Add ctap fuzz target

This fuzz target sends a sequence of arbitrary CTAP1 or CTAP2 requests
to the authenticator.

fuzz/.gitignore

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+target
+corpus
+artifacts
+coverage

fuzz/Cargo.toml

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+[package]
+name = "fido-authenticator-fuzz"
+version = "0.0.0"
+publish = false
+edition = "2021"
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies]
+ctap-types = { version = "0.2.0", features = ["arbitrary"] }
+libfuzzer-sys = "0.4"
+trussed-staging = { version = "0.3.0", features = ["chunked", "hkdf", "virt"] }
+
+[dependencies.fido-authenticator]
+path = ".."
+
+[[bin]]
+name = "ctap"
+path = "fuzz_targets/ctap.rs"
+test = false
+doc = false
+bench = false
+
+[patch.crates-io]
+ctap-types = { git = "https://github.com/trussed-dev/ctap-types.git", branch = "arbitrary" }
+littlefs2 = { git = "https://github.com/trussed-dev/littlefs2.git", rev = "2b45a7559ff44260c6dd693e4cb61f54ae5efc53" }
+trussed = { git = "https://github.com/trussed-dev/trussed.git", rev = "b548d379dcbd67d29453d94847b7bc33ae92e673" }
+trussed-chunked = { git = "https://github.com/trussed-dev/trussed-staging.git", tag = "chunked-v0.1.0" }
+trussed-hkdf = { git = "https://github.com/trussed-dev/trussed-staging.git", tag = "hkdf-v0.2.0" }
+trussed-staging = { git = "https://github.com/trussed-dev/trussed-staging.git", tag = "v0.3.0" }

fuzz/fuzz_targets/ctap.rs

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+#![no_main]
+
+use ctap_types::{authenticator::Request, ctap1::Authenticator as _, ctap2::Authenticator as _};
+use fido_authenticator::{Authenticator, Config, Conforming};
+use trussed_staging::virt;
+
+use libfuzzer_sys::fuzz_target;
+
+fuzz_target!(|requests: Vec<Request<'_>>| {
+    virt::with_ram_client("fido", |client| {
+        let mut authenticator = Authenticator::new(
+            client,
+            Conforming {},
+            Config {
+                max_msg_size: 0,
+                skip_up_timeout: None,
+                max_resident_credential_count: None,
+                large_blobs: None,
+                nfc_transport: false,
+            },
+        );
+
+        for request in requests {
+            match request {
+                Request::Ctap1(request) => {
+                    authenticator.call_ctap1(&request).ok();
+                }
+                Request::Ctap2(request) => {
+                    authenticator.call_ctap2(&request).ok();
+                }
+            }
+        }
+    });
+});