Fix sql injection issues (#807)

Currently, we have some sql injection issues in our code which
DeepSource detects for us, but some of them we ignored.

## What is the new behavior?

This PR should fix them.

python-sdk/src/astro/databases/base.py

@@ -101,6 +101,21 @@ def run_sql(
             result = self.connection.execute(sql_statement, parameters)
         return result
 
+    def columns_exist(self, table: Table, columns: list[str]) -> bool:
+        """
+        Check that a list of columns exist in the given table.
+
+        :param table: The table to check in.
+        :param columns: The columns to check.
+
+        :returns: whether the columns exist in the table or not.
+        """
+        sqla_table = self.get_sqla_table(table)
+        return all(
+            any(sqla_column.name == column for sqla_column in sqla_table.columns)
+            for column in columns
+        )
+
     def table_exists(self, table: Table) -> bool:
         """
         Check if a table exists in the database.
@@ -492,15 +507,13 @@ def export_table_to_pandas_dataframe(self, source_table: Table) -> pd.DataFrame:
 
         :param source_table: An existing table in the database
         """
-        table_qualified_name = self.get_table_qualified_name(source_table)
         if self.table_exists(source_table):
-            return pd.read_sql(
-                # We are avoiding SQL injection by confirming the table exists before this statement
-                f"SELECT * FROM {table_qualified_name}",  # skipcq BAN-B608
-                con=self.sqlalchemy_engine,
-            )
+            sqla_table = self.get_sqla_table(source_table)
+            return pd.read_sql(sql=sqla_table.select(), con=self.sqlalchemy_engine)
+
+        table_qualified_name = self.get_table_qualified_name(source_table)
         raise NonExistentTableException(
-            "The table %s does not exist" % table_qualified_name
+            f"The table {table_qualified_name} does not exist"
         )
 
     def export_table_to_file(

python-sdk/src/astro/databases/google/bigquery.py

@@ -197,20 +197,31 @@ def merge_table(
         target_table_name = self.get_table_qualified_name(target_table)
         source_table_name = self.get_table_qualified_name(source_table)
 
-        statement = f"MERGE {target_table_name} T USING {source_table_name} S\
-            ON {' AND '.join(['T.' + col + '= S.' + col for col in target_conflict_columns])}\
-            WHEN NOT MATCHED BY TARGET THEN INSERT ({','.join(target_columns)}) VALUES ({','.join(source_columns)})"
-
-        update_statement_map = ", ".join(
-            [
-                f"T.{target_columns[idx]}=S.{source_columns[idx]}"
-                for idx in range(len(target_columns))
-            ]
+        insert_statement = (
+            f"INSERT ({', '.join(target_columns)}) VALUES ({', '.join(source_columns)})"
+        )
+        merge_statement = (
+            f"MERGE {target_table_name} T USING {source_table_name} S"
+            f" ON {' AND '.join(f'T.{col}=S.{col}' for col in target_conflict_columns)}"
+            f" WHEN NOT MATCHED BY TARGET THEN {insert_statement}"
         )
         if if_conflicts == "update":
-            update_statement = f"UPDATE SET {update_statement_map}"  # skipcq: BAN-B608
-            statement += f" WHEN MATCHED THEN {update_statement}"
-        self.run_sql(sql_statement=statement)
+            update_statement_map = ", ".join(
+                f"T.{col}=S.{source_columns[idx]}"
+                for idx, col in enumerate(target_columns)
+            )
+            if not self.columns_exist(source_table, source_columns):
+                raise ValueError(
+                    f"Not all the columns provided exist for {source_table_name}!"
+                )
+            if not self.columns_exist(target_table, target_columns):
+                raise ValueError(
+                    f"Not all the columns provided exist for {target_table_name}!"
+                )
+            # Note: Ignoring below sql injection warning, as we validate that the table columns exist beforehand.
+            update_statement = f"UPDATE SET {update_statement_map}"  # skipcq BAN-B608
+            merge_statement += f" WHEN MATCHED THEN {update_statement}"
+        self.run_sql(sql_statement=merge_statement)
 
     def is_native_load_file_available(
         self, source_file: File, target_table: Table

python-sdk/tests/databases/test_all_databases.py

@@ -0,0 +1,63 @@
+"""Tests all Database implementations."""
+import pathlib
+
+import pandas as pd
+import pytest
+
+from astro.constants import Database
+from astro.files import File
+from astro.settings import SCHEMA
+from astro.sql.table import Metadata, Table
+
+CWD = pathlib.Path(__file__).parent
+
+
+@pytest.mark.integration
+@pytest.mark.parametrize(
+    "database_table_fixture",
+    [
+        {
+            "database": Database.BIGQUERY,
+            "file": File(str(pathlib.Path(CWD.parent, "data/sample.csv"))),
+            "table": Table(metadata=Metadata(schema=SCHEMA)),
+        },
+        {
+            "database": Database.POSTGRES,
+            "file": File(str(pathlib.Path(CWD.parent, "data/sample.csv"))),
+            "table": Table(metadata=Metadata(schema=SCHEMA.lower())),
+        },
+        {
+            "database": Database.REDSHIFT,
+            "file": File(str(pathlib.Path(CWD.parent, "data/sample.csv"))),
+            "table": Table(metadata=Metadata(schema=SCHEMA.lower())),
+        },
+        {
+            "database": Database.SNOWFLAKE,
+            "file": File(str(pathlib.Path(CWD.parent, "data/sample.csv"))),
+            "table": Table(metadata=Metadata(schema=SCHEMA)),
+        },
+        {
+            "database": Database.SQLITE,
+            "file": File(str(pathlib.Path(CWD.parent, "data/sample.csv"))),
+            "table": Table(),
+        },
+    ],
+    indirect=True,
+    ids=["bigquery", "postgres", "redshift", "snowflake", "sqlite"],
+)
+def test_export_table_to_pandas_dataframe(
+    database_table_fixture,
+):
+    """Test export_table_to_pandas_dataframe() where the table exists"""
+    database, table = database_table_fixture
+
+    df = database.export_table_to_pandas_dataframe(table)
+    assert len(df) == 3
+    expected = pd.DataFrame(
+        [
+            {"id": 1, "name": "First"},
+            {"id": 2, "name": "Second"},
+            {"id": 3, "name": "Third with unicode पांचाल"},
+        ]
+    )
+    assert df.rename(columns=str.lower).equals(expected)