From 57fabe8f94a636823ca90d696dd5ed0a02d6ddc7 Mon Sep 17 00:00:00 2001
From: vasileios <zigras00@gmail.com>
Date: Tue, 17 Dec 2024 16:35:41 +0100
Subject: [PATCH] [#4886] Added check for csv uploads to the MimeTypeValidator

There is a problem defining that a file is text/plain or text/csv.

We decided to make some extra checks in order to be closer to that
conclusion because a lot of csv files are not created properly
(according to the proper structure, delimiters etc.) and are treated as
text/plain from magic library.
---
 src/openforms/formio/api/validators.py             | 10 ++++++++++
 src/openforms/formio/tests/files/test-csv-file.csv |  1 +
 src/openforms/formio/tests/test_validators.py      | 14 ++++++++++++++
 3 files changed, 25 insertions(+)
 create mode 100644 src/openforms/formio/tests/files/test-csv-file.csv

diff --git a/src/openforms/formio/api/validators.py b/src/openforms/formio/api/validators.py
index aecbcb06bf..34dcd5aa13 100644
--- a/src/openforms/formio/api/validators.py
+++ b/src/openforms/formio/api/validators.py
@@ -96,6 +96,16 @@ def __call__(self, value: UploadedFile) -> None:
             raise serializers.ValidationError(
                 _("The provided file is not a {file_type}.").format(file_type=f".{ext}")
             )
+        # gh #4886
+        # We need to accept text/plain as a valid MIME type for CSV files.
+        # If the file does not strictly follow the conventions of CSV (e.g. non-standard delimiters),
+        # may not be considered as a valid CSV.
+        elif (
+            value.content_type == "text/csv"
+            and mime_type == "text/plain"
+            and ext == "csv"
+        ):
+            return
         elif mime_type == "image/heic" and value.content_type in (
             "image/heic",
             "image/heif",
diff --git a/src/openforms/formio/tests/files/test-csv-file.csv b/src/openforms/formio/tests/files/test-csv-file.csv
new file mode 100644
index 0000000000..3ae83b7712
--- /dev/null
+++ b/src/openforms/formio/tests/files/test-csv-file.csv
@@ -0,0 +1 @@
+123
diff --git a/src/openforms/formio/tests/test_validators.py b/src/openforms/formio/tests/test_validators.py
index d448a24650..f0d0671d25 100644
--- a/src/openforms/formio/tests/test_validators.py
+++ b/src/openforms/formio/tests/test_validators.py
@@ -188,6 +188,20 @@ def test_multiple_valid_mimetypes_in_zip_files_are_transformed(self):
 
             validator(sample)
 
+    def test_allowed_mime_types_for_csv_files(self):
+        valid_types = ("text/csv", "text/plain")
+        csv_file = TEST_FILES / "test-csv-file.csv"
+        validator = validators.MimeTypeValidator()
+
+        for valid_type in valid_types:
+            sample = SimpleUploadedFile(
+                "test-csv-file.csv",
+                csv_file.read_bytes(),
+                content_type=valid_type,
+            )
+
+            validator(sample)
+
     def test_validate_files_multiple_mime_types(self):
         """Assert that validation of files associated with multiple mime types works