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| 1 | +//! The [`CapProvider<P>`] trait — unified capability access with optional scope enforcement. |
| 2 | +//! |
| 3 | +//! `CapProvider<P>` generalizes [`Has<P>`](crate::has::Has) to support both unscoped |
| 4 | +//! capabilities (which always succeed) and scoped capabilities |
| 5 | +//! ([`Attenuated<P, S>`](crate::attenuate::Attenuated)) which check the target against |
| 6 | +//! a scope before granting access. |
| 7 | +
|
| 8 | +use crate::cap::Cap; |
| 9 | +use crate::error::CapSecError; |
| 10 | +use crate::permission::Permission; |
| 11 | + |
| 12 | +/// A type that can provide a capability token for permission `P`, possibly |
| 13 | +/// after performing a scope check against the target. |
| 14 | +pub trait CapProvider<P: Permission> { |
| 15 | + /// Provides a `Cap<P>` for the given target, or returns an error if the |
| 16 | + /// target is outside the capability's scope. |
| 17 | + fn provide_cap(&self, target: &str) -> Result<Cap<P>, CapSecError>; |
| 18 | +} |
| 19 | + |
| 20 | +// We cannot use a blanket `impl<T: Has<P>> CapProvider<P> for T` because |
| 21 | +// Rust's coherence rules can't prove Attenuated won't impl Has in the future. |
| 22 | +// Instead, we require types to impl CapProvider explicitly. |
| 23 | +// The #[capsec::context] macro and built-in types all get impls. |
| 24 | +// For user-defined Has<P> impls, provide a convenience macro. |
| 25 | + |
| 26 | +/// Implement `CapProvider<P>` for a type that already implements `Has<P>`. |
| 27 | +/// |
| 28 | +/// Since `Has<P>` is infallible, the implementation always returns `Ok` |
| 29 | +/// and ignores the target string. |
| 30 | +/// |
| 31 | +/// # Example |
| 32 | +/// |
| 33 | +/// ```rust,ignore |
| 34 | +/// struct MyCtx { cap: Cap<FsRead> } |
| 35 | +/// impl Has<FsRead> for MyCtx { fn cap_ref(&self) -> Cap<FsRead> { self.cap.clone() } } |
| 36 | +/// capsec_core::impl_cap_provider_for_has!(MyCtx, FsRead); |
| 37 | +/// ``` |
| 38 | +#[macro_export] |
| 39 | +macro_rules! impl_cap_provider_for_has { |
| 40 | + ($ty:ty, $perm:ty) => { |
| 41 | + impl $crate::cap_provider::CapProvider<$perm> for $ty { |
| 42 | + fn provide_cap( |
| 43 | + &self, |
| 44 | + _target: &str, |
| 45 | + ) -> Result<$crate::cap::Cap<$perm>, $crate::error::CapSecError> { |
| 46 | + Ok(<Self as $crate::has::Has<$perm>>::cap_ref(self)) |
| 47 | + } |
| 48 | + } |
| 49 | + }; |
| 50 | +} |
| 51 | + |
| 52 | +// ── Built-in impls: Cap<P>, SendCap<P> ───────────────────────────── |
| 53 | + |
| 54 | +impl<P: Permission> CapProvider<P> for Cap<P> { |
| 55 | + fn provide_cap(&self, _target: &str) -> Result<Cap<P>, CapSecError> { |
| 56 | + Ok(Cap::new()) |
| 57 | + } |
| 58 | +} |
| 59 | + |
| 60 | +impl<P: Permission> CapProvider<P> for crate::cap::SendCap<P> { |
| 61 | + fn provide_cap(&self, _target: &str) -> Result<Cap<P>, CapSecError> { |
| 62 | + Ok(Cap::new()) |
| 63 | + } |
| 64 | +} |
| 65 | + |
| 66 | +// ── Subsumption ───────────────────────────────────────────────────── |
| 67 | + |
| 68 | +macro_rules! impl_cap_provider_subsumes { |
| 69 | + ($super:ty => $($sub:ty),+) => { |
| 70 | + $( |
| 71 | + impl CapProvider<$sub> for Cap<$super> { |
| 72 | + fn provide_cap(&self, _target: &str) -> Result<Cap<$sub>, CapSecError> { |
| 73 | + Ok(Cap::new()) |
| 74 | + } |
| 75 | + } |
| 76 | + )+ |
| 77 | + } |
| 78 | +} |
| 79 | + |
| 80 | +use crate::permission::*; |
| 81 | + |
| 82 | +impl_cap_provider_subsumes!(FsAll => FsRead, FsWrite); |
| 83 | +impl_cap_provider_subsumes!(NetAll => NetConnect, NetBind); |
| 84 | + |
| 85 | +// ── Ambient ───────────────────────────────────────────────────────── |
| 86 | + |
| 87 | +macro_rules! impl_cap_provider_ambient { |
| 88 | + ($($perm:ty),+) => { |
| 89 | + $( |
| 90 | + impl CapProvider<$perm> for Cap<Ambient> { |
| 91 | + fn provide_cap(&self, _target: &str) -> Result<Cap<$perm>, CapSecError> { |
| 92 | + Ok(Cap::new()) |
| 93 | + } |
| 94 | + } |
| 95 | + )+ |
| 96 | + } |
| 97 | +} |
| 98 | + |
| 99 | +impl_cap_provider_ambient!( |
| 100 | + FsRead, FsWrite, FsAll, NetConnect, NetBind, NetAll, EnvRead, EnvWrite, Spawn |
| 101 | +); |
| 102 | + |
| 103 | +// ── Tuples ────────────────────────────────────────────────────────── |
| 104 | + |
| 105 | +macro_rules! impl_cap_provider_tuple_first { |
| 106 | + ([$($a:ident),+]; $all:tt) => { |
| 107 | + $( impl_cap_provider_tuple_first!(@inner $a; $all); )+ |
| 108 | + }; |
| 109 | + (@inner $a:ident; [$($b:ident),+]) => { |
| 110 | + $( |
| 111 | + impl CapProvider<$a> for Cap<($a, $b)> { |
| 112 | + fn provide_cap(&self, _target: &str) -> Result<Cap<$a>, CapSecError> { |
| 113 | + Ok(Cap::new()) |
| 114 | + } |
| 115 | + } |
| 116 | + )+ |
| 117 | + }; |
| 118 | +} |
| 119 | + |
| 120 | +macro_rules! impl_cap_provider_tuple_second { |
| 121 | + ($first:ident $(, $rest:ident)+) => { |
| 122 | + $( |
| 123 | + impl CapProvider<$first> for Cap<($rest, $first)> { |
| 124 | + fn provide_cap(&self, _target: &str) -> Result<Cap<$first>, CapSecError> { |
| 125 | + Ok(Cap::new()) |
| 126 | + } |
| 127 | + } |
| 128 | + impl CapProvider<$rest> for Cap<($first, $rest)> { |
| 129 | + fn provide_cap(&self, _target: &str) -> Result<Cap<$rest>, CapSecError> { |
| 130 | + Ok(Cap::new()) |
| 131 | + } |
| 132 | + } |
| 133 | + )+ |
| 134 | + impl_cap_provider_tuple_second!($($rest),+); |
| 135 | + }; |
| 136 | + ($single:ident) => {}; |
| 137 | +} |
| 138 | + |
| 139 | +impl_cap_provider_tuple_first!( |
| 140 | + [FsRead, FsWrite, FsAll, NetConnect, NetBind, NetAll, EnvRead, EnvWrite, Spawn, Ambient]; |
| 141 | + [FsRead, FsWrite, FsAll, NetConnect, NetBind, NetAll, EnvRead, EnvWrite, Spawn, Ambient] |
| 142 | +); |
| 143 | + |
| 144 | +impl_cap_provider_tuple_second!( |
| 145 | + FsRead, FsWrite, FsAll, NetConnect, NetBind, NetAll, EnvRead, EnvWrite, Spawn, Ambient |
| 146 | +); |
| 147 | + |
| 148 | +#[cfg(test)] |
| 149 | +mod tests { |
| 150 | + use super::*; |
| 151 | + |
| 152 | + #[test] |
| 153 | + fn cap_provides() { |
| 154 | + let root = crate::root::test_root(); |
| 155 | + let cap = root.grant::<FsRead>(); |
| 156 | + assert!(cap.provide_cap("/any").is_ok()); |
| 157 | + } |
| 158 | + |
| 159 | + #[test] |
| 160 | + fn sendcap_provides() { |
| 161 | + let root = crate::root::test_root(); |
| 162 | + let cap = root.grant::<FsRead>().make_send(); |
| 163 | + assert!(cap.provide_cap("/any").is_ok()); |
| 164 | + } |
| 165 | + |
| 166 | + #[test] |
| 167 | + fn subsumption_provides() { |
| 168 | + let root = crate::root::test_root(); |
| 169 | + let cap = root.grant::<FsAll>(); |
| 170 | + let result: Result<Cap<FsRead>, _> = cap.provide_cap("/any"); |
| 171 | + assert!(result.is_ok()); |
| 172 | + } |
| 173 | + |
| 174 | + #[test] |
| 175 | + fn ambient_provides() { |
| 176 | + let root = crate::root::test_root(); |
| 177 | + let cap = root.grant::<Ambient>(); |
| 178 | + let result: Result<Cap<FsRead>, _> = cap.provide_cap("/any"); |
| 179 | + assert!(result.is_ok()); |
| 180 | + } |
| 181 | + |
| 182 | + #[test] |
| 183 | + fn tuple_provides() { |
| 184 | + let root = crate::root::test_root(); |
| 185 | + let cap = root.grant::<(FsRead, NetConnect)>(); |
| 186 | + assert!(CapProvider::<FsRead>::provide_cap(&cap, "/any").is_ok()); |
| 187 | + assert!(CapProvider::<NetConnect>::provide_cap(&cap, "host").is_ok()); |
| 188 | + } |
| 189 | +} |
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