1 /* ghmac.h - data hashing functions
3 * Copyright (C) 2011 Collabora Ltd.
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Library General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Library General Public License for more details.
15 * You should have received a copy of the GNU Library General Public
16 * License along with this library; if not, write to the
17 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18 * Boston, MA 02111-1307, USA.
20 * Author: Stef Walter <stefw@collabora.co.uk>
29 #include "glib/galloca.h"
32 #include "gstrfuncs.h"
33 #include "gtestutils.h"
40 * @title: Secure HMAC Digests
41 * @short_description: Computes the HMAC for data
43 * HMACs should be used when producing a cookie or hash based on data and a key.
44 * Simple mechanisms for using SHA1 and other algorithms to digest a key and
45 * data together are vulnerable to various security issues. HMAC uses algorithms
46 * like SHA1 in a secure way to produce a digest of a key and data.
48 * Both the key and data are arbitrary byte arrays of bytes or characters.
50 * Support for HMAC Digests has been added in GLib 2.30
56 GChecksumType digest_type;
63 * @digest_type: the desired type of digest
64 * @key: (array length=key_len): the key for the HMAC
65 * @key_len: the length of the keys
67 * Creates a new #GHmac, using the digest algorithm @digest_type.
68 * If the @digest_type is not known, %NULL is returned.
69 * A #GHmac can be used to compute the HMAC of a key and an
70 * arbitrary binary blob, using different hashing algorithms.
72 * A #GHmac works by feeding a binary blob through g_hmac_update()
73 * until the data is complete; the digest can then be extracted
74 * using g_hmac_get_string(), which will return the checksum as a
75 * hexadecimal string; or g_hmac_get_digest(), which will return a
76 * array of raw bytes. Once either g_hmac_get_string() or
77 * g_hmac_get_digest() have been called on a #GHmac, the HMAC
78 * will be closed and it won't be possible to call g_hmac_update()
81 * Return value: the newly created #GHmac, or %NULL.
82 * Use g_hmac_unref() to free the memory allocated by it.
87 g_hmac_new (GChecksumType digest_type,
98 checksum = g_checksum_new (digest_type);
99 g_return_val_if_fail (checksum != NULL, NULL);
104 case G_CHECKSUM_SHA1:
105 block_size = 64; /* RFC 2104 */
107 case G_CHECKSUM_SHA256:
108 block_size = 64; /* RFC draft-kelly-ipsec-ciph-sha2-01 */
111 g_return_val_if_reached (NULL);
114 hmac = g_slice_new0 (GHmac);
116 hmac->digest_type = digest_type;
117 hmac->digesti = checksum;
118 hmac->digesto = g_checksum_new (digest_type);
120 buffer = g_alloca (block_size);
121 pad = g_alloca (block_size);
123 memset (buffer, 0, block_size);
125 /* If the key is too long, hash it */
126 if (key_len > block_size)
129 g_checksum_update (hmac->digesti, key, key_len);
130 g_checksum_get_digest (hmac->digesti, buffer, &len);
131 g_checksum_reset (hmac->digesti);
134 /* Otherwise pad it with zeros */
137 memcpy (buffer, key, key_len);
141 for (i = 0; i < block_size; i++)
142 pad[i] = 0x36 ^ buffer[i]; /* ipad value */
143 g_checksum_update (hmac->digesti, pad, block_size);
146 for (i = 0; i < block_size; i++)
147 pad[i] = 0x5c ^ buffer[i]; /* opad value */
148 g_checksum_update (hmac->digesto, pad, block_size);
155 * @hmac: the #GHmac to copy
157 * Copies a #GHmac. If @hmac has been closed, by calling
158 * g_hmac_get_string() or g_hmac_get_digest(), the copied
159 * HMAC will be closed as well.
161 * Return value: the copy of the passed #GHmac. Use g_hmac_unref()
162 * when finished using it.
167 g_hmac_copy (const GHmac *hmac)
171 g_return_val_if_fail (hmac != NULL, NULL);
173 copy = g_slice_new (GHmac);
174 copy->digest_type = hmac->digest_type;
175 copy->digesti = g_checksum_copy (hmac->digesti);
176 copy->digesto = g_checksum_copy (hmac->digesto);
183 * @hmac: a valid #GHmac.
185 * Atomically increments the reference count of @hmac by one.
186 * This function is MT-safe and may be called from any thread.
188 * Return value: the passed in #GHmac.
193 g_hmac_ref (GHmac *hmac)
195 g_return_val_if_fail (hmac != NULL, NULL);
197 g_atomic_int_inc (&hmac->ref_count);
206 * Atomically decrements the reference count of @hmac by one.
207 * If the reference count drops to 0, all keys and values will be
208 * destroyed, and all memory allocated by the hash table is released.
209 * This function is MT-safe and may be called from any thread.
210 * Frees the memory allocated for @hmac.
215 g_hmac_unref (GHmac *hmac)
217 g_return_if_fail (hmac != NULL);
219 if (g_atomic_int_dec_and_test (&hmac->ref_count))
221 g_checksum_free (hmac->digesti);
222 g_checksum_free (hmac->digesto);
223 g_slice_free (GHmac, hmac);
230 * @data: (array length=length): buffer used to compute the checksum
231 * @length: size of the buffer, or -1 if it is a null-terminated string.
233 * Feeds @data into an existing #GHmac. The HMAC must still be
234 * open, that is g_hmac_get_string() or g_hmac_get_digest() must
235 * not have been called on @hmac.
240 g_hmac_update (GHmac *hmac,
244 g_return_if_fail (hmac != NULL);
245 g_return_if_fail (length == 0 || data != NULL);
247 g_checksum_update (hmac->digesti, data, length);
254 * Gets the HMAC as an hexadecimal string.
256 * Once this function has been called the #GHmac can no longer be
257 * updated with g_hmac_update().
259 * The hexadecimal characters will be lower case.
261 * Return value: the hexadecimal representation of the HMAC. The
262 * returned string is owned by the HMAC and should not be modified
268 g_hmac_get_string (GHmac *hmac)
273 g_return_val_if_fail (hmac != NULL, NULL);
275 digest_len = g_checksum_type_get_length (hmac->digest_type);
276 buffer = g_malloc (digest_len);
278 g_hmac_get_digest (hmac, buffer, &digest_len);
279 return g_checksum_get_string (hmac->digesto);
283 * g_checksum_get_digest:
285 * @buffer: output buffer
286 * @digest_len: an inout parameter. The caller initializes it to the size of @buffer.
287 * After the call it contains the length of the digest.
289 * Gets the digest from @checksum as a raw binary array and places it
290 * into @buffer. The size of the digest depends on the type of checksum.
292 * Once this function has been called, the #GHmac is closed and can
293 * no longer be updated with g_checksum_update().
298 g_hmac_get_digest (GHmac *hmac,
304 g_return_if_fail (hmac != NULL);
306 len = g_checksum_type_get_length (hmac->digest_type);
307 g_return_if_fail (*digest_len >= len);
309 /* Use the same buffer, because we can :) */
310 g_checksum_get_digest (hmac->digesti, buffer, &len);
311 g_checksum_update (hmac->digesto, buffer, len);
312 g_checksum_get_digest (hmac->digesto, buffer, digest_len);
316 * g_compute_hmac_for_data:
317 * @digest_type: a #GChecksumType to use for the HMAC
318 * @key: (array length=key_len): the key to use in the HMAC
319 * @key_len: the length of the key
320 * @data: binary blob to compute the HMAC of
321 * @length: length of @data
323 * Computes the HMAC for a binary @data of @length. This is a
324 * convenience wrapper for g_hmac_new(), g_hmac_get_string()
325 * and g_hmac_unref().
327 * The hexadecimal string returned will be in lower case.
329 * Return value: the HMAC of the binary data as a string in hexadecimal.
330 * The returned string should be freed with g_free() when done using it.
335 g_compute_hmac_for_data (GChecksumType digest_type,
344 g_return_val_if_fail (length == 0 || data != NULL, NULL);
346 hmac = g_hmac_new (digest_type, key, key_len);
350 g_hmac_update (hmac, data, length);
351 retval = g_strdup (g_hmac_get_string (hmac));
358 * g_compute_hmac_for_string:
359 * @digest_type: a #GChecksumType to use for the HMAC
360 * @key: (array length=key_len): the key to use in the HMAC
361 * @key_len: the length of the key
362 * @str: the string to compute the HMAC for
363 * @length: the length of the string, or -1 if the string is null-terminated.
365 * Computes the HMAC for a string.
367 * The hexadecimal string returned will be in lower case.
369 * Return value: the HMAC as a hexadecimal string. The returned string
370 * should be freed with g_free() when done using it.
375 g_compute_hmac_for_string (GChecksumType digest_type,
381 g_return_val_if_fail (length == 0 || str != NULL, NULL);
384 length = strlen (str);
386 return g_compute_hmac_for_data (digest_type, key, key_len,
387 (const guchar *) str, length);