/* ghmac.h - data hashing functions
*
* Copyright (C) 2011 Collabora Ltd.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*
* Author: Stef Walter <stefw@collabora.co.uk>
*/
#include "config.h"
#include <string.h>
#include "ghmac.h"
#include "glib/galloca.h"
#include "gatomic.h"
#include "gslice.h"
#include "gmem.h"
#include "gstrfuncs.h"
#include "gtestutils.h"
#include "gtypes.h"
#include "glibintl.h"
/**
* SECTION:hmac
* @title: Secure HMAC Digests
* @short_description: computes the HMAC for data
*
* HMACs should be used when producing a cookie or hash based on data
* and a key. Simple mechanisms for using SHA1 and other algorithms to
* digest a key and data together are vulnerable to various security
* issues. <ulink url="http://en.wikipedia.org/wiki/HMAC">HMAC</ulink>
* uses algorithms like SHA1 in a secure way to produce a digest of a
* key and data.
*
* Both the key and data are arbitrary byte arrays of bytes or characters.
*
* Support for HMAC Digests has been added in GLib 2.30.
*/
struct _GHmac
{
int ref_count;
GChecksumType digest_type;
GChecksum *digesti;
GChecksum *digesto;
};
/**
* g_hmac_new:
* @digest_type: the desired type of digest
* @key: (array length=key_len): the key for the HMAC
* @key_len: the length of the keys
*
* Creates a new #GHmac, using the digest algorithm @digest_type.
* If the @digest_type is not known, %NULL is returned.
* A #GHmac can be used to compute the HMAC of a key and an
* arbitrary binary blob, using different hashing algorithms.
*
* A #GHmac works by feeding a binary blob through g_hmac_update()
* until the data is complete; the digest can then be extracted
* using g_hmac_get_string(), which will return the checksum as a
* hexadecimal string; or g_hmac_get_digest(), which will return a
* array of raw bytes. Once either g_hmac_get_string() or
* g_hmac_get_digest() have been called on a #GHmac, the HMAC
* will be closed and it won't be possible to call g_hmac_update()
* on it anymore.
*
* Return value: the newly created #GHmac, or %NULL.
* Use g_hmac_unref() to free the memory allocated by it.
*
* Since: 2.30
*/
GHmac *
g_hmac_new (GChecksumType digest_type,
const guchar *key,
gsize key_len)
{
GChecksum *checksum;
GHmac *hmac;
guchar *buffer;
guchar *pad;
gsize i, len;
gsize block_size;
checksum = g_checksum_new (digest_type);
g_return_val_if_fail (checksum != NULL, NULL);
switch (digest_type)
{
case G_CHECKSUM_MD5:
case G_CHECKSUM_SHA1:
block_size = 64; /* RFC 2104 */
break;
case G_CHECKSUM_SHA256:
block_size = 64; /* RFC draft-kelly-ipsec-ciph-sha2-01 */
break;
default:
g_return_val_if_reached (NULL);
}
hmac = g_slice_new0 (GHmac);
hmac->ref_count = 1;
hmac->digest_type = digest_type;
hmac->digesti = checksum;
hmac->digesto = g_checksum_new (digest_type);
buffer = g_alloca (block_size);
pad = g_alloca (block_size);
memset (buffer, 0, block_size);
/* If the key is too long, hash it */
if (key_len > block_size)
{
len = block_size;
g_checksum_update (hmac->digesti, key, key_len);
g_checksum_get_digest (hmac->digesti, buffer, &len);
g_checksum_reset (hmac->digesti);
}
/* Otherwise pad it with zeros */
else
{
memcpy (buffer, key, key_len);
}
/* First pad */
for (i = 0; i < block_size; i++)
pad[i] = 0x36 ^ buffer[i]; /* ipad value */
g_checksum_update (hmac->digesti, pad, block_size);
/* Second pad */
for (i = 0; i < block_size; i++)
pad[i] = 0x5c ^ buffer[i]; /* opad value */
g_checksum_update (hmac->digesto, pad, block_size);
return hmac;
}
/**
* g_hmac_copy:
* @hmac: the #GHmac to copy
*
* Copies a #GHmac. If @hmac has been closed, by calling
* g_hmac_get_string() or g_hmac_get_digest(), the copied
* HMAC will be closed as well.
*
* Return value: the copy of the passed #GHmac. Use g_hmac_unref()
* when finished using it.
*
* Since: 2.30
*/
GHmac *
g_hmac_copy (const GHmac *hmac)
{
GHmac *copy;
g_return_val_if_fail (hmac != NULL, NULL);
copy = g_slice_new (GHmac);
copy->ref_count = 1;
copy->digest_type = hmac->digest_type;
copy->digesti = g_checksum_copy (hmac->digesti);
copy->digesto = g_checksum_copy (hmac->digesto);
return copy;
}
/**
* g_hmac_ref:
* @hmac: a valid #GHmac
*
* Atomically increments the reference count of @hmac by one.
*
* This function is MT-safe and may be called from any thread.
*
* Return value: the passed in #GHmac.
*
* Since: 2.30
**/
GHmac *
g_hmac_ref (GHmac *hmac)
{
g_return_val_if_fail (hmac != NULL, NULL);
g_atomic_int_inc (&hmac->ref_count);
return hmac;
}
/**
* g_hmac_unref:
* @hmac: a #GHmac
*
* Atomically decrements the reference count of @hmac by one.
*
* If the reference count drops to 0, all keys and values will be
* destroyed, and all memory allocated by the hash table is released.
* This function is MT-safe and may be called from any thread.
* Frees the memory allocated for @hmac.
*
* Since: 2.30
*/
void
g_hmac_unref (GHmac *hmac)
{
g_return_if_fail (hmac != NULL);
if (g_atomic_int_dec_and_test (&hmac->ref_count))
{
g_checksum_free (hmac->digesti);
g_checksum_free (hmac->digesto);
g_slice_free (GHmac, hmac);
}
}
/**
* g_hmac_update:
* @hmac: a #GHmac
* @data: (array length=length): buffer used to compute the checksum
* @length: size of the buffer, or -1 if it is a nul-terminated string
*
* Feeds @data into an existing #GHmac.
*
* The HMAC must still be open, that is g_hmac_get_string() or
* g_hmac_get_digest() must not have been called on @hmac.
*
* Since: 2.30
*/
void
g_hmac_update (GHmac *hmac,
const guchar *data,
gssize length)
{
g_return_if_fail (hmac != NULL);
g_return_if_fail (length == 0 || data != NULL);
g_checksum_update (hmac->digesti, data, length);
}
/**
* g_hmac_get_string:
* @hmac: a #GHmac
*
* Gets the HMAC as an hexadecimal string.
*
* Once this function has been called the #GHmac can no longer be
* updated with g_hmac_update().
*
* The hexadecimal characters will be lower case.
*
* Return value: the hexadecimal representation of the HMAC. The
* returned string is owned by the HMAC and should not be modified
* or freed.
*
* Since: 2.30
*/
const gchar *
g_hmac_get_string (GHmac *hmac)
{
guint8 *buffer;
gsize digest_len;
g_return_val_if_fail (hmac != NULL, NULL);
digest_len = g_checksum_type_get_length (hmac->digest_type);
buffer = g_alloca (digest_len);
/* This is only called for its side-effect of updating hmac->digesto... */
g_hmac_get_digest (hmac, buffer, &digest_len);
/* ... because we get the string from the checksum rather than
* stringifying buffer ourselves
*/
return g_checksum_get_string (hmac->digesto);
}
/**
* g_hmac_get_digest:
* @hmac: a #GHmac
* @buffer: output buffer
* @digest_len: an inout parameter. The caller initializes it to the
* size of @buffer. After the call it contains the length of the digest
*
* Gets the digest from @checksum as a raw binary array and places it
* into @buffer. The size of the digest depends on the type of checksum.
*
* Once this function has been called, the #GHmac is closed and can
* no longer be updated with g_checksum_update().
*
* Since: 2.30
*/
void
g_hmac_get_digest (GHmac *hmac,
guint8 *buffer,
gsize *digest_len)
{
gsize len;
g_return_if_fail (hmac != NULL);
len = g_checksum_type_get_length (hmac->digest_type);
g_return_if_fail (*digest_len >= len);
/* Use the same buffer, because we can :) */
g_checksum_get_digest (hmac->digesti, buffer, &len);
g_checksum_update (hmac->digesto, buffer, len);
g_checksum_get_digest (hmac->digesto, buffer, digest_len);
}
/**
* g_compute_hmac_for_data:
* @digest_type: a #GChecksumType to use for the HMAC
* @key: (array length=key_len): the key to use in the HMAC
* @key_len: the length of the key
* @data: binary blob to compute the HMAC of
* @length: length of @data
*
* Computes the HMAC for a binary @data of @length. This is a
* convenience wrapper for g_hmac_new(), g_hmac_get_string()
* and g_hmac_unref().
*
* The hexadecimal string returned will be in lower case.
*
* Return value: the HMAC of the binary data as a string in hexadecimal.
* The returned string should be freed with g_free() when done using it.
*
* Since: 2.30
*/
gchar *
g_compute_hmac_for_data (GChecksumType digest_type,
const guchar *key,
gsize key_len,
const guchar *data,
gsize length)
{
GHmac *hmac;
gchar *retval;
g_return_val_if_fail (length == 0 || data != NULL, NULL);
hmac = g_hmac_new (digest_type, key, key_len);
if (!hmac)
return NULL;
g_hmac_update (hmac, data, length);
retval = g_strdup (g_hmac_get_string (hmac));
g_hmac_unref (hmac);
return retval;
}
/**
* g_compute_hmac_for_string:
* @digest_type: a #GChecksumType to use for the HMAC
* @key: (array length=key_len): the key to use in the HMAC
* @key_len: the length of the key
* @str: the string to compute the HMAC for
* @length: the length of the string, or -1 if the string is nul-terminated
*
* Computes the HMAC for a string.
*
* The hexadecimal string returned will be in lower case.
*
* Return value: the HMAC as a hexadecimal string.
* The returned string should be freed with g_free()
* when done using it.
*
* Since: 2.30
*/
gchar *
g_compute_hmac_for_string (GChecksumType digest_type,
const guchar *key,
gsize key_len,
const gchar *str,
gssize length)
{
g_return_val_if_fail (length == 0 || str != NULL, NULL);
if (length < 0)
length = strlen (str);
return g_compute_hmac_for_data (digest_type, key, key_len,
(const guchar *) str, length);
}