implement OCM wellknown for discovery

changelog/unreleased/implement-ocm-wellknown.md

@@ -0,0 +1,5 @@
+Enhancement: Implement OCM well-known endpoint
+
+The `wellknown` service now implements the `/.well-known/ocm` endpoint for OCM discovery. The unused endpoints for openid connect and webfinger have been removed. This aligns the wellknown implementation with the master branch.
+
+https://github.com/cs3org/reva/pull/4809

internal/http/services/wellknown/ocm.go

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+// Copyright 2018-2024 CERN
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// In applying this license, CERN does not waive the privileges and immunities
+// granted to it by virtue of its status as an Intergovernmental Organization
+// or submit itself to any jurisdiction.
+
+package wellknown
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/url"
+	"path/filepath"
+
+	"github.com/cs3org/reva/v2/pkg/appctx"
+)
+
+const OCMAPIVersion = "1.1.0"
+
+type OcmProviderConfig struct {
+	OCMPrefix    string `docs:"ocm;The prefix URL where the OCM API is served."                                   mapstructure:"ocm_prefix"`
+	Endpoint     string `docs:"This host's full URL. If it's not configured, it is assumed OCM is not available." mapstructure:"endpoint"`
+	Provider     string `docs:"reva;A friendly name that defines this service."                                   mapstructure:"provider"`
+	WebdavRoot   string `docs:"/remote.php/dav/ocm;The root URL of the WebDAV endpoint to serve OCM shares."      mapstructure:"webdav_root"`
+	WebappRoot   string `docs:"/external/sciencemesh;The root URL to serve Web apps via OCM."                     mapstructure:"webapp_root"`
+	EnableWebapp bool   `docs:"false;Whether web apps are enabled in OCM shares."                                 mapstructure:"enable_webapp"`
+	EnableDatatx bool   `docs:"false;Whether data transfers are enabled in OCM shares."                           mapstructure:"enable_datatx"`
+}
+
+type OcmDiscoveryData struct {
+	Enabled       bool            `json:"enabled"       xml:"enabled"`
+	APIVersion    string          `json:"apiVersion"    xml:"apiVersion"`
+	Endpoint      string          `json:"endPoint"      xml:"endPoint"`
+	Provider      string          `json:"provider"      xml:"provider"`
+	ResourceTypes []resourceTypes `json:"resourceTypes" xml:"resourceTypes"`
+	Capabilities  []string        `json:"capabilities"  xml:"capabilities"`
+}
+
+type resourceTypes struct {
+	Name       string            `json:"name"`
+	ShareTypes []string          `json:"shareTypes"`
+	Protocols  map[string]string `json:"protocols"`
+}
+
+type wkocmHandler struct {
+	data *OcmDiscoveryData
+}
+
+func (c *OcmProviderConfig) ApplyDefaults() {
+	if c.OCMPrefix == "" {
+		c.OCMPrefix = "ocm"
+	}
+	if c.Provider == "" {
+		c.Provider = "reva"
+	}
+	if c.WebdavRoot == "" {
+		c.WebdavRoot = "/remote.php/dav/ocm/"
+	}
+	if c.WebdavRoot[len(c.WebdavRoot)-1:] != "/" {
+		c.WebdavRoot += "/"
+	}
+	if c.WebappRoot == "" {
+		c.WebappRoot = "/external/sciencemesh/"
+	}
+	if c.WebappRoot[len(c.WebappRoot)-1:] != "/" {
+		c.WebappRoot += "/"
+	}
+}
+
+func (h *wkocmHandler) init(c *OcmProviderConfig) {
+	// generates the (static) data structure to be exposed by /.well-known/ocm:
+	// first prepare an empty and disabled payload
+	c.ApplyDefaults()
+	d := &OcmDiscoveryData{}
+	d.Enabled = false
+	d.Endpoint = ""
+	d.APIVersion = OCMAPIVersion
+	d.Provider = c.Provider
+	d.ResourceTypes = []resourceTypes{{
+		Name:       "file",
+		ShareTypes: []string{},
+		Protocols:  map[string]string{},
+	}}
+	d.Capabilities = []string{}
+
+	if c.Endpoint == "" {
+		h.data = d
+		return
+	}
+
+	endpointURL, err := url.Parse(c.Endpoint)
+	if err != nil {
+		h.data = d
+		return
+	}
+
+	// now prepare the enabled one
+	d.Enabled = true
+	d.Endpoint, _ = url.JoinPath(c.Endpoint, c.OCMPrefix)
+	rtProtos := map[string]string{}
+	// webdav is always enabled
+	rtProtos["webdav"] = filepath.Join(endpointURL.Path, c.WebdavRoot)
+	if c.EnableWebapp {
+		rtProtos["webapp"] = filepath.Join(endpointURL.Path, c.WebappRoot)
+	}
+	if c.EnableDatatx {
+		rtProtos["datatx"] = filepath.Join(endpointURL.Path, c.WebdavRoot)
+	}
+	d.ResourceTypes = []resourceTypes{{
+		Name:       "file",           // so far we only support `file`
+		ShareTypes: []string{"user"}, // so far we only support `user`
+		Protocols:  rtProtos,         // expose the protocols as per configuration
+	}}
+	// for now we hardcode the capabilities, as this is currently only advisory
+	d.Capabilities = []string{"/invite-accepted"}
+	h.data = d
+}
+
+// This handler implements the OCM discovery endpoint specified in
+// https://cs3org.github.io/OCM-API/docs.html?repo=OCM-API&user=cs3org#/paths/~1ocm-provider/get
+func (h *wkocmHandler) Ocm(w http.ResponseWriter, r *http.Request) {
+	log := appctx.GetLogger(r.Context())
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusOK)
+	if r.UserAgent() == "Nextcloud Server Crawler" {
+		// Nextcloud decided to only support OCM 1.0 and 1.1, not any 1.x as per SemVer. See
+		// https://github.com/nextcloud/server/pull/39574#issuecomment-1679191188
+		h.data.APIVersion = "1.1"
+	} else {
+		h.data.APIVersion = OCMAPIVersion
+	}
+	indented, _ := json.MarshalIndent(h.data, "", "   ")
+	if _, err := w.Write(indented); err != nil {
+		log.Err(err).Msg("Error writing to ResponseWriter")
+	}
+}