diff options
Diffstat (limited to 'sm/certcheck.c')
| -rw-r--r-- | sm/certcheck.c | 364 |
1 files changed, 364 insertions, 0 deletions
diff --git a/sm/certcheck.c b/sm/certcheck.c new file mode 100644 index 000000000..732356149 --- /dev/null +++ b/sm/certcheck.c @@ -0,0 +1,364 @@ +/* certcheck.c - check one certificate + * Copyright (C) 2001, 2003, 2004 Free Software Foundation, Inc. + * + * This file is part of GnuPG. + * + * GnuPG is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * GnuPG is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, + * USA. + */ + +#include <config.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <errno.h> +#include <unistd.h> +#include <time.h> +#include <assert.h> + +#include "gpgsm.h" +#include <gcrypt.h> +#include <ksba.h> + +#include "keydb.h" +#include "i18n.h" + + +static int +do_encode_md (gcry_md_hd_t md, int algo, int pkalgo, unsigned int nbits, + gcry_mpi_t *r_val) +{ + int n; + size_t nframe; + unsigned char *frame; + + if (pkalgo == GCRY_PK_DSA) + { + nframe = gcry_md_get_algo_dlen (algo); + if (nframe != 20) + { + log_error (_("DSA requires the use of a 160 bit hash algorithm\n")); + return gpg_error (GPG_ERR_INTERNAL); + } + frame = xtrymalloc (nframe); + if (!frame) + return OUT_OF_CORE (errno); + memcpy (frame, gcry_md_read (md, algo), nframe); + n = nframe; + } + else + { + int i; + unsigned char asn[100]; + size_t asnlen; + size_t len; + + nframe = (nbits+7) / 8; + + asnlen = DIM(asn); + if (gcry_md_algo_info (algo, GCRYCTL_GET_ASNOID, asn, &asnlen)) + { + log_error ("no object identifier for algo %d\n", algo); + return gpg_error (GPG_ERR_INTERNAL); + } + + len = gcry_md_get_algo_dlen (algo); + + if ( len + asnlen + 4 > nframe ) + { + log_error ("can't encode a %d bit MD into a %d bits frame\n", + (int)(len*8), (int)nbits); + return gpg_error (GPG_ERR_INTERNAL); + } + + /* We encode the MD in this way: + * + * 0 A PAD(n bytes) 0 ASN(asnlen bytes) MD(len bytes) + * + * PAD consists of FF bytes. + */ + frame = xtrymalloc (nframe); + if (!frame) + return OUT_OF_CORE (errno); + n = 0; + frame[n++] = 0; + frame[n++] = 1; /* block type */ + i = nframe - len - asnlen -3 ; + assert ( i > 1 ); + memset ( frame+n, 0xff, i ); n += i; + frame[n++] = 0; + memcpy ( frame+n, asn, asnlen ); n += asnlen; + memcpy ( frame+n, gcry_md_read(md, algo), len ); n += len; + assert ( n == nframe ); + } + if (DBG_CRYPTO) + { + int j; + log_debug ("encoded hash:"); + for (j=0; j < nframe; j++) + log_printf (" %02X", frame[j]); + log_printf ("\n"); + } + + gcry_mpi_scan (r_val, GCRYMPI_FMT_USG, frame, n, &nframe); + xfree (frame); + return 0; +} + +/* Return the public key algorithm id from the S-expression PKEY. + FIXME: libgcrypt should provide such a function. Note that this + implementation uses the names as used by libksba. */ +static int +pk_algo_from_sexp (gcry_sexp_t pkey) +{ + gcry_sexp_t l1, l2; + const char *name; + size_t n; + int algo; + + l1 = gcry_sexp_find_token (pkey, "public-key", 0); + if (!l1) + return 0; /* Not found. */ + l2 = gcry_sexp_cadr (l1); + gcry_sexp_release (l1); + + name = gcry_sexp_nth_data (l2, 0, &n); + if (!name) + algo = 0; /* Not found. */ + else if (n==3 && !memcmp (name, "rsa", 3)) + algo = GCRY_PK_RSA; + else if (n==3 && !memcmp (name, "dsa", 3)) + algo = GCRY_PK_DSA; + else if (n==13 && !memcmp (name, "ambiguous-rsa", 13)) + algo = GCRY_PK_RSA; + else + algo = 0; + gcry_sexp_release (l2); + return algo; +} + + +/* + 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 +gpgsm_check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert) +{ + const char *algoid; + gcry_md_hd_t md; + int rc, algo; + gcry_mpi_t frame; + ksba_sexp_t p; + size_t n; + gcry_sexp_t s_sig, s_hash, s_pkey; + + algo = gcry_md_map_name ( (algoid=ksba_cert_get_digest_algo (cert))); + if (!algo) + { + log_error ("unknown hash algorithm `%s'\n", algoid? algoid:"?"); + if (algoid + && ( !strcmp (algoid, "1.2.840.113549.1.1.2") + ||!strcmp (algoid, "1.2.840.113549.2.2"))) + log_info (_("(this is the MD2 algorithm)\n")); + return gpg_error (GPG_ERR_GENERAL); + } + 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_start_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); + + p = ksba_cert_get_sig_val (cert); + n = gcry_sexp_canon_len (p, 0, NULL, NULL); + if (!n) + { + log_error ("libksba did not return a proper S-Exp\n"); + gcry_md_close (md); + ksba_free (p); + return gpg_error (GPG_ERR_BUG); + } + if (DBG_CRYPTO) + { + int j; + log_debug ("signature value:"); + for (j=0; j < n; j++) + log_printf (" %02X", p[j]); + log_printf ("\n"); + } + + rc = gcry_sexp_sscan ( &s_sig, NULL, (char*)p, n); + ksba_free (p); + if (rc) + { + log_error ("gcry_sexp_scan failed: %s\n", gpg_strerror (rc)); + gcry_md_close (md); + return rc; + } + + p = ksba_cert_get_public_key (issuer_cert); + n = gcry_sexp_canon_len (p, 0, NULL, NULL); + if (!n) + { + log_error ("libksba did not return a proper S-Exp\n"); + gcry_md_close (md); + ksba_free (p); + gcry_sexp_release (s_sig); + return gpg_error (GPG_ERR_BUG); + } + rc = gcry_sexp_sscan ( &s_pkey, NULL, (char*)p, n); + ksba_free (p); + if (rc) + { + log_error ("gcry_sexp_scan failed: %s\n", gpg_strerror (rc)); + gcry_md_close (md); + gcry_sexp_release (s_sig); + return rc; + } + + rc = do_encode_md (md, algo, pk_algo_from_sexp (s_pkey), + gcry_pk_get_nbits (s_pkey), &frame); + if (rc) + { + gcry_md_close (md); + gcry_sexp_release (s_sig); + gcry_sexp_release (s_pkey); + return rc; + } + + /* put hash into the S-Exp s_hash */ + if ( gcry_sexp_build (&s_hash, NULL, "%m", frame) ) + BUG (); + gcry_mpi_release (frame); + + + rc = gcry_pk_verify (s_sig, s_hash, s_pkey); + if (DBG_X509) + log_debug ("gcry_pk_verify: %s\n", gpg_strerror (rc)); + gcry_md_close (md); + gcry_sexp_release (s_sig); + gcry_sexp_release (s_hash); + gcry_sexp_release (s_pkey); + return rc; +} + + + +int +gpgsm_check_cms_signature (ksba_cert_t cert, ksba_const_sexp_t sigval, + gcry_md_hd_t md, int algo) +{ + int rc; + ksba_sexp_t p; + gcry_mpi_t frame; + gcry_sexp_t s_sig, s_hash, s_pkey; + size_t n; + + n = gcry_sexp_canon_len (sigval, 0, NULL, NULL); + if (!n) + { + log_error ("libksba did not return a proper S-Exp\n"); + return gpg_error (GPG_ERR_BUG); + } + rc = gcry_sexp_sscan (&s_sig, NULL, (char*)sigval, n); + if (rc) + { + log_error ("gcry_sexp_scan failed: %s\n", gpg_strerror (rc)); + return rc; + } + + p = ksba_cert_get_public_key (cert); + n = gcry_sexp_canon_len (p, 0, NULL, NULL); + if (!n) + { + log_error ("libksba did not return a proper S-Exp\n"); + ksba_free (p); + gcry_sexp_release (s_sig); + return gpg_error (GPG_ERR_BUG); + } + if (DBG_CRYPTO) + log_printhex ("public key: ", p, n); + + rc = gcry_sexp_sscan ( &s_pkey, NULL, (char*)p, n); + ksba_free (p); + if (rc) + { + log_error ("gcry_sexp_scan failed: %s\n", gpg_strerror (rc)); + gcry_sexp_release (s_sig); + return rc; + } + + + rc = do_encode_md (md, algo, pk_algo_from_sexp (s_pkey), + gcry_pk_get_nbits (s_pkey), &frame); + if (rc) + { + gcry_sexp_release (s_sig); + gcry_sexp_release (s_pkey); + return rc; + } + /* put hash into the S-Exp s_hash */ + if ( gcry_sexp_build (&s_hash, NULL, "%m", frame) ) + BUG (); + gcry_mpi_release (frame); + + rc = gcry_pk_verify (s_sig, s_hash, s_pkey); + if (DBG_X509) + log_debug ("gcry_pk_verify: %s\n", gpg_strerror (rc)); + gcry_sexp_release (s_sig); + gcry_sexp_release (s_hash); + gcry_sexp_release (s_pkey); + return rc; +} + + + +int +gpgsm_create_cms_signature (ctrl_t ctrl, ksba_cert_t cert, + gcry_md_hd_t md, int mdalgo, + unsigned char **r_sigval) +{ + int rc; + char *grip, *desc; + size_t siglen; + + grip = gpgsm_get_keygrip_hexstring (cert); + if (!grip) + return gpg_error (GPG_ERR_BAD_CERT); + + desc = gpgsm_format_keydesc (cert); + + rc = gpgsm_agent_pksign (ctrl, grip, desc, gcry_md_read(md, mdalgo), + gcry_md_get_algo_dlen (mdalgo), mdalgo, + r_sigval, &siglen); + xfree (desc); + xfree (grip); + return rc; +} + + + |