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sm,dirmngr: Support rsaPSS signature verification.
* sm/certcheck.c (hash_algo_from_buffer): New. (uint_from_buffer): New. (gpgsm_check_cert_sig): Handle PSS. * dirmngr/crlcache.c (hash_algo_from_buffer): New. (uint_from_buffer): New. (start_sig_check): Detect PSS and extract hash algo. New arg to return a PSS flag. (finish_sig_check): New arg use_pss. Extract PSS args and use them. (crl_parse_insert): Pass use_pss flag along. -- GnuPG-bug-id: 4538 Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch
parent
4d37cc72b8
commit
0626cc8fed
2 changed files with 308 additions and 61 deletions
192
sm/certcheck.c
192
sm/certcheck.c
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@ -1,5 +1,7 @@
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/* certcheck.c - check one certificate
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* Copyright (C) 2001, 2003, 2004 Free Software Foundation, Inc.
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* Copyright (C) 2001, 2003, 2004 Free Software Foundation, Inc.
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* Copyright (C) 2001-2019 Werner Koch
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* Copyright (C) 2015-2020 g10 Code GmbH
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*
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* This file is part of GnuPG.
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*
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@ -15,6 +17,7 @@
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <https://www.gnu.org/licenses/>.
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* SPDX-License-Identifier: GPL-3.0-or-later
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*/
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#include <config.h>
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@ -220,6 +223,53 @@ pk_algo_from_sexp (gcry_sexp_t pkey)
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}
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/* Return the hash algorithm's algo id from its name given in the
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* non-null termnated string in (buffer,buflen). Returns 0 on failure
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* or if the algo is not known. */
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static int
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hash_algo_from_buffer (const void *buffer, size_t buflen)
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{
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char *string;
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int algo;
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string = xtrymalloc (buflen + 1);
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if (!string)
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{
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log_error (_("out of core\n"));
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return 0;
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}
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memcpy (string, buffer, buflen);
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string[buflen] = 0;
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algo = gcry_md_map_name (string);
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if (!algo)
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log_error ("unknown digest algorithm '%s' used in certificate\n", string);
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xfree (string);
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return algo;
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}
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/* Return an unsigned integer from the non-null termnated string
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* (buffer,buflen). Returns 0 on failure. */
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static unsigned int
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uint_from_buffer (const void *buffer, size_t buflen)
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{
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char *string;
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unsigned int val;
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string = xtrymalloc (buflen + 1);
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if (!string)
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{
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log_error (_("out of core\n"));
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return 0;
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}
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memcpy (string, buffer, buflen);
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string[buflen] = 0;
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val = strtoul (string, NULL, 10);
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xfree (string);
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return val;
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}
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/* Check the signature on CERT using the ISSUER-CERT. This function
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does only test the cryptographic signature and nothing else. It is
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assumed that the ISSUER_CERT is valid. */
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@ -229,21 +279,76 @@ gpgsm_check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
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const char *algoid;
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gcry_md_hd_t md;
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int rc, algo;
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gcry_mpi_t frame;
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ksba_sexp_t p;
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size_t n;
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gcry_sexp_t s_sig, s_hash, s_pkey;
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gcry_sexp_t s_sig, s_data, s_pkey;
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int use_pss = 0;
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unsigned int saltlen;
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algo = gcry_md_map_name ( (algoid=ksba_cert_get_digest_algo (cert)));
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if (!algo)
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if (!algo && algoid && !strcmp (algoid, "1.2.840.113549.1.1.10"))
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use_pss = 1;
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else if (!algo)
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{
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log_error ("unknown hash algorithm '%s'\n", algoid? algoid:"?");
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log_error ("unknown digest algorithm '%s' used certificate\n",
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algoid? algoid:"?");
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if (algoid
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&& ( !strcmp (algoid, "1.2.840.113549.1.1.2")
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||!strcmp (algoid, "1.2.840.113549.2.2")))
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log_info (_("(this is the MD2 algorithm)\n"));
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return gpg_error (GPG_ERR_GENERAL);
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}
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/* The the signature from the certificate. */
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p = ksba_cert_get_sig_val (cert);
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n = gcry_sexp_canon_len (p, 0, NULL, NULL);
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if (!n)
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{
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log_error ("libksba did not return a proper S-Exp\n");
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ksba_free (p);
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return gpg_error (GPG_ERR_BUG);
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}
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rc = gcry_sexp_sscan ( &s_sig, NULL, (char*)p, n);
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ksba_free (p);
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if (rc)
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{
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log_error ("gcry_sexp_scan failed: %s\n", gpg_strerror (rc));
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return rc;
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}
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if (DBG_CRYPTO)
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gcry_log_debugsxp ("sigval", s_sig);
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if (use_pss)
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{
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/* Extract the hash algorithm and the salt length from the sigval. */
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gcry_buffer_t ioarray[2] = { {0}, {0} };
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rc = gcry_sexp_extract_param (s_sig, "sig-val",
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"&'hash-algo''salt-length'",
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ioarray+0, ioarray+1, NULL);
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if (rc)
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{
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gcry_sexp_release (s_sig);
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log_error ("extracting params from PSS failed: %s\n",
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gpg_strerror (rc));
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return rc;
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}
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algo = hash_algo_from_buffer (ioarray[0].data, ioarray[0].len);
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saltlen = uint_from_buffer (ioarray[1].data, ioarray[1].len);
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xfree (ioarray[0].data);
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xfree (ioarray[1].data);
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if (saltlen < 20)
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{
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log_error ("length of PSS salt too short\n");
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return gpg_error (GPG_ERR_DIGEST_ALGO);
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}
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if (!algo)
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return gpg_error (GPG_ERR_DIGEST_ALGO);
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/* log_debug ("PSS hash=%d saltlen=%u\n", algo, saltlen); */
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}
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/* Hash the to-be-signed parts of the certificate. */
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rc = gcry_md_open (&md, algo, 0);
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if (rc)
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{
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@ -262,33 +367,7 @@ gpgsm_check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
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}
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gcry_md_final (md);
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p = ksba_cert_get_sig_val (cert);
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n = gcry_sexp_canon_len (p, 0, NULL, NULL);
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if (!n)
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{
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log_error ("libksba did not return a proper S-Exp\n");
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gcry_md_close (md);
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ksba_free (p);
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return gpg_error (GPG_ERR_BUG);
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}
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if (DBG_CRYPTO)
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{
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int j;
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log_debug ("signature value:");
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for (j=0; j < n; j++)
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log_printf (" %02X", p[j]);
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log_printf ("\n");
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}
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rc = gcry_sexp_sscan ( &s_sig, NULL, (char*)p, n);
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ksba_free (p);
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if (rc)
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{
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log_error ("gcry_sexp_scan failed: %s\n", gpg_strerror (rc));
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gcry_md_close (md);
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return rc;
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}
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/* Get the public key from the certificate. */
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p = ksba_cert_get_public_key (issuer_cert);
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n = gcry_sexp_canon_len (p, 0, NULL, NULL);
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if (!n)
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@ -308,29 +387,50 @@ gpgsm_check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
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gcry_sexp_release (s_sig);
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return rc;
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}
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if (DBG_CRYPTO)
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gcry_log_debugsxp ("pubkey:", s_pkey);
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rc = do_encode_md (md, algo, pk_algo_from_sexp (s_pkey),
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gcry_pk_get_nbits (s_pkey), s_pkey, &frame);
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if (rc)
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if (use_pss)
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{
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gcry_md_close (md);
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gcry_sexp_release (s_sig);
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gcry_sexp_release (s_pkey);
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return rc;
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rc = gcry_sexp_build (&s_data, NULL,
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"(data (flags pss)"
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"(hash %s %b)"
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"(salt-length %u))",
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hash_algo_to_string (algo),
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(int)gcry_md_get_algo_dlen (algo),
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gcry_md_read (md, algo),
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saltlen);
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if (rc)
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BUG ();
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}
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else
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{
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/* RSA or DAS: Prepare the hash for verification. */
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gcry_mpi_t frame;
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/* put hash into the S-Exp s_hash */
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if ( gcry_sexp_build (&s_hash, NULL, "%m", frame) )
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BUG ();
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gcry_mpi_release (frame);
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rc = do_encode_md (md, algo, pk_algo_from_sexp (s_pkey),
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gcry_pk_get_nbits (s_pkey), s_pkey, &frame);
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if (rc)
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{
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gcry_md_close (md);
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gcry_sexp_release (s_sig);
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gcry_sexp_release (s_pkey);
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return rc;
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}
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if ( gcry_sexp_build (&s_data, NULL, "%m", frame) )
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BUG ();
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gcry_mpi_release (frame);
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}
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if (DBG_CRYPTO)
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gcry_log_debugsxp ("data:", s_data);
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rc = gcry_pk_verify (s_sig, s_hash, s_pkey);
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/* Verify. */
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rc = gcry_pk_verify (s_sig, s_data, s_pkey);
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if (DBG_X509)
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log_debug ("gcry_pk_verify: %s\n", gpg_strerror (rc));
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gcry_md_close (md);
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gcry_sexp_release (s_sig);
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gcry_sexp_release (s_hash);
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gcry_sexp_release (s_data);
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gcry_sexp_release (s_pkey);
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return rc;
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}
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