Improve ristretto255 scalarmult exception messages

These fail due to bad inputs, not internal errors.

Author: nikic

ext/sodium/libsodium.c

@@ -2585,7 +2585,7 @@ PHP_FUNCTION(sodium_crypto_scalarmult_ristretto255)
 	q = zend_string_alloc(crypto_scalarmult_ristretto255_BYTES, 0);
 	if (crypto_scalarmult_ristretto255((unsigned char *) ZSTR_VAL(q), n, p) != 0) {
 		zend_string_efree(q);
-		zend_throw_exception(sodium_exception_ce, "internal error", 0);
+		zend_throw_exception(sodium_exception_ce, "Result is identity element", 0);
 		RETURN_THROWS();
 	}
 	ZSTR_VAL(q)[crypto_scalarmult_ristretto255_BYTES] = 0;
@@ -2612,7 +2612,7 @@ PHP_FUNCTION(sodium_crypto_scalarmult_ristretto255_base)
 	q = zend_string_alloc(crypto_scalarmult_ristretto255_BYTES, 0);
 	if (crypto_scalarmult_ristretto255_base((unsigned char *) ZSTR_VAL(q), n) != 0) {
 		zend_string_efree(q);
-		zend_throw_exception(sodium_exception_ce, "internal error", 0);
+		zend_argument_error(sodium_exception_ce, 1, "must not be zero", 0);
 		RETURN_THROWS();
 	}
 	ZSTR_VAL(q)[crypto_scalarmult_BYTES] = 0;

ext/sodium/tests/crypto_core_ristretto255.phpt

@@ -128,7 +128,7 @@ bool(false)
 bool(false)
 string(64) "3066f82a1a747d45120d1740f14358531a8f04bbffe6a819f86dfe50f44a0a46"
 bool(true)
-internal error
+Result is identity element
 bool(true)
 bool(false)
 bool(true)

ext/sodium/tests/crypto_scalarmult_ristretto255.phpt

@@ -10,14 +10,22 @@ if (!defined('SODIUM_CRYPTO_CORE_RISTRETTO255_HASHBYTES')) print "skip libsodium
 <?php
 $b = sodium_hex2bin("e2f2ae0a6abc4e71a884a961c500515f58e30b6aa582dd8db6a65945e08d2d76");
 $n = str_repeat("\0", SODIUM_CRYPTO_SCALARMULT_RISTRETTO255_SCALARBYTES);
-for ($i = 0; $i < 16; $i++, sodium_increment($n)) {
-    try {
-        $p = sodium_crypto_scalarmult_ristretto255_base($n);
-        $p2 = sodium_crypto_scalarmult_ristretto255($n, $b);
-    } catch (SodiumException $ex) {
-        echo $ex->getMessage(), "\n";
-        continue;
-    }
+
+try {
+    $p = sodium_crypto_scalarmult_ristretto255_base($n);
+} catch (SodiumException $ex) {
+    echo $ex->getMessage(), "\n";
+}
+try {
+    $p2 = sodium_crypto_scalarmult_ristretto255($n, $b);
+} catch (SodiumException $ex) {
+    echo $ex->getMessage(), "\n";
+}
+
+for ($i = 1; $i < 16; $i++) {
+    sodium_increment($n);
+    $p = sodium_crypto_scalarmult_ristretto255_base($n);
+    $p2 = sodium_crypto_scalarmult_ristretto255($n, $b);
     var_dump(sodium_bin2hex($p));
     assert($p === $p2);
 }
@@ -30,7 +38,8 @@ try {
 
 ?>
 --EXPECT--
-internal error
+sodium_crypto_scalarmult_ristretto255_base(): Argument #1 ($n) must not be zero
+Result is identity element
 string(64) "e2f2ae0a6abc4e71a884a961c500515f58e30b6aa582dd8db6a65945e08d2d76"
 string(64) "6a493210f7499cd17fecb510ae0cea23a110e8d5b901f8acadd3095c73a3b919"
 string(64) "94741f5d5d52755ece4f23f044ee27d5d1ea1e2bd196b462166b16152a9d0259"