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101 lines
4.2 KiB
Diff
101 lines
4.2 KiB
Diff
From f5527fffff3f002b0a6b376163613b82f69de073 Mon Sep 17 00:00:00 2001
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From: Andrey Ryabinin <aryabinin@virtuozzo.com>
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Date: Thu, 24 Nov 2016 13:23:10 +0000
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Subject: mpi: Fix NULL ptr dereference in mpi_powm() [ver #3]
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This fixes CVE-2016-8650.
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If mpi_powm() is given a zero exponent, it wants to immediately return
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either 1 or 0, depending on the modulus. However, if the result was
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initalised with zero limb space, no limbs space is allocated and a
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NULL-pointer exception ensues.
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Fix this by allocating a minimal amount of limb space for the result when
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the 0-exponent case when the result is 1 and not touching the limb space
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when the result is 0.
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This affects the use of RSA keys and X.509 certificates that carry them.
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BUG: unable to handle kernel NULL pointer dereference at (null)
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IP: [<ffffffff8138ce5d>] mpi_powm+0x32/0x7e6
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PGD 0
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Oops: 0002 [#1] SMP
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Modules linked in:
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CPU: 3 PID: 3014 Comm: keyctl Not tainted 4.9.0-rc6-fscache+ #278
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Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014
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task: ffff8804011944c0 task.stack: ffff880401294000
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RIP: 0010:[<ffffffff8138ce5d>] [<ffffffff8138ce5d>] mpi_powm+0x32/0x7e6
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RSP: 0018:ffff880401297ad8 EFLAGS: 00010212
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RAX: 0000000000000000 RBX: ffff88040868bec0 RCX: ffff88040868bba0
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RDX: ffff88040868b260 RSI: ffff88040868bec0 RDI: ffff88040868bee0
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RBP: ffff880401297ba8 R08: 0000000000000000 R09: 0000000000000000
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R10: 0000000000000047 R11: ffffffff8183b210 R12: 0000000000000000
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R13: ffff8804087c7600 R14: 000000000000001f R15: ffff880401297c50
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FS: 00007f7a7918c700(0000) GS:ffff88041fb80000(0000) knlGS:0000000000000000
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CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
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CR2: 0000000000000000 CR3: 0000000401250000 CR4: 00000000001406e0
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Stack:
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ffff88040868bec0 0000000000000020 ffff880401297b00 ffffffff81376cd4
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0000000000000100 ffff880401297b10 ffffffff81376d12 ffff880401297b30
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ffffffff81376f37 0000000000000100 0000000000000000 ffff880401297ba8
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Call Trace:
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[<ffffffff81376cd4>] ? __sg_page_iter_next+0x43/0x66
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[<ffffffff81376d12>] ? sg_miter_get_next_page+0x1b/0x5d
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[<ffffffff81376f37>] ? sg_miter_next+0x17/0xbd
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[<ffffffff8138ba3a>] ? mpi_read_raw_from_sgl+0xf2/0x146
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[<ffffffff8132a95c>] rsa_verify+0x9d/0xee
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[<ffffffff8132acca>] ? pkcs1pad_sg_set_buf+0x2e/0xbb
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[<ffffffff8132af40>] pkcs1pad_verify+0xc0/0xe1
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[<ffffffff8133cb5e>] public_key_verify_signature+0x1b0/0x228
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[<ffffffff8133d974>] x509_check_for_self_signed+0xa1/0xc4
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[<ffffffff8133cdde>] x509_cert_parse+0x167/0x1a1
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[<ffffffff8133d609>] x509_key_preparse+0x21/0x1a1
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[<ffffffff8133c3d7>] asymmetric_key_preparse+0x34/0x61
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[<ffffffff812fc9f3>] key_create_or_update+0x145/0x399
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[<ffffffff812fe227>] SyS_add_key+0x154/0x19e
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[<ffffffff81001c2b>] do_syscall_64+0x80/0x191
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[<ffffffff816825e4>] entry_SYSCALL64_slow_path+0x25/0x25
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Code: 56 41 55 41 54 53 48 81 ec a8 00 00 00 44 8b 71 04 8b 42 04 4c 8b 67 18 45 85 f6 89 45 80 0f 84 b4 06 00 00 85 c0 75 2f 41 ff ce <49> c7 04 24 01 00 00 00 b0 01 75 0b 48 8b 41 18 48 83 38 01 0f
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RIP [<ffffffff8138ce5d>] mpi_powm+0x32/0x7e6
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RSP <ffff880401297ad8>
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CR2: 0000000000000000
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---[ end trace d82015255d4a5d8d ]---
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Basically, this is a backport of a libgcrypt patch:
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http://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=patch;h=6e1adb05d290aeeb1c230c763970695f4a538526
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Fixes: cdec9cb5167a ("crypto: GnuPG based MPI lib - source files (part 1)")
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Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
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Signed-off-by: David Howells <dhowells@redhat.com>
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cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
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cc: linux-ima-devel@lists.sourceforge.net
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cc: stable@vger.kernel.org
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Signed-off-by: James Morris <james.l.morris@oracle.com>
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---
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lib/mpi/mpi-pow.c | 7 ++++++-
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1 file changed, 6 insertions(+), 1 deletion(-)
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diff --git a/lib/mpi/mpi-pow.c b/lib/mpi/mpi-pow.c
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index 5464c87..e24388a 100644
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--- a/lib/mpi/mpi-pow.c
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+++ b/lib/mpi/mpi-pow.c
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@@ -64,8 +64,13 @@ int mpi_powm(MPI res, MPI base, MPI exp, MPI mod)
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if (!esize) {
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/* Exponent is zero, result is 1 mod MOD, i.e., 1 or 0
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* depending on if MOD equals 1. */
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- rp[0] = 1;
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res->nlimbs = (msize == 1 && mod->d[0] == 1) ? 0 : 1;
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+ if (res->nlimbs) {
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+ if (mpi_resize(res, 1) < 0)
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+ goto enomem;
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+ rp = res->d;
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+ rp[0] = 1;
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+ }
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res->sign = 0;
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goto leave;
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}
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--
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cgit v1.1
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