3 files changed, 18 insertions, 8 deletions

diff --git a/ChangeLog b/ChangeLog
index 6152abb51..5eb73c9f9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -21,6 +21,12 @@
      [sshconnect.c]
      bz#1211: make BindAddress work with UsePrivilegedPort=yes; patch from
      swp AT swp.pp.ru; ok dtucker@
+   - dtucker@cvs.openbsd.org 2013/10/08 11:42:13
+     [dh.c dh.h]
+     Increase the size of the Diffie-Hellman groups requested for a each
+     symmetric key size.  New values from NIST Special Publication 800-57 with
+     the upper limit specified by RFC4419.  Pointed out by Peter Backes, ok
+     djm@.
 
 20131009
  - (djm) [openbsd-compat/arc4random.c openbsd-compat/chacha_private.h] Pull
diff --git a/dh.c b/dh.c
index 449dd3858..d33af1fa7 100644
--- a/dh.c
+++ b/dh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: dh.c,v 1.51 2013/07/02 12:31:43 markus Exp $ */
+/* $OpenBSD: dh.c,v 1.52 2013/10/08 11:42:13 dtucker Exp $ */
 /*
  * Copyright (c) 2000 Niels Provos.  All rights reserved.
  *
@@ -352,17 +352,20 @@ dh_new_group14(void)
 
 /*
  * Estimates the group order for a Diffie-Hellman group that has an
- * attack complexity approximately the same as O(2**bits).  Estimate
- * with:  O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3)))
+ * attack complexity approximately the same as O(2**bits).
+ * Values from NIST Special Publication 800-57: Recommendation for Key
+ * Management Part 1 (rev 3) limited by the recommended maximum value
+ * from RFC4419 section 3.
  */
 
 int
 dh_estimate(int bits)
 {
-
+        if (bits <= 112)
+                return 2048;
         if (bits <= 128)
-                return (1024);  /* O(2**86) */
+                return 3072;
         if (bits <= 192)
-                return (2048);  /* O(2**116) */
-        return (4096);          /* O(2**156) */
+                return 7680;
+        return 8192;
 }
diff --git a/dh.h b/dh.h
index dfc1480ea..48f7b68ea 100644
--- a/dh.h
+++ b/dh.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: dh.h,v 1.10 2008/06/26 09:19:40 djm Exp $ */
+/* $OpenBSD: dh.h,v 1.11 2013/10/08 11:42:13 dtucker Exp $ */
 
 /*
  * Copyright (c) 2000 Niels Provos.  All rights reserved.
@@ -43,6 +43,7 @@ int	 dh_pub_is_valid(DH *, BIGNUM *);
 
 int      dh_estimate(int);
 
+/* Min and max values from RFC4419. */
 #define DH_GRP_MIN      1024
 #define DH_GRP_MAX      8192