linux/crypto/asymmetric_keys
Eric Biggers 0f30cbea00 X.509: reject invalid BIT STRING for subjectPublicKey
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: 42d5ec27f8 ("X.509: Add an ASN.1 decoder")
Cc: <stable@vger.kernel.org> # v3.7+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
2017-12-08 15:13:27 +00:00
..
.gitignore X.509: Add a crypto key parser for binary (DER) X.509 certificates 2012-10-08 13:50:22 +10:30
asymmetric_keys.h KEYS: Generalise x509_request_asymmetric_key() 2016-04-11 22:41:56 +01:00
asymmetric_type.c KEYS: checking the input id parameters before finding asymmetric key 2017-10-18 09:12:40 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mscode_parser.c pefile: Fix the failure of calculation for digest 2016-07-18 12:19:46 +10:00
mscode.asn1 pefile: Parse the "Microsoft individual code signing" data blob 2014-07-09 14:58:37 +01:00
pkcs7_key_type.c pkcs7: Set the module licence to prevent tainting 2017-11-15 16:38:45 +00:00
pkcs7_parser.c pkcs7: Set the module licence to prevent tainting 2017-11-15 16:38:45 +00:00
pkcs7_parser.h PKCS#7: Handle blacklisted certificates 2017-04-03 16:07:25 +01:00
pkcs7_trust.c KEYS: Generalise x509_request_asymmetric_key() 2016-04-11 22:41:56 +01:00
pkcs7_verify.c PKCS#7: Handle blacklisted certificates 2017-04-03 16:07:25 +01:00
pkcs7.asn1 PKCS#7: Appropriately restrict authenticated attributes and content type 2015-08-12 17:01:01 +01:00
public_key.c pkcs7: Set the module licence to prevent tainting 2017-11-15 16:38:45 +00:00
restrict.c KEYS: Keyring asymmetric key restrict method with chaining 2017-04-04 14:10:13 -07:00
signature.c KEYS: Add identifier pointers to public_key_signature struct 2016-04-06 16:13:33 +01:00
verify_pefile.c crypto : asymmetric_keys : verify_pefile:zero memory content before freeing 2017-06-09 13:29:50 +10:00
verify_pefile.h KEYS: Generalise system_verify_data() to provide access to internal content 2016-04-06 16:14:24 +01:00
x509_akid.asn1 X.509: Extract both parts of the AuthorityKeyIdentifier 2015-08-07 16:26:13 +01:00
x509_cert_parser.c X.509: reject invalid BIT STRING for subjectPublicKey 2017-12-08 15:13:27 +00:00
x509_parser.h X.509: Allow X.509 certs to be blacklisted 2017-04-03 16:07:25 +01:00
x509_public_key.c pkcs7: Set the module licence to prevent tainting 2017-11-15 16:38:45 +00:00
x509.asn1 X.509: Add bits needed for PKCS#7 2014-07-01 16:40:19 +01:00