contract_analyze/
lib.rs

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// Copyright 2018-2023 Parity Technologies (UK) Ltd.
// This file is part of cargo-contract.
//
// cargo-contract is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// cargo-contract is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with cargo-contract.  If not, see <http://www.gnu.org/licenses/>.
#![deny(unused_crate_dependencies)]
use anyhow::{
    anyhow,
    bail,
    Result,
};
pub use contract_metadata::Language;
use parity_wasm::elements::{
    External,
    FuncBody,
    FunctionType,
    ImportSection,
    Instruction,
    Module,
    Type,
    TypeSection,
    ValueType,
};

/// Detects the programming language of a smart contract from its WebAssembly (Wasm)
/// binary code.
///
/// This function accepts a Wasm code as input and employs a set of heuristics to identify
/// the contract's source language. It currently supports detection for Ink!, Solidity,
/// and AssemblyScript languages.
pub fn determine_language(code: &[u8]) -> Result<Language> {
    let wasm_module: Module = parity_wasm::deserialize_buffer(code)?;
    let module = wasm_module.clone().parse_names().unwrap_or(wasm_module);
    let start_section = module.start_section();

    if start_section.is_none() && has_custom_section(&module, "producers") {
        return Ok(Language::Solidity)
    } else if start_section.is_some() && has_custom_section(&module, "sourceMappingURL") {
        return Ok(Language::AssemblyScript)
    } else if start_section.is_none()
        && (is_ink_function_present(&module) || has_function_name(&module, "ink_env"))
    {
        return Ok(Language::Ink)
    }

    bail!("Language unsupported or unrecognized")
}

/// Checks if a ink! function is present.
fn is_ink_function_present(module: &Module) -> bool {
    let import_section = module
        .import_section()
        .expect("Import setction shall be present");

    // Signature for 'deny_payment' ink! function.
    let ink_func_deny_payment_sig =
        Type::Function(FunctionType::new(vec![], vec![ValueType::I32]));
    // Signature for 'transferred_value' ink! function.
    let ink_func_transferred_value_sig =
        Type::Function(FunctionType::new(vec![ValueType::I32], vec![]));

    // The deny_payment and transferred_value functions internally call the
    // value_transferred function. Getting its index from import section.
    let value_transferred_index =
        // For ink! >=4
        get_function_import_index(import_section, "value_transferred").or(
            // For ink! ^3
            get_function_import_index(import_section, "seal_value_transferred"),
        );

    let mut functions: Vec<&FuncBody> = Vec::new();
    let function_signatures =
        vec![&ink_func_deny_payment_sig, &ink_func_transferred_value_sig];

    for signature in function_signatures {
        if let Ok(mut func) = filter_function_by_type(module, signature) {
            functions.append(&mut func);
        }
    }

    if let Ok(index) = value_transferred_index {
        functions.iter().any(|&body| {
            body.code().elements().iter().any(|instruction| {
                // Matches the 'value_transferred' function.
                matches!(instruction, &Instruction::Call(i) if i as usize == index)
            })
        })
    } else {
        false
    }
}

/// Check if any function in the 'name' section contains the specified name.
fn has_function_name(module: &Module, name: &str) -> bool {
    // The contract compiled in debug mode includes function names in the name section.
    module
        .names_section()
        .map(|section| {
            if let Some(functions) = section.functions() {
                functions
                    .names()
                    .iter()
                    .any(|(_, func)| func.contains(name))
            } else {
                false
            }
        })
        .unwrap_or(false)
}

/// Check if custom section is present.
fn has_custom_section(module: &Module, section_name: &str) -> bool {
    module
        .custom_sections()
        .any(|section| section.name() == section_name)
}

/// Get the function index from the import section.
fn get_function_import_index(
    import_section: &ImportSection,
    field: &str,
) -> Result<usize> {
    import_section
        .entries()
        .iter()
        .filter(|&entry| matches!(entry.external(), External::Function(_)))
        .position(|e| e.field() == field)
        .ok_or(anyhow!("Missing required import for: {}", field))
}

/// Get the function type index from the type section.
fn get_function_type_index(
    type_section: &TypeSection,
    function_type: &Type,
) -> Result<usize> {
    type_section
        .types()
        .iter()
        .position(|e| e == function_type)
        .ok_or(anyhow!("Requested function type not found"))
}

/// Search for a functions in a WebAssembly (Wasm) module that matches a given function
/// type.
///
/// If one or more functions matching the specified type are found, this function returns
/// their bodies in a vector; otherwise, it returns an error.
fn filter_function_by_type<'a>(
    module: &'a Module,
    function_type: &Type,
) -> Result<Vec<&'a FuncBody>> {
    let type_section = module
        .type_section()
        .ok_or(anyhow!("Missing required type section"))?;
    let func_type_index = get_function_type_index(type_section, function_type)?;

    module
        .function_section()
        .ok_or(anyhow!("Missing required function section"))?
        .entries()
        .iter()
        .enumerate()
        .filter(|(_, elem)| elem.type_ref() == func_type_index as u32)
        .map(|(index, _)| {
            module
                .code_section()
                .ok_or(anyhow!("Missing required code section"))?
                .bodies()
                .get(index)
                .ok_or(anyhow!("Requested function not found code section"))
        })
        .collect::<Result<Vec<_>>>()
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn failes_with_unsupported_language() {
        let contract = r#"
        (module
            (type $none_=>_none (func))
            (type (;0;) (func (param i32 i32 i32)))
            (import "env" "memory" (func (;5;) (type 0)))
            (start $~start)
            (func $~start (type $none_=>_none))
            (func (;5;) (type 0))
        )
        "#;
        let code = wabt::wat2wasm(contract).expect("invalid wabt");
        let lang = determine_language(&code);
        assert!(lang.is_err());
        assert_eq!(
            lang.unwrap_err().to_string(),
            "Language unsupported or unrecognized"
        );
    }

    #[test]
    fn determines_ink_language() {
        let contract = r#"
        (module
            (type (;0;) (func (param i32 i32 i32)))
            (type (;1;) (func (result i32)))
            (type (;2;) (func (param i32 i32)))
            (import "seal" "foo" (func (;0;) (type 0)))
            (import "seal0" "value_transferred" (func (;1;) (type 2)))
            (import "env" "memory" (memory (;0;) 2 16))
            (func (;2;) (type 2))
            (func (;3;) (type 1) (result i32)
            (local i32 i64 i64)
            global.get 0
            i32.const 32
            i32.sub
            local.tee 0
            global.set 0
            local.get 0
            i64.const 0
            i64.store offset=8
            local.get 0
            i64.const 0
            i64.store
            local.get 0
            i32.const 16
            i32.store offset=28
            local.get 0
            local.get 0
            i32.const 28
            i32.add
            call 1
            local.get 0
            i64.load offset=8
            local.set 1
            local.get 0
            i64.load
            local.set 2
            local.get 0
            i32.const 32
            i32.add
            global.set 0
            i32.const 5
            i32.const 4
            local.get 1
            local.get 2
            i64.or
            i64.eqz
            select
        )
            (global (;0;) (mut i32) (i32.const 65536))
        )"#;
        let code = wabt::wat2wasm(contract).expect("invalid wabt");
        let lang = determine_language(&code);
        assert!(
            matches!(lang, Ok(Language::Ink)),
            "Failed to detect Ink! language"
        );
    }

    #[test]
    fn determines_solidity_language() {
        let contract = r#"
        (module
            (type (;0;) (func (param i32 i32 i32)))
            (import "env" "memory" (memory (;0;) 16 16))
            (func (;0;) (type 0))
        )
        "#;
        let code = wabt::wat2wasm(contract).expect("invalid wabt");
        // Custom sections are not supported in wabt format, injecting using parity_wasm
        let mut module: Module = parity_wasm::deserialize_buffer(&code).unwrap();
        module.set_custom_section("producers".to_string(), Vec::new());
        let code = module.into_bytes().unwrap();
        let lang = determine_language(&code);
        assert!(
            matches!(lang, Ok(Language::Solidity)),
            "Failed to detect Solidity language"
        );
    }

    #[test]
    fn determines_assembly_script_language() {
        let contract = r#"
        (module
            (type $none_=>_none (func))
            (type (;0;) (func (param i32 i32 i32)))
            (import "seal" "foo" (func (;0;) (type 0)))
            (import "env" "memory" (memory $0 2 16))
            (start $~start)
            (func $~start (type $none_=>_none))
            (func (;1;) (type 0))
        )
        "#;
        let code = wabt::wat2wasm(contract).expect("invalid wabt");
        // Custom sections are not supported in wabt format, injecting using parity_wasm
        let mut module: Module = parity_wasm::deserialize_buffer(&code).unwrap();
        module.set_custom_section("sourceMappingURL".to_string(), Vec::new());
        let code = module.into_bytes().unwrap();
        let lang = determine_language(&code);
        assert!(
            matches!(lang, Ok(Language::AssemblyScript)),
            "Failed to detect AssemblyScript language"
        );
    }
}