From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754500AbdLLNbV (ORCPT ); Tue, 12 Dec 2017 08:31:21 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:33436 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754457AbdLLMzf (ORCPT ); Tue, 12 Dec 2017 07:55:35 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Biggers , David Howells , James Morris Subject: [PATCH 4.9 021/148] X.509: reject invalid BIT STRING for subjectPublicKey Date: Tue, 12 Dec 2017 13:43:51 +0100 Message-Id: <20171212124432.074851722@linuxfoundation.org> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20171212124431.207182779@linuxfoundation.org> References: <20171212124431.207182779@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Biggers commit 0f30cbea005bd3077bd98cd29277d7fc2699c1da upstream. Adding a specially crafted X.509 certificate whose subjectPublicKey ASN.1 value is zero-length caused x509_extract_key_data() to set the public key size to SIZE_MAX, as it subtracted the nonexistent BIT STRING metadata byte. Then, x509_cert_parse() called kmemdup() with that bogus size, triggering the WARN_ON_ONCE() in kmalloc_slab(). This appears to be harmless, but it still must be fixed since WARNs are never supposed to be user-triggerable. Fix it by updating x509_cert_parse() to validate that the value has a BIT STRING metadata byte, and that the byte is 0 which indicates that the number of bits in the bitstring is a multiple of 8. It would be nice to handle the metadata byte in asn1_ber_decoder() instead. But that would be tricky because in the general case a BIT STRING could be implicitly tagged, and/or could legitimately have a length that is not a whole number of bytes. Here was the WARN (cleaned up slightly): WARNING: CPU: 1 PID: 202 at mm/slab_common.c:971 kmalloc_slab+0x5d/0x70 mm/slab_common.c:971 Modules linked in: CPU: 1 PID: 202 Comm: keyctl Tainted: G B 4.14.0-09238-g1d3b78bbc6e9 #26 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-20171110_100015-anatol 04/01/2014 task: ffff880033014180 task.stack: ffff8800305c8000 Call Trace: __do_kmalloc mm/slab.c:3706 [inline] __kmalloc_track_caller+0x22/0x2e0 mm/slab.c:3726 kmemdup+0x17/0x40 mm/util.c:118 kmemdup include/linux/string.h:414 [inline] x509_cert_parse+0x2cb/0x620 crypto/asymmetric_keys/x509_cert_parser.c:106 x509_key_preparse+0x61/0x750 crypto/asymmetric_keys/x509_public_key.c:174 asymmetric_key_preparse+0xa4/0x150 crypto/asymmetric_keys/asymmetric_type.c:388 key_create_or_update+0x4d4/0x10a0 security/keys/key.c:850 SYSC_add_key security/keys/keyctl.c:122 [inline] SyS_add_key+0xe8/0x290 security/keys/keyctl.c:62 entry_SYSCALL_64_fastpath+0x1f/0x96 Fixes: 42d5ec27f873 ("X.509: Add an ASN.1 decoder") Signed-off-by: Eric Biggers Signed-off-by: David Howells Reviewed-by: James Morris Signed-off-by: Greg Kroah-Hartman --- crypto/asymmetric_keys/x509_cert_parser.c | 2 ++ 1 file changed, 2 insertions(+) --- a/crypto/asymmetric_keys/x509_cert_parser.c +++ b/crypto/asymmetric_keys/x509_cert_parser.c @@ -408,6 +408,8 @@ int x509_extract_key_data(void *context, ctx->cert->pub->pkey_algo = "rsa"; /* Discard the BIT STRING metadata */ + if (vlen < 1 || *(const u8 *)value != 0) + return -EBADMSG; ctx->key = value + 1; ctx->key_size = vlen - 1; return 0;