaging(ctx *gin.Context, paging *pagingParams, messages []*model.M
 	}
 }
 
+// withForwardedPrefix prepends the reverse-proxy path prefix to the given
+// request path. Reverse proxies that strip a subpath before forwarding the
+// request (e.g. Caddy's `uri strip_prefix /gotify`) can announce the stripped
+// prefix via the X-Forwarded-Prefix header, so that URLs emitted by gotify —
+// like the paging `next` link — keep pointing at the externally reachable path
+// instead of dropping the prefix. See #664.
+func withForwardedPrefix(ctx *gin.Context, path string) string {
+	prefix := strings.Trim(ctx.GetHeader("X-Forwarded-Prefix"), "/")
+	if prefix == "" {
+		return path
+	}
+	return "/" + prefix + "/" + strings.TrimPrefix(path, "/")
+}
+
 func withPaging(ctx *gin.Context, f func(pagingParams *pagingParams)) {
 	params := &pagingParams{Limit: 100}
 	if err := ctx.MustBindWith(params, binding.Query); err == nil {
diff --git a/api/message_test.go b/api/message_test.go
index 2a1d4a2b..968318aa 100644
--- a/api/message_test.go
+++ b/api/message_test.go
@@ -106,6 +106,33 @@ func (s *MessageSuite) Test_GetMessages_WithLimit_ReturnsNext() {
 	test.BodyEquals(s.T(), expected, s.recorder)
 }
 
+func (s *MessageSuite) Test_GetMessages_WithLimit_BehindProxyPrefix_ReturnsNextWithPrefix() {
+	user := s.db.User(5)
+	app1 := user.App(1)
+	app2 := user.App(2)
+	var messages []*model.Message
+	for i := 100; i >= 1; i -= 2 {
+		one := app2.NewMessage(uint(i))
+		two := app1.NewMessage(uint(i - 1))
+		messages = append(messages, &one, &two)
+	}
+
+	// The reverse proxy strips the /gotify prefix, so gotify receives /message,
+	// but announces the stripped prefix via X-Forwarded-Prefix. The emitted
+	// next url must keep the prefix. See #664.
+	s.withURL("http", "example.com", "/message", "limit=5")
+	s.ctx.Request.Header.Set("X-Forwarded-Prefix", "/gotify")
+	test.WithUser(s.ctx, 5)
+	s.a.GetMessages(s.ctx)
+
+	expected := &model.PagedMessages{
+		Paging:   model.Paging{Limit: 5, Size: 5, Since: 96, Next: "http://example.com/gotify/message?limit=5&since=96"},
+		Messages: toExternalMessages(messages[:5]),
+	}
+
+	test.BodyEquals(s.T(), expected, s.recorder)
+}
+
 func (s *MessageSuite) Test_GetMessages_WithLimit_WithSince_ReturnsNext() {
 	user := s.db.User(5)
 	app1 := user.App(1)