Add KAT test Windows support (C backend only) and unify across platforms

Unix KAT tests rely on shell pipelines (sha256sum, cut, xargs) not
available on Windows. Introduce test/src/kat_client.py — a portable
Python script that runs gen_KAT binaries, SHA-256-hashes their stdout,
and checks against META.yml, replacing the shell one-liner:
```
 set -o pipefail; $W $MLKEM512_DIR/bin/gen_KAT512 | $SHA256SUM | \
 cut -d " " -f 1 | xargs ./META.sh ML-KEM-512 kat-sha256
```
Add gen_KAT{512,768,1024}, gen_KAT, run_kat, and test targets to
Makefile.Microsoft_nmake. quickcheck now aliases test.

To keep KAT checking uniform across platforms, the Unix Makefile is
migrated to the same Python script. A single mechanism now drives
KAT verification on both Unix and Windows. META.sh and the SHA256SUM
detection block are removed as they are no longer needed.

Signed-off-by: willieyz <willie.zhao@chelpis.com>

Author: willieyz

META.sh

@@ -49,18 +49,12 @@ build: func kat acvp wycheproof
 test: run_kat run_func run_acvp run_wycheproof run_unit run_alloc run_rng_fail
 	$(Q)echo "  Everything checks fine!"
 
-# Detect available SHA256 command
-SHA256SUM := $(shell command -v shasum >/dev/null 2>&1 && echo "shasum -a 256" || (command -v sha256sum >/dev/null 2>&1 && echo "sha256sum" || echo ""))
-ifeq ($(SHA256SUM),)
-$(error Neither 'shasum' nor 'sha256sum' found. Please install one of these tools.)
-endif
-
 run_kat_512: kat_512
-	set -o pipefail; $(W) $(MLKEM512_DIR)/bin/gen_KAT512 | $(SHA256SUM) | cut -d " " -f 1 | xargs ./META.sh ML-KEM-512 kat-sha256
+	EXEC_WRAPPER="$(EXEC_WRAPPER)" python3 test/src/kat_client.py --scheme 512
 run_kat_768: kat_768
-	set -o pipefail; $(W) $(MLKEM768_DIR)/bin/gen_KAT768 | $(SHA256SUM) | cut -d " " -f 1 | xargs ./META.sh ML-KEM-768  kat-sha256
+	EXEC_WRAPPER="$(EXEC_WRAPPER)" python3 test/src/kat_client.py --scheme 768
 run_kat_1024: kat_1024
-	set -o pipefail; $(W) $(MLKEM1024_DIR)/bin/gen_KAT1024 | $(SHA256SUM) | cut -d " " -f 1 | xargs ./META.sh ML-KEM-1024  kat-sha256
+	EXEC_WRAPPER="$(EXEC_WRAPPER)" python3 test/src/kat_client.py --scheme 1024
 run_kat: run_kat_512 run_kat_768 run_kat_1024
 
 run_func_512: func_512

Makefile

@@ -110,15 +110,40 @@ acvp_mlkem1024: $(OBJ_FILES_1024) $(MLKEM1024_BUILD_DIR)\test\acvp\acvp_mlkem.ob
     @if NOT EXIST $(MLKEM1024_BUILD_DIR)\bin mkdir $(MLKEM1024_BUILD_DIR)\bin
     $(CC) $(CFLAGS) /D MLK_CONFIG_PARAMETER_SET=1024 /Fe$(MLKEM1024_BUILD_DIR)\bin\acvp_mlkem1024 $** /link
 
+# compile KAT generator for mlkem512
+gen_KAT512: $(OBJ_FILES_512) $(MLKEM512_BUILD_DIR)\test\gen_KAT.obj $(BUILD_DIR)\randombytes\notrandombytes.obj
+    @if NOT EXIST $(MLKEM512_BUILD_DIR)\bin mkdir $(MLKEM512_BUILD_DIR)\bin
+    $(CC) $(CFLAGS) /D MLK_CONFIG_PARAMETER_SET=512 /Fe$(MLKEM512_BUILD_DIR)\bin\gen_KAT512 $** /link
+
+# compile KAT generator for mlkem768
+gen_KAT768: $(OBJ_FILES_768) $(MLKEM768_BUILD_DIR)\test\gen_KAT.obj $(BUILD_DIR)\randombytes\notrandombytes.obj
+    @if NOT EXIST $(MLKEM768_BUILD_DIR)\bin mkdir $(MLKEM768_BUILD_DIR)\bin
+    $(CC) $(CFLAGS) /D MLK_CONFIG_PARAMETER_SET=768 /Fe$(MLKEM768_BUILD_DIR)\bin\gen_KAT768 $** /link
+
+# compile KAT generator for mlkem1024
+gen_KAT1024: $(OBJ_FILES_1024) $(MLKEM1024_BUILD_DIR)\test\gen_KAT.obj $(BUILD_DIR)\randombytes\notrandombytes.obj
+    @if NOT EXIST $(MLKEM1024_BUILD_DIR)\bin mkdir $(MLKEM1024_BUILD_DIR)\bin
+    $(CC) $(CFLAGS) /D MLK_CONFIG_PARAMETER_SET=1024 /Fe$(MLKEM1024_BUILD_DIR)\bin\gen_KAT1024 $** /link
+
 acvp: acvp_mlkem512 acvp_mlkem768 acvp_mlkem1024
 
+gen_KAT: gen_KAT512 gen_KAT768 gen_KAT1024
+
+run_kat: gen_KAT
+    python test/src/kat_client.py
+
 run_acvp: acvp
     python test/acvp/acvp_client.py
 
-quickcheck: test_mlkem512 test_mlkem768 test_mlkem1024 run_acvp
+run_func: test_mlkem512 test_mlkem768 test_mlkem1024
     $(MLKEM512_BUILD_DIR)\bin\test_mlkem512.exe
-	$(MLKEM768_BUILD_DIR)\bin\test_mlkem768.exe
-	$(MLKEM1024_BUILD_DIR)\bin\test_mlkem1024.exe
+    $(MLKEM768_BUILD_DIR)\bin\test_mlkem768.exe
+    $(MLKEM1024_BUILD_DIR)\bin\test_mlkem1024.exe
+
+test: run_func run_acvp run_kat
+    @echo   Everything checks fine!
+
+quickcheck: test
 
 clean:
     -DEL $(BUILD_DIR)

Makefile.Microsoft_nmake

@@ -0,0 +1,100 @@
+#!/usr/bin/env python3
+# Copyright (c) The mlkem-native project authors
+# SPDX-License-Identifier: Apache-2.0 OR ISC OR MIT
+
+import hashlib
+import os
+import subprocess
+import sys
+import argparse
+from pathlib import Path
+
+
+# Check if we need to use a wrapper for execution (e.g. QEMU)
+exec_prefix = os.environ.get("EXEC_WRAPPER", "")
+exec_prefix = exec_prefix.split(" ") if exec_prefix != "" else []
+
+
+def err(msg, **kwargs):
+    print(msg, file=sys.stderr, **kwargs)
+
+
+def info(msg, **kwargs):
+    print(msg, **kwargs)
+
+
+def read_meta_hashes():
+    hashes = {}
+    current_name = None
+    with open("META.yml") as f:
+        for line in f:
+            line = line.strip()
+            if line.startswith("- name:"):
+                current_name = line.split(":", 1)[1].strip()
+            elif line.startswith("kat-sha256:") and current_name:
+                hashes[current_name] = line.split(":", 1)[1].strip()
+    return hashes
+
+
+def get_kat_binary(level):
+    suffix = ".exe" if sys.platform == "win32" else ""
+    return Path("test/build") / f"mlkem{level}" / "bin" / f"gen_KAT{level}{suffix}"
+
+
+def run_kat_single(level, ref_hash):
+    scheme_name = f"ML-KEM-{level}"
+    binary = get_kat_binary(level)
+
+    if not binary.exists():
+        err(f"Binary not found: {binary}")
+        return False
+
+    cmd = exec_prefix + [str(binary)]
+    result = subprocess.run(cmd, capture_output=True)
+
+    if result.returncode != 0:
+        err("FAIL!")
+        err(f"{cmd} failed with error code {result.returncode}")
+        err(result.stderr.decode("utf-8", errors="replace"))
+        return False
+
+    computed = hashlib.sha256(result.stdout).hexdigest()
+
+    if computed == ref_hash:
+        info(f"META.yml {scheme_name} kat-sha256: OK")
+        return True
+    else:
+        err(f"META.yml {scheme_name} kat-sha256: FAIL ({ref_hash} != {computed})")
+        return False
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--scheme",
+        choices=["512", "768", "1024"],
+        help="Run KAT for only one parameter set (default: all)",
+    )
+    args = parser.parse_args()
+
+    levels = [int(args.scheme)] if args.scheme else [512, 768, 1024]
+    ref_hashes = read_meta_hashes()
+
+    failed = False
+    for level in levels:
+        scheme_name = f"ML-KEM-{level}"
+        ref = ref_hashes.get(scheme_name)
+        if ref is None:
+            err(f"META.yml: no kat-sha256 entry for {scheme_name}")
+            failed = True
+            continue
+        if not run_kat_single(level, ref):
+            failed = True
+
+    if failed:
+        sys.exit(1)
+    info("ALL GOOD!")
+
+
+if __name__ == "__main__":
+    main()