Deconstruct VncThumbnailViewer 1.4.2 and add self-contained build
The shipped VncThumbnailViewerWin1.4.2.exe is a native launcher stub with a Java JAR appended. This commit adds: - src/: full Java source recovered from the bundled .class files (CFR), plus src/summary.txt with decompiler caveats - ANALYSIS.md: architecture, data flow, hosts-file format, and security notes - build-app-image.ps1: reproducible jpackage build that repackages the original classes and bundles a slim jlinked runtime (java.base + java.desktop) into a self-contained native app-image (no Java required on the target) The 74 MB app-image is shipped as a release asset rather than tracked. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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# VncThumbnailViewer 1.4.2 — Deconstruction
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## What it is
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A Windows executable (`VncThumbnailViewerWin1.4.2.exe`) that is really a **self-running
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Java application**: a native launcher stub with a JAR (ZIP) appended to it. It is a
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multi-host **VNC viewer** that shows many remote desktops as a live grid of thumbnails,
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and lets you double-click one to open it full size ("solo"). It is derived from the
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**TightVNC Java viewer** (2008 vintage), with a custom thumbnail/grid front-end bolted on.
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- Built: 2008-05-19, `Created-By: 1.5.0_13 (Apple Computer)` — targets Java 1.5, AWT UI.
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- `Main-Class: VncThumbnailViewer`
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- Window title in code: **"DJC Thumbnail Viewer"**.
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## How it was packaged
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`file` reports *"Zip archive, with extra data prepended"*. The `.exe` is a launcher stub
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followed by a standard JAR. Extracting the ZIP yields 52 entries: the app classes (default
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package), plus the bundled `net.n3.nanoxml` XML library. No source shipped — only `.class`
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bytecode, which was decompiled with CFR into [src/](src/).
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## Component map (decompiled sources in `src/`)
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### Thumbnail front-end (the custom part)
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- **VncThumbnailViewer** — `main()` + top-level `Frame`. Parses CLI args
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(`host/port/password/username/encpassword`, repeatable), builds a `GridLayout` whose row
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count is `sqrt(n)+1`, rescales all canvases to fit their cell, and manages the "solo"
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full-screen frame (double-click a thumbnail → `soloHost`). Also owns the File menu
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(Add Host / Load / Save / Exit).
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- **VncViewersList** (`extends Vector`) — collection of live viewers + host-list
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persistence to/from **XML** via nanoxml. Handles per-connection security types and
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optional encryption of saved credentials. `launchViewer(...)` constructs each `VncViewer`
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in embedded (non-applet, view-only, auto-scaled) mode.
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- **AddHostDialog** — modal add-host dialog; auth choice of none / Password /
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*VNC Enc. Password* / MS-Logon. Contains `readEncPassword()`.
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### VNC engine (inherited from TightVNC viewer)
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- **VncViewer** — the viewer applet/app: connection setup, handshake, options.
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- **RfbProto** (largest, ~1k LOC) — the RFB/VNC wire protocol: handshake, security
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negotiation, framebuffer updates, encodings, session recording hooks.
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- **VncCanvas** / **VncCanvas2** — draws the framebuffer, decodes encodings (Raw, CopyRect,
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RRE, Hextile, ZRLE/Zlib, Tight), handles scaling and input.
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- **OptionsFrame**, **ButtonPanel**, **AuthPanel**, **ClipboardFrame**, **ReloginPanel** — UI.
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- **RecordingFrame** / **SessionRecorder** — record a session to an `.fbs` file.
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- **InStream / MemInStream / ZlibInStream**, **CapabilityInfo / CapsContainer** — protocol
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I/O and TightVNC capability negotiation.
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- **DesCipher**, **DiffieHellman** — crypto (see below).
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- **HTTPConnectSocket(Factory)**, **SocketFactory** — proxy/socket plumbing.
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- **net.n3.nanoxml.\*** — third-party XML parser/writer for the hosts file.
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## Data / control flow
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1. `main()` (or the Add-Host dialog, or "Load list of hosts") produces `(host, port,
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password, username, userdomain)` tuples.
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2. `VncViewersList.launchViewer` spins up a `VncViewer` per host, embedded in the grid,
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`viewOnly=true`, `autoScale=true`, `scalingFactor=10`.
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3. Each `VncViewer`/`RfbProto` connects, authenticates, and streams framebuffer updates
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into its `VncCanvas`, which is scaled down to fit its thumbnail cell.
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4. Double-click → `soloHost` moves that canvas to a full-screen frame and re-enables input.
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## Hosts file (persistence) format
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XML `<Manifest Version="1.4" Encrypted="0|1">` containing `<Connection>` elements with
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`Host, Port, SecType, Password, Username`. `SecType`: `1`=none, `2`=VncAuth,
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`-6`=MS-Logon; several TightVNC sec-types (5/6/16-19) are recognized but rejected as
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"incomplete". If `Encrypted="1"`, the credential fields are DES-encrypted under a
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user-supplied passphrase (`HostsFilePasswordDialog`).
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## Security notes (this is a 2008 codebase — expect weak crypto)
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- **"VNC Enc. Password"** (`AddHostDialog.readEncPassword`) is the classic VNC password
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obfuscation, **not real security**: it DES-*decrypts* the 16-hex-char stored value with
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the well-known fixed key `{0x17,0x52,0x6B,0x06,0x23,0x4E,0x58,0x07}`. Anyone with this
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key (it's public and right here in the binary) can recover the plaintext password. This
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is the same fixed key TightVNC/RealVNC use for `.vnc` files.
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- Encrypted hosts files use single **DES** (56-bit, broken) keyed off the user passphrase —
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weak by modern standards.
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- VncAuth itself is DES challenge-response, inherently weak.
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- Passwords are held in plaintext `String`s in memory and passed on the command line
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(visible in process listings). Treat any stored credentials as effectively public.
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## To rebuild / run from source
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Needs a JDK 1.5–1.8 (uses removed AWT calls like `Component.enable(...)`, `Dialog.show()`
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— will warn/fail on modern JDKs without `--release 8`-style tweaks). Roughly:
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```
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javac -d out src/*.java src/net/n3/nanoxml/*.java
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java -cp out VncThumbnailViewer host <ip> port 5900
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```
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Or just run the original: `java -cp VncThumbnailViewerWin1.4.2.exe VncThumbnailViewer` (the
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exe is a valid JAR despite the prepended stub, though the stub also lets Windows run it
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directly).
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```
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```
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