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Fix information leak in geli(8) integrity mode

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In integrity mode, a larger logical sector (e.g., 4096 bytes) spans several
physical sectors (e.g., 512 bytes) on the backing device.  Due to hash
overhead, a 4096 byte logical sector takes 8.5625 512-byte physical sectors.
This means that only 288 bytes (256 data + 32 hash) of the last 512 byte
sector are used.

The memory allocation used to store the encrypted data to be written to the
physical sectors comes from malloc(9) and does not use M_ZERO.

Previously, nothing initialized the final physical sector backing each
logical sector, aside from the hash + encrypted data portion.  So 224 bytes
of kernel heap memory was leaked to every block :-(.

This patch addresses the issue by initializing the trailing portion of the
physical sector in every logical sector to zeros before use.  A much simpler
but higher overhead fix would be to tag the entire allocation M_ZERO.

PR:		222077
Reported by:	Maxim Khitrov <max AT mxcrypt.com>
Reviewed by:	emaste
Security:	yes
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D12272
This commit is contained in:
Conrad Meyer 2017-09-09 01:41:01 +00:00
parent 3d96cd7873
commit ea5eee641e
1 changed files with 9 additions and 1 deletions
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10
sys/geom/eli/g_eli_integrity.c
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@ -463,8 +463,16 @@ g_eli_auth_run(struct g_eli_worker *wr, struct bio *bp)
authkey = (u_char *)p; p += G_ELI_AUTH_SECKEYLEN;
data_secsize = sc->sc_data_per_sector;
if ((i % lsec) == 0)
if ((i % lsec) == 0) {
data_secsize = decr_secsize % data_secsize;
/*
* Last encrypted sector of each decrypted sector is
* only partially filled.
*/
if (bp->bio_cmd == BIO_WRITE)
memset(data + sc->sc_alen + data_secsize, 0,
encr_secsize - sc->sc_alen - data_secsize);
}
if (bp->bio_cmd == BIO_READ) {
/* Remember read HMAC. */