From bc0539a9b7538c5cb0c194cc0a700466cfa1b003 Mon Sep 17 00:00:00 2001 From: Theo Buehler Date: Tue, 11 Apr 2023 19:43:49 +0200 Subject: [PATCH] [ruby/openssl] Fix modular square root test with LibreSSL >= 3.8 If x is a modular square root of a (mod p) then so is (p - x). Both answers are valid. In particular, both 2 and 3 are valid square roots of 4 (mod 5). Do not assume that a particular square root is chosen by the algorithm. Indeed, the algorithm in OpenSSL and LibreSSL <= 3.7 returns a non-deterministic answer in many cases. LibreSSL 3.8 and later will always return the smaller of the two possible answers. This breaks the current test case. Instead of checking for a particular square root, check that the square of the claimed square root is the given value. This is always true. Add the simplest test case where the answer is indeed non-deterministic. https://github.com/ruby/openssl/commit/93548ae959 --- test/openssl/test_bn.rb | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/test/openssl/test_bn.rb b/test/openssl/test_bn.rb index 77af14091e..ea88ff06ce 100644 --- a/test/openssl/test_bn.rb +++ b/test/openssl/test_bn.rb @@ -175,7 +175,9 @@ class OpenSSL::TestBN < OpenSSL::TestCase end def test_mod_sqrt - assert_equal(3, 4.to_bn.mod_sqrt(5)) + assert_equal(4, 4.to_bn.mod_sqrt(5).mod_sqr(5)) + # One of 189484 or 326277 is returned as a square root of 2 (mod 515761). + assert_equal(2, 2.to_bn.mod_sqrt(515761).mod_sqr(515761)) assert_equal(0, 5.to_bn.mod_sqrt(5)) assert_raise(OpenSSL::BNError) { 3.to_bn.mod_sqrt(5) } end