diffie-hellman: Don't set exponent length for DH groups with prime order subgroups

According to RFC 5114 the exponent length for these groups should always equal
the size of their prime order subgroup.
This was handled correctly before the initialization was done during
library initialization.

Fixes: 46184b07c163 ("diffie-hellman: Explicitly initialize DH exponent sizes during initialization")

diff --git a/src/libstrongswan/crypto/diffie_hellman.c b/src/libstrongswan/crypto/diffie_hellman.c
index 820b8d1d8ffd2f1109a33a593bf87a0752a3af9a..8127340005230228883e3c3f6cd53cec9d482d10 100644 (file)
--- a/src/libstrongswan/crypto/diffie_hellman.c
+++ b/src/libstrongswan/crypto/diffie_hellman.c
@@ -449,6 +449,12 @@ void diffie_hellman_init()
        {
                for (i = 0; i < countof(dh_params); i++)
                {
+                       /* according to RFC 5114 the size of the exponent for these DH
+                        * groups should equal the size of their prime order subgroup */
+                       if (dh_params[i].public.subgroup.len)
+                       {
+                               continue;
+                       }
                        dh_params[i].public.exp_len = dh_params[i].public.prime.len;
                }
        }