From 779092b0cd46b493faa6a40d2ecfb9d1df659750 Mon Sep 17 00:00:00 2001
From: Harald Welte <laforge@osmocom.org>
Date: Fri, 22 Nov 2024 15:55:35 +0100
Subject: [PATCH] esim.saip: Fix computation of file content

When generating the file content (body), we need to proceed in the
following order:

1a) If FCP contains fillPattern/repeatPattern, compute file content from those

1b) If FCP doesn't contain fillPattern/repeatPattern but template
    exists, compute file content from template

2)  Apply any fillFileConten / fillFileOffset from the SAIP File on top
    of the above

Change-Id: I822bb5fbec11a3be35910a496af7168458fd949c
Closes: OS#6642
---
 pySim/esim/saip/__init__.py | 21 +++++++++++++++++----
 pySim/ts_102_222.py         | 10 ++++++++++
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/pySim/esim/saip/__init__.py b/pySim/esim/saip/__init__.py
index 3490f64c..355e6b9d 100644
--- a/pySim/esim/saip/__init__.py
+++ b/pySim/esim/saip/__init__.py
@@ -18,6 +18,7 @@
 import logging
 import abc
 import io
+import os
 from typing import Tuple, List, Optional, Dict, Union
 from collections import OrderedDict
 import asn1tools
@@ -25,6 +26,7 @@ from osmocom.utils import b2h, h2b, Hexstr
 from osmocom.tlv import BER_TLV_IE, bertlv_parse_tag, bertlv_parse_len
 from osmocom.construct import build_construct, parse_construct, GreedyInteger
 
+from pySim import ts_102_222
 from pySim.utils import dec_imsi
 from pySim.ts_102_221 import FileDescriptor
 from pySim.filesystem import CardADF, Path
@@ -352,18 +354,29 @@ class File:
         ret += self.file_content_to_tuples()
         return ret
 
-    @staticmethod
-    def file_content_from_tuples(l: List[Tuple]) -> Optional[bytes]:
+    def expand_fill_pattern(self) -> bytes:
+        """Expand the fill/repeat pattern as per TS 102 222 Section 6.3.2.2.2"""
+        return ts_102_222.expand_pattern(self.fill_pattern, self.fill_pattern_repeat, self.file_size)
+
+    def file_content_from_tuples(self, l: List[Tuple]) -> Optional[bytes]:
         """linearize a list of fillFileContent / fillFileOffset tuples into a stream of bytes."""
         stream = io.BytesIO()
+        # Providing file content within "fillFileContent" / "fillFileOffset" shall have the same effect as
+        # creating a file with a fill/repeat pattern and thereafter updating the content via Update.
+        # Step 1: Fill with pattern from Fcp or Template
+        if self.fill_pattern:
+            stream.write(self.expand_fill_pattern())
+        elif self.template and self.template.default_val:
+            stream.write(self.template.expand_default_value_pattern(self.file_size))
+        stream.seek(0)
+        # then process the fillFileContent/fillFileOffset
         for k, v in l:
             if k == 'doNotCreate':
                 return None
             if k == 'fileDescriptor':
                 pass
             elif k == 'fillFileOffset':
-                # FIXME: respect the fillPattern!
-                stream.write(b'\xff' * v)
+                stream.seek(v, os.SEEK_CUR)
             elif k == 'fillFileContent':
                 stream.write(v)
             else:
diff --git a/pySim/ts_102_222.py b/pySim/ts_102_222.py
index e54c1969..74eb2c3a 100644
--- a/pySim/ts_102_222.py
+++ b/pySim/ts_102_222.py
@@ -25,6 +25,16 @@ from osmocom.utils import b2h, auto_uint8, auto_uint16, is_hexstr
 
 from pySim.ts_102_221 import *
 
+def expand_pattern(pattern: bytes, repeat: bool, size: int) -> bytes:
+    """Expand the fill/repeat pattern as per TS 102 222 Section 6.3.2.2.2 Tags C1/C2."""
+    if not repeat:
+        pad_len = size - len(pattern)
+        return pattern + pattern[-1:] * pad_len
+    else:
+        count = size // len(pattern)
+        part_len = size - count * len(pattern)
+        return pattern * count + pattern[:part_len]
+
 @with_default_category('TS 102 222 Administrative Commands')
 class Ts102222Commands(CommandSet):
     """Administrative commands for telecommunication applications."""