- OpenBSD CVS updates:

[openssh.git] / kex.c

diff --git a/kex.c b/kex.c
index 0e5f257660e36fd1e334c250c26e7ceaa9d8134b..3082b73f2488f5110918230a54110646867f54d1 100644 (file)
--- a/kex.c
+++ b/kex.c
@@ -43,8 +43,6 @@ RCSID("$Id$");
 # include <openssl/dh.h>
 # include <openssl/crypto.h>
 # include <openssl/bio.h>
-# include <openssl/bn.h>
-# include <openssl/dh.h>
 # include <openssl/pem.h>
 #endif /* HAVE_OPENSSL */
 #if HAVE_SSL
@@ -52,12 +50,9 @@ RCSID("$Id$");
 # include <ssl/dh.h>
 # include <ssl/crypto.h>
 # include <ssl/bio.h>
-# include <ssl/bn.h>
-# include <ssl/dh.h>
 # include <ssl/pem.h>
 #endif /* HAVE_SSL */
 
-#include "entropy.h"
 #include "kex.h"
 
 Buffer *
@@ -85,8 +80,36 @@ kex_init(char *myproposal[PROPOSAL_MAX])
 
 /* diffie-hellman-group1-sha1 */
 
+int
+dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
+{
+       int i;
+       int n = BN_num_bits(dh_pub);
+       int bits_set = 0;
+
+       /* we only accept g==2 */
+       if (!BN_is_word(dh->g, 2)) {
+               log("invalid DH base != 2");
+               return 0;
+       }
+       if (dh_pub->neg) {
+               log("invalid public DH value: negativ");
+               return 0;
+       }
+       for (i = 0; i <= n; i++)
+               if (BN_is_bit_set(dh_pub, i))
+                       bits_set++;
+       debug("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
+
+       /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
+       if (bits_set > 1 && (BN_cmp(dh_pub, dh->p) == -1))
+               return 1;
+       log("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
+       return 0;
+}
+
 DH *
-new_dh_group1()
+dh_new_group1()
 {
        static char *group1 =
            "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
@@ -96,22 +119,23 @@ new_dh_group1()
            "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
            "FFFFFFFF" "FFFFFFFF";
        DH *dh;
-       int ret;
+       int ret, tries = 0;
        dh = DH_new();
        if(dh == NULL)
                fatal("DH_new");
-       ret = BN_hex2bn(&dh->p,group1);
+       ret = BN_hex2bn(&dh->p, group1);
        if(ret<0)
                fatal("BN_hex2bn");
        dh->g = BN_new();
        if(dh->g == NULL)
                fatal("DH_new g");
-       BN_set_word(dh->g,2);
-
-       seed_rng();
-       if (DH_generate_key(dh) == 0)
-               fatal("DH_generate_key");
-
+       BN_set_word(dh->g, 2);
+       do {
+               if (DH_generate_key(dh) == 0)
+                       fatal("DH_generate_key");
+               if (tries++ > 10)
+                       fatal("dh_new_group1: too many bad keys: giving up");
+       } while (!dh_pub_is_valid(dh, dh->pub_key));
        return dh;
 }
 
@@ -356,7 +380,7 @@ kex_choose_conf(char *cprop[PROPOSAL_MAX], char *sprop[PROPOSAL_MAX], int server
                choose_enc (&k->enc [mode], cprop[nenc],  sprop[nenc]);
                choose_mac (&k->mac [mode], cprop[nmac],  sprop[nmac]);
                choose_comp(&k->comp[mode], cprop[ncomp], sprop[ncomp]);
-               log("kex: %s %s %s %s",
+               debug("kex: %s %s %s %s",
                    ctos ? "client->server" : "server->client",
                    k->enc[mode].name,
                    k->mac[mode].name,