refactor: try to minimize memory footprint.

Cargo.toml

@@ -17,9 +17,12 @@ categories = ["cryptography"]
 maintenance = { status = "as-is" }
 
 [dependencies]
-rand = { version = "0.8.0", features = ["rand_chacha"] }
+thiserror = "1.0.63"
-rand_chacha = "0.3.1"
+rand = { version = "0.8.5" }
+rand_chacha = { version = "0.3.1", optional = true }
+rand_pcg = { version = "0.3.1", optional = true }
+byteorder = "1.5.0"
 
 [features]
-default = ["secure_random"]
+default = ["rand_pcg"]
-secure_random = ["rand/getrandom"]
+secure_random = ["rand/getrandom", "rand/rand_chacha", "rand_chacha"]

src/cbc.rs

@@ -0,0 +1,276 @@
+use rand::prelude::*;
+use std::cmp::min;
+
+use super::{ecb, TcTeaError};
+
+const SALT_LEN: usize = 2;
+const ZERO_LEN: usize = 7;
+const FIXED_PADDING_LEN: usize = 1 + SALT_LEN + ZERO_LEN;
+
+/// Calculate expected size of encrypted data.
+///
+/// `body_size` is the size of data you'd like to encrypt.
+pub fn get_encrypted_size(body_size: usize) -> usize {
+    let len = FIXED_PADDING_LEN + body_size;
+    let pad_len = (8 - (len & 0b0111)) & 0b0111;
+    len + pad_len
+}
+
+fn xor_tea_block(a: &[u8; 8], b: &[u8; 8]) -> [u8; 8] {
+    let mut dest = *a;
+    dest.iter_mut().zip(b).for_each(|(a, b)| *a ^= *b);
+    dest
+}
+
+#[inline(always)]
+fn encrypt_round(
+    cipher: &mut [u8],
+    plain: &[u8],
+    key: &[u32; 4],
+    iv1: &mut [u8; 8],
+    iv2: &mut [u8; 8],
+) {
+    let mut plain_block = [0u8; 8];
+    plain_block.copy_from_slice(plain);
+
+    let iv2_next = xor_tea_block(&plain_block, iv1);
+    let mut result = iv2_next;
+    ecb::encrypt(&mut result, key);
+
+    let cipher_block = xor_tea_block(&result, iv2);
+    *iv1 = cipher_block;
+    *iv2 = iv2_next;
+    cipher[..8].copy_from_slice(&cipher_block);
+}
+
+pub fn encrypt<'a>(
+    cipher: &'a mut [u8],
+    plain: &[u8],
+    key: &[u32; 4],
+) -> Result<&'a [u8], TcTeaError> {
+    // buffer size calculation
+    let len = FIXED_PADDING_LEN + plain.len();
+    let pad_len = (8 - (len & 0b0111)) & 0b0111;
+    let expected_output_len = len + pad_len; // add our padding
+    if cipher.len() < expected_output_len {
+        Err(TcTeaError::DecryptBufferTooSmall(
+            expected_output_len,
+            cipher.len(),
+        ))?;
+    }
+
+    let header_len = 1 + pad_len + SALT_LEN;
+
+    // Setup buffer
+    let cipher = &mut cipher[..expected_output_len];
+    let mut header = [0u8; 16];
+
+    // Set up a header with random padding/salt
+    #[cfg(feature = "secure_random")]
+    ChaCha20Rng::from_entropy().fill_bytes(&mut header[0..header_len]);
+    #[cfg(not(feature = "secure_random"))]
+    rand_pcg::Pcg32::from_entropy().fill_bytes(&mut header[0..header_len]);
+
+    // Build header
+    let copy_to_header_len = min(16 - header_len, plain.len());
+    let (plain_header, plain) = plain.split_at(copy_to_header_len);
+
+    header[0] = (header[0] & 0b1111_1000) | ((pad_len as u8) & 0b0000_0111);
+    header[header_len..header_len + copy_to_header_len].copy_from_slice(plain_header);
+
+    {
+        let mut iv1 = [0u8; 8];
+        let mut iv2 = [0u8; 8];
+
+        let plain_last_block_len = plain.len() % 8;
+        let (plain, plain_last_block) = plain.split_at(plain.len() - plain_last_block_len);
+
+        // Encrypt first 2 blocks from the header, then whole blocks
+        // cbc_encrypt_round(cipher, &header, key, &mut iv1, &mut iv2);
+        encrypt_round(cipher, &header[..8], key, &mut iv1, &mut iv2);
+        let cipher = &mut cipher[8..];
+
+        encrypt_round(cipher, &header[8..], key, &mut iv1, &mut iv2);
+        let mut cipher = &mut cipher[8..];
+
+        if !plain.is_empty() {
+            for (plain, cipher) in plain.chunks_exact(8).zip(cipher.chunks_exact_mut(8)) {
+                encrypt_round(cipher, plain, key, &mut iv1, &mut iv2);
+            }
+            cipher = &mut cipher[plain.len()..];
+        }
+
+        if plain_last_block_len != 0 {
+            let mut last_block = [0u8; 8];
+            last_block[..plain_last_block_len].copy_from_slice(plain_last_block);
+            encrypt_round(cipher, &last_block, key, &mut iv1, &mut iv2);
+        }
+    }
+
+    // Done.
+    Ok(cipher)
+}
+
+#[inline(always)]
+fn decrypt_round(
+    plain: &mut [u8],
+    cipher: &[u8],
+    key: &[u32; 4],
+    iv1: &mut [u8; 8],
+    iv2: &mut [u8; 8],
+) {
+    let mut cipher_block = [0u8; 8];
+    cipher_block.copy_from_slice(cipher);
+
+    let mut result = xor_tea_block(&cipher_block, iv2);
+    ecb::decrypt(&mut result, key);
+    let plain_block = xor_tea_block(&result, iv1);
+
+    *iv1 = cipher_block;
+    *iv2 = result;
+
+    plain[..8].copy_from_slice(&plain_block);
+}
+
+pub fn decrypt<'a>(
+    plain: &'a mut [u8],
+    cipher: &[u8],
+    key: &[u32; 4],
+) -> Result<&'a [u8], TcTeaError> {
+    let input_len = cipher.len();
+    if (input_len < FIXED_PADDING_LEN) || (input_len % 8 != 0) {
+        Err(TcTeaError::InvalidDataSize(input_len))?;
+    }
+    let output_len = plain.len();
+    if output_len < input_len {
+        Err(TcTeaError::DecryptBufferTooSmall(input_len, output_len))?;
+    }
+
+    let plain = &mut plain[..input_len];
+    let mut iv1 = [0u8; 8];
+    let mut iv2 = [0u8; 8];
+    for (cipher, plain) in cipher.chunks_exact(8).zip(plain.chunks_exact_mut(8)) {
+        decrypt_round(plain, cipher, key, &mut iv1, &mut iv2);
+    }
+
+    let pad_size = usize::from(plain[0] & 0b111);
+
+    // Prefixed with "pad_size", "padding", "salt"
+    let start_loc = 1 + pad_size + SALT_LEN;
+    let end_loc = input_len - ZERO_LEN;
+
+    if plain[end_loc..].iter().fold(0u8, |acc, v| acc | v) != 0 {
+        plain.fill(0);
+        Err(TcTeaError::InvalidPadding)?
+    }
+
+    Ok(&plain[start_loc..end_loc])
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // Known good data, generated from its C++ implementation
+    const GOOD_ENCRYPTED_DATA: [u8; 24] = [
+        0x91, 0x09, 0x51, 0x62, 0xe3, 0xf5, 0xb6, 0xdc, //
+        0x6b, 0x41, 0x4b, 0x50, 0xd1, 0xa5, 0xb8, 0x4e, //
+        0xc5, 0x0d, 0x0c, 0x1b, 0x11, 0x96, 0xfd, 0x3c, //
+    ];
+
+    const ENCRYPTION_KEY: [u32; 4] = [0x31323334, 0x35363738, 0x41424344, 0x45464748];
+
+    const EXPECTED_PLAIN_TEXT: [u8; 8] = [1, 2, 3, 4, 5, 6, 7, 8];
+
+    #[test]
+    fn tc_tea_basic_decryption() -> Result<(), TcTeaError> {
+        let mut plain = vec![0u8; 24];
+        let result = decrypt(&mut plain, &GOOD_ENCRYPTED_DATA, &ENCRYPTION_KEY)?;
+        assert_eq!(result, &EXPECTED_PLAIN_TEXT);
+        Ok(())
+    }
+
+    #[test]
+    fn tc_tea_decryption_reject_non_zero_byte() {
+        let mut bad_data = GOOD_ENCRYPTED_DATA;
+        bad_data[23] ^= 0xff; // last byte
+        let mut plain = vec![0xffu8; 24];
+        assert_eq!(
+            decrypt(&mut plain, &bad_data, &ENCRYPTION_KEY),
+            Err(TcTeaError::InvalidPadding)
+        );
+    }
+
+    #[test]
+    fn tc_tea_encrypt_empty() -> Result<(), TcTeaError> {
+        let mut cipher_buffer = [0xffu8; 100];
+        let cipher = encrypt(&mut cipher_buffer, b"", &ENCRYPTION_KEY)?;
+        assert_eq!(cipher.len(), 16);
+
+        let mut plain = vec![0xffu8; 24];
+        // Since encryption utilises random numbers, we are just going to
+        let decrypted = decrypt(&mut plain, cipher, &ENCRYPTION_KEY)?;
+        assert_eq!(decrypted, b"");
+
+        Ok(())
+    }
+
+    #[test]
+    fn tc_tea_basic_encryption() -> Result<(), TcTeaError> {
+        let mut cipher_buffer = [0xffu8; 100];
+        let cipher = encrypt(&mut cipher_buffer, &EXPECTED_PLAIN_TEXT, &ENCRYPTION_KEY)?;
+        assert_eq!(cipher.len(), 24);
+
+        let mut plain = vec![0xffu8; 24];
+        // Since encryption utilises random numbers, we are just going to
+        let decrypted = decrypt(&mut plain, cipher, &ENCRYPTION_KEY)?;
+        assert_eq!(decrypted, &EXPECTED_PLAIN_TEXT);
+
+        Ok(())
+    }
+
+    #[test]
+    fn tc_tea_test_long_encryption() -> Result<(), TcTeaError> {
+        let mut cipher_buffer = [0xffu8; 100];
+        let input = b"...test data by Jixun ... ... test hello aaa";
+        for _ in 0..16 {
+            let cipher = encrypt(&mut cipher_buffer, input, &ENCRYPTION_KEY)?;
+            assert_eq!(cipher.len() % 8, 0);
+            assert!(cipher.len() > input.len());
+
+            // Since encryption utilises random numbers, we are just going to
+            let mut plain = vec![0xffu8; cipher.len()];
+            let decrypted = decrypt(&mut plain, cipher, &ENCRYPTION_KEY)?;
+            assert_eq!(decrypted, input);
+        }
+
+        Ok(())
+    }
+
+    #[test]
+    fn tc_tea_test_various_len() -> Result<(), TcTeaError> {
+        let mut cipher_buffer = [0xffu8; 100];
+        let mut plain_buffer = [0xffu8; 100];
+
+        let input = b"...test data by Jixun ... ... test hello aaa";
+        for test_len in 0usize..input.len() {
+            let input = &input[..test_len];
+            let cipher = encrypt(&mut cipher_buffer, input, &ENCRYPTION_KEY)?;
+            let decrypted = decrypt(&mut plain_buffer, cipher, &ENCRYPTION_KEY)?;
+            assert_eq!(decrypted, input);
+        }
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_calc_encrypted_size() {
+        assert_eq!(get_encrypted_size(0), 16);
+        assert_eq!(get_encrypted_size(1), 16);
+        assert_eq!(get_encrypted_size(6), 16);
+
+        assert_eq!(get_encrypted_size(7), 24);
+        assert_eq!(get_encrypted_size(14), 24);
+        assert_eq!(get_encrypted_size(15), 32);
+    }
+}

src/ecb.rs

@@ -0,0 +1,73 @@
+use byteorder::{ByteOrder, BE};
+
+// Tencent chooses 16 rounds instead of traditional 32 rounds.
+const ROUNDS: u32 = 16;
+const DELTA: u32 = 0x9e3779b9;
+
+/// Perform a single round of encrypting/decrypting wrapping arithmetics
+fn ecb_single_round(value: u32, sum: u32, key1: u32, key2: u32) -> u32 {
+    let left = value.wrapping_shl(4).wrapping_add(key1);
+    let right = value.wrapping_shr(5).wrapping_add(key2);
+    let mid = sum.wrapping_add(value);
+
+    left ^ mid ^ right
+}
+
+/// Perform a 16 round TEA ECB encryption.
+pub fn encrypt(block: &mut [u8; 8], k: &[u32; 4]) {
+    let mut y = BE::read_u32(&block[..4]);
+    let mut z = BE::read_u32(&block[4..]);
+    let mut sum = 0_u32;
+
+    for _ in 0..ROUNDS {
+        sum = sum.wrapping_add(DELTA);
+
+        y = y.wrapping_add(ecb_single_round(z, sum, k[0], k[1]));
+        z = z.wrapping_add(ecb_single_round(y, sum, k[2], k[3]));
+    }
+
+    BE::write_u32(&mut block[..4], y);
+    BE::write_u32(&mut block[4..], z);
+}
+
+/// Perform a 16 round TEA ECB decryption.
+pub fn decrypt(block: &mut [u8; 8], key: &[u32; 4]) {
+    let mut y = BE::read_u32(&block[..4]);
+    let mut z = BE::read_u32(&block[4..]);
+    let mut sum = DELTA.wrapping_mul(ROUNDS);
+
+    for _ in 0..ROUNDS {
+        z = z.wrapping_sub(ecb_single_round(y, sum, key[2], key[3]));
+        y = y.wrapping_sub(ecb_single_round(z, sum, key[0], key[1]));
+
+        sum = sum.wrapping_sub(DELTA);
+    }
+
+    BE::write_u32(&mut block[..4], y);
+    BE::write_u32(&mut block[4..], z);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_decryption() {
+        let mut data: [u8; 8] = [0x56, 0x27, 0x6b, 0xa9, 0x80, 0xb9, 0xec, 0x16];
+        let key: [u32; 4] = [0x01020304, 0x05060708, 0x090a0b0c, 0x0d0e0f00];
+        let expected: [u8; 8] = [1, 2, 3, 4, 5, 6, 7, 8];
+
+        decrypt(&mut data, &key);
+        assert_eq!(data, expected);
+    }
+
+    #[test]
+    fn test_encryption() {
+        let mut data: [u8; 8] = [1, 2, 3, 4, 5, 6, 7, 8];
+        let key: [u32; 4] = [0x01020304, 0x05060708, 0x090a0b0c, 0x0d0e0f00];
+        let expected: [u8; 8] = [0x56, 0x27, 0x6b, 0xa9, 0x80, 0xb9, 0xec, 0x16];
+
+        encrypt(&mut data, &key);
+        assert_eq!(data, expected);
+    }
+}

src/lib.rs

@@ -2,9 +2,78 @@
 //!
 //! Notably, it uses a different round number and uses a "tweaked" CBC mode.
 
-mod stream_ext;
+use byteorder::{ByteOrder, BE};
-mod tc_tea_public;
+use thiserror::Error;
-mod tc_tea_internal;
-mod tc_tea_cbc;
 
-pub use tc_tea_public::*;
+pub mod cbc;
+pub mod ecb;
+
+#[derive(Error, Debug, PartialEq)]
+pub enum TcTeaError {
+    #[error("Key size mismatch. Required 16 bytes, got {0} bytes")]
+    KeyTooShort(usize),
+    #[error("Cipher text size invalid. {0} mod 8 != 0.")]
+    InvalidDataSize(usize),
+    #[error("Decrypt buffer size too small, it should be at least {0} bytes (actual={1} bytes).")]
+    DecryptBufferTooSmall(usize, usize),
+    #[error("Encrypt buffer size too small, it should be at least {0} bytes (actual={1} bytes).")]
+    EncryptBufferTooSmall(usize, usize),
+    #[error("Invalid data padding")]
+    InvalidPadding,
+    #[error("Slice error.")]
+    SliceError,
+}
+
+/// Parse key to u32 array
+pub fn parse_key(key: &[u8]) -> Result<[u32; 4], TcTeaError> {
+    let key_chunks = match key.len() {
+        16 => key.chunks(4),
+        key_length => Err(TcTeaError::KeyTooShort(key_length))?,
+    };
+
+    let mut parsed = [0u32; 4];
+    for (key, key_chunk) in parsed.iter_mut().zip(key_chunks) {
+        *key = BE::read_u32(key_chunk);
+    }
+    Ok(parsed)
+}
+
+/// Encrypts an arbitrary length sized data in the following way:
+///
+/// * PadLen  (1 byte)
+/// * Padding (variable, 0-7byte)
+/// * Salt    (2 bytes)
+/// * Body    (? bytes)
+/// * Zero    (7 bytes)
+///
+/// Returned bytes will always have a length multiple of 8.
+///
+/// PadLen/Padding/Salt are randomly bytes, with a minimum of 21 bits (3 * 8 - 3) randomness.
+///
+/// # Panics
+///
+/// If random number generator fails, it will panic.
+pub fn encrypt<T: AsRef<[u8]>>(plaintext: T, key: &[u8]) -> Result<Vec<u8>, TcTeaError> {
+    let key = parse_key(key)?;
+    let plaintext = plaintext.as_ref();
+    let mut cipher = vec![0u8; plaintext.len()];
+    let result = cbc::decrypt(&mut cipher, plaintext, &key)?;
+    Ok(Vec::from(result))
+}
+
+/// Decrypts a byte array containing the following:
+///
+/// * PadLen  (1 byte)
+/// * Padding (variable, 0-7byte)
+/// * Salt    (2 bytes)
+/// * Body    (? bytes)
+/// * Zero    (7 bytes)
+///
+/// PadLen is taken from the last 3 bit of the first byte.
+pub fn decrypt<T: AsRef<[u8]>>(encrypted: T, key: &[u8]) -> Result<Vec<u8>, TcTeaError> {
+    let key = parse_key(key)?;
+    let encrypted = encrypted.as_ref();
+    let mut plain = vec![0u8; encrypted.len()];
+    let result = cbc::decrypt(&mut plain, encrypted, &key)?;
+    Ok(Vec::from(result))
+}

src/stream_ext.rs

@@ -1,80 +0,0 @@
-use std::ops::BitOr;
-
-pub trait StreamExt {
-    fn read_u32_be(&self, offset: usize) -> u32;
-    fn write_u32_be(&mut self, offset: usize, value: u32);
-    fn xor_block(&mut self, dst_offset: usize, size: usize, src: &[u8], src_offset: usize);
-    fn is_all_zeros(&self) -> bool;
-
-    fn xor_prev_tea_block(&mut self, offset: usize);
-    fn copy_tea_block(&mut self, offset: usize, src: &[u8], src_offset: usize);
-    fn xor_tea_block(&mut self, dst_offset: usize, src: &[u8], src_offset: usize);
-}
-
-impl StreamExt for [u8] {
-    #[inline]
-    fn read_u32_be(&self, offset: usize) -> u32 {
-        (u32::from(self[offset]) << 24)
-            | (u32::from(self[offset + 1]) << 16)
-            | (u32::from(self[offset + 2]) << 8)
-            | (u32::from(self[offset + 3]))
-    }
-
-    #[inline]
-    fn write_u32_be(&mut self, offset: usize, value: u32) {
-        self[offset..offset + 4].copy_from_slice(&value.to_be_bytes());
-    }
-
-    #[inline]
-    fn xor_block(&mut self, dst_offset: usize, size: usize, src: &[u8], src_offset: usize) {
-        for i in 0..size {
-            self[dst_offset + i] ^= src[src_offset + i];
-        }
-    }
-
-    /// Constant time all zero comparison
-    /// Attempts to do constant time comparison,
-    ///   but probably gets optimised away by llvm... lol
-    fn is_all_zeros(&self) -> bool {
-        self.iter().fold(0u8, |acc, b| acc.bitor(b)) == 0
-    }
-
-    #[inline]
-    fn xor_prev_tea_block(&mut self, offset: usize) {
-        for i in offset..offset + 8 {
-            self[i] ^= self[i - 8];
-        }
-    }
-
-    #[inline]
-    fn copy_tea_block(&mut self, offset: usize, src: &[u8], src_offset: usize) {
-        self[offset..offset + 8]
-            .as_mut()
-            .copy_from_slice(&src[src_offset..src_offset + 8]);
-    }
-
-    #[inline]
-    fn xor_tea_block(&mut self, dst_offset: usize, src: &[u8], src_offset: usize) {
-        self.xor_block(dst_offset, 8, src, src_offset);
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn test_read_u32_be() {
-        let v1 = [1, 2, 3, 4];
-        let v2 = [0x7f, 0xff, 0xee, 0xdd, 0xcc];
-        assert_eq!(v1.read_u32_be(0), 0x01020304);
-        assert_eq!(v2.read_u32_be(1), 0xffeeddcc);
-    }
-
-    #[test]
-    fn test_write_u32_be() {
-        let v2 = &mut [0x7fu8, 0xff, 0xee, 0xdd, 0xcc];
-        v2.write_u32_be(0, 0x01020304);
-        assert_eq!(v2, &[1u8, 2, 3, 4, 0xcc]);
-    }
-}

src/tc_tea_cbc.rs

@@ -1,170 +0,0 @@
-use rand::prelude::*;
-use rand_chacha::ChaCha20Rng;
-
-use super::stream_ext::StreamExt;
-use super::tc_tea_internal::{ecb_decrypt, ecb_encrypt, parse_key};
-
-const SALT_LEN: usize = 2;
-const ZERO_LEN: usize = 7;
-const FIXED_PADDING_LEN: usize = 1 + SALT_LEN + ZERO_LEN;
-
-/// Calculate expected size of encrypted data.
-///
-/// `body_size` is the size of data you'd like to encrypt.
-pub fn calc_encrypted_size(body_size: usize) -> usize {
-    let len = FIXED_PADDING_LEN + body_size;
-    let pad_len = (8 - (len & 0b0111)) & 0b0111;
-    len + pad_len
-}
-
-pub fn encrypt(plaintext: &[u8], key: &[u8]) -> Option<Box<[u8]>> {
-    let key = parse_key(key)?;
-
-    // buffer size calculation
-    let len = FIXED_PADDING_LEN + plaintext.len();
-    let pad_len = (8 - (len & 0b0111)) & 0b0111;
-    let len = len + pad_len; // add our padding
-    debug_assert_eq!(
-        len,
-        calc_encrypted_size(plaintext.len()),
-        "encrypted size calculation mismatch"
-    );
-    let header_len = 1 + pad_len + SALT_LEN;
-
-    // Setup buffer
-    let mut encrypted = vec![0u8; len].into_boxed_slice();
-    let mut iv1 = vec![0u8; len].into_boxed_slice();
-
-    // Setup a header with random padding/salt
-    #[cfg(feature = "secure_random")]
-        ChaCha20Rng::from_entropy().fill_bytes(&mut encrypted[0..header_len]);
-
-    #[cfg(not(feature = "secure_random"))]
-        ChaCha20Rng::from_rng(thread_rng())
-        .unwrap()
-        .fill_bytes(&mut encrypted[0..header_len]);
-
-    encrypted[0] = (encrypted[0] & 0b1111_1000) | ((pad_len as u8) & 0b0000_0111);
-
-    // Copy input to destination buffer.
-    encrypted[header_len..header_len + plaintext.len()]
-        .as_mut()
-        .copy_from_slice(plaintext);
-
-    // First block
-    iv1.copy_tea_block(0, &encrypted, 0); // preserve iv2 for first block
-    ecb_encrypt(&mut encrypted[0..8], &key); // transform first block
-
-    // Rest of the block
-    for i in (8..len).step_by(8) {
-        encrypted.xor_prev_tea_block(i); // XOR iv2
-        iv1.copy_tea_block(i, &encrypted, i); // store iv1
-        ecb_encrypt(&mut encrypted[i..i + 8], &key); // TEA ECB
-        encrypted.xor_tea_block(i, &iv1, i - 8); // XOR iv1 (from prev block)
-    }
-
-    // Done.
-    Some(encrypted)
-}
-
-pub fn decrypt(encrypted: &[u8], key: &[u8]) -> Option<Box<[u8]>> {
-    let key = parse_key(key)?;
-    let len = encrypted.len();
-    if (len < FIXED_PADDING_LEN) || (len % 8 != 0) {
-        return None;
-    }
-
-    let mut decrypted_buf = encrypted.to_vec();
-
-    // First block
-    ecb_decrypt(&mut decrypted_buf[0..8], &key);
-
-    // Rest of the block
-    for i in (8..len).step_by(8) {
-        decrypted_buf.xor_prev_tea_block(i); // xor iv1
-        ecb_decrypt(&mut decrypted_buf[i..i + 8], &key);
-    }
-
-    // Finalise: XOR iv2 (cipher text)
-    decrypted_buf.xor_block(8, len - 8, encrypted, 0);
-
-    let pad_size = usize::from(decrypted_buf[0] & 0b111);
-
-    // Prefixed with "pad_size", "padding", "salt"
-    let start_loc = 1 + pad_size + SALT_LEN;
-    let end_loc = len - ZERO_LEN;
-
-    if decrypted_buf[end_loc..].is_all_zeros() {
-        Some(
-            decrypted_buf[start_loc..end_loc]
-                .to_vec()
-                .into_boxed_slice(),
-        )
-    } else {
-        None
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    // Known good data, generated from its C++ implementation
-    const GOOD_ENCRYPTED_DATA: [u8; 24] = [
-        0x91, 0x09, 0x51, 0x62, 0xe3, 0xf5, 0xb6, 0xdc, //
-        0x6b, 0x41, 0x4b, 0x50, 0xd1, 0xa5, 0xb8, 0x4e, //
-        0xc5, 0x0d, 0x0c, 0x1b, 0x11, 0x96, 0xfd, 0x3c, //
-    ];
-
-    const ENCRYPTION_KEY: &[u8; 16] = b"12345678ABCDEFGH";
-
-    const GOOD_DECRYPTED_DATA: [u8; 8] = [1u8, 2, 3, 4, 5, 6, 7, 8];
-
-    #[test]
-    fn tc_tea_basic_decryption() {
-        let result = decrypt(&GOOD_ENCRYPTED_DATA, ENCRYPTION_KEY).unwrap();
-        assert_eq!(result, GOOD_DECRYPTED_DATA.into());
-    }
-
-    #[test]
-    fn tc_tea_decryption_reject_non_zero_byte() {
-        let mut bad_data = GOOD_ENCRYPTED_DATA;
-        bad_data[23] ^= 0xff; // last byte
-        assert!(decrypt(&bad_data, ENCRYPTION_KEY).is_none());
-    }
-
-    #[test]
-    fn tc_tea_basic_encryption() {
-        let encrypted = encrypt(&GOOD_DECRYPTED_DATA, ENCRYPTION_KEY).unwrap();
-        assert_eq!(encrypted.len(), 24);
-
-        // Since encryption utilises random numbers, we are just going to
-        let decrypted = decrypt(&encrypted, ENCRYPTION_KEY).unwrap();
-        assert_eq!(decrypted, GOOD_DECRYPTED_DATA.into());
-    }
-
-    #[test]
-    fn tc_tea_test_long_encryption() {
-        let input = b"...test data by Jixun";
-        for _ in 0..16 {
-            let encrypted = encrypt(input, ENCRYPTION_KEY).unwrap();
-            assert_eq!(encrypted.len() % 8, 0);
-            assert!(encrypted.len() > input.len());
-
-            // Since encryption utilises random numbers, we are just going to
-            let decrypted = decrypt(&encrypted, ENCRYPTION_KEY).unwrap();
-            assert_eq!(&*decrypted, input);
-        }
-    }
-
-    #[test]
-    fn test_calc_encrypted_size() {
-        assert_eq!(calc_encrypted_size(0), 16);
-        assert_eq!(calc_encrypted_size(1), 16);
-        assert_eq!(calc_encrypted_size(6), 16);
-
-        assert_eq!(calc_encrypted_size(7), 24);
-        assert_eq!(calc_encrypted_size(14), 24);
-        assert_eq!(calc_encrypted_size(15), 32);
-    }
-}

src/tc_tea_internal.rs

@@ -1,63 +0,0 @@
-use super::stream_ext::StreamExt;
-
-const ROUNDS: u32 = 16;
-const DELTA: u32 = 0x9e3779b9;
-
-#[inline]
-pub fn parse_key(key: &[u8]) -> Option<[u32; 4]> {
-    if key.len() < 16 {
-        return None;
-    }
-
-    let mut k = [0u32; 4];
-    for (i, k) in k.iter_mut().enumerate() {
-        *k = key.read_u32_be(i * 4);
-    }
-    Some(k)
-}
-
-#[inline]
-/// Perform a single round of encrypting/decrypting wrapping arithmetics
-fn tc_tea_single_round_arithmetic(value: u32, sum: u32, key1: u32, key2: u32) -> u32 {
-    // ((y << 4) + k[2]) ^ (y + sum) ^ ((y >> 5) + k[3]);
-
-    value.wrapping_shl(4).wrapping_add(key1)
-        ^ sum.wrapping_add(value)
-        ^ value.wrapping_shr(5).wrapping_add(key2)
-}
-
-#[inline]
-/// Perform a single operation of TEA ECB decryption.
-pub fn ecb_decrypt(block: &mut [u8], k: &[u32; 4]) {
-    let mut y = block.read_u32_be(0);
-    let mut z = block.read_u32_be(4);
-    let mut sum = DELTA.wrapping_mul(ROUNDS);
-
-    for _ in 0..ROUNDS {
-        z = z.wrapping_sub(tc_tea_single_round_arithmetic(y, sum, k[2], k[3]));
-        y = y.wrapping_sub(tc_tea_single_round_arithmetic(z, sum, k[0], k[1]));
-
-        sum = sum.wrapping_sub(DELTA);
-    }
-
-    block.write_u32_be(0, y);
-    block.write_u32_be(4, z);
-}
-
-#[inline]
-/// Perform a single operation of TEA ECB encryption.
-pub fn ecb_encrypt(block: &mut [u8], k: &[u32; 4]) {
-    let mut y = block.read_u32_be(0);
-    let mut z = block.read_u32_be(4);
-    let mut sum = 0_u32;
-
-    for _ in 0..ROUNDS {
-        sum = sum.wrapping_add(DELTA);
-
-        y = y.wrapping_add(tc_tea_single_round_arithmetic(z, sum, k[0], k[1]));
-        z = z.wrapping_add(tc_tea_single_round_arithmetic(y, sum, k[2], k[3]));
-    }
-
-    block.write_u32_be(0, y);
-    block.write_u32_be(4, z);
-}

src/tc_tea_public.rs

@@ -1,33 +0,0 @@
-use super::tc_tea_cbc;
-
-/// Encrypts an arbitrary length sized data in the following way:
-///
-/// * PadLen  (1 byte)
-/// * Padding (variable, 0-7byte)
-/// * Salt    (2 bytes)
-/// * Body    (? bytes)
-/// * Zero    (7 bytes)
-///
-/// Returned bytes will always have a length multiple of 8.
-///
-/// PadLen/Padding/Salt are randomly bytes, with a minimum of 21 bits (3 * 8 - 3) randomness.
-///
-/// # Panics
-///
-/// If random number generator fails, it will panic.
-pub fn encrypt<T: AsRef<[u8]>, K: AsRef<[u8]>>(plaintext: T, key: K) -> Option<Box<[u8]>> {
-    tc_tea_cbc::encrypt(plaintext.as_ref(), key.as_ref())
-}
-
-/// Decrypts a byte array containing the following:
-///
-/// * PadLen  (1 byte)
-/// * Padding (variable, 0-7byte)
-/// * Salt    (2 bytes)
-/// * Body    (? bytes)
-/// * Zero    (7 bytes)
-///
-/// PadLen is taken from the last 3 bit of the first byte.
-pub fn decrypt<T: AsRef<[u8]>, K: AsRef<[u8]>>(encrypted: T, key: K) -> Option<Box<[u8]>> {
-    tc_tea_cbc::decrypt(encrypted.as_ref(), key.as_ref())
-}