fabaccess-bffh/bffhd/authorization/permissions.rs

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//! Access control logic
//!
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use std::fmt;
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use std::cmp::Ordering;
use std::convert::{TryFrom, Into};
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fn is_sep_char(c: char) -> bool {
c == '.'
}
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#[derive(Debug, Clone, Eq, PartialEq, serde::Serialize, serde::Deserialize)]
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/// A set of privileges to a thing
pub struct PrivilegesBuf {
/// Which permission is required to know about the existance of this thing
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pub disclose: PermissionBuf,
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/// Which permission is required to read this thing
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pub read: PermissionBuf,
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/// Which permission is required to write parts of this thing
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pub write: PermissionBuf,
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/// Which permission is required to manage all parts of this thing
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pub manage: PermissionBuf
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}
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#[derive(Debug, Clone, PartialEq, Eq, Hash, serde::Serialize, serde::Deserialize)]
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#[repr(transparent)]
#[serde(transparent)]
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/// An owned permission string
///
/// This is under the hood just a fancy std::String.
// TODO: What is the possible fallout from homograph attacks?
// i.e. "bffh.perm" is not the same as "bffհ.реrm" (Armenian 'հ':Հ and Cyrillic 'е':Е)
// See also https://util.unicode.org/UnicodeJsps/confusables.jsp
pub struct PermissionBuf {
inner: String,
}
impl PermissionBuf {
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#[inline(always)]
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/// Allocate an empty `PermissionBuf`
pub fn new() -> Self {
PermissionBuf { inner: String::new() }
}
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#[inline(always)]
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/// Allocate a `PermissionBuf` with the given capacity given to the internal [`String`]
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pub fn with_capacity(cap: usize) -> Self {
PermissionBuf { inner: String::with_capacity(cap) }
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}
#[inline(always)]
pub fn as_permission(&self) -> &Permission {
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self.as_ref()
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}
pub fn push<P: AsRef<Permission>>(&mut self, perm: P) {
self._push(perm.as_ref())
}
pub fn _push(&mut self, perm: &Permission) {
// in general we always need a separator unless the last byte is one or the string is empty
let need_sep = self.inner.chars().rev().next().map(|c| !is_sep_char(c)).unwrap_or(false);
if need_sep {
self.inner.push('.')
}
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self.inner.push_str(perm.as_str())
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}
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#[inline(always)]
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pub const fn from_string_unchecked(inner: String) -> Self {
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Self { inner }
}
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#[inline]
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pub fn from_perm(perm: &Permission) -> Self {
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Self { inner: perm.as_str().to_string() }
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}
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#[inline(always)]
pub fn into_string(self) -> String {
self.inner
}
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#[inline(always)]
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pub fn is_empty(&self) -> bool {
self.inner.is_empty()
}
}
impl AsRef<String> for PermissionBuf {
#[inline(always)]
fn as_ref(&self) -> &String {
&self.inner
}
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}
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impl AsRef<str> for PermissionBuf {
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#[inline(always)]
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fn as_ref(&self) -> &str {
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&self.inner.as_str()
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}
}
impl AsRef<Permission> for PermissionBuf {
#[inline]
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fn as_ref(&self) -> &Permission {
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Permission::new(self)
}
}
impl PartialOrd for PermissionBuf {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
let a: &Permission = self.as_ref();
a.partial_cmp(other.as_ref())
}
}
impl fmt::Display for PermissionBuf {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.inner.fmt(f)
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}
}
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#[derive(PartialEq, Eq, Hash, Debug)]
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#[repr(transparent)]
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/// A borrowed permission string
///
/// Permissions have total equality and partial ordering.
/// Specifically permissions on the same path in a tree can be compared for specificity.
/// This means that ```(bffh.perm) > (bffh.perm.sub) == true```
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/// but ```(bffh.perm) > (unrelated.but.more.specific.perm) == false```.
/// This allows to check if PermRule a grants Perm b by checking `a > b`.
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pub struct Permission(str);
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impl Permission {
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#[inline(always)]
// We can't make this `const` just yet because `str` is always a fat pointer meaning we can't
// just const cast it, and `CoerceUnsized` and friends are currently unstable.
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pub fn new<S: AsRef<str> + ?Sized>(s: &S) -> &Permission {
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// Safe because s is a valid reference
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unsafe { &*(s.as_ref() as *const str as *const Permission) }
}
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#[inline(always)]
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pub fn as_str(&self) -> &str {
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&self.0
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}
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#[inline(always)]
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pub fn iter(&self) -> std::str::Split<char> {
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self.0.split('.')
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}
}
impl PartialOrd for Permission {
fn partial_cmp(&self, other: &Permission) -> Option<Ordering> {
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let mut i = self.iter();
let mut j = other.iter();
let (mut l, mut r);
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while {
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l = i.next();
r = j.next();
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l.is_some() && r.is_some()
} {
if l.unwrap() != r.unwrap() {
return None;
}
}
match (l,r) {
(None, None) => Some(Ordering::Equal),
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(Some(_), None) => Some(Ordering::Less),
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(None, Some(_)) => Some(Ordering::Greater),
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(Some(_), Some(_)) => unreachable!("Broken contract in Permission::partial_cmp: sides \
should never be both Some!"),
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}
}
}
impl AsRef<Permission> for Permission {
#[inline]
fn as_ref(&self) -> &Permission {
self
}
}
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#[derive(Clone, Debug, PartialEq, Eq, Hash, serde::Serialize, serde::Deserialize)]
#[serde(try_from = "String")]
#[serde(into = "String")]
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pub enum PermRule {
/// The permission is precise,
///
/// i.e. `Base("bffh.perm")` grants bffh.perm but does not grant permission for bffh.perm.sub
Base(PermissionBuf),
/// The permissions is for the children of the node
///
/// i.e. `Children("bffh.perm")` grants bffh.perm.sub, bffh.perm.sub.two *BUT NOT* bffh.perm
/// itself.
Children(PermissionBuf),
/// The permissions is for the subtree marked by the node
///
/// i.e. `Children("bffh.perm")` grants bffh.perm.sub, bffh.perm.sub.two and also bffh.perm
/// itself.
Subtree(PermissionBuf),
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// This lacks what LDAP calls "ONELEVEL": The ability to grant the exact children but not several
// levels deep, i.e. `Onelevel("bffh.perm")` grants bffh.perm.sub *BUT NOT* bffh.perm.sub.two or
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// bffh.perm itself.
// I can't think of a reason to use that so I'm skipping it for now.
}
impl PermRule {
// Does this rule match that permission
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pub fn match_perm<P: AsRef<Permission> + ?Sized>(&self, perm: &P) -> bool {
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match self {
PermRule::Base(ref base) => base.as_permission() == perm.as_ref(),
PermRule::Children(ref parent) => parent.as_permission() > perm.as_ref() ,
PermRule::Subtree(ref parent) => parent.as_permission() >= perm.as_ref(),
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}
}
}
impl fmt::Display for PermRule {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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PermRule::Base(perm)
=> write!(f, "{}", perm),
PermRule::Children(parent)
=> write!(f,"{}.+", parent),
PermRule::Subtree(parent)
=> write!(f,"{}.*", parent),
}
}
}
impl Into<String> for PermRule {
fn into(self) -> String {
match self {
PermRule::Base(perm) => perm.into_string(),
PermRule::Children(mut perm) => {
perm.push(Permission::new("+"));
perm.into_string()
},
PermRule::Subtree(mut perm) => {
perm.push(Permission::new("+"));
perm.into_string()
}
}
}
}
impl TryFrom<String> for PermRule {
type Error = &'static str;
fn try_from(mut input: String) -> std::result::Result<Self, Self::Error> {
// Check out specifically the last two chars
let len = input.len();
if len <= 2 {
Err("Input string for PermRule is too short")
} else {
match &input[len-2..len] {
".+" => {
input.truncate(len-2);
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Ok(PermRule::Children(PermissionBuf::from_string_unchecked(input)))
},
".*" => {
input.truncate(len-2);
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Ok(PermRule::Subtree(PermissionBuf::from_string_unchecked(input)))
},
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_ => Ok(PermRule::Base(PermissionBuf::from_string_unchecked(input))),
}
}
}
}
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#[cfg(test)]
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mod tests {
use super::*;
#[test]
fn permission_ord_test() {
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assert!(PermissionBuf::from_string_unchecked("bffh.perm".to_string())
> PermissionBuf::from_string_unchecked("bffh.perm.sub".to_string()));
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}
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#[test]
fn permission_simple_check_test() {
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let perm = PermissionBuf::from_string_unchecked("test.perm".to_string());
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let rule = PermRule::Base(perm.clone());
assert!(rule.match_perm(&perm));
}
#[test]
fn permission_children_checks_only_children() {
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let perm = PermissionBuf::from_string_unchecked("test.perm".to_string());
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let rule = PermRule::Children(perm.clone());
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assert_eq!(rule.match_perm(&perm), false);
let perm2 = PermissionBuf::from_string_unchecked("test.perm.child".to_string());
let perm3 = PermissionBuf::from_string_unchecked("test.perm.child.deeper".to_string());
assert!(rule.match_perm(&perm2));
assert!(rule.match_perm(&perm3));
}
#[test]
fn permission_subtree_checks_base() {
let perm = PermissionBuf::from_string_unchecked("test.perm".to_string());
let rule = PermRule::Subtree(perm.clone());
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assert!(rule.match_perm(&perm));
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let perm2 = PermissionBuf::from_string_unchecked("test.perm.child".to_string());
let perm3 = PermissionBuf::from_string_unchecked("test.perm.child.deeper".to_string());
assert!(rule.match_perm(&perm2));
assert!(rule.match_perm(&perm3));
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}
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#[test]
fn format_and_read_compatible() {
use std::convert::TryInto;
let testdata = vec![
("testrole", "testsource"),
("", "norole"),
("nosource", "")
].into_iter().map(|(n,s)| (n.to_string(), s.to_string()));
for (name, source) in testdata {
let role = RoleIdentifier { name, source };
let fmt_string = format!("{}", &role);
println!("{:?} is formatted: {}", &role, &fmt_string);
let parsed: RoleIdentifier = fmt_string.try_into().unwrap();
println!("Which parses into {:?}", &parsed);
assert_eq!(role, parsed);
}
}
#[test]
fn rules_from_string_test() {
assert_eq!(
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PermRule::Base(PermissionBuf::from_string_unchecked("bffh.perm".to_string())),
PermRule::try_from("bffh.perm".to_string()).unwrap()
);
assert_eq!(
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PermRule::Children(PermissionBuf::from_string_unchecked("bffh.perm".to_string())),
PermRule::try_from("bffh.perm.+".to_string()).unwrap()
);
assert_eq!(
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PermRule::Subtree(PermissionBuf::from_string_unchecked("bffh.perm".to_string())),
PermRule::try_from("bffh.perm.*".to_string()).unwrap()
);
}
#[test]
fn rules_from_string_edgecases_test() {
assert!(PermRule::try_from("*".to_string()).is_err());
assert!(PermRule::try_from("+".to_string()).is_err());
}
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}