CBMC: Add proofs on top of native functions (keccakf1600x4_permute_native)

- This commit adds CBMC proofs for following the native function:
 `mld_keccak_f1600_x4_native`, called `keccakf1600x4_permute_native`.

- This following changes are include:

 - Apply the same harness file and construct function contract reference
  from `keccakf1600x4_permute`.

 - Use the following function contracts:
  - `mld_keccak_f1600_x4_native`

 - Add `MLD_USE_FIPS202_X4_NATIVE` in dummy_backend_fips202_x4.h

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

Author: willieyz

mldsa/src/fips202/native/api.h

@@ -55,7 +55,13 @@ __contract__(
 );
 #endif /* MLD_USE_FIPS202_X1_NATIVE */
 #if defined(MLD_USE_FIPS202_X4_NATIVE)
-static MLD_INLINE int mld_keccak_f1600_x4_native(uint64_t *state);
-#endif
+static MLD_INLINE int mld_keccak_f1600_x4_native(uint64_t *state)
+__contract__(
+    requires(memory_no_alias(state, sizeof(uint64_t) * 25 * 4))
+    assigns(memory_slice(state, sizeof(uint64_t) * 25 * 4))
+    ensures(return_value == MLD_NATIVE_FUNC_FALLBACK || return_value == MLD_NATIVE_FUNC_SUCCESS)
+    ensures((return_value == MLD_NATIVE_FUNC_FALLBACK) ==> array_unchanged_u64(state, 25 * 4))
+);
+#endif /* MLD_USE_FIPS202_X4_NATIVE */
 
 #endif /* !MLD_FIPS202_NATIVE_API_H */

proofs/cbmc/dummy_backend_fips202_x4.h

@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) The mldsa-native project authors
+ * SPDX-License-Identifier: Apache-2.0 OR ISC OR MIT
+ */
+
+#ifndef MLD_DUMMY_FIPS202X4_BACKEND_H
+#define MLD_DUMMY_FIPS202X4_BACKEND_H
+
+
+#define MLD_USE_FIPS202_X4_NATIVE
+
+#include "../../mldsa/src/fips202/native/api.h"
+
+#endif /* !MLD_DUMMY_FIPS202X4_BACKEND_H */

proofs/cbmc/keccakf1600x4_permute_native/Makefile

@@ -0,0 +1,67 @@
+# Copyright (c) The mldsa-native project authors
+# Copyright (c) The mlkem-native project authors
+# SPDX-License-Identifier: Apache-2.0 OR ISC OR MIT
+
+include ../Makefile_params.common
+
+HARNESS_ENTRY = harness
+HARNESS_FILE = keccakf1600x4_permute_native_harness
+
+# This should be a unique identifier for this proof, and will appear on the
+# Litani dashboard. It can be human-readable and contain spaces if you wish.
+PROOF_UID = keccakf1600x4_permute_native
+
+DEFINES += -DMLD_CONFIG_USE_NATIVE_BACKEND_FIPS202 -DMLD_CONFIG_FIPS202_BACKEND_FILE="\"dummy_backend_fips202_x4.h\""
+INCLUDES +=
+
+REMOVE_FUNCTION_BODY +=
+UNWINDSET +=
+
+PROOF_SOURCES += $(PROOFDIR)/$(HARNESS_FILE).c
+PROJECT_SOURCES += $(SRCDIR)/mldsa/src/fips202/keccakf1600.c
+
+CHECK_FUNCTION_CONTRACTS=$(MLD_NAMESPACE)keccakf1600x4_permute
+USE_FUNCTION_CONTRACTS=mld_keccak_f1600_x4_native
+APPLY_LOOP_CONTRACTS=on
+USE_DYNAMIC_FRAMES=1
+
+# Disable any setting of EXTERNAL_SAT_SOLVER, and choose SMT backend instead
+EXTERNAL_SAT_SOLVER=
+CBMCFLAGS=--smt2
+
+# For this proof we tell CBMC to
+#  - not decompose arrays into their individual cells
+#  - to slice constraints that are not in the cone of influence of the proof obligations
+# These options simplify them modelling of arrays and produce much more compact
+# SMT files, leaving all array-type reasoning to the SMT solver.
+#
+# For functions that use large and multi-dimensional arrays, this yields
+# a substantial improvement in proof performance.
+CBMCFLAGS += --no-array-field-sensitivity
+CBMCFLAGS += --slice-formula
+
+FUNCTION_NAME = mld_keccakf1600x4_permute_native
+
+# If this proof is found to consume huge amounts of RAM, you can set the
+# EXPENSIVE variable. With new enough versions of the proof tools, this will
+# restrict the number of EXPENSIVE CBMC jobs running at once. See the
+# documentation in Makefile.common under the "Job Pools" heading for details.
+# EXPENSIVE = true
+
+# This function is large enough to need...
+CBMC_OBJECT_BITS = 8
+
+# If you require access to a file-local ("static") function or object to conduct
+# your proof, set the following (and do not include the original source file
+# ("mlkem/poly.c") in PROJECT_SOURCES).
+# REWRITTEN_SOURCES = $(PROOFDIR)/<__SOURCE_FILE_BASENAME__>.i
+# include ../Makefile.common
+# $(PROOFDIR)/<__SOURCE_FILE_BASENAME__>.i_SOURCE = $(SRCDIR)/mlkem/poly.c
+# $(PROOFDIR)/<__SOURCE_FILE_BASENAME__>.i_FUNCTIONS = foo bar
+# $(PROOFDIR)/<__SOURCE_FILE_BASENAME__>.i_OBJECTS = baz
+# Care is required with variables on the left-hand side: REWRITTEN_SOURCES must
+# be set before including Makefile.common, but any use of variables on the
+# left-hand side requires those variables to be defined. Hence, _SOURCE,
+# _FUNCTIONS, _OBJECTS is set after including Makefile.common.
+
+include ../Makefile.common

proofs/cbmc/keccakf1600x4_permute_native/keccakf1600x4_permute_native_harness.c

@@ -0,0 +1,12 @@
+// Copyright (c) The mldsa-native project authors
+// Copyright (c) The mlkem-native project authors
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: MIT-0
+
+#include <keccakf1600.h>
+
+void harness(void)
+{
+  uint64_t *s;
+  mld_keccakf1600x4_permute(s);
+}