Adjust CBMC proof to modified gen_matrix

Signed-off-by: Hanno Becker <[email protected]>

Author: hanno-becker

mlkem/src/indcpa.c

@@ -39,6 +39,8 @@
 #define mlk_pack_ciphertext MLK_ADD_PARAM_SET(mlk_pack_ciphertext)
 #define mlk_unpack_ciphertext MLK_ADD_PARAM_SET(mlk_unpack_ciphertext)
 #define mlk_matvec_mul MLK_ADD_PARAM_SET(mlk_matvec_mul)
+#define mlk_polymat_permute_bitrev_to_custom \
+  MLK_ADD_PARAM_SET(mlk_polymat_permute_bitrev_to_custom)
 /* End of parameter set namespacing */
 
 /*************************************************
@@ -175,21 +177,40 @@ static void mlk_unpack_ciphertext(mlk_polyvec b, mlk_poly *v,
   mlk_poly_decompress_dv(v, c + MLKEM_POLYVECCOMPRESSEDBYTES_DU);
 }
 
-#if !defined(MLK_USE_NATIVE_NTT_CUSTOM_ORDER)
-/* This namespacing is not done at the top to avoid a naming conflict
- * with native backends, which are currently not yet namespaced. */
-#define mlk_poly_permute_bitrev_to_custom \
-  MLK_ADD_PARAM_SET(mlk_poly_permute_bitrev_to_custom)
-
-static MLK_INLINE void mlk_poly_permute_bitrev_to_custom(int16_t data[MLKEM_N])
+/* Helper function to ensure that the polynomial entries in the output
+ * of gen_matrix use the standard (bitreversed) ordering of coefficients.
+ * No-op unless a native backend with a custom ordering is used.
+ *
+ * We don't inline this into gen_matrix to avoid having to split the CBMC
+ * proof for gen_matrix based on MLK_USE_NATIVE_NTT_CUSTOM_ORDER. */
+static void mlk_polymat_permute_bitrev_to_custom(mlk_polymat a)
 __contract__(
   /* We don't specify that this should be a permutation, but only
    * that it does not change the bound established at the end of mlk_gen_matrix. */
-  requires(memory_no_alias(data, sizeof(int16_t) * MLKEM_N))
-  requires(array_bound(data, 0, MLKEM_N, 0, MLKEM_Q))
-  assigns(memory_slice(data, sizeof(mlk_poly)))
-  ensures(array_bound(data, 0, MLKEM_N, 0, MLKEM_Q))) { ((void)data); }
+ requires(memory_no_alias(a, sizeof(mlk_polymat)))
+ requires(forall(x, 0, MLKEM_K * MLKEM_K,
+   array_bound(a[x].coeffs, 0, MLKEM_N, 0, MLKEM_Q)))
+ assigns(object_whole(a))
+ ensures(forall(x, 0, MLKEM_K * MLKEM_K,
+   array_bound(a[x].coeffs, 0, MLKEM_N, 0, MLKEM_Q))))
+{
+#if defined(MLK_USE_NATIVE_NTT_CUSTOM_ORDER)
+  unsigned i;
+  for (i = 0; i < MLKEM_K * MLKEM_K; i++)
+  __loop__(
+     assigns(i, object_whole(a))
+     invariant(i <= MLKEM_K * MLKEM_K)
+     invariant(forall(x, 0, MLKEM_K * MLKEM_K,
+       array_bound(a[x].coeffs, 0, MLKEM_N, 0, MLKEM_Q)))
+     )
+  {
+    mlk_poly_permute_bitrev_to_custom(a[i].coeffs);
+  }
+#else  /* MLK_USE_NATIVE_NTT_CUSTOM_ORDER */
+  /* Nothing to do */
+  (void)a;
 #endif /* !MLK_USE_NATIVE_NTT_CUSTOM_ORDER */
+}
 
 /* Reference: `gen_matrix()` in the reference implementation @[REF].
  *            - We use a special subroutine to generate 4 polynomials
@@ -269,10 +290,7 @@ void mlk_gen_matrix(mlk_polymat a, const uint8_t seed[MLKEM_SYMBYTES],
    * The public matrix is generated in NTT domain. If the native backend
    * uses a custom order in NTT domain, permute A accordingly.
    */
-  for (i = 0; i < MLKEM_K * MLKEM_K; i++)
-  {
-    mlk_poly_permute_bitrev_to_custom(a[i].coeffs);
-  }
+  mlk_polymat_permute_bitrev_to_custom(a);
 
   /* Specification: Partially implements
    * @[FIPS203, Section 3.3, Destruction of intermediate values] */
@@ -524,4 +542,4 @@ void mlk_indcpa_dec(uint8_t m[MLKEM_INDCPA_MSGBYTES],
 #undef mlk_pack_ciphertext
 #undef mlk_unpack_ciphertext
 #undef mlk_matvec_mul
-#undef mlk_poly_permute_bitrev_to_custom
+#undef mlk_polymat_permute_bitrev_to_custom

proofs/cbmc/gen_matrix/Makefile

@@ -20,7 +20,7 @@ PROOF_SOURCES += $(PROOFDIR)/$(HARNESS_FILE).c
 PROJECT_SOURCES += $(SRCDIR)/mlkem/src/indcpa.c
 
 CHECK_FUNCTION_CONTRACTS=mlk_gen_matrix
-USE_FUNCTION_CONTRACTS=mlk_poly_rej_uniform mlk_poly_rej_uniform_x4 mlk_poly_permute_bitrev_to_custom mlk_zeroize
+USE_FUNCTION_CONTRACTS=mlk_poly_rej_uniform mlk_poly_rej_uniform_x4 mlk_polymat_permute_bitrev_to_custom mlk_zeroize
 APPLY_LOOP_CONTRACTS=on
 USE_DYNAMIC_FRAMES=1
 

proofs/cbmc/gen_matrix_native/Makefile renamed to proofs/cbmc/gen_matrix_serial/Makefile

@@ -4,31 +4,31 @@
 include ../Makefile_params.common
 
 HARNESS_ENTRY = harness
-HARNESS_FILE = gen_matrix_native_harness
+HARNESS_FILE = gen_matrix_serial_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 = gen_matrix_native
+PROOF_UID = mlk_gen_matrix_serial
 
-DEFINES += -DMLK_CONFIG_USE_NATIVE_BACKEND_ARITH -DMLK_CONFIG_ARITH_BACKEND_FILE="\"dummy_backend.h\""
+DEFINES += -DMLK_CONFIG_SERIAL_FIPS202_ONLY
 INCLUDES +=
 
 REMOVE_FUNCTION_BODY +=
-UNWINDSET += mlk_gen_matrix.0:4 mlk_gen_matrix.1:4 mlk_gen_matrix.2:4 mlk_gen_matrix.3:16
+UNWINDSET += mlk_gen_matrix.0:4 mlk_gen_matrix.1:16
 
 PROOF_SOURCES += $(PROOFDIR)/$(HARNESS_FILE).c
 PROJECT_SOURCES += $(SRCDIR)/mlkem/src/indcpa.c
 
 CHECK_FUNCTION_CONTRACTS=mlk_gen_matrix
-USE_FUNCTION_CONTRACTS=mlk_poly_rej_uniform mlk_poly_rej_uniform_x4 mlk_poly_permute_bitrev_to_custom
+USE_FUNCTION_CONTRACTS=mlk_poly_rej_uniform mlk_polymat_permute_bitrev_to_custom mlk_zeroize
 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
 
-FUNCTION_NAME = mlk_gen_matrix_native
+FUNCTION_NAME = mlk_gen_matrix_serial
 
 # 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

proofs/cbmc/gen_matrix_native/gen_matrix_native_harness.c renamed to proofs/cbmc/gen_matrix_serial/gen_matrix_serial_harness.c

@@ -4,11 +4,11 @@
 include ../Makefile_params.common
 
 HARNESS_ENTRY = harness
-HARNESS_FILE = poly_permute_bitrev_to_custom_harness
+HARNESS_FILE = polymat_permute_bitrev_to_custom_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 = mlk_poly_permute_bitrev_to_custom
+PROOF_UID = mlk_polymat_permute_bitrev_to_custom
 
 DEFINES +=
 INCLUDES +=
@@ -18,7 +18,7 @@ REMOVE_FUNCTION_BODY +=
 PROOF_SOURCES += $(PROOFDIR)/$(HARNESS_FILE).c
 PROJECT_SOURCES += $(SRCDIR)/mlkem/src/indcpa.c
 
-CHECK_FUNCTION_CONTRACTS=mlk_poly_permute_bitrev_to_custom
+CHECK_FUNCTION_CONTRACTS=mlk_polymat_permute_bitrev_to_custom
 USE_FUNCTION_CONTRACTS=
 APPLY_LOOP_CONTRACTS=on
 USE_DYNAMIC_FRAMES=1
@@ -38,7 +38,7 @@ CBMCFLAGS=--smt2
 CBMCFLAGS += --no-array-field-sensitivity
 CBMCFLAGS += --slice-formula
 
-FUNCTION_NAME = mlk_poly_permute_bitrev_to_custom
+FUNCTION_NAME = mlk_polymat_permute_bitrev_to_custom
 
 # 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

proofs/cbmc/poly_permute_bitrev_to_custom/Makefile renamed to proofs/cbmc/polymat_permute_bitrev_to_custom/Makefile

@@ -3,12 +3,12 @@
 // SPDX-License-Identifier: MIT-0
 
 #include <stdint.h>
-#include "params.h"
+#include "poly_k.h"
 
-void mlk_poly_permute_bitrev_to_custom(int16_t data[MLKEM_N]);
+void mlk_polymat_permute_bitrev_to_custom(mlk_polymat a);
 
 void harness(void)
 {
-  int16_t *data;
-  mlk_poly_permute_bitrev_to_custom(data);
+  mlk_poly *a;
+  mlk_polymat_permute_bitrev_to_custom(a);
 }

proofs/cbmc/poly_permute_bitrev_to_custom/poly_permute_bitrev_to_custom_harness.c renamed to proofs/cbmc/polymat_permute_bitrev_to_custom/polymat_permute_bitrev_to_custom_harness.c

@@ -0,0 +1,63 @@
+# 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 = polymat_permute_bitrev_to_custom_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 = mlk_polymat_permute_bitrev_to_custom_native
+
+DEFINES += -DMLK_CONFIG_USE_NATIVE_BACKEND_ARITH -DMLK_CONFIG_ARITH_BACKEND_FILE="\"dummy_backend.h\""
+INCLUDES +=
+
+REMOVE_FUNCTION_BODY +=
+
+PROOF_SOURCES += $(PROOFDIR)/$(HARNESS_FILE).c
+PROJECT_SOURCES += $(SRCDIR)/mlkem/src/indcpa.c
+
+CHECK_FUNCTION_CONTRACTS=mlk_polymat_permute_bitrev_to_custom
+USE_FUNCTION_CONTRACTS= mlk_poly_permute_bitrev_to_custom
+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 = mlk_polymat_permute_bitrev_to_custom_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
+CBMC_OBJECT_BITS = 11
+
+# 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/src/poly.c") in PROJECT_SOURCES).
+# REWRITTEN_SOURCES = $(PROOFDIR)/<__SOURCE_FILE_BASENAME__>.i
+# include ../Makefile.common
+# $(PROOFDIR)/<__SOURCE_FILE_BASENAME__>.i_SOURCE = $(SRCDIR)/mlkem/src/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/polymat_permute_bitrev_to_custom_native/Makefile

@@ -0,0 +1,14 @@
+// Copyright (c) The mlkem-native project authors
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: MIT-0
+
+#include <stdint.h>
+#include "poly_k.h"
+
+void mlk_polymat_permute_bitrev_to_custom(mlk_polymat a);
+
+void harness(void)
+{
+  mlk_poly *a;
+  mlk_polymat_permute_bitrev_to_custom(a);
+}

proofs/cbmc/polymat_permute_bitrev_to_custom_native/polymat_permute_bitrev_to_custom_native_harness.c

@@ -42,6 +42,9 @@ def gen_contracts():
 def is_exception(funcname):
     # The functions passing this filter are known not to have a proof
 
+    if funcname == 'poly_permute_bitrev_to_custom':
+        return True
+
     if funcname.endswith("_native") or funcname.endswith("_asm"):
         # CBMC proofs are axiomatized against contracts of the backends
         return True