chatmail-core/src/pgp.rs

use std::collections::HashSet;
use std::convert::TryInto;
use std::io::Cursor;
use std::ptr;

use libc::{strchr, strlen, strncmp, strspn, strstr};
use pgp::composed::{
    Deserializable, KeyType as PgpKeyType, Message, SecretKeyParamsBuilder, SignedPublicKey,
    SignedSecretKey, SubkeyParamsBuilder,
};
use pgp::crypto::{HashAlgorithm, SymmetricKeyAlgorithm};
use pgp::types::{CompressionAlgorithm, KeyTrait, SecretKeyTrait, StringToKey};
use rand::thread_rng;

use crate::dc_tools::*;
use crate::error::Error;
use crate::key::*;
use crate::keyring::*;

pub unsafe fn dc_split_armored_data(
    buf: *mut libc::c_char,
    ret_headerline: *mut *const libc::c_char,
    ret_setupcodebegin: *mut *const libc::c_char,
    ret_preferencrypt: *mut *const libc::c_char,
    ret_base64: *mut *const libc::c_char,
) -> bool {
    let mut success = false;
    let mut line_chars: libc::size_t = 0;
    let mut line: *mut libc::c_char = buf;
    let mut p1: *mut libc::c_char = buf;
    let mut p2: *mut libc::c_char;
    let mut headerline: *mut libc::c_char = ptr::null_mut();
    let mut base64: *mut libc::c_char = ptr::null_mut();
    if !ret_headerline.is_null() {
        *ret_headerline = ptr::null()
    }
    if !ret_setupcodebegin.is_null() {
        *ret_setupcodebegin = ptr::null_mut();
    }
    if !ret_preferencrypt.is_null() {
        *ret_preferencrypt = ptr::null();
    }
    if !ret_base64.is_null() {
        *ret_base64 = ptr::null();
    }
    if !(buf.is_null() || ret_headerline.is_null()) {
        dc_remove_cr_chars(buf);
        while 0 != *p1 {
            if *p1 as libc::c_int == '\n' as i32 {
                *line.offset(line_chars as isize) = 0i32 as libc::c_char;
                if headerline.is_null() {
                    dc_trim(line);
                    if strncmp(
                        line,
                        b"-----BEGIN \x00" as *const u8 as *const libc::c_char,
                        1,
                    ) == 0i32
                        && strncmp(
                            &mut *line.offset(strlen(line).wrapping_sub(5) as isize),
                            b"-----\x00" as *const u8 as *const libc::c_char,
                            5,
                        ) == 0i32
                    {
                        headerline = line;
                        if !ret_headerline.is_null() {
                            *ret_headerline = headerline
                        }
                    }
                } else if strspn(line, b"\t\r\n \x00" as *const u8 as *const libc::c_char)
                    == strlen(line)
                {
                    base64 = p1.offset(1isize);
                    break;
                } else {
                    p2 = strchr(line, ':' as i32);
                    if p2.is_null() {
                        *line.offset(line_chars as isize) = '\n' as i32 as libc::c_char;
                        base64 = line;
                        break;
                    } else {
                        *p2 = 0i32 as libc::c_char;
                        dc_trim(line);
                        if strcasecmp(
                            line,
                            b"Passphrase-Begin\x00" as *const u8 as *const libc::c_char,
                        ) == 0i32
                        {
                            p2 = p2.offset(1isize);
                            dc_trim(p2);
                            if !ret_setupcodebegin.is_null() {
                                *ret_setupcodebegin = p2
                            }
                        } else if strcasecmp(
                            line,
                            b"Autocrypt-Prefer-Encrypt\x00" as *const u8 as *const libc::c_char,
                        ) == 0i32
                        {
                            p2 = p2.offset(1isize);
                            dc_trim(p2);
                            if !ret_preferencrypt.is_null() {
                                *ret_preferencrypt = p2
                            }
                        }
                    }
                }
                p1 = p1.offset(1isize);
                line = p1;
                line_chars = 0;
            } else {
                p1 = p1.offset(1isize);
                line_chars = line_chars.wrapping_add(1)
            }
        }
        if !(headerline.is_null() || base64.is_null()) {
            /* now, line points to beginning of base64 data, search end */
            /*the trailing space makes sure, this is not a normal base64 sequence*/
            p1 = strstr(base64, b"-----END \x00" as *const u8 as *const libc::c_char);
            if !(p1.is_null()
                || strncmp(
                    p1.offset(9isize),
                    headerline.offset(11isize),
                    strlen(headerline.offset(11isize)),
                ) != 0i32)
            {
                *p1 = 0i32 as libc::c_char;
                dc_trim(base64);
                if !ret_base64.is_null() {
                    *ret_base64 = base64
                }
                success = true;
            }
        }
    }

    success
}

/// Create a new key pair.
pub fn dc_pgp_create_keypair(addr: impl AsRef<str>) -> Option<(Key, Key)> {
    let user_id = format!("<{}>", addr.as_ref());

    let key_params = SecretKeyParamsBuilder::default()
        .key_type(PgpKeyType::Rsa(2048))
        .can_create_certificates(true)
        .can_sign(true)
        .primary_user_id(user_id)
        .passphrase(None)
        .preferred_symmetric_algorithms(smallvec![
            SymmetricKeyAlgorithm::AES256,
            SymmetricKeyAlgorithm::AES192,
            SymmetricKeyAlgorithm::AES128,
        ])
        .preferred_hash_algorithms(smallvec![
            HashAlgorithm::SHA2_256,
            HashAlgorithm::SHA2_384,
            HashAlgorithm::SHA2_512,
            HashAlgorithm::SHA2_224,
            HashAlgorithm::SHA1,
        ])
        .preferred_compression_algorithms(smallvec![
            CompressionAlgorithm::ZLIB,
            CompressionAlgorithm::ZIP,
        ])
        .subkey(
            SubkeyParamsBuilder::default()
                .key_type(PgpKeyType::Rsa(2048))
                .can_encrypt(true)
                .passphrase(None)
                .build()
                .unwrap(),
        )
        .build()
        .expect("invalid key params");

    let key = key_params.generate().expect("invalid params");
    let private_key = key.sign(|| "".into()).expect("failed to sign secret key");

    let public_key = private_key.public_key();
    let public_key = public_key
        .sign(&private_key, || "".into())
        .expect("failed to sign public key");

    private_key.verify().expect("invalid private key generated");
    public_key.verify().expect("invalid public key generated");

    Some((Key::Public(public_key), Key::Secret(private_key)))
}

pub fn dc_pgp_pk_encrypt(
    plain: &[u8],
    public_keys_for_encryption: &Keyring,
    private_key_for_signing: Option<&Key>,
) -> Result<String, Error> {
    let lit_msg = Message::new_literal_bytes("", plain);
    let pkeys: Vec<&SignedPublicKey> = public_keys_for_encryption
        .keys()
        .into_iter()
        .filter_map(|key| {
            let k: &Key = &key;
            k.try_into().ok()
        })
        .collect();

    let mut rng = thread_rng();

    // TODO: measure time
    let encrypted_msg = if let Some(private_key) = private_key_for_signing {
        let skey: &SignedSecretKey = private_key
            .try_into()
            .map_err(|_| format_err!("Invalid private key"))?;

        lit_msg
            .sign(skey, || "".into(), Default::default())
            .and_then(|msg| msg.compress(CompressionAlgorithm::ZLIB))
            .and_then(|msg| msg.encrypt_to_keys(&mut rng, Default::default(), &pkeys))
    } else {
        lit_msg.encrypt_to_keys(&mut rng, Default::default(), &pkeys)
    };

    let msg = encrypted_msg?;
    let encoded_msg = msg.to_armored_string(None)?;

    Ok(encoded_msg)
}

pub fn dc_pgp_pk_decrypt(
    ctext: &[u8],
    private_keys_for_decryption: &Keyring,
    public_keys_for_validation: &Keyring,
    ret_signature_fingerprints: Option<&mut HashSet<String>>,
) -> Result<Vec<u8>, Error> {
    let (msg, _) = Message::from_armor_single(Cursor::new(ctext))?;
    let skeys: Vec<&SignedSecretKey> = private_keys_for_decryption
        .keys()
        .iter()
        .filter_map(|key| {
            let k: &Key = &key;
            k.try_into().ok()
        })
        .collect();

    let (decryptor, _) = msg.decrypt(|| "".into(), || "".into(), &skeys[..])?;
    let msgs = decryptor.collect::<Result<Vec<_>, _>>()?;
    ensure!(!msgs.is_empty(), "No valid messages found");

    let dec_msg = &msgs[0];

    if let Some(ret_signature_fingerprints) = ret_signature_fingerprints {
        if !public_keys_for_validation.keys().is_empty() {
            let pkeys: Vec<&SignedPublicKey> = public_keys_for_validation
                .keys()
                .iter()
                .filter_map(|key| {
                    let k: &Key = &key;
                    k.try_into().ok()
                })
                .collect();

            for pkey in &pkeys {
                if dec_msg.verify(&pkey.primary_key).is_ok() {
                    let fp = hex::encode_upper(pkey.fingerprint());
                    ret_signature_fingerprints.insert(fp);
                }
            }
        }
    }

    match dec_msg.get_content()? {
        Some(content) => Ok(content),
        None => bail!("Decrypted message is empty"),
    }
}

/// Symmetric encryption.
pub fn dc_pgp_symm_encrypt(passphrase: &str, plain: &[u8]) -> Result<String, Error> {
    let mut rng = thread_rng();
    let lit_msg = Message::new_literal_bytes("", plain);

    let s2k = StringToKey::new_default(&mut rng);
    let msg =
        lit_msg.encrypt_with_password(&mut rng, s2k, Default::default(), || passphrase.into())?;

    let encoded_msg = msg.to_armored_string(None)?;

    Ok(encoded_msg)
}

/// Symmetric decryption.
pub fn dc_pgp_symm_decrypt(passphrase: &str, ctext: &[u8]) -> Result<Vec<u8>, Error> {
    let enc_msg = Message::from_bytes(Cursor::new(ctext))?;
    let decryptor = enc_msg.decrypt_with_password(|| passphrase.into())?;

    let msgs = decryptor.collect::<Result<Vec<_>, _>>()?;
    ensure!(!msgs.is_empty(), "No valid messages found");

    match msgs[0].get_content()? {
        Some(content) => Ok(content),
        None => bail!("Decrypted message is empty"),
    }
}