From: jared.jennings.ctr@...
Date: 2014-03-28T17:54:33+00:00
Subject: [ruby-core:61742] [ruby-trunk - Bug #9659] crash in FIPS mode after unchecked algo->init_func failure

Issue #9659 has been updated by Jared Jennings.


I've just compared the Debian and CentOS OpenSSL sources, and it looks like large parts of the FIPS functionality in OpenSSL that I've taken for granted are provided in CentOS/RHEL-specific patches. So you may not be able to duplicate the failure with stock OpenSSL, or on Debian or Ubuntu machines.

On my RHEL 6 machine, I needed the `dracut-fips` package installed, which contains the FIPS crypto module (sometimes it's called a "canister"); see https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Security_Guide/sect-Security_Guide-Federal_Standards_And_Regulations-Federal_Information_Processing_Standard.html. This was because the OpenSSL init function checked whether the FIPS module was installed, and it's distributed in this package. But the code to check this was part of the CentOS/RHEL patches.

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Bug #9659: crash in FIPS mode after unchecked algo->init_func failure
https://bugs.ruby-lang.org/issues/9659#change-45982

* Author: Jared Jennings
* Status: Feedback
* Priority: Normal
* Assignee: 
* Category: ext
* Target version: current: 2.2.0
* ruby -v: ruby 1.8.7 (2011-06-30 patchlevel 352) [x86_64-linux]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN
----------------------------------------
This is just like #4944, but in the `digest` extension instead of the `openssl` extension.

On my host, which is configured for FIPS 140-2 compliance (this is a U.S. Government security standard), OpenSSL refuses to perform an MD5 checksum. It indicates this refusal when the digest algorithm initialization function is called: this function returns a 0 indicating failure instead of a 1 indicating success. But it's just a bunch of arithmetic; how can it fail? So the return code is ignored. But if the initialization fails, and we go on trying to use the algorithm, the Ruby interpreter crashes:

~~~
  $ OPENSSL_FORCE_FIPS_MODE= ruby -rdigest -e "puts Digest::MD5.hexdigest('hi')"
  md5_dgst.c(78): OpenSSL internal error, assertion failed: Digest MD5 forbidden in FIPS mode!
  Aborted (core dumped)
~~~

The digest extension, in the `rb_digest_base_alloc`, `rb_digest_base_reset`, and `rb_digest_base_finish` functions, is ignoring the return code of `algo->init_func`. If OpenSSL is present at build time, `algo->init_func` works out to be the `MD5_Init` function from OpenSSL. This function, according to its man page, returns a 1 for success or 0 for failure.

I see the problem under Ruby 1.8.7 as patched by Red Hat; I can't easily build the trunk on my system, but it looks like in r43668 the return value still isn't being checked in these three places:

 * source:ext/digest/digest.c@43668#L551
 * source:ext/digest/digest.c@43668#L589
 * source:ext/digest/digest.c@43668#L627

---Files--------------------------------
002-builtin-indicate-digest-failure.patch (10.4 KB)
001-detect-digest-failure.patch (2.12 KB)
003-digest-openssl-md5-use-evp-api.patch (1.8 KB)


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