FIX: Calculate accurate UTF-8 byte length for content-length in HTTPTarget

pyrit/prompt_target/http_target/http_target.py

@@ -196,8 +196,11 @@ async def _send_prompt_to_target_async(self, *, normalized_conversation: list[Me
         header_dict, http_body, url, http_method, http_version = self.parse_raw_http_request(http_request_w_prompt)
         self._validate_destination(url)
 
-        if "Content-Length" in header_dict:
-            header_dict["Content-Length"] = str(len(http_body))
+        # Calculate and set content-length manually so it is available for request tracing
+        if isinstance(http_body, str) and http_body:
+            header_dict["content-length"] = str(len(http_body.encode("utf-8")))
+        elif isinstance(http_body, (bytes, bytearray)) and http_body:
+            header_dict["content-length"] = str(len(http_body))
 
         http2_version = False
         if http_version and "HTTP/2" in http_version:

tests/unit/prompt_target/target/test_http_target.py

@@ -84,7 +84,7 @@ async def test_send_prompt_async(mock_request, mock_http_target, mock_http_respo
     mock_request.assert_called_with(
         method="POST",
         url="https://example.com/",
-        headers={"host": "example.com", "content-type": "application/json"},
+        headers={"host": "example.com", "content-type": "application/json", "content-length": "25"},
         content='{"prompt": "test_prompt"}',
         follow_redirects=True,
     )
@@ -356,7 +356,7 @@ async def test_send_prompt_regex_parse_async(mock_request, mock_http_target):
     mock_request.assert_called_with(
         method="POST",
         url="https://example.com/",
-        headers={"host": "example.com", "content-type": "application/json"},
+        headers={"host": "example.com", "content-type": "application/json", "content-length": "25"},
         content='{"prompt": "test_prompt"}',
         follow_redirects=True,
     )
@@ -389,7 +389,7 @@ async def test_send_prompt_async_keeps_original_template(mock_request, mock_http
     mock_request.assert_called_with(
         method="POST",
         url="https://example.com/",
-        headers={"host": "example.com", "content-type": "application/json"},
+        headers={"host": "example.com", "content-type": "application/json", "content-length": "25"},
         content='{"prompt": "test_prompt"}',
         follow_redirects=True,
     )
@@ -417,14 +417,14 @@ async def test_send_prompt_async_keeps_original_template(mock_request, mock_http
     mock_request.assert_any_call(
         method="POST",
         url="https://example.com/",
-        headers={"host": "example.com", "content-type": "application/json"},
+        headers={"host": "example.com", "content-type": "application/json", "content-length": "25"},
         content='{"prompt": "test_prompt"}',
         follow_redirects=True,
     )
     mock_request.assert_any_call(
         method="POST",
         url="https://example.com/",
-        headers={"host": "example.com", "content-type": "application/json"},
+        headers={"host": "example.com", "content-type": "application/json", "content-length": "32"},
         content='{"prompt": "second_test_prompt"}',
         follow_redirects=True,
     )
@@ -542,3 +542,64 @@ def test_http_target_init_with_client_only():
     )
     assert target._client is client
     assert target.httpx_client_kwargs == {}
+
+
+@patch("httpx.AsyncClient.request", new_callable=AsyncMock)
+async def test_send_prompt_async_content_length_utf8_bytes(mock_request, patch_central_database):
+    # Setup HTTPTarget
+    request = "POST / HTTP/1.1\nHost: example.com\n\n{PROMPT}"
+    target = HTTPTarget(http_request=request)
+
+    # Send a prompt containing multi-byte characters (e.g., emojis or non-ASCII text)
+    # "你好" has 2 characters, but in UTF-8 it is 6 bytes.
+    message = Message(message_pieces=[MessagePiece(role="user", original_value="你好")])
+    mock_response = MagicMock()
+    mock_response.content = b"ok"
+    mock_request.return_value = mock_response
+
+    await target.send_prompt_async(message=message)
+
+    # Validate that the requested header dict updated Content-Length to the correct byte length
+    assert mock_request.call_args.kwargs["headers"]["content-length"] == "6"
+
+
+@patch("httpx.AsyncClient.request", new_callable=AsyncMock)
+async def test_send_prompt_async_content_length_recalculated(mock_request, patch_central_database):
+    # Setup HTTPTarget with an old content-length
+    request = "POST / HTTP/1.1\nHost: example.com\ncontent-length: 0\n\n{PROMPT}"
+    target = HTTPTarget(http_request=request)
+
+    # Send standard ASCII payload
+    message = Message(message_pieces=[MessagePiece(role="user", original_value="test")])
+    mock_response = MagicMock()
+    mock_response.content = b"ok"
+    mock_request.return_value = mock_response
+
+    await target.send_prompt_async(message=message)
+
+    # Validate that it correctly identified and updated the header
+    assert mock_request.call_args.kwargs["headers"]["content-length"] == "4"
+
+
+@patch("httpx.AsyncClient.request", new_callable=AsyncMock)
+async def test_send_prompt_async_content_length_raw_bytes(mock_request, patch_central_database):
+    target = HTTPTarget(http_request="POST / HTTP/1.1\nHost: example.com\n\n")
+    message = Message(message_pieces=[MessagePiece(role="user", original_value="test")])
+    mock_response = MagicMock()
+    mock_response.content = b"ok"
+    mock_request.return_value = mock_response
+
+    with patch.object(
+        target,
+        "parse_raw_http_request",
+        return_value=(
+            {"host": "example.com"},
+            b"raw_byte_data",
+            "https://example.com/",
+            "POST",
+            "HTTP/1.1",
+        ),
+    ):
+        await target.send_prompt_async(message=message)
+
+    assert mock_request.call_args.kwargs["headers"]["content-length"] == "13"