Add configuration for custom path segment

To support SCEP clients that expect a specific path segment in
a SCEP URL, a new "customPath" option was added to the SCEP
provisioner configuration. The configuration can be used to set
a specific path (segment) that the SCEP provisioner will respond to.

authority/provisioner/scep.go

@@ -26,10 +26,18 @@ type SCEP struct {
 	// Numerical identifier for the ContentEncryptionAlgorithm as defined in github.com/mozilla-services/pkcs7
 	// at https://github.com/mozilla-services/pkcs7/blob/33d05740a3526e382af6395d3513e73d4e66d1cb/encrypt.go#L63
 	// Defaults to 0, being DES-CBC
-	EncryptionAlgorithmIdentifier int      `json:"encryptionAlgorithmIdentifier,omitempty"`
+	EncryptionAlgorithmIdentifier int `json:"encryptionAlgorithmIdentifier,omitempty"`
-	Options                       *Options `json:"options,omitempty"`
+	// CustomPath is used to specify a custom path on which the SCEP provisioner will be made
-	Claims                        *Claims  `json:"claims,omitempty"`
+	// available. By default a SCEP provisioner is available at
-	claimer                       *Claimer
+	// https://<address>:<port>/scep/<provisionerName> and requests performed looking similar
+	// to https://<address>:<port>/scep/<provisionerName>?operations=GetCACert. When CustomPath
+	// is set, the SCEP URL will be https://<address>:<port>/scep/<provisionerName>/<customPath>,
+	// resulting in SCEP clients that expect a specific path, such as "/pkiclient.exe", to be
+	// able to interact with the SCEP provisioner.
+	CustomPath string   `json:"customPath,omitempty"`
+	Options    *Options `json:"options,omitempty"`
+	Claims     *Claims  `json:"claims,omitempty"`
+	claimer    *Claimer
 
 	secretChallengePassword string
 	encryptionAlgorithm     int

scep/api/api.go

@@ -66,7 +66,9 @@ func New(scepAuth scep.Interface) api.RouterHandler {
 // Route traffic and implement the Router interface.
 func (h *Handler) Route(r api.Router) {
 	getLink := h.Auth.GetLinkExplicit
+	r.MethodFunc(http.MethodGet, getLink("{provisionerName}/{customPath}*", false, nil), h.lookupProvisioner(h.Get))
 	r.MethodFunc(http.MethodGet, getLink("{provisionerName}", false, nil), h.lookupProvisioner(h.Get))
+	r.MethodFunc(http.MethodPost, getLink("{provisionerName}/{customPath}*", false, nil), h.lookupProvisioner(h.Post))
 	r.MethodFunc(http.MethodPost, getLink("{provisionerName}", false, nil), h.lookupProvisioner(h.Post))
 }
 
@@ -191,6 +193,13 @@ func (h *Handler) lookupProvisioner(next nextHTTP) nextHTTP {
 			return
 		}
 
+		customPathParam := chi.URLParam(r, "customPath")
+		customPath, err := url.PathUnescape(customPathParam)
+		if err != nil {
+			api.WriteError(w, err)
+			return
+		}
+
 		p, err := h.Auth.LoadProvisionerByName(provisionerName)
 		if err != nil {
 			api.WriteError(w, err)
@@ -203,6 +212,12 @@ func (h *Handler) lookupProvisioner(next nextHTTP) nextHTTP {
 			return
 		}
 
+		configuredCustomPath := strings.Trim(prov.CustomPath, "/")
+		if customPath != configuredCustomPath {
+			api.WriteError(w, errors.Errorf("custom path requested '%s' is not the expected path '%s'", customPath, configuredCustomPath))
+			return
+		}
+
 		ctx := r.Context()
 		ctx = context.WithValue(ctx, scep.ProvisionerContextKey, scep.Provisioner(prov))
 		next(w, r.WithContext(ctx))