221 lines
9.2 KiB
Ada
221 lines
9.2 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT LIBRARY COMPONENTS --
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-- --
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-- G N A T . S E C U R E _ H A S H E S --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 2009-2014, Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This package provides common supporting code for a family of secure
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-- hash functions (including MD5 and the FIPS PUB 180-3 functions SHA-1,
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-- SHA-224, SHA-256, SHA-384 and SHA-512).
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-- This is an internal unit and should be not used directly in applications.
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-- Use GNAT.MD5 and GNAT.SHA* instead.
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with Ada.Streams; use Ada.Streams;
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with Interfaces;
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with System;
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package GNAT.Secure_Hashes is
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type Buffer_Type is new String;
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for Buffer_Type'Alignment use 8;
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-- Secure hash functions use a string buffer that is also accessed as an
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-- array of words, which may require up to 64 bit alignment.
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-- The function-independent part of processing state: A buffer of data
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-- being accumulated until a complete block is ready for hashing.
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type Message_State (Block_Length : Natural) is record
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Last : Natural := 0;
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-- Index of last used element in Buffer
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Length : Interfaces.Unsigned_64 := 0;
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-- Total length of processed data
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Buffer : Buffer_Type (1 .. Block_Length);
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-- Data buffer
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end record;
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-- The function-specific part of processing state:
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-- Each hash function maintains an internal state as an array of words,
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-- which is ultimately converted to a stream representation with the
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-- appropriate bit order.
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generic
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type Word is mod <>;
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-- Either 32 or 64 bits
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with procedure Swap (X : System.Address);
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-- Byte swapping function for a Word at X
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Hash_Bit_Order : System.Bit_Order;
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-- Bit order of the produced hash
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package Hash_Function_State is
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type State is array (Natural range <>) of Word;
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-- Used to store a hash function's internal state
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procedure To_Hash
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(H : State;
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H_Bits : out Stream_Element_Array);
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-- Convert H to stream representation with the given bit order. If
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-- H_Bits is smaller than the internal hash state, then the state
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-- is truncated.
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end Hash_Function_State;
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-- Generic hashing framework: The user interface for each implemented
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-- secure hash function is an instance of this generic package.
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generic
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Block_Words : Natural;
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-- Number of words in each block
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State_Words : Natural;
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-- Number of words in internal state
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Hash_Words : Natural;
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-- Number of words in the final hash (must be no greater than
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-- State_Words).
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Hash_Bit_Order : System.Bit_Order;
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-- Bit order used for conversion between bit representation and word
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-- representation.
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with package Hash_State is new Hash_Function_State (<>);
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-- Hash function state package
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Initial_State : Hash_State.State;
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-- Initial value of the hash function state
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with procedure Transform
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(H : in out Hash_State.State;
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M : in out Message_State);
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-- Transformation function updating H by processing a complete data
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-- block from M.
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package H is
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-- The visible part of H is the interface to secure hashing functions
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-- that is exposed to user applications, and is intended to remain
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-- a stable interface.
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pragma Assert (Hash_Words <= State_Words);
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type Context is private;
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-- The internal processing state of the hashing function
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function "=" (L, R : Context) return Boolean is abstract;
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-- Context is the internal, implementation defined intermediate state
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-- in a hash computation, and no specific semantics can be expected on
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-- equality of context values. Only equality of final hash values (as
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-- returned by the [Wide_]Digest functions below) is meaningful.
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Initial_Context : constant Context;
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-- Initial value of a Context object. May be used to reinitialize
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-- a Context value by simple assignment of this value to the object.
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function HMAC_Initial_Context (Key : String) return Context;
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-- Initial Context for HMAC computation with the given Key
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procedure Update (C : in out Context; Input : String);
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procedure Wide_Update (C : in out Context; Input : Wide_String);
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procedure Update
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(C : in out Context;
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Input : Stream_Element_Array);
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-- Update C to process the given input. Successive calls to Update are
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-- equivalent to a single call with the concatenation of the inputs. For
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-- the Wide_String version, each Wide_Character is processed low order
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-- byte first.
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Word_Length : constant Natural := Hash_State.Word'Size / 8;
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Hash_Length : constant Natural := Hash_Words * Word_Length;
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subtype Binary_Message_Digest is
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Stream_Element_Array (1 .. Stream_Element_Offset (Hash_Length));
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-- The fixed-length byte array returned by Digest, providing
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-- the hash in binary representation.
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function Digest (C : Context) return Binary_Message_Digest;
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-- Return hash or HMAC for the data accumulated with C
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function Digest (S : String) return Binary_Message_Digest;
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function Wide_Digest (W : Wide_String) return Binary_Message_Digest;
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function Digest
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(A : Stream_Element_Array) return Binary_Message_Digest;
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-- These functions are equivalent to the corresponding Update (or
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-- Wide_Update) on a default initialized Context, followed by Digest
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-- on the resulting Context.
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subtype Message_Digest is String (1 .. 2 * Hash_Length);
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-- The fixed-length string returned by Digest, providing the hash in
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-- hexadecimal representation.
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function Digest (C : Context) return Message_Digest;
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-- Return hash or HMAC for the data accumulated with C in hexadecimal
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-- representation.
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function Digest (S : String) return Message_Digest;
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function Wide_Digest (W : Wide_String) return Message_Digest;
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function Digest (A : Stream_Element_Array) return Message_Digest;
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-- These functions are equivalent to the corresponding Update (or
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-- Wide_Update) on a default initialized Context, followed by Digest
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-- on the resulting Context.
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private
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Block_Length : constant Natural := Block_Words * Word_Length;
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-- Length in bytes of a data block
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subtype Key_Length is
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Stream_Element_Offset range 0 .. Stream_Element_Offset (Block_Length);
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-- KL is 0 for a normal hash context, > 0 for HMAC
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type Context (KL : Key_Length := 0) is record
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Key : Stream_Element_Array (1 .. KL);
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-- HMAC key
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H_State : Hash_State.State (0 .. State_Words - 1) := Initial_State;
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-- Function-specific state
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M_State : Message_State (Block_Length);
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-- Function-independent state (block buffer)
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end record;
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Initial_Context : constant Context (KL => 0) := (others => <>);
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-- Initial values are provided by default initialization of Context
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end H;
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end GNAT.Secure_Hashes;
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