tcp: ulp: diag: more info without CAP_NET_ADMIN

When introduced in commit 61723b3 ("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, only some
metadata about the configuration, no cryptographic information. 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.

Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>

Author: matttbe

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);

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;

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;
@@ -56,22 +56,28 @@ 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))) {
 		err = -EMSGSIZE;
 		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;
 }
 

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;