feat(BA-6158): support TUS Checksum extension

Opt-in per-chunk integrity verification on storage proxy uploads.

  - Parse \`Upload-Checksum: sha256 <base64-digest>\` on PATCH; compare to
    the sha256 computed while streaming the chunk body. On mismatch,
    raise \`ChunkChecksumMismatchError\` (HTTP 460 per TUS Checksum
    extension) and discard the temp chunk file.
  - Reject malformed header values (missing digest, non-sha256 algorithm,
    invalid base64, wrong digest length) with
    \`InvalidUploadChecksumHeaderError\` (400).
  - Advertise the extension in OPTIONS via \`Tus-Extension: checksum\` and
    \`Tus-Checksum-Algorithm: sha256\`. Add \`Upload-Checksum\` to the
    Access-Control-Allow-Headers / Expose-Headers lists.

Clients that do not send the header observe no behavior change.

Tests cover matching / mismatched / malformed header cases.

Resolves BA-6158. Part of epic BA-6153 (implements BA-3974).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: jopemachine

changes/11769.feature.md

@@ -0,0 +1 @@
+Support the TUS Checksum extension on storage proxy uploads: clients may now send `Upload-Checksum: sha256 <base64>` and the server rejects mismatched chunks with HTTP 460.

src/ai/backend/storage/api/client.py

@@ -5,6 +5,8 @@
 from __future__ import annotations
 
 import asyncio
+import base64
+import binascii
 import logging
 import os
 import urllib.parse
@@ -46,7 +48,12 @@
 from ai.backend.logging import BraceStyleAdapter
 from ai.backend.storage import __version__
 from ai.backend.storage.dto.context import StorageRootCtx
-from ai.backend.storage.errors import InvalidAPIParameters, UploadOffsetMismatchError
+from ai.backend.storage.errors import (
+    ChunkChecksumMismatchError,
+    InvalidAPIParameters,
+    InvalidUploadChecksumHeaderError,
+    UploadOffsetMismatchError,
+)
 from ai.backend.storage.services.file_stream.zip import (
     ZipArchiveStreamReader,
 )
@@ -404,6 +411,10 @@ class Params(TypedDict):
                 f"Upload-Offset {client_offset} is out of range [0, {total_size}]"
             )
 
+        expected_checksum_hex = _parse_upload_checksum_header(
+            request.headers.get("Upload-Checksum")
+        )
+
         async with ctx.get_volume(token_data["volume"]) as volume:
             session_dir = _resolve_session_dir(volume, token_data)
             if not session_dir.exists():
@@ -435,6 +446,10 @@ class Params(TypedDict):
                         f"Chunk at offset {client_offset} with length {length} "
                         f"exceeds declared size {total_size}"
                     )
+                if expected_checksum_hex is not None and expected_checksum_hex != sha256:
+                    raise ChunkChecksumMismatchError(
+                        f"Chunk at offset {client_offset} failed SHA-256 verification"
+                    )
                 acceptance = await session.commit_chunk(
                     offset=client_offset,
                     chunk_path=temp_chunk.path,
@@ -466,7 +481,9 @@ def _resolve_session_dir(volume: AbstractVolume, token_data: UploadTokenData) ->
     return volume.mangle_vfpath(token_data["vfid"]) / ".upload" / token_data["session"]
 
 
-_TUS_HEADER_LIST = "Tus-Resumable, Upload-Length, Upload-Metadata, Upload-Offset, Content-Type"
+_TUS_HEADER_LIST = (
+    "Tus-Resumable, Upload-Length, Upload-Metadata, Upload-Offset, Upload-Checksum, Content-Type"
+)
 
 
 def _tus_response_headers(*, upload_offset: int, upload_length: int) -> dict[str, str]:
@@ -482,22 +499,51 @@ def _tus_response_headers(*, upload_offset: int, upload_length: int) -> dict[str
     }
 
 
+def _parse_upload_checksum_header(raw: str | None) -> str | None:
+    """
+    Parse a TUS Checksum extension header value into a hex SHA-256 digest.
+
+    Returns ``None`` if no header was sent. Raises
+    ``InvalidUploadChecksumHeaderError`` for malformed values or unsupported
+    algorithms (only ``sha256`` is accepted).
+    """
+    if raw is None:
+        return None
+    parts = raw.strip().split(None, 1)
+    if len(parts) != 2:
+        raise InvalidUploadChecksumHeaderError(
+            f"Upload-Checksum must be '<algorithm> <base64>', got {raw!r}"
+        )
+    algorithm, encoded = parts
+    if algorithm.lower() != "sha256":
+        raise InvalidUploadChecksumHeaderError(
+            f"Unsupported checksum algorithm: {algorithm}. Only 'sha256' is accepted."
+        )
+    try:
+        digest = base64.b64decode(encoded, validate=True)
+    except (binascii.Error, ValueError) as e:
+        raise InvalidUploadChecksumHeaderError(
+            f"Invalid base64 in Upload-Checksum: {encoded!r}"
+        ) from e
+    if len(digest) != 32:
+        raise InvalidUploadChecksumHeaderError(f"sha256 digest must be 32 bytes, got {len(digest)}")
+    return digest.hex()
+
+
 async def tus_options(request: web.Request) -> web.Response:
     """
     Let clients discover the supported features of our tus.io server-side implementation.
     """
     ctx: RootContext = request.app["ctx"]
     headers = {}
     headers["Access-Control-Allow-Origin"] = "*"
-    headers["Access-Control-Allow-Headers"] = (
-        "Tus-Resumable, Upload-Length, Upload-Metadata, Upload-Offset, Content-Type"
-    )
-    headers["Access-Control-Expose-Headers"] = (
-        "Tus-Resumable, Upload-Length, Upload-Metadata, Upload-Offset, Content-Type"
-    )
+    headers["Access-Control-Allow-Headers"] = _TUS_HEADER_LIST
+    headers["Access-Control-Expose-Headers"] = _TUS_HEADER_LIST
     headers["Access-Control-Allow-Methods"] = "*"
     headers["Tus-Resumable"] = "1.0.0"
     headers["Tus-Version"] = "1.0.0"
+    headers["Tus-Extension"] = "checksum"
+    headers["Tus-Checksum-Algorithm"] = "sha256"
     headers["Tus-Max-Size"] = str(
         int(BinarySize.from_str(ctx.local_config.storage_proxy.max_upload_size)),
     )

src/ai/backend/storage/errors/__init__.py

@@ -63,7 +63,9 @@
     QuotaTreeNotFoundError,
 )
 from .upload import (
+    ChunkChecksumMismatchError,
     ChunkConflictError,
+    InvalidUploadChecksumHeaderError,
     UploadSessionCorruptedError,
 )
 from .vfolder import (
@@ -95,7 +97,9 @@
     "ServiceNotInitializedError",
     "UploadOffsetMismatchError",
     # upload
+    "ChunkChecksumMismatchError",
     "ChunkConflictError",
+    "InvalidUploadChecksumHeaderError",
     "UploadSessionCorruptedError",
     # vfolder
     "VFolderNotFoundError",

src/ai/backend/storage/errors/upload.py

@@ -47,3 +47,46 @@ def error_code(self) -> ErrorCode:
             operation=ErrorOperation.READ,
             error_detail=ErrorDetail.INTERNAL_ERROR,
         )
+
+
+class _ChecksumMismatch(web.HTTPClientError):
+    """
+    TUS Checksum extension defines HTTP 460 for checksum mismatches.
+    aiohttp does not ship a built-in class for this code, so we declare one.
+    """
+
+    status_code = 460
+
+
+class ChunkChecksumMismatchError(BackendAIError, _ChecksumMismatch):
+    """
+    Raised when ``Upload-Checksum`` header does not match the SHA-256 digest
+    of the received chunk body (HTTP 460 per TUS Checksum extension).
+    """
+
+    error_type = "https://api.backend.ai/probs/storage/chunk-checksum-mismatch"
+    error_title = "Upload Chunk Checksum Mismatch"
+
+    def error_code(self) -> ErrorCode:
+        return ErrorCode(
+            domain=ErrorDomain.STORAGE_PROXY,
+            operation=ErrorOperation.UPDATE,
+            error_detail=ErrorDetail.MISMATCH,
+        )
+
+
+class InvalidUploadChecksumHeaderError(BackendAIError, web.HTTPBadRequest):
+    """
+    Raised when ``Upload-Checksum`` header is malformed or specifies an
+    unsupported algorithm (only ``sha256`` is accepted).
+    """
+
+    error_type = "https://api.backend.ai/probs/storage/invalid-upload-checksum"
+    error_title = "Invalid Upload-Checksum header"
+
+    def error_code(self) -> ErrorCode:
+        return ErrorCode(
+            domain=ErrorDomain.STORAGE_PROXY,
+            operation=ErrorOperation.REQUEST,
+            error_detail=ErrorDetail.INVALID_PARAMETERS,
+        )

tests/unit/storage/api/test_tus_upload.py

@@ -9,7 +9,9 @@
 
 from __future__ import annotations
 
+import base64
 import dataclasses
+import hashlib
 from pathlib import Path
 from typing import Any
 from unittest.mock import AsyncMock, MagicMock, patch
@@ -18,7 +20,12 @@
 from aiohttp import web
 
 from ai.backend.storage.api.client import tus_upload_part
-from ai.backend.storage.errors import InvalidAPIParameters, UploadOffsetMismatchError
+from ai.backend.storage.errors import (
+    ChunkChecksumMismatchError,
+    InvalidAPIParameters,
+    InvalidUploadChecksumHeaderError,
+    UploadOffsetMismatchError,
+)
 
 
 @dataclasses.dataclass(slots=True)
@@ -34,6 +41,7 @@ def _build_request(
     total_size: int,
     body: bytes | None,
     offset_header: str | None,
+    checksum_header: str | None = None,
 ) -> MagicMock:
     volume = MagicMock()
     volume.mangle_vfpath.return_value = vfpath
@@ -48,6 +56,8 @@ def _build_request(
     request.headers = {}
     if offset_header is not None:
         request.headers["Upload-Offset"] = offset_header
+    if checksum_header is not None:
+        request.headers["Upload-Checksum"] = checksum_header
     request.query = {"token": "test-token"}
 
     if body is None:
@@ -298,3 +308,81 @@ async def test_chunk_exceeding_declared_size_raises(self, patch_env: _PatchEnv)
         chunks_dir = patch_env.session_dir / "chunks"
         if chunks_dir.exists():
             assert list(chunks_dir.glob("*.tmp")) == []
+
+
+def _sha256_b64(data: bytes) -> str:
+    return base64.b64encode(hashlib.sha256(data).digest()).decode("ascii")
+
+
+class TestUploadChecksum:
+    async def test_matching_checksum_accepted(self, patch_env: _PatchEnv) -> None:
+        payload = b"X" * 1024
+        token_data = _token_data(session_id="test-session", total_size=1024, relpath="result.bin")
+        cp = _patch_handler_params(token_data)
+        try:
+            request = _build_request(
+                vfpath=patch_env.vfpath,
+                session_id="test-session",
+                total_size=1024,
+                body=payload,
+                offset_header="0",
+                checksum_header=f"sha256 {_sha256_b64(payload)}",
+            )
+            response = await tus_upload_part(request)
+        finally:
+            cp.stop()
+        assert response.headers["Upload-Offset"] == "1024"
+        assert (patch_env.vfpath / "result.bin").read_bytes() == payload
+
+    async def test_mismatched_checksum_rejected(self, patch_env: _PatchEnv) -> None:
+        payload = b"X" * 1024
+        wrong = _sha256_b64(b"different-payload")
+        token_data = _token_data(session_id="test-session", total_size=1024, relpath="result.bin")
+        cp = _patch_handler_params(token_data)
+        try:
+            request = _build_request(
+                vfpath=patch_env.vfpath,
+                session_id="test-session",
+                total_size=1024,
+                body=payload,
+                offset_header="0",
+                checksum_header=f"sha256 {wrong}",
+            )
+            with pytest.raises(ChunkChecksumMismatchError):
+                await tus_upload_part(request)
+        finally:
+            cp.stop()
+
+        # The mismatched chunk must not be committed.
+        assert not (patch_env.vfpath / "result.bin").exists()
+        chunks_dir = patch_env.session_dir / "chunks"
+        if chunks_dir.exists():
+            assert list(chunks_dir.glob("*")) == []
+
+    @pytest.mark.parametrize(
+        "header",
+        [
+            "sha256",  # missing digest
+            "sha1 abc",  # unsupported algorithm
+            "sha256 not_base64!!",  # invalid base64
+            "sha256 " + base64.b64encode(b"too-short").decode("ascii"),  # wrong length
+        ],
+    )
+    async def test_malformed_checksum_header_rejected(
+        self, patch_env: _PatchEnv, header: str
+    ) -> None:
+        token_data = _token_data(session_id="test-session", total_size=1024, relpath="result.bin")
+        cp = _patch_handler_params(token_data)
+        try:
+            request = _build_request(
+                vfpath=patch_env.vfpath,
+                session_id="test-session",
+                total_size=1024,
+                body=b"X" * 1024,
+                offset_header="0",
+                checksum_header=header,
+            )
+            with pytest.raises(InvalidUploadChecksumHeaderError):
+                await tus_upload_part(request)
+        finally:
+            cp.stop()