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net/tls: handle errors from padding_length()

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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 <davejwatson@fb.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jakub Kicinski 2019-05-09 16:14:07 -07:00 committed by David S. Miller
parent 88c80bee88
commit b53f4976fb
1 changed files with 22 additions and 8 deletions
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30
net/tls/tls_sw.c
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@ -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);