feat: aes gcm stream works

src/lib.rs

@@ -0,0 +1,212 @@
+use aes::Aes128;
+use aes::cipher::{Block, BlockEncrypt, KeyInit};
+use aes::cipher::generic_array::GenericArray;
+
+pub struct Aes128GcmStream {
+    crypto: Aes128,
+    message_buffer: Vec<u8>,
+    integrality_buffer: Vec<u8>,
+    ghash_key: u128,
+    ghash_val: u128,
+    init_nonce: u128,
+    encryption_nonce: u128,
+    adata_len: usize,
+    message_len: usize,
+}
+
+impl Aes128GcmStream {
+    pub fn new(key: [u8; 16]) -> Self {
+        let key = GenericArray::from(key);
+        let aes = Aes128::new(&key);
+
+        Self {
+            crypto: aes,
+            message_buffer: vec![],
+            integrality_buffer: vec![],
+            ghash_key: 0,
+            ghash_val: 0,
+            init_nonce: 0,
+            encryption_nonce: 0,
+            adata_len: 0,
+            message_len: 0,
+        }
+    }
+
+    pub fn init_nonce(&mut self, nonce: &[u8]) {
+        let (ghash_key, normalized_nonce) = self.normalize_nonce(nonce);
+        self.ghash_key = ghash_key;
+        self.init_nonce = normalized_nonce;
+        self.encryption_nonce = normalized_nonce;
+    }
+
+    pub fn init_adata(&mut self, adata: &[u8]) {
+        self.integrality_buffer.extend_from_slice(adata);
+        self.adata_len += adata.len();
+
+        let adata_bit_len = self.adata_len * 8;
+        let v = 128 * ((adata_bit_len + 128 - 1) / 128) - adata_bit_len;
+        self.integrality_buffer.extend_from_slice(&vec![0x00; v / 8]);
+    }
+
+    pub fn next(&mut self, bytes: &[u8]) -> Vec<u8> {
+        self.message_buffer.extend_from_slice(bytes);
+        let message_buffer_slice = self.message_buffer.as_slice();
+        let message_buffer_len = message_buffer_slice.len();
+        if message_buffer_len < 16 {
+            return vec![];
+        }
+        let blocks_count = message_buffer_len / 16;
+        let mut encrypted_message = vec![];
+        for i in 0..blocks_count {
+            self.encryption_nonce = inc_32(self.encryption_nonce);
+            let mut ctr = self.encryption_nonce.to_be_bytes();
+            let block = Block::<Aes128>::from_mut_slice(&mut ctr);
+            self.crypto.encrypt_block(block);
+            let chunk = &message_buffer_slice[i * 16..(i + 1) * 16];
+            let y = u8to128(chunk) ^ u8to128(&block.as_slice());
+            encrypted_message.extend_from_slice(&y.to_be_bytes());
+        }
+        self.message_buffer = message_buffer_slice[blocks_count * 16..].to_vec();
+        self.integrality_buffer.extend_from_slice(&encrypted_message);
+        self.message_len += encrypted_message.len();
+
+        self.update_integrality_buffer();
+
+        encrypted_message
+    }
+
+    pub fn finalize(&mut self) -> (Vec<u8>, Vec<u8>) {
+        let mut encrypted_message = vec![];
+        if !self.message_buffer.is_empty() {
+            // last block and this block len is less than 128 bits
+            self.encryption_nonce = inc_32(self.encryption_nonce);
+            let mut ctr = self.encryption_nonce.to_be_bytes();
+            let block = Block::<Aes128>::from_mut_slice(&mut ctr);
+            self.crypto.encrypt_block(block);
+
+            let chunk = self.message_buffer.as_slice();
+            let msb = msb_s(chunk.len() * 8, block.as_slice());
+            let y = u8to128(chunk) ^ u8to128(&msb);
+            encrypted_message.extend_from_slice(&y.to_be_bytes()[16 - chunk.len()..16]);
+            self.integrality_buffer.extend_from_slice(&encrypted_message);
+            self.message_len += encrypted_message.len();
+        }
+        let adata_bit_len = self.adata_len * 8;
+        let message_bit_len = self.message_len * 8;
+        let u = 128 * ((message_bit_len + 128 - 1) / 128) - message_bit_len;
+        self.integrality_buffer.extend_from_slice(&vec![0x00; u / 8]);
+        self.integrality_buffer.extend_from_slice(&(adata_bit_len as u64).to_be_bytes());
+        self.integrality_buffer.extend_from_slice(&(message_bit_len as u64).to_be_bytes());
+
+        self.update_integrality_buffer();
+        assert!(self.integrality_buffer.is_empty());
+
+        let tag = self.calculate_tag();
+
+        (encrypted_message, tag)
+    }
+
+    fn calculate_tag(&mut self) -> Vec<u8> {
+        let mut bs = self.init_nonce.to_be_bytes().clone();
+        let block = Block::<Aes128>::from_mut_slice(&mut bs);
+        self.crypto.encrypt_block(block);
+        let tag_trunk = self.ghash_val.to_be_bytes();
+        let y = u8to128(&tag_trunk) ^ u8to128(&block.as_slice());
+        y.to_be_bytes().to_vec()
+    }
+
+    fn update_integrality_buffer(&mut self) {
+        let integrality_buffer_slice = self.integrality_buffer.as_slice();
+        let integrality_buffer_slice_len = integrality_buffer_slice.len();
+        if integrality_buffer_slice_len >= 16 {
+            let i_blocks_count = integrality_buffer_slice_len / 16;
+            for i in 0..i_blocks_count {
+                let buf = &integrality_buffer_slice[i * 16..(i + 1) * 16];
+                self.ghash_val = gmul_128(self.ghash_val ^ u8to128(buf), self.ghash_key)
+            }
+            self.integrality_buffer = integrality_buffer_slice[i_blocks_count * 16..].to_vec();
+        }
+    }
+
+    fn ghash_key(&mut self) -> u128 {
+        let mut block = [0u8; 16];
+        let block = Block::<Aes128>::from_mut_slice(&mut block);
+        self.crypto.encrypt_block(block);
+        u8to128(&block.as_slice())
+    }
+
+    fn normalize_nonce(&mut self, nonce_bytes: &[u8]) -> (u128, u128) {
+        let ghash_key = self.ghash_key();
+        let nonce = u8to128(nonce_bytes);
+        let normalized_nonce = match nonce_bytes.len() == 12 {
+            true => {
+                nonce << 32 | 0x00000001
+            }
+            false => {
+                let mut iv_padding = vec![];
+                // s = 128[len(iv) / 128] - len(iv)
+                let s = 128 * (((nonce_bytes.len() * 8) + 128 - 1) / 128) - (nonce_bytes.len() * 8);
+                iv_padding.push(nonce << s);
+                iv_padding.push((nonce_bytes.len() * 8) as u128);
+                ghash(ghash_key, &iv_padding)
+            }
+        };
+        (ghash_key, normalized_nonce)
+    }
+}
+
+
+// R = 11100001 || 0(120)
+const R: u128 = 0b11100001 << 120;
+
+fn gmul_128(x: u128, y: u128) -> u128 {
+    let mut z = 0u128;
+    let mut v = y;
+    for i in (0..128).rev() {
+        let xi = (x >> i) & 1;
+        if xi != 0 {
+            z ^= v;
+        }
+        v = match v & 1 == 0 {
+            true => { v >> 1 }
+            false => { (v >> 1) ^ R }
+        };
+    }
+    z
+}
+
+fn ghash(key: u128, messages: &[u128]) -> u128 {
+    let mut y = 0u128;
+    for i in 0..messages.len() {
+        let yi = gmul_128(y ^ messages[i], key);
+        y = yi;
+    }
+    y
+}
+
+fn u8to128(bytes: &[u8]) -> u128 {
+    bytes.iter().rev().enumerate().fold(0, |acc, (i, &byte)| {
+        acc | (byte as u128) << (i * 8)
+    })
+}
+
+fn msb_s(s: usize, bytes: &[u8]) -> Vec<u8> {
+    let mut result = vec![];
+    let n = s / 8;
+    let remain = s % 8;
+    for i in 0..n {
+        result.push(bytes[i]);
+    }
+    if remain > 0 {
+        result.push(bytes[n] >> (8 - remain));
+    }
+    result
+}
+
+// incs(X)=MSBlen(X)-s(X) || [int(LSBs(X))+1 mod 2^s]s
+fn inc_32(bits: u128) -> u128 {
+    let msb = bits >> 32;
+    let mut lsb = (bits & 0xffffffff) as u32;
+    lsb = lsb.wrapping_add(1);
+    msb << 32 | lsb as u128
+}