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/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* lib/crypto/builtin/pbkdf2.c - Implementation of PBKDF2 from RFC 2898 */
/*
* Copyright 2002, 2008 by the Massachusetts Institute of Technology.
* All Rights Reserved.
*
* Export of this software from the United States of America may
* require a specific license from the United States Government.
* It is the responsibility of any person or organization contemplating
* export to obtain such a license before exporting.
*
* WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
* distribute this software and its documentation for any purpose and
* without fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright notice and
* this permission notice appear in supporting documentation, and that
* the name of M.I.T. not be used in advertising or publicity pertaining
* to distribution of the software without specific, written prior
* permission. Furthermore if you modify this software you must label
* your software as modified software and not distribute it in such a
* fashion that it might be confused with the original M.I.T. software.
* M.I.T. makes no representations about the suitability of
* this software for any purpose. It is provided "as is" without express
* or implied warranty.
*/
#include <ctype.h>
#include "crypto_int.h"
/*
* RFC 2898 specifies PBKDF2 in terms of an underlying pseudo-random
* function with two arguments (password and salt||blockindex). Right
* now we only use PBKDF2 with the hmac-sha1 PRF, also specified in
* RFC 2898, which invokes HMAC with the password as the key and the
* second argument as the text. (HMAC accepts any key size up to the
* block size; the password is pre-hashed with unkeyed SHA1 if it is
* longer than the block size.)
*
* For efficiency, it is better to generate the key from the password
* once at the beginning, so we specify prf_fn in terms of a
* krb5_key first argument. That might not be convenient for a PRF
* which uses the password in some other way, so this might need to be
* adjusted in the future.
*/
typedef krb5_error_code (*prf_fn)(krb5_key pass, krb5_data *salt,
krb5_data *out);
static int debug_hmac = 0;
static void printd (const char *descr, krb5_data *d) {
unsigned int i, j;
const int r = 16;
printf("%s:", descr);
for (i = 0; i < d->length; i += r) {
printf("\n %04x: ", i);
for (j = i; j < i + r && j < d->length; j++)
printf(" %02x", 0xff & d->data[j]);
for (; j < i + r; j++)
printf(" ");
printf(" ");
for (j = i; j < i + r && j < d->length; j++) {
int c = 0xff & d->data[j];
printf("%c", isprint(c) ? c : '.');
}
}
printf("\n");
}
/*
* Implements the hmac-sha1 PRF. pass has been pre-hashed (if
* necessary) and converted to a key already; salt has had the block
* index appended to the original salt.
*
* NetBSD 8 declares an hmac() function in stdlib.h, so avoid that name.
*/
static krb5_error_code
k5_hmac(const struct krb5_hash_provider *hash, krb5_keyblock *pass,
krb5_data *salt, krb5_data *out)
{
krb5_error_code err;
krb5_crypto_iov iov;
if (debug_hmac)
printd(" hmac input", salt);
iov.flags = KRB5_CRYPTO_TYPE_DATA;
iov.data = *salt;
err = krb5int_hmac_keyblock(hash, pass, &iov, 1, out);
if (err == 0 && debug_hmac)
printd(" hmac output", out);
return err;
}
static krb5_error_code
F(char *output, char *u_tmp1, char *u_tmp2,
const struct krb5_hash_provider *hash, size_t hlen, krb5_keyblock *pass,
const krb5_data *salt, unsigned long count, int i)
{
unsigned char ibytes[4];
unsigned int j, k;
krb5_data sdata;
krb5_data out;
krb5_error_code err;
/* Compute U_1. */
store_32_be(i, ibytes);
memcpy(u_tmp2, salt->data, salt->length);
memcpy(u_tmp2 + salt->length, ibytes, 4);
sdata = make_data(u_tmp2, salt->length + 4);
out = make_data(u_tmp1, hlen);
err = k5_hmac(hash, pass, &sdata, &out);
if (err)
return err;
memcpy(output, u_tmp1, hlen);
/* Compute U_2, .. U_c. */
sdata.length = hlen;
for (j = 2; j <= count; j++) {
memcpy(u_tmp2, u_tmp1, hlen);
err = k5_hmac(hash, pass, &sdata, &out);
if (err)
return err;
/* And xor them together. */
for (k = 0; k < hlen; k++)
output[k] ^= u_tmp1[k];
}
return 0;
}
static krb5_error_code
pbkdf2(const struct krb5_hash_provider *hash, krb5_keyblock *pass,
const krb5_data *salt, unsigned long count, const krb5_data *output)
{
size_t hlen = hash->hashsize;
int l, i;
char *utmp1, *utmp2;
char utmp3[128]; /* XXX length shouldn't be hardcoded! */
if (output->length == 0 || hlen == 0)
abort();
/* Step 1 & 2. */
if (output->length / hlen > 0xffffffff)
abort();
/* Step 2. */
l = (output->length + hlen - 1) / hlen;
utmp1 = /*output + dklen; */ malloc(hlen);
if (utmp1 == NULL)
return ENOMEM;
utmp2 = /*utmp1 + hlen; */ malloc(salt->length + 4 + hlen);
if (utmp2 == NULL) {
free(utmp1);
return ENOMEM;
}
/* Step 3. */
for (i = 1; i <= l; i++) {
krb5_error_code err;
char *out;
if (i == l)
out = utmp3;
else
out = output->data + (i-1) * hlen;
err = F(out, utmp1, utmp2, hash, hlen, pass, salt, count, i);
if (err) {
free(utmp1);
free(utmp2);
return err;
}
if (i == l)
memcpy(output->data + (i-1) * hlen, utmp3,
output->length - (i-1) * hlen);
}
free(utmp1);
free(utmp2);
return 0;
}
krb5_error_code
krb5int_pbkdf2_hmac(const struct krb5_hash_provider *hash,
const krb5_data *out, unsigned long count,
const krb5_data *pass, const krb5_data *salt)
{
krb5_keyblock keyblock;
char tmp[128];
krb5_data d;
krb5_crypto_iov iov;
krb5_error_code err;
assert(hash->hashsize <= sizeof(tmp));
if (pass->length > hash->blocksize) {
d = make_data(tmp, hash->hashsize);
iov.flags = KRB5_CRYPTO_TYPE_DATA;
iov.data = *pass;
err = hash->hash(&iov, 1, &d);
if (err)
return err;
keyblock.length = d.length;
keyblock.contents = (krb5_octet *) d.data;
} else {
keyblock.length = pass->length;
keyblock.contents = (krb5_octet *) pass->data;
}
keyblock.enctype = ENCTYPE_NULL;
err = pbkdf2(hash, &keyblock, salt, count, out);
return err;
}
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