Date: Wed, 9 Mar 2016 22:31:21 +0100 From: Dimitry Andric <dim@FreeBSD.org> To: Xin Li <delphij@delphij.net> Cc: Antoine Brodin <antoine@FreeBSD.org>, Xin LI <delphij@gmail.com>, Mathieu Arnold <mat@freebsd.org>, Jung-Uk Kim <jkim@freebsd.org>, Bryan Drewery <bdrewery@freebsd.org>, Xin LI <delphij@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, svn-src-releng@freebsd.org Subject: Re: svn commit: r296465 - in releng/9.3: . crypto/openssl crypto/openssl/apps crypto/openssl/bugs crypto/openssl/crypto crypto/openssl/crypto/aes crypto/openssl/crypto/asn1 crypto/openssl/crypto/bf cry... Message-ID: <F14D28E4-4458-4208-8215-DB8998D62E2E@FreeBSD.org> In-Reply-To: <2E9527A1-C869-48DA-9554-2A96F1735F8C@FreeBSD.org> References: <201603071622.u27GMC4a082792@repo.freebsd.org> <9B6D673B7B15CCDC424E97A8@atuin.in.mat.cc> <56DEFD08.6050100@FreeBSD.org> <63FB9E5BBBF224CA12839457@ogg.in.absolight.net> <56DEFDF5.2040500@FreeBSD.org> <1E2DCDEE8775312979CE7D0B@ogg.in.absolight.net> <56DF0234.2090307@FreeBSD.org> <56DF025B.1090706@FreeBSD.org> <DC10EFD5F03DA877503B6C3E@ogg.in.absolight.net> <56DF0550.6000604@FreeBSD.org> <E24637388915226D9A922B8B@atuin.in.mat.cc> <CAGMYy3tfrty-8r-Efzzd56d4AOdV0H%2BParrkUtBWR4f%2B0ZtxWw@mail.gmail.com> <CAALwa8mXg-eE3tZ1R=LAd9nWNAmTkqPmrSaZAmtrQ=u4-=wEeg@mail.gmail.com> <56DFEA05.6060501@delphij.net> <2E9527A1-C869-48DA-9554-2A96F1735F8C@FreeBSD.org>
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[-- Attachment #1 --]
On 09 Mar 2016, at 21:39, Dimitry Andric <dim@FreeBSD.org> wrote:
>
> On 09 Mar 2016, at 10:16, Xin Li <delphij@delphij.net> wrote:
>>
>> FYI -- I can confirm that libcrypto is broken and have a reliable way to
>> trigger it.
>>
>> So far I was able to narrow down this to this change and here is a
>> temporary workaround (which will reintroduce CVE-2016-0702).
>>
>> Cheers,
>> <bn-revert.diff>
>
> FWIW, before the workaround I get this from valgrind:
>
> ==10050== Invalid read of size 8
> ==10050== at 0x6BA3438: MOD_EXP_CTIME_COPY_FROM_PREBUF (bn_exp.c:585)
> ==10050== by 0x6BA3438: BN_mod_exp_mont_consttime (bn_exp.c:760)
> ==10050== by 0x6B84AB7: ??? (dh_key.c:156)
> ==10050== by 0x4E4550B: ssh_dh_gen_key (in /usr/lib/private/libssh.so.5)
> ==10050== by 0x42AEBF: kexgex_server (kexgexs.c:115)
> ==10050== by 0x4E545FE: ssh_kex_input_kexinit (in /usr/lib/private/libssh.so.5)
> ==10050== by 0x4E54BBE: ssh_dispatch_run (in /usr/lib/private/libssh.so.5)
> ==10050== by 0x41085C: do_ssh2_kex (sshd.c:2559)
> ==10050== by 0x41085C: main (sshd.c:2162)
> ==10050== Address 0x2078f3580 is not stack'd, malloc'd or (recently) free'd
> ==10050==
> ==10050==
> ==10050== Process terminating with default action of signal 11 (SIGSEGV): dumping core
> ==10050== Access not within mapped region at address 0x2078F3580
> ==10050== at 0x6BA3438: MOD_EXP_CTIME_COPY_FROM_PREBUF (bn_exp.c:585)
> ==10050== by 0x6BA3438: BN_mod_exp_mont_consttime (bn_exp.c:760)
> ==10050== by 0x6B84AB7: ??? (dh_key.c:156)
> ==10050== by 0x4E4550B: ssh_dh_gen_key (in /usr/lib/private/libssh.so.5)
> ==10050== by 0x42AEBF: kexgex_server (kexgexs.c:115)
> ==10050== by 0x4E545FE: ssh_kex_input_kexinit (in /usr/lib/private/libssh.so.5)
> ==10050== by 0x4E54BBE: ssh_dispatch_run (in /usr/lib/private/libssh.so.5)
> ==10050== by 0x41085C: do_ssh2_kex (sshd.c:2559)
> ==10050== by 0x41085C: main (sshd.c:2162)
> ==10050== If you believe this happened as a result of a stack
> ==10050== overflow in your program's main thread (unlikely but
> ==10050== possible), you can try to increase the size of the
> ==10050== main thread stack using the --main-stacksize= flag.
> ==10050== The main thread stack size used in this run was 16777216.
I think this is a possible fix (it works for me, at least):
Index: crypto/openssl/crypto/bn/bn_exp.c
===================================================================
--- crypto/openssl/crypto/bn/bn_exp.c (revision 296469)
+++ crypto/openssl/crypto/bn/bn_exp.c (working copy)
@@ -758,7 +758,7 @@ int BN_mod_exp_mont_consttime(BIGNUM *rr, const BI
* Fetch the appropriate pre-computed value from the pre-buf
*/
if (!MOD_EXP_CTIME_COPY_FROM_PREBUF
- (computeTemp, top, powerbuf, wvalue, numPowers))
+ (computeTemp, top, powerbuf, wvalue, window))
goto err;
/* Multiply the result into the intermediate result */
Can people experiencing this problem please apply the above diff to
their openssl, rebuild secure/lib/libcrypto, install it, then restart
sshd and/or whatever daemon you have seen the crashes with?
-Dimitry
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