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use std::{iter, slice, vec};
use thiserror::Error;
use crate::Scope;
/// Indicates the requester held insufficient scope to be granted access
/// to a controlled resource
#[derive(Copy, Clone, Debug, Hash, Eq, PartialEq, Error)]
#[error("insufficient scope")]
pub struct InsufficientScope;
/// An access policy based on OAuth2 scopes
///
/// This access policy takes the form of alternatives around required scopes.
/// This policy will allow access if any of the alternatives would allow
/// access. If the policy contains no alternatives, the default effect is to
/// deny access.
///
/// # Examples
///
/// ## Deny all requests
/// ```
/// use aliri_traits::Policy;
/// use aliri_oauth2::{Scope, ScopePolicy};
///
/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
/// let policy = ScopePolicy::deny_all();
///
/// let request = Scope::single("admin".parse()?);
/// assert!(policy.evaluate(&request).is_err());
/// # Ok(())
/// # }
/// ```
///
/// ## Allow any request
/// ```
/// use aliri_traits::Policy;
/// use aliri_oauth2::{Scope, ScopePolicy};
///
/// let policy = ScopePolicy::allow_any();
///
/// let request = Scope::empty();
/// assert!(policy.evaluate(&request).is_ok());
/// ```
///
/// ## Allow requests with a single scope
/// ```
/// use aliri_traits::Policy;
/// use aliri_oauth2::{Scope, ScopePolicy};
///
/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
/// let policy = ScopePolicy::allow_one(
/// Scope::single("admin".parse()?)
/// );
///
/// let request = Scope::from_scope_tokens(vec![
/// "admin".parse()?,
/// "user".parse()?,
/// ]);
/// assert!(policy.evaluate(&request).is_ok());
///
/// let user_request = Scope::from_scope_tokens(vec![
/// "user".parse()?,
/// ]);
/// assert!(policy.evaluate(&user_request).is_err());
/// # Ok(())
/// # }
/// ```
///
/// ## Allow requests with multiple potential sets of scopes
/// ```
/// use aliri_traits::Policy;
/// use aliri_oauth2::{Scope, ScopePolicy};
///
/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
/// let mut policy = ScopePolicy::deny_all();
/// policy.allow(Scope::single("admin".parse()?));
/// policy.allow(Scope::from_scope_tokens(vec![
/// "special".parse()?,
/// "user".parse()?,
/// ]));
///
/// let admin_request = Scope::from_scope_tokens(vec![
/// "admin".parse()?,
/// ]);
/// assert!(policy.evaluate(&admin_request).is_ok());
///
/// let user_request = Scope::from_scope_tokens(vec![
/// "user".parse()?,
/// ]);
/// assert!(policy.evaluate(&user_request).is_err());
///
/// let special_user_request = Scope::from_scope_tokens(vec![
/// "special".parse()?,
/// "user".parse()?,
/// ]);
/// assert!(policy.evaluate(&special_user_request).is_ok());
/// # Ok(())
/// # }
/// ```
#[derive(Clone, Debug, PartialEq, Eq)]
#[must_use]
pub struct ScopePolicy {
inner: ScopePolicyInner,
}
#[derive(Clone, Debug, PartialEq, Eq)]
enum ScopePolicyInner {
DenyAll,
AllowAny,
AllowOne(Scope),
AllowMany(Vec<Scope>),
}
impl Default for ScopePolicy {
#[inline]
fn default() -> Self {
Self::deny_all()
}
}
impl ScopePolicy {
/// Constructs a policy that has no permissible alternatives
///
/// By default, this policy will deny all requests
#[inline]
pub const fn deny_all() -> Self {
Self {
inner: ScopePolicyInner::DenyAll,
}
}
/// Constructs a policy that does not require any scopes (allow)
#[inline]
pub const fn allow_any() -> Self {
Self {
inner: ScopePolicyInner::AllowAny,
}
}
/// Constructs a policy that requires this set of scopes
#[inline]
pub const fn allow_one(scope: Scope) -> Self {
Self {
inner: ScopePolicyInner::AllowOne(scope),
}
}
/// Add an alternate allowable scope
#[inline]
pub fn or_allow(self, scope: Scope) -> Self {
if scope.is_empty() {
let mut this = self;
this.inner = ScopePolicyInner::AllowAny;
this
} else {
match self.inner {
ScopePolicyInner::AllowAny => Self::allow_any(),
ScopePolicyInner::DenyAll => Self::allow_one(scope),
ScopePolicyInner::AllowOne(existing) => Self {
inner: ScopePolicyInner::AllowMany(vec![existing, scope]),
},
ScopePolicyInner::AllowMany(mut scopes) => {
scopes.push(scope);
Self {
inner: ScopePolicyInner::AllowMany(scopes),
}
}
}
}
}
/// Add an alternate allowable scope
pub fn allow(&mut self, scope: Scope) {
let this = std::mem::replace(self, Self::deny_all());
*self = this.or_allow(scope);
}
/// Constructs a policy that requires this set of scopes from a string
///
/// # Panics
///
/// This function will panic if the provided string is not a valid [`Scope`].
pub fn allow_one_from_static(scope: &'static str) -> Self {
match scope.parse::<Scope>() {
Ok(scope) => Self::allow_one(scope),
Err(err) => panic!("{}: scope = {}", err, scope),
}
}
/// Add an alternate allowable scope from a string
///
/// # Panics
///
/// This function will panic if the provided string is not a valid [`Scope`].
pub fn or_allow_from_static(self, scope: &'static str) -> Self {
match scope.parse::<Scope>() {
Ok(scope) => self.or_allow(scope),
Err(err) => panic!("{}: scope = {}", err, scope),
}
}
/// Add an alternate allowable scope from a string
///
/// # Panics
///
/// This function will panic if the provided string is not a valid [`Scope`].
pub fn allow_from_static(&mut self, scope: &'static str) {
match scope.parse::<Scope>() {
Ok(scope) => self.allow(scope),
Err(err) => panic!("{}: scope = {}", err, scope),
}
}
const fn is_allow_all(&self) -> bool {
matches!(self.inner, ScopePolicyInner::AllowAny)
}
}
impl aliri_traits::Policy for ScopePolicy {
type Request = Scope;
type Denial = InsufficientScope;
fn evaluate(&self, held: &Self::Request) -> Result<(), Self::Denial> {
let allowed = self.into_iter().any(|req| held.contains_all(req));
if allowed {
Ok(())
} else {
Err(InsufficientScope)
}
}
}
impl IntoIterator for ScopePolicy {
type Item = Scope;
type IntoIter = IntoIter;
#[inline]
fn into_iter(self) -> Self::IntoIter {
let inner = match self.inner {
ScopePolicyInner::DenyAll => IntoIterInner::Empty,
ScopePolicyInner::AllowAny => IntoIterInner::One(iter::once(Scope::empty())),
ScopePolicyInner::AllowOne(scope) => IntoIterInner::One(iter::once(scope)),
ScopePolicyInner::AllowMany(scopes) => IntoIterInner::Many(scopes.into_iter()),
};
IntoIter { inner }
}
}
/// An iterator over the scopes in a [`ScopePolicy`]
#[derive(Debug)]
pub struct IntoIter {
inner: IntoIterInner,
}
#[derive(Debug)]
enum IntoIterInner {
Empty,
One(iter::Once<Scope>),
Many(vec::IntoIter<Scope>),
}
impl Iterator for IntoIter {
type Item = Scope;
fn next(&mut self) -> Option<Self::Item> {
match &mut self.inner {
IntoIterInner::Empty => None,
IntoIterInner::One(iter) => iter.next(),
IntoIterInner::Many(iter) => iter.next(),
}
}
}
/// An iterator over a set of borrowed scopes
#[derive(Clone, Debug)]
pub struct Iter<'a> {
inner: IterInner<'a>,
}
#[derive(Clone, Debug)]
enum IterInner<'a> {
Empty,
One(iter::Once<&'a Scope>),
Many(slice::Iter<'a, Scope>),
}
impl<'a> Iterator for Iter<'a> {
type Item = &'a Scope;
#[inline]
fn next(&mut self) -> Option<Self::Item> {
match &mut self.inner {
IterInner::Empty => None,
IterInner::One(iter) => iter.next(),
IterInner::Many(iter) => iter.next(),
}
}
}
impl<'a> IntoIterator for &'a ScopePolicy {
type Item = &'a Scope;
type IntoIter = Iter<'a>;
#[inline]
fn into_iter(self) -> Self::IntoIter {
const EMPTY_SCOPE: &Scope = &Scope::empty();
Iter {
inner: match &self.inner {
ScopePolicyInner::DenyAll => IterInner::Empty,
ScopePolicyInner::AllowAny => IterInner::One(iter::once(EMPTY_SCOPE)),
ScopePolicyInner::AllowOne(scope) => IterInner::One(iter::once(scope)),
ScopePolicyInner::AllowMany(scopes) => IterInner::Many(scopes.iter()),
},
}
}
}
impl Extend<Scope> for ScopePolicy {
#[inline]
fn extend<I>(&mut self, iter: I)
where
I: IntoIterator<Item = Scope>,
{
for scope in iter {
self.allow(scope);
if self.is_allow_all() {
break;
}
}
}
}
impl iter::FromIterator<Scope> for ScopePolicy {
fn from_iter<I>(iter: I) -> Self
where
I: IntoIterator<Item = Scope>,
{
let mut set = Self::deny_all();
set.extend(iter);
set
}
}
impl From<Scope> for ScopePolicy {
#[inline]
fn from(scope: Scope) -> Self {
Self::allow_one(scope)
}
}
/// Construct a policy from a list of scope alternatives.
///
/// For more information about how the alternatives are evaluated, see [`ScopePolicy`].
///
/// ```
/// use aliri_oauth2::{scope, policy};
///
/// let policy = policy![
/// scope!["admin"],
/// scope!["special", "user"],
/// ];
/// ```
///
/// This is equivalent to the following:
///
/// ```
/// use aliri_oauth2::{ScopePolicy, scope};
///
/// let policy = ScopePolicy::deny_all()
/// .or_allow(scope!["admin"])
/// .or_allow(scope!["special", "user"]);
/// ```
#[macro_export]
macro_rules! policy {
($($scope:expr),* $(,)?) => {
$crate::ScopePolicy::deny_all()
$(
.or_allow($scope)
)*
};
}