Additional cipher_info getters

ChangeLog.d/additional_cipher_info_getters.txt

@@ -0,0 +1,3 @@
+Features
+   * Add functions to get the IV and block size from cipher_info structs.
+   * Add functions to check if a cipher supports variable IV or key size.

include/mbedtls/cipher.h

@@ -507,6 +507,80 @@ static inline const char *mbedtls_cipher_info_get_name(
         return( info->MBEDTLS_PRIVATE(name) );
 }
 
+/**
+ * \brief       This function returns the size of the IV or nonce
+ *              for the cipher info structure, in bytes.
+ *
+ * \param info  The cipher info structure. This may be \c NULL.
+ *
+ * \return      The recommended IV size.
+ * \return      \c 0 for ciphers not using an IV or a nonce.
+ * \return      \c 0 if \p info is \c NULL.
+ */
+static inline size_t mbedtls_cipher_info_get_iv_size(
+    const mbedtls_cipher_info_t *info )
+{
+    if( info == NULL )
+        return( 0 );
+
+    return( (size_t) info->MBEDTLS_PRIVATE(iv_size) );
+}
+
+/**
+ * \brief        This function returns the block size of the given
+ *               cipher info structure in bytes.
+ *
+ * \param info   The cipher info structure. This may be \c NULL.
+ *
+ * \return       The block size of the cipher.
+ * \return       \c 1 if the cipher is a stream cipher.
+ * \return       \c 0 if \p info is \c NULL.
+ */
+static inline size_t mbedtls_cipher_info_get_block_size(
+    const mbedtls_cipher_info_t *info )
+{
+    if( info == NULL )
+        return( 0 );
+
+    return( (size_t) info->MBEDTLS_PRIVATE(block_size) );
+}
+
+/**
+ * \brief        This function returns a non-zero value if the key length for
+ *               the given cipher is variable.
+ *
+ * \param info   The cipher info structure. This may be \c NULL.
+ *
+ * \return       Non-zero if the key length is variable, \c 0 otherwise.
+ * \return       \c 0 if the given pointer is \c NULL.
+ */
+static inline int mbedtls_cipher_info_has_variable_key_bitlen(
+    const mbedtls_cipher_info_t *info )
+{
+    if( info == NULL )
+        return( 0 );
+
+    return( info->MBEDTLS_PRIVATE(flags) & MBEDTLS_CIPHER_VARIABLE_KEY_LEN );
+}
+
+/**
+ * \brief        This function returns a non-zero value if the IV size for
+ *               the given cipher is variable.
+ *
+ * \param info   The cipher info structure. This may be \c NULL.
+ *
+ * \return       Non-zero if the IV size is variable, \c 0 otherwise.
+ * \return       \c 0 if the given pointer is \c NULL.
+ */
+static inline int mbedtls_cipher_info_has_variable_iv_size(
+    const mbedtls_cipher_info_t *info )
+{
+    if( info == NULL )
+        return( 0 );
+
+    return( info->MBEDTLS_PRIVATE(flags) & MBEDTLS_CIPHER_VARIABLE_IV_LEN );
+}
+
 /**
  * \brief               This function initializes a \p cipher_context as NONE.
  *
@@ -583,11 +657,13 @@ int mbedtls_cipher_setup_psa( mbedtls_cipher_context_t *ctx,
 #endif /* MBEDTLS_USE_PSA_CRYPTO */
 
 /**
- * \brief        This function returns the block size of the given cipher.
+ * \brief        This function returns the block size of the given cipher
+ *               in bytes.
  *
- * \param ctx    The context of the cipher. This must be initialized.
+ * \param ctx    The context of the cipher.
  *
  * \return       The block size of the underlying cipher.
+ * \return       \c 1 if the cipher is a stream cipher.
  * \return       \c 0 if \p ctx has not been initialized.
  */
 static inline unsigned int mbedtls_cipher_get_block_size(

tests/suites/test_suite_cipher.function

@@ -18,7 +18,7 @@
 static int check_cipher_info( mbedtls_cipher_type_t type,
                               const mbedtls_cipher_info_t *info )
 {
-    size_t key_bitlen;
+    size_t key_bitlen, block_size, iv_size;
 
     TEST_ASSERT( info != NULL );
     TEST_EQUAL( type, mbedtls_cipher_info_get_type( info ) );
@@ -33,8 +33,14 @@ static int check_cipher_info( mbedtls_cipher_type_t type,
     TEST_ASSERT( mbedtls_cipher_info_from_string( info->name ) == info );
 
     key_bitlen = mbedtls_cipher_info_get_key_bitlen( info );
+    block_size = mbedtls_cipher_info_get_block_size( info );
+    iv_size = mbedtls_cipher_info_get_iv_size( info );
     if( info->type == MBEDTLS_CIPHER_NULL )
+    {
         TEST_ASSERT( key_bitlen == 0 );
+        TEST_ASSERT( block_size == 1 );
+        TEST_ASSERT( iv_size == 0 );
+    }
     else if( info->mode == MBEDTLS_MODE_XTS )
     {
         TEST_ASSERT( key_bitlen == 256 ||
@@ -44,14 +50,28 @@ static int check_cipher_info( mbedtls_cipher_type_t type,
     else if( ! strncmp( info->name, "DES-EDE3-", 9 ) )
     {
         TEST_ASSERT( key_bitlen == 192 );
+        TEST_ASSERT( ! mbedtls_cipher_info_has_variable_key_bitlen( info ) );
+        TEST_ASSERT( block_size == 8 );
     }
     else if( ! strncmp( info->name, "DES-EDE-", 8 ) )
     {
         TEST_ASSERT( key_bitlen == 128 );
+        TEST_ASSERT( ! mbedtls_cipher_info_has_variable_key_bitlen( info ) );
+        TEST_ASSERT( block_size == 8 );
     }
     else if( ! strncmp( info->name, "DES-", 4 ) )
     {
         TEST_ASSERT( key_bitlen == 64 );
+        TEST_ASSERT( ! mbedtls_cipher_info_has_variable_key_bitlen( info ) );
+        TEST_ASSERT( block_size == 8 );
+    }
+    else if( ! strncmp( info->name, "AES", 3 ) )
+    {
+        TEST_ASSERT( key_bitlen == 128 ||
+                     key_bitlen == 192 ||
+                     key_bitlen == 256 );
+        TEST_ASSERT( ! mbedtls_cipher_info_has_variable_key_bitlen( info ) );
+        TEST_ASSERT( block_size == 16 );
     }
     else
     {
@@ -60,6 +80,23 @@ static int check_cipher_info( mbedtls_cipher_type_t type,
                      key_bitlen == 256 );
     }
 
+    if( strstr( info->name, "-ECB" ) != NULL )
+    {
+        TEST_ASSERT( iv_size == 0 );
+        TEST_ASSERT( ! mbedtls_cipher_info_has_variable_iv_size( info ) );
+    }
+    else if( strstr( info->name, "-CBC" ) != NULL ||
+             strstr( info->name, "-CTR" ) != NULL )
+    {
+        TEST_ASSERT( iv_size == block_size );
+        TEST_ASSERT( ! mbedtls_cipher_info_has_variable_iv_size( info ) );
+    }
+    else if( strstr( info->name, "-GCM" ) != NULL )
+    {
+        TEST_ASSERT( iv_size == block_size - 4 );
+        TEST_ASSERT( mbedtls_cipher_info_has_variable_iv_size( info ) );
+    }
+
     return( 1 );
 
 exit: