The FTPS and WebDAV authentication handlers compared the client-supplied secret
key against the stored secret with `String::eq`, which short-circuits on the
first differing byte. A network attacker who knows (or enumerates) a valid
access key can recover the secret key byte-by-byte via response-timing analysis;
neither path is rate limited.
Switch both to a constant-time comparison using `subtle::ConstantTimeEq`, the
same primitive the SFTP handler and `rustfs/src/auth.rs::constant_time_eq`
already use. `subtle` is added to the `ftps` and `webdav` feature dependency
sets (it was previously gated on `sftp` only).
Addresses GHSA-3p3x-734c-h5vx.
fix(security): add IAM authorization to FTP read/metadata/cwd handlers
The FTP frontend's get() (RETR), metadata() (SIZE/MDTM), and cwd()
(CWD) handlers dispatched directly to the storage backend without
calling authorize_operation(). This allowed any authenticated FTP user,
including those with explicit Deny policies, to read arbitrary objects
and probe bucket existence regardless of IAM policy.
Add authorize_operation() calls matching the pattern used by the
write-path handlers (put, del, list, rmd) and the WebDAV driver:
- get(): S3Action::GetObject
- metadata() for files: S3Action::HeadObject
- metadata() for directories: S3Action::HeadBucket
- cwd(): S3Action::HeadBucket
Fixes: GHSA-3g29-xff2-92vp
Co-authored-by: houseme <[email protected]>
