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Use ciphertext buffer length for determining ciphertext length #2

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Merged
merged 1 commit into from
Aug 4, 2025
Merged

Use ciphertext buffer length for determining ciphertext length #2

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18 changes: 14 additions & 4 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -81,14 +81,14 @@ pub trait AesBlockCipher: FfiAesCipher {

/// Decrypt the contents of `ciphertext` and place the result in the `plaintext` out parameter
fn decrypt(&self, ciphertext: &[u8], plaintext: &mut [u8]) -> Result<(), Error> {
if plaintext.len() % AES_BLOCK_SIZE != 0 {
if ciphertext.len() % AES_BLOCK_SIZE != 0 {
return Err(Error::NonBlockSizeAlignedBuffer);
}
if plaintext.len() < ciphertext.len() {
return Err(Error::InsufficientBufferSize);
}

let num_blocks = plaintext.len() / AES_BLOCK_SIZE;
let num_blocks = ciphertext.len() / AES_BLOCK_SIZE;
self.ffi_decrypt(num_blocks, plaintext, ciphertext);

Ok(())
Expand Down Expand Up @@ -238,14 +238,14 @@ pub trait AesCbcBlockCipher: FfiAesCbcCipher {
}

fn decrypt(&self, ciphertext: &[u8], plaintext: &mut [u8]) -> Result<(), Error> {
if plaintext.len() % AES_BLOCK_SIZE != 0 {
if ciphertext.len() % AES_BLOCK_SIZE != 0 {
return Err(Error::NonBlockSizeAlignedBuffer);
}
if plaintext.len() < ciphertext.len() {
return Err(Error::InsufficientBufferSize);
}

let num_blocks = plaintext.len() / AES_BLOCK_SIZE;
let num_blocks = ciphertext.len() / AES_BLOCK_SIZE;
self.ffi_decrypt(num_blocks, plaintext, ciphertext);

Ok(())
Expand Down Expand Up @@ -461,6 +461,11 @@ mod test {
cipher.decrypt([0u8; 64].as_slice(), [0u8; 32].as_mut_slice()),
Err(Error::InsufficientBufferSize)
));
assert!(matches!(cipher.decrypt([0u8; 0].as_slice(), [0u8; 32768].as_mut_slice()), Ok(())));
assert!(matches!(
cipher.decrypt([0u8; crate::AES_BLOCK_SIZE].as_slice(), [0u8; 32768].as_mut_slice()),
Ok(())
));

let cipher = Aes128Cbc::new([0u8; 16].as_slice(), [0u8; 16].as_slice()).unwrap();
assert!(matches!(
Expand All @@ -475,5 +480,10 @@ mod test {
cipher.decrypt([0u8; 64].as_slice(), [0u8; 32].as_mut_slice()),
Err(Error::InsufficientBufferSize)
));
assert!(matches!(cipher.decrypt([0u8; 0].as_slice(), [0u8; 32768].as_mut_slice()), Ok(())));
assert!(matches!(
cipher.decrypt([0u8; crate::AES_BLOCK_SIZE].as_slice(), [0u8; 32768].as_mut_slice()),
Ok(())
));
}
}