sqlcrypto 0.1.0

lightweight and memory efficient sqlite/sqlcipher encryption (not secure)/decryption in pure rust
Documentation 
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use crate::*;
use crate::is_valid_decrypted_header;
use std::io::Write;
use ring::hmac::{Key, HMAC_SHA1_FOR_LEGACY_USE_ONLY, sign};
use aes_frast::aes_core::setkey_enc_k256;
use aes_frast::aes_with_operation_mode::cbc_enc;

fn read_db_header(header: &[u8]) -> Result<(usize, usize)> {
    if !(&header[..16] == b"SQLite format 3\0" && is_valid_decrypted_header(&header[16..])) {
        return Err(Error::Message("invalid db header"))
    }
    let page = get_page_size_from_database_header(header)?;
    if !(is_valid_page_size(page)) {
        return Err(Error::Message("Invalid page size"))
    }
    let reserve = get_reserved_size_from_database_header(header);
    if reserve == 0 {
        return Err(Error::Message("needs reserved space at the end of each page"))
    }
    Ok((page, reserve))
}

/// Encrypts a decrypted SQLite database, provided a key and an output stream. THIS IS NOT SECURE!
pub fn encrypt<R: AsRef<[u8]>, W: Write>(data: R, key: &[u8], output: &mut W) -> Result<()> {
    let bytes = data.as_ref();
    let (page, reserve) = read_db_header(&bytes[..100])?;
    let (key, hmac_key) = key_derive(&[1u8; 16], key); // not particularly secure salt
    let hmac_key = Key::new(HMAC_SHA1_FOR_LEGACY_USE_ONLY, hmac_key.as_slice());
    let mut scheduled_key = vec![0u32; 60];
    setkey_enc_k256(key.as_slice(), scheduled_key.as_mut_slice());
    output.write(&[1u8; 16])?;
    for i in 0..bytes.len()/page {
        let mut page = get_page(bytes, page, i + 1);
        if i == 0 {
            page = &page[16..];
        }
        let page_content = &page[..page.len()-reserve];
        let mut page_encrypted = vec![0u8; page_content.len()];
        cbc_enc(page_content, page_encrypted.as_mut_slice(), scheduled_key.as_slice(), &[1u8; 16]);
        let mut hmac_data: Vec<u8> = page_encrypted.iter().cloned().chain([1u8; 16].iter().cloned()).collect();
        hmac_data.write(&((i + 1) as i32).to_le_bytes())?;
        // TODO SIGN HMAC
        output.write(page_encrypted.as_slice())?;
        output.write(&[1u8; 16])?;
        output.write(sign(&hmac_key, hmac_data.as_slice()).as_ref())?;
        output.write(vec![1u8; reserve - 36].as_slice())?;
    }
    Ok(())
}