linux/crypto
Eric Biggers 268a84d36e crypto: af_alg - avoid undefined behavior accessing salg_name
commit 92eb6c3060 upstream.

Commit 3f69cc6076 ("crypto: af_alg - Allow arbitrarily long algorithm
names") made the kernel start accepting arbitrarily long algorithm names
in sockaddr_alg.  However, the actual length of the salg_name field
stayed at the original 64 bytes.

This is broken because the kernel can access indices >= 64 in salg_name,
which is undefined behavior -- even though the memory that is accessed
is still located within the sockaddr structure.  It would only be
defined behavior if the array were properly marked as arbitrary-length
(either by making it a flexible array, which is the recommended way
these days, or by making it an array of length 0 or 1).

We can't simply change salg_name into a flexible array, since that would
break source compatibility with userspace programs that embed
sockaddr_alg into another struct, or (more commonly) declare a
sockaddr_alg like 'struct sockaddr_alg sa = { .salg_name = "foo" };'.

One solution would be to change salg_name into a flexible array only
when '#ifdef __KERNEL__'.  However, that would keep userspace without an
easy way to actually use the longer algorithm names.

Instead, add a new structure 'sockaddr_alg_new' that has the flexible
array field, and expose it to both userspace and the kernel.
Make the kernel use it correctly in alg_bind().

This addresses the syzbot report
"UBSAN: array-index-out-of-bounds in alg_bind"
(https://syzkaller.appspot.com/bug?extid=92ead4eb8e26a26d465e).

Reported-by: syzbot+92ead4eb8e26a26d465e@syzkaller.appspotmail.com
Fixes: 3f69cc6076 ("crypto: af_alg - Allow arbitrarily long algorithm names")
Cc: <stable@vger.kernel.org> # v4.12+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-12-30 11:25:48 +01:00
..
asymmetric_keys
async_tx
842.c
ablkcipher.c
acompress.c
aead.c
aegis.h
aegis128.c
aegis128l.c
aegis256.c
aes_generic.c
aes_ti.c
af_alg.c crypto: af_alg - avoid undefined behavior accessing salg_name 2020-12-30 11:25:48 +01:00
ahash.c
akcipher.c
algapi.c
algboss.c
algif_aead.c
algif_hash.c
algif_rng.c
algif_skcipher.c
ansi_cprng.c
anubis.c
api.c
arc4.c
authenc.c
authencesn.c
blkcipher.c
blowfish_common.c
blowfish_generic.c
camellia_generic.c
cast_common.c
cast5_generic.c
cast6_generic.c
cbc.c
ccm.c
cfb.c
chacha20_generic.c
chacha20poly1305.c
cipher.c
cmac.c
compress.c
crc32_generic.c
crc32c_generic.c
crct10dif_common.c
crct10dif_generic.c
cryptd.c
crypto_engine.c
crypto_null.c
crypto_user.c
crypto_wq.c
ctr.c
cts.c
deflate.c
des_generic.c
dh_helper.c
dh.c
drbg.c
ecb.c
ecc_curve_defs.h
ecc.c
ecc.h
ecdh_helper.c
ecdh.c
echainiv.c
fcrypt.c
fips.c
gcm.c
gf128mul.c
ghash-generic.c
hash_info.c
hmac.c
internal.h
jitterentropy-kcapi.c
jitterentropy.c
Kconfig
keywrap.c
khazad.c
kpp.c
lrw.c
lz4.c
lz4hc.c
lzo.c
Makefile
mcryptd.c
md4.c
md5.c
memneq.c
michael_mic.c
morus640.c
morus1280.c
pcbc.c
pcrypt.c
poly1305_generic.c
proc.c
ripemd.h
rmd128.c
rmd160.c
rmd256.c
rmd320.c
rng.c
rsa_helper.c
rsa-pkcs1pad.c
rsa.c
rsaprivkey.asn1
rsapubkey.asn1
salsa20_generic.c
scatterwalk.c
scompress.c
seed.c
seqiv.c
serpent_generic.c
sha1_generic.c
sha3_generic.c
sha256_generic.c
sha512_generic.c
shash.c
simd.c
skcipher.c
sm3_generic.c
sm4_generic.c
tcrypt.c
tcrypt.h
tea.c
testmgr.c
testmgr.h
tgr192.c
twofish_common.c
twofish_generic.c
vmac.c
wp512.c
xcbc.c
xor.c
xts.c
zstd.c