Serial FIPS202: Adapt mld_polyvecl_uniform_gamma1

This commit changes mld_polyvecl_uniform_gamma1 to only use
mld_poly_uniform_gamma1 in case MLD_CONFIG_SERIAL_FIPS202_ONLY is set.

An additional CBMC proof is added that proves the function in case the
option is enabled.

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

Author: mkannwischer

mldsa/poly_kl.c

@@ -432,6 +432,8 @@ void mld_poly_uniform_gamma1(mld_poly *a, const uint8_t seed[MLDSA_CRHBYTES],
   mld_zeroize(extseed, sizeof(extseed));
 }
 
+
+#if !defined(MLD_CONFIG_SERIAL_FIPS202_ONLY)
 MLD_INTERNAL_API
 void mld_poly_uniform_gamma1_4x(mld_poly *r0, mld_poly *r1, mld_poly *r2,
                                 mld_poly *r3,
@@ -480,6 +482,7 @@ void mld_poly_uniform_gamma1_4x(mld_poly *r0, mld_poly *r1, mld_poly *r2,
   mld_zeroize(buf, sizeof(buf));
   mld_zeroize(extseed, sizeof(extseed));
 }
+#endif /* !MLD_CONFIG_SERIAL_FIPS202_ONLY */
 
 MLD_INTERNAL_API
 void mld_poly_challenge(mld_poly *c, const uint8_t seed[MLDSA_CTILDEBYTES])

mldsa/polyvec.c

@@ -157,10 +157,20 @@ void mld_polyvecl_uniform_gamma1(mld_polyvecl *v,
                                  const uint8_t seed[MLDSA_CRHBYTES],
                                  uint16_t nonce)
 {
+#if defined(MLD_CONFIG_SERIAL_FIPS202_ONLY)
+  int i;
+#endif
+
   /* Safety: nonce is at most ((UINT16_MAX - MLDSA_L) / MLDSA_L), and, hence,
    * this cast is safe. See NONCE_UB comment in sign.c. */
   nonce = (uint16_t)(MLDSA_L * nonce);
   /* Now, nonce <= UINT16_MAX - (MLDSA_L - 1), so the casts below are safe. */
+#if defined(MLD_CONFIG_SERIAL_FIPS202_ONLY)
+  for (i = 0; i < MLDSA_L; i++)
+  {
+    mld_poly_uniform_gamma1(&v->vec[i], seed, (uint16_t)(nonce + i));
+  }
+#else /* MLD_CONFIG_SERIAL_FIPS202_ONLY */
 #if MLDSA_L == 4
   mld_poly_uniform_gamma1_4x(&v->vec[0], &v->vec[1], &v->vec[2], &v->vec[3],
                              seed, nonce, (uint16_t)(nonce + 1),
@@ -179,6 +189,7 @@ void mld_polyvecl_uniform_gamma1(mld_polyvecl *v,
                              seed, (uint16_t)(nonce + 3), (uint16_t)(nonce + 4),
                              (uint16_t)(nonce + 5), (uint16_t)(nonce + 6));
 #endif /* MLDSA_L == 7 */
+#endif /* !MLD_CONFIG_SERIAL_FIPS202_ONLY */
 
   mld_assert_bound_2d(v->vec, MLDSA_L, MLDSA_N, -(MLDSA_GAMMA1 - 1),
                       MLDSA_GAMMA1 + 1);

proofs/cbmc/polyvecl_uniform_gamma1_serial/Makefile

@@ -0,0 +1,57 @@
+# Copyright (c) The mldsa-native project authors
+# SPDX-License-Identifier: Apache-2.0 OR ISC OR MIT
+
+include ../Makefile_params.common
+
+HARNESS_ENTRY = harness
+HARNESS_FILE = polyvecl_uniform_gamma1_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 = polyvecl_uniform_gamma1_serial
+
+DEFINES += -DMLD_CONFIG_SERIAL_FIPS202_ONLY
+INCLUDES +=
+
+REMOVE_FUNCTION_BODY +=
+
+UNWINDSET += $(MLD_NAMESPACE)polyvecl_uniform_gamma1.0:7 # Largest value of MLDSA_L
+
+PROOF_SOURCES += $(PROOFDIR)/$(HARNESS_FILE).c
+PROJECT_SOURCES += $(SRCDIR)/mldsa/polyvec.c
+
+CHECK_FUNCTION_CONTRACTS=$(MLD_NAMESPACE)polyvecl_uniform_gamma1
+USE_FUNCTION_CONTRACTS=$(MLD_NAMESPACE)poly_uniform_gamma1
+
+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 = polyvecl_uniform_gamma1_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
+# 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 = 10
+
+# 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
+# ("mldsa/poly.c") in PROJECT_SOURCES).
+# REWRITTEN_SOURCES = $(PROOFDIR)/<__SOURCE_FILE_BASENAME__>.i
+# include ../Makefile.common
+# $(PROOFDIR)/<__SOURCE_FILE_BASENAME__>.i_SOURCE = $(SRCDIR)/mldsa/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/polyvecl_uniform_gamma1_serial/polyvecl_uniform_gamma1_harness.c

@@ -0,0 +1,13 @@
+// Copyright (c) The mldsa-native project authors
+// SPDX-License-Identifier: Apache-2.0 OR ISC OR MIT
+
+#include "polyvec.h"
+
+void harness(void)
+{
+  mld_polyvecl *v;
+  const uint8_t *seed;
+  uint16_t nonce;
+
+  mld_polyvecl_uniform_gamma1(v, seed, nonce);
+}