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| author | Bryan Donlan <bdonlan@amazon.com> | 2018-03-07 16:01:06 -0500 |
|---|---|---|
| committer | Rich Salz <rsalz@openssl.org> | 2018-03-08 10:27:49 -0500 |
| commit | 082193ef2b25cf16ec51af9dc9f0ee890beb38b9 (patch) | |
| tree | 47569ec7a98b96948ca9c6c4fdc9f25def757efc /crypto/x86_64cpuid.pl | |
| parent | 83918ad6fddf33acc43aadcc40f08be22ff39482 (diff) | |
| download | openssl-new-082193ef2b25cf16ec51af9dc9f0ee890beb38b9.tar.gz | |
Fix issues in ia32 RDRAND asm leading to reduced entropy
This patch fixes two issues in the ia32 RDRAND assembly code that result in a
(possibly significant) loss of entropy.
The first, less significant, issue is that, by returning success as 0 from
OPENSSL_ia32_rdrand() and OPENSSL_ia32_rdseed(), a subtle bias was introduced.
Specifically, because the assembly routine copied the remaining number of
retries over the result when RDRAND/RDSEED returned 'successful but zero', a
bias towards values 1-8 (primarily 8) was introduced.
The second, more worrying issue was that, due to a mixup in registers, when a
buffer that was not size 0 or 1 mod 8 was passed to OPENSSL_ia32_rdrand_bytes
or OPENSSL_ia32_rdseed_bytes, the last (n mod 8) bytes were all the same value.
This issue impacts only the 64-bit variant of the assembly.
This change fixes both issues by first eliminating the only use of
OPENSSL_ia32_rdrand, replacing it with OPENSSL_ia32_rdrand_bytes, and fixes the
register mixup in OPENSSL_ia32_rdrand_bytes. It also adds a sanity test for
OPENSSL_ia32_rdrand_bytes and OPENSSL_ia32_rdseed_bytes to help catch problems
of this nature in the future.
Reviewed-by: Andy Polyakov <appro@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5342)
Diffstat (limited to 'crypto/x86_64cpuid.pl')
| -rw-r--r-- | crypto/x86_64cpuid.pl | 20 |
1 files changed, 3 insertions, 17 deletions
diff --git a/crypto/x86_64cpuid.pl b/crypto/x86_64cpuid.pl index 0a88c7a4ed..513d00560c 100644 --- a/crypto/x86_64cpuid.pl +++ b/crypto/x86_64cpuid.pl @@ -1,5 +1,5 @@ #! /usr/bin/env perl -# Copyright 2005-2016 The OpenSSL Project Authors. All Rights Reserved. +# Copyright 2005-2018 The OpenSSL Project Authors. All Rights Reserved. # # Licensed under the OpenSSL license (the "License"). You may not use # this file except in compliance with the License. You can obtain a copy @@ -434,21 +434,6 @@ ___ sub gen_random { my $rdop = shift; print<<___; -.globl OPENSSL_ia32_${rdop} -.type OPENSSL_ia32_${rdop},\@abi-omnipotent -.align 16 -OPENSSL_ia32_${rdop}: - mov \$8,%ecx -.Loop_${rdop}: - ${rdop} %rax - jc .Lbreak_${rdop} - loop .Loop_${rdop} -.Lbreak_${rdop}: - cmp \$0,%rax - cmove %rcx,%rax - ret -.size OPENSSL_ia32_${rdop},.-OPENSSL_ia32_${rdop} - .globl OPENSSL_ia32_${rdop}_bytes .type OPENSSL_ia32_${rdop}_bytes,\@abi-omnipotent .align 16 @@ -482,11 +467,12 @@ OPENSSL_ia32_${rdop}_bytes: mov %r10b,($arg1) lea 1($arg1),$arg1 inc %rax - shr \$8,%r8 + shr \$8,%r10 dec $arg2 jnz .Ltail_${rdop}_bytes .Ldone_${rdop}_bytes: + xor %r10,%r10 # Clear sensitive data from register ret .size OPENSSL_ia32_${rdop}_bytes,.-OPENSSL_ia32_${rdop}_bytes ___ |