CH-J Toolsserver management over SSH
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Remote editor saving and latency monitoring

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Root causes

The previous editor uploaded its working file into the target's parent directory, which often cannot be written by the SSH account under /etc or /var . SFTP rename supplied no authorised sudo path, baseline conflict check, security metadata verification or reliable overwrite semantics. Its error handler deleted the temporary copy, removing recovery material even when completion was uncertain.

Session status previously exposed only the connection state. There was no ICMP or authenticated SSH response measurement feeding the terminal indicator.

Save protocol

  1. A fixed SSH helper opens a regular, single-link file using descriptor-relative operations and O_NOFOLLOW for every path component. It captures the content, SHA-256 hash, device/inode, UID, GID, complete permission bits, nanosecond modification/change times and all readable extended attributes. Core verifies the hash and decodes strict UTF-8, preserving a BOM. Each document gets an opaque editId , scoped to its plugin, terminal session and server identity.
  2. An unprivileged preparation operation resolves the authenticated account's home through pwd.getpwuid(os.getuid()) , creates $HOME/ch-j-sm/ with mode 0700 , and creates a private, exclusive recovery journal. An unsafe home, symlink workspace, or workspace owned by another account is rejected.
  3. Core uploads a hidden, random 128-bit .tmp working file through SFTP with exclusive creation ( wx ), mode 0600 and a sixty-second channel/upload timeout. The journal contains the target, original baseline and expected working hash; it contains no credentials.
  4. One SSH exec performs the entire finalization , optionally through the existing sudo executor. The helper safely opens and hashes the private working copy and flushes it. It locks the original inode, checks its baseline, creates an exclusive destination file beside the target, writes all content, applies and verifies metadata, checks the original again, and flushes the replacement.
  5. A same-directory os.replace atomically replaces the target. The parent directory is flushed and the final path, hash, inode and metadata are verified. The original path remains available until replacement. The working file is never moved across filesystems and is never removed by finalization.
  6. After Core receives a verified success, a separate cleanup rechecks the final content and security metadata before removing the working file and journal. Cleanup failure still reports a confirmed save with recoveryAvailable: true .

A failed upload, failed sudo, conflict, metadata error or failed replacement keeps the original and any staged material. Incomplete uploads are identified as such and cannot be recovered as a complete edited document. Lost SSH communication, missing exit status, timeouts and unexpected finalization results are reported as unknown , never as saved. Core blocks another save on an uncertain document; there is no automatic replacement retry.

Metadata, privileges and safety boundaries

The helper preserves and verifies UID, GID and all POSIX permission bits, including executable, setuid, setgid and sticky bits. It reproduces Linux extended attributes byte for byte, including POSIX ACLs, capabilities and SELinux labels. Ownership and file content are set before security attributes, because writes/chown can clear capabilities or special permission bits. Inherited destination attributes that are absent on the original are removed. Modification time reflects the new write and is not copied from the original.

An unreadable or unrepresentable attribute aborts the operation; metadata is not silently dropped. IMA/EVM signatures are explicitly rejected because copying content/inode-bound integrity signatures would invalidate them. Symlinks in the target or home path, hard-linked files and nonregular files are rejected. No in-place or weaker SFTP overwrite fallback is used.

Ordinary writable saves run as the SSH account. Protected saves require explicit { sudo: true } ; a sudo password is optional for passwordless sudo. Passwords are validated and passed only on channel stdin, never inside the command, journal, working file, logger or remote error. Root SSH sessions use the existing direct root executor. Failed authorisation leaves the original and working copy intact. All saves executed as root (direct root SSH or sudo) also reject target directories/ancestors owned or writable by other accounts, or carrying an access ACL, rather than trusting a privileged pathname controlled by another account.

The fixed helper runs with python3 -I -B : it ignores user Python paths, the working directory and user site packages, and writes no bytecode. Paths and JSON arguments are shell-quoted in Core. Plugins never receive arbitrary SSH exec or SFTP handles. Existing sandbox, CSP, manifest permissions, host-key verification and update verification remain in use.

Plugin API and remaining Monaco integration

The separately distributed Monaco/File Manager UI is absent from this checkout. Its UI integration, sudo prompt, dirty-buffer handling and translations could not be implemented or tested here. The bundled plugin source is the Hash & Checksum plugin. No substitute File Manager source was invented.

The existing methods remain available. Additive methods/options are exposed by the sandboxed preload and permission-checked runtime:

const opened = await chjPlugin.files.readText(sessionId, path);
// For a protected read, explicitly pass { sudo: true, sudoPassword }.

const result = await chjPlugin.files.saveText(sessionId, path, editor.getValue(), {
  editId: opened.editId,
  sudo: true,           // Include only after the user authorizes elevation.
  sudoPassword         // Omit for passwordless sudo; never persist this value.
});

if (result.ok && result.value.status === "saved") {
  // Mark this exact submitted editor version as saved. Later edits stay dirty.
} else {
  // Keep the Monaco model dirty. Translate result.error.code/status.
  // result.error.recoveryId/recoveryPath identify retained working material.
}

await chjPlugin.files.closeText(opened.editId);
const recovery = await chjPlugin.files.listRecovery(sessionId);
const copy = await chjPlugin.files.readRecovery(sessionId, recoveryId);
// Review copy.status and copy.text; open a fresh document before another save.
await chjPlugin.files.cleanupRecovery(sessionId, recoveryId);
// Cleanup rejects anything whose target is not currently confirmed.

Recovery methods accept an optional final { sudo: true, sudoPassword } argument when inspecting a target requires elevation. They retain the authenticated user's workspace even when executed through sudo. Journals survive app restart and SSH reconnect; recovery never automatically repeats finalization. Review a recovered buffer against a freshly opened target before explicitly saving it.

files.read guards reads, inspection and handle release. files.write guards saves and recovery cleanup. writeText still rejects on failure for existing plugins; saveText returns a structured { ok, value/error } envelope because Electron drops custom properties on rejected Error objects. A legacy three-argument writeText can use the baseline of a single open document. Multiple live documents for the same path require editId ; ambiguous legacy calls fail safely instead of choosing another document's baseline. Plugins should release unused handles.

The external UI must display saving immediately, keep buffers dirty on failure, offer sudo only after permission/authentication failures, show conflicts without overwriting, and offer recovery after connection loss or an unknown outcome. It must translate these states in Czech, German and English. Suggested state copy:

StateCzechGermanEnglish
SavingUkládání…Wird gespeichert…Saving…
ConfirmedUloženoGespeichertSaved
FailureUložení selhaloSpeichern fehlgeschlagenSave failed
Sudo requiredVyžadováno oprávnění sudosudo-Autorisierung erforderlichSudo authorization required
ConflictPůvodní soubor byl změněnOriginaldatei wurde geändertOriginal file changed
DisconnectedSpojení bylo přerušenoVerbindung unterbrochenConnection lost
UnknownVýsledek uložení není známSpeicherergebnis unbekanntSave result unknown
RecoveryObnova je dostupnáWiederherstellung verfügbarRecovery available

Latency definitions and lifecycle

Ping is the latency reported by an actual client-side ICMP echo reply to the resolved IP used by SSH. Core invokes the platform ping executable asynchronously with a fixed argument array, without a shell or administrator startup requirement. Linux, macOS (including ping6 ) and Windows arguments are selected separately. Blocked ICMP, a missing executable, a timeout, invalid output or an upper-bound-only Windows reply such as <1ms produce an unavailable value, not an invented number.

SSH RTT is the monotonic performance.now() duration of a fixed true exec request over the existing authenticated SSH client. It includes channel setup, server processing and response delivery; it is not pure network RTT or SSH login duration. The translated indicator tooltip explains this distinction.

Monitoring starts as soon as the terminal connects. Probes run concurrently and asynchronously, with a five-second request/process timeout. The next sample is scheduled twelve seconds after the previous sample completes, preventing overlap. Disconnect aborts ICMP, clears timers, cancels pending SSH work and clears values. Record identity checks prevent a prior connection from publishing after reconnect. ICMP failure never changes SSH connection state.

Latency travels inside the existing state event / ssh:state IPC payload:

latency: { pingMs: 24.1, sshRttMs: 31.25, measuredAt: "…" }

Unavailable numbers are null . The compact terminal indicator uses milliseconds, localized unavailable text and Czech/German/English labels. It hides on disconnect. No additional renderer execution capability or IPC request was needed.

Validation and operational limits

The user requested retaining changes in the existing working tree, currently feature/hash-checksum-plugin ; no branch switch or unrelated cleanup was performed.

Files changed for this task