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sm: Support import and verification of EdDSA certificates.

Browse Source 
* sm/certdump.c (gpgsm_get_serial): New.
* sm/certcheck.c (gpgsm_check_cert_sig): Support EdDSA signatures.
--

Note that this does not work with the self-signed RFC-8410 sample
certificate; see the code for comments.

The Ed488 case has not been tested due to a lack of support in
Libgcrypt.

Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch 2020-05-13 21:21:24 +02:00
parent f44d395bdf
commit b1694987bb
No known key found for this signature in database
GPG Key ID: E3FDFF218E45B72B
3 changed files with 144 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

139
sm/certcheck.c
View File

@ -35,6 +35,7 @@
#include "keydb.h"
#include "../common/i18n.h"
#include "../common/membuf.h"
/* Return the number of bits of the Q parameter from the DSA key
@ -348,20 +349,27 @@ int
gpgsm_check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
{
const char *algoid;
gcry_md_hd_t md;
gcry_md_hd_t md = NULL;
void *certder = NULL;
size_t certderlen;
int rc, algo;
ksba_sexp_t p;
size_t n;
gcry_sexp_t s_sig, s_data, s_pkey;
int use_pss = 0;
int use_eddsa = 0;
unsigned int saltlen;
algo = gcry_md_map_name ( (algoid=ksba_cert_get_digest_algo (cert)));
if (!algo && algoid && !strcmp (algoid, "1.2.840.113549.1.1.10"))
use_pss = 1;
else if (algoid && !strcmp (algoid, "1.3.101.112"))
use_eddsa = 1;
else if (algoid && !strcmp (algoid, "1.3.101.113"))
use_eddsa = 2;
else if (!algo)
{
log_error ("unknown digest algorithm '%s' used certificate\n",
log_error ("unknown digest algorithm '%s' used in certificate\n",
algoid? algoid:"?");
if (algoid
&& ( !strcmp (algoid, "1.2.840.113549.1.1.2")
@ -400,24 +408,50 @@ gpgsm_check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
}
/* Hash the to-be-signed parts of the certificate. */
rc = gcry_md_open (&md, algo, 0);
if (rc)
/* Hash the to-be-signed parts of the certificate or but them into a
* buffer for the EdDSA algorithms. */
if (use_eddsa)
{
log_error ("md_open failed: %s\n", gpg_strerror (rc));
return rc;
}
if (DBG_HASHING)
gcry_md_debug (md, "hash.cert");
membuf_t mb;
rc = ksba_cert_hash (cert, 1, HASH_FNC, md);
if (rc)
{
log_error ("ksba_cert_hash failed: %s\n", gpg_strerror (rc));
gcry_md_close (md);
return rc;
init_membuf (&mb, 2048);
rc = ksba_cert_hash (cert, 1,
(void (*)(void *, const void*,size_t))put_membuf,
&mb);
if (rc)
{
log_error ("ksba_cert_hash failed: %s\n", gpg_strerror (rc));
xfree (get_membuf (&mb, NULL));
return rc;
}
certder = get_membuf (&mb, &certderlen);
if (!certder)
{
rc = gpg_error_from_syserror ();
log_error ("getting tbsCertificate failed: %s\n", gpg_strerror (rc));
return rc;
}
}
else
{
rc = gcry_md_open (&md, algo, 0);
if (rc)
{
log_error ("md_open failed: %s\n", gpg_strerror (rc));
return rc;
}
if (DBG_HASHING)
gcry_md_debug (md, "hash.cert");
rc = ksba_cert_hash (cert, 1, HASH_FNC, md);
if (rc)
{
log_error ("ksba_cert_hash failed: %s\n", gpg_strerror (rc));
gcry_md_close (md);
return rc;
}
gcry_md_final (md);
}
gcry_md_final (md);
/* Get the public key from the certificate. */
p = ksba_cert_get_public_key (issuer_cert);
@ -428,6 +462,7 @@ gpgsm_check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
gcry_md_close (md);
ksba_free (p);
gcry_sexp_release (s_sig);
xfree (certder);
return gpg_error (GPG_ERR_BUG);
}
rc = gcry_sexp_sscan ( &s_pkey, NULL, (char*)p, n);
@ -437,6 +472,7 @@ gpgsm_check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
log_error ("gcry_sexp_scan failed: %s\n", gpg_strerror (rc));
gcry_md_close (md);
gcry_sexp_release (s_sig);
xfree (certder);
return rc;
}
if (DBG_CRYPTO)
@ -455,6 +491,21 @@ gpgsm_check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
if (rc)
BUG ();
}
else if (use_eddsa)
{
rc = gcry_sexp_build (&s_data, NULL,
"(data(flags eddsa)(hash-algo %s)(value %b))",
use_eddsa == 1? "sha512":"shake256",
(int)certderlen, certder);
xfree (certder);
certder = NULL;
if (rc)
{
log_error ("building data for eddsa failed: %s\n", gpg_strerror (rc));
gcry_sexp_release (s_sig);
return rc;
}
}
else
{
/* RSA or DSA: Prepare the hash for verification. */
@ -479,7 +530,59 @@ gpgsm_check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
/* Verify. */
rc = gcry_pk_verify (s_sig, s_data, s_pkey);
if (DBG_X509)
log_debug ("gcry_pk_verify: %s\n", gpg_strerror (rc));
log_debug ("gcry_pk_verify: %s\n", gpg_strerror (rc));
if (use_eddsa && (gpg_err_code (rc) == GPG_ERR_INTERNAL
|| gpg_err_code (rc) == GPG_ERR_INV_CURVE))
{
/* Let's assume that this is a certificate for an ECDH key
* signed using EdDSA. This won't work. We should have located
* the public key using subjectKeyIdentifier (SKI) to not run
* into this problem. However, we don't do this for self-signed
* certificates and we don't have a way to search for arbitrary
* keys based on the SKI. Note: The sample certificate from
* RFC-8410 uses a SHA-1 hash of the public key for the SKI; so
* we are not able to verify it.
*/
ksba_sexp_t ski;
const unsigned char *skider;
size_t skiderlen;
if (DBG_X509)
log_debug ("retrying using the ski\n");
if (!ksba_cert_get_subj_key_id (issuer_cert, NULL, &ski))
{
skider = gpgsm_get_serial (ski, &skiderlen);
if (!skider)
;
else if (skiderlen == (use_eddsa==1? 32:57))
{
/* Here we assume that the SKI is actually the public key. */
gcry_sexp_release (s_pkey);
rc = gcry_sexp_build (&s_pkey, NULL,
"(public-key(ecc(curve%s)(q%b)))",
use_eddsa==1? "1.3.101.112":"1.3.101.113",
(int)skiderlen, skider);
if (rc)
log_error ("building pubkey from SKI failed: %s\n",
gpg_strerror (rc));
else
rc = gcry_pk_verify (s_sig, s_data, s_pkey);
if (DBG_X509)
log_debug ("gcry_pk_verify: %s\n", gpg_strerror (rc));
}
else if (skiderlen == 20)
{
log_printhex (skider, skiderlen, "ski might be the SHA-1:");
}
else
{
if (DBG_X509)
log_debug(skider, skiderlen, "ski is:");
}
ksba_free (ski);
}
}
gcry_md_close (md);
gcry_sexp_release (s_sig);
gcry_sexp_release (s_data);

22
sm/certdump.c
View File

@ -48,6 +48,28 @@ struct dn_array_s {
};
/* Get the first first element from the s-expression SN and return a
* pointer to it. Stores the length at R_LENGTH. Returns NULL for no
* value or an invalid expression. */
const void *
gpgsm_get_serial (ksba_const_sexp_t sn, size_t *r_length)
{
const char *p = (const char *)sn;
unsigned long n;
char *endp;
if (!p || *p != '(')
return NULL;
p++;
n = strtoul (p, &endp, 10);
p = endp;
if (*p++ != ':')
return NULL;
*r_length = n;
return p;
}
/* Print the first element of an S-Expression. */
void
gpgsm_print_serial (estream_t fp, ksba_const_sexp_t sn)

1
sm/gpgsm.h
View File

@ -297,6 +297,7 @@ char *gpgsm_get_certid (ksba_cert_t cert);
/*-- certdump.c --*/
const void *gpgsm_get_serial (ksba_const_sexp_t sn, size_t *r_length);
void gpgsm_print_serial (estream_t fp, ksba_const_sexp_t p);
void gpgsm_print_time (estream_t fp, ksba_isotime_t t);
void gpgsm_print_name2 (FILE *fp, const char *string, int translate);