Split up GCM into a start/update/finish cycle
diff --git a/include/polarssl/gcm.h b/include/polarssl/gcm.h
index 77baa17..c703f3b 100644
--- a/include/polarssl/gcm.h
+++ b/include/polarssl/gcm.h
@@ -49,6 +49,12 @@
aes_context aes_ctx; /*!< AES context used */
uint64_t HL[16]; /*!< Precalculated HTable */
uint64_t HH[16]; /*!< Precalculated HTable */
+ uint64_t len; /*!< Total data length */
+ uint64_t add_len; /*!< Total add length */
+ unsigned char base_ectr[16];/*!< First ECTR for tag */
+ unsigned char y[16]; /*!< Y working value */
+ unsigned char buf[16]; /*!< buf working value */
+ int mode; /*!< Encrypt or Decrypt */
}
gcm_context;
@@ -115,7 +121,7 @@
* \param add additional data
* \param add_len length of additional data
* \param tag buffer holding the tag
- * \param tag_len length of the tag
+ * \param tag_len length of the tag
* \param input buffer holding the input data
* \param output buffer for holding the output data
*
@@ -128,12 +134,68 @@
size_t iv_len,
const unsigned char *add,
size_t add_len,
- const unsigned char *tag,
+ const unsigned char *tag,
size_t tag_len,
const unsigned char *input,
unsigned char *output );
/**
+ * \brief Generic GCM stream start function
+ *
+ * \param ctx GCM context
+ * \param mode GCM_ENCRYPT or GCM_DECRYPT
+ * \param iv initialization vector
+ * \param iv_len length of IV
+ * \param add additional data
+ * \param add_len length of additional data
+ *
+ * \return 0 if successful
+ */
+int gcm_starts( gcm_context *ctx,
+ int mode,
+ const unsigned char *iv,
+ size_t iv_len,
+ const unsigned char *add,
+ size_t add_len );
+
+/**
+ * \brief Generic GCM update function. Encrypts/decrypts using the
+ * given GCM context. Expects input to be a multiple of 16
+ * bytes! Only the last call before gcm_finish() can be less
+ * than 16 bytes!
+ *
+ * \note On decryption, the output buffer cannot be the same as input buffer.
+ * If buffers overlap, the output buffer must trail at least 8 bytes
+ * behind the input buffer.
+ *
+ * \param ctx GCM context
+ * \param length length of the input data
+ * \param input buffer holding the input data
+ * \param output buffer for holding the output data
+ *
+ * \return 0 if successful or POLARSSL_ERR_GCM_BAD_INPUT
+ */
+int gcm_update( gcm_context *ctx,
+ size_t length,
+ const unsigned char *input,
+ unsigned char *output );
+
+/**
+ * \brief Generic GCM finalisation function. Wraps up the GCM stream
+ * and generated the tag. The tag can have a maximum length of
+ * 16 bytes.
+ *
+ * \param ctx GCM context
+ * \param tag buffer for holding the tag
+ * \param tag_len length of the tag to generate
+ *
+ * \return 0 if successful or POLARSSL_ERR_GCM_BAD_INPUT
+ */
+int gcm_finish( gcm_context *ctx,
+ unsigned char *tag,
+ size_t tag_len );
+
+/**
* \brief Checkup routine
*
* \return 0 if successful, or 1 if the test failed