[ruby-core:76268] [Ruby trunk Feature#10098] [PATCH] Timing-safe string comparison for OpenSSL::HMAC

Issue #10098 has been updated by Matt U.


Yui, I'm a little confused. The patch you have in your comment looks timing-safe to me. Also I suggest taking a look at Nobu's improvements to my code, I definitely learned a lot more about speed after reading it.

Other things that don't use OpenSSL might benefit from this feature, so my vote is to add this to the String library rather than OpenSSL.

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Feature #10098: [PATCH] Timing-safe string comparison for OpenSSL::HMAC
https://bugs.ruby-lang.org/issues/10098#change-59506

* Author: Matt U
* Status: Assigned
* Priority: Normal
* Assignee: Yukihiro Matsumoto
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I could be totally wrong, but it seems the standard library doesn't provide a reliable way of comparing hashes in constant-time.

* The docs for `OpenSSL::HMAC` encourage the use of `Digest#to_s` (see: http://ruby-doc.org/stdlib-2.1.0/libdoc/openssl/rdoc/OpenSSL/HMAC.html#method-c-new )
* Ruby's string comparison uses memcmp, which isn't timing safe (see: http://rxr.whitequark.org/mri/source/string.c#2382 )

With this patch I propose to add an additional method, `OpenSSL::HMAC#verify`, which takes a binary string with a digest and compares it against the computed hash.


---Files--------------------------------
hmac-timing.patch (2.5 KB)
hmac-timing.patch (2.48 KB)
tsafe_eql.patch (2.48 KB)
tsafe_inline.patch (3.51 KB)
0001-add-timing-safe-string-compare-method.patch (4.31 KB)


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