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* certcheck.c (do_encode_md): Add arg PKEY. Add support for DSA2

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and all ECDSA sizes.
        (get_dsa_qbits): New.
        (pk_algo_from_sexp): A key will never contain ecdsa as algorithm,
        so remove that.
This commit is contained in:
Werner Koch 2007-04-20 10:54:46 +00:00
parent 4c48abebfe
commit e3a8e6b727
2 changed files with 82 additions and 12 deletions
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8
sm/ChangeLog
View File

@ -1,3 +1,11 @@
2007-04-19 Werner Koch <wk@g10code.com>
* certcheck.c (do_encode_md): Add arg PKEY. Add support for DSA2
and all ECDSA sizes.
(get_dsa_qbits): New.
(pk_algo_from_sexp): A key will never contain ecdsa as algorithm,
so remove that.
2007-04-18 Werner Koch <wk@g10code.com>
* certcheck.c (do_encode_md): Support 160 bit ECDSA.

82
sm/certcheck.c
View File

@ -35,10 +35,38 @@
#include "keydb.h"
#include "i18n.h"
/* Return the number of bits of the Q parameter from the DSA key
KEY. */
static unsigned int
get_dsa_qbits (gcry_sexp_t key)
{
gcry_sexp_t l1, l2;
gcry_mpi_t q;
unsigned int nbits;
l1 = gcry_sexp_find_token (key, "public-key", 0);
if (!l1)
return 0; /* Does not contain a key object. */
l2 = gcry_sexp_cadr (l1);
gcry_sexp_release (l1);
l1 = gcry_sexp_find_token (l2, "q", 1);
gcry_sexp_release (l2);
if (!l1)
return 0; /* Invalid object. */
q = gcry_sexp_nth_mpi (l1, 1, GCRYMPI_FMT_USG);
gcry_sexp_release (l1);
if (!q)
return 0; /* Missing value. */
nbits = gcry_mpi_get_nbits (q);
gcry_mpi_release (q);
return nbits;
}
static int
do_encode_md (gcry_md_hd_t md, int algo, int pkalgo, unsigned int nbits,
gcry_mpi_t *r_val)
gcry_sexp_t pkey, gcry_mpi_t *r_val)
{
int n;
size_t nframe;
@ -46,17 +74,54 @@ do_encode_md (gcry_md_hd_t md, int algo, int pkalgo, unsigned int nbits,
if (pkalgo == GCRY_PK_DSA || pkalgo == GCRY_PK_ECDSA)
{
nframe = gcry_md_get_algo_dlen (algo);
if (nframe != 20)
unsigned int qbits;
if ( pkalgo == GCRY_PK_ECDSA )
qbits = gcry_pk_get_nbits (pkey);
else
qbits = get_dsa_qbits (pkey);
if ( (qbits%8) )
{
log_error (_("DSA requires the use of a 160 bit hash algorithm\n"));
log_error(_("DSA requires the hash length to be a"
" multiple of 8 bits\n"));
return gpg_error (GPG_ERR_INTERNAL);
}
/* Don't allow any Q smaller than 160 bits. We don't want
someone to issue signatures from a key with a 16-bit Q or
something like that, which would look correct but allow
trivial forgeries. Yes, I know this rules out using MD5 with
DSA. ;) */
if (qbits < 160)
{
log_error (_("%s key uses an unsafe (%u bit) hash\n"),
gcry_pk_algo_name (pkalgo), qbits);
return gpg_error (GPG_ERR_INTERNAL);
}
/* Check if we're too short. Too long is safe as we'll
automatically left-truncate. */
nframe = gcry_md_get_algo_dlen (algo);
if (nframe < qbits/8)
{
log_error (_("a %u bit hash is not valid for a %u bit %s key\n"),
(unsigned int)nframe*8,
gcry_pk_get_nbits (pkey),
gcry_pk_algo_name (pkalgo));
/* FIXME: we need to check the requirements for ECDSA. */
if (nframe < 20 || pkalgo == GCRY_PK_DSA )
return gpg_error (GPG_ERR_INTERNAL);
}
frame = xtrymalloc (nframe);
if (!frame)
return out_of_core ();
memcpy (frame, gcry_md_read (md, algo), nframe);
n = nframe;
/* Truncate. */
if (n > qbits/8)
n = qbits/8;
}
else
{
@ -143,8 +208,6 @@ pk_algo_from_sexp (gcry_sexp_t pkey)
algo = GCRY_PK_RSA;
else if (n==3 && !memcmp (name, "dsa", 3))
algo = GCRY_PK_DSA;
else if (n==5 && !memcmp (name, "ecdsa", 5))
algo = GCRY_PK_ECDSA;
/* Because this function is called only for verification we can
assume that ECC actually means ECDSA. */
else if (n==3 && !memcmp (name, "ecc", 3))
@ -158,8 +221,7 @@ pk_algo_from_sexp (gcry_sexp_t pkey)
}
/*
Check the signature on CERT using the ISSUER-CERT. This function
/* Check the signature on CERT using the ISSUER-CERT. This function
does only test the cryptographic signature and nothing else. It is
assumed that the ISSUER_CERT is valid. */
int
@ -249,7 +311,7 @@ gpgsm_check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
}
rc = do_encode_md (md, algo, pk_algo_from_sexp (s_pkey),
gcry_pk_get_nbits (s_pkey), &frame);
gcry_pk_get_nbits (s_pkey), s_pkey, &frame);
if (rc)
{
gcry_md_close (md);
@ -322,7 +384,7 @@ gpgsm_check_cms_signature (ksba_cert_t cert, ksba_const_sexp_t sigval,
rc = do_encode_md (md, algo, pk_algo_from_sexp (s_pkey),
gcry_pk_get_nbits (s_pkey), &frame);
gcry_pk_get_nbits (s_pkey), s_pkey, &frame);
if (rc)
{
gcry_sexp_release (s_sig);