aries-askar 0.4.6

use std::{mem, ptr};

use crate::{crypto::buffer::SecretBytes, kms::Encrypted};

#[no_mangle]
pub extern "C" fn askar_buffer_free(buffer: SecretBuffer) {
    ffi_support::abort_on_panic::with_abort_on_panic(|| {
        drop(buffer.destroy_into_secret());
    })
}

// Structure consistent with ffi_support ByteBuffer, but zeroized on drop
#[derive(Debug)]
#[repr(C)]
pub struct SecretBuffer {
    // must be >= 0, signed int was chosen for compatibility
    len: i64,
    // nullable
    data: *mut u8,
}

impl Default for SecretBuffer {
    fn default() -> Self {
        Self {
            len: 0,
            data: ptr::null_mut(),
        }
    }
}

impl SecretBuffer {
    pub fn from_secret(buffer: impl Into<SecretBytes>) -> Self {
        let mut buf = buffer.into();
        buf.shrink_to_fit();
        debug_assert_eq!(buf.len(), buf.capacity());
        let mut buf = mem::ManuallyDrop::new(buf.into_vec());
        let len = i64::try_from(buf.len()).expect("secret length exceeds i64::MAX");
        let data = buf.as_mut_ptr();
        Self { len, data }
    }

    pub fn destroy_into_secret(self) -> SecretBytes {
        if self.data.is_null() {
            SecretBytes::default()
        } else {
            if self.len < 0 {
                panic!("found negative length for secret buffer");
            }
            let len = self.len as usize;
            SecretBytes::from(unsafe { Vec::from_raw_parts(self.data, len, len) })
        }
    }
}

// A combined ciphertext and tag value
#[derive(Debug)]
#[repr(C)]
pub struct EncryptedBuffer {
    buffer: SecretBuffer,
    tag_pos: i64,
    nonce_pos: i64,
}

impl EncryptedBuffer {
    pub fn from_encrypted(enc: Encrypted) -> Self {
        let tag_pos = i64::try_from(enc.tag_pos).expect("ciphertext length exceeds i64::MAX");
        let nonce_pos = i64::try_from(enc.nonce_pos).expect("ciphertext length exceeds i64::MAX");
        Self {
            buffer: SecretBuffer::from_secret(enc.buffer),
            tag_pos,
            nonce_pos,
        }
    }
}