1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328
const BASE64_DIGEST_LEN: usize = 44;
use async_session::{
base64,
hmac::{Hmac, Mac, NewMac},
sha2::Sha256,
Session, SessionStore,
};
use std::{
fmt::{self, Debug, Formatter},
iter,
time::{Duration, SystemTime},
};
use trillium::{async_trait, Conn, Handler};
use trillium_cookies::{
cookie::{Cookie, Key, SameSite},
CookiesConnExt,
};
/**
# Handler to enable sessions.
See crate-level docs for an overview of this crate's approach to
sessions and security.
*/
pub struct SessionHandler<Store> {
store: Store,
cookie_path: String,
cookie_name: String,
cookie_domain: Option<String>,
session_ttl: Option<Duration>,
save_unchanged: bool,
same_site_policy: SameSite,
key: Key,
older_keys: Vec<Key>,
}
impl<Store: SessionStore> Debug for SessionHandler<Store> {
fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
f.debug_struct("SessionHandler")
.field("store", &self.store)
.field("cookie_path", &self.cookie_path)
.field("cookie_name", &self.cookie_name)
.field("cookie_domain", &self.cookie_domain)
.field("session_ttl", &self.session_ttl)
.field("save_unchanged", &self.save_unchanged)
.field("same_site_policy", &self.same_site_policy)
.field("key", &"<<secret>>")
.field("older_keys", &"<<secret>>")
.finish()
}
}
impl<Store: SessionStore> SessionHandler<Store> {
/**
Constructs a SessionHandler from the given
[`async_session::SessionStore`] and secret. The `secret` MUST be
at least 32 bytes long, and MUST be cryptographically random to be
secure. It is recommended to retrieve this at runtime from the
environment instead of compiling it into your application.
# Panics
SessionHandler::new will panic if the secret is fewer than
32 bytes.
# Defaults
The defaults for SessionHandler are:
* cookie path: "/"
* cookie name: "trillium.sid"
* session ttl: one day
* same site: strict
* save unchanged: enabled
* older secrets: none
# Customization
Although the above defaults are appropriate for most applications,
they can be overridden. Please be careful changing these settings,
as they can weaken your application's security:
```rust
# use std::time::Duration;
# use trillium_sessions::{SessionHandler, MemoryStore};
# use trillium_cookies::{CookiesHandler, cookie::SameSite};
# std::env::set_var("TRILLIUM_SESSION_SECRETS", "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb");
// this logic will be unique to your deployment
let secrets_var = std::env::var("TRILLIUM_SESSION_SECRETS").unwrap();
let session_secrets = secrets_var.split(' ').collect::<Vec<_>>();
let handler = (
CookiesHandler::new(),
SessionHandler::new(MemoryStore::new(), session_secrets[0])
.with_cookie_name("custom.cookie.name")
.with_cookie_path("/some/path")
.with_cookie_domain("trillium.rs")
.with_same_site_policy(SameSite::Strict)
.with_session_ttl(Some(Duration::from_secs(1)))
.with_older_secrets(&session_secrets[1..])
.without_save_unchanged()
);
```
*/
pub fn new(store: Store, secret: impl AsRef<[u8]>) -> Self {
Self {
store,
save_unchanged: true,
cookie_path: "/".into(),
cookie_name: "trillium.sid".into(),
cookie_domain: None,
same_site_policy: SameSite::Lax,
session_ttl: Some(Duration::from_secs(24 * 60 * 60)),
key: Key::derive_from(secret.as_ref()),
older_keys: vec![],
}
}
/// Sets a cookie path for this session handler.
/// The default for this value is "/"
pub fn with_cookie_path(mut self, cookie_path: impl AsRef<str>) -> Self {
cookie_path.as_ref().clone_into(&mut self.cookie_path);
self
}
/// Sets a session ttl. This will be used both for the cookie
/// expiry and also for the session-internal expiry.
///
/// The default for this value is one day. Set this to None to not
/// set a cookie or session expiry. This is not recommended.
pub fn with_session_ttl(mut self, session_ttl: Option<Duration>) -> Self {
self.session_ttl = session_ttl;
self
}
/// Sets the name of the cookie that the session is stored with or in.
///
/// If you are running multiple trillium applications on the same
/// domain, you will need different values for each
/// application. The default value is "trillium.sid"
pub fn with_cookie_name(mut self, cookie_name: impl AsRef<str>) -> Self {
cookie_name.as_ref().clone_into(&mut self.cookie_name);
self
}
/// Disables the `save_unchanged` setting. When `save_unchanged`
/// is enabled, a session will cookie will always be set. With
/// `save_unchanged` disabled, the session data must be modified
/// from the `Default` value in order for it to save. If a session
/// already exists and its data unmodified in the course of a
/// request, the session will only be persisted if
/// `save_unchanged` is enabled.
pub fn without_save_unchanged(mut self) -> Self {
self.save_unchanged = false;
self
}
/// Sets the same site policy for the session cookie. Defaults to
/// SameSite::Strict. See [incrementally better
/// cookies](https://tools.ietf.org/html/draft-west-cookie-incrementalism-01)
/// for more information about this setting
pub fn with_same_site_policy(mut self, policy: SameSite) -> Self {
self.same_site_policy = policy;
self
}
/// Sets the domain of the cookie.
pub fn with_cookie_domain(mut self, cookie_domain: impl AsRef<str>) -> Self {
self.cookie_domain = Some(cookie_domain.as_ref().to_owned());
self
}
/// Sets optional older signing keys that will not be used to sign
/// cookies, but can be used to validate previously signed
/// cookies.
pub fn with_older_secrets(mut self, secrets: &[impl AsRef<[u8]>]) -> Self {
self.older_keys = secrets
.iter()
.map(AsRef::as_ref)
.map(Key::derive_from)
.collect();
self
}
//--- methods below here are private ---
async fn load_or_create(&self, cookie_value: Option<&str>) -> Session {
let session = match cookie_value {
Some(cookie_value) => self
.store
.load_session(String::from(cookie_value))
.await
.ok()
.flatten(),
None => None,
};
session
.and_then(|session| session.validate())
.unwrap_or_default()
}
fn build_cookie(&self, secure: bool, cookie_value: String) -> Cookie<'static> {
let mut cookie: Cookie<'static> = Cookie::build((self.cookie_name.clone(), cookie_value))
.http_only(true)
.same_site(self.same_site_policy)
.secure(secure)
.path(self.cookie_path.clone())
.into();
if let Some(ttl) = self.session_ttl {
cookie.set_expires(Some((SystemTime::now() + ttl).into()));
}
if let Some(cookie_domain) = self.cookie_domain.clone() {
cookie.set_domain(cookie_domain)
}
self.sign_cookie(&mut cookie);
cookie
}
// the following is reused verbatim from
// https://github.com/SergioBenitez/cookie-rs/blob/master/src/secure/signed.rs#L37-46
/// Signs the cookie's value providing integrity and authenticity.
fn sign_cookie(&self, cookie: &mut Cookie<'_>) {
// Compute HMAC-SHA256 of the cookie's value.
let mut mac = Hmac::<Sha256>::new_from_slice(self.key.signing()).expect("good key");
mac.update(cookie.value().as_bytes());
// Cookie's new value is [MAC | original-value].
let mut new_value = base64::encode(mac.finalize().into_bytes());
new_value.push_str(cookie.value());
cookie.set_value(new_value);
}
// the following is reused verbatim from
// https://github.com/SergioBenitez/cookie-rs/blob/master/src/secure/signed.rs#L51-L66
/// Given a signed value `str` where the signature is prepended to `value`,
/// verifies the signed value and returns it. If there's a problem, returns
/// an `Err` with a string describing the issue.
fn verify_signature<'a>(&self, cookie_value: &'a str) -> Option<&'a str> {
if cookie_value.len() < BASE64_DIGEST_LEN {
log::trace!("length of value is <= BASE64_DIGEST_LEN");
return None;
}
// Split [MAC | original-value] into its two parts.
let (digest_str, value) = cookie_value.split_at(BASE64_DIGEST_LEN);
let digest = match base64::decode(digest_str) {
Ok(digest) => digest,
Err(_) => {
log::trace!("bad base64 digest");
return None;
}
};
iter::once(&self.key)
.chain(self.older_keys.iter())
.find_map(|key| {
let mut mac = Hmac::<Sha256>::new_from_slice(key.signing()).expect("good key");
mac.update(value.as_bytes());
mac.verify(&digest).ok()
})
.map(|_| value)
}
}
#[async_trait]
impl<Store: SessionStore> Handler for SessionHandler<Store> {
async fn run(&self, mut conn: Conn) -> Conn {
let session = conn.take_state::<Session>();
let cookie_value = conn
.cookies()
.get(&self.cookie_name)
.and_then(|cookie| self.verify_signature(cookie.value()));
let mut session = match session {
Some(session) => session,
None => self.load_or_create(cookie_value).await,
};
if let Some(ttl) = self.session_ttl {
session.expire_in(ttl);
}
conn.with_state(session)
}
async fn before_send(&self, mut conn: Conn) -> Conn {
if let Some(session) = conn.take_state::<Session>() {
let session_to_keep = session.clone();
let secure = conn.is_secure();
if session.is_destroyed() {
self.store.destroy_session(session).await.ok();
conn.cookies_mut()
.remove(Cookie::from(self.cookie_name.clone()));
} else if self.save_unchanged || session.data_changed() {
match self.store.store_session(session).await {
Ok(Some(cookie_value)) => {
conn.cookies_mut()
.add(self.build_cookie(secure, cookie_value));
}
Ok(None) => {}
Err(e) => {
log::error!("could not store session:\n\n{e}")
}
}
}
conn.with_state(session_to_keep)
} else {
conn
}
}
}
/// Alias for [`SessionHandler::new`]
pub fn sessions<Store>(store: Store, secret: impl AsRef<[u8]>) -> SessionHandler<Store>
where
Store: SessionStore,
{
SessionHandler::new(store, secret)
}