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dhobsd/libvmod-digest

Digest and HMAC vmod

===========
vmod_digest

Varnish Digest Module

:Manual section: 3
:Author: Kristian Lyngstøl
:Date: 2011-09-22
:Version: 0.3

SYNOPSIS

::

    import digest;
    
    digest.hmac_md5(<key>,<message>);
    digest.hmac_sha1(<key>, <message>);
    digest.hmac_sha256(<key>, <message));

    digest.base64(<string>);
    digest.base64url(<string>);
    digest.base64url_nopad(<string>);
    digest.base64_hex(<string>);
    digest.base64url_hex(<string>);
    digest.base64url_nopad_hex(<string>);
    digest.base64_decode(<string>);
    digest.base64url_decode(<string>);
    digest.base64url_nopad_decode(<string>);

    digest.version()

    digest.hash_sha1(<string>);
    digest.hash_sha224(<string>);
    digest.hash_sha256(<string>);
    digest.hash_sha384(<string>);
    digest.hash_sha512(<string>);
    digest.hash_gost(<string>);
    digest.hash_md2(<string>);
    digest.hash_md4(<string>);
    digest.hash_md5(<string>);
    digest.hash_crc32(<string>);
    digest.hash_crc32b(<string>);
    digest.hash_adler32(<string>);
    digest.hash_haval128(<string>);
    digest.hash_haval160(<string>);
    digest.hash_haval192(<string>);
    digest.hash_haval224(<string>);
    digest.hash_haval256(<string>);
    digest.hash_ripemd128(<string>);
    digest.hash_ripemd160(<string>);
    digest.hash_ripemd256(<string>);
    digest.hash_ripemd320(<string>);
    digest.hash_tiger(<string>);
    digest.hash_tiger128(<string>);
    digest.hash_tiger160(<string>);
    digest.hash_snefru128(<string>);
    digest.hash_snefru256(<string>);

DESCRIPTION

Varnish Module (vmod) for computing HMAC, message digests and working with
base64.

All HMAC- and hash-functionality is provided by libmhash, while base64 is
implemented locally.

FUNCTIONS

Example VCL::

backend foo { ... };

import digest;

sub vcl_recv {
	if (digest.hmac_sha256("key",req.http.x-some-header) !=
		digest.hmac_sha256("key",req.http.x-some-header-signed))
	{
		return (synth(401, "Naughty user!"));
	}
}

hmac_(hash)

Prototype
::

        digest.hmac_md5(<key>,<message>);
        digest.hmac_sha1(<key>, <message>);
        digest.hmac_sha256(<key>, <message));

Returns
String. Hex-encoded prepended with 0x.
Description
All the various hmac-functions work the same, but use a different
hash mechanism.
Example
::

            set resp.http.x-data-sig = 
                    digest.hmac_sha256("secretkey",resp.http.x-data);

base64, base64url, base64url_nopad

Prototype
::

            digest.base64(<string>);
            digest.base64url(<string>);
            digest.base64url_nopad(<string>);

Returns
String
Description
Returns the base64-encoded version of the input-string. The
base64url-variant uses base64 url-encoding (+/ replaced by -_) and
the base64url_nopad does the same, but avoids adding padding. The
latter is more commonly used, though an (allowed) exception to the
RFC4648.
Example
::

            set resp.http.x-data-sig = 
                    digest.base64({"content with
                    newline in it"});

base64_hex, base64url_hex, base64url_nopad_hex

Prototype
::

            digest.base64_hex(<string>);
            digest.base64url_hex(<string>);
            digest.base64url_nopad_hex(<string>);

Returns
String
Description
Returns the base64-encoded version of the hex encoded input-string. The
input-string can start with an optional 0x. Input is hex-decoded into binary
and the encoding is identical to base64, base64url, and base64url_nopad.
Example
::

            set resp.http.x-data-sig =
                    digest.base64_hex("0xdd26bfddf122c1055d4c");

hash_(algorithm)

Prototype
::

            digest.hash_sha1(<string>);
            digest.hash_sha224(<string>);
            digest.hash_sha256(<string>);
            digest.hash_sha384(<string>);
            digest.hash_sha512(<string>);
            digest.hash_gost(<string>);
            digest.hash_md2(<string>);
            digest.hash_md4(<string>);
            digest.hash_md5(<string>);
            digest.hash_crc32(<string>);
            digest.hash_crc32b(<string>);
            digest.hash_adler32(<string>);
            digest.hash_haval128(<string>);
            digest.hash_haval160(<string>);
            digest.hash_haval192(<string>);
            digest.hash_haval224(<string>);
            digest.hash_haval256(<string>);
            digest.hash_ripemd128(<string>);
            digest.hash_ripemd160(<string>);
            digest.hash_ripemd256(<string>);
            digest.hash_ripemd320(<string>);
            digest.hash_tiger(<string>);
            digest.hash_tiger128(<string>);
            digest.hash_tiger160(<string>);
            digest.hash_snefru128(<string>);
            digest.hash_snefru256(<string>);

Returns
String
Description
Computes the digest/hash of the supplied, using the specified hash
algorithm. If in doubt as to which to pick, use SHA256. For
detailed discussions, see The Internet.
Example
::

            set resp.http.x-data-md5 = 
                    digest.hash_md5(resp.http.x-data);

base64_decode, base64url_decode, base64url_nopad_decode

Prototype
::

            digest.base64_decode(<string>);
            digest.base64url_decode(<string>);
            digest.base64url_nopad_decode(<string>);

Returns
String
Description
Decodes the bas64 and base64url-encoded strings. All functions
treat padding the same, meaning base64url_decode and
base64url_nopad_decode are identical, but available for consistency
and practicality.
Example
::
synthetic(digest.base64_decode(req.http.x-parrot));

version

Prototype
::

            digest.version()

Returns
string
Description
Returns the string constant version-number of the digest vmod.
Example
::

            set resp.http.X-digest-version = digest.version();

INSTALLATION

The source tree is based on autotools to configure the building, and
does also have the necessary bits in place to do functional unit tests
using the varnishtest tool.

Building requires the Varnish header files and uses pkg-config to find
the necessary paths.

Usage::

./autogen.sh
./configure

If you have installed Varnish to a non-standard directory, call
autogen.sh and configure with PKG_CONFIG_PATH pointing to
the appropriate path. For example, when varnishd configure was called
with --prefix=$PREFIX, use

PKG_CONFIG_PATH=${PREFIX}/lib/pkgconfig
export PKG_CONFIG_PATH

Make targets:

  • make - builds the vmod.
  • make install - installs your vmod.
  • make check - runs the unit tests in src/tests/*.vtc
  • make distcheck - run check and prepare a tarball of the vmod.

ACKNOWLEDGEMENTS

Author: Kristian Lyngstøl kristian@varnish-software.com, Varnish Software AS

This Vmod was written for Media Norge, Schibsted and others.

The bulk of the functionality is acquired through libmhash

Bug reports by: Magnus Hagander

HISTORY

Version 0.1: Initial version, mostly feature-complete

Version 0.2: Mainly build-related cleanups, no feature-changes

Version 0.3: Handle empty/NULL strings for hashes and keys.

BUGS

No bugs at all!

If the key is NULL for hmac-functions, the function will fail and return
NULL itself, and do no hmac-computation at all. This should be used as an
indication of some greater flaw in your software/VCL. (I.e.: Your key
should be under your control, not user-supplied without verification).

The base64url_nopad_decode() and base64url_decode() functions do not
differ much. The exception is that nopad_decode() does not know about
padding at all, and might get confused if the input actually is padded.

SEE ALSO

COPYRIGHT

This document is licensed under the same license as the
libvmod-digest project. See LICENSE for details.

  • Copyright (c) 2011 Varnish Software

Languages

C82.3%Makefile10.0%Shell7.6%

Contributors

MBKRFGDAAONIREZM
Other
Created March 12, 2016
Updated March 12, 2016
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