From d51aa2819005a03e4cfb6f62333be6ccadfb3c06 Mon Sep 17 00:00:00 2001
From: Ondrej Zajicek <santiago@crfreenet.org>
Date: Sun, 26 Oct 2008 22:42:39 +0100
Subject: Implementation of MD5 authentication of BGP sessions.

---
 sysdep/linux/sysio.h | 21 +++++++++++++++
 sysdep/unix/io.c     | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 96 insertions(+)

(limited to 'sysdep')

diff --git a/sysdep/linux/sysio.h b/sysdep/linux/sysio.h
index 3a29cdc..b0aff71 100644
--- a/sysdep/linux/sysio.h
+++ b/sysdep/linux/sysio.h
@@ -139,3 +139,24 @@ static inline char *sysio_mcast_join(sock *s)
 #endif
 
 #endif
+
+#include <linux/socket.h>
+#include <linux/tcp.h>
+
+/* For the case that we have older kernel headers */
+/* Copied from Linux kernel file include/linux/tcp.h */
+
+#ifndef TCP_MD5SIG
+
+#define TCP_MD5SIG  14
+#define TCP_MD5SIG_MAXKEYLEN 80
+
+struct tcp_md5sig {
+  struct __kernel_sockaddr_storage tcpm_addr;     /* address associated */
+  __u16   __tcpm_pad1;                            /* zero */
+  __u16   tcpm_keylen;                            /* key length */
+  __u32   __tcpm_pad2;                            /* zero */
+  __u8    tcpm_key[TCP_MD5SIG_MAXKEYLEN];         /* key (binary) */
+};
+
+#endif
diff --git a/sysdep/unix/io.c b/sysdep/unix/io.c
index 7dcca21..6faa176 100644
--- a/sysdep/unix/io.c
+++ b/sysdep/unix/io.c
@@ -546,6 +546,7 @@ sk_new(pool *p)
   s->err_hook = NULL;
   s->fd = -1;
   s->rbuf_alloc = s->tbuf_alloc = NULL;
+  s->password = NULL;
   return s;
 }
 
@@ -642,6 +643,71 @@ bad:
   return err;
 }
 
+
+/* FIXME: check portability  */
+
+static int
+sk_set_md5_auth_int(sock *s, sockaddr *sa, char *passwd)
+{
+  struct tcp_md5sig md5;
+
+  memset(&md5, 0, sizeof(md5));
+  memcpy(&md5.tcpm_addr, (struct sockaddr *) sa, sizeof(*sa));
+
+  if (passwd)
+    {
+      int len = strlen(passwd);
+
+      if (len > TCP_MD5SIG_MAXKEYLEN)
+	{
+	  log(L_ERR "MD5 password too long");
+	  return -1;
+	}
+
+      md5.tcpm_keylen = len;
+      memcpy(&md5.tcpm_key, passwd, len);
+    }
+
+  int rv = setsockopt(s->fd, IPPROTO_TCP, TCP_MD5SIG, &md5, sizeof(md5));
+
+  if (rv < 0) 
+    {
+      if (errno == ENOPROTOOPT)
+	log(L_ERR "Kernel does not support TCP MD5 signatures");
+      else
+	log(L_ERR "sk_set_md5_auth_int: setsockopt: %m");
+    }
+
+  return rv;
+}
+
+/**
+ * sk_set_md5_auth - add / remove MD5 security association for given socket.
+ * @s: socket
+ * @a: IP address of the other side
+ * @passwd: password used for MD5 authentication
+ *
+ * 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.
+ *
+ * When called with passwd != NULL, the new pair is added,
+ * When called with passwd == NULL, the existing pair is removed.
+ *
+ * Result: 0 for success, -1 for an error.
+ */
+
+int
+sk_set_md5_auth(sock *s, ip_addr a, char *passwd)
+{
+  sockaddr sa;
+  fill_in_sockaddr(&sa, a, 0);
+  return sk_set_md5_auth_int(s, &sa, passwd);
+}
+
+
 static void
 sk_tcp_connected(sock *s)
 {
@@ -805,6 +871,14 @@ sk_open(sock *s)
 	ERR("bind");
     }
   fill_in_sockaddr(&sa, s->daddr, s->dport);
+
+  if (s->password)
+    {
+      int rv = sk_set_md5_auth_int(s, &sa, s->password);
+      if (rv < 0)
+	goto bad_no_log;
+    }
+
   switch (type)
     {
     case SK_TCP_ACTIVE:
@@ -846,6 +920,7 @@ sk_open(sock *s)
 
 bad:
   log(L_ERR "sk_open: %s: %m", err);
+bad_no_log:
   close(fd);
   s->fd = -1;
   return -1;
-- 
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