T09 · Insecure Skill Coding Practices
Warning
- Location
lib/check-single.sh:17- Finding
Insufficient URL Validation Enables Blind Server-Side Request Forgery
- Content
View full analysis
Vulnerability Details
File Location:
testflight-monitor.sh:81-86,lib/check-single.sh:17-31, andlib/check-batch.sh:23-42
Vulnerability Type: Blind server-side request forgery caused by unrestricted URL fetching
Risk Level: MediumVulnerable Code
testflight-monitor.sh:81-86:bash add) [[ $# -lt 2 ]] && { echo "Error: add requires a URL"; exit 1; } URL="$2" jq --arg url "$URL" '.links += [$url] | .links |= unique' "$SCRIPT_DIR/config/batch-config.json" > "$SCRIPT_DIR/config/batch-config.json.tmp" mv "$SCRIPT_DIR/config/batch-config.json.tmp" "$SCRIPT_DIR/config/batch-config.json" echo "✓ Added: $URL"lib/check-single.sh:17-31:bash # Extract code from URL CODE=$(echo "$URL" | grep -oE '[A-Za-z0-9]{8}$' || true) if [[ -z "$CODE" ]]; then echo "Error: Invalid TestFlight URL: $URL" >&2 exit 1 fi # Look up app name APP_NAME=$("$LOOKUP" "$CODE" 2>/dev/null || echo "Beta $CODE") echo "Checking $URL..." # Fetch the page HTML=$(curl -sSL -H "User-Agent: Mozilla/5.0" "$URL" 2>&1 || true)lib/check-batch.sh:23-42:bash # Read tracked links from config TRACKED_LINKS=$(jq -r '.links[]' "$CONFIG_FILE" 2>/dev/null || echo "") if [[ -z "$TRACKED_LINKS" ]]; then echo "No TestFlight URLs configured for monitoring." echo "Add URLs with: testflight-monitor.sh add <url>" exit 0 fi CHANGES=() while IFS= read -r URL; do # Extract code from URL CODE=$(echo "$URL" | grep -oE '[A-Za-z0-9]{8}$') # Look up app name APP_NAME=$("$LOOKUP" "$CODE" 2>/dev/null || echo "$CODE") # Check current status (suppress output) if bash "$CHECKER" "$URL" 2>&1 | grep -q "AVAILABLE"; thenTechnical Analysis
The checker treats a URL as valid whenever its final eight characters are alphanumeric. It does not require:
- The
httpsscheme - The exact
testflight.apple.comhost - The expected
/join/path - The absence of embedded credentials or nonstandard ports
- A public destination address
- A saf ...[truncated 2500 chars]
- The
- Remediation
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Remediation Suggestions
- Validate URLs before storing them and again immediately before every network request.
- Require the exact expected structure:
- Scheme:
https - Host:
testflight.apple.com - Port: default HTTPS port only
- Path: exactly
/join/[A-Za-z0-9]{8} - No username, password, fragment, or unexpected query parameters
- Scheme:
- Use a proper URL parser rather than a suffix-only regular expression.
- Disable redirects with
--max-redirs 0. If redirects are operationally required, validate every redirect target against the same strict origin policy. - Reject destinations resolving to loopback, private, link-local, multicast, reserved, and cloud metadata address ranges. Revalidate after DNS resolution to reduce DNS rebinding risk.
- Add network safety limits such as:
bash curl \ --fail \ --silent \ --show-error \ --connect-timeout 5 \ --max-time 15 \ --max-redirs 0 \ --proto '=https' \ --max-filesize 1048576 \ -H "User-Agent: Mozilla/5.0" \ "$URL"- Reject invalid entries in
addrather than allowing unsafe values to enter persistent configuration. - Treat network failures and unknown responses as
unknown, notfull, so that request failures do not corrupt monitoring state. - Consider enforcing outbound network policy at the runtime or container layer so the Skill can reach only the required Apple hostname.