Change in pysim[master]: pySim-shell: JSONpath support for updating files/records

laforge gerrit-no-reply at lists.osmocom.org
Tue Apr 6 22:34:06 UTC 2021


laforge has uploaded this change for review. ( https://gerrit.osmocom.org/c/pysim/+/23661 )


Change subject: pySim-shell: JSONpath support for updating files/records
......................................................................

pySim-shell: JSONpath support for updating files/records

Change-Id: Iad09b3d878b8b58ad34cb549c80f8a6eb3149faa
---
M docs/shell.rst
M pySim/filesystem.py
A pySim/jsonpath.py
M requirements.txt
M setup.py
5 files changed, 79 insertions(+), 2 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/pysim refs/changes/61/23661/1

diff --git a/docs/shell.rst b/docs/shell.rst
index 2edebbf..3cfc849 100644
--- a/docs/shell.rst
+++ b/docs/shell.rst
@@ -226,6 +226,33 @@
    :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
diff --git a/pySim/filesystem.py b/pySim/filesystem.py
index a65a764..f8443f3 100644
--- a/pySim/filesystem.py
+++ b/pySim/filesystem.py
@@ -35,6 +35,7 @@
 
 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 @@
 
         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 @@
         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)
 
diff --git a/pySim/jsonpath.py b/pySim/jsonpath.py
new file mode 100644
index 0000000..012d1d9
--- /dev/null
+++ b/pySim/jsonpath.py
@@ -0,0 +1,34 @@
+import json
+import pprint
+
+from jsonpath_ng import jsonpath, parse
+
+"""JSONpath utliity 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.
+"""
+
+
+def js_path_find(js_dict, js_path):
+    """Find/Match a JSON path within a givne JSON-serializable dict.
+    Args:
+        js_dict : JSON-serializable dict to operate on
+        js_path : JSONpath string
+    Returns: Result of the JSONpath expression
+    """
+    jsonpath_expr = 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 givne 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 = parse(js_path)
+    jsonpath_expr.find(js_dict)
+    jsonpath_expr.update(js_dict, new_val)
+
diff --git a/requirements.txt b/requirements.txt
index 978a3db..f203ed1 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,3 +2,4 @@
 serial
 pytlv
 cmd2
+jsonpath-ng
diff --git a/setup.py b/setup.py
index d9f742c..a02e327 100644
--- a/setup.py
+++ b/setup.py
@@ -13,6 +13,7 @@
         "serial",
         "pytlv",
         "cmd2"
+        "jsonpath-ng"
     ],
     scripts=[
         'pySim-prog.py',

-- 
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Gerrit-Project: pysim
Gerrit-Branch: master
Gerrit-Change-Id: Iad09b3d878b8b58ad34cb549c80f8a6eb3149faa
Gerrit-Change-Number: 23661
Gerrit-PatchSet: 1
Gerrit-Owner: laforge <laforge at osmocom.org>
Gerrit-MessageType: newchange
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