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tls: block decryption when a rekey is pending

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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@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Sabrina Dubroca 2024-12-12 16:36:04 +01:00 committed by David S. Miller
parent 92c932b994
commit 0471b1093e
2 changed files with 37 additions and 1 deletions
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3
include/net/tls.h
View File

@ -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;

35
net/tls/tls_sw.c
View File

@ -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);