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Make use of gcry_kdf_derive.

Browse source 
Factoring common code out is always a Good Thing.  Also added a
configure test to print an error if gcry_kdf_derive is missing in
Libgcrypt.
This commit is contained in:
Werner Koch 2011-03-10 18:39:34 +01:00
parent 35c731d889
commit b9bcc77d6c
5 changed files with 59 additions and 140 deletions
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96
g10/passphrase.c
View file

@ -1,6 +1,6 @@
/* passphrase.c - Get a passphrase
* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004,
* 2005, 2006, 2007, 2009 Free Software Foundation, Inc.
* 2005, 2006, 2007, 2009, 2011 Free Software Foundation, Inc.
*
* This file is part of GnuPG.
*
@ -101,81 +101,6 @@ encode_s2k_iterations (int iterations)
}
/* Hash a passphrase using the supplied s2k.
Always needs: dek->algo, s2k->mode, s2k->hash_algo. */
static void
hash_passphrase ( DEK *dek, char *pw, STRING2KEY *s2k)
{
gcry_md_hd_t md;
int pass, i;
int used = 0;
int pwlen = strlen(pw);
assert ( s2k->hash_algo );
dek->keylen = openpgp_cipher_get_algo_keylen (dek->algo);
if ( !(dek->keylen > 0 && dek->keylen <= DIM(dek->key)) )
BUG();
if (gcry_md_open (&md, s2k->hash_algo, 1))
BUG ();
for (pass=0; used < dek->keylen ; pass++ )
{
if ( pass )
{
gcry_md_reset (md);
for (i=0; i < pass; i++ ) /* Preset the hash context. */
gcry_md_putc (md, 0 );
}
if ( s2k->mode == 1 || s2k->mode == 3 )
{
int len2 = pwlen + 8;
ulong count = len2;
if ( s2k->mode == 3 )
{
count = S2K_DECODE_COUNT(s2k->count);
if ( count < len2 )
count = len2;
}
/* Fixme: To avoid DoS attacks by sending an sym-encrypted
packet with a very high S2K count, we should either cap
the iteration count or CPU seconds based timeout. */
/* A little bit complicated because we need a ulong for count. */
while ( count > len2 ) /* maybe iterated+salted */
{
gcry_md_write ( md, s2k->salt, 8 );
gcry_md_write ( md, pw, pwlen );
count -= len2;
}
if ( count < 8 )
gcry_md_write ( md, s2k->salt, count );
else
{
gcry_md_write ( md, s2k->salt, 8 );
count -= 8;
gcry_md_write ( md, pw, count );
}
}
else
gcry_md_write ( md, pw, pwlen );
gcry_md_final( md );
i = gcry_md_get_algo_dlen ( s2k->hash_algo );
if ( i > dek->keylen - used )
i = dek->keylen - used;
memcpy (dek->key+used, gcry_md_read (md, s2k->hash_algo), i);
used += i;
}
gcry_md_close(md);
}
int
have_static_passphrase()
{
@ -655,7 +580,24 @@ passphrase_to_dek_ext (u32 *keyid, int pubkey_algo,
if ( (!pw || !*pw) && (mode == 2 || mode == 4))
dek->keylen = 0;
else
hash_passphrase (dek, pw, s2k);
{
dek->keylen = openpgp_cipher_get_algo_keylen (dek->algo);
if (!(dek->keylen > 0 && dek->keylen <= DIM(dek->key)))
BUG ();
if (gcry_kdf_derive (pw, strlen (pw),
s2k->mode == 3? GCRY_KDF_ITERSALTED_S2K :
s2k->mode == 1? GCRY_KDF_SALTED_S2K :
/* */ GCRY_KDF_SIMPLE_S2K,
s2k->hash_algo, s2k->salt, 8,
S2K_DECODE_COUNT(s2k->count),
dek->keylen, dek->key))
{
xfree (pw);
xfree (dek);
write_status( STATUS_MISSING_PASSPHRASE );
return NULL;
}
}
if (s2k_cacheid)
memcpy (dek->s2k_cacheid, s2k_cacheid, sizeof dek->s2k_cacheid);
xfree(last_pw);