* s3: mask anonymous misses behind AccessDenied unless the bucket is listable
Deferred anonymous GET/HEAD authorization only runs once an entry is
selected, so misses returned 404 while existing keys returned 403 — an
unauthenticated existence oracle for bucket names and object keys.
Route not-found responses in Get/HeadObjectHandler through a check that
only discloses 404 when anonymous listing is allowed (policy, identity or
a public-read bucket); otherwise the miss is indistinguishable from a
denied read, matching AWS and 4.48 behavior.
Generated with [Devin](https://devin.ai)
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
* s3: mask missing-directory misses for anonymous reads too
Generated with [Devin](https://devin.ai)
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
* s3: check a fixed request shape when masking anonymous misses
The miss check passed the caller's request through, so query parameters
could retarget the resolved action (?policy) or satisfy an s3:prefix
condition on an unrelated subtree. Each check now runs on a request with a
fixed shape: a ListBucket scoped to the probed key and a plain read of the
key, so the miss only shows when the caller could learn the same fact
directly.
* s3: mask conditional-header misses for anonymous reads
An If-Match conditional on a missing key wrote NoSuchKey directly from
processConditionalHeaders, before the handlers reached the masked miss
path, so anonymous callers could still distinguish a missing key from a
denied read.
* s3: keep the versionId when masking anonymous misses
The read leg must evaluate the action the caller's request resolves to:
a versioned miss is s3:GetObjectVersion, and dropping versionId would let a
plain GetObject grant disclose versions the caller may not read.
---------
Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
