kobe_primitives/

wallet.rs

//! Unified wallet type for multi-chain key derivation.

use alloc::string::{String, ToString};

use bip39::{Language, Mnemonic};
use zeroize::Zeroizing;

use crate::DeriveError;

/// A unified HD wallet that can derive keys for multiple cryptocurrencies.
///
/// This wallet holds a BIP39 mnemonic and derives a seed that can be used
/// to generate addresses for Bitcoin, Ethereum, and other coins following
/// BIP32/44/49/84 standards.
///
/// # Passphrase Support
///
/// The wallet supports an optional BIP39 passphrase (sometimes called "25th word").
/// This provides an extra layer of security - the same mnemonic with different
/// passphrases will produce completely different wallets.
#[derive(Debug)]
pub struct Wallet {
    /// BIP39 mnemonic phrase.
    mnemonic: Zeroizing<String>,
    /// Seed derived from mnemonic + passphrase.
    seed: Zeroizing<[u8; 64]>,
    /// Whether a passphrase was used.
    has_passphrase: bool,
    /// Language of the mnemonic.
    language: Language,
}

impl Wallet {
    /// Generate a new wallet with a random mnemonic.
    ///
    /// # Arguments
    ///
    /// * `word_count` - Number of words (12, 15, 18, 21, or 24)
    /// * `passphrase` - Optional BIP39 passphrase for additional security
    ///
    /// # Errors
    ///
    /// Returns an error if the word count is invalid.
    ///
    /// # Note
    ///
    /// This function requires the `rand` feature to be enabled.
    #[cfg(feature = "rand")]
    pub fn generate(word_count: usize, passphrase: Option<&str>) -> Result<Self, DeriveError> {
        Self::generate_in(Language::English, word_count, passphrase)
    }

    /// Generate a new wallet with a random mnemonic in the specified language.
    ///
    /// # Arguments
    ///
    /// * `language` - Language for the mnemonic word list
    /// * `word_count` - Number of words (12, 15, 18, 21, or 24)
    /// * `passphrase` - Optional BIP39 passphrase for additional security
    ///
    /// # Errors
    ///
    /// Returns an error if the word count is invalid.
    ///
    /// # Note
    ///
    /// This function requires the `rand` feature to be enabled.
    #[cfg(feature = "rand")]
    pub fn generate_in(
        language: Language,
        word_count: usize,
        passphrase: Option<&str>,
    ) -> Result<Self, DeriveError> {
        if !matches!(word_count, 12 | 15 | 18 | 21 | 24) {
            return Err(DeriveError::Input(alloc::format!(
                "word count must be 12, 15, 18, 21, or 24, got {word_count}"
            )));
        }

        let mnemonic = Mnemonic::generate_in(language, word_count)?;
        Ok(Self::from_parts(&mnemonic, language, passphrase))
    }

    /// Generate a new wallet with a custom random number generator.
    ///
    /// This is useful in `no_std` environments where you provide your own
    /// cryptographically secure RNG instead of relying on the system RNG.
    ///
    /// # Arguments
    ///
    /// * `rng` - A cryptographically secure random number generator
    /// * `language` - Language for the mnemonic word list
    /// * `word_count` - Number of words (12, 15, 18, 21, or 24)
    /// * `passphrase` - Optional BIP39 passphrase for additional security
    ///
    /// # Errors
    ///
    /// Returns an error if the word count is invalid.
    ///
    /// # Note
    ///
    /// This function requires the `rand_core` feature to be enabled.
    #[cfg(feature = "rand_core")]
    pub fn generate_in_with<R>(
        rng: &mut R,
        language: Language,
        word_count: usize,
        passphrase: Option<&str>,
    ) -> Result<Self, DeriveError>
    where
        R: bip39::rand_core::RngCore + bip39::rand_core::CryptoRng,
    {
        if !matches!(word_count, 12 | 15 | 18 | 21 | 24) {
            return Err(DeriveError::Input(alloc::format!(
                "word count must be 12, 15, 18, 21, or 24, got {word_count}"
            )));
        }

        let mnemonic = Mnemonic::generate_in_with(rng, language, word_count)?;
        Ok(Self::from_parts(&mnemonic, language, passphrase))
    }

    /// Create a wallet from raw entropy bytes (English by default).
    ///
    /// This is useful in `no_std` environments where you provide your own entropy
    /// source instead of relying on the system RNG.
    ///
    /// # Arguments
    ///
    /// * `entropy` - Raw entropy bytes (16, 20, 24, 28, or 32 bytes for 12-24 words)
    /// * `passphrase` - Optional BIP39 passphrase for additional security
    ///
    /// # Errors
    ///
    /// Returns an error if the entropy length is invalid.
    pub fn from_entropy(entropy: &[u8], passphrase: Option<&str>) -> Result<Self, DeriveError> {
        Self::from_entropy_in(Language::English, entropy, passphrase)
    }

    /// Create a wallet from raw entropy bytes in the specified language.
    ///
    /// This is useful in `no_std` environments where you provide your own entropy
    /// source instead of relying on the system RNG.
    ///
    /// # Arguments
    ///
    /// * `language` - Language for the mnemonic word list
    /// * `entropy` - Raw entropy bytes (16, 20, 24, 28, or 32 bytes for 12-24 words)
    /// * `passphrase` - Optional BIP39 passphrase for additional security
    ///
    /// # Errors
    ///
    /// Returns an error if the entropy length is invalid.
    pub fn from_entropy_in(
        language: Language,
        entropy: &[u8],
        passphrase: Option<&str>,
    ) -> Result<Self, DeriveError> {
        let mnemonic = Mnemonic::from_entropy_in(language, entropy)?;
        Ok(Self::from_parts(&mnemonic, language, passphrase))
    }

    /// Create a wallet from an existing mnemonic phrase.
    ///
    /// The language will be automatically detected from the phrase.
    ///
    /// # Arguments
    ///
    /// * `phrase` - BIP39 mnemonic phrase
    /// * `passphrase` - Optional BIP39 passphrase
    ///
    /// # Errors
    ///
    /// Returns an error if the mnemonic is invalid.
    pub fn from_mnemonic(phrase: &str, passphrase: Option<&str>) -> Result<Self, DeriveError> {
        let mnemonic: Mnemonic = phrase.parse()?;
        let language = mnemonic.language();
        Ok(Self::from_parts(&mnemonic, language, passphrase))
    }

    /// Create a wallet from an existing mnemonic phrase in the specified language.
    ///
    /// # Arguments
    ///
    /// * `language` - Language for the mnemonic word list
    /// * `phrase` - BIP39 mnemonic phrase
    /// * `passphrase` - Optional BIP39 passphrase
    ///
    /// # Errors
    ///
    /// Returns an error if the mnemonic is invalid.
    pub fn from_mnemonic_in(
        language: Language,
        phrase: &str,
        passphrase: Option<&str>,
    ) -> Result<Self, DeriveError> {
        let mnemonic = Mnemonic::parse_in(language, phrase)?;
        Ok(Self::from_parts(&mnemonic, language, passphrase))
    }

    /// Build a wallet from a validated mnemonic, deriving the seed.
    fn from_parts(mnemonic: &Mnemonic, language: Language, passphrase: Option<&str>) -> Self {
        let passphrase_str = passphrase.unwrap_or("");
        let seed_bytes = mnemonic.to_seed(passphrase_str);
        Self {
            mnemonic: Zeroizing::new(mnemonic.to_string()),
            seed: Zeroizing::new(seed_bytes),
            has_passphrase: passphrase.is_some(),
            language,
        }
    }

    /// Get the mnemonic phrase.
    ///
    /// **Security Warning**: Handle this value carefully as it can
    /// reconstruct all derived keys.
    #[inline]
    #[must_use]
    pub fn mnemonic(&self) -> &str {
        &self.mnemonic
    }

    /// Get the seed bytes for key derivation.
    ///
    /// This seed can be used by chain-specific derivers (Bitcoin, Ethereum, etc.)
    /// to generate addresses following their respective standards.
    #[inline]
    #[must_use]
    pub fn seed(&self) -> &[u8; 64] {
        &self.seed
    }

    /// Check if a passphrase was supplied at construction time.
    ///
    /// Returns `true` whenever the caller passed `Some(_)` to the constructor,
    /// even if the passphrase string itself was empty. Callers relying on
    /// "non-empty passphrase" semantics must check the passphrase string before
    /// constructing the wallet.
    #[must_use]
    pub const fn has_passphrase(&self) -> bool {
        self.has_passphrase
    }

    /// Get the language of the mnemonic.
    #[inline]
    #[must_use]
    pub const fn language(&self) -> Language {
        self.language
    }

    /// Get the word count of the mnemonic.
    #[inline]
    #[must_use]
    pub fn word_count(&self) -> usize {
        self.mnemonic.split_whitespace().count()
    }
}

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

    const TEST_MNEMONIC: &str = "abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about";

    #[cfg(feature = "rand")]
    #[test]
    fn test_generate_12_words() {
        let wallet = Wallet::generate(12, None).unwrap();
        assert_eq!(wallet.word_count(), 12);
        assert!(!wallet.has_passphrase());
    }

    #[cfg(feature = "rand")]
    #[test]
    fn test_generate_24_words() {
        let wallet = Wallet::generate(24, None).unwrap();
        assert_eq!(wallet.word_count(), 24);
    }

    #[cfg(feature = "rand")]
    #[test]
    fn test_generate_with_passphrase() {
        let wallet = Wallet::generate(12, Some("secret")).unwrap();
        assert!(wallet.has_passphrase());
    }

    #[test]
    fn test_invalid_entropy_length() {
        // 15 bytes is invalid (should be 16, 20, 24, 28, or 32)
        let result = Wallet::from_entropy(&[0u8; 15], None);
        assert!(result.is_err());
    }

    #[test]
    fn test_from_entropy() {
        // 16 bytes = 12 words
        let entropy = [0u8; 16];
        let wallet = Wallet::from_entropy(&entropy, None).unwrap();
        assert_eq!(wallet.word_count(), 12);
    }

    #[test]
    fn test_from_mnemonic() {
        let wallet = Wallet::from_mnemonic(TEST_MNEMONIC, None).unwrap();
        assert_eq!(wallet.mnemonic(), TEST_MNEMONIC);
    }

    #[test]
    fn test_passphrase_changes_seed() {
        let wallet1 = Wallet::from_mnemonic(TEST_MNEMONIC, None).unwrap();
        let wallet2 = Wallet::from_mnemonic(TEST_MNEMONIC, Some("password")).unwrap();

        // Same mnemonic with different passphrase should produce different seeds
        assert_ne!(wallet1.seed(), wallet2.seed());
    }

    #[test]
    fn test_deterministic_seed() {
        let wallet1 = Wallet::from_mnemonic(TEST_MNEMONIC, Some("test")).unwrap();
        let wallet2 = Wallet::from_mnemonic(TEST_MNEMONIC, Some("test")).unwrap();
        assert_eq!(wallet1.seed(), wallet2.seed());
    }

    #[test]
    fn kat_bip39_seed_vector() {
        // BIP-39 reference: "abandon...about" with empty passphrase
        // Verified against Python pbkdf2_hmac + iancoleman.io
        let wallet = Wallet::from_mnemonic(TEST_MNEMONIC, None).unwrap();
        assert_eq!(
            hex::encode(wallet.seed()),
            "5eb00bbddcf069084889a8ab9155568165f5c453ccb85e70811aaed6f6da5fc1\
             9a5ac40b389cd370d086206dec8aa6c43daea6690f20ad3d8d48b2d2ce9e38e4"
        );
    }

    #[test]
    fn kat_all_zero_entropy_produces_abandon_about() {
        let wallet = Wallet::from_entropy(&[0u8; 16], None).unwrap();
        assert_eq!(wallet.mnemonic(), TEST_MNEMONIC);
    }
}