ikev2: fix wrong usage of BN_bn2bin()

This patch fixes 2 different crashes:

1) BN_bn2bin() returns bytes written, not actual key length. Use
  BN_bn2binpad() instead which adds padding.
2) Initiator may receive multiple sa-init responses for the same ispi
  which may result in crash. Remember first response and ignore any
  subsequent ones.

Type: fix

Change-Id: Ia1eac9167e3100a6894c0563ee70bab04f6a5f4f
Signed-off-by: Filip Tehlar <ftehlar@cisco.com>

1 files changed, 39 insertions, 8 deletions

diff --git a/src/plugins/ikev2/ikev2_crypto.c b/src/plugins/ikev2/ikev2_crypto.c
index 26ff43387e7..572bee8fc65 100644
--- a/src/plugins/ikev2/ikev2_crypto.c
+++ b/src/plugins/ikev2/ikev2_crypto.c
@@ -458,6 +458,23 @@ ikev2_encrypt_data (ikev2_sa_t * sa, v8 * src, u8 * dst)
   return out_len + bs;
 }
 
+#ifndef BN_bn2binpad
+int
+BN_bn2binpad (const BIGNUM * a, unsigned char *to, int tolen)
+{
+  int r = BN_bn2bin (a, to);
+  ASSERT (tolen >= r);
+  int pad = tolen - r;
+  if (pad)
+    {
+      vec_insert (to, pad, 0);
+      clib_memset (to, 0, pad);
+      _vec_len (to) -= pad;
+    }
+  return tolen;
+}
+#endif
+
 void
 ikev2_generate_dh (ikev2_sa_t * sa, ikev2_sa_transform_t * t)
 {
@@ -486,13 +503,13 @@ ikev2_generate_dh (ikev2_sa_t * sa, ikev2_sa_transform_t * t)
 	  sa->dh_private_key = vec_new (u8, t->key_len);
 #if OPENSSL_VERSION_NUMBER >= 0x10100000L
 	  DH_get0_key (dh, &pub_key, &priv_key);
-	  r = BN_bn2bin (pub_key, sa->i_dh_data);
+	  r = BN_bn2binpad (pub_key, sa->i_dh_data, t->key_len);
 	  ASSERT (r == t->key_len);
-	  r = BN_bn2bin (priv_key, sa->dh_private_key);
+	  r = BN_bn2binpad (priv_key, sa->dh_private_key, t->key_len);
 #else
-	  r = BN_bn2bin (dh->pub_key, sa->i_dh_data);
+	  r = BN_bn2binpad (dh->pub_key, sa->i_dh_data, t->key_len);
 	  ASSERT (r == t->key_len);
-	  r = BN_bn2bin (dh->priv_key, sa->dh_private_key);
+	  r = BN_bn2binpad (dh->priv_key, sa->dh_private_key, t->key_len);
 #endif
 	  ASSERT (r == t->key_len);
 	}
@@ -501,9 +518,9 @@ ikev2_generate_dh (ikev2_sa_t * sa, ikev2_sa_transform_t * t)
 	  sa->r_dh_data = vec_new (u8, t->key_len);
 #if OPENSSL_VERSION_NUMBER >= 0x10100000L
 	  DH_get0_key (dh, &pub_key, &priv_key);
-	  r = BN_bn2bin (pub_key, sa->r_dh_data);
+	  r = BN_bn2binpad (pub_key, sa->r_dh_data, t->key_len);
 #else
-	  r = BN_bn2bin (dh->pub_key, sa->r_dh_data);
+	  r = BN_bn2binpad (dh->pub_key, sa->r_dh_data, t->key_len);
 #endif
 	  ASSERT (r == t->key_len);
 
@@ -511,7 +528,14 @@ ikev2_generate_dh (ikev2_sa_t * sa, ikev2_sa_transform_t * t)
 	  sa->dh_shared_key = vec_new (u8, t->key_len);
 	  ex = BN_bin2bn (sa->i_dh_data, vec_len (sa->i_dh_data), NULL);
 	  r = DH_compute_key (sa->dh_shared_key, ex, dh);
-	  ASSERT (r == t->key_len);
+	  ASSERT (t->key_len >= r);
+	  int pad = t->key_len - r;
+	  if (pad)
+	    {
+	      vec_insert (sa->dh_shared_key, pad, 0);
+	      clib_memset (sa->dh_shared_key, 0, pad);
+	      _vec_len (sa->dh_shared_key) -= pad;
+	    }
 	  BN_clear_free (ex);
 	}
       DH_free (dh);
@@ -630,7 +654,14 @@ ikev2_complete_dh (ikev2_sa_t * sa, ikev2_sa_transform_t * t)
       sa->dh_shared_key = vec_new (u8, t->key_len);
       ex = BN_bin2bn (sa->r_dh_data, vec_len (sa->r_dh_data), NULL);
       r = DH_compute_key (sa->dh_shared_key, ex, dh);
-      ASSERT (r == t->key_len);
+      ASSERT (t->key_len >= r);
+      int pad = t->key_len - r;
+      if (pad)
+	{
+	  vec_insert (sa->dh_shared_key, pad, 0);
+	  clib_memset (sa->dh_shared_key, 0, pad);
+	  _vec_len (sa->dh_shared_key) -= pad;
+	}
       BN_clear_free (ex);
       DH_free (dh);
     }