sha.pl

/*  Part of SWI-Prolog

    Author:        Jan Wielemaker
    E-mail:        J.Wielemaker@vu.nl
    WWW:           http://www.swi-prolog.org
    Copyright (c)  2007-2013, University of Amsterdam
                              VU University Amsterdam
    All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

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       notice, this list of conditions and the following disclaimer.

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       distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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*/

:- module(crypto_hash,
          [ sha_hash/3,                 % +Data, -Hash, +Options
            sha_new_ctx/2,              % -NewContext, +Options
            sha_hash_ctx/4,             % +OldCtx, +Data, -NewCtx, -Hash
            hmac_sha/4,                 % +Key, +Data, -Hash, +Options
            file_sha1/2,                % +File, -SHA1
            hash_atom/2                 % +Hash, -HexAtom
          ]).
:- use_foreign_library(foreign(sha4pl)).

/** <module> SHA secure hashes

This library provides a  lightweight   implementation  for computing SHA
secure  hashes.  A  general  secure  hash    interface  is  provided  by
library(crypto), part of the `ssl` package.

@see library(md5), library(hash_stream) and library(crypto).
*/

%!  sha_hash(+Data, -Hash, +Options) is det
%
%   Hash is the SHA hash of Data, The conversion is controlled
%   by Options:
%
%     * algorithm(+Algorithm)
%     One of =sha1= (default), =sha224=, =sha256=, =sha384= or
%     =sha512=
%     * encoding(+Encoding)
%     If Data is a sequence of character _codes_, this must be
%     translated into a sequence of _bytes_, because that is what
%     the hashing requires.  The default encoding is =utf8=.  The
%     other meaningful value is =octet=, claiming that Data contains
%     raw bytes.
%
%   @param  Data is either an atom, string or code-list
%   @param  Hash is a packed string

%!  sha_new_ctx(-NewContext, +Options) is det
%
%   NewContext is unified with the empty SHA computation context
%   (which includes the Options.)  It could later be passed to
%   sha_hash_ctx/4. For Options, see sha_hash/3.
%
%   @param  NewContext is an opaque pure Prolog term that is
%           subject to garbage collection.

%!  sha_hash_ctx(+OldContext, +Data, -NewContext, -Hash) is det
%
%   Hash is the SHA hash of Data.  NewContext is the new SHA
%   computation context, while OldContext is the old.  OldContext
%   may be produced by a prior invocation of either sha_new_ctx/3 or
%   sha_hash_ctx/4 itself.
%
%   This predicate allows a SHA function to be computed in chunks,
%   which may be important while working with Metalink (RFC 5854),
%   BitTorrent or similar technologies, or simply with big files.

%!  hmac_sha(+Key, +Data, -Hash, +Options) is det
%
%   For Options, see sha_hash/3.

%!  file_sha1(+File, -SHA1:atom) is det.
%
%   True when SHA1 is the SHA1 hash for the content of File. Options
%   is passed to open/4 and typically used to control whether binary
%   or text encoding must be used. The   output is compatible to the
%   =sha1sum= program found in many systems.

file_sha1(File, Hash) :-
    setup_call_cleanup(
        open(File, read, In, [type(binary)]),
        stream_sha1(In, Hash),
        close(In)).

stream_sha1(Stream, Hash) :-
    sha_new_ctx(Ctx0, [encoding(octet)]),
    update_hash(Stream, Ctx0, _Ctx, 0, HashCodes),
    hash_atom(HashCodes, Hash).

update_hash(In, Ctx0, Ctx, Hash0, Hash) :-
    at_end_of_stream(In),
    !,
    Ctx = Ctx0,
    Hash = Hash0.
update_hash(In, Ctx0, Ctx, _Hash0, Hash) :-
    read_pending_codes(In, Data, []),
    sha_hash_ctx(Ctx0, Data, Ctx1, Hash1),
    update_hash(In, Ctx1, Ctx, Hash1, Hash).



%!  hash_atom(+HashCodes, -HexAtom) is det.
%
%   Convert a list of bytes (integers 0..255) into the usual
%   hexadecimal notation.  E.g.
%
%     ==
%     ?- sha_hash('SWI-Prolog', Hash, []),
%        hash_atom(Hash, Hex).
%     Hash = [61, 128, 252, 38, 121, 69, 229, 85, 199|...],
%     Hex = '3d80fc267945e555c730403bd0ab0716e2a68c68'.
%     ==

hash_atom(Codes, Hash) :-
    phrase(bytes_hex(Codes), HexCodes),
    atom_codes(Hash, HexCodes).

bytes_hex([]) --> [].
bytes_hex([H|T]) -->
    { High is H>>4,
      Low is H /\ 0xf,
      code_type(C0, xdigit(High)),
      code_type(C1, xdigit(Low))
    },
    [C0,C1],
    bytes_hex(T).


		 /*******************************
		 *            SANDBOX		*
		 *******************************/

:- multifile sandbox:safe_primitive/1.

sandbox:safe_primitive(crypto_hash:sha_hash(_,_,_)).
sandbox:safe_primitive(crypto_hash:hmac_sha(_,_,_,_)).
sandbox:safe_primitive(crypto_hash:hash_atom(_,_)).