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. 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 Signed-off-by: Sabrina Dubroca <[email protected]> --- include/net/tls.h | 3 +++ net/tls/tls_sw.c | 35 +++++++++++++++++++++++++++++++++++ 2 files changed, 38 insertions(+) diff --git a/include/net/tls.h b/include/net/tls.h index 3a33924db2bc..870e4421c599 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..db98710c4810 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 +1724,32 @@ 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 tls_msg *tlm = tls_msg(skb); + const struct strp_msg *rxm = strp_msg(skb); + char hs_type; + int err; + + if (likely(tlm->control != TLS_RECORD_TYPE_HANDSHAKE)) + return 0; + + if (rxm->full_len < 1) + return -EINVAL; + + err = skb_copy_bits(skb, rxm->offset, &hs_type, 1); + if (err < 0) + 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) { @@ -1739,6 +1769,10 @@ 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); + err = tls_check_pending_rekey(tls_ctx, darg->skb); + if (err < 0) + return err; + return 0; } @@ -2719,6 +2753,7 @@ 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); -- 2.47.0
