Rust crypto core: FrodoKEM port, hybrid suite, Fury, STREAM, key files

FrodoKEM-640-SHAKE is ported from CIRCL v1.6.4 (the RustCrypto crate
implements the incompatible ISO variant) and reproduces the reference
NIST KAT digest. ML-KEM-768 comes from RustCrypto ml-kem. Derivation,
encapsulation, implicit rejection, KEK, header MAC, header parsing,
STREAM and Argon2id key files all match vectors from the Go oracle, Go's
files decrypt in Rust, and Go decrypts Rust's.

Co-Authored-By: Claude <noreply@anthropic.com>

tests/common/mod.rs

@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+#![allow(dead_code)]
+
+use std::path::{Path, PathBuf};
+use std::process::Command;
+use std::sync::OnceLock;
+
+pub fn root() -> PathBuf {
+    PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+}
+
+/// Whether the Go toolchain is available for oracle-backed tests. When it
+/// is not, those tests print SKIPPED and return; CI installs Go so they
+/// always run there (VAULT_REQUIRE_ORACLE=1 turns a skip into a failure).
+pub fn have_go() -> bool {
+    let ok = Command::new("go").arg("version").output().is_ok_and(|o| o.status.success());
+    if !ok && std::env::var_os("VAULT_REQUIRE_ORACLE").is_some() {
+        panic!("VAULT_REQUIRE_ORACLE is set but go is not available");
+    }
+    ok
+}
+
+pub fn skip(why: &str) {
+    eprintln!("SKIPPED: {why}");
+}
+
+/// Builds the Go oracle CLI once per test process ($VAULT_GO_ORACLE wins).
+pub fn go_oracle() -> Option<PathBuf> {
+    static BIN: OnceLock<Option<PathBuf>> = OnceLock::new();
+    BIN.get_or_init(|| {
+        if let Some(p) = std::env::var_os("VAULT_GO_ORACLE") {
+            return Some(PathBuf::from(p));
+        }
+        if !have_go() {
+            return None;
+        }
+        let out = root().join("target").join("vault-go-oracle");
+        let st = Command::new("go")
+            .args(["build", "-o"])
+            .arg(&out)
+            .arg(".")
+            .current_dir(root().join("oracle/go"))
+            .env("CGO_ENABLED", "0")
+            .status()
+            .expect("run go build");
+        assert!(st.success(), "building the Go oracle failed");
+        Some(out)
+    })
+    .clone()
+}
+
+pub fn go_test(pkg: &str, test: &str, env: &[(&str, &Path)]) -> std::process::Output {
+    let mut c = Command::new("go");
+    c.args(["test", "-count=1", "-v", "-run", &format!("^{test}$"), pkg])
+        .current_dir(root().join("oracle/go"));
+    for (k, v) in env {
+        c.env(k, v);
+    }
+    c.output().expect("run go test")
+}