BSD: Add the IPsec SA/SP database entries control

Add code for manipulation with TCP-MD5 keys in the IPsec SA/SP database
at FreeBSD systems. Now, BGP MD5 authentication (RFC 2385) keys are
handled automatically on both Linux and FreeBSD.

Based on patches from Pavel Tvrdik.

10 files changed, 226 insertions, 34 deletions

diff --git a/doc/bird.sgml b/doc/bird.sgml
index 653e0bb5..1a5fbaff 100644
--- a/doc/bird.sgml
+++ b/doc/bird.sgml
@@ -1764,9 +1764,20 @@ using the following configuration parameters:
 	only. Default: disabled.
 
 	<tag>password <m/string/</tag>
-	Use this password for MD5 authentication of BGP sessions. Default: no
-	authentication. Password has to be set by external utility
-	(e.g. setkey(8)) on BSD systems.
+	Use this password for MD5 authentication of BGP sessions (RFC 2385).
+	When used on BSD systems, see also <cf/setkey/ option below. Default:
+	no authentication.
+
+	<tag>setkey <m/switch/</tag>
+	On BSD systems, keys for TCP MD5 authentication are stored in the global
+	SA/SP database, which can be accessed by external utilities (e.g.
+	setkey(8)). BIRD configures security associations in the SA/SP database
+	automatically based on <cf/password/ options (see above), this option
+	allows to disable automatic updates by BIRD when manual configuration by
+	external utilities is preferred. Note that automatic SA/SP database
+	updates are currently implemented only for FreeBSD. Passwords have to be
+	set manually by an external utility on NetBSD and OpenBSD. Default:
+	enabled (ignored on non-FreeBSD).
 
 	<tag>passive <m/switch/</tag>
 	Standard BGP behavior is both initiating outgoing connections and
diff --git a/lib/socket.h b/lib/socket.h
index 0327e9e5..6babfa7b 100644
--- a/lib/socket.h
+++ b/lib/socket.h
@@ -87,7 +87,7 @@ int sk_leave_group(sock *s, ip_addr maddr);	/* Leave multicast group on sk iface
 int sk_setup_broadcast(sock *s);
 int sk_set_ttl(sock *s, int ttl);	/* Set transmit TTL for given socket */
 int sk_set_min_ttl(sock *s, int ttl);	/* Set minimal accepted TTL for given socket */
-int sk_set_md5_auth(sock *s, ip_addr a, struct iface *ifa, char *passwd);
+int sk_set_md5_auth(sock *s, ip_addr local, ip_addr remote, struct iface *ifa, char *passwd, int setkey);
 int sk_set_ipv6_checksum(sock *s, int offset);
 int sk_set_icmp6_filter(sock *s, int p1, int p2);
 void sk_log_error(sock *s, const char *p);
diff --git a/proto/bgp/bgp.c b/proto/bgp/bgp.c
index 94c8e5c2..2014525e 100644
--- a/proto/bgp/bgp.c
+++ b/proto/bgp/bgp.c
@@ -121,7 +121,8 @@ bgp_open(struct bgp_proto *p)
   bgp_counter++;
 
   if (p->cf->password)
-    if (sk_set_md5_auth(bgp_listen_sk, p->cf->remote_ip, p->cf->iface, p->cf->password) < 0)
+    if (sk_set_md5_auth(bgp_listen_sk, p->cf->source_addr, p->cf->remote_ip,
+			p->cf->iface, p->cf->password, p->cf->setkey) < 0)
       {
 	sk_log_error(bgp_listen_sk, p->p.name);
 	bgp_close(p, 0);
@@ -191,7 +192,8 @@ bgp_close(struct bgp_proto *p, int apply_md5)
   bgp_counter--;
 
   if (p->cf->password && apply_md5)
-    if (sk_set_md5_auth(bgp_listen_sk, p->cf->remote_ip, p->cf->iface, NULL) < 0)
+    if (sk_set_md5_auth(bgp_listen_sk, p->cf->source_addr, p->cf->remote_ip,
+			p->cf->iface, NULL, p->cf->setkey) < 0)
       sk_log_error(bgp_listen_sk, p->p.name);
 
   if (!bgp_counter)
diff --git a/proto/bgp/bgp.h b/proto/bgp/bgp.h
index 274794f1..b1cca2d9 100644
--- a/proto/bgp/bgp.h
+++ b/proto/bgp/bgp.h
@@ -51,6 +51,7 @@ struct bgp_config {
   int add_path;				/* Use ADD-PATH extension [draft] */
   int allow_local_as;			/* Allow that number of local ASNs in incoming AS_PATHs */
   int gr_mode;				/* Graceful restart mode (BGP_GR_*) */
+  int setkey;				/* Set MD5 password to system SA/SP database */
   unsigned gr_time;			/* Graceful restart timeout */
   unsigned connect_delay_time;		/* Minimum delay between connect attempts */
   unsigned connect_retry_time;		/* Timeout for connect attempts */
diff --git a/proto/bgp/config.Y b/proto/bgp/config.Y
index 85b93a6b..f3ba0e16 100644
--- a/proto/bgp/config.Y
+++ b/proto/bgp/config.Y
@@ -27,7 +27,7 @@ CF_KEYWORDS(BGP, LOCAL, NEIGHBOR, AS, HOLD, TIME, CONNECT, RETRY,
 	INTERPRET, COMMUNITIES, BGP_ORIGINATOR_ID, BGP_CLUSTER_LIST, IGP,
 	TABLE, GATEWAY, DIRECT, RECURSIVE, MED, TTL, SECURITY, DETERMINISTIC,
 	SECONDARY, ALLOW, BFD, ADD, PATHS, RX, TX, GRACEFUL, RESTART, AWARE,
-	CHECK, LINK, PORT, EXTENDED, MESSAGES)
+	CHECK, LINK, PORT, EXTENDED, MESSAGES, SETKEY)
 
 CF_GRAMMAR
 
@@ -54,6 +54,7 @@ bgp_proto_start: proto_start BGP {
      BGP_CFG->default_local_pref = 100;
      BGP_CFG->gr_mode = BGP_GR_AWARE;
      BGP_CFG->gr_time = 120;
+     BGP_CFG->setkey = 1;
  }
  ;
 
@@ -112,6 +113,7 @@ bgp_proto:
  | bgp_proto CAPABILITIES bool ';' { BGP_CFG->capabilities = $3; }
  | bgp_proto ADVERTISE IPV4 bool ';' { BGP_CFG->advertise_ipv4 = $4; }
  | bgp_proto PASSWORD text ';' { BGP_CFG->password = $3; }
+ | bgp_proto SETKEY bool ';' { BGP_CFG->setkey = $3; }
  | bgp_proto ROUTE LIMIT expr ';' {
      this_proto->in_limit = cfg_allocz(sizeof(struct proto_limit));
      this_proto->in_limit->limit = $4;
diff --git a/sysdep/bsd/Modules b/sysdep/bsd/Modules
index 96455db7..39db88e9 100644
--- a/sysdep/bsd/Modules
+++ b/sysdep/bsd/Modules
@@ -2,3 +2,4 @@ krt-sock.c
 krt-sock.Y
 krt-sys.h
 sysio.h
+setkey.h
diff --git a/sysdep/bsd/setkey.h b/sysdep/bsd/setkey.h
new file mode 100644
index 00000000..b417faca
--- /dev/null
+++ b/sysdep/bsd/setkey.h
@@ -0,0 +1,170 @@
+/*
+ *	BIRD -- Manipulation the IPsec SA/SP database using setkey(8) utility
+ *
+ * 	(c) 2016 CZ.NIC z.s.p.o.
+ */
+
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <net/pfkeyv2.h>
+#include <netipsec/ipsec.h>
+
+#include "nest/bird.h"
+#include "lib/unix.h"
+
+
+/*
+ * Open a socket for manage the IPsec SA/SP database entries
+ */
+static int
+setkey_open_socket(void)
+{
+  int s = socket(PF_KEY, SOCK_RAW, PF_KEY_V2);
+  if (s < 0)
+  {
+    log(L_ERR "SETKEY: socket: %m");
+    return -1;
+  }
+
+  return s;
+}
+
+static int
+setkey_send(struct sadb_msg *msg, uint len)
+{
+  int s = setkey_open_socket();
+  if (s < 0)
+    return -1;
+
+  if (msg->sadb_msg_type == SADB_ADD)
+  {
+    /* Delete possible current key in the IPsec SA/SP database */
+    msg->sadb_msg_type = SADB_DELETE;
+    send(s, msg, len, 0);
+    msg->sadb_msg_type = SADB_ADD;
+  }
+
+  if (send(s, msg, len, 0) < 0)
+  {
+    log(L_ERR "SETKEY: send: %m");
+    close(s);
+    return -1;
+  }
+
+  close(s);
+  return 0;
+}
+
+/*
+ * Perform setkey(8)-like operation for set the password for TCP MD5 Signature.
+ * Could be called with SABD_ADD or SADB_DELETE argument. Note that SADB_ADD
+ * argument is internally processed as a pair of SADB_ADD and SADB_DELETE
+ * operations to implement replace.
+ */
+static int
+setkey_md5(sockaddr *src, sockaddr *dst, char *passwd, uint type)
+{
+  uint passwd_len = passwd ? strlen(passwd) : 0;
+
+  uint total =
+    sizeof(struct sadb_msg) +
+    sizeof(struct sadb_key) + PFKEY_ALIGN8(passwd_len) +
+    sizeof(struct sadb_sa) +
+    sizeof(struct sadb_x_sa2) +
+    sizeof(struct sadb_address) + PFKEY_ALIGN8(src->sa.sa_len) +
+    sizeof(struct sadb_address) + PFKEY_ALIGN8(dst->sa.sa_len);
+
+  char *buf = alloca(total);
+  char *pos = buf;
+  uint len;
+
+  memset(buf, 0, total);
+
+  struct sadb_msg *msg = (void *) pos;
+  len = sizeof(struct sadb_msg);
+  msg->sadb_msg_version = PF_KEY_V2;
+  msg->sadb_msg_type = type;
+  msg->sadb_msg_satype = SADB_X_SATYPE_TCPSIGNATURE;
+  msg->sadb_msg_len = 0;	/* Fix it later */
+  msg->sadb_msg_pid = getpid();
+  pos += len;
+
+  /* Set authentication algorithm and password */
+  struct sadb_key *key = (void *) pos;
+  len = sizeof(struct sadb_key) + PFKEY_ALIGN8(passwd_len);
+  key->sadb_key_len = PFKEY_UNIT64(len);
+  key->sadb_key_exttype = SADB_EXT_KEY_AUTH;
+  key->sadb_key_bits = passwd_len * 8;
+  memcpy(pos + sizeof(struct sadb_key), passwd, passwd_len);
+  pos += len;
+
+  struct sadb_sa *sa = (void *) pos;
+  len = sizeof(struct sadb_sa);
+  sa->sadb_sa_len = PFKEY_UNIT64(len);
+  sa->sadb_sa_exttype = SADB_EXT_SA;
+  sa->sadb_sa_spi = htonl((u32) TCP_SIG_SPI);
+  sa->sadb_sa_auth = SADB_X_AALG_TCP_MD5;
+  sa->sadb_sa_encrypt = SADB_EALG_NONE;
+  sa->sadb_sa_flags = SADB_X_EXT_CYCSEQ;
+  pos += len;
+
+  struct sadb_x_sa2 *sa2 = (void *) pos;
+  len = sizeof(struct sadb_x_sa2);
+  sa2->sadb_x_sa2_len = PFKEY_UNIT64(len);
+  sa2->sadb_x_sa2_exttype = SADB_X_EXT_SA2;
+  sa2->sadb_x_sa2_mode = IPSEC_MODE_ANY;
+  pos += len;
+
+  /* Set source address */
+  struct sadb_address *saddr = (void *) pos;
+  len = sizeof(struct sadb_address) + PFKEY_ALIGN8(src->sa.sa_len);
+  saddr->sadb_address_len = PFKEY_UNIT64(len);
+  saddr->sadb_address_exttype = SADB_EXT_ADDRESS_SRC;
+  saddr->sadb_address_proto = IPSEC_ULPROTO_ANY;
+  saddr->sadb_address_prefixlen = MAX_PREFIX_LENGTH;
+  memcpy(pos + sizeof(struct sadb_address), &src->sa, src->sa.sa_len);
+  pos += len;
+
+  /* Set destination address */
+  struct sadb_address *daddr = (void *) pos;
+  len = sizeof(struct sadb_address) + PFKEY_ALIGN8(dst->sa.sa_len);
+  daddr->sadb_address_len = PFKEY_UNIT64(len);
+  daddr->sadb_address_exttype = SADB_EXT_ADDRESS_DST;
+  daddr->sadb_address_proto = IPSEC_ULPROTO_ANY;
+  daddr->sadb_address_prefixlen = MAX_PREFIX_LENGTH;
+  memcpy(pos + sizeof(struct sadb_address), &dst->sa, dst->sa.sa_len);
+  pos += len;
+
+  len = pos - buf;
+  msg->sadb_msg_len = PFKEY_UNIT64(len);
+
+  return setkey_send(msg, len);
+}
+
+/*
+ * Manipulation with the IPsec SA/SP database
+ */
+static int
+sk_set_md5_in_sasp_db(sock *s, ip_addr local, ip_addr remote, struct iface *ifa, char *passwd)
+{
+  sockaddr src, dst;
+  sockaddr_fill(&src, s->af, local, ifa, 0);
+  sockaddr_fill(&dst, s->af, remote, ifa, 0);
+
+  if (passwd && *passwd)
+  {
+    int len = strlen(passwd);
+    if (len > TCP_KEYLEN_MAX)
+      ERR_MSG("The password for TCP MD5 Signature is too long");
+
+    if (setkey_md5(&src, &dst, passwd, SADB_ADD) < 0)
+      ERR_MSG("Cannot add TCP-MD5 password into the IPsec SA/SP database");
+  }
+  else
+  {
+    if (setkey_md5(&src, &dst, NULL, SADB_DELETE) < 0)
+      ERR_MSG("Cannot delete TCP-MD5 password from the IPsec SA/SP database");
+  }
+  return 0;
+}
diff --git a/sysdep/bsd/sysio.h b/sysdep/bsd/sysio.h
index c82d7a1e..6c20733f 100644
--- a/sysdep/bsd/sysio.h
+++ b/sysdep/bsd/sysio.h
@@ -189,30 +189,26 @@ sk_prepare_ip_header(sock *s, void *hdr, int dlen)
 #ifndef TCP_KEYLEN_MAX
 #define TCP_KEYLEN_MAX 80
 #endif
+
 #ifndef TCP_SIG_SPI
 #define TCP_SIG_SPI 0x1000
 #endif
 
-/* 
- * FIXME: Passwords has to be set by setkey(8) command. This is the same
- * behaviour like Quagga. We need to add code for SA/SP entries
- * management.
- */
+#if defined(__FreeBSD__)
+#define USE_MD5SIG_SETKEY
+#include "lib/setkey.h"
+#endif
 
 int
-sk_set_md5_auth(sock *s, ip_addr a, struct iface *ifa, char *passwd)
+sk_set_md5_auth(sock *s, ip_addr local, ip_addr remote, struct iface *ifa, char *passwd, int setkey UNUSED)
 {
-  int enable = 0;
-
-  if (passwd && *passwd)
-  {
-    int len = strlen(passwd);
-    enable = TCP_SIG_SPI;
-
-    if (len > TCP_KEYLEN_MAX)
-      ERR_MSG("MD5 password too long");
-  }
+#ifdef USE_MD5SIG_SETKEY
+  if (setkey)
+    if (sk_set_md5_in_sasp_db(s, local, remote, ifa, passwd) < 0)
+      return -1;
+#endif
 
+  int enable = (passwd && *passwd) ? TCP_SIG_SPI : 0;
   if (setsockopt(s->fd, IPPROTO_TCP, TCP_MD5SIG, &enable, sizeof(enable)) < 0)
   {
     if (errno == ENOPROTOOPT)
diff --git a/sysdep/linux/sysio.h b/sysdep/linux/sysio.h
index c1561cbf..58644417 100644
--- a/sysdep/linux/sysio.h
+++ b/sysdep/linux/sysio.h
@@ -179,19 +179,19 @@ sk_prepare_cmsgs4(sock *s, struct msghdr *msg, void *cbuf, size_t cbuflen)
  */
 
 int
-sk_set_md5_auth(sock *s, ip_addr a, struct iface *ifa, char *passwd)
+sk_set_md5_auth(sock *s, ip_addr local UNUSED, ip_addr remote, struct iface *ifa, char *passwd, int setkey UNUSED)
 {
   struct tcp_md5sig md5;
 
   memset(&md5, 0, sizeof(md5));
-  sockaddr_fill((sockaddr *) &md5.tcpm_addr, s->af, a, ifa, 0);
+  sockaddr_fill((sockaddr *) &md5.tcpm_addr, s->af, remote, ifa, 0);
 
   if (passwd)
   {
     int len = strlen(passwd);
 
     if (len > TCP_MD5SIG_MAXKEYLEN)
-      ERR_MSG("MD5 password too long");
+      ERR_MSG("The password for TCP MD5 Signature is too long");
 
     md5.tcpm_keylen = len;
     memcpy(&md5.tcpm_key, passwd, len);
diff --git a/sysdep/unix/io.c b/sysdep/unix/io.c
index 5955dbfe..d918d321 100644
--- a/sysdep/unix/io.c
+++ b/sysdep/unix/io.c
@@ -951,23 +951,32 @@ sk_set_min_ttl(sock *s, int ttl)
 /**
  * sk_set_md5_auth - add / remove MD5 security association for given socket
  * @s: socket
- * @a: IP address of the other side
+ * @local: IP address of local side
+ * @remote: IP address of remote side
  * @ifa: Interface for link-local IP address
- * @passwd: password used for MD5 authentication
+ * @passwd: Password used for MD5 authentication
+ * @setkey: Update also system SA/SP database
  *
- * In TCP MD5 handling code in kernel, there is a set of pairs (address,
- * password) used to choose password according to address of the other side.
- * This function is useful for listening socket, for active sockets it is enough
- * to set s->password field.
+ * In TCP MD5 handling code in kernel, there is a set of security associations
+ * used for choosing password and other authentication parameters according to
+ * the local and remote address. This function is useful for listening socket,
+ * for active sockets it may be enough to set s->password field.
  *
  * When called with passwd != NULL, the new pair is added,
  * When called with passwd == NULL, the existing pair is removed.
  *
+ * Note that while in Linux, the MD5 SAs are specific to socket, in BSD they are
+ * stored in global SA/SP database (but the behavior also must be enabled on
+ * per-socket basis). In case of multiple sockets to the same neighbor, the
+ * socket-specific state must be configured for each socket while global state
+ * just once per src-dst pair. The @setkey argument controls whether the global
+ * state (SA/SP database) is also updated.
+ *
  * Result: 0 for success, -1 for an error.
  */
 
 int
-sk_set_md5_auth(sock *s, ip_addr a, struct iface *ifa, char *passwd)
+sk_set_md5_auth(sock *s, ip_addr local, ip_addr remote, struct iface *ifa, char *passwd, int setkey)
 { DUMMY; }
 #endif
 
@@ -1437,7 +1446,7 @@ sk_open(sock *s)
   }
 
   if (s->password)
-    if (sk_set_md5_auth(s, s->daddr, s->iface, s->password) < 0)
+    if (sk_set_md5_auth(s, s->saddr, s->daddr, s->iface, s->password, 0) < 0)
       goto err;
 
   switch (s->type)