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Commit | Line | Data |
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9c6fd700 GKH |
1 | From f5527fffff3f002b0a6b376163613b82f69de073 Mon Sep 17 00:00:00 2001 |
2 | From: Andrey Ryabinin <aryabinin@virtuozzo.com> | |
3 | Date: Thu, 24 Nov 2016 13:23:10 +0000 | |
4 | Subject: mpi: Fix NULL ptr dereference in mpi_powm() [ver #3] | |
5 | ||
6 | From: Andrey Ryabinin <aryabinin@virtuozzo.com> | |
7 | ||
8 | commit f5527fffff3f002b0a6b376163613b82f69de073 upstream. | |
9 | ||
10 | This fixes CVE-2016-8650. | |
11 | ||
12 | If mpi_powm() is given a zero exponent, it wants to immediately return | |
13 | either 1 or 0, depending on the modulus. However, if the result was | |
14 | initalised with zero limb space, no limbs space is allocated and a | |
15 | NULL-pointer exception ensues. | |
16 | ||
17 | Fix this by allocating a minimal amount of limb space for the result when | |
18 | the 0-exponent case when the result is 1 and not touching the limb space | |
19 | when the result is 0. | |
20 | ||
21 | This affects the use of RSA keys and X.509 certificates that carry them. | |
22 | ||
23 | BUG: unable to handle kernel NULL pointer dereference at (null) | |
24 | IP: [<ffffffff8138ce5d>] mpi_powm+0x32/0x7e6 | |
25 | PGD 0 | |
26 | Oops: 0002 [#1] SMP | |
27 | Modules linked in: | |
28 | CPU: 3 PID: 3014 Comm: keyctl Not tainted 4.9.0-rc6-fscache+ #278 | |
29 | Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014 | |
30 | task: ffff8804011944c0 task.stack: ffff880401294000 | |
31 | RIP: 0010:[<ffffffff8138ce5d>] [<ffffffff8138ce5d>] mpi_powm+0x32/0x7e6 | |
32 | RSP: 0018:ffff880401297ad8 EFLAGS: 00010212 | |
33 | RAX: 0000000000000000 RBX: ffff88040868bec0 RCX: ffff88040868bba0 | |
34 | RDX: ffff88040868b260 RSI: ffff88040868bec0 RDI: ffff88040868bee0 | |
35 | RBP: ffff880401297ba8 R08: 0000000000000000 R09: 0000000000000000 | |
36 | R10: 0000000000000047 R11: ffffffff8183b210 R12: 0000000000000000 | |
37 | R13: ffff8804087c7600 R14: 000000000000001f R15: ffff880401297c50 | |
38 | FS: 00007f7a7918c700(0000) GS:ffff88041fb80000(0000) knlGS:0000000000000000 | |
39 | CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 | |
40 | CR2: 0000000000000000 CR3: 0000000401250000 CR4: 00000000001406e0 | |
41 | Stack: | |
42 | ffff88040868bec0 0000000000000020 ffff880401297b00 ffffffff81376cd4 | |
43 | 0000000000000100 ffff880401297b10 ffffffff81376d12 ffff880401297b30 | |
44 | ffffffff81376f37 0000000000000100 0000000000000000 ffff880401297ba8 | |
45 | Call Trace: | |
46 | [<ffffffff81376cd4>] ? __sg_page_iter_next+0x43/0x66 | |
47 | [<ffffffff81376d12>] ? sg_miter_get_next_page+0x1b/0x5d | |
48 | [<ffffffff81376f37>] ? sg_miter_next+0x17/0xbd | |
49 | [<ffffffff8138ba3a>] ? mpi_read_raw_from_sgl+0xf2/0x146 | |
50 | [<ffffffff8132a95c>] rsa_verify+0x9d/0xee | |
51 | [<ffffffff8132acca>] ? pkcs1pad_sg_set_buf+0x2e/0xbb | |
52 | [<ffffffff8132af40>] pkcs1pad_verify+0xc0/0xe1 | |
53 | [<ffffffff8133cb5e>] public_key_verify_signature+0x1b0/0x228 | |
54 | [<ffffffff8133d974>] x509_check_for_self_signed+0xa1/0xc4 | |
55 | [<ffffffff8133cdde>] x509_cert_parse+0x167/0x1a1 | |
56 | [<ffffffff8133d609>] x509_key_preparse+0x21/0x1a1 | |
57 | [<ffffffff8133c3d7>] asymmetric_key_preparse+0x34/0x61 | |
58 | [<ffffffff812fc9f3>] key_create_or_update+0x145/0x399 | |
59 | [<ffffffff812fe227>] SyS_add_key+0x154/0x19e | |
60 | [<ffffffff81001c2b>] do_syscall_64+0x80/0x191 | |
61 | [<ffffffff816825e4>] entry_SYSCALL64_slow_path+0x25/0x25 | |
62 | 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 | |
63 | RIP [<ffffffff8138ce5d>] mpi_powm+0x32/0x7e6 | |
64 | RSP <ffff880401297ad8> | |
65 | CR2: 0000000000000000 | |
66 | ---[ end trace d82015255d4a5d8d ]--- | |
67 | ||
68 | Basically, this is a backport of a libgcrypt patch: | |
69 | ||
70 | http://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=patch;h=6e1adb05d290aeeb1c230c763970695f4a538526 | |
71 | ||
72 | Fixes: cdec9cb5167a ("crypto: GnuPG based MPI lib - source files (part 1)") | |
73 | Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com> | |
74 | Signed-off-by: David Howells <dhowells@redhat.com> | |
75 | cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com> | |
76 | cc: linux-ima-devel@lists.sourceforge.net | |
77 | Signed-off-by: James Morris <james.l.morris@oracle.com> | |
78 | Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> | |
79 | ||
80 | --- | |
81 | lib/mpi/mpi-pow.c | 7 ++++++- | |
82 | 1 file changed, 6 insertions(+), 1 deletion(-) | |
83 | ||
84 | --- a/lib/mpi/mpi-pow.c | |
85 | +++ b/lib/mpi/mpi-pow.c | |
86 | @@ -64,8 +64,13 @@ int mpi_powm(MPI res, MPI base, MPI exp, | |
87 | if (!esize) { | |
88 | /* Exponent is zero, result is 1 mod MOD, i.e., 1 or 0 | |
89 | * depending on if MOD equals 1. */ | |
90 | - rp[0] = 1; | |
91 | res->nlimbs = (msize == 1 && mod->d[0] == 1) ? 0 : 1; | |
92 | + if (res->nlimbs) { | |
93 | + if (mpi_resize(res, 1) < 0) | |
94 | + goto enomem; | |
95 | + rp = res->d; | |
96 | + rp[0] = 1; | |
97 | + } | |
98 | res->sign = 0; | |
99 | goto leave; | |
100 | } |