http: add "Use reverse proxy host" option

added "Use reverse-proxy reported "Host" when possible" option, which
will prefer using the "Host" or "X-Forwarded-Host" values instead of
"External jfa-go URL" in the web app. To do so, app.ExternalDomain/URI
are now functions which take *gin.Context (the latter optionally). The
protocol for the request is determined from X-Forwarded-Proto(col), so
make sure your proxy includes it.

The wiki will have been updated to mention the new option.

auth.go

@@ -266,8 +266,7 @@ func (app *appContext) getTokenLogin(gc *gin.Context) {
 		respond(500, "Couldn't generate token", gc)
 		return
 	}
-	// host := gc.Request.URL.Hostname()
-	host := app.ExternalDomain
+	host := app.ExternalDomain(gc)
 
 	// Before you think this is broken: the first "true" arg is for "secure", i.e. only HTTPS!
 	gc.SetCookie("refresh", refresh, REFRESH_TOKEN_VALIDITY_SEC, "/", host, true, true)
@@ -329,7 +328,7 @@ func (app *appContext) getTokenRefresh(gc *gin.Context) {
 		return
 	}
 	// host := gc.Request.URL.Hostname()
-	host := app.ExternalDomain
+	host := app.ExternalDomain(gc)
 	gc.SetCookie("refresh", refresh, REFRESH_TOKEN_VALIDITY_SEC, "/", host, true, true)
 	gc.JSON(200, getTokenDTO{jwt})
 }

config.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/gin-gonic/gin"
 	"github.com/hrfee/jfa-go/common"
 	"github.com/hrfee/jfa-go/easyproxy"
 	lm "github.com/hrfee/jfa-go/logmessages"
@@ -68,6 +69,35 @@ func (app *appContext) MustCorrectURL(section, key, value string) {
 	app.config.Section(section).Key(key).SetValue(v)
 }
 
+// ExternalDomain returns the Host for the request, using the fixed app.externalDomain value unless app.UseProxyHost is true.
+func (app *appContext) ExternalDomain(gc *gin.Context) string {
+	if !app.UseProxyHost || gc.Request.Host == "" {
+		return app.externalDomain
+	}
+	return gc.Request.Host
+}
+
+// ExternalURI returns the External URI of jfa-go's root directory (by default, where the admin page is), using the fixed app.externalURI value unless app.UseProxyHost is true and gc is not nil.
+// When nil is passed, app.externalURI is returned.
+func (app *appContext) ExternalURI(gc *gin.Context) string {
+	if gc == nil {
+		return app.externalURI
+	}
+
+	var proto string
+	if gc.Request.TLS != nil || gc.Request.Header.Get("X-Forwarded-Proto") == "https" || gc.Request.Header.Get("X-Forwarded-Protocol") == "https" {
+		proto = "https://"
+	} else {
+		proto = "http://"
+	}
+
+	// app.debug.Printf("Request: %+v\n", gc.Request)
+	if app.UseProxyHost && gc.Request.Host != "" {
+		return proto + gc.Request.Host + PAGES.Base
+	}
+	return app.externalURI
+}
+
 func (app *appContext) loadConfig() error {
 	var err error
 	app.config, err = ini.ShadowLoad(app.configPath)
@@ -108,16 +138,22 @@ func (app *appContext) loadConfig() error {
 		app.config.Section("files").Key(key).SetValue(app.config.Section("files").Key(key).MustString(filepath.Join(app.dataPath, (key + ".db"))))
 	}
 
-	app.ExternalURI = strings.TrimSuffix(strings.TrimSuffix(app.config.Section("ui").Key("jfa_url").MustString(""), "/invite"), "/")
-	if !strings.HasSuffix(app.ExternalURI, PAGES.Base) {
+	// If true, app.ExternalDomain() will return one based on the reported Host (ideally reported in "Host" or "X-Forwarded-Host" by the reverse proxy), falling back to app.externalDomain if not set.
+	app.UseProxyHost = app.config.Section("ui").Key("use_proxy_host").MustBool(false)
+	app.externalURI = strings.TrimSuffix(strings.TrimSuffix(app.config.Section("ui").Key("jfa_url").MustString(""), "/invite"), "/")
+	if !strings.HasSuffix(app.externalURI, PAGES.Base) {
 		app.err.Println(lm.NoURLSuffix)
 	}
-	if app.ExternalURI == "" {
-		app.err.Println(lm.NoExternalHost + lm.LoginWontSave)
+	if app.externalURI == "" {
+		if app.UseProxyHost {
+			app.err.Println(lm.NoExternalHost + lm.LoginWontSave + lm.SetExternalHostDespiteUseProxyHost)
+		} else {
+			app.err.Println(lm.NoExternalHost + lm.LoginWontSave)
+		}
 	}
-	u, err := url.Parse(app.ExternalURI)
+	u, err := url.Parse(app.externalURI)
 	if err == nil {
-		app.ExternalDomain = u.Hostname()
+		app.externalDomain = u.Hostname()
 	}
 
 	app.config.Section("email").Key("no_username").SetValue(strconv.FormatBool(app.config.Section("email").Key("no_username").MustBool(false)))

config/config-base.yaml

@@ -215,12 +215,15 @@ sections:
   - setting: jfa_url
     name: External jfa-go URL
     required: true
-    depends_true: enabled
     type: text
     value: http://accounts.jellyf.in:8056
     description: The URL at which the jfa-go root (usually the admin page) is accessible, including
-      the subfolder if you use one. This is necessary because using a reverse proxy
-      means the program has no way of knowing the URL itself.
+      the subfolder if you use one. While your reverse proxy should report this anyway, server-side actions like sending invite messages don't receive such wisdom.
+  - setting: use_proxy_host
+    name: Use reverse-proxy reported "Host" when possible
+    type: bool
+    value: false
+    description: If enabled, the "Host" reported by your reverse proxy will be used in the web app, rather than the "External jfa-go URL" value. Useful if you regularly access jfa-go from more than one host/domain. Also, make sure your proxy passes X-Forwarded-Proto/X-Forwarded-Protocol.
   - setting: url_base
     name: Reverse Proxy subfolder
     requires_restart: true

email.go

@@ -326,7 +326,7 @@ func (emailer *Emailer) confirmationValues(code, username, key string, app *appC
 		}
 	} else {
 		message := app.config.Section("messages").Key("message").String()
-		inviteLink := app.ExternalURI
+		inviteLink := app.ExternalURI(nil)
 		if code == "" { // Personal email change
 			inviteLink = fmt.Sprintf("%s/my/confirm/%s", inviteLink, url.PathEscape(key))
 		} else { // Invite email confirmation
@@ -394,7 +394,7 @@ func (emailer *Emailer) inviteValues(code string, invite Invite, app *appContext
 	expiry := invite.ValidTill
 	d, t, expiresIn := emailer.formatExpiry(expiry, false, app.datePattern, app.timePattern)
 	message := app.config.Section("messages").Key("message").String()
-	inviteLink := fmt.Sprintf("%s%s/%s", app.ExternalURI, PAGES.Form, code)
+	inviteLink := fmt.Sprintf("%s%s/%s", app.ExternalURI(nil), PAGES.Form, code)
 	template := map[string]interface{}{
 		"hello":              emailer.lang.InviteEmail.get("hello"),
 		"youHaveBeenInvited": emailer.lang.InviteEmail.get("youHaveBeenInvited"),

logmessages/logmessages.go

@@ -207,15 +207,16 @@ const (
 	FailedRestoreDB       = "Failed to resotre database from \"%s\": %v"
 
 	// config.go
-	EnableAllPWRMethods = "No PWR method preferences set in [user_page], all will be enabled"
-	InitProxy           = "Initialized proxy @ \"%s\""
-	FailedInitProxy     = "Failed to initialize proxy @ \"%s\": %v\nStartup will pause for a bit to grab your attention."
-	NoURLSuffix         = `Warning: Given "jfa_url"/"External jfa-go URL" value does not include "url_base" value!`
-	BadURLBase          = `Warning: Given reverse proxy subfolder "%s" may conflict with the applications subpaths.`
-	RouteCollision      = `Route Collision! Given reverse proxy subfolder "%s" or "URL Paths" settings likely conflict with the applications subpaths. Culprit: %v`
-	NoExternalHost      = `No "External jfa-go URL" provided, set one in Settings > General.`
-	LoginWontSave       = ` Your login won't save until you do.`
-	SubpathBlockMessage = `URLs: Root subfolder = "%s", Admin = "%s", My Account = "%s", Invite forms = "%s"`
+	EnableAllPWRMethods                = "No PWR method preferences set in [user_page], all will be enabled"
+	InitProxy                          = "Initialized proxy @ \"%s\""
+	FailedInitProxy                    = "Failed to initialize proxy @ \"%s\": %v\nStartup will pause for a bit to grab your attention."
+	NoURLSuffix                        = `Warning: Given "jfa_url"/"External jfa-go URL" value does not include "url_base" value!`
+	BadURLBase                         = `Warning: Given reverse proxy subfolder "%s" may conflict with the applications subpaths.`
+	RouteCollision                     = `Route Collision! Given reverse proxy subfolder "%s" or "URL Paths" settings likely conflict with the applications subpaths. Culprit: %v`
+	NoExternalHost                     = `No "External jfa-go URL" provided, set one in Settings > General.`
+	LoginWontSave                      = ` Logins may not save until you do.`
+	SetExternalHostDespiteUseProxyHost = ` This needs to be set even though use_proxy_host is enabled.`
+	SubpathBlockMessage                = `URLs: Root subfolder = "%s", Admin = "%s", My Account = "%s", Invite forms = "%s"`
 
 	// discord.go
 	StartDaemon                      = "Started %s daemon"

main.go

@@ -121,7 +121,8 @@ type appContext struct {
 	host                        string
 	port                        int
 	version                     string
-	ExternalURI, ExternalDomain string
+	externalURI, externalDomain string // The latter lower-case as should be accessed through app.ExternalDomain()
+	UseProxyHost                bool
 	updater                     *Updater
 	webhooks                    *WebhookSender
 	newUpdate                   bool // Whether whatever's in update is new.

pwreset.go

@@ -30,7 +30,7 @@ func (app *appContext) GenInternalReset(userID string) (InternalPWR, error) {
 
 // GenResetLink generates and returns a password reset link.
 func (app *appContext) GenResetLink(pin string) (string, error) {
-	url := app.ExternalURI
+	url := app.ExternalURI(nil)
 	var pinLink string
 	if url == "" {
 		return pinLink, errors.New(lm.NoExternalHost)

user-auth.go

@@ -65,7 +65,7 @@ func (app *appContext) getUserTokenLogin(gc *gin.Context) {
 	}
 
 	// host := gc.Request.URL.Hostname()
-	host := app.ExternalDomain
+	host := app.ExternalDomain(gc)
 	uri := "/my"
 	// FIXME: This seems like a bad idea? I think it's to deal with people having Reverse proxy subfolder/URL base set to /accounts.
 	if strings.HasPrefix(gc.Request.RequestURI, PAGES.Base) {
@@ -105,7 +105,7 @@ func (app *appContext) getUserTokenRefresh(gc *gin.Context) {
 	}
 
 	// host := gc.Request.URL.Hostname()
-	host := app.ExternalDomain
+	host := app.ExternalDomain(gc)
 	gc.SetCookie("user-refresh", refresh, REFRESH_TOKEN_VALIDITY_SEC, "/my", host, true, true)
 	gc.JSON(200, getTokenDTO{jwt})
 }

views.go

@@ -88,7 +88,7 @@ func (app *appContext) BasePageTemplateValues(gc *gin.Context, page Page, base g
 
 	pages := PagePathsDTO{
 		PagePaths:   PAGES,
-		ExternalURI: app.ExternalURI,
+		ExternalURI: app.ExternalURI(gc),
 		TrueBase:    PAGES.Base,
 	}
 	pages.Base = app.getURLBase(gc)
@@ -742,7 +742,7 @@ func (app *appContext) InviteProxy(gc *gin.Context) {
 	discord := discordEnabled && app.config.Section("discord").Key("show_on_reg").MustBool(true)
 	matrix := matrixEnabled && app.config.Section("matrix").Key("show_on_reg").MustBool(true)
 
-	userPageAddress := app.ExternalURI + PAGES.MyAccount
+	userPageAddress := app.ExternalURI(gc) + PAGES.MyAccount
 
 	fromUser := ""
 	if invite.ReferrerJellyfinID != "" {