diff options
authorEric Biggers <ebiggers@google.com>2018-06-26 16:59:46 +0100
committerJames Morris <james.morris@microsoft.com>2018-06-26 09:43:05 -0700
commit3619dec5103dd999a777e3e4ea08c8f40a6ddc57 (patch)
parent2e20ce4a66b798671c60198ea2547d5e090dd991 (diff)
dh key: fix rounding up KDF output length
Commit 383203eff718 ("dh key: get rid of stack allocated array") changed kdf_ctr() to assume that the length of key material to derive is a multiple of the digest size. The length was supposed to be rounded up accordingly. However, the round_up() macro was used which only gives the correct result on power-of-2 arguments, whereas not all hash algorithms have power-of-2 digest sizes. In some cases this resulted in a write past the end of the 'outbuf' buffer. Fix it by switching to roundup(), which works for non-power-of-2 inputs. Reported-by: syzbot+486f97f892efeb2075a3@syzkaller.appspotmail.com Reported-by: syzbot+29d17b7898b41ee120a5@syzkaller.appspotmail.com Reported-by: syzbot+8a608baf8751184ec727@syzkaller.appspotmail.com Reported-by: syzbot+d04e58bd384f1fe0b112@syzkaller.appspotmail.com Fixes: 383203eff718 ("dh key: get rid of stack allocated array") Signed-off-by: Eric Biggers <ebiggers@google.com> Acked-by: Kees Cook <keescook@chromium.org> Acked-by: Tycho Andersen <tycho@tycho.ws> Signed-off-by: James Morris <james.morris@microsoft.com>
1 files changed, 4 insertions, 2 deletions
diff --git a/security/keys/dh.c b/security/keys/dh.c
index f7403821db7f..b203f7758f97 100644
--- a/security/keys/dh.c
+++ b/security/keys/dh.c
@@ -142,6 +142,8 @@ static void kdf_dealloc(struct kdf_sdesc *sdesc)
* The src pointer is defined as Z || other info where Z is the shared secret
* from DH and other info is an arbitrary string (see SP800-56A section
+ *
+ * 'dlen' must be a multiple of the digest size.
static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen,
u8 *dst, unsigned int dlen, unsigned int zlen)
@@ -205,8 +207,8 @@ static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc,
uint8_t *outbuf = NULL;
int ret;
- size_t outbuf_len = round_up(buflen,
- crypto_shash_digestsize(sdesc->shash.tfm));
+ size_t outbuf_len = roundup(buflen,
+ crypto_shash_digestsize(sdesc->shash.tfm));
outbuf = kmalloc(outbuf_len, GFP_KERNEL);
if (!outbuf) {