When a TLS handshake record carrying a KeyUpdate message is received,
all subsequent records will be encrypted with a new key. We need to
stop decrypting incoming records with the old key, and wait until
userspace provides a new key.
Make a note of this in the RX context just after decrypting that
record, and stop recvmsg/splice calls with EKEYEXPIRED until the new
key is available.
key_update_pending can't be combined with the existing bitfield,
because we will read it locklessly in ->poll.
Signed-off-by: Sabrina Dubroca <sd@xxxxxxxxxxxxxxx>
---
v3:
- move key_update_pending check into tls_rx_rec_wait (Jakub)
- TLS_RECORD_TYPE_HANDSHAKE was added to include/net/tls_prot.h by
the tls handshake series, drop that from this patch
- move key_update_pending into an existing hole
v4:
- flip TLS_RECORD_TYPE_HANDSHAKE test and use likely() (Jakub)
- pass ctx rather than sk to tls_check_pending_rekey (Jakub)
- use WRITE_ONCE to set key_update_pending to pair with poll's
lockless read
v5:
- some coding style changes (Parthiban Veerasoora)
- changes to error handling in tls_check_pending_rekey (Jakub)
include/net/tls.h | 3 +++
net/tls/tls_sw.c | 35 ++++++++++++++++++++++++++++++++++-
2 files changed, 37 insertions(+), 1 deletion(-)
diff --git a/include/net/tls.h b/include/net/tls.h
index 61fef2880114..857340338b69 100644
--- a/include/net/tls.h
+++ b/include/net/tls.h
@@ -59,6 +59,8 @@ struct tls_rec;
#define TLS_CRYPTO_INFO_READY(info) ((info)->cipher_type)
+#define TLS_HANDSHAKE_KEYUPDATE 24 /* rfc8446 B.3: Key update */
+
#define TLS_AAD_SPACE_SIZE 13
#define TLS_MAX_IV_SIZE 16
@@ -130,6 +132,7 @@ struct tls_sw_context_rx {
u8 async_capable:1;
u8 zc_capable:1;
u8 reader_contended:1;
+ bool key_update_pending;
struct tls_strparser strp;
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index bbf26cc4f6ee..3dcf8ee60fea 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -1314,6 +1314,10 @@ tls_rx_rec_wait(struct sock *sk, struct sk_psock *psock, bool nonblock,
int ret = 0;
long timeo;
+ /* a rekey is pending, let userspace deal with it */
+ if (unlikely(ctx->key_update_pending))
+ return -EKEYEXPIRED;
+
timeo = sock_rcvtimeo(sk, nonblock);
while (!tls_strp_msg_ready(ctx)) {
@@ -1720,6 +1724,34 @@ tls_decrypt_device(struct sock *sk, struct msghdr *msg,
return 1;
}
+static int tls_check_pending_rekey(struct tls_context *ctx, struct sk_buff *skb)
+{
+ const struct strp_msg *rxm = strp_msg(skb);
+ const struct tls_msg *tlm = tls_msg(skb);
+ char hs_type;
+ int err;
+
+ if (likely(tlm->control != TLS_RECORD_TYPE_HANDSHAKE))
+ return 0;
+
+ if (rxm->full_len < 1)
+ return 0;
+
+ err = skb_copy_bits(skb, rxm->offset, &hs_type, 1);
+ if (err < 0) {
+ DEBUG_NET_WARN_ON_ONCE(1);
+ return err;
+ }
+
+ if (hs_type == TLS_HANDSHAKE_KEYUPDATE) {
+ struct tls_sw_context_rx *rx_ctx = ctx->priv_ctx_rx;
+
+ WRITE_ONCE(rx_ctx->key_update_pending, true);
+ }
+
+ return 0;
+}
+
static int tls_rx_one_record(struct sock *sk, struct msghdr *msg,
struct tls_decrypt_arg *darg)
{
@@ -1739,7 +1771,7 @@ static int tls_rx_one_record(struct sock *sk, struct msghdr *msg,
rxm->full_len -= prot->overhead_size;
tls_advance_record_sn(sk, prot, &tls_ctx->rx);
- return 0;
+ return tls_check_pending_rekey(tls_ctx, darg->skb);
}
int decrypt_skb(struct sock *sk, struct scatterlist *sgout)
@@ -2719,6 +2751,7 @@ int tls_set_sw_offload(struct sock *sk, int tx)
crypto_info = &ctx->crypto_recv.info;
cctx = &ctx->rx;
aead = &sw_ctx_rx->aead_recv;
+ sw_ctx_rx->key_update_pending = false;
}
cipher_desc = get_cipher_desc(crypto_info->cipher_type);
--
2.47.1
