Fix memory leaks in ext/sodium on failure of some functions

Infallible in practice right now, but should be fixed as infallible today does not mean infallible tomorrow:
- sodium_crypto_sign_publickey_from_secretkey
- sodium_crypto_kx_seed_keypair
- sodium_crypto_kx_keypair
- sodium_crypto_auth
- sodium_crypto_sign_ed25519_sk_to_curve25519
- sodium_pad

Fallible today:
- sodium_crypto_sign_ed25519_pk_to_curve25519

Author: nielsdos

ext/sodium/libsodium.c

@@ -992,6 +992,7 @@ PHP_FUNCTION(sodium_crypto_sign_publickey_from_secretkey)
 
 	if (crypto_sign_ed25519_sk_to_pk((unsigned char *) ZSTR_VAL(publickey),
 									 (const unsigned char *) secretkey) != 0) {
+		zend_string_efree(publickey);
 		zend_throw_exception(sodium_exception_ce,
 				   "internal error", 0);
 		RETURN_THROWS();
@@ -2475,6 +2476,7 @@ PHP_FUNCTION(sodium_crypto_kx_seed_keypair)
 	crypto_generichash(sk, crypto_kx_SECRETKEYBYTES,
 					   seed, crypto_kx_SEEDBYTES, NULL, 0);
 	if (crypto_scalarmult_base(pk, sk) != 0) {
+		zend_string_efree(keypair);
 		zend_throw_exception(sodium_exception_ce, "internal error", 0);
 		RETURN_THROWS();
 	}
@@ -2496,6 +2498,7 @@ PHP_FUNCTION(sodium_crypto_kx_keypair)
 	pk = sk + crypto_kx_SECRETKEYBYTES;
 	randombytes_buf(sk, crypto_kx_SECRETKEYBYTES);
 	if (crypto_scalarmult_base(pk, sk) != 0) {
+		zend_string_efree(keypair);
 		zend_throw_exception(sodium_exception_ce, "internal error", 0);
 		RETURN_THROWS();
 	}
@@ -2672,6 +2675,7 @@ PHP_FUNCTION(sodium_crypto_auth)
 	if (crypto_auth((unsigned char *) ZSTR_VAL(mac),
 					(const unsigned char *) msg, msg_len,
 					(const unsigned char *) key) != 0) {
+		zend_string_efree(mac);
 		zend_throw_exception(sodium_exception_ce, "internal error", 0);
 		RETURN_THROWS();
 	}
@@ -2731,6 +2735,7 @@ PHP_FUNCTION(sodium_crypto_sign_ed25519_sk_to_curve25519)
 
 	if (crypto_sign_ed25519_sk_to_curve25519((unsigned char *) ZSTR_VAL(ecdhkey),
 											 (const unsigned char *) eddsakey) != 0) {
+		zend_string_efree(ecdhkey);
 		zend_throw_exception(sodium_exception_ce, "conversion failed", 0);
 		RETURN_THROWS();
 	}
@@ -2758,6 +2763,7 @@ PHP_FUNCTION(sodium_crypto_sign_ed25519_pk_to_curve25519)
 
 	if (crypto_sign_ed25519_pk_to_curve25519((unsigned char *) ZSTR_VAL(ecdhkey),
 											 (const unsigned char *) eddsakey) != 0) {
+		zend_string_efree(ecdhkey);
 		zend_throw_exception(sodium_exception_ce, "conversion failed", 0);
 		RETURN_THROWS();
 	}
@@ -3036,6 +3042,7 @@ PHP_FUNCTION(sodium_pad)
 #if SODIUM_LIBRARY_VERSION_MAJOR > 9 || (SODIUM_LIBRARY_VERSION_MAJOR == 9 && SODIUM_LIBRARY_VERSION_MINOR >= 6)
 	if (sodium_pad(NULL, (unsigned char *) ZSTR_VAL(padded), unpadded_len,
 				   (size_t) blocksize, xpadded_len + 1U) != 0) {
+		zend_string_efree(padded);
 		zend_throw_exception(sodium_exception_ce, "internal error", 0);
 		RETURN_THROWS();
 	}

ext/sodium/tests/sodium_crypto_sign_ed25519_pk_to_curve25519_failure_leak.phpt

@@ -0,0 +1,15 @@
+--TEST--
+Memory leak on sodium_crypto_sign_ed25519_pk_to_curve25519() failure
+--EXTENSIONS--
+sodium
+--FILE--
+<?php
+
+try {
+    sodium_crypto_sign_ed25519_pk_to_curve25519(str_repeat("\x00", SODIUM_CRYPTO_SIGN_PUBLICKEYBYTES));
+} catch (SodiumException $e) {
+    echo $e->getMessage();
+}
+
+?>
+--EXPECT--