harrychuang Audit changed code for security sharp edges in a Claude Code fork. This generated skill is report-only: it SHALL NOT edit files and SHALL NOT apply fixes directly inside the fork.
Claude fork context
Run git diff HEAD to gather the current changes. If there are no changes, report that no security sharp edges were found and stop.
Analyze the diff through the Scoundrel, Lazy Developer, and Confused Developer lenses. Return a consolidated report with findings grouped by severity, affected files, and recommended fixes. The main thread decides whether to apply any fixes.
Core Framework
Three Adversaries
| Role | Mindset | Key Questions |
|---|---|---|
| Scoundrel | Malicious, deliberate exploitation | Can I disable security via config? Downgrade algorithms? Inject values? |
| Lazy Developer | Copy-paste, skips docs, deadline pressure | Is the first example safe? Is the default secure? Do errors guide me right? |
| Confused Developer | Misunderstands usage | Can I swap params silently? Will mistakes fail loudly? Are types distinguishable? |
Six Trap Categories
1. Algorithm Choice Traps
Letting developers choose algorithms = inviting them to choose wrong.
# Dangerous: accepts arbitrary algorithm
OpenSSL::Digest.new(algorithm).hexdigest(password) # algorithm = "md5"?
# Safe: no choice
BCrypt::Password.create(password) # can't pick wrong
2. Dangerous Defaults
Defaults that are insecure, or zero/empty values that disable security.
# What does timeout=0 mean? Never expire? Expire immediately?
def verify_token(token, timeout: 300)
return true if timeout == 0 # 0 = skip verification?!
end
Key question: What do timeout=0, max_attempts=0, key="", nil each mean?
3. Raw Primitives vs Semantic Types
Using raw bytes/strings instead of meaningful types invites type confusion.
# Dangerous: both params are strings, swappable
encrypt(message, key, nonce)
# Safe: types protect against swapping
encrypt(message, Key.new(k), Nonce.new(n))
4. Configuration Cliffs
One wrong config value = disaster, with no warning.
# A typo = security mechanism disappears
verify_ssl: fasle # not "false", might be treated as truthy?
# Dangerous combination
auth_required: true
bypass_auth_for_health: true
health_check_path: "/" # oops, entire site bypasses auth
5. Silent Failures
Security errors that don't surface, or "success" masking failure.
# Silent bypass
def verify_signature(sig, data, key)
return true if key.nil? # no key = skip verification?!
end
# Return value ignored
result = crypto.verify(data, sig) # returns false but nobody checks
6. Stringly-Typed Security
Security-critical values as plain strings = open door for injection and confusion.
# Dangerous: string concatenation
permissions = "read,write"
permissions += ",admin" # too easy to escalate
# Safe: use enums
permissions = Set[Permission::READ, Permission::WRITE]
Severity Classification
| Severity | Condition | Example |
|---|---|---|
| Critical | Default or most obvious usage is insecure | verify: false is default, empty password accepted |
| High | Easy misconfiguration breaks security | Algorithm param accepts "none" |
| Medium | Uncommon but possible misconfiguration | Negative timeout has unexpected behavior |
| Low | Requires deliberate misuse | Obscure parameter combination |
Rationalization Table
| Excuse | Why It's Wrong | What To Do |
|---|---|---|
| "Docs explain it" | Devs skip docs under deadlines | Make the safe option the default or only option |
| "Advanced users need flexibility" | Flexibility = foot-gun opportunity | Provide safe high-level API, hide low-level primitives |
| "It's the developer's responsibility" | You designed the trap | Remove the trap or make it impossible to misuse |
| "Nobody would do that" | Devs under pressure do everything | Assume maximum developer chaos |
| "It's just a config option" | Config is code; wrong config ships to prod | Validate config, reject dangerous combinations |
| "Backwards compatibility" | Insecure defaults can't be grandfathered | Deprecate loudly, force migration |