Test mbedtls_mpi_fill_random
Positive tests: test that the RNG has the expected size, given that we
know how many leading zeros it has because we know how the function
consumes bytes and when the test RNG produces null bytes.
Negative tests: test that if the RNG is willing to emit less than the
number of wanted bytes, the function fails.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index 202df1d..3aebd6c 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -941,6 +941,48 @@
Test bit set (Invalid bit value)
mbedtls_mpi_set_bit:16:"00":5:2:16:"00":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
+Fill random: 0 bytes
+mpi_fill_random:0:0:0
+
+Fill random: 1 byte, good
+mpi_fill_random:1:1:0
+
+Fill random: 2 bytes, good, no leading zero
+mpi_fill_random:2:2:0
+
+Fill random: 2 bytes, good, 1 leading zero
+mpi_fill_random:2:256:0
+
+Fill random: MAX_SIZE - 7, good
+mpi_fill_random:MBEDTLS_MPI_MAX_SIZE - 7:MBEDTLS_MPI_MAX_SIZE - 7:0
+
+Fill random: MAX_SIZE, good
+mpi_fill_random:MBEDTLS_MPI_MAX_SIZE:MBEDTLS_MPI_MAX_SIZE:0
+
+Fill random: 1 byte, RNG failure
+mpi_fill_random:1:0:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
+Fill random: 2 bytes, RNG failure after 1 byte
+mpi_fill_random:2:1:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
+Fill random: 4 bytes, RNG failure after 3 bytes
+mpi_fill_random:4:3:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
+Fill random: 8 bytes, RNG failure after 7 bytes
+mpi_fill_random:8:7:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
+Fill random: 16 bytes, RNG failure after 1 bytes
+mpi_fill_random:16:1:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
+Fill random: 16 bytes, RNG failure after 8 bytes
+mpi_fill_random:16:8:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
+Fill random: 16 bytes, RNG failure after 15 bytes
+mpi_fill_random:16:15:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
+Fill random: MAX_SIZE bytes, RNG failure after MAX_SIZE-1 bytes
+mpi_fill_random:MBEDTLS_MPI_MAX_SIZE:MBEDTLS_MPI_MAX_SIZE-1:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
MPI Selftest
depends_on:MBEDTLS_SELF_TEST
mpi_selftest:
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index e54aaff..b3c5cba 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -1,5 +1,6 @@
/* BEGIN_HEADER */
#include "mbedtls/bignum.h"
+#include "mbedtls/entropy.h"
typedef struct mbedtls_test_mpi_random
{
@@ -43,6 +44,22 @@
return( 0 );
}
+
+/* Random generator that is told how many bytes to return. */
+static int f_rng_bytes_left( void *state, unsigned char *buf, size_t len )
+{
+ size_t *bytes_left = state;
+ size_t i;
+ for( i = 0; i < len; i++ )
+ {
+ if( *bytes_left == 0 )
+ return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
+ buf[i] = *bytes_left & 0xff;
+ --( *bytes_left );
+ }
+ return( 0 );
+}
+
/* END_HEADER */
/* BEGIN_DEPENDENCIES
@@ -1308,6 +1325,37 @@
}
/* END_CASE */
+/* BEGIN_CASE */
+void mpi_fill_random( int wanted_bytes, int rng_bytes, int expected_ret )
+{
+ mbedtls_mpi X;
+ int ret;
+ size_t bytes_left = rng_bytes;
+ mbedtls_mpi_init( &X );
+
+ ret = mbedtls_mpi_fill_random( &X, wanted_bytes,
+ f_rng_bytes_left, &bytes_left );
+ TEST_ASSERT( ret == expected_ret );
+
+ if( expected_ret == 0 )
+ {
+ /* mbedtls_mpi_fill_random is documented to use bytes from the RNG
+ * as a big-endian representation of the number. We know when
+ * our RNG function returns null bytes, so we know how many
+ * leading zero bytes the number has. */
+ size_t leading_zeros = 0;
+ if( wanted_bytes > 0 && rng_bytes % 256 == 0 )
+ leading_zeros = 1;
+ TEST_ASSERT( mbedtls_mpi_size( &X ) + leading_zeros ==
+ (size_t) wanted_bytes );
+ TEST_ASSERT( (int) bytes_left == rng_bytes - wanted_bytes );
+ }
+
+exit:
+ mbedtls_mpi_free( &X );
+}
+/* END_CASE */
+
/* BEGIN_CASE depends_on:MBEDTLS_SELF_TEST */
void mpi_selftest( )
{