Winzip AES encryption support for writing.
diff --git a/lib/zip_file_set_encryption.c b/lib/zip_file_set_encryption.c
new file mode 100644
index 0000000..9ef09f3
--- /dev/null
+++ b/lib/zip_file_set_encryption.c
@@ -0,0 +1,115 @@
+/*
+ zip_file_set_encryption.c -- set encryption for file in archive
+ Copyright (C) 2016 Dieter Baron and Thomas Klausner
+
+ This file is part of libzip, a library to manipulate ZIP archives.
+ The authors can be contacted at <libzip@nih.at>
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions
+ are met:
+ 1. Redistributions of source code must retain the above copyright
+ notice, this list of conditions and the following disclaimer.
+ 2. Redistributions in binary form must reproduce the above copyright
+ notice, this list of conditions and the following disclaimer in
+ the documentation and/or other materials provided with the
+ distribution.
+ 3. The names of the authors may not be used to endorse or promote
+ products derived from this software without specific prior
+ written permission.
+
+ THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS
+ OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
+ DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
+ GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
+ IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
+ IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+
+#include "zipint.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+ZIP_EXTERN int
+zip_file_set_encryption(zip_t *za, zip_uint64_t idx, zip_uint16_t method, const char *password)
+{
+ zip_entry_t *e;
+ zip_uint16_t old_method;
+
+ if (idx >= za->nentry) {
+ zip_error_set(&za->error, ZIP_ER_INVAL, 0);
+ return -1;
+ }
+
+ if (ZIP_IS_RDONLY(za)) {
+ zip_error_set(&za->error, ZIP_ER_RDONLY, 0);
+ return -1;
+ }
+
+ if (_zip_get_encryption_implementation(method, ZIP_CODEC_ENCODE) == NULL) {
+ zip_error_set(&za->error, ZIP_ER_COMPNOTSUPP, 0);
+ return -1;
+ }
+
+ e = za->entry+idx;
+
+ old_method = (e->orig == NULL ? ZIP_EM_NONE : e->orig->encryption_method);
+
+ if (method == old_method && password == NULL) {
+ if (e->changes) {
+ if (e->changes->changed & ZIP_DIRENT_PASSWORD) {
+ _zip_crypto_clear(e->changes->password, strlen(e->changes->password));
+ free(e->changes->password);
+ e->changes->password = e->orig->password;
+ }
+ e->changes->changed &= ~(ZIP_DIRENT_ENCRYPTION_METHOD|ZIP_DIRENT_PASSWORD);
+ if (e->changes->changed == 0) {
+ _zip_dirent_free(e->changes);
+ e->changes = NULL;
+ }
+ }
+ }
+ else {
+ char *our_password = NULL;
+
+ if (password) {
+ if ((our_password = strdup(password)) == NULL) {
+ zip_error_set(&za->error, ZIP_ER_MEMORY, 0);
+ return -1;
+ }
+ }
+
+ if (e->changes == NULL) {
+ if ((e->changes=_zip_dirent_clone(e->orig)) == NULL) {
+ _zip_crypto_clear(our_password, strlen(our_password));
+ free(our_password);
+ zip_error_set(&za->error, ZIP_ER_MEMORY, 0);
+ return -1;
+ }
+ }
+
+ e->changes->encryption_method = method;
+ e->changes->changed |= ZIP_DIRENT_ENCRYPTION_METHOD;
+ if (password) {
+ e->changes->password = our_password;
+ e->changes->changed |= ZIP_DIRENT_PASSWORD;
+ }
+ else {
+ if (e->changes->changed & ZIP_DIRENT_PASSWORD) {
+ _zip_crypto_clear(e->changes->password, strlen(e->changes->password));
+ free(e->changes->password);
+ e->changes->password = e->orig->password;
+ e->changes->changed &= ~ZIP_DIRENT_PASSWORD;
+ }
+ }
+ }
+
+ return 0;
+}
