Raise UnsupportedFormat for a malformed DBF stream

src/tablib/formats/_dbf.py

@@ -14,6 +14,7 @@
 
 from .._vendor.dbfpy import dbf, dbfnew
 from .._vendor.dbfpy import record as dbfrecord
+from ..exceptions import UnsupportedFormat
 
 
 class DBFFormat:
@@ -58,10 +59,22 @@ def import_set(cls, dset, in_stream):
         """Returns a dataset from a DBF stream."""
 
         dset.wipe()
-        _dbf = dbf.Dbf(in_stream)
-        dset.headers = _dbf.fieldNames
-        for record in range(_dbf.recordCount):
-            row = [_dbf[record][f] for f in _dbf.fieldNames]
+        # A malformed DBF makes the vendored parser raise a variety of low-level
+        # errors (struct.error, IndexError, UnicodeDecodeError, ...). Report
+        # them as UnsupportedFormat, consistent with detect() treating any
+        # parsing error as "not a valid DBF".
+        try:
+            _dbf = dbf.Dbf(in_stream)
+            headers = _dbf.fieldNames
+            rows = [[_dbf[record][f] for f in headers]
+                    for record in range(_dbf.recordCount)]
+        except Exception as e:
+            raise UnsupportedFormat(
+                'Error parsing DBF: the stream is not a valid DBF file.'
+            ) from e
+
+        dset.headers = headers
+        for row in rows:
             dset.append(row)
 
     @classmethod

tests/test_tablib.py

@@ -1910,6 +1910,19 @@ def test_dbf_import_set(self):
                     )
                 index += 1
 
+    def test_dbf_import_malformed(self):
+        """A malformed DBF stream raises UnsupportedFormat rather than a raw
+        struct.error / IndexError from the vendored parser."""
+        data.append(self.john)
+        data.headers = self.headers
+        good = data.dbf
+        # truncate the DBF inside its header
+        truncated = good[:16]
+        with self.assertRaises(UnsupportedFormat):
+            tablib.Dataset().load(truncated, format='dbf')
+        with self.assertRaises(UnsupportedFormat):
+            tablib.Dataset().load(b'not a dbf file', format='dbf')
+
     def test_dbf_export_set(self):
         """Test DBF import."""
         data.append(self.john)