Filesystem gate

Cargo.toml

@@ -2,18 +2,33 @@
 resolver = "2"
 members = [
     "components/chroot",
-    "components/readonly",
+    "components/gate",
+    "components/latch-defer-all",
+    "components/latch-deny-all",
+    "components/latch-deny-random",
+    "components/latch-deny-symlink-at",
+    "components/latch-n2",
+    "components/latch-n3",
+    "components/latch-n4",
+    "components/latch-n5",
+    "components/latch-path-glob",
+    "components/latch-readonly",
     "components/trace",
+    "crates/filesystem-latch",
+    "crates/filesystem-latch-n",
     "crates/test-harness",
 ]
 
 [workspace.dependencies]
 chrono = { git = "https://github.com/chronotope/chrono.git", branch = "0.5.x" }
 componentized-rt = { path = "./crates/componentized-rt" }
+filesystem-latch = { path = "./crates/filesystem-latch" }
+filesystem-latch-n = { path = "./crates/filesystem-latch-n" }
 heck = "0.5"
 tempfile = "3"
 test-harness = { path = "./crates/test-harness" }
 tokio = { version = "1", features = ["macros", "rt-multi-thread", "sync"] }
+wac-graph = "0.12"
 wasmtime = { version = "49", features = ["component-model-async"] }
 wasmtime-wasi = { version = "49", features = ["p3"] }
 wit-bindgen = { version = "0.62.0", features = ["async-spawn"] }

Makefile

@@ -25,7 +25,6 @@ clean: clean-components clean-wit
 clean-all: clean-components clean-tools clean-wit
 	cargo clean
 
-
 .PHONY: test
 test: components
 	cargo test --workspace

README.md

@@ -15,7 +15,16 @@ A collection of utility components that remix wasi:filesystem types and interfac
 ## Components
 
 - [`chroot`](./components/chroot/)
-- [`readonly`](./components/readonly/)
+- [`gate`](./components/gate/)
+- [`latch-deny-all`](./components/latch-deny-all/)
+- [`latch-deny-random`](./components/latch-deny-random/)
+- [`latch-deny-symlink-at`](./components/latch-deny-symlink-at/)
+- [`latch-defer-all`](./components/latch-defer-all/)
+- [`latch-n2`](./components/latch-n2/)
+- [`latch-n3`](./components/latch-n3/)
+- [`latch-n4`](./components/latch-n4/)
+- [`latch-n5`](./components/latch-n5/)
+- [`latch-readonly`](./components/latch-readonly/)
 - [`trace`](./components/trace/)
 
 ## Build

components/readonly/Cargo.toml → components/gate/Cargo.toml

@@ -1,5 +1,5 @@
 [package]
-name = "readonly"
+name = "gate"
 version = "0.1.0"
 edition = "2021"
 license = "Apache-2.0"
@@ -8,7 +8,9 @@ license = "Apache-2.0"
 crate-type = ["cdylib"]
 
 [dependencies]
+chrono = { workspace = true }
 componentized-rt = { workspace = true, features = ["executor"] }
+heck = { workspace = true }
 wit-bindgen = { workspace = true }
 
 [dev-dependencies]

components/gate/README.md

@@ -0,0 +1,41 @@
+# `gate`
+
+Filesystem gate access control for preopens and descriptors.
+
+Each operation is authorized by the imported latch before it reaches the filesystem, then the latch is told the final decision with `observe-decision`. Descriptor operations are authorized with the descriptor, its path, and the operation's arguments. The path of a preopen is its name, e.g. `/`, a descriptor opened with `open-at` has the path it was opened at, with `.` and `..` applied and symlinks followed where the host follows them. Testing whether two descriptors are the same object with `is-same-object` is not gated.
+
+How a denial is enforced depends on the operation:
+
+- Most operations fail with the error code the latch denied them with.
+- `read-via-stream` and `read-directory` return an empty stream, and the future resolves to the error.
+- `write-via-stream` and `append-via-stream` do not read the data stream, and the future resolves to the error.
+- Getting the preopens is authorized once, a denial returns no preopens. Each preopen is then authorized individually, a denied preopen is left out and the other preopens are returned.
+- Directory entries are authorized individually as they are read. A denied entry is left out of the stream and the read continues with the next entry.
+
+Denials are logged as warnings, except denied preopens and directory entries, which are left out rather than failed and are logged at the trace level:
+
+```
+Denied REASON=access OPERATION=wasi:filesystem/types#descriptor.open-at FD=/ PATH-FLAGS=() PATH=file.txt OPEN-FLAGS=(create) FLAGS=(read|write)
+Denied REASON=access OPERATION=wasi:filesystem/types#descriptor.read-directory FD=/ NAME=file.txt TYPE=regular-file
+```
+
+A latch error, or a failure to observe the decision, fails the operation with `other`, prefixed with `latch-error:`, and is logged as an error. A latch error for a directory entry ends the stream and fails the read. Getting the preopens can not fail, a latch error traps instead.
+
+```
+Latch error CODE=invalid-config<latch-path-glob> OPERATION=wasi:filesystem/types#descriptor.stat FD=/file.txt
+```
+
+## Interfaces
+
+Imports:
+
+- `componentized:filesystem/latch@0.3.0-dev`: decides whether each operation may proceed
+- `wasi:logging/logging@0.1.0-draft`: logs denials and latch errors
+- `wasi:clocks/system-clock@0.3.0`: types used by wasi:filesystem/types
+- `wasi:filesystem/types@0.3.0`: the descriptors the gated descriptors wrap
+- `wasi:filesystem/preopens@0.3.0`: the preopens the gated preopens wrap
+
+Exports:
+
+- `wasi:filesystem/types@0.3.0`: descriptors gated by the latch
+- `wasi:filesystem/preopens@0.3.0`: preopens gated by the latch