From 8f814cddb94f4018646569143d10ebbb98daa454 Mon Sep 17 00:00:00 2001 From: Jonas Nick Date: Tue, 8 Oct 2019 09:11:16 +0000 Subject: [PATCH] Add test for boundary conditions of scalar_set_b32 with respect to overflows --- src/tests.c | 35 +++++++++++++++++++++++++++++++---- 1 file changed, 31 insertions(+), 4 deletions(-) diff --git a/src/tests.c b/src/tests.c index 0a0cb52..ef166e4 100644 --- a/src/tests.c +++ b/src/tests.c @@ -1123,16 +1123,43 @@ void run_scalar_tests(void) { #ifndef USE_NUM_NONE { - /* A scalar with value of the curve order should be 0. */ + /* Test secp256k1_scalar_set_b32 boundary conditions */ secp256k1_num order; - secp256k1_scalar zero; + secp256k1_scalar scalar; unsigned char bin[32]; + unsigned char bin_tmp[32]; int overflow = 0; + /* 2^256-1 - order */ + static const secp256k1_scalar all_ones_minus_order = SECP256K1_SCALAR_CONST( + 0x00000000UL, 0x00000000UL, 0x00000000UL, 0x00000001UL, + 0x45512319UL, 0x50B75FC4UL, 0x402DA173UL, 0x2FC9BEBEUL + ); + + /* A scalar set to 0s should be 0. */ + memset(bin, 0, 32); + secp256k1_scalar_set_b32(&scalar, bin, &overflow); + CHECK(overflow == 0); + CHECK(secp256k1_scalar_is_zero(&scalar)); + + /* A scalar with value of the curve order should be 0. */ secp256k1_scalar_order_get_num(&order); secp256k1_num_get_bin(bin, 32, &order); - secp256k1_scalar_set_b32(&zero, bin, &overflow); + secp256k1_scalar_set_b32(&scalar, bin, &overflow); CHECK(overflow == 1); - CHECK(secp256k1_scalar_is_zero(&zero)); + CHECK(secp256k1_scalar_is_zero(&scalar)); + + /* A scalar with value of the curve order minus one should not overflow. */ + bin[31] -= 1; + secp256k1_scalar_set_b32(&scalar, bin, &overflow); + CHECK(overflow == 0); + secp256k1_scalar_get_b32(bin_tmp, &scalar); + CHECK(memcmp(bin, bin_tmp, 32) == 0); + + /* A scalar set to all 1s should overflow. */ + memset(bin, 0xFF, 32); + secp256k1_scalar_set_b32(&scalar, bin, &overflow); + CHECK(overflow == 1); + CHECK(secp256k1_scalar_eq(&scalar, &all_ones_minus_order)); } #endif