[PATCH net-next v5 2/2] tcp_diag: report TCP MD5 signing keys and addresses

Ivan Delalande
2017-08-31T16:59:40Z

Report TCP MD5 (RFC2385) signing keys, addresses and address prefixes to
processes with CAP_NET_ADMIN requesting INET_DIAG_INFO. Currently it is
not possible to retrieve these from the kernel once they have been
configured on sockets.

Signed-off-by: Ivan Delalande <colona@arista.com>
---
include/uapi/linux/inet_diag.h | 1 +
include/uapi/linux/tcp.h | 9 ++++
net/ipv4/tcp_diag.c | 109 ++++++++++++++++++++++++++++++++++++++---
3 files changed, 113 insertions(+), 6 deletions(-)

diff --git a/include/uapi/linux/inet_diag.h b/include/uapi/linux/inet_diag.h
index 678496897a68..f52ff62bfabe 100644
--- a/include/uapi/linux/inet_diag.h
+++ b/include/uapi/linux/inet_diag.h
@@ -143,6 +143,7 @@ enum {
INET_DIAG_MARK,
INET_DIAG_BBRINFO,
INET_DIAG_CLASS_ID,
+ INET_DIAG_MD5SIG,
__INET_DIAG_MAX,
};

diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 030e594bab45..15c25eccab2b 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -256,4 +256,13 @@ struct tcp_md5sig {
__u8 tcpm_key[TCP_MD5SIG_MAXKEYLEN]; /* key (binary) */
};

+/* INET_DIAG_MD5SIG */
+struct tcp_diag_md5sig {
+ __u8 tcpm_family;
+ __u8 tcpm_prefixlen;
+ __u16 tcpm_keylen;
+ __be32 tcpm_addr[4];
+ __u8 tcpm_key[TCP_MD5SIG_MAXKEYLEN];
+};
+
#endif /* _UAPI_LINUX_TCP_H */
diff --git a/net/ipv4/tcp_diag.c b/net/ipv4/tcp_diag.c
index a748c74aa8b7..abbf0edcf6c2 100644
--- a/net/ipv4/tcp_diag.c
+++ b/net/ipv4/tcp_diag.c
@@ -16,6 +16,7 @@

#include <linux/tcp.h>

+#include <net/netlink.h>
#include <net/tcp.h>

static void tcp_diag_get_info(struct sock *sk, struct inet_diag_msg *r,
@@ -36,6 +37,100 @@ static void tcp_diag_get_info(struct sock *sk, struct inet_diag_msg *r,
tcp_get_info(sk, info);
}

+#ifdef CONFIG_TCP_MD5SIG
+static void tcp_diag_md5sig_fill(struct tcp_diag_md5sig *info,
+ const struct tcp_md5sig_key *key)
+{
+ info->tcpm_family = key->family;
+ info->tcpm_prefixlen = key->prefixlen;
+ info->tcpm_keylen = key->keylen;
+ memcpy(info->tcpm_key, key->key, key->keylen);
+
+ if (key->family == AF_INET)
+ info->tcpm_addr[0] = key->addr.a4.s_addr;
+ #if IS_ENABLED(CONFIG_IPV6)
+ else if (key->family == AF_INET6)
+ memcpy(&info->tcpm_addr, &key->addr.a6,
+ sizeof(info->tcpm_addr));
+ #endif
+}
+
+static int tcp_diag_put_md5sig(struct sk_buff *skb,
+ const struct tcp_md5sig_info *md5sig)
+{
+ const struct tcp_md5sig_key *key;
+ struct tcp_diag_md5sig *info;
+ struct nlattr *attr;
+ int md5sig_count = 0;
+
+ hlist_for_each_entry_rcu(key, &md5sig->head, node)
+ md5sig_count++;
+ if (md5sig_count == 0)
+ return 0;
+
+ attr = nla_reserve(skb, INET_DIAG_MD5SIG,
+ md5sig_count * sizeof(struct tcp_diag_md5sig));
+ if (!attr)
+ return -EMSGSIZE;
+
+ info = nla_data(attr);
+ memset(info, 0, md5sig_count * sizeof(struct tcp_diag_md5sig));
+ hlist_for_each_entry_rcu(key, &md5sig->head, node) {
+ tcp_diag_md5sig_fill(info++, key);
+ if (--md5sig_count == 0)
+ break;
+ }
+
+ return 0;
+}
+#endif
+
+static int tcp_diag_get_aux(struct sock *sk, bool net_admin,
+ struct sk_buff *skb)
+{
+#ifdef CONFIG_TCP_MD5SIG
+ if (net_admin) {
+ struct tcp_md5sig_info *md5sig;
+ int err = 0;
+
+ rcu_read_lock();
+ md5sig = rcu_dereference(tcp_sk(sk)->md5sig_info);
+ if (md5sig)
+ err = tcp_diag_put_md5sig(skb, md5sig);
+ rcu_read_unlock();
+ if (err < 0)
+ return err;
+ }
+#endif
+
+ return 0;
+}
+
+static size_t tcp_diag_get_aux_size(struct sock *sk, bool net_admin)
+{
+ size_t size = 0;
+
+#ifdef CONFIG_TCP_MD5SIG
+ if (net_admin && sk_fullsock(sk)) {
+ const struct tcp_md5sig_info *md5sig;
+ const struct tcp_md5sig_key *key;
+ size_t md5sig_count = 0;
+
+ rcu_read_lock();
+ md5sig = rcu_dereference(tcp_sk(sk)->md5sig_info);
+ if (md5sig) {
+ hlist_for_each_entry_rcu(key, &md5sig->head, node)
+ md5sig_count++;
+ }
+ rcu_read_unlock();
+ size += nla_total_size(md5sig_count *
+ sizeof(struct tcp_diag_md5sig));
+ }
+#endif
+
+ return size;
+}
+
static void tcp_diag_dump(struct sk_buff *skb, struct netlink_callback *cb,
const struct inet_diag_req_v2 *r, struct nlattr *bc)
{
@@ -68,13 +163,15 @@ static int tcp_diag_destroy(struct sk_buff *in_skb,
#endif

static const struct inet_diag_handler tcp_diag_handler = {
- .dump = tcp_diag_dump,
- .dump_one = tcp_diag_dump_one,
- .idiag_get_info = tcp_diag_get_info,
- .idiag_type = IPPROTO_TCP,
- .idiag_info_size = sizeof(struct tcp_info),
+ .dump = tcp_diag_dump,
+ .dump_one = tcp_diag_dump_one,
+ .idiag_get_info = tcp_diag_get_info,
+ .idiag_get_aux = tcp_diag_get_aux,
+ .idiag_get_aux_size = tcp_diag_get_aux_size,
+ .idiag_type = IPPROTO_TCP,
+ .idiag_info_size = sizeof(struct tcp_info),
#ifdef CONFIG_INET_DIAG_DESTROY
- .destroy = tcp_diag_destroy,
+ .destroy = tcp_diag_destroy,
#endif
};

--
2.14.1