webhooker/internal/handlers/target_edit.go

package handlers

import (
	"net/http"

	"github.com/go-chi/chi"
	"sneak.berlin/go/webhooker/internal/database"
	"sneak.berlin/go/webhooker/internal/delivery"
)

// targetEditTemplate is the page the target edit form renders.
const targetEditTemplate = "target_edit.html"

// tmplKeyTarget is the template data key for the target being
// edited, and tmplKeyMaxTimeout for the timeout ceiling the form
// tells the user about.
const (
	tmplKeyTarget     = "Target"
	tmplKeyMaxTimeout = "MaxTimeout"
)

// configUnreadableMessage is shown when a target's stored
// configuration does not parse. It says plainly that saving replaces
// the stored value rather than preserving it, because the form
// cannot pre-fill what it could not read.
const configUnreadableMessage = "The stored configuration for this " +
	"target could not be read. Enter the values below; saving " +
	"replaces the stored configuration."

// targetEditView is the display model for the target edit page.
//
// It carries the target's row fields alongside its UNMASKED
// configuration, and deliberately omits database.Target's raw
// Config blob: the form renders named fields, and giving the
// template the blob as well would put an unreviewed second path to
// the credential on the page.
type targetEditView struct {
	ID         string
	Name       string
	Type       database.TargetType
	Active     bool
	MaxRetries int
	Config     delivery.TargetConfigForm
}

// HandleTargetEdit shows the form to edit a target.
//
// This page is the one place the full destination URL and header
// values are shown. It is reachable only through the
// /source/{sourceID} route group, which supplies RequireAuth and
// NoCache, and only for a target of a webhook the session's user
// owns; masking (delivery.TargetView) is unchanged everywhere else.
func (h *Handlers) HandleTargetEdit() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		webhook, target, ok := h.ownedTarget(w, r)
		if !ok {
			return
		}

		cfg, err := delivery.NewTargetConfigForm(target)
		msg := ""

		if err != nil {
			// The error carries the parse failure, never the
			// blob, so it is safe to log against the target id.
			h.log.Warn(
				"stored target config could not be read for editing",
				"target_id", target.ID,
				"error", err,
			)

			msg = configUnreadableMessage
		}

		h.renderTargetEdit(w, r, webhook, target, cfg, msg)
	}
}

// HandleTargetEditSubmit handles the target edit form submission.
func (h *Handlers) HandleTargetEditSubmit() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		webhook, target, ok := h.ownedTarget(w, r)
		if !ok {
			return
		}

		// The body size cap is enforced by the MaxBodySize
		// middleware, which runs before CSRF parses the form.
		err := r.ParseForm()
		if err != nil {
			http.Error(
				w, "Bad request", http.StatusBadRequest,
			)

			return
		}

		h.applyTargetEdit(w, r, webhook, target)
	}
}

// applyTargetEdit validates and saves target edits.
//
// The submitted configuration goes through buildTargetConfig, the
// same builder the create path uses, so an edited destination is
// SSRF-validated exactly as a new one is.
//
// The target's type is not editable. Each type stores a different
// configuration shape and its delivery history is recorded against
// the target row, so changing the type of an existing target is
// really the creation of a different one. The stored type decides
// which fields the form offers and which builder runs.
func (h *Handlers) applyTargetEdit(
	w http.ResponseWriter,
	r *http.Request,
	webhook database.Webhook,
	target *database.Target,
) {
	name := r.PostFormValue("name")
	if name == "" {
		http.Error(
			w, "Name is required", http.StatusBadRequest,
		)

		return
	}

	configJSON, err := h.buildTargetConfig(
		w, r, target.Type, targetFormInputFrom(r),
	)
	if err != nil {
		// buildTargetConfig has already written the response.
		return
	}

	// Retries are offered only by the forms for target types that
	// retry, so an absent field means "this form does not edit
	// retries" rather than "set them to zero". Reading it
	// unconditionally would silently disable retries on any target
	// saved from a form that does not render the input.
	//
	// A field that IS submitted but does not parse is a 400, through
	// the same validator the create path uses. It is rejected before
	// anything is written, so a typo cannot destroy the retry count
	// the target is already delivering with.
	if r.PostForm.Has("max_retries") {
		retries, ok := targetMaxRetries(w, r, target.MaxRetries)
		if !ok {
			return
		}

		target.MaxRetries = retries
	}

	target.Name = name
	target.Config = configJSON

	err = h.db.DB().Save(target).Error
	if err != nil {
		h.serverError(w, "failed to update target", err)

		return
	}

	http.Redirect(
		w, r, "/source/"+webhook.ID, http.StatusSeeOther,
	)
}

// renderTargetEdit renders the target edit page with an optional
// error message.
func (h *Handlers) renderTargetEdit(
	w http.ResponseWriter,
	r *http.Request,
	webhook database.Webhook,
	target *database.Target,
	cfg delivery.TargetConfigForm,
	errMsg string,
) {
	// The template calls Webhook methods, which take pointer
	// receivers; html/template cannot address a value stored in a
	// map.
	data := map[string]any{
		tmplKeyWebhook: &webhook,
		tmplKeyTarget: targetEditView{
			ID:         target.ID,
			Name:       target.Name,
			Type:       target.Type,
			Active:     target.Active,
			MaxRetries: target.MaxRetries,
			Config:     cfg,
		},
		tmplKeyMaxTimeout: delivery.MaxTargetTimeoutSeconds,
		tmplKeyError:      errMsg,
	}

	h.renderTemplate(w, r, targetEditTemplate, data)
}

// ownedTarget resolves the request's sourceID and targetID
// parameters to a target of a webhook the session's user owns.
//
// Ownership is decided by the webhook, and the target is then
// scoped to that webhook, so a target id belonging to someone
// else's webhook is a 404 rather than an edit of their target. It
// reports false once it has written the response.
func (h *Handlers) ownedTarget(
	w http.ResponseWriter,
	r *http.Request,
) (database.Webhook, *database.Target, bool) {
	webhook, ok := h.ownedWebhook(w, r)
	if !ok {
		return database.Webhook{}, nil, false
	}

	var target database.Target

	err := h.db.DB().Where(
		"id = ? AND webhook_id = ?",
		chi.URLParam(r, "targetID"), webhook.ID,
	).First(&target).Error
	if err != nil {
		http.NotFound(w, r)

		return database.Webhook{}, nil, false
	}

	return webhook, &target, true
}