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use core::convert::TryInto;
use iso7816::Status;
// use iso7816::response::Result;
use trussed::{
postcard_deserialize, postcard_serialize_bytes,
syscall, try_syscall,
types::{KeyId, Location, PathBuf},
};
#[derive(Clone, Debug, Default, Eq, PartialEq)]
pub struct State {
// at startup, trussed is not callable yet.
// moreover, when worst comes to worst, filesystems are not available
// persistent: Option<Persistent>,
pub runtime: Runtime,
// temporary "state", to be removed again
// pub hack: Hack,
// trussed: RefCell<Trussed<S>>,
}
#[derive(Clone, Debug, Eq, PartialEq, serde::Deserialize, serde::Serialize)]
pub struct Persistent {
pub salt: [u8; 8],
/// This is the user's password, passed through PBKDF-HMAC-SHA1.
/// It is used for authorization using challenge HMAC-SHA1'ing.
pub authorization_key: Option<KeyId>,
}
#[derive(Clone, Debug, Default, Eq, PartialEq)]
pub struct Runtime {
/// Not actually used - need to figure out "many credentials" case
pub previously: Option<CommandState>,
/// This gets rotated regularly, so someone sniffing on the bus can't replay.
/// There is a small window between a legitimate client authenticating,
/// and its next command that needs such authentication.
pub challenge: [u8; 8],
/// Gets set after a successful VALIDATE call,
/// good for use right after (e.g. to set/change/remove password),
/// and cleared thereafter.
pub client_authorized: bool,
/// For book-keeping purposes, set client_authorized / prevents it from being cleared before
/// returning control to caller of the app
pub client_newly_authorized: bool,
}
impl Runtime {
pub fn reset(&mut self) {
*self = Self::default();
}
}
impl Persistent {
pub fn password_set(&self) -> bool {
self.authorization_key.is_some()
}
}
impl State {
const FILENAME: &'static str = "state.bin";
// pub fn persistent<E, T>(
// &mut self,
// trussed: &mut T,
// f: impl FnOnce(&mut T, &mut Persistent) -> core::result::Result<(), E>
// )
// -> Result<(), E>
pub fn try_persistent<T>(
&mut self,
trussed: &mut T,
f: impl FnOnce(&mut T, &mut Persistent) -> Result<(), Status>
)
-> Result<(), Status>
where
T: trussed::Client,
{
// 1. If there is serialized, persistent state (i.e., the try_syscall! to `read_file` does
// not fail), then assume it is valid and deserialize it. If the reading fails, assume
// that this is the first run, and set defaults.
//
// NB: This is an attack vector. If the state can be corrupted, this clears the password.
// Consider resetting the device in this situation
let mut state: Persistent = try_syscall!(trussed.read_file(Location::Internal, PathBuf::from(Self::FILENAME)))
.map(|response| postcard_deserialize(&response.data).unwrap())
.unwrap_or_else(|_| {
let salt: [u8; 8] = syscall!(trussed.random_bytes(8)).bytes.as_ref().try_into().unwrap();
Persistent { salt, authorization_key: None }
});
// 2. Let the app read or modify the state
let result = f(trussed, &mut state);
// 3. Always write it back
syscall!(trussed.write_file(
Location::Internal,
PathBuf::from(Self::FILENAME),
postcard_serialize_bytes(&state).unwrap(),
None,
));
// 4. Return whatever
result
}
pub fn persistent<T, X>(
&mut self,
trussed: &mut T,
f: impl FnOnce(&mut T, &mut Persistent) -> X
)
-> X
where
T: trussed::Client,
{
// 1. If there is serialized, persistent state (i.e., the try_syscall! to `read_file` does
// not fail), then assume it is valid and deserialize it. If the reading fails, assume
// that this is the first run, and set defaults.
//
// NB: This is an attack vector. If the state can be corrupted, this clears the password.
// Consider resetting the device in this situation
let mut state: Persistent = try_syscall!(trussed.read_file(Location::Internal, PathBuf::from(Self::FILENAME)))
.map(|response| postcard_deserialize(&response.data).unwrap())
.unwrap_or_else(|_| {
let salt: [u8; 8] = syscall!(trussed.random_bytes(8)).bytes.as_ref().try_into().unwrap();
Persistent { salt, authorization_key: None }
});
// 2. Let the app read or modify the state
let x = f(trussed, &mut state);
// 3. Always write it back
syscall!(trussed.write_file(
Location::Internal,
PathBuf::from(Self::FILENAME),
postcard_serialize_bytes(&state).unwrap(),
None,
));
x
}
}
#[derive(Clone, Debug, Eq, PartialEq)]
pub enum CommandState {
ListCredentials(usize),
}