fix(http): harden BaseURL proxy scheme/host detection

Split comma-separated X-Forwarded-Proto and honor the RFC 7239 Forwarded
header so generated links use https behind common reverse-proxy setups.

Refs #10482

Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

core/http/middleware/baseurl.go

@@ -55,17 +55,62 @@ func BasePathPrefix(c echo.Context) string {
 // The returned URL is guaranteed to end with `/`.
 // The method should be used in conjunction with the StripPathPrefix middleware.
 func BaseURL(c echo.Context) string {
+	fwdProto, fwdHost := parseForwarded(c.Request().Header.Get("Forwarded"))
+
 	scheme := "http"
-	if c.Request().Header.Get("X-Forwarded-Proto") == "https" {
+	switch {
+	case c.Request().TLS != nil:
 		scheme = "https"
-	} else if c.Request().TLS != nil {
+	case strings.EqualFold(firstToken(c.Request().Header.Get("X-Forwarded-Proto")), "https"):
+		scheme = "https"
+	case strings.EqualFold(fwdProto, "https"):
 		scheme = "https"
 	}
 
 	host := c.Request().Host
 	if forwardedHost := c.Request().Header.Get("X-Forwarded-Host"); forwardedHost != "" {
 		host = forwardedHost
+	} else if fwdHost != "" {
+		host = fwdHost
 	}
 
 	return scheme + "://" + host + BasePathPrefix(c)
 }
+
+// firstToken returns the first comma-separated token of v, trimmed of spaces.
+// Reverse-proxy chains can emit X-Forwarded-Proto as "https,http"; only the
+// first hop (closest to the client) is meaningful for scheme detection.
+func firstToken(v string) string {
+	if i := strings.IndexByte(v, ','); i >= 0 {
+		v = v[:i]
+	}
+	return strings.TrimSpace(v)
+}
+
+// parseForwarded extracts the proto and host directives from the first element
+// of an RFC 7239 Forwarded header (e.g. `for=x;proto=https;host=h, for=y`).
+// Values may be quoted. Returns empty strings when absent or malformed so the
+// caller can fall through to other signals.
+func parseForwarded(header string) (proto, host string) {
+	if header == "" {
+		return "", ""
+	}
+	// Only the first element (closest proxy to the client) matters here.
+	if i := strings.IndexByte(header, ','); i >= 0 {
+		header = header[:i]
+	}
+	for _, directive := range strings.Split(header, ";") {
+		key, value, ok := strings.Cut(strings.TrimSpace(directive), "=")
+		if !ok {
+			continue
+		}
+		value = strings.Trim(strings.TrimSpace(value), `"`)
+		switch strings.ToLower(strings.TrimSpace(key)) {
+		case "proto":
+			proto = value
+		case "host":
+			host = value
+		}
+	}
+	return proto, host
+}

core/http/middleware/baseurl_test.go

@@ -135,4 +135,49 @@ var _ = Describe("BaseURL", func() {
 			Entry("missing leading slash", "evil"),
 		)
 	})
+
+	Context("scheme detection hardening", func() {
+		It("treats comma-separated X-Forwarded-Proto as https when first token is https", func() {
+			app := echo.New()
+			actualURL := ""
+			app.GET("/x", func(c echo.Context) error {
+				actualURL = BaseURL(c)
+				return nil
+			})
+			req := httptest.NewRequest("GET", "/x", nil)
+			req.Header.Set("X-Forwarded-Proto", "https,http")
+			rec := httptest.NewRecorder()
+			app.ServeHTTP(rec, req)
+			Expect(actualURL).To(Equal("https://example.com/"))
+		})
+
+		It("derives https from the RFC 7239 Forwarded proto directive", func() {
+			app := echo.New()
+			actualURL := ""
+			app.GET("/x", func(c echo.Context) error {
+				actualURL = BaseURL(c)
+				return nil
+			})
+			req := httptest.NewRequest("GET", "/x", nil)
+			req.Header.Set("Forwarded", "for=192.0.2.1;proto=https;host=proxy.example")
+			rec := httptest.NewRecorder()
+			app.ServeHTTP(rec, req)
+			Expect(actualURL).To(Equal("https://proxy.example/"))
+		})
+
+		It("prefers X-Forwarded-Host over the Forwarded host directive", func() {
+			app := echo.New()
+			actualURL := ""
+			app.GET("/x", func(c echo.Context) error {
+				actualURL = BaseURL(c)
+				return nil
+			})
+			req := httptest.NewRequest("GET", "/x", nil)
+			req.Header.Set("X-Forwarded-Host", "xfh.example")
+			req.Header.Set("Forwarded", "host=fwd.example;proto=https")
+			rec := httptest.NewRecorder()
+			app.ServeHTTP(rec, req)
+			Expect(actualURL).To(Equal("https://xfh.example/"))
+		})
+	})
 })