keyfork-mnemonic-util: rewrite to only process entropy on demand

keyfork-mnemonic-util/src/lib.rs

@@ -1,4 +1,4 @@
-use std::{collections::HashMap, error::Error, fmt::Display, str::FromStr, sync::Arc};
+use std::{error::Error, fmt::Display, str::FromStr, sync::Arc};
 
 use hmac::Hmac;
 use pbkdf2::pbkdf2;
@@ -74,9 +74,11 @@ impl Wordlist {
         self.0.get(word)
     }
 
+    /*
     fn inner(&self) -> &Vec<String> {
         &self.0
     }
+    */
 
     #[cfg(test)]
     fn into_inner(self) -> Vec<String> {
@@ -87,18 +89,46 @@ impl Wordlist {
 /// A BIP-0039 mnemonic with reference to a [`Wordlist`].
 #[derive(Debug, Clone)]
 pub struct Mnemonic {
-    words: Vec<usize>,
+    entropy: Vec<u8>,
+    // words: Vec<usize>,
     wordlist: Arc<Wordlist>,
 }
 
 impl Display for Mnemonic {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        let mut iter = self.words.iter().peekable();
+        let bit_count = self.entropy.len() * 8;
-        while let Some(word_index) = iter.next() {
+        let mut bits = vec![false; bit_count + bit_count / 32];
-            let word = self.wordlist.get_word(*word_index).expect("word");
+
-            write!(f, "{word}")?;
+        for byte_index in 0..bit_count / 8 {
+            for bit_index in 0..8 {
+                bits[byte_index * 8 + bit_index] =
+                    (self.entropy[byte_index] & (1 << (7 - bit_index))) > 0;
+            }
+        }
+
+        let mut hasher = Sha256::new();
+        hasher.update(&self.entropy);
+        let hash = hasher.finalize().to_vec();
+        for check_bit in 0..bit_count / 32 {
+            bits[bit_count + check_bit] = (hash[check_bit / 8] & (1 << (7 - (check_bit % 8)))) > 0;
+        }
+
+        let mut iter = bits
+            .chunks_exact(11)
+            .peekable()
+            .map(|chunk| {
+                let mut num = 0usize;
+                for i in 0..11 {
+                    num += usize::from(chunk[10 - i]) << i;
+                }
+                num
+            })
+            .filter_map(|word| self.wordlist.get_word(word))
+            .peekable();
+        while let Some(word) = iter.next() {
+            f.write_str(&word)?;
             if iter.peek().is_some() {
-                write!(f, " ")?;
+                f.write_str(" ")?;
             }
         }
         Ok(())
@@ -114,10 +144,14 @@ pub enum MnemonicFromStrError {
 
     /// One of the words used to generate the mnemonic was not found in the default wordlist.
     InvalidWord(usize),
+
+    /// The checksum for the mnemonic did not match the given words.
+    InvalidChecksum,
 }
 
 impl Display for MnemonicFromStrError {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str("Mnemonic error: ")?;
         match self {
             MnemonicFromStrError::InvalidWordCount(count) => {
                 write!(f, "Incorrect word count: {count}")
@@ -125,6 +159,9 @@ impl Display for MnemonicFromStrError {
             MnemonicFromStrError::InvalidWord(index) => {
                 write!(f, "Unknown word at index: {index}")
             }
+            MnemonicFromStrError::InvalidChecksum => {
+                f.write_str("Checksum of data did not match expected value")
+            }
         }
     }
 }
@@ -135,25 +172,55 @@ impl FromStr for Mnemonic {
     type Err = MnemonicFromStrError;
 
     fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let words: Vec<_> = s.split_whitespace().collect();
+        let mut usize_words = vec![];
         let wordlist = Wordlist::default().arc();
-        let hm: HashMap<&str, usize> = wordlist
+        let mut bits = vec![false; words.len() * 11];
-            .inner()
+        for (index, word) in words.iter().enumerate() {
-            .iter()
+            let word = wordlist
-            .enumerate()
+                .0
-            .map(|(a, b)| (b.as_str(), a))
+                .iter()
-            .collect();
+                .position(|w| &w == word)
-        let mut words: Vec<usize> = Vec::with_capacity(24);
+                .ok_or(MnemonicFromStrError::InvalidWord(index))?;
-        for (index, word) in s.split_whitespace().enumerate() {
+            usize_words.push(word);
-            match hm.get(&word) {
+            for bit in 0..11 {
-                Some(id) => words.push(*id),
+                bits[index * 11 + bit] = (word & (1 << (10 - bit))) > 0;
-                None => return Err(MnemonicFromStrError::InvalidWord(index)),
             }
         }
-        // 3 words for every 32 bits
+
-        if words.len() % 3 != 0 {
+        let mut checksum_bits = vec![false; bits.len() - (bits.len() * 32 / 33)];
-            return Err(MnemonicFromStrError::InvalidWordCount(words.len()));
+        checksum_bits.copy_from_slice(&bits[bits.len() * 32 / 33..]);
+
+        // remove checksum bits
+        bits.truncate(bits.len() * 32 / 33);
+        // bits.truncate(bits.len() - bits.len() % 32);
+
+        let entropy: Vec<u8> = bits
+            .chunks_exact(8)
+            .map(|chunk| {
+                let mut num = 0u8;
+                for i in 0..8 {
+                    num += u8::from(chunk[7 - i]) << i;
+                }
+                num
+            })
+            .collect();
+
+        let mut hasher = Sha256::new();
+        hasher.update(&entropy);
+        let hash = hasher.finalize().to_vec();
+
+        for (i, bit) in checksum_bits.iter().enumerate() {
+            if !hash[i / 8] & (1 << (7 - (i % 8))) == *bit as u8 {
+                return Err(MnemonicFromStrError::InvalidChecksum);
+            }
         }
-        Ok(Mnemonic { words, wordlist })
+
+        Ok(Mnemonic {
+            entropy,
+            // words: usize_words,
+            wordlist,
+        })
     }
 }
 
@@ -176,61 +243,26 @@ impl Mnemonic {
             return Err(MnemonicGenerationError::InvalidByteLength(bit_count));
         }
 
-        Ok(unsafe {Self::from_raw_entropy(bytes, wordlist)})
+        Ok(unsafe { Self::from_raw_entropy(bytes, wordlist) })
     }
 
     pub unsafe fn from_raw_entropy(bytes: &[u8], wordlist: Arc<Wordlist>) -> Mnemonic {
-        let bit_count = bytes.len() * 8;
+        Mnemonic {
-        let mut bits = vec![false; bit_count + bit_count / 32];
+            entropy: bytes.to_vec(),
-
+            wordlist,
-        for byte_index in 0..bit_count / 8 {
-            for bit_index in 0..8 {
-                bits[byte_index * 8 + bit_index] = (bytes[byte_index] & (1 << (7 - bit_index))) > 0;
-            }
         }
+    }
 
-        let mut hasher = Sha256::new();
+    pub fn as_bytes(&self) -> &[u8] {
-        hasher.update(bytes);
+        &self.entropy
-        let hash = hasher.finalize().to_vec();
+    }
-        for check_bit in 0..bit_count / 32 {
-            bits[bit_count + check_bit] = (hash[check_bit / 8] & (1 << (7 - (check_bit % 8)))) > 0;
-        }
 
-        let words = bits
+    pub fn to_bytes(self) -> Vec<u8> {
-            // NOTE: Tested with all approved variants. Always divisible by 11.
+        self.entropy
-            .chunks_exact(11)
-            .map(|chunk| {
-                let mut num = 0usize;
-                for i in 0..11 {
-                    num += usize::from(chunk[10 - i]) << i;
-                }
-                num
-            })
-            .collect::<Vec<_>>();
-
-        Mnemonic { words, wordlist }
     }
 
     pub fn entropy(&self) -> Vec<u8> {
-        let mut bits = vec![false; self.words.len() * 11];
+        self.entropy.clone()
-        for (index, word) in self.words.iter().enumerate() {
-            for bit in 0..11 {
-                bits[index * 11 + bit] = (word & (1 << (10 - bit))) > 0;
-            }
-        }
-
-        // remove checksum bits
-        bits.truncate(bits.len() - bits.len() % 32);
-
-        bits.chunks_exact(8)
-            .map(|chunk| {
-                let mut num = 0u8;
-                for i in 0..8 {
-                    num += u8::from(chunk[7 - i]) << i;
-                }
-                num
-            })
-            .collect()
     }
 
     pub fn seed<'a>(
@@ -247,8 +279,32 @@ impl Mnemonic {
         Ok(seed.to_vec())
     }
 
-    pub fn into_inner(self) -> (Vec<usize>, Arc<Wordlist>) {
+    pub fn words(self) -> (Vec<usize>, Arc<Wordlist>) {
-        (self.words, self.wordlist)
+        let bit_count = self.entropy.len() * 8;
+        let mut bits = vec![false; bit_count + bit_count / 32];
+
+        for byte_index in 0..bit_count / 8 {
+            for bit_index in 0..8 {
+                bits[byte_index * 8 + bit_index] =
+                    (self.entropy[byte_index] & (1 << (7 - bit_index))) > 0;
+            }
+        }
+
+        let mut hasher = Sha256::new();
+        hasher.update(&self.entropy);
+        let hash = hasher.finalize().to_vec();
+        for check_bit in 0..bit_count / 32 {
+            bits[bit_count + check_bit] = (hash[check_bit / 8] & (1 << (7 - (check_bit % 8)))) > 0;
+        }
+
+        let words = bits.chunks_exact(11).peekable().map(|chunk| {
+            let mut num = 0usize;
+            for i in 0..11 {
+                num += usize::from(chunk[10 - i]) << i;
+            }
+            num
+        });
+        (words.collect(), self.wordlist.clone())
     }
 }
 
@@ -329,7 +385,7 @@ mod tests {
         for _ in 0..tests {
             random.read_exact(&mut entropy[..]).unwrap();
             let mnemonic = Mnemonic::from_entropy(&entropy[..256 / 8], wordlist.clone()).unwrap();
-            let (words, _) = mnemonic.into_inner();
+            let (words, _) = mnemonic.words();
             hs.clear();
             hs.extend(words);
             if hs.len() != 24 {
@@ -361,7 +417,7 @@ mod tests {
         let mut random = std::fs::File::open("/dev/urandom").unwrap();
         random.read_exact(&mut entropy[..]).unwrap();
         let mnemonic = unsafe { Mnemonic::from_raw_entropy(&entropy[..], wordlist.clone()) };
-        let (words, _) = mnemonic.into_inner();
+        let (words, _) = mnemonic.words();
         assert!(words.len() == 96);
     }
 }