tcp: md5: add TCP_MD5SIG_EXT socket option to set a key address prefix

Replace first padding in the tcp_md5sig structure with a new flag field
and address prefix length so it can be specified when configuring a new
key for TCP MD5 signature. The tcpm_flags field will only be used if the
socket option is TCP_MD5SIG_EXT to avoid breaking existing programs, and
tcpm_prefixlen only when the TCP_MD5SIG_FLAG_PREFIX flag is set.

Signed-off-by: Bob Gilligan <[e-mail]>
Signed-off-by: Eric Mowat <[e-mail]>
Signed-off-by: Ivan Delalande <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/tcp.h

···
 					 const struct sock *sk,
 					 const struct sk_buff *skb);
 	int		(*md5_parse)(struct sock *sk,
+				     int optname,
 				     char __user *optval,
 				     int optlen);
 #endif

include/uapi/linux/tcp.h

···
 #define TCP_SAVED_SYN		28	/* Get SYN headers recorded for connection */
 #define TCP_REPAIR_WINDOW	29	/* Get/set window parameters */
 #define TCP_FASTOPEN_CONNECT	30	/* Attempt FastOpen with connect */
-#define TCP_ULP		31	/* Attach a ULP to a TCP connection */
+#define TCP_ULP			31	/* Attach a ULP to a TCP connection */
+#define TCP_MD5SIG_EXT		32	/* TCP MD5 Signature with extensions */
 
 struct tcp_repair_opt {
 	__u32	opt_code;
···
 /* for TCP_MD5SIG socket option */
 #define TCP_MD5SIG_MAXKEYLEN	80
 
+/* tcp_md5sig extension flags for TCP_MD5SIG_EXT */
+#define TCP_MD5SIG_FLAG_PREFIX		1	/* address prefix length */
+
 struct tcp_md5sig {
 	struct __kernel_sockaddr_storage tcpm_addr;	/* address associated */
-	__u16	__tcpm_pad1;				/* zero */
+	__u8	tcpm_flags;				/* extension flags */
+	__u8	tcpm_prefixlen;				/* address prefix */
 	__u16	tcpm_keylen;				/* key length */
-	__u32	__tcpm_pad2;				/* zero */
+	__u32	__tcpm_pad;				/* zero */
 	__u8	tcpm_key[TCP_MD5SIG_MAXKEYLEN];		/* key (binary) */
 };
 

net/ipv4/tcp.c

···
 
 #ifdef CONFIG_TCP_MD5SIG
 	case TCP_MD5SIG:
+	case TCP_MD5SIG_EXT:
 		/* Read the IP->Key mappings from userspace */
-		err = tp->af_specific->md5_parse(sk, optval, optlen);
+		err = tp->af_specific->md5_parse(sk, optname, optval, optlen);
 		break;
 #endif
 	case TCP_USER_TIMEOUT:

net/ipv4/tcp_ipv4.c

···
 	}
 }
 
-static int tcp_v4_parse_md5_keys(struct sock *sk, char __user *optval,
-				 int optlen)
+static int tcp_v4_parse_md5_keys(struct sock *sk, int optname,
+				 char __user *optval, int optlen)
 {
 	struct tcp_md5sig cmd;
 	struct sockaddr_in *sin = (struct sockaddr_in *)&cmd.tcpm_addr;
+	u8 prefixlen = 32;
 
 	if (optlen < sizeof(cmd))
 		return -EINVAL;
···
 	if (sin->sin_family != AF_INET)
 		return -EINVAL;
 
+	if (optname == TCP_MD5SIG_EXT &&
+	    cmd.tcpm_flags & TCP_MD5SIG_FLAG_PREFIX) {
+		prefixlen = cmd.tcpm_prefixlen;
+		if (prefixlen > 32)
+			return -EINVAL;
+	}
+
 	if (!cmd.tcpm_keylen)
 		return tcp_md5_do_del(sk, (union tcp_md5_addr *)&sin->sin_addr.s_addr,
-				      AF_INET, 32);
+				      AF_INET, prefixlen);
 
 	if (cmd.tcpm_keylen > TCP_MD5SIG_MAXKEYLEN)
 		return -EINVAL;
 
 	return tcp_md5_do_add(sk, (union tcp_md5_addr *)&sin->sin_addr.s_addr,
-			      AF_INET, 32, cmd.tcpm_key, cmd.tcpm_keylen,
+			      AF_INET, prefixlen, cmd.tcpm_key, cmd.tcpm_keylen,
 			      GFP_KERNEL);
 }
 

net/ipv6/tcp_ipv6.c

···
 	return tcp_v6_md5_do_lookup(sk, &addr_sk->sk_v6_daddr);
 }
 
-static int tcp_v6_parse_md5_keys(struct sock *sk, char __user *optval,
-				 int optlen)
+static int tcp_v6_parse_md5_keys(struct sock *sk, int optname,
+				 char __user *optval, int optlen)
 {
 	struct tcp_md5sig cmd;
 	struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)&cmd.tcpm_addr;
+	u8 prefixlen;
 
 	if (optlen < sizeof(cmd))
 		return -EINVAL;
···
 	if (sin6->sin6_family != AF_INET6)
 		return -EINVAL;
 
+	if (optname == TCP_MD5SIG_EXT &&
+	    cmd.tcpm_flags & TCP_MD5SIG_FLAG_PREFIX) {
+		prefixlen = cmd.tcpm_prefixlen;
+		if (prefixlen > 128 || (ipv6_addr_v4mapped(&sin6->sin6_addr) &&
+					prefixlen > 32))
+			return -EINVAL;
+	} else {
+		prefixlen = ipv6_addr_v4mapped(&sin6->sin6_addr) ? 32 : 128;
+	}
+
 	if (!cmd.tcpm_keylen) {
 		if (ipv6_addr_v4mapped(&sin6->sin6_addr))
 			return tcp_md5_do_del(sk, (union tcp_md5_addr *)&sin6->sin6_addr.s6_addr32[3],
-					      AF_INET, 32);
+					      AF_INET, prefixlen);
 		return tcp_md5_do_del(sk, (union tcp_md5_addr *)&sin6->sin6_addr,
-				      AF_INET6, 128);
+				      AF_INET6, prefixlen);
 	}
 
 	if (cmd.tcpm_keylen > TCP_MD5SIG_MAXKEYLEN)
···
 
 	if (ipv6_addr_v4mapped(&sin6->sin6_addr))
 		return tcp_md5_do_add(sk, (union tcp_md5_addr *)&sin6->sin6_addr.s6_addr32[3],
-				      AF_INET, 32, cmd.tcpm_key,
+				      AF_INET, prefixlen, cmd.tcpm_key,
 				      cmd.tcpm_keylen, GFP_KERNEL);
 
 	return tcp_md5_do_add(sk, (union tcp_md5_addr *)&sin6->sin6_addr,
-			      AF_INET6, 128, cmd.tcpm_key, cmd.tcpm_keylen,
-			      GFP_KERNEL);
+			      AF_INET6, prefixlen, cmd.tcpm_key,
+			      cmd.tcpm_keylen, GFP_KERNEL);
 }
 
 static int tcp_v6_md5_hash_headers(struct tcp_md5sig_pool *hp,