Encrypt access tokens

src/core/wopiutils.py

@@ -20,9 +20,9 @@
 from urllib.parse import quote_plus as url_quote_plus
 import http.client
 import flask
-import jwt
 from werkzeug.utils import secure_filename
 import core.commoniface as common
+from jwcrypto import jwk, jwe, jwt
 
 # this is the xattr key used for conflicts resolution on the remote storage
 LASTSAVETIMEKEY = 'iop.wopi.lastwritetime'
@@ -99,10 +99,10 @@ def validateAndLogHeaders(op):
     srv.refreshconfig()
     # validate the access token
     try:
-        acctok = jwt.decode(flask.request.args['access_token'], srv.wopisecret, algorithms=['HS256'])
+        acctok = decodeAccessToken(flask.request.args['access_token'])
         if acctok['exp'] < time.time() or 'cs3org:wopiserver' not in acctok['iss']:
-            raise jwt.exceptions.ExpiredSignatureError
-    except (jwt.exceptions.DecodeError, jwt.exceptions.ExpiredSignatureError, KeyError) as e:
+            raise jwt.JWTExpired
+    except (jwt.JWTMissingKey, jwt.JWTExpired, jwe.InvalidJWEData, ValueError) as e:
         log.info('msg="Expired or malformed token" client="%s" requestedUrl="%s" error="%s" token="%s"' %
                  (flask.request.remote_addr, flask.request.base_url, str(type(e)) + ': ' + str(e), flask.request.args['access_token']))
         return 'Invalid access token', http.client.UNAUTHORIZED
@@ -202,11 +202,22 @@ def generateAccessToken(userid, fileid, viewmode, user, folderurl, endpoint, app
         # does not set appname when the app is not proxied, so we optimistically assume it's Collabora and let it go)
         log.info('msg="Forcing read-only access to ODF file" filename="%s"' % statinfo['filepath'])
         viewmode = ViewMode.READ_ONLY
-    acctok = jwt.encode({'userid': userid, 'wopiuser': wopiuser, 'filename': statinfo['filepath'], 'username': username,
-                         'viewmode': viewmode.value, 'folderurl': folderurl, 'endpoint': endpoint,
-                         'appname': appname, 'appediturl': appediturl, 'appviewurl': appviewurl,
-                         'exp': exptime, 'iss': 'cs3org:wopiserver:%s' % WOPIVER},    # standard claims
-                        srv.wopisecret, algorithm='HS256')
+
+    acctokValues = {
+        'userid': userid,
+        'wopiuser': wopiuser,
+        'filename': statinfo['filepath'],
+        'username': username,
+        'viewmode': viewmode.value,
+        'folderurl': folderurl,
+        'endpoint': endpoint,
+        'appname': appname,
+        'appediturl': appediturl,
+        'appviewurl': appviewurl,
+        'exp': exptime,
+        'iss': 'cs3org:wopiserver:%s' % WOPIVER
+    }
+    acctok = encodeAccessToken(acctokValues)
     log.info('msg="Access token generated" userid="%s" wopiuser="%s" mode="%s" endpoint="%s" filename="%s" inode="%s" '
              'mtime="%s" folderurl="%s" appname="%s" expiration="%d" token="%s"' %
              (userid[-20:], wopiuser if wopiuser != userid else username, viewmode, endpoint,
@@ -216,6 +227,31 @@ def generateAccessToken(userid, fileid, viewmode, user, folderurl, endpoint, app
     return statinfo['inode'], acctok, viewmode
 
 
+def encodeAccessToken(acctok):
+    # Create a signed JWT
+    token = jwt.JWT(header={"alg": "HS256"}, claims=acctok)
+    key = jwk.JWK.from_password(srv.wopisecret)
+    token.make_signed_token(key)
+
+    # if enabled, create an encrypted JWT (JWE)
+    if srv.config.getboolean('security', "encrcyptjwetoken"):
+        token = jwt.JWT(header={"alg": "A256KW", "enc": "A256CBC-HS512"}, claims=token.serialize())
+        token.make_encrypted_token(srv.tokensecret)
+
+    return token.serialize()
+
+
+def decodeAccessToken(token):
+    # if enabled, decrypt the JWE
+    if srv.config.getboolean('security', "encrcyptjwetoken"):
+        token = jwt.JWT(key=srv.tokensecret, jwt=token, expected_type="JWE").claims
+
+    # decode the signed JWT
+    token = jwt.JWT(key=jwk.JWK.from_password(srv.wopisecret), jwt=token, expected_type="JWS")
+
+    return json.loads(token.claims)
+
+
 def encodeLock(lock):
     '''Generates the lock payload for the storage given the raw metadata'''
     if lock:

src/wopiserver.py

@@ -23,7 +23,7 @@
     import flask                   # Flask app server
     from werkzeug.exceptions import NotFound as Flask_NotFound
     from werkzeug.exceptions import MethodNotAllowed as Flask_MethodNotAllowed
-    import jwt                     # JSON Web Tokens support
+    from jwcrypto import jwk, jwe, jwt               # JSON Web Tokens support
     from prometheus_flask_exporter import PrometheusMetrics    # Prometheus support
 
 except ImportError:
@@ -110,6 +110,8 @@ def init(cls):
             cls.codetypes = cls.config.get('general', 'codeofficetypes', fallback='.odt .ods .odp').split()
             with open(cls.config.get('security', 'wopisecretfile')) as s:
                 cls.wopisecret = s.read().strip('\n')
+            if cls.config.getboolean('security', "encrcyptjwetoken"):
+                initEncryptionKey(cls)
             with open(cls.config.get('security', 'iopsecretfile')) as s:
                 cls.iopsecret = s.read().strip('\n')
             cls.tokenvalidity = cls.config.getint('general', 'tokenvalidity')
@@ -358,11 +360,11 @@ def iopDownload():
     '''Returns the file's content for a given valid access token. Used as a download URL,
        so that the path and possibly the x-access-token are never explicitly visible.'''
     try:
-        acctok = jwt.decode(flask.request.args['access_token'], Wopi.wopisecret, algorithms=['HS256'])
+        acctok = utils.decodeAccessToken(flask.request.args['access_token'])
         if acctok['exp'] < time.time():
-            raise jwt.exceptions.ExpiredSignatureError
+            raise jwt.JWTExpired
         return core.wopi.getFile(0, acctok)   # note that here we exploit the non-dependency from fileid
-    except (jwt.exceptions.DecodeError, jwt.exceptions.ExpiredSignatureError, KeyError) as e:
+    except (jwt.JWTMissingKey, jwt.JWTExpired, jwe.InvalidJWEData, ValueError) as e:
         Wopi.log.info('msg="Expired or malformed token" client="%s" requestedUrl="%s" error="%s" token="%s"' %
                       (flask.request.remote_addr, flask.request.base_url, e, flask.request.args['access_token']))
         return 'Invalid access token', http.client.UNAUTHORIZED
@@ -619,6 +621,21 @@ def cboxDownload_deprecated():
     return iopDownload()
 
 
+def initEncryptionKey(cls):
+    try:
+        with open(cls.config.get('security', 'jwesecretfile'), 'r') as kf:
+            key_data = kf.read()
+        key = jwk.JWK.from_json(key_data)
+    except Exception as e:
+        Wopi.log.info('msg="No encryption key file found: %s"' % str(e))
+        try:
+            key = jwk.JWK.generate(kty='oct', size=256)
+            Wopi.log.info('msg="Generating new encryption key"')
+            with open(cls.config.get('security', 'jwesecretfile'), 'w') as kwf:
+                kwf.write(key.export())
+        except Exception as ge:
+            Wopi.log.critical('msg="Error during encryption key generation: %s"' % str(ge))
+    cls.tokensecret = key
 #
 # Start the Flask endless listening loop
 #