pySim-shell: JSONpath support for updating files/records

Change-Id: Iad09b3d878b8b58ad34cb549c80f8a6eb3149faa

contrib/jenkins.sh

@@ -14,6 +14,7 @@ virtualenv -p python3 venv --system-site-packages
 pip install pytlv
 pip install pyyaml
 pip install cmd2
+pip install jsonpath-ng
 
 # Execute automatically discovered unit tests first
 python -m unittest discover -v -s tests/

docs/shell.rst

@@ -226,6 +226,33 @@ update_binary_decoded
    :module: pySim.filesystem
    :func: TransparentEF.ShellCommands.upd_bin_dec_parser
 
+In normal operation, update_binary_decoded needs a JSON document representing the entire file contents as
+input.  This can be inconvenient if you want to keep 99% of the content but just toggle one specific
+parameter.   That's where the JSONpath support comes in handy:  You can specify a JSONpath to an element
+inside the document as well as a new value for tat field:
+
+Th below example demonstrates this by modifying the ofm field within EF.AD:
+
+::
+
+  pySIM-shell (MF/ADF.USIM/EF.AD)> read_binary_decoded
+  {
+      "ms_operation_mode": "normal",
+      "specific_facilities": {
+          "ofm": true
+      },
+      "len_of_mnc_in_imsi": 2
+  }
+  pySIM-shell (MF/ADF.USIM/EF.AD)> update_binary_decoded --json-path specific_facilities.ofm false
+  pySIM-shell (MF/ADF.USIM/EF.AD)> read_binary_decoded
+  {
+      "ms_operation_mode": "normal",
+      "specific_facilities": {
+          "ofm": false
+      },
+      "len_of_mnc_in_imsi": 2
+  }
+
 
 
 cmd2 settable parameters

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)
+

requirements.txt

@@ -2,3 +2,4 @@ pyscard
 serial
 pytlv
 cmd2
+jsonpath-ng

setup.py

@@ -13,6 +13,7 @@ setup(
         "serial",
         "pytlv",
         "cmd2"
+        "jsonpath-ng"
     ],
     scripts=[
         'pySim-prog.py',