At the time padding_length() is called the record header
is still part of the message. If malicious TLS 1.3 peer
sends an all-zero record padding_length() will stop at
the record header, and return full length of the data
including the tail_size.
Subsequent subtraction of prot->overhead_size from rxm->full_len
will cause rxm->full_len to turn negative. skb accessors,
however, will always catch resulting out-of-bounds operation,
so in practice this fix comes down to returning the correct
error code. It also fixes a set but not used warning.
This code was added by commit 130b392c6cd6 ("net: tls: Add tls 1.3 support").
CC: Dave Watson <[email protected]>
Signed-off-by: Jakub Kicinski <[email protected]>
Reviewed-by: Dirk van der Merwe <[email protected]>
---
net/tls/tls_sw.c | 30 ++++++++++++++++++++++--------
1 file changed, 22 insertions(+), 8 deletions(-)
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index c02293fb10e6..d93f83f77864 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -119,23 +119,25 @@ static int skb_nsg(struct sk_buff *skb, int offset, int
len)
}
static int padding_length(struct tls_sw_context_rx *ctx,
- struct tls_context *tls_ctx, struct sk_buff *skb)
+ struct tls_prot_info *prot, struct sk_buff *skb)
{
struct strp_msg *rxm = strp_msg(skb);
int sub = 0;
/* Determine zero-padding length */
- if (tls_ctx->prot_info.version == TLS_1_3_VERSION) {
+ if (prot->version == TLS_1_3_VERSION) {
char content_type = 0;
int err;
int back = 17;
while (content_type == 0) {
- if (back > rxm->full_len)
+ if (back > rxm->full_len - prot->prepend_size)
return -EBADMSG;
err = skb_copy_bits(skb,
rxm->offset + rxm->full_len - back,
&content_type, 1);
+ if (err)
+ return err;
if (content_type)
break;
sub++;
@@ -170,9 +172,17 @@ static void tls_decrypt_done(struct crypto_async_request
*req, int err)
tls_err_abort(skb->sk, err);
} else {
struct strp_msg *rxm = strp_msg(skb);
- rxm->full_len -= padding_length(ctx, tls_ctx, skb);
- rxm->offset += prot->prepend_size;
- rxm->full_len -= prot->overhead_size;
+ int pad;
+
+ pad = padding_length(ctx, prot, skb);
+ if (pad < 0) {
+ ctx->async_wait.err = pad;
+ tls_err_abort(skb->sk, pad);
+ } else {
+ rxm->full_len -= pad;
+ rxm->offset += prot->prepend_size;
+ rxm->full_len -= prot->overhead_size;
+ }
}
/* After using skb->sk to propagate sk through crypto async callback
@@ -1478,7 +1488,7 @@ static int decrypt_skb_update(struct sock *sk, struct
sk_buff *skb,
struct tls_prot_info *prot = &tls_ctx->prot_info;
int version = prot->version;
struct strp_msg *rxm = strp_msg(skb);
- int err = 0;
+ int pad, err = 0;
if (!ctx->decrypted) {
#ifdef CONFIG_TLS_DEVICE
@@ -1501,7 +1511,11 @@ static int decrypt_skb_update(struct sock *sk, struct
sk_buff *skb,
*zc = false;
}
- rxm->full_len -= padding_length(ctx, tls_ctx, skb);
+ pad = padding_length(ctx, prot, skb);
+ if (pad < 0)
+ return pad;
+
+ rxm->full_len -= pad;
rxm->offset += prot->prepend_size;
rxm->full_len -= prot->overhead_size;
tls_advance_record_sn(sk, &tls_ctx->rx, version);
--
2.21.0
