Commit b53f4976 authored by Jakub Kicinski's avatar Jakub Kicinski Committed by David S. Miller

net/tls: handle errors from padding_length()

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 130b392c ("net: tls: Add tls 1.3 support").

CC: Dave Watson <davejwatson@fb.com>
Signed-off-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: default avatarDirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 88c80bee
...@@ -119,23 +119,25 @@ static int skb_nsg(struct sk_buff *skb, int offset, int len) ...@@ -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, 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); struct strp_msg *rxm = strp_msg(skb);
int sub = 0; int sub = 0;
/* Determine zero-padding length */ /* 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; char content_type = 0;
int err; int err;
int back = 17; int back = 17;
while (content_type == 0) { while (content_type == 0) {
if (back > rxm->full_len) if (back > rxm->full_len - prot->prepend_size)
return -EBADMSG; return -EBADMSG;
err = skb_copy_bits(skb, err = skb_copy_bits(skb,
rxm->offset + rxm->full_len - back, rxm->offset + rxm->full_len - back,
&content_type, 1); &content_type, 1);
if (err)
return err;
if (content_type) if (content_type)
break; break;
sub++; sub++;
...@@ -170,9 +172,17 @@ static void tls_decrypt_done(struct crypto_async_request *req, int err) ...@@ -170,9 +172,17 @@ static void tls_decrypt_done(struct crypto_async_request *req, int err)
tls_err_abort(skb->sk, err); tls_err_abort(skb->sk, err);
} else { } else {
struct strp_msg *rxm = strp_msg(skb); struct strp_msg *rxm = strp_msg(skb);
rxm->full_len -= padding_length(ctx, tls_ctx, skb); int pad;
rxm->offset += prot->prepend_size;
rxm->full_len -= prot->overhead_size; 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 /* 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, ...@@ -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; struct tls_prot_info *prot = &tls_ctx->prot_info;
int version = prot->version; int version = prot->version;
struct strp_msg *rxm = strp_msg(skb); struct strp_msg *rxm = strp_msg(skb);
int err = 0; int pad, err = 0;
if (!ctx->decrypted) { if (!ctx->decrypted) {
#ifdef CONFIG_TLS_DEVICE #ifdef CONFIG_TLS_DEVICE
...@@ -1501,7 +1511,11 @@ static int decrypt_skb_update(struct sock *sk, struct sk_buff *skb, ...@@ -1501,7 +1511,11 @@ static int decrypt_skb_update(struct sock *sk, struct sk_buff *skb,
*zc = false; *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->offset += prot->prepend_size;
rxm->full_len -= prot->overhead_size; rxm->full_len -= prot->overhead_size;
tls_advance_record_sn(sk, &tls_ctx->rx, version); tls_advance_record_sn(sk, &tls_ctx->rx, version);
......
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