From 01138f5853a16068fb5a45ea39d3fc35fe664cb7 Mon Sep 17 00:00:00 2001 From: Yusuke Endoh Date: Sun, 16 Feb 2020 19:55:19 +0900 Subject: Make OpenSSL::OSSL#test_memcmp_timing robust The test was too fragile. Actually, it fails on one of our CIs immediately after it was merged to ruby/ruby. https://gist.github.com/ko1/7ea4a5826641f79e2f9e041d83e45dba#file-brlog-trunk_clang_40-20200216-101730-L532-L535 https://gist.github.com/ko1/1c657746092b871359d8bf9e0ad28921#file-brlog-trunk-test4-20200216-104518-L473-L476 * Two measurements, a-b and a-c, must be interative instead of sequential; the execution time will be easily affected by disturbance (say, cron job or some external process invoked during measurement) * The comparison of the two results must be relative instead of absolute; slow machine may take several tens of seconds for each execution, and one delta second is too small. The test cases of a, b, and c are very extreme, so if the target method has a bug, the two execution times would be very different. So I think it is enough to check if the difference is less than 10 times. This change is the same as https://github.com/ruby/openssl/pull/332 --- test/openssl/test_ossl.rb | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'test') diff --git a/test/openssl/test_ossl.rb b/test/openssl/test_ossl.rb index f517b1d83d..f83e8136fa 100644 --- a/test/openssl/test_ossl.rb +++ b/test/openssl/test_ossl.rb @@ -52,10 +52,13 @@ class OpenSSL::OSSL < OpenSSL::SSLTestCase c = "y#{a}" a = "#{a}x" - n = 10_000 - a_b_time = Benchmark.measure { n.times { OpenSSL.fixed_length_secure_compare(a, b) } }.real - a_c_time = Benchmark.measure { n.times { OpenSSL.fixed_length_secure_compare(a, c) } }.real - assert_in_delta(a_b_time, a_c_time, 1, "fixed_length_secure_compare timing test failed") + a_b_time = a_c_time = 0 + 100.times do + a_b_time += Benchmark.measure { 100.times { OpenSSL.fixed_length_secure_compare(a, b) } }.real + a_c_time += Benchmark.measure { 100.times { OpenSSL.fixed_length_secure_compare(a, c) } }.real + end + assert_operator(a_b_time, :<, a_c_time * 10, "fixed_length_secure_compare timing test failed") + assert_operator(a_c_time, :<, a_b_time * 10, "fixed_length_secure_compare timing test failed") end end -- cgit v1.2.3