Improves season 1 level 3 solution (#113)

* Reversing Season 2 level-3 with level-4 due to another initiative we are working on.

* adds mocha

* fixes template reference

* replaces executable

* improves the solution in Season-1/Level-3

* Potential fix for code scanning alert no. 46: Uncontrolled data used in path expression

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

---------

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

Author: jkcso

Season-1/Level-3/solution.py

@@ -1,34 +1,61 @@
-import os
+# Model solution follows
 
-# Example of a secure function that doesn't suffer from path traversal
-def safe_path(path):
-    base_dir = os.path.dirname(os.path.abspath(__file__))
-    filepath = os.path.normpath(os.path.join(base_dir, path))
-    if base_dir != os.path.commonpath([base_dir, filepath]):
-        return None
-    return filepath
-
-# Following the above, this is the secure version of the respective function on code.py
-def get_prof_picture(self, path=None):
-    # setting a profile picture is optional
-    if not path:
-        pass
-
-    # defends against path traversal attacks
-    if path.startswith('/') or path.startswith('..'):
-        return None
-
-    # builds path
-    base_dir = os.path.dirname(os.path.abspath(__file__))
-    prof_picture_path = os.path.normpath(os.path.join(base_dir, path))
-    if base_dir != os.path.commonpath([base_dir, prof_picture_path]):
-        return None
-
-    with open(prof_picture_path, 'rb') as pic:
-        picture = bytearray(pic.read())
-
-    # assume that image is returned on screen after this
-    return prof_picture_path
+import os
+from flask import Flask, request
+
+### Unrelated to the exercise -- Starts here -- Please ignore
+app = Flask(__name__)
+@app.route("/")
+def source():
+    TaxPayer('foo', 'bar').get_tax_form_attachment(request.args["input"])
+    TaxPayer('foo', 'bar').get_prof_picture(request.args["input"])
+### Unrelated to the exercise -- Ends here -- Please ignore
+
+class TaxPayer:
+
+    def __init__(self, username, password):
+        self.username = username
+        self.password = password
+        self.prof_picture = None
+        self.tax_form_attachment = None
+
+    # returns the path of an optional profile picture that users can set
+    def get_prof_picture(self, path=None):
+        # setting a profile picture is optional
+        if not path:
+            pass
+
+        # builds path
+        base_dir = os.path.dirname(os.path.abspath(__file__))
+        prof_picture_path = os.path.normpath(os.path.join(base_dir, path))
+        if not prof_picture_path.startswith(base_dir):
+            return None
+
+        with open(prof_picture_path, 'rb') as pic:
+            picture = bytearray(pic.read())
+
+        # assume that image is returned on screen after this
+        return prof_picture_path
+
+    # returns the path of an attached tax form that every user should submit
+    def get_tax_form_attachment(self, path=None):
+        tax_data = None
+
+        # A tax form is required
+        if not path:
+            raise Exception("Error: Tax form is required for all users")
+
+        # Validate the path to prevent path traversal attacks
+        base_dir = os.path.dirname(os.path.abspath(__file__))
+        tax_form_path = os.path.normpath(os.path.join(base_dir, path))
+        if not tax_form_path.startswith(base_dir):
+            return None
+
+        with open(tax_form_path, 'rb') as form:
+            tax_data = bytearray(form.read())
+
+        # assume that tax data is returned on screen after this
+        return tax_form_path
 
 
 # Solution explanation