Merge remote-tracking branch 'public/pr/1593' into development

include/mbedtls/aes.h

@@ -296,6 +296,56 @@ int mbedtls_aes_crypt_cfb8( mbedtls_aes_context *ctx,
                     unsigned char *output );
 #endif /*MBEDTLS_CIPHER_MODE_CFB */
 
+#if defined(MBEDTLS_CIPHER_MODE_OFB)
+/**
+ * \brief       This function performs an AES-OFB (Output Feedback Mode)
+ *              encryption or decryption operation.
+ *
+ *              For OFB, you must set up the context with
+ *              mbedtls_aes_setkey_enc(), regardless of whether you are
+ *              performing an encryption or decryption operation. This is
+ *              because OFB mode uses the same key schedule for encryption and
+ *              decryption.
+ *
+ *              The OFB operation is identical for encryption or decryption,
+ *              therefore no operation mode needs to be specified.
+ *
+ * \note        Upon exit, the content of iv, the Initialisation Vector, is
+ *              updated so that you can call the same function again on the next
+ *              block(s) of data and get the same result as if it was encrypted
+ *              in one call. This allows a "streaming" usage, by initialising
+ *              iv_off to 0 before the first call, and preserving its value
+ *              between calls.
+ *
+ *              For non-streaming use, the iv should be initialised on each call
+ *              to a unique value, and iv_off set to 0 on each call.
+ *
+ *              If you need to retain the contents of the initialisation vector,
+ *              you must either save it manually or use the cipher module
+ *              instead.
+ *
+ * \warning     For the OFB mode, the initialisation vector must be unique
+ *              every encryption operation. Reuse of an initialisation vector
+ *              will compromise security.
+ *
+ * \param ctx      The AES context to use for encryption or decryption.
+ * \param length   The length of the input data.
+ * \param iv_off   The offset in IV (updated after use).
+ * \param iv       The initialization vector (updated after use).
+ * \param input    The buffer holding the input data.
+ * \param output   The buffer holding the output data.
+ *
+ * \return         \c 0 on success.
+ */
+int mbedtls_aes_crypt_ofb( mbedtls_aes_context *ctx,
+                       size_t length,
+                       size_t *iv_off,
+                       unsigned char iv[16],
+                       const unsigned char *input,
+                       unsigned char *output );
+
+#endif /* MBEDTLS_CIPHER_MODE_OFB */
+
 #if defined(MBEDTLS_CIPHER_MODE_CTR)
 /**
  * \brief      This function performs an AES-CTR encryption or decryption

include/mbedtls/cipher.h

@@ -164,6 +164,9 @@ typedef enum {
     MBEDTLS_CIPHER_ARIA_128_CCM,         /**< Aria cipher with 128-bit key and CCM mode. */
     MBEDTLS_CIPHER_ARIA_192_CCM,         /**< Aria cipher with 192-bit key and CCM mode. */
     MBEDTLS_CIPHER_ARIA_256_CCM,         /**< Aria cipher with 256-bit key and CCM mode. */
+    MBEDTLS_CIPHER_AES_128_OFB,          /**< AES 128-bit cipher in OFB mode. */
+    MBEDTLS_CIPHER_AES_192_OFB,          /**< AES 192-bit cipher in OFB mode. */
+    MBEDTLS_CIPHER_AES_256_OFB,          /**< AES 256-bit cipher in OFB mode. */
 } mbedtls_cipher_type_t;
 
 /** Supported cipher modes. */
@@ -172,7 +175,7 @@ typedef enum {
     MBEDTLS_MODE_ECB,                    /**< The ECB cipher mode. */
     MBEDTLS_MODE_CBC,                    /**< The CBC cipher mode. */
     MBEDTLS_MODE_CFB,                    /**< The CFB cipher mode. */
-    MBEDTLS_MODE_OFB,                    /**< The OFB cipher mode - unsupported. */
+    MBEDTLS_MODE_OFB,                    /**< The OFB cipher mode. */
     MBEDTLS_MODE_CTR,                    /**< The CTR cipher mode. */
     MBEDTLS_MODE_GCM,                    /**< The GCM cipher mode. */
     MBEDTLS_MODE_STREAM,                 /**< The stream cipher mode. */

include/mbedtls/cipher_internal.h

@@ -64,6 +64,14 @@ struct mbedtls_cipher_base_t
                      unsigned char *output );
 #endif
 
+#if defined(MBEDTLS_CIPHER_MODE_OFB)
+    /** Encrypt using OFB (Full length) */
+    int (*ofb_func)( void *ctx, size_t length, size_t *iv_off,
+                     unsigned char *iv,
+                     const unsigned char *input,
+                     unsigned char *output );
+#endif
+
 #if defined(MBEDTLS_CIPHER_MODE_CTR)
     /** Encrypt using CTR */
     int (*ctr_func)( void *ctx, size_t length, size_t *nc_off,

include/mbedtls/config.h

@@ -501,6 +501,13 @@
  */
 #define MBEDTLS_CIPHER_MODE_CBC
 
+/**
+ * \def MBEDTLS_CIPHER_MODE_OFB
+ *
+ * Enable Output Feedback mode (OFB) for symmetric ciphers.
+ */
+#define MBEDTLS_CIPHER_MODE_OFB
+
 /**
  * \def MBEDTLS_CIPHER_MODE_CFB
  *