CBMC: Add proof and spec for mld_shake256x4_squeezeblocks

Resolves #247

Signed-off-by: Matthias J. Kannwischer <[email protected]>

Author: mkannwischer

mldsa/fips202/fips202x4.h

@@ -80,7 +80,20 @@ __contract__(
 #define mld_shake256x4_squeezeblocks FIPS202_NAMESPACE(shake256x4_squeezeblocks)
 void mld_shake256x4_squeezeblocks(uint8_t *out0, uint8_t *out1, uint8_t *out2,
                                   uint8_t *out3, size_t nblocks,
-                                  mld_shake256x4ctx *state);
+                                  mld_shake256x4ctx *state)
+__contract__(
+  requires(nblocks <= 8 /* somewhat arbitrary bound */)
+  requires(memory_no_alias(state, sizeof(mld_shake256x4ctx)))
+  requires(memory_no_alias(out0, nblocks * SHAKE256_RATE))
+  requires(memory_no_alias(out1, nblocks * SHAKE256_RATE))
+  requires(memory_no_alias(out2, nblocks * SHAKE256_RATE))
+  requires(memory_no_alias(out3, nblocks * SHAKE256_RATE))
+  assigns(memory_slice(out0, nblocks * SHAKE256_RATE),
+    memory_slice(out1, nblocks * SHAKE256_RATE),
+    memory_slice(out2, nblocks * SHAKE256_RATE),
+    memory_slice(out3, nblocks * SHAKE256_RATE),
+    object_whole(state))
+);
 
 #define mld_shake256x4_init FIPS202_NAMESPACE(shake256x4_init)
 void mld_shake256x4_init(mld_shake256x4ctx *state);

proofs/cbmc/shake256x4_squeezeblocks/Makefile

@@ -0,0 +1,56 @@
+# 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 = shake256x4_squeezeblocks_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 = shake256x4_squeezeblocks
+
+DEFINES +=
+INCLUDES +=
+
+REMOVE_FUNCTION_BODY +=
+UNWINDSET +=
+
+PROOF_SOURCES += $(PROOFDIR)/$(HARNESS_FILE).c
+PROJECT_SOURCES += $(SRCDIR)/mldsa/fips202/fips202x4.c
+
+CHECK_FUNCTION_CONTRACTS=$(FIPS202_NAMESPACE)shake256x4_squeezeblocks
+USE_FUNCTION_CONTRACTS=mld_keccak_squeezeblocks_x4
+APPLY_LOOP_CONTRACTS=on
+USE_DYNAMIC_FRAMES=1
+
+# Disable any setting of EXTERNAL_SAT_SOLVER, and choose SMT backend instead
+EXTERNAL_SAT_SOLVER=
+CBMCFLAGS=--bitwuzla
+
+FUNCTION_NAME = mld_shake256x4_squeezeblocks
+
+# 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/shake256x4_squeezeblocks/shake256x4_squeezeblocks_harness.c

@@ -0,0 +1,18 @@
+// 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 <fips202x4.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+
+void harness(void)
+{
+  uint8_t *output0, output1, output2, output3;
+  size_t nblocks;
+  mld_shake256x4ctx *state;
+  mld_shake256x4_squeezeblocks(output0, output1, output2, output3, nblocks,
+                               state);
+}