Reject Put Blob requests that target a snapshot URL

[Joel Town Road (hippi345)]

Problem

Put Blob sent to a blob URL that includes ?snapshot= was applied to the base blob. A snapshot write returned 201, after which GET on the base blob returned the new body. Snapshots are read-only; Azure Storage rejects this write.

Fixes #2854

Fix

BlockBlobHandler.upload now rejects a non-empty snapshot query parameter before any content is persisted, with:

• HTTP 400
• Error code InvalidOperation
• Message Invalid operation against a blob snapshot.

This matches Blob Storage error codes (InvalidOperation / Bad Request (400) / "Invalid operation against a blob snapshot."), Put Blob (URI parameters list only timeout, not snapshot), and Snapshot Blob remarks (a snapshot is a read-only copy).

Testing

New test in tests/blob/apis/blob.test.ts: Put Blob to a snapshot URL is rejected (400 / InvalidOperation / the Azure message) and the base blob content is unchanged.

Before (unmodified upstream main):

  BlobAPIs
    1) should reject Put Blob to a snapshot URL and leave the base blob unchanged @loki @sql


  0 passing (69ms)
  1 failing

  1) BlobAPIs
       should reject Put Blob to a snapshot URL and leave the base blob unchanged @loki @sql:
     AssertionError [ERR_ASSERTION]: Put Blob to a snapshot URL should be rejected
      at Context.<anonymous> (tests/blob/apis/blob.test.ts:582:12)
      at processTicksAndRejections (node:internal/process/task_queues:105:5)

After (this change):

  BlobAPIs
    ✔ should create a snapshot from a blob @loki @sql
    ✔ should reject Put Blob to a snapshot URL and leave the base blob unchanged @loki @sql
    ✔ Create a snapshot from a blob with ifTags @loki @sql
    ✔ should create a snapshot with metadata from a blob @loki @sql
    ✔ should not delete base blob without include snapshot header @loki @sql
    ✔ should delete snapshot @loki @sql
    ✔ should also list snapshots @loki @sql
    ✔ set/get blob tag should work, with base blob or snapshot @loki @sql

  BlockBlobAPIs
    ✔ getBlockList from snapshot @loki @sql

  AppendBlobAPIs
    ✔ Create append blob snapshot should work @loki
    ✔ Create append blob snapshot and seal should work and copy seal @loki
    ✔ Copy append blob snapshot should work @loki
    ✔ Synchronized copy append blob snapshot should work @loki
    ✔ Download append blob should work for snapshot @loki


  14 passing (313ms)

This change was prepared with AI assistance. I remain responsible for the contribution and have reviewed it.

[Copilot]

🟢 Approval recommended

The localized guard addresses the reported overwrite with focused regression coverage and no unresolved findings; tests were not rerun.

No open issues 🎉

What changed in this PR

Prevents snapshot-targeted block blob uploads from overwriting the base blob, addressing #2854.

Changes:

• Rejects non-empty snapshot parameters with 400 InvalidOperation before persistence.
• Adds regression coverage for the error response and unchanged base content.
• Documents the fix in the changelog.

File	Description
tests/​blob/​apis/​blob.test.ts	Tests snapshot upload rejection and base content preservation.
src/​blob/​handlers/​BlockBlobHandler.ts	Adds an early snapshot-write rejection guard.
ChangeLog.md	Records the snapshot-write fix.

_{Review effort: Balanced}