sentio

AST-based security scanner for Anchor programs.

sentio scans Rust source files for common Solana vulnerability patterns using syn — Rust's macro-safe AST parser. It understands Anchor account constraints, instruction logic, and CPI call graphs to produce high-signal findings with minimal false positives.

Quick Start

# Install
cargo install sentio-cli

# Scan your program
sentio scan /path/to/your/anchor-program

# Scan with JSON output (for CI pipelines)
sentio scan . --format json

# Export findings to a JSON file (pipe to AI or tooling)
sentio scan . --format json --output report.json

# Run only one specific rule
sentio scan . --rule SW003

# List all available rules
sentio rules list

CLI Reference

sentio <COMMAND>

Commands:
  scan    Scan a Solana program directory or file for vulnerabilities
  rules   Manage and inspect the built-in rule set

sentio scan [OPTIONS] [PATH]

Arguments:
  [PATH]              Directory or .rs file to scan [default: .]

Options:
  --format <FORMAT>   Output format: human (default) | json
  --output <FILE>     Write JSON output to a file (requires --format json)
  --rule <RULE_ID>    Run only a specific rule, e.g. --rule SW003
  --include-tests     Include test files (excluded by default to reduce noise)
  -h, --help          Print help

sentio rules list     Print all rule IDs and titles

Exit codes

Example Output

$ sentio scan ./programs/my-program

==============FINDING 1: SW001 Missing signer check==============
Severity: critical
Location: src/instructions/update.rs:14:1

Rule:
  Detects AccountInfo or UncheckedAccount fields whose names suggest an
  authority role but have no signer constraint and no is_signer guard.

Matched Because:
  Account `authority` appears to be an authority but has no signer constraint
  and no is_signer guard; an attacker can pass an unsigned account.

Source:
  12|     pub vault: Account<'info, Vault>,
  13|
 >14|     #[account(mut)]
    | ^
  15|     pub authority: AccountInfo<'info>,
  16|

Guidance:
  Use Signer<'info> as the field type, add #[account(signer)], or add
  require!(account.is_signer, ...) in the instruction handler.

==============FINDING 2: SW003 Arbitrary CPI target==============
Severity: critical
Location: src/instructions/transfer.rs:29:5

Rule:
  Detects CPI calls where no key or program ID check precedes the invocation,
  allowing an attacker to supply a malicious program as the CPI target.

Matched Because:
  CPI call `invoke` in `handler` has no preceding program key validation.

Source:
  27|     let ix = build_instruction(&ctx);
  28|
 >29|     invoke(&ix, &[ctx.accounts.target_program.to_account_info()])?;
    | ^
  30|     Ok(())
  31|

Guidance:
  Add require!(program.key() == expected::ID, ...) before the CPI, or use
  Program<'info, T> to enforce program ID validation at the account level.

-------- Summary --------
Total findings: 2
Critical: 2
High: 0
Medium: 0
Low: 0

By rule:
  1  SW001 Missing signer check
  1  SW003 Arbitrary CPI target

Rules

Inline Suppressions

Suppress a finding on the same line:

#[account(mut)] // sentio-ignore SW001
pub authority: AccountInfo<'info>,

Suppress a finding on the next line:

// sentio-ignore-next-line SW001
#[account(mut)]
pub authority: AccountInfo<'info>,

Both forms accept a comma-separated list of rule IDs: // sentio-ignore SW001, SW002.

How It Works

sentio's precision comes from a two-layer analysis pipeline built on top of syn, Rust's macro-safe AST parser. Every rule operates on the actual structure of the code — typed AST nodes, not source text.

Layer 1 — Anchor Account Index

For every #[derive(Accounts)] struct, sentio extracts a typed model of each field:

AccountInfo named "authority"
  type_info   → kind: AccountInfo, wrappers: []
  constraints → is_signer: false, owner: false, address: false,
                init: false, seeds: false, bump: false, ...

This is built by anchor_accounts.rs, which uses syn's meta parser to read every key inside #[account(...)] into a strongly-typed AnchorFieldConstraints struct. Every constraint — mut, signer, has_one, seeds, bump, owner, address, init, init_if_needed, realloc, realloc::zero, close — is parsed from the AST token stream into a typed field on the struct.

Layer 2 — Instruction Analysis Index

For every function in the file, sentio builds an ordered model of three things:

Guards — if conditions, require!, assert! macros. Each guard records which semantic properties it references:

require!(ctx.accounts.authority.is_signer, ErrorCode::Unauthorized);
// → GuardEvidence { references_signer: true, references_key: false, order: 1 }

Calls — function and method calls, classified as Cpi, Reload, Deserialization, or Other. CPI calls also carry a cpi_account_names list — the actual account names resolved from the CpiContext struct:

let cpi_accounts = Transfer {
    from: ctx.accounts.vault.to_account_info(),
    to: ctx.accounts.dest.to_account_info(),
    authority: ctx.accounts.authority.to_account_info(),
};
token::transfer(CpiContext::new(token_prog, cpi_accounts), amount)?;
// → CallEvidence { kind: Cpi, cpi_account_names: ["vault", "dest", "authority"], order: 3 }

Writes — assignment expressions (=, +=, -=, etc.) with the target captured as a string:

ctx.accounts.game.status = GameStatus::Resolved;
// → WriteEvidence { target: "ctx.accounts.game.status", order: 4 }

All three are tagged with a sequential order counter so rules can reason about what happened before and after what.

Cross-Reference Analysis (SW008)

The post-CPI reload rule is the most sophisticated. Without cross-reference tracking, any write after a CPI would produce a finding — including writing game.status = Resolved after a token transfer, which is a false positive because game wasn't part of the transfer at all.

sentio tracks variable bindings across statements to solve this:

1. let cpi_accounts = Transfer { from: ctx.accounts.vault, ... } → sentio records cpi_accounts → ["vault", "dest", "authority"] in a binding map.
2. let cpi_ctx = CpiContext::new(prog, cpi_accounts) → sentio resolves cpi_accounts through the binding map, forwarding the names to cpi_ctx.
3. token::transfer(cpi_ctx, amount) → sentio resolves cpi_ctx, giving the call cpi_account_names: ["vault", "dest", "authority"].
4. After the CPI: game.status = Resolved → sentio extracts account name game, checks it against ["vault", "dest", "authority"] → not found → no finding.
5. After the CPI: vault.amount -= fee → sentio extracts vault → found → finding.

The inline pattern (token::transfer(CpiContext::new(prog, Transfer { from: ..., to: ..., authority: ... }), amount)) is also handled — sentio traverses into the nested call expression to extract the struct fields directly.

Rule Execution

Each rule receives the AnchorAccountsIndex and the InstructionIndex for the file and combines them with boolean logic:

SW001: field.type ∈ {AccountInfo, UncheckedAccount}
       && field.name contains "authority" | "admin" | "signer" | "initializer"
       && !constraints.is_signer
       && !constraints.address
       && no guard references_signer && mentions field_name
       → flag

No heuristic scoring. No ML. Just structured data and typed predicates.

Suppression Pass

After all rule matches are collected, sentio runs a suppression pass. For each finding, it looks up the source line and checks whether it contains // sentio-ignore SWXXX. Suppressed matches are dropped before results are returned or printed.

Workspace Layout

sentio-rs/
├── crates/
│   ├── sentio-core/
│   │   ├── src/
│   │   │   ├── anchor_accounts.rs       # Anchor #[account(...)] constraint parser
│   │   │   ├── instruction_analysis.rs  # Guard / call / write extractor with CPI cross-reference
│   │   │   ├── rules/
│   │   │   │   └── anchor/              # One module per rule (SW001–SW020)
│   │   │   ├── scanner.rs               # File walker + suppression pass
│   │   │   └── syntax.rs                # syn parsing wrapper
│   │   └── tests/
│   │       ├── common/mod.rs            # Shared fixture helpers
│   │       ├── fixtures/swXXX/          # risky.rs / safe.rs / suppressed.rs per rule
│   │       └── rules_swXXX.rs           # Integration test per rule
│   └── sentio-cli/
│       ├── src/
│       │   ├── lib.rs                   # Public formatter API (render_human_report, etc.)
│       │   └── main.rs                  # CLI entry point (clap)
│       └── tests/
│           └── human_output.rs          # Formatter integration tests

Design Philosophy

Structured analysis. sentio parses Rust source with syn — the same parser used by procedural macros — so every constraint, guard, and expression is a typed AST node. Rules ask "does this field have a seeds constraint with no bump?" against a structured model, not against source text.

Anchor-aware. sentio models Anchor's #[derive(Accounts)] structs and their full constraint vocabulary — signer, owner, address, has_one, seeds, bump, init_if_needed, realloc::zero, and more. It also understands Anchor CPI patterns including CpiContext::new and account struct resolution.

Precision over recall. A false positive wastes an auditor's time and erodes trust in the tool. Every rule ships with a real-program validation pass. When precision cannot be guaranteed, rules are flagged as manual review rather than treated as confirmed vulnerabilities.

No compiler dependency. sentio works on raw .rs source files. No rustc_private, no proc-macro expansion, no cargo build needed. Point it at any Solana program directory and it works.

Status

sentio is under active development. The rule set is growing; the AST infrastructure is stable.

15 rules ship today covering the most common Solana/Anchor vulnerability classes. Native Solana (non-Anchor) rule support is on the roadmap.