feat: templatized proxy error page

.goreleaser.yaml

@@ -63,6 +63,9 @@ nfpms:
       - src: layers
         dst: /etc/bouncer/layers
         type: config
+      - src: templates
+        dst: /etc/bouncer/templates
+        type: config
       - dst: /etc/bouncer/bootstrap.d
         type: dir
         file_info:

Dockerfile

@@ -22,6 +22,7 @@ RUN make GORELEASER_ARGS='build --rm-dist --single-target --snapshot' goreleaser
 
 # Patch config
 RUN /src/dist/bouncer_linux_amd64_v1/bouncer -c '' config dump > /src/dist/bouncer_linux_amd64_v1/config.yml \
+&& yq -i '.proxy.templates.dir = "/usr/share/bouncer/templates"' /src/dist/bouncer_linux_amd64_v1/config.yml \
     && yq -i '.layers.queue.templateDir = "/usr/share/bouncer/layers/queue/templates"' /src/dist/bouncer_linux_amd64_v1/config.yml \
     && yq -i '.layers.authn.templateDir = "/usr/share/bouncer/layers/authn/templates"' /src/dist/bouncer_linux_amd64_v1/config.yml \
     && yq -i '.admin.auth.privateKey = "/etc/bouncer/admin-key.json"' /src/dist/bouncer_linux_amd64_v1/config.yml \

internal/config/proxy_server.go

@@ -7,22 +7,26 @@ import (
 )
 
 type ProxyServerConfig struct {
-	HTTP      HTTPConfig      `yaml:"http"`
-	Metrics   MetricsConfig   `yaml:"metrics"`
-	Transport TransportConfig `yaml:"transport"`
-	Dial      DialConfig      `yaml:"dial"`
-	Sentry    SentryConfig    `yaml:"sentry"`
-	Cache     CacheConfig     `yaml:"cache"`
+	Debug     InterpolatedBool `yaml:"debug"`
+	HTTP      HTTPConfig       `yaml:"http"`
+	Metrics   MetricsConfig    `yaml:"metrics"`
+	Transport TransportConfig  `yaml:"transport"`
+	Dial      DialConfig       `yaml:"dial"`
+	Sentry    SentryConfig     `yaml:"sentry"`
+	Cache     CacheConfig      `yaml:"cache"`
+	Templates TemplatesConfig  `yaml:"templates"`
 }
 
 func NewDefaultProxyServerConfig() ProxyServerConfig {
 	return ProxyServerConfig{
+		Debug:     false,
 		HTTP:      NewHTTPConfig("0.0.0.0", 8080),
 		Metrics:   NewDefaultMetricsConfig(),
 		Transport: NewDefaultTransportConfig(),
 		Dial:      NewDefaultDialConfig(),
 		Sentry:    NewDefaultSentryConfig(),
 		Cache:     NewDefaultCacheConfig(),
+		Templates: NewDefaultTemplatesConfig(),
 	}
 }
 
@@ -115,3 +119,13 @@ func NewDefaultCacheConfig() CacheConfig {
 		TTL: *NewInterpolatedDuration(time.Second * 30),
 	}
 }
+
+type TemplatesConfig struct {
+	Dir InterpolatedString `yaml:"dir"`
+}
+
+func NewDefaultTemplatesConfig() TemplatesConfig {
+	return TemplatesConfig{
+		Dir: "./templates",
+	}
+}

internal/proxy/server.go

@@ -3,11 +3,14 @@ package proxy
 import (
 	"context"
 	"fmt"
+	"html/template"
 	"log"
 	"net"
 	"net/http"
 	"net/http/httputil"
 	"net/url"
+	"path/filepath"
+	"strconv"
 	"time"
 
 	"forge.cadoles.com/Cadoles/go-proxy"
@@ -17,6 +20,8 @@ import (
 	"forge.cadoles.com/cadoles/bouncer/internal/config"
 	"forge.cadoles.com/cadoles/bouncer/internal/proxy/director"
 	"forge.cadoles.com/cadoles/bouncer/internal/store"
+
+	"github.com/Masterminds/sprig/v3"
 	"github.com/getsentry/sentry-go"
 	sentryhttp "github.com/getsentry/sentry-go/http"
 	"github.com/go-chi/chi/v5"
@@ -191,7 +196,63 @@ func (s *Server) errorHandler(w http.ResponseWriter, r *http.Request, err error)
 	logger.Error(r.Context(), "proxy error", logger.E(err))
 	sentry.CaptureException(err)
 
-	http.Error(w, http.StatusText(http.StatusBadGateway), http.StatusBadGateway)
+	s.renderErrorPage(w, r, err, http.StatusBadGateway, http.StatusText(http.StatusBadGateway))
+}
+
+func (s *Server) renderErrorPage(w http.ResponseWriter, r *http.Request, err error, statusCode int, status string) {
+	templateData := struct {
+		StatusCode int
+		Status     string
+		Err        error
+		Debug      bool
+	}{
+		Debug:      bool(s.serverConfig.Debug),
+		StatusCode: statusCode,
+		Status:     status,
+		Err:        err,
+	}
+
+	w.WriteHeader(statusCode)
+	s.renderPage(w, r, "error", strconv.FormatInt(int64(statusCode), 10), templateData)
+}
+
+func (s *Server) renderPage(w http.ResponseWriter, r *http.Request, page string, block string, templateData any) {
+	ctx := r.Context()
+
+	templatesConf := s.serverConfig.Templates
+
+	pattern := filepath.Join(string(templatesConf.Dir), page+".gohtml")
+
+	logger.Info(ctx, "loading proxy templates", logger.F("pattern", pattern))
+
+	tmpl, err := template.New("").Funcs(sprig.FuncMap()).ParseGlob(pattern)
+	if err != nil {
+		logger.Error(ctx, "could not load proxy templates", logger.E(errors.WithStack(err)))
+		http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+
+		return
+	}
+
+	w.Header().Add("Cache-Control", "no-cache")
+
+	blockTmpl := tmpl.Lookup(block)
+	if blockTmpl == nil {
+		blockTmpl = tmpl.Lookup("default")
+	}
+
+	if blockTmpl == nil {
+		logger.Error(ctx, "could not find template block nor default one", logger.F("block", block))
+		http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+
+		return
+	}
+
+	if err := blockTmpl.Execute(w, templateData); err != nil {
+		logger.Error(ctx, "could not render proxy page", logger.E(errors.WithStack(err)))
+		http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+
+		return
+	}
 }
 
 func NewServer(funcs ...OptionFunc) *Server {

misc/packaging/common/config.yml

@@ -70,6 +70,12 @@ admin:
 
 # Configuration du service "proxy"
 proxy:
+  # Activer/désactiver le mode debug (affichage ou non des messages d'erreur)
+  debug: false
+  # Configuration des templates utilisés par le proxy
+  templates:
+    # Répertoire contenant les templates
+    dir: /etc/bouncer/templates
   http:
     # Hôte d'écoute du service,
     # 0.0.0.0 pour écouter sur toutes les interfaces

templates/error.gohtml

@@ -0,0 +1,96 @@
+{{ define "default" }}
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width,initial-scale=1" />
+    {{ $title := print .StatusCode " - " .Status }}
+    <title>{{ $title }}</title>
+    <style>
+      html {
+        box-sizing: border-box;
+        font-size: 16px;
+      }
+
+      *,
+      *:before,
+      *:after {
+        box-sizing: inherit;
+      }
+
+      body,
+      h1,
+      h2,
+      h3,
+      h4,
+      h5,
+      h6,
+      p,
+      ol,
+      ul {
+        margin: 0;
+        padding: 0;
+        font-weight: normal;
+      }
+
+      html,
+      body {
+        width: 100%;
+        height: 100%;
+        font-family: Arial, Helvetica, sans-serif;
+        background-color: #ffe4e4;
+      }
+
+      #container {
+        display: flex;
+        align-items: center;
+        justify-content: center;
+        height: 100%;
+        flex-direction: column;
+      }
+
+      #card {
+        padding: 1.5em 1em;
+        border: 1px solid #d90202;
+        background-color: #feb0b0;
+        border-radius: 5px;
+        box-shadow: 2px 2px #cccccc1c;
+        color: #810000 !important;
+      }
+
+      .title {
+        margin-bottom: 1.2em;
+      }
+
+      p {
+        margin-bottom: 0.5em;
+      }
+
+      code,
+      pre {
+        font-family: monospace;
+      }
+
+      .footer {
+        font-size: 0.7em;
+        margin-top: 2em;
+        text-align: right;
+      }
+    </style>
+  </head>
+  <body>
+    <div id="container">
+      <div id="card">
+        <h2 class="title">{{ $title }}</h2>
+        {{ if .Debug }}
+        <pre>{{ .Err }}</pre>
+        {{ end }}
+        <p class="footer">
+          Propulsé par
+          <a href="https://forge.cadoles.com/Cadoles/bouncer">Bouncer</a>.
+        </p>
+      </div>
+    </div>
+  </body>
+</html>
+{{ end }}