Constify EC_KEY_*_oct2priv() input buffer

Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1300)

crypto/ec/ec_25519.c

@@ -155,7 +155,7 @@ static int x25519_keycopy(EC_KEY *dest, const EC_KEY *src)
     return x25519_init_private(dest, src->custom_data);
 }
 
-static int x25519_oct2priv(EC_KEY *eckey, unsigned char *buf, size_t len)
+static int x25519_oct2priv(EC_KEY *eckey, const unsigned char *buf, size_t len)
 {
     if (len != EC_X25519_KEYLEN)
         return 0;

crypto/ec/ec_key.c

@@ -546,7 +546,8 @@ int EC_KEY_oct2key(EC_KEY *key, const unsigned char *buf, size_t len,
     return 1;
 }
 
-size_t EC_KEY_priv2oct(const EC_KEY *eckey, unsigned char *buf, size_t len)
+size_t EC_KEY_priv2oct(const EC_KEY *eckey, 
+                       unsigned char *buf, size_t len)
 {
     if (eckey->group == NULL || eckey->group->meth == NULL)
         return 0;
@@ -581,7 +582,7 @@ size_t ec_key_simple_priv2oct(const EC_KEY *eckey,
     return buf_len;
 }
 
-int EC_KEY_oct2priv(EC_KEY *eckey, unsigned char *buf, size_t len)
+int EC_KEY_oct2priv(EC_KEY *eckey, const unsigned char *buf, size_t len)
 {
     if (eckey->group == NULL || eckey->group->meth == NULL)
         return 0;
@@ -592,7 +593,7 @@ int EC_KEY_oct2priv(EC_KEY *eckey, unsigned char *buf, size_t len)
     return eckey->group->meth->oct2priv(eckey, buf, len);
 }
 
-int ec_key_simple_oct2priv(EC_KEY *eckey, unsigned char *buf, size_t len)
+int ec_key_simple_oct2priv(EC_KEY *eckey, const unsigned char *buf, size_t len)
 {
     if (eckey->priv_key == NULL)
         eckey->priv_key = BN_secure_new();

crypto/ec/ec_lcl.h

@@ -159,7 +159,7 @@ struct ec_method_st {
     int (*field_set_to_one) (const EC_GROUP *, BIGNUM *r, BN_CTX *);
     /* private key operations */
     size_t (*priv2oct)(const EC_KEY *eckey, unsigned char *buf, size_t len);
-    int (*oct2priv)(EC_KEY *eckey, unsigned char *buf, size_t len);
+    int (*oct2priv)(EC_KEY *eckey, const unsigned char *buf, size_t len);
     int (*set_private)(EC_KEY *eckey, const BIGNUM *priv_key);
     int (*keygen)(EC_KEY *eckey);
     int (*keycheck)(const EC_KEY *eckey);
@@ -553,7 +553,7 @@ const EC_METHOD *EC_GFp_nistz256_method(void);
 
 size_t ec_key_simple_priv2oct(const EC_KEY *eckey,
                               unsigned char *buf, size_t len);
-int ec_key_simple_oct2priv(EC_KEY *eckey, unsigned char *buf, size_t len);
+int ec_key_simple_oct2priv(EC_KEY *eckey, const unsigned char *buf, size_t len);
 int ec_key_simple_generate_key(EC_KEY *eckey);
 int ec_key_simple_generate_public_key(EC_KEY *eckey);
 int ec_key_simple_check_key(const EC_KEY *eckey);

doc/crypto/EC_KEY_new.pod

@@ -49,7 +49,7 @@ EC_KEY objects
  size_t EC_KEY_key2buf(const EC_KEY *eckey, point_conversion_form_t form,
                        unsigned char **pbuf, BN_CTX *ctx);
 
- int EC_KEY_oct2priv(EC_KEY *eckey, unsigned char *buf, size_t len);
+ int EC_KEY_oct2priv(EC_KEY *eckey, const unsigned char *buf, size_t len);
  size_t EC_KEY_priv2oct(const EC_KEY *eckey, unsigned char *buf, size_t len);
 
  size_t EC_KEY_priv2buf(const EC_KEY *eckey, unsigned char **pbuf);

include/openssl/ec.h

@@ -906,7 +906,7 @@ int EC_KEY_oct2key(EC_KEY *key, const unsigned char *buf, size_t len,
  *  \return 1 on success and 0 if an error occurred
  */
 
-int EC_KEY_oct2priv(EC_KEY *key, unsigned char *buf, size_t len);
+int EC_KEY_oct2priv(EC_KEY *key, const unsigned char *buf, size_t len);
 
 /** Encodes a EC_KEY private key to an octet string
  *  \param  key    key to encode