add file encryption utils for AES-128-ECB

1 files changed, 79 insertions, 0 deletions

diff --git a/src/file.c b/src/file.c
new file mode 100644
index 0000000..445d917
--- /dev/null
+++ b/src/file.c
@@ -0,0 +1,79 @@
+/**
+ * \file
+ * \author Egor Tensin <Egor.Tensin@gmail.com>
+ * \date 2015
+ * \copyright This file is licensed under the terms of the MIT License.
+ *            See LICENSE.txt for details.
+ */
+
+#include <aesni/all.h>
+
+#include <stdlib.h>
+#include <string.h>
+
+size_t aes128ecb_encrypt_file(const unsigned char* src,
+                              size_t src_size,
+                              unsigned char* dest,
+                              Aes128KeySchedule* key_schedule)
+{
+    size_t rem_size = src_size % 16;
+    size_t padding_size = 16 - rem_size;
+    size_t dest_size = src_size + padding_size;
+
+    if (dest == NULL)
+        return dest_size;
+
+    size_t src_len = src_size / 16;
+
+    for (size_t i = 0; i < src_len; ++i, src += 16, dest += 16)
+    {
+        AesBlock128 plaintext = load_aes_block128(src);
+        AesBlock128 ciphertext = aes128ecb_encrypt(plaintext, key_schedule);
+        store_aes_block128(ciphertext, dest);
+    }
+
+    unsigned char padding[16] = { 0x10 };
+
+    if (rem_size != 0)
+    {
+        memcpy(padding, src, rem_size);
+        memset(padding + rem_size, padding_size, padding_size);
+    }
+
+    AesBlock128 plaintext = load_aes_block128(padding);
+    AesBlock128 ciphertext = aes128ecb_encrypt(plaintext, key_schedule);
+    store_aes_block128(ciphertext, dest);
+
+    return dest_size;
+}
+
+size_t aes128ecb_decrypt_file(const unsigned char* src,
+                              size_t src_size,
+                              unsigned char* dest,
+                              Aes128KeySchedule* inverted_schedule)
+{
+    size_t dest_size = src_size;
+
+    if (dest == NULL)
+        return dest_size;
+
+    size_t src_len = src_size / 16;
+
+    for (size_t i = 0; i < src_len - 1; ++i, src += 16, dest += 16)
+    {
+        AesBlock128 ciphertext = load_aes_block128(src);
+        AesBlock128 plaintext = aes128ecb_decrypt(ciphertext, inverted_schedule);
+        store_aes_block128(plaintext, dest);
+    }
+
+    AesBlock128 ciphertext = load_aes_block128(src);
+    AesBlock128 plaintext = aes128ecb_decrypt(ciphertext, inverted_schedule);
+    unsigned char padding[16];
+    store_aes_block128(plaintext, padding);
+
+    if (padding[0] == 0x10)
+        return dest_size - 16;
+
+    memcpy(dest, padding, 16 - padding[15]);
+    return dest_size - padding[15];
+}