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Message-Id: <20220705235926.1035407-4-kuba@kernel.org>
Date: Tue, 5 Jul 2022 16:59:24 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org, edumazet@...gle.com, pabeni@...hat.com,
john.fastabend@...il.com, borisp@...dia.com,
linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
maximmi@...dia.com, Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH net-next 3/5] tls: rx: add sockopt for enabling optimistic decrypt with TLS 1.3
Since optimisitic decrypt may add extra load in case of retries
require socket owner to explicitly opt-in.
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
Documentation/networking/tls.rst | 18 ++++++++
include/linux/sockptr.h | 8 ++++
include/net/tls.h | 3 ++
include/uapi/linux/snmp.h | 1 +
include/uapi/linux/tls.h | 2 +
net/tls/tls_main.c | 75 ++++++++++++++++++++++++++++++++
net/tls/tls_proc.c | 1 +
net/tls/tls_sw.c | 21 ++++++---
8 files changed, 122 insertions(+), 7 deletions(-)
diff --git a/Documentation/networking/tls.rst b/Documentation/networking/tls.rst
index be8e10c14b05..7a6643836e42 100644
--- a/Documentation/networking/tls.rst
+++ b/Documentation/networking/tls.rst
@@ -239,6 +239,19 @@ for the original TCP transmission and TCP retransmissions. To the receiver
this will look like TLS records had been tampered with and will result
in record authentication failures.
+TLS_RX_EXPECT_NO_PAD
+~~~~~~~~~~~~~~~~~~~~
+
+TLS 1.3 only. Expect the sender to not pad records. This allows the data
+to be decrypted directly into user space buffers with TLS 1.3.
+
+This optimization is safe to enable only if the remote end is trusted,
+otherwise it is an attack vector to doubling the TLS processing cost.
+
+If the record decrypted turns out to had been padded or is not a data
+record it will be decrypted again into a kernel buffer without zero copy.
+Such events are counted in the ``TlsDecryptRetry`` statistic.
+
Statistics
==========
@@ -264,3 +277,8 @@ TLS implementation exposes the following per-namespace statistics
- ``TlsDeviceRxResync`` -
number of RX resyncs sent to NICs handling cryptography
+
+- ``TlsDecryptRetry`` -
+ number of RX records which had to be re-decrypted due to
+ ``TLS_RX_EXPECT_NO_PAD`` mis-prediction. Note that this counter will
+ also increment for non-data records.
diff --git a/include/linux/sockptr.h b/include/linux/sockptr.h
index ea193414298b..d45902fb4cad 100644
--- a/include/linux/sockptr.h
+++ b/include/linux/sockptr.h
@@ -102,4 +102,12 @@ static inline long strncpy_from_sockptr(char *dst, sockptr_t src, size_t count)
return strncpy_from_user(dst, src.user, count);
}
+static inline int check_zeroed_sockptr(sockptr_t src, size_t offset,
+ size_t size)
+{
+ if (!sockptr_is_kernel(src))
+ return check_zeroed_user(src.user + offset, size);
+ return memchr_inv(src.kernel + offset, 0, size) == NULL;
+}
+
#endif /* _LINUX_SOCKPTR_H */
diff --git a/include/net/tls.h b/include/net/tls.h
index 8017f1703447..4fc16ca5f469 100644
--- a/include/net/tls.h
+++ b/include/net/tls.h
@@ -149,6 +149,7 @@ struct tls_sw_context_rx {
struct sk_buff *recv_pkt;
u8 async_capable:1;
+ u8 zc_capable:1;
atomic_t decrypt_pending;
/* protect crypto_wait with decrypt_pending*/
spinlock_t decrypt_compl_lock;
@@ -239,6 +240,7 @@ struct tls_context {
u8 tx_conf:3;
u8 rx_conf:3;
u8 zerocopy_sendfile:1;
+ u8 rx_no_pad:1;
int (*push_pending_record)(struct sock *sk, int flags);
void (*sk_write_space)(struct sock *sk);
@@ -358,6 +360,7 @@ int tls_sk_attach(struct sock *sk, int optname, char __user *optval,
void tls_err_abort(struct sock *sk, int err);
int tls_set_sw_offload(struct sock *sk, struct tls_context *ctx, int tx);
+void tls_update_rx_zc_capable(struct tls_context *tls_ctx);
void tls_sw_strparser_arm(struct sock *sk, struct tls_context *ctx);
void tls_sw_strparser_done(struct tls_context *tls_ctx);
int tls_sw_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 904909d020e2..1c9152add663 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -344,6 +344,7 @@ enum
LINUX_MIB_TLSRXDEVICE, /* TlsRxDevice */
LINUX_MIB_TLSDECRYPTERROR, /* TlsDecryptError */
LINUX_MIB_TLSRXDEVICERESYNC, /* TlsRxDeviceResync */
+ LINUX_MIN_TLSDECRYPTRETRY, /* TlsDecryptRetry */
__LINUX_MIB_TLSMAX
};
diff --git a/include/uapi/linux/tls.h b/include/uapi/linux/tls.h
index bb8f80812b0b..f1157d8f4acd 100644
--- a/include/uapi/linux/tls.h
+++ b/include/uapi/linux/tls.h
@@ -40,6 +40,7 @@
#define TLS_TX 1 /* Set transmit parameters */
#define TLS_RX 2 /* Set receive parameters */
#define TLS_TX_ZEROCOPY_RO 3 /* TX zerocopy (only sendfile now) */
+#define TLS_RX_EXPECT_NO_PAD 4 /* Attempt opportunistic zero-copy */
/* Supported versions */
#define TLS_VERSION_MINOR(ver) ((ver) & 0xFF)
@@ -162,6 +163,7 @@ enum {
TLS_INFO_TXCONF,
TLS_INFO_RXCONF,
TLS_INFO_ZC_RO_TX,
+ TLS_INFO_RX_NO_PAD,
__TLS_INFO_MAX,
};
#define TLS_INFO_MAX (__TLS_INFO_MAX - 1)
diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index 2ffede463e4a..1b3efc96db0b 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -533,6 +533,37 @@ static int do_tls_getsockopt_tx_zc(struct sock *sk, char __user *optval,
return 0;
}
+static int do_tls_getsockopt_no_pad(struct sock *sk, char __user *optval,
+ int __user *optlen)
+{
+ struct tls_context *ctx = tls_get_ctx(sk);
+ unsigned int value;
+ int err, len;
+
+ if (ctx->prot_info.version != TLS_1_3_VERSION)
+ return -EINVAL;
+
+ if (get_user(len, optlen))
+ return -EFAULT;
+ if (len < sizeof(value))
+ return -EINVAL;
+
+ lock_sock(sk);
+ err = -EINVAL;
+ if (ctx->rx_conf == TLS_SW || ctx->rx_conf == TLS_HW)
+ value = ctx->rx_no_pad;
+ release_sock(sk);
+ if (err)
+ return err;
+
+ if (put_user(sizeof(value), optlen))
+ return -EFAULT;
+ if (copy_to_user(optval, &value, sizeof(value)))
+ return -EFAULT;
+
+ return 0;
+}
+
static int do_tls_getsockopt(struct sock *sk, int optname,
char __user *optval, int __user *optlen)
{
@@ -547,6 +578,9 @@ static int do_tls_getsockopt(struct sock *sk, int optname,
case TLS_TX_ZEROCOPY_RO:
rc = do_tls_getsockopt_tx_zc(sk, optval, optlen);
break;
+ case TLS_RX_EXPECT_NO_PAD:
+ rc = do_tls_getsockopt_no_pad(sk, optval, optlen);
+ break;
default:
rc = -ENOPROTOOPT;
break;
@@ -718,6 +752,38 @@ static int do_tls_setsockopt_tx_zc(struct sock *sk, sockptr_t optval,
return 0;
}
+static int do_tls_setsockopt_no_pad(struct sock *sk, sockptr_t optval,
+ unsigned int optlen)
+{
+ struct tls_context *ctx = tls_get_ctx(sk);
+ u32 val;
+ int rc;
+
+ if (ctx->prot_info.version != TLS_1_3_VERSION ||
+ sockptr_is_null(optval) || optlen < sizeof(val))
+ return -EINVAL;
+
+ rc = copy_from_sockptr(&val, optval, sizeof(val));
+ if (rc)
+ return -EFAULT;
+ if (val > 1)
+ return -EINVAL;
+ rc = check_zeroed_sockptr(optval, sizeof(val), optlen - sizeof(val));
+ if (rc < 1)
+ return rc == 0 ? -EINVAL : rc;
+
+ lock_sock(sk);
+ rc = -EINVAL;
+ if (ctx->rx_conf == TLS_SW || ctx->rx_conf == TLS_HW) {
+ ctx->rx_no_pad = val;
+ tls_update_rx_zc_capable(ctx);
+ rc = 0;
+ }
+ release_sock(sk);
+
+ return rc;
+}
+
static int do_tls_setsockopt(struct sock *sk, int optname, sockptr_t optval,
unsigned int optlen)
{
@@ -736,6 +802,9 @@ static int do_tls_setsockopt(struct sock *sk, int optname, sockptr_t optval,
rc = do_tls_setsockopt_tx_zc(sk, optval, optlen);
release_sock(sk);
break;
+ case TLS_RX_EXPECT_NO_PAD:
+ rc = do_tls_setsockopt_no_pad(sk, optval, optlen);
+ break;
default:
rc = -ENOPROTOOPT;
break;
@@ -976,6 +1045,11 @@ static int tls_get_info(const struct sock *sk, struct sk_buff *skb)
if (err)
goto nla_failure;
}
+ if (ctx->rx_no_pad) {
+ err = nla_put_flag(skb, TLS_INFO_RX_NO_PAD);
+ if (err)
+ goto nla_failure;
+ }
rcu_read_unlock();
nla_nest_end(skb, start);
@@ -997,6 +1071,7 @@ static size_t tls_get_info_size(const struct sock *sk)
nla_total_size(sizeof(u16)) + /* TLS_INFO_RXCONF */
nla_total_size(sizeof(u16)) + /* TLS_INFO_TXCONF */
nla_total_size(0) + /* TLS_INFO_ZC_RO_TX */
+ nla_total_size(0) + /* TLS_INFO_RX_NO_PAD */
0;
return size;
diff --git a/net/tls/tls_proc.c b/net/tls/tls_proc.c
index feeceb0e4cb4..0c200000cc45 100644
--- a/net/tls/tls_proc.c
+++ b/net/tls/tls_proc.c
@@ -18,6 +18,7 @@ static const struct snmp_mib tls_mib_list[] = {
SNMP_MIB_ITEM("TlsRxDevice", LINUX_MIB_TLSRXDEVICE),
SNMP_MIB_ITEM("TlsDecryptError", LINUX_MIB_TLSDECRYPTERROR),
SNMP_MIB_ITEM("TlsRxDeviceResync", LINUX_MIB_TLSRXDEVICERESYNC),
+ SNMP_MIB_ITEM("TlsDecryptRetry", LINUX_MIN_TLSDECRYPTRETRY),
SNMP_MIB_SENTINEL
};
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 2bac57684429..7592b6519953 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -1601,6 +1601,7 @@ static int decrypt_skb_update(struct sock *sk, struct sk_buff *skb,
if (unlikely(darg->zc && prot->version == TLS_1_3_VERSION &&
darg->tail != TLS_RECORD_TYPE_DATA)) {
darg->zc = false;
+ TLS_INC_STATS(sock_net(sk), LINUX_MIN_TLSDECRYPTRETRY);
return decrypt_skb_update(sk, skb, dest, darg);
}
@@ -1787,7 +1788,7 @@ int tls_sw_recvmsg(struct sock *sk,
timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
zc_capable = !bpf_strp_enabled && !is_kvec && !is_peek &&
- prot->version != TLS_1_3_VERSION;
+ ctx->zc_capable;
decrypted = 0;
while (len && (decrypted + copied < target || ctx->recv_pkt)) {
struct tls_decrypt_arg darg = {};
@@ -2269,6 +2270,14 @@ void tls_sw_strparser_arm(struct sock *sk, struct tls_context *tls_ctx)
strp_check_rcv(&rx_ctx->strp);
}
+void tls_update_rx_zc_capable(struct tls_context *tls_ctx)
+{
+ struct tls_sw_context_rx *rx_ctx = tls_sw_ctx_rx(tls_ctx);
+
+ rx_ctx->zc_capable = tls_ctx->rx_no_pad ||
+ tls_ctx->prot_info.version != TLS_1_3_VERSION;
+}
+
int tls_set_sw_offload(struct sock *sk, struct tls_context *ctx, int tx)
{
struct tls_context *tls_ctx = tls_get_ctx(sk);
@@ -2504,12 +2513,10 @@ int tls_set_sw_offload(struct sock *sk, struct tls_context *ctx, int tx)
if (sw_ctx_rx) {
tfm = crypto_aead_tfm(sw_ctx_rx->aead_recv);
- if (crypto_info->version == TLS_1_3_VERSION)
- sw_ctx_rx->async_capable = 0;
- else
- sw_ctx_rx->async_capable =
- !!(tfm->__crt_alg->cra_flags &
- CRYPTO_ALG_ASYNC);
+ tls_update_rx_zc_capable(ctx);
+ sw_ctx_rx->async_capable =
+ crypto_info->version != TLS_1_3_VERSION &&
+ !!(tfm->__crt_alg->cra_flags & CRYPTO_ALG_ASYNC);
/* Set up strparser */
memset(&cb, 0, sizeof(cb));
--
2.36.1
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