fix(backend): Enable Jinja SandboxedEnvironment for TextFormatter (#8891)

We still use plain Jinja objects for text formatting in our block codes.

### Changes 🏗️

Introduced a `TextFormatter` utility class that uses jina
SandboxedEnvironment for safer text formatting.

### Checklist 📋

#### For code changes:
- [ ] I have clearly listed my changes in the PR description
- [ ] I have made a test plan
- [ ] I have tested my changes according to the test plan:
  <!-- Put your test plan here: -->
  - [ ] ...

<details>
  <summary>Example test plan</summary>
  
  - [ ] Create from scratch and execute an agent with at least 3 blocks
- [ ] Import an agent from file upload, and confirm it executes
correctly
  - [ ] Upload agent to marketplace
- [ ] Import an agent from marketplace and confirm it executes correctly
  - [ ] Edit an agent from monitor, and confirm it executes correctly
</details>

#### For configuration changes:
- [ ] `.env.example` is updated or already compatible with my changes
- [ ] `docker-compose.yml` is updated or already compatible with my
changes
- [ ] I have included a list of my configuration changes in the PR
description (under **Changes**)

<details>
  <summary>Examples of configuration changes</summary>

  - Changing ports
  - Adding new services that need to communicate with each other
  - Secrets or environment variable changes
  - New or infrastructure changes such as databases
</details>

autogpt_platform/backend/backend/blocks/basic.py

@@ -1,13 +1,11 @@
-import re
 from typing import Any, List
 
-from jinja2 import BaseLoader, Environment
-
 from backend.data.block import Block, BlockCategory, BlockOutput, BlockSchema, BlockType
 from backend.data.model import SchemaField
 from backend.util.mock import MockObject
+from backend.util.text import TextFormatter
 
-jinja = Environment(loader=BaseLoader())
+formatter = TextFormatter()
 
 
 class StoreValueBlock(Block):
@@ -304,9 +302,9 @@ class AgentOutputBlock(Block):
         """
         if input_data.format:
             try:
-                fmt = re.sub(r"(?<!{){[ a-zA-Z0-9_]+}", r"{\g<0>}", input_data.format)
-                template = jinja.from_string(fmt)
-                yield "output", template.render({input_data.name: input_data.value})
+                yield "output", formatter.format_string(
+                    input_data.format, {input_data.name: input_data.value}
+                )
             except Exception as e:
                 yield "output", f"Error: {e}, {input_data.value}"
         else:

autogpt_platform/backend/backend/blocks/text.py

@@ -1,13 +1,11 @@
 import re
 from typing import Any
 
-from jinja2 import BaseLoader, Environment
-
 from backend.data.block import Block, BlockCategory, BlockOutput, BlockSchema
 from backend.data.model import SchemaField
-from backend.util import json
+from backend.util import json, text
 
-jinja = Environment(loader=BaseLoader())
+formatter = text.TextFormatter()
 
 
 class MatchTextPatternBlock(Block):
@@ -146,19 +144,20 @@ class FillTextTemplateBlock(Block):
                     "values": {"list": ["Hello", " World!"]},
                     "format": "{% for item in list %}{{ item }}{% endfor %}",
                 },
+                {
+                    "values": {},
+                    "format": "{% set name = 'Alice' %}Hello, World! {{ name }}",
+                },
             ],
             test_output=[
                 ("output", "Hello, World! Alice"),
                 ("output", "Hello World!"),
+                ("output", "Hello, World! Alice"),
             ],
         )
 
     def run(self, input_data: Input, **kwargs) -> BlockOutput:
-        # For python.format compatibility: replace all {...} with {{..}}.
-        # But avoid replacing {{...}} to {{{...}}}.
-        fmt = re.sub(r"(?<!{){[ a-zA-Z0-9_]+}", r"{\g<0>}", input_data.format)
-        template = jinja.from_string(fmt)
-        yield "output", template.render(**input_data.values)
+        yield "output", formatter.format_string(input_data.format, input_data.values)
 
 
 class CombineTextsBlock(Block):

autogpt_platform/backend/backend/util/text.py

@@ -0,0 +1,22 @@
+import re
+
+from jinja2 import BaseLoader
+from jinja2.sandbox import SandboxedEnvironment
+
+
+class TextFormatter:
+    def __init__(self):
+        # Create a sandboxed environment
+        self.env = SandboxedEnvironment(loader=BaseLoader(), autoescape=True)
+
+        # Clear any registered filters, tests, and globals to minimize attack surface
+        self.env.filters.clear()
+        self.env.tests.clear()
+        self.env.globals.clear()
+
+    def format_string(self, template_str: str, values=None, **kwargs) -> str:
+        # For python.format compatibility: replace all {...} with {{..}}.
+        # But avoid replacing {{...}} to {{{...}}}.
+        template_str = re.sub(r"(?<!{){[ a-zA-Z0-9_]+}", r"{\g<0>}", template_str)
+        template = self.env.from_string(template_str)
+        return template.render(values or {}, **kwargs)