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Identities for entities did.bot
agent llm did
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12 kB · 270 lines
Rust
at main
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use std::fmt;
use crate::read::read;use crate::{ NsidPattern, Scope, ScopeParseError, ScopeWarning, Transition, MAX_GRANT_ATOMS, MAX_GRANT_BYTES, MAX_SCOPE_ATOMS, MAX_SCOPE_BYTES,};
/// A space-separated set of [`Scope`]s, as carried on a `scope` parameter or/// a token response.////// Canonical by construction: [`ScopeSet::new`] sorts, dedupes, and drops/// any atom already admitted by another atom of its kind, so two sets/// built from the same members in different orders — or with redundant/// members — compare equal. Policy is a set of records in a repository,/// which has no inherent order, so a ceiling has to be a function of the/// rule set alone; a `ScopeSet` that could represent the same ceiling two/// different ways would let vector order silently change what a policy/// means, which is exactly the failure this type exists to rule out.#[derive(Debug, Clone, PartialEq, Eq, Default)]pub struct ScopeSet(pub Vec<Scope>);
impl ScopeSet { /// Builds a canonical [`ScopeSet`] from a bag of atoms: sorted, deduped, /// and with every atom already admitted by another atom of its kind /// dropped. Containment among distinct atoms is a strict partial order — /// two distinct atoms can never admit each other — so which atom /// survives never depends on the input order. /// /// Only an atom of the same kind stands in for another. A ceiling judges /// each kind on its own ([`ScopeSet::narrow`]), and this server never /// grants a `transition:` scope, so `transition:generic` does not absorb /// the `repo:` scopes asked for beside it. pub fn new(atoms: Vec<Scope>) -> Self { let mut atoms = atoms; atoms.sort(); atoms.dedup(); let kept = atoms .iter() .enumerate() .filter(|(i, atom)| { !atoms.iter().enumerate().any(|(j, other)| { j != *i && other.kind() == atom.kind() && other.contains(atom) }) }) .map(|(_, atom)| atom.clone()) .collect(); ScopeSet(kept) }
/// Whether some atom of this set admits `wanted`, which is what a token /// carrying this set may do. pub fn covers(&self, wanted: &Scope) -> bool { self.0.iter().any(|atom| atom.contains(wanted)) }
/// Whether a token carrying this set may act at another service: call /// `lxm` there through `atproto-proxy`, or take a token for it from /// `com.atproto.server.getServiceAuth`. `aud` names the service, as a /// DID or a DID and a service fragment. /// /// `None` asks for a token bound to no method. An `rpc:*` scope for /// `aud` admits one, and so does `transition:generic`, as the reference /// PDS reads it. pub fn permits_rpc(&self, lxm: Option<&str>, aud: &str) -> bool { if lxm.is_none() && self.0.contains(&Scope::Transition(Transition::Generic)) { return true; } self.covers(&Scope::Rpc { method: lxm.map_or(NsidPattern::Any, |lxm| NsidPattern::Exact(lxm.to_owned())), aud: Some(aud.to_owned()), }) }
/// Parses a whole `scope` string: OAuth2's space-separated list of atoms. /// /// Checks [`MAX_SCOPE_BYTES`] before reading any atom, and /// [`MAX_SCOPE_ATOMS`] against the scopes they name. An atom this grammar /// cannot read is kept as [`Scope::Unknown`]; see [`ScopeSet::read`]. pub fn parse(s: &str) -> Result<Self, ScopeParseError> { Self::read(s).map(|(set, _)| set) }
/// Reads a scope an app asked for: the set, and each warning its atoms' /// forms carry, beside the atom as the app wrote it. /// /// Every form the permission spec defines reads without a warning. A form /// it does not define is read as well as it can be, with a warning /// saying how. An atom that names no scope this grammar reads is kept as /// [`Scope::Unknown`], with a warning, rather than failing the string: a /// server can drop it and grant the rest. Only the bounds and a character /// no scope may hold fail the whole string. pub fn read(s: &str) -> Result<(Self, Vec<(String, ScopeWarning)>), ScopeParseError> { Self::read_within(s, MAX_SCOPE_BYTES, MAX_SCOPE_ATOMS) }
/// Parses a grant this server stored, which may be larger than any /// request: each `include:` in the request became the atoms its /// permission set grants. /// /// Checks [`MAX_GRANT_BYTES`] and [`MAX_GRANT_ATOMS`] before parsing any /// atom. pub fn parse_grant(s: &str) -> Result<Self, ScopeParseError> { Self::read_within(s, MAX_GRANT_BYTES, MAX_GRANT_ATOMS).map(|(set, _)| set) }
fn read_within( s: &str, max_bytes: usize, max_scopes: usize, ) -> Result<(Self, Vec<(String, ScopeWarning)>), ScopeParseError> { if s.len() > max_bytes { return Err(ScopeParseError::TooLong { len: s.len(), max: max_bytes, }); } // Every atom names at least one scope, so a string with too many atoms // is refused before any is read. let atoms: Vec<&str> = s.split_whitespace().collect(); if atoms.len() > max_scopes { return Err(ScopeParseError::TooManyAtoms { count: atoms.len(), max: max_scopes, }); } let mut scopes = Vec::new(); let mut warnings = Vec::new(); for atom in atoms { let read = match read(atom) { Ok(read) => read, Err( error @ (ScopeParseError::AtomTooLong(_) | ScopeParseError::ForbiddenCharacter(_)), ) => return Err(error), Err(error) => crate::read::Read { scopes: vec![Scope::Unknown(atom.to_owned())], warnings: vec![ScopeWarning::Unreadable(error.to_string())], }, }; scopes.extend(read.scopes); warnings.extend( read.warnings .into_iter() .map(|warning| (atom.to_owned(), warning)), ); } if scopes.len() > max_scopes { return Err(ScopeParseError::TooManyAtoms { count: scopes.len(), max: max_scopes, }); } Ok((ScopeSet::new(scopes), warnings)) }
/// Is every requested scope admitted by some scope in `ceiling`? /// /// Returns the whole intersected grant on success. On refusal, returns /// the first requested scope that no ceiling scope admits at all — /// `plan/scope-policy.md`'s "refuse rather than silently narrow, and say /// which scope", which needs this exact atom to build the /// `WWW-Authenticate: Bearer error="insufficient_scope", scope="…"` /// header. /// /// A requested atom's grant is the *union* of its overlap with every /// ceiling atom, not the single largest overlap: `ceiling` is a set with /// no inherent order, so a ceiling atom that grants `create` and one /// that grants `delete` must both survive regardless of which one this /// loop visits first. [`ScopeSet::new`] then collapses any overlap that /// one of its siblings already subsumes. /// /// An overlap counts only in the requested atom's own kind, as in /// [`ScopeSet::narrow`]: `transition:generic` under a `repo:*` ceiling is /// refused, not paid out as `repo:*`. pub fn intersect(&self, ceiling: &ScopeSet) -> Result<ScopeSet, ScopeRefused> { let mut granted = Vec::with_capacity(self.0.len()); for requested in &self.0 { let mut admitted = false; for ceiling_scope in &ceiling.0 { let Some(overlap) = ceiling_scope.intersect(requested) else { continue; }; if overlap.kind() == requested.kind() { granted.push(overlap); admitted = true; } } if !admitted { return Err(ScopeRefused(requested.clone())); } } Ok(ScopeSet::new(granted)) }
/// The same overlap, split into what the ceiling granted and what it /// did not. /// /// [`ScopeSet::intersect`] refuses the whole request the moment one /// atom falls outside the ceiling, which is what `token` and every /// other caller checking a grant against a ceiling wants. A consent /// decision wants the other answer: the grant that *is* available, plus /// the part of the request it does not cover, so the record an agent /// approves can name both. /// /// Projection runs from the requested atom onto the ceiling and never /// the other way, and only ever within one kind: a granted atom is /// always a narrowing of something the request named, of that atom's own /// kind. So a wide atom is never paid out in capabilities of a kind /// nobody asked for — `transition:generic` overlaps `repo:*` and /// `rpc:*`, and a ceiling holding those grants it nothing. /// /// `cut` is every requested atom that no granted atom contains — the /// atoms the ceiling dropped outright and the atoms it shrank alike. /// The grammar has no difference operation, so an atom the ceiling /// narrowed (`repo:*?action=create&action=delete` against a ceiling holding /// `repo:*?action=create`) is named whole rather than as the sliver /// removed from it. An empty `cut` means the ceiling granted the /// request exactly as asked, which is the only case /// [`ScopeSet::intersect`] and this agree on completely. pub fn narrow(&self, ceiling: &ScopeSet) -> (ScopeSet, ScopeSet) { let mut overlaps = Vec::with_capacity(self.0.len()); for requested in &self.0 { for ceiling_scope in &ceiling.0 { let Some(overlap) = requested.intersect(ceiling_scope) else { continue; }; // Same kind, or nothing. An overlap of a different variant // than the atom that was asked for is not a narrowing of // that atom, it is a *re-expression* of it as capabilities // the request never named: `transition:generic` overlaps // `repo:*` and `rpc:*`, and taking those would hand back a // grant nobody asked for in that form — a wide atom paid out // as its pieces. An atom whose every overlap is refused this // way is granted nothing and lands in `cut`. if overlap.kind() == requested.kind() { overlaps.push(overlap); } } } let granted = ScopeSet::new(overlaps); let cut = ScopeSet::new( self.0 .iter() .filter(|requested| !granted.0.iter().any(|atom| atom.contains(requested))) .cloned() .collect(), ); (granted, cut) }}
/// The exact scope a ceiling refused, for `insufficient_scope`.#[derive(Debug, Clone, PartialEq, Eq, thiserror::Error)]#[error("scope `{0}` is outside this agent's ceiling")]pub struct ScopeRefused(pub Scope);
impl fmt::Display for ScopeSet { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { let joined = self .0 .iter() .map(ToString::to_string) .collect::<Vec<_>>() .join(" "); write!(f, "{joined}") }}