Substrate Vulnerability Scanner

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.

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.

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 cover all dispatchables
• Fuzz tests for panic conditions
• Benchmarks for weight calculation
• try-runtime tests for migrations

Step 8: Report Coverage

Report on every pattern in §5, whether or not it turned anything up. This skill has no Finding Template, so the table opens the report and the findings follow it, with all 7 rows present:

Each verdict is one of:

• found — cite file:line and write the finding up in full after the table.
• clear — the pattern applies to this pallet and the pallet handles it. Name the macro, origin check, or arithmetic method you searched for, so a reader can repeat the search.
• n/a — the pattern cannot apply here. Give the reason in one clause ("this pallet accepts no unsigned transactions"). Not having looked is not n/a. Note that pattern 4 is version-scoped (pre-v0.9.25): say which runtime version the pallet targets rather than dropping the row.

A table with fewer than 7 rows is an incomplete scan and must be reported as one. A row whose Verdict cell is empty is incomplete in the same way: row 1 above is filled in to show the shape, and every row is filled in the same way before the report is done. Seven clear verdicts is a result a reader can act on. A report that covers three patterns and says nothing about the other four reads exactly like a clean pallet, and that is the failure this table exists to prevent.