pySim-shell: JSONpath support for updating files/records

Change-Id: Iad09b3d878b8b58ad34cb549c80f8a6eb3149faa

pySim/filesystem.py

@@ -35,6 +35,7 @@ from typing import cast, Optional, Iterable, List, Any, Dict, Tuple
 
 from pySim.utils import sw_match, h2b, b2h, is_hex
 from pySim.exceptions import *
+from pySim.jsonpath import js_path_find, js_path_modify
 
 class CardFile(object):
     """Base class for all objects in the smart card filesystem.
@@ -418,10 +419,16 @@ class TransparentEF(CardEF):
 
         upd_bin_dec_parser = argparse.ArgumentParser()
         upd_bin_dec_parser.add_argument('data', help='Abstract data (JSON format) to write')
+        upd_bin_dec_parser.add_argument('--json-path', type=str,
+                                        help='JSON path to modify specific element of file only')
         @cmd2.with_argparser(upd_bin_dec_parser)
         def do_update_binary_decoded(self, opts):
             """Encode + Update (Write) data of a transparent EF"""
-            data_json = json.loads(opts.data)
+            if opts.json_path:
+                (data_json, sw) = self._cmd.rs.read_binary_dec()
+                js_path_modify(data_json, opts.json_path, json.loads(opts.data))
+            else:
+                data_json = json.loads(opts.data)
             (data, sw) = self._cmd.rs.update_binary_dec(data_json)
             if data:
                 self._cmd.poutput_json(data)
@@ -574,10 +581,17 @@ class LinFixedEF(CardEF):
         upd_rec_dec_parser = argparse.ArgumentParser()
         upd_rec_dec_parser.add_argument('record_nr', type=int, help='Number of record to be read')
         upd_rec_dec_parser.add_argument('data', help='Data bytes (hex format) to write')
+        upd_rec_dec_parser.add_argument('--json-path', type=str,
+                                        help='JSON path to modify specific element of record only')
         @cmd2.with_argparser(upd_rec_dec_parser)
         def do_update_record_decoded(self, opts):
             """Encode + Update (write) data to a record-oriented EF"""
-            (data, sw) = self._cmd.rs.update_record_dec(opts.record_nr, opts.data)
+            if opts.json_path:
+                (data_json, sw) = self._cmd.rs.read_record_dec(opts.record_nr)
+                js_path_modify(data_json, opts.json_path, json.loads(opts.data))
+            else:
+                data_json = json.loads(opts.data)
+            (data, sw) = self._cmd.rs.update_record_dec(opts.record_nr, data_json)
             if data:
                 self._cmd.poutput(data)
 

pySim/jsonpath.py

@@ -0,0 +1,48 @@
+# coding=utf-8
+import json
+import pprint
+import jsonpath_ng
+
+"""JSONpath utility functions as needed within pysim.
+
+As pySim-sell has the ability to represent SIM files as JSON strings,
+adding JSONpath allows us to conveniently modify individual sub-fields
+of a file or record in its JSON representation.
+"""
+
+# (C) 2021 by Harald Welte <laforge@osmocom.org>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+def js_path_find(js_dict, js_path):
+    """Find/Match a JSON path within a given JSON-serializable dict.
+    Args:
+        js_dict : JSON-serializable dict to operate on
+        js_path : JSONpath string
+    Returns: Result of the JSONpath expression
+    """
+    jsonpath_expr = jsonpath_ng.parse(js_path)
+    return jsonpath_expr.find(js_dict)
+
+def js_path_modify(js_dict, js_path, new_val):
+    """Find/Match a JSON path within a given JSON-serializable dict.
+    Args:
+        js_dict : JSON-serializable dict to operate on
+        js_path : JSONpath string
+        new_val : New value for field in js_dict at js_path
+    """
+    jsonpath_expr = jsonpath_ng.parse(js_path)
+    jsonpath_expr.find(js_dict)
+    jsonpath_expr.update(js_dict, new_val)
+