Clear secret stack values after use in curve25519.c

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4242)

(cherry picked from commit 78f1e4d0b063e17c9700f2aceecaca03bfa434f3)

diff --git a/crypto/ec/curve25519.c b/crypto/ec/curve25519.c
index e535823c0f75ef52412341eb9bf35fd9d5256eff..c8aa9aa6d503ba0c2b1219c2d04ac3759cb7d329 100644 (file)
--- a/crypto/ec/curve25519.c
+++ b/crypto/ec/curve25519.c
@@ -3226,6 +3226,8 @@ static void ge_scalarmult_base(ge_p3 *h, const uint8_t *a) {
     ge_madd(&r, h, &t);
     ge_p1p1_to_p3(h, &r);
   }
+
+  OPENSSL_cleanse(e, sizeof(e));
 }
 
 /* Replace (f,g) with (g,f) if b == 1;
@@ -3356,6 +3358,8 @@ static void x25519_scalar_mult_generic(uint8_t out[32],
   fe_invert(z2, z2);
   fe_mul(x2, x2, z2);
   fe_tobytes(out, x2);
+
+  OPENSSL_cleanse(e, sizeof(e));
 }
 
 static void x25519_scalar_mult(uint8_t out[32], const uint8_t scalar[32],
@@ -3391,4 +3395,6 @@ void X25519_public_from_private(uint8_t out_public_value[32],
   fe_invert(zminusy_inv, zminusy);
   fe_mul(zplusy, zplusy, zminusy_inv);
   fe_tobytes(out_public_value, zplusy);
+
+  OPENSSL_cleanse(e, sizeof(e));
 }