add error codes & messages to the library

2 files changed, 125 insertions, 17 deletions

diff --git a/src/buffer.c b/src/buffer.c
index b4896f7..71ebad2 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -13,20 +13,40 @@
 
 static unsigned char FULL_BLOCK_PADDING[16] = { 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16 };
 
-size_t aesni_encrypt_buffer_ecb128(
+int aesni_encrypt_buffer_ecb128(
     const void* src,
     size_t src_size,
     void* dest,
-    AesNI_KeySchedule128* key_schedule)
+    size_t* dest_size,
+    AesNI_KeySchedule128* key_schedule,
+    AesNI_ErrorDetails* err_details)
 {
-    size_t rem_size = src_size % 16;
-    size_t padding_size = 16 - rem_size;
-    size_t dest_size = src_size + padding_size;
+    if (dest_size == NULL)
+    {
+        aesni_make_error_null_argument(err_details, "dest_size");
+        return 1;
+    }
+
+    const size_t rem_size = src_size % 16;
+    const size_t padding_size = 16 - rem_size;
+    *dest_size = src_size + padding_size;
 
     if (dest == NULL)
-        return dest_size;
+        return 0;
 
-    size_t src_len = src_size / 16;
+    if (src == NULL)
+    {
+        aesni_make_error_null_argument(err_details, "src");
+        return 1;
+    }
+
+    if (key_schedule == NULL)
+    {
+        aesni_make_error_null_argument(err_details, "key_schedule");
+        return 1;
+    }
+
+    const size_t src_len = src_size / 16;
 
     for (size_t i = 0; i < src_len; ++i, (char*) src += 16, (char*) dest += 16)
     {
@@ -51,10 +71,10 @@ size_t aesni_encrypt_buffer_ecb128(
     AesNI_Block128 ciphertext = aesni_encrypt_block_ecb128(plaintext, key_schedule);
     aesni_store_block128(dest, ciphertext);
 
-    return dest_size;
+    return 0;
 }
 
-static unsigned char get_padding_size(const unsigned char* padding)
+static unsigned char get_pkcs7_padding_size(const unsigned char* padding)
 {
     if (padding[15] < 0x01 || padding[15] > 0x10)
         return 0;
@@ -66,18 +86,38 @@ static unsigned char get_padding_size(const unsigned char* padding)
     return padding[15];
 }
 
-size_t aesni_decrypt_buffer_ecb128(
+int aesni_decrypt_buffer_ecb128(
     const void* src,
     size_t src_size,
     void* dest,
-    AesNI_KeySchedule128* inverted_schedule)
+    size_t* dest_size,
+    AesNI_KeySchedule128* inverted_schedule,
+    AesNI_ErrorDetails* err_details)
 {
-    size_t dest_size = src_size;
+    if (dest_size == NULL)
+    {
+        aesni_make_error_null_argument(err_details, "dest_size");
+        return 1;
+    }
+
+    *dest_size = src_size;
 
     if (dest == NULL)
-        return dest_size;
+        return 0;
+
+    if (src == NULL)
+    {
+        aesni_make_error_null_argument(err_details, "src");
+        return 1;
+    }
 
-    size_t src_len = src_size / 16;
+    if (inverted_schedule == NULL)
+    {
+        aesni_make_error_null_argument(err_details, "inverted_schedule");
+        return 1;
+    }
+
+    const size_t src_len = src_size / 16;
 
     for (size_t i = 0; i < src_len - 1; ++i, (char*) src += 16, (char*) dest += 16)
     {
@@ -91,15 +131,17 @@ size_t aesni_decrypt_buffer_ecb128(
     unsigned char padding[16];
     aesni_store_block128(padding, plaintext);
 
-    unsigned char padding_size = get_padding_size(padding);
+    unsigned char padding_size = get_pkcs7_padding_size(padding);
 
     if (padding_size == 0)
     {
-        return dest_size - 16;
+        aesni_make_error_invalid_pkcs7_padding(err_details);
+        return 1;
     }
     else
     {
         memcpy(dest, padding, 16 - padding_size);
-        return dest_size - padding_size;
+        *dest_size -= padding_size;
+        return 0;
     }
 }
diff --git a/src/error.c b/src/error.c
new file mode 100644
index 0000000..c4af82c
--- /dev/null
+++ b/src/error.c
@@ -0,0 +1,66 @@
+/**
+ * \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>
+
+static const char* err_msgs[] =
+{
+    "Success",
+    "Invalid argument value NULL",
+    "Invalid PKCS7 padding (wrong key?)",
+};
+
+const char* aesni_strerror(AesNI_ErrorCode ec)
+{
+    return err_msgs[ec];
+}
+
+static void aesni_make_error(
+    AesNI_ErrorDetails* err_details,
+    AesNI_ErrorCode ec)
+{
+    if (err_details == NULL)
+        return;
+
+    err_details->ec = ec;
+}
+
+void aesni_make_error_success(
+    AesNI_ErrorDetails* err_details)
+{
+    if (err_details == NULL)
+        return;
+
+    aesni_make_error(err_details, AESNI_ERROR_SUCCESS);
+}
+
+void aesni_make_error_null_argument(
+    AesNI_ErrorDetails* err_details,
+    const char* arg_name)
+{
+    if (err_details == NULL)
+        return;
+
+    aesni_make_error(err_details, AESNI_ERROR_NULL_ARGUMENT);
+
+    const size_t arg_name_size = sizeof(err_details->params.null_arg.arg_name);
+    strncpy(err_details->params.null_arg.arg_name, arg_name, arg_name_size);
+    err_details->params.null_arg.arg_name[arg_name_size - 1] = '\0';
+}
+
+void aesni_make_error_invalid_pkcs7_padding(
+    AesNI_ErrorDetails* err_details)
+{
+    if (err_details == NULL)
+        return;
+
+    aesni_make_error(err_details, AESNI_ERROR_INVALID_PKCS7_PADDING);
+}