Implement and test mbedtls_mpi_mod_raw_random
In the basic/XXX=core test cases, use odd upper bounds, because the mod
version of random() only supports odd upper bounds (the upper bound is a
modulus and the mod modules only support odd moduli).
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/bignum_mod_raw.c b/library/bignum_mod_raw.c
index c98a1c1..fbd90bf 100644
--- a/library/bignum_mod_raw.c
+++ b/library/bignum_mod_raw.c
@@ -176,6 +176,18 @@
/* BEGIN MERGE SLOT 6 */
+int mbedtls_mpi_mod_raw_random( mbedtls_mpi_uint *X,
+ mbedtls_mpi_uint min,
+ const mbedtls_mpi_mod_modulus *N,
+ int (*f_rng)(void *, unsigned char *, size_t),
+ void *p_rng )
+{
+ int ret = mbedtls_mpi_core_random( X, min, N->p, N->limbs, f_rng, p_rng );
+ if( ret != 0 )
+ return( ret );
+ return( mbedtls_mpi_mod_raw_to_mont_rep( X, N ) );
+}
+
/* END MERGE SLOT 6 */
/* BEGIN MERGE SLOT 7 */
diff --git a/library/bignum_mod_raw.h b/library/bignum_mod_raw.h
index e6237b3..87e241f 100644
--- a/library/bignum_mod_raw.h
+++ b/library/bignum_mod_raw.h
@@ -297,6 +297,40 @@
/* BEGIN MERGE SLOT 6 */
+/** Generate a random number uniformly in a range.
+ *
+ * This function generates a random number between \p min inclusive and
+ * \p N exclusive.
+ *
+ * The procedure complies with RFC 6979 §3.3 (deterministic ECDSA)
+ * when the RNG is a suitably parametrized instance of HMAC_DRBG
+ * and \p min is \c 1.
+ *
+ * \note There are `N - min` possible outputs. The lower bound
+ * \p min can be reached, but the upper bound \p N cannot.
+ *
+ * \param X The destination MPI, in canonical representation modulo \p N.
+ * It must not be aliased with \p N or otherwise overlap it.
+ * \param min The minimum value to return. It must be strictly smaller
+ * than \b N.
+ * \param N The modulus.
+ * This is the upper bound of the output range, exclusive.
+ * \param f_rng The RNG function to use. This must not be \c NULL.
+ * \param p_rng The RNG parameter to be passed to \p f_rng.
+ *
+ * \return \c 0 if successful.
+ * \return #MBEDTLS_ERR_MPI_NOT_ACCEPTABLE if the implementation was
+ * unable to find a suitable value within a limited number
+ * of attempts. This has a negligible probability if \p N
+ * is significantly larger than \p min, which is the case
+ * for all usual cryptographic applications.
+ */
+int mbedtls_mpi_mod_raw_random( mbedtls_mpi_uint *X,
+ mbedtls_mpi_uint min,
+ const mbedtls_mpi_mod_modulus *N,
+ int (*f_rng)(void *, unsigned char *, size_t),
+ void *p_rng );
+
/* END MERGE SLOT 6 */
/* BEGIN MERGE SLOT 7 */
diff --git a/tests/suites/test_suite_bignum_random.data b/tests/suites/test_suite_bignum_random.data
index bf51b0f..b51254b 100644
--- a/tests/suites/test_suite_bignum_random.data
+++ b/tests/suites/test_suite_bignum_random.data
@@ -17,31 +17,43 @@
mpi_core_random_basic:0x40000000:"0200000000000000000000000000000000":0
# Use the same data values for mpi_core_random_basic->NOT_ACCEPTABLE
-# and for mpi_legacy_random_values where we want to return NOT_ACCEPTABLE
+# and for mpi_XXX_random_values where we want to return NOT_ACCEPTABLE
# but this isn't checked at runtime.
-MPI core random basic: 2^28-1..2^28 (NOT_ACCEPTABLE)
-mpi_core_random_basic:0x0fffffff:"10000000":MBEDTLS_ERR_MPI_NOT_ACCEPTABLE
+MPI core random basic: 2^28-1..2^28+1 (NOT_ACCEPTABLE)
+mpi_core_random_basic:0x0fffffff:"10000001":MBEDTLS_ERR_MPI_NOT_ACCEPTABLE
-MPI random legacy=core: 2^28-1..2^28 (NOT_ACCEPTABLE)
-mpi_legacy_random_values:0x0fffffff:"10000000"
+MPI random legacy=core: 2^28-1..2^28+1 (NOT_ACCEPTABLE)
+mpi_legacy_random_values:0x0fffffff:"10000001"
-MPI core random basic: 2^29-1..2^29 (NOT_ACCEPTABLE)
-mpi_core_random_basic:0x1fffffff:"20000000":MBEDTLS_ERR_MPI_NOT_ACCEPTABLE
+MPI random mod=core: 2^28-1..2^28+1 (NOT_ACCEPTABLE)
+mpi_mod_random_values:0x0fffffff:"10000001"
-MPI random legacy=core: 2^29-1..2^29 (NOT_ACCEPTABLE)
-mpi_legacy_random_values:0x1fffffff:"20000000"
+MPI core random basic: 2^29-1..2^29+1 (NOT_ACCEPTABLE)
+mpi_core_random_basic:0x1fffffff:"20000001":MBEDTLS_ERR_MPI_NOT_ACCEPTABLE
-MPI core random basic: 2^30-1..2^30 (NOT_ACCEPTABLE)
-mpi_core_random_basic:0x3fffffff:"40000000":MBEDTLS_ERR_MPI_NOT_ACCEPTABLE
+MPI random legacy=core: 2^29-1..2^29+1 (NOT_ACCEPTABLE)
+mpi_legacy_random_values:0x1fffffff:"20000001"
-MPI random legacy=core: 2^30-1..2^30 (NOT_ACCEPTABLE)
-mpi_legacy_random_values:0x3fffffff:"40000000"
+MPI random mod=core: 2^29-1..2^29+1 (NOT_ACCEPTABLE)
+mpi_mod_random_values:0x1fffffff:"20000001"
-MPI core random basic: 2^31-1..2^31 (NOT_ACCEPTABLE)
-mpi_core_random_basic:0x7fffffff:"80000000":MBEDTLS_ERR_MPI_NOT_ACCEPTABLE
+MPI core random basic: 2^30-1..2^30+1 (NOT_ACCEPTABLE)
+mpi_core_random_basic:0x3fffffff:"40000001":MBEDTLS_ERR_MPI_NOT_ACCEPTABLE
-MPI random legacy=core: 2^31-1..2^31 (NOT_ACCEPTABLE)
-mpi_legacy_random_values:0x7fffffff:"80000000"
+MPI random legacy=core: 2^30-1..2^30+1 (NOT_ACCEPTABLE)
+mpi_legacy_random_values:0x3fffffff:"40000001"
+
+MPI random mod=core: 2^30-1..2^30+1 (NOT_ACCEPTABLE)
+mpi_mod_random_values:0x3fffffff:"40000001"
+
+MPI core random basic: 2^31-1..2^31+1 (NOT_ACCEPTABLE)
+mpi_core_random_basic:0x7fffffff:"80000001":MBEDTLS_ERR_MPI_NOT_ACCEPTABLE
+
+MPI random legacy=core: 2^31-1..2^31+1 (NOT_ACCEPTABLE)
+mpi_legacy_random_values:0x7fffffff:"80000001"
+
+MPI random mod=core: 2^31-1..2^31+1 (NOT_ACCEPTABLE)
+mpi_mod_random_values:0x7fffffff:"80000001"
MPI random in range: 1..2
mpi_random_many:1:"02":1000
@@ -233,3 +245,21 @@
MPI random legacy=core: 0..2^256+1
mpi_legacy_random_values:0:"010000000000000000000000000000000000000000000000000000000000000001"
+
+MPI random mod=core: 0..1
+mpi_mod_random_values:0:"01"
+
+MPI random mod=core: 0..3
+mpi_mod_random_values:0:"03"
+
+MPI random mod=core: 1..3
+mpi_mod_random_values:1:"03"
+
+MPI random mod=core: 2^30..2^31-1
+mpi_mod_random_values:0x40000000:"7fffffff"
+
+MPI random mod=core: 2^31-1..2^32-1
+mpi_mod_random_values:0x7fffffff:"ffffffff"
+
+MPI random mod=core: 0..2^256+1
+mpi_mod_random_values:0:"010000000000000000000000000000000000000000000000000000000000000001"
diff --git a/tests/suites/test_suite_bignum_random.function b/tests/suites/test_suite_bignum_random.function
index 2250e8c..a837e1b 100644
--- a/tests/suites/test_suite_bignum_random.function
+++ b/tests/suites/test_suite_bignum_random.function
@@ -8,6 +8,7 @@
#include "mbedtls/bignum.h"
#include "mbedtls/entropy.h"
#include "bignum_core.h"
+#include "bignum_mod_raw.h"
#include "constant_time_internal.h"
/* This test suite only manipulates non-negative bignums. */
@@ -159,6 +160,61 @@
/* END_CASE */
/* BEGIN_CASE */
+void mpi_mod_random_values( int min, char *max_hex )
+{
+ /* Same RNG as in mpi_core_random_basic */
+ mbedtls_test_rnd_pseudo_info rnd_core = {
+ {'T', 'h', 'i', 's', ' ', 'i', ',', 'a',
+ 's', 'e', 'e', 'd', '!', 0},
+ 0, 0};
+ mbedtls_test_rnd_pseudo_info rnd_mod_raw;
+ memcpy( &rnd_mod_raw, &rnd_core, sizeof( rnd_core ) );
+ mbedtls_mpi_uint *R_core = NULL;
+ mbedtls_mpi_uint *R_mod_raw = NULL;
+ mbedtls_mpi_mod_modulus N;
+ mbedtls_mpi_mod_modulus_init( &N );
+
+ TEST_EQUAL( mbedtls_test_read_mpi_modulus( &N, max_hex,
+ MBEDTLS_MPI_MOD_REP_MONTGOMERY ),
+ 0 );
+ ASSERT_ALLOC( R_core, N.limbs );
+ ASSERT_ALLOC( R_mod_raw, N.limbs );
+
+ /* Call the core and mod random() functions with the same random stream. */
+ int core_ret = mbedtls_mpi_core_random( R_core,
+ min, N.p, N.limbs,
+ mbedtls_test_rnd_pseudo_rand,
+ &rnd_core );
+ int mod_raw_ret = mbedtls_mpi_mod_raw_random( R_mod_raw,
+ min, &N,
+ mbedtls_test_rnd_pseudo_rand,
+ &rnd_mod_raw );
+
+ /* They must return the same status, and, on success, output the
+ * same number, with the same limb count. */
+ TEST_EQUAL( core_ret, mod_raw_ret );
+ if( core_ret == 0 )
+ {
+ TEST_EQUAL( mbedtls_mpi_mod_raw_from_mont_rep( R_mod_raw, &N ), 0 );
+ ASSERT_COMPARE( R_core, N.limbs * ciL,
+ R_mod_raw, N.limbs * ciL );
+ }
+
+ /* Also check that they have consumed the RNG in the same way. */
+ /* This may theoretically fail on rare platforms with padding in
+ * the structure! If this is a problem in practice, change to a
+ * field-by-field comparison. */
+ ASSERT_COMPARE( &rnd_core, sizeof( rnd_core ),
+ &rnd_mod_raw, sizeof( rnd_mod_raw ) );
+
+exit:
+ mbedtls_mpi_mod_modulus_free( &N );
+ mbedtls_free( R_core );
+ mbedtls_free( R_mod_raw );
+}
+/* END_CASE */
+
+/* BEGIN_CASE */
void mpi_random_many( int min, char *bound_hex, int iterations )
{
/* Generate numbers in the range 1..bound-1. Do it iterations times.