1 files changed, 24 insertions, 8 deletions

diff --git a/src/lib/libcrypto/dh/dh_gen.c b/src/lib/libcrypto/dh/dh_gen.c
index 7a6a38fbb4..06f78b35ab 100644
--- a/src/lib/libcrypto/dh/dh_gen.c
+++ b/src/lib/libcrypto/dh/dh_gen.c
@@ -82,7 +82,10 @@
  * Since DH should be using a safe prime (both p and q are prime),
  * this generator function can take a very very long time to run.
  */
-
+/* Actually there is no reason to insist that 'generator' be a generator.
+ * It's just as OK (and in some sense better) to use a generator of the
+ * order-q subgroup.
+ */
 DH *DH_generate_parameters(int prime_len, int generator,
              void (*callback)(int,int,void *), void *cb_arg)
         {
@@ -100,30 +103,43 @@ DH *DH_generate_parameters(int prime_len, int generator,
         t2 = BN_CTX_get(ctx);
         if (t1 == NULL || t2 == NULL) goto err;
         
+        if (generator <= 1)
+                {
+                DHerr(DH_F_DH_GENERATE_PARAMETERS, DH_R_BAD_GENERATOR);
+                goto err;
+                }
         if (generator == DH_GENERATOR_2)
                 {
-                BN_set_word(t1,24);
-                BN_set_word(t2,11);
+                if (!BN_set_word(t1,24)) goto err;
+                if (!BN_set_word(t2,11)) goto err;
                 g=2;
                 }
-#ifdef undef  /* does not work for safe primes */
+#if 0 /* does not work for safe primes */
         else if (generator == DH_GENERATOR_3)
                 {
-                BN_set_word(t1,12);
-                BN_set_word(t2,5);
+                if (!BN_set_word(t1,12)) goto err;
+                if (!BN_set_word(t2,5)) goto err;
                 g=3;
                 }
 #endif
         else if (generator == DH_GENERATOR_5)
                 {
-                BN_set_word(t1,10);
-                BN_set_word(t2,3);
+                if (!BN_set_word(t1,10)) goto err;
+                if (!BN_set_word(t2,3)) goto err;
                 /* BN_set_word(t3,7); just have to miss
                  * out on these ones :-( */
                 g=5;
                 }
         else
+                {
+                /* in the general case, don't worry if 'generator' is a
+                 * generator or not: since we are using safe primes,
+                 * it will generate either an order-q or an order-2q group,
+                 * which both is OK */
+                if (!BN_set_word(t1,2)) goto err;
+                if (!BN_set_word(t2,1)) goto err;
                 g=generator;
+                }
         
         p=BN_generate_prime(NULL,prime_len,1,t1,t2,callback,cb_arg);
         if (p == NULL) goto err;