Add crypto sources for future use.add/crypto

 * the goal is to support AES-CBC-HMAC-SHA as AEAD cipher

Signed-off-by: Toni Uhlig <matzeton@googlemail.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/crypto/pkcs7_padding.h b/crypto/pkcs7_padding.h
new file mode 100644
index 0000000..bdd6c21
--- /dev/null
+++ b/crypto/pkcs7_padding.h
@@ -0,0 +1,24 @@
+#ifndef _PKCS7_PADDING_H_
+#define _PKCS7_PADDING_H_
+
+#include <stdint.h>
+#include <stddef.h>
+
+/* Pad a buffer with bytes as defined in PKCS#7 
+ * Returns the number of pad bytes added, or zero if
+ * the buffer size is not large enough to hold the correctly padded data
+ */
+int pkcs7_padding_pad_buffer( uint8_t *buffer,  size_t data_length, size_t buffer_size, uint8_t modulus );
+
+int pkcs7_padding_valid( uint8_t *buffer, size_t data_length, size_t buffer_size, uint8_t modulus );
+
+/* Given a block of pkcs7 padded data, return the actual data length in the block based on the padding applied.
+ * buffer_size must be a multiple of modulus
+ * last byte 'x' in buffer must be between 1 and modulus
+ * buffer_size must be at least x + 1 in size
+ * last 'x' bytes in buffer must be same as 'x'
+ * returned size will be buffer_size - 'x'
+ */
+size_t pkcs7_padding_data_length( uint8_t * buffer, size_t buffer_size, uint8_t modulus );
+
+#endif
\ No newline at end of file