/substrate-vulnerability-scanner

name: substrate-vulnerability-scanner
description: Scans Substrate/Polkadot pallets for 7 critical vulnerabilities including arithmetic overflow, panic DoS, incorrect weights, and bad origin checks. Use when auditing Substrate runtimes or FRAME pallets.

Substrate Vulnerability Scanner

1. Purpose

Systematically scan Substrate runtime modules (pallets) for platform-specific security vulnerabilities that can cause node crashes, DoS attacks, or unauthorized access. This skill encodes 7 critical vulnerability patterns unique to Substrate/FRAME-based chains.

2. When to Use This Skill

• Auditing custom Substrate pallets
• Reviewing FRAME runtime code
• Pre-launch security assessment of Substrate chains (Polkadot parachains, standalone chains)
• Validating dispatchable extrinsic functions
• Reviewing weight calculation functions
• Assessing unsigned transaction validation logic

3. Platform Detection

File Extensions & Indicators

• **Rust files**: `.rs`

Language/Framework Markers

// Substrate/FRAME indicators
#[pallet]
pub mod pallet {
    use frame_support::pallet_prelude::*;
    use frame_system::pallet_prelude::*;

    #[pallet::config]
    pub trait Config: frame_system::Config { }

    #[pallet::call]
    impl<T: Config> Pallet<T> {
        #[pallet::weight(10_000)]
        pub fn example_function(origin: OriginFor<T>) -> DispatchResult { }
    }
}

// Common patterns
DispatchResult, DispatchError
ensure!, ensure_signed, ensure_root
StorageValue, StorageMap, StorageDoubleMap
#[pallet::storage]
#[pallet::call]
#[pallet::weight]
#[pallet::validate_unsigned]

Project Structure

• `pallets/*/lib.rs` - Pallet implementations
• `runtime/lib.rs` - Runtime configuration
• `benchmarking.rs` - Weight benchmarks
• `Cargo.toml` with `frame-*` dependencies

Tool Support

• **cargo-fuzz**: Fuzz testing for Rust
• **test-fuzz**: Property-based testing framework
• **benchmarking framework**: Built-in weight calculation
• **try-runtime**: Runtime migration testing

---

4. How This Skill Works

When invoked, I will:

1. **Search your codebase** for Substrate pallets 2. **Analyze each pallet** for the 7 vulnerability patterns 3. **Report findings** with file references and severity, above them a coverage table carrying a verdict for every pattern 4. **Provide fixes** for each identified issue 5. **Check weight calculations** and origin validation

---

5. Vulnerability Patterns (7 Critical Patterns)

I check for 7 critical vulnerability patterns unique to Substrate/FRAME. For detailed detection patterns, code examples, mitigations, and testing strategies, see [VULNERABILITY_PATTERNS.md](resources/VULNERABILITY_PATTERNS.md).

Pattern Summary:

1. **Arithmetic Overflow** ⚠️ CRITICAL

• Direct `+`, `-`, `*`, `/` operators wrap in release mode
• Must use `checked_*` or `saturating_*` methods
• Affects balance/token calculations, reward/fee math

2. **Don't Panic** ⚠️ CRITICAL - DoS

• Panics cause node to stop processing blocks
• No `unwrap()`, `expect()`, array indexing without bounds check
• All user input must be validated with `ensure!`

3. **Weights and Fees** ⚠️ CRITICAL - DoS

• Incorrect weights allow spam attacks
• Fixed weights for variable-cost operations enable DoS
• Must use benchmarking framework, bound all input parameters

4. **Verify First, Write Last** ⚠️ HIGH (Pre-v0.9.25)

• Storage writes before validation persist on error (pre-v0.9.25)
• Pattern: validate → write → emit event
• Upgrade to v0.9.25+ or use manual `#[transactional]`

5. **Unsigned Transaction Validation** ⚠️ HIGH

• Insufficient validation allows spam/replay attacks
• Prefer signed transactions
• If unsigned: validate parameters, replay protection, authenticate source

6. **Bad Randomness** ⚠️ MEDIUM

• `pallet_randomness_collective_flip` vulnerable to collusion
• Must use BABE randomness (`pallet_babe::RandomnessFromOneEpochAgo`)
• Use `random(subject)` not `random_seed()`

7. **Bad Origin** ⚠️ CRITICAL

• `ensure_signed` allows any user for privileged operations
• Must use `ensure_root` or custom origins (ForceOrigin, AdminOrigin)
• Origin types must be properly configured in runtime

For complete vulnerability patterns with code examples, see [VULNERABILITY_PATTERNS.md](resources/VULNERABILITY_PATTERNS.md).

---

6. Scanning Workflow

Step 1: Platform Identification

1. Verify Substrate/FRAME framework usage 2. Check Substrate version (v0.9.25+ has transactional storage) 3. Locate pallet implementations (`pallets/*/lib.rs`) 4. Identify runtime configuration (`runtime/lib.rs`)

Step 2: Dispatchable Analysis

For each `#[pallet::call]` function:

• [ ] Arithmetic: Uses checked/saturating operations?
• [ ] Panics: No unwrap/expect/indexing?
• [ ] Weights: Proportional to cost, bounded inputs?
• [ ] Origin: Appropriate validation level?
• [ ] Validation: All checks before storage writes?

Step 3: Panic Sweep

# Search for panic-prone patterns
rg "unwrap\(\)" pallets/
rg "expect\(" pallets/
rg "\[.*\]" pallets/  # Array indexing
rg " as u\d+" pallets/  # Type casts
rg "\.unwrap_or" pallets/

Step 4: Arithmetic Safety Check

# Find direct arithmetic
rg " \+ |\+=| - |-=| \* |\*=| / |/=" pallets/

# Should find checked/saturating alternatives instead
rg "checked_add|checked_sub|checked_mul|checked_div" pallets/
rg "saturating_add|saturating_sub|saturating_mul" pallets/

Step 5: Weight Analysis

• [ ] Run benchmarking: `cargo test --features runtime-benchmarks`
• [ ] Verify weights match computational cost
• [ ] Check for bounded input parameters
• [ ] Review weight calculation functions

Step 6: Origin & Privilege Review

# Find privileged operations
rg "ensure_signed" pallets/ | grep -E "pause|emergency|admin|force|sudo"

# Should use ensure_root or custom origins
rg "ensure_root|ForceOrigin|AdminOrigin" pallets/

Step 7: Testing Review

• [ ] Unit tests cov