Add point ctrls to X25519

Add ctrl operations to set or retrieve encoded point in
EVP_PKEY structures containing X25519 keys.

Reviewed-by: Rich Salz <rsalz@openssl.org>

crypto/evp/p_lib.c

diff --git a/crypto/evp/p_lib.c b/crypto/evp/p_lib.c
index 802f6dd..5b776ff 100644
--- a/crypto/evp/p_lib.c
+++ b/crypto/evp/p_lib.c
@@ -451,10 +451,34 @@
     return unsup_alg(out, pkey, indent, "Parameters");
 }
 
+static int evp_pkey_asn1_ctrl(EVP_PKEY *pkey, int op, int arg1, void *arg2)
+{
+    if (pkey->ameth == NULL || pkey->ameth->pkey_ctrl == NULL)
+        return -2;
+    return pkey->ameth->pkey_ctrl(pkey, op, arg1, arg2);
+}
+
 int EVP_PKEY_get_default_digest_nid(EVP_PKEY *pkey, int *pnid)
 {
-    if (!pkey->ameth || !pkey->ameth->pkey_ctrl)
-        return -2;
-    return pkey->ameth->pkey_ctrl(pkey, ASN1_PKEY_CTRL_DEFAULT_MD_NID,
-                                  0, pnid);
+    return evp_pkey_asn1_ctrl(pkey, ASN1_PKEY_CTRL_DEFAULT_MD_NID, 0, pnid);
+}
+
+int EVP_PKEY_set1_tls_encodedpoint(EVP_PKEY *pkey,
+                               const unsigned char *pt, size_t ptlen)
+{
+    if (ptlen > INT_MAX)
+        return 0;
+    if (evp_pkey_asn1_ctrl(pkey, ASN1_PKEY_CTRL_SET1_TLS_ENCPT, ptlen,
+                           (void *)pt) <= 0)
+        return 0;
+    return 1;
+}
+
+size_t EVP_PKEY_get1_tls_encodedpoint(EVP_PKEY *pkey, unsigned char **ppt)
+{
+    int rv;
+    rv = evp_pkey_asn1_ctrl(pkey, ASN1_PKEY_CTRL_GET1_TLS_ENCPT, 0, ppt);
+    if (rv <= 0)
+        return 0;
+    return rv;
 }