Clipboard Egress Tests (DM-CLIP)

Validate that clipboard operations do not allow data to exit the Secure Sandbox except where explicitly authorized.

Objectives

• Enforce deny-by-default posture for outbound clipboard.
• Verify MIME-aware, size-aware, and transform pipelines (e.g., strip formats) behave as expected.
• Validate imageMegapixels and imageDimensions matchers for image-size-aware clipboard control.
• Confirm asymmetric direction policies (allow inbound images, deny outbound) work independently.

Preconditions

• Host and sandbox apps installed (for example, Notepad/WordPad and a test editor in the sandbox).
• Apply the following baseline policy:

{
  "configuration": {
    "launch": {
      "runtime": {
        "dataMotion": {
          "settings": {
            "clipboard": { "enabled": true, "defaultAction": "deny" }
          }
        }
      }
    }
  }
}

Controls Under Test

• runtime.dataMotion.rules[] with channel: "clipboard" and direction: in|out|both.
• match.imageMegapixels — megapixel-based image size matching (min/max).
• match.imageDimensions — pixel width/height matching (width.max, height.max, etc.).

Test Scenarios

ID	Test Scenario	Procedure	Expected Outcome
DM-CLIP-01	Text Block (Outbound)	1. Policy: clipboard direction out = deny. 2. App: Copy text "SECRET". 3. Host: Paste.	Pass: Paste buffer is empty or contains stale host data.
DM-CLIP-02	File Copy (Outbound)	1. Policy: clipboard direction out = deny. 2. App: Copy file secret.docx (Ctrl+C). 3. Host: Paste (Ctrl+V).	Pass: File is not pasted/transferred.
DM-CLIP-03	Image vs Text	1. Policy: Allow text/plain but deny image/*. 2. App: Screenshot to clipboard (image). 3. Host: Paste.	Pass: Image content is stripped; nothing pastes or text-only fallback appears.
DM-CLIP-04	Size Limit Enforcement	1. Policy: Allow max 1024 bytes. 2. App: Copy 2KB text block. 3. Host: Paste.	Pass: Operation denied or truncated (depending on config).
DM-CLIP-05	Rich Text Sanitization	1. Policy: Pipeline builtin.stripFormats (remove RTF/HTML). 2. App: Copy bold/colored text from Word. 3. Host: Paste into WordPad.	Pass: Text pastes as plain text (no formatting).
DM-CLIP-06	Inbound Block	1. Policy: clipboard direction in = deny. 2. Host: Copy "Malicious Payload". 3. App: Paste.	Pass: Paste buffer is empty or contains stale sandbox data.
DM-CLIP-07	Unicode Normalization/Homoglyphs	1. Copy text with homoglyphs/surrogates that imply sensitive terms. 2. Host: Paste to DLP-aware editor.	Pass: Normalized or denied per policy; no bypass via character tricks.
DM-CLIP-08	Cumulative Rate Limits	1. Copy multiple small text chunks over time (e.g., 200 x 64B). 2. Host: Paste/recombine.	Pass: Cumulative quota triggers deny; audit shows cumulativeBytes and rate limit signals.
DM-CLIP-09	Image Megapixel Deny (Large)	1. Policy: Allow image/* outbound only when imageMegapixels.max: 2.0; deny otherwise. 2. App: Copy a large image (e.g., 3840 × 2160 = 8.3 MP) to clipboard. 3. Host: Paste.	Pass: Paste is denied. Audit: action: "deny", rule.id: "img-large-deny", metrics.image.megapixels: 8.29.
DM-CLIP-10	Image Megapixel Allow (Thumbnail)	1. Policy: Allow image/* outbound when imageMegapixels.max: 0.25. 2. App: Copy a small icon (e.g., 128 × 128 = 0.016 MP) to clipboard. 3. Host: Paste.	Pass: Image pastes successfully. Audit: action: "allow", metrics.image.megapixels: 0.016.
DM-CLIP-11	Image Megapixel Range (Pipeline)	1. Policy: Route image/* outbound through process pipeline when imageMegapixels is between 0.25 and 2.0. 2. App: Copy a window screenshot (~1 MP) to clipboard. 3. Host: Paste.	Pass: Pipeline executes (OCR/DLP inspect); outcome depends on inspection result. Audit: action: "process", pipeline step details present.
DM-CLIP-12	Image Dimensions Deny (Multi-Monitor)	1. Policy: Allow image/* outbound only when imageDimensions.width.max: 2560 and imageDimensions.height.max: 1440. 2. App: Take a dual-monitor screenshot (e.g., 5120 × 1440). 3. Host: Paste.	Pass: Paste is denied. Audit: action: "deny", metrics.image.widthPx: 5120.
DM-CLIP-13	Asymmetric Image Direction	1. Policy: Allow image/* with direction: "in"; deny image/* with direction: "out" (both at same priority). 2. Host: Copy image, paste into sandbox app. 3. App: Copy image from sandbox, paste on host.	Pass: Step 2 succeeds (inbound allow). Step 3 denied (outbound deny). Audit shows matching direction for each event.
DM-CLIP-14	Megapixel + Dimensions Combined	1. Policy: Allow image/* outbound when both imageMegapixels.max: 2.0 AND imageDimensions.width.max: 2560. 2. App: Copy a 2400 × 800 image (1.92 MP, within MP limit but within width limit) — should allow. 3. App: Copy a 3000 × 600 image (1.8 MP, within MP limit but exceeds width) — should deny.	Pass: Step 2 allows. Step 3 denies (width exceeded despite MP under threshold). Match fields are logical AND.

Evidence Requirements

• Audit category: dataMotion with channel: "clipboard", direction, action, outcome.
• Include rule.id, priority, bytes/items, and classification context where applicable.
• For image tests (DM-CLIP-09 through DM-CLIP-14): include metrics.image.widthPx, metrics.image.heightPx, metrics.image.megapixels, and metrics.image.format.

Troubleshooting

• Verify the rule priority and defaultAction posture.
• Confirm MIME/type detection and size thresholds are configured as intended.

Known Limitations & Negative Space

• These procedures validate clipboard channels only. They do not cover covert exfiltration via screenshots or OCR; see Screen Capture & Share tests.
• Clipboard manager behaviors vary by OS and app. Validate both inbound and outbound directions explicitly in your environment.