[PATCH net-next 0/2] tcp: ulp: diag: expose more to non net admin users

[PATCH net-next 0/2] tcp: ulp: diag: expose more to non net admin users

[Matthieu Baerts (NGI0)]

Since its introduction in commit 61723b393292 ("tcp: ulp: add functions
to dump ulp-specific information"), the ULP diag info have been exported
only to users with CAP_NET_ADMIN capability.

Not everything is sensitive, and some info can be exported to all users
in order to ease the debugging from the userspace side without requiring
additional capabilities.

First, the ULP name can be easily exported. Then more depending on each
layer:

 - On kTLS side, it looks like everything can be exported to all users:
   version, cipher type, tx/rx user config type, plus some flags.

 - On MPTCP side, everything but the sequence numbers are exported to
   all non net admin users, similar to TCP.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
Matthieu Baerts (NGI0) (2):
      tcp: ulp: diag: always print the name if any
      tcp: ulp: diag: more info without CAP_NET_ADMIN

 include/net/tcp.h   |  4 ++--
 net/ipv4/tcp_diag.c | 21 ++++++++++-----------
 net/mptcp/diag.c    | 42 ++++++++++++++++++++++++++----------------
 net/tls/tls_main.c  |  4 ++--
 4 files changed, 40 insertions(+), 31 deletions(-)
---
base-commit: f130a0cc1b4ff1ef28a307428d40436032e2b66e
change-id: 20250306-net-next-tcp-ulp-diag-net-admin-a1d6d7f9910b

Best regards,
-- 
Matthieu Baerts (NGI0) <matttbe@kernel.org>

[PATCH net-next 1/2] tcp: ulp: diag: always print the name if any

[Matthieu Baerts (NGI0)]

Since its introduction in commit 61723b393292 ("tcp: ulp: add functions
to dump ulp-specific information"), the ULP diag info have been exported
only if the requester had CAP_NET_ADMIN.

At least the ULP name can be exported without CAP_NET_ADMIN. This will
already help identifying which layer is being used, e.g. which TCP
connections are in fact MPTCP subflow.

Acked-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/ipv4/tcp_diag.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/net/ipv4/tcp_diag.c b/net/ipv4/tcp_diag.c
index f428ecf9120f2f596e1d67db2b2a0d0d0e211905..d8bba37dbffd8c6cc7fab2328a88b6ce6ea3e9f4 100644
--- a/net/ipv4/tcp_diag.c
+++ b/net/ipv4/tcp_diag.c
@@ -83,7 +83,7 @@ static int tcp_diag_put_md5sig(struct sk_buff *skb,
 #endif
 
 static int tcp_diag_put_ulp(struct sk_buff *skb, struct sock *sk,
-			    const struct tcp_ulp_ops *ulp_ops)
+			    const struct tcp_ulp_ops *ulp_ops, bool net_admin)
 {
 	struct nlattr *nest;
 	int err;
@@ -96,7 +96,7 @@ static int tcp_diag_put_ulp(struct sk_buff *skb, struct sock *sk,
 	if (err)
 		goto nla_failure;
 
-	if (ulp_ops->get_info)
+	if (net_admin && ulp_ops->get_info)
 		err = ulp_ops->get_info(sk, skb);
 	if (err)
 		goto nla_failure;
@@ -113,6 +113,7 @@ static int tcp_diag_get_aux(struct sock *sk, bool net_admin,
 			    struct sk_buff *skb)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
+	const struct tcp_ulp_ops *ulp_ops;
 	int err = 0;
 
 #ifdef CONFIG_TCP_MD5SIG
@@ -129,15 +130,13 @@ static int tcp_diag_get_aux(struct sock *sk, bool net_admin,
 	}
 #endif
 
-	if (net_admin) {
-		const struct tcp_ulp_ops *ulp_ops;
-
-		ulp_ops = icsk->icsk_ulp_ops;
-		if (ulp_ops)
-			err = tcp_diag_put_ulp(skb, sk, ulp_ops);
-		if (err)
+	ulp_ops = icsk->icsk_ulp_ops;
+	if (ulp_ops) {
+		err = tcp_diag_put_ulp(skb, sk, ulp_ops, net_admin);
+		if (err < 0)
 			return err;
 	}
+
 	return 0;
 }
 
@@ -164,14 +163,14 @@ static size_t tcp_diag_get_aux_size(struct sock *sk, bool net_admin)
 	}
 #endif
 
-	if (net_admin && sk_fullsock(sk)) {
+	if (sk_fullsock(sk)) {
 		const struct tcp_ulp_ops *ulp_ops;
 
 		ulp_ops = icsk->icsk_ulp_ops;
 		if (ulp_ops) {
 			size += nla_total_size(0) +
 				nla_total_size(TCP_ULP_NAME_MAX);
-			if (ulp_ops->get_info_size)
+			if (net_admin && ulp_ops->get_info_size)
 				size += ulp_ops->get_info_size(sk);
 		}
 	}

-- 
2.47.1

[PATCH net-next 2/2] tcp: ulp: diag: more info without CAP_NET_ADMIN

[Matthieu Baerts (NGI0)]

When introduced in commit 61723b393292 ("tcp: ulp: add functions to dump
ulp-specific information"), the whole ULP diag info has been exported
only if the requester had CAP_NET_ADMIN.

It looks like not everything is sensitive, and some info can be exported
to all users in order to ease the debugging from the userspace side
without requiring additional capabilities. Each layer should then decide
what can be exposed to everybody. The 'net_admin' boolean is then passed
to the different layers.

On kTLS side, it looks like there is nothing sensitive there: version,
cipher type, tx/rx user config type, plus some flags. So, only some
metadata about the configuration, no cryptographic info like keys, etc.
Then, everything can be exported to all users.

On MPTCP side, that's different. The MPTCP-related sequence numbers per
subflow should certainly not be exposed to everybody. For example, the
DSS mapping and ssn_offset would give all users on the system access to
narrow ranges of values for the subflow TCP sequence numbers and
MPTCP-level DSNs, and then ease packet injection. The TCP diag interface
doesn't expose the TCP sequence numbers for TCP sockets, so best to do
the same here. The rest -- token, IDs, flags -- can be exported to
everybody.

Acked-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 include/net/tcp.h   |  4 ++--
 net/ipv4/tcp_diag.c |  8 ++++----
 net/mptcp/diag.c    | 42 ++++++++++++++++++++++++++----------------
 net/tls/tls_main.c  |  4 ++--
 4 files changed, 34 insertions(+), 24 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index a9bc959fb102fc6697b4a664b3773b47b3309f13..7207c52b1fc9ce3cd9cf2a8580310d0e629f82d6 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2598,8 +2598,8 @@ struct tcp_ulp_ops {
 	/* cleanup ulp */
 	void (*release)(struct sock *sk);
 	/* diagnostic */
-	int (*get_info)(struct sock *sk, struct sk_buff *skb);
-	size_t (*get_info_size)(const struct sock *sk);
+	int (*get_info)(struct sock *sk, struct sk_buff *skb, bool net_admin);
+	size_t (*get_info_size)(const struct sock *sk, bool net_admin);
 	/* clone ulp */
 	void (*clone)(const struct request_sock *req, struct sock *newsk,
 		      const gfp_t priority);
diff --git a/net/ipv4/tcp_diag.c b/net/ipv4/tcp_diag.c
index d8bba37dbffd8c6cc7fab2328a88b6ce6ea3e9f4..45e174b8cd22173b6b8eeffe71df334c45498b15 100644
--- a/net/ipv4/tcp_diag.c
+++ b/net/ipv4/tcp_diag.c
@@ -96,8 +96,8 @@ static int tcp_diag_put_ulp(struct sk_buff *skb, struct sock *sk,
 	if (err)
 		goto nla_failure;
 
-	if (net_admin && ulp_ops->get_info)
-		err = ulp_ops->get_info(sk, skb);
+	if (ulp_ops->get_info)
+		err = ulp_ops->get_info(sk, skb, net_admin);
 	if (err)
 		goto nla_failure;
 
@@ -170,8 +170,8 @@ static size_t tcp_diag_get_aux_size(struct sock *sk, bool net_admin)
 		if (ulp_ops) {
 			size += nla_total_size(0) +
 				nla_total_size(TCP_ULP_NAME_MAX);
-			if (net_admin && ulp_ops->get_info_size)
-				size += ulp_ops->get_info_size(sk);
+			if (ulp_ops->get_info_size)
+				size += ulp_ops->get_info_size(sk, net_admin);
 		}
 	}
 	return size;
diff --git a/net/mptcp/diag.c b/net/mptcp/diag.c
index 02205f7994d752cc505991efdf7aa0bbbfd830db..70cf9ebce8338bde3b0bb10fc8620905b15f5190 100644
--- a/net/mptcp/diag.c
+++ b/net/mptcp/diag.c
@@ -12,7 +12,7 @@
 #include <net/netlink.h>
 #include "protocol.h"
 
-static int subflow_get_info(struct sock *sk, struct sk_buff *skb)
+static int subflow_get_info(struct sock *sk, struct sk_buff *skb, bool net_admin)
 {
 	struct mptcp_subflow_context *sf;
 	struct nlattr *start;
@@ -56,15 +56,6 @@ static int subflow_get_info(struct sock *sk, struct sk_buff *skb)
 
 	if (nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_TOKEN_REM, sf->remote_token) ||
 	    nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_TOKEN_LOC, sf->token) ||
-	    nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_RELWRITE_SEQ,
-			sf->rel_write_seq) ||
-	    nla_put_u64_64bit(skb, MPTCP_SUBFLOW_ATTR_MAP_SEQ, sf->map_seq,
-			      MPTCP_SUBFLOW_ATTR_PAD) ||
-	    nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_MAP_SFSEQ,
-			sf->map_subflow_seq) ||
-	    nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_SSN_OFFSET, sf->ssn_offset) ||
-	    nla_put_u16(skb, MPTCP_SUBFLOW_ATTR_MAP_DATALEN,
-			sf->map_data_len) ||
 	    nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_FLAGS, flags) ||
 	    nla_put_u8(skb, MPTCP_SUBFLOW_ATTR_ID_REM, sf->remote_id) ||
 	    nla_put_u8(skb, MPTCP_SUBFLOW_ATTR_ID_LOC, subflow_get_local_id(sf))) {
@@ -72,6 +63,21 @@ static int subflow_get_info(struct sock *sk, struct sk_buff *skb)
 		goto nla_failure;
 	}
 
+	/* Only export seq related counters to user with CAP_NET_ADMIN */
+	if (net_admin &&
+	    (nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_RELWRITE_SEQ,
+			 sf->rel_write_seq) ||
+	     nla_put_u64_64bit(skb, MPTCP_SUBFLOW_ATTR_MAP_SEQ, sf->map_seq,
+			       MPTCP_SUBFLOW_ATTR_PAD) ||
+	     nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_MAP_SFSEQ,
+			 sf->map_subflow_seq) ||
+	     nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_SSN_OFFSET, sf->ssn_offset) ||
+	     nla_put_u16(skb, MPTCP_SUBFLOW_ATTR_MAP_DATALEN,
+			 sf->map_data_len))) {
+		err = -EMSGSIZE;
+		goto nla_failure;
+	}
+
 	rcu_read_unlock();
 	unlock_sock_fast(sk, slow);
 	nla_nest_end(skb, start);
@@ -84,22 +90,26 @@ static int subflow_get_info(struct sock *sk, struct sk_buff *skb)
 	return err;
 }
 
-static size_t subflow_get_info_size(const struct sock *sk)
+static size_t subflow_get_info_size(const struct sock *sk, bool net_admin)
 {
 	size_t size = 0;
 
 	size += nla_total_size(0) +	/* INET_ULP_INFO_MPTCP */
 		nla_total_size(4) +	/* MPTCP_SUBFLOW_ATTR_TOKEN_REM */
 		nla_total_size(4) +	/* MPTCP_SUBFLOW_ATTR_TOKEN_LOC */
-		nla_total_size(4) +	/* MPTCP_SUBFLOW_ATTR_RELWRITE_SEQ */
-		nla_total_size_64bit(8) +	/* MPTCP_SUBFLOW_ATTR_MAP_SEQ */
-		nla_total_size(4) +	/* MPTCP_SUBFLOW_ATTR_MAP_SFSEQ */
-		nla_total_size(4) +	/* MPTCP_SUBFLOW_ATTR_SSN_OFFSET */
-		nla_total_size(2) +	/* MPTCP_SUBFLOW_ATTR_MAP_DATALEN */
 		nla_total_size(4) +	/* MPTCP_SUBFLOW_ATTR_FLAGS */
 		nla_total_size(1) +	/* MPTCP_SUBFLOW_ATTR_ID_REM */
 		nla_total_size(1) +	/* MPTCP_SUBFLOW_ATTR_ID_LOC */
 		0;
+
+	if (net_admin)
+		size += nla_total_size(4) +	/* MPTCP_SUBFLOW_ATTR_RELWRITE_SEQ */
+			nla_total_size_64bit(8) +	/* MPTCP_SUBFLOW_ATTR_MAP_SEQ */
+			nla_total_size(4) +	/* MPTCP_SUBFLOW_ATTR_MAP_SFSEQ */
+			nla_total_size(4) +	/* MPTCP_SUBFLOW_ATTR_SSN_OFFSET */
+			nla_total_size(2) +	/* MPTCP_SUBFLOW_ATTR_MAP_DATALEN */
+			0;
+
 	return size;
 }
 
diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index 99ca4465f70216c5a44e4ca7477df0e93df6b76d..cb86b0bf9a53e1ff060d8e69eddbd6acfbee5194 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -1057,7 +1057,7 @@ static u16 tls_user_config(struct tls_context *ctx, bool tx)
 	return 0;
 }
 
-static int tls_get_info(struct sock *sk, struct sk_buff *skb)
+static int tls_get_info(struct sock *sk, struct sk_buff *skb, bool net_admin)
 {
 	u16 version, cipher_type;
 	struct tls_context *ctx;
@@ -1115,7 +1115,7 @@ static int tls_get_info(struct sock *sk, struct sk_buff *skb)
 	return err;
 }
 
-static size_t tls_get_info_size(const struct sock *sk)
+static size_t tls_get_info_size(const struct sock *sk, bool net_admin)
 {
 	size_t size = 0;
 

-- 
2.47.1

Re: [PATCH net-next 0/2] tcp: ulp: diag: expose more to non net admin users

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Thu, 06 Mar 2025 12:29:26 +0100 you wrote:
> Since its introduction in commit 61723b393292 ("tcp: ulp: add functions
> to dump ulp-specific information"), the ULP diag info have been exported
> only to users with CAP_NET_ADMIN capability.
> 
> Not everything is sensitive, and some info can be exported to all users
> in order to ease the debugging from the userspace side without requiring
> additional capabilities.
> 
> [...]

Here is the summary with links:
  - [net-next,1/2] tcp: ulp: diag: always print the name if any
    https://git.kernel.org/netdev/net-next/c/f5afcb9fbb39
  - [net-next,2/2] tcp: ulp: diag: more info without CAP_NET_ADMIN
    https://git.kernel.org/netdev/net-next/c/0d7336f8f06d

You are awesome, thank you!
-- 
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