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.

5 files changed, 203 insertions, 27 deletions

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)