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gnupg/sm/verify.c
Werner Koch 4a36adaa64
sm: Exclude rsaPSS from de-vs compliance mode. 
* common/compliance.h (PK_ALGO_FLAG_RSAPSS): New.
* common/compliance.c (gnupg_pk_is_compliant): Add arg alog_flags and
test rsaPSS.  Adjust all callers.
* common/util.c (pubkey_algo_to_string): New.
(gnupg_pk_is_allowed): Ditto.
* sm/misc.c (gpgsm_ksba_cms_get_sig_val): New wrapper function.
(gpgsm_get_hash_algo_from_sigval): New.
* sm/certcheck.c (gpgsm_check_cms_signature): Change type of sigval
arg.  Add arg pkalgoflags.  Use the PK_ALGO_FLAG_RSAPSS.
* sm/verify.c (gpgsm_verify): Use the new wrapper and new fucntion to
also get the algo flags.  Pass algo flags along.  Change some of the
info output to be more like current master.
--
Signed-off-by: Werner Koch <wk@gnupg.org>

This backport from master
commit 969abcf40cdfc65f3ee859c5e62889e1a8ccde91
also includes some changes taken from
commit a759fa963a42e0652134130029217270b6d5d00b
(sm: Improve readability of the data verification output.)

Signed-off-by: Werner Koch <wk@gnupg.org>
2020-07-03 17:08:58 +02:00

724 lines
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/* verify.c - Verify a messages signature
* Copyright (C) 2001, 2002, 2003, 2007,
* 2010 Free Software Foundation, Inc.
* Copyright (C) 2001-2019 Werner Koch
* Copyright (C) 2015-2020 g10 Code GmbH
*
* 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 3 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, see <https://www.gnu.org/licenses/>.
* SPDX-License-Identifier: GPL-3.0-or-later
*/
#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 "../common/i18n.h"
#include "../common/compliance.h"
static char *
strtimestamp_r (ksba_isotime_t atime)
{
char *buffer = xmalloc (15);
if (!atime || !*atime)
strcpy (buffer, "none");
else
sprintf (buffer, "%.4s-%.2s-%.2s", atime, atime+4, atime+6);
return buffer;
}
/* Hash the data for a detached signature. Returns 0 on success. */
static gpg_error_t
hash_data (int fd, gcry_md_hd_t md)
{
gpg_error_t err = 0;
estream_t fp;
char buffer[4096];
int nread;
fp = es_fdopen_nc (fd, "rb");
if (!fp)
{
err = gpg_error_from_syserror ();
log_error ("fdopen(%d) failed: %s\n", fd, gpg_strerror (err));
return err;
}
do
{
nread = es_fread (buffer, 1, DIM(buffer), fp);
gcry_md_write (md, buffer, nread);
}
while (nread);
if (es_ferror (fp))
{
err = gpg_error_from_syserror ();
log_error ("read error on fd %d: %s\n", fd, gpg_strerror (err));
}
es_fclose (fp);
return err;
}
/* Perform a verify operation. To verify detached signatures, DATA_FD
must be different than -1. With OUT_FP given and a non-detached
signature, the signed material is written to that stream. */
int
gpgsm_verify (ctrl_t ctrl, int in_fd, int data_fd, estream_t out_fp)
{
int i, rc;
gnupg_ksba_io_t b64reader = NULL;
gnupg_ksba_io_t b64writer = NULL;
ksba_reader_t reader;
ksba_writer_t writer = NULL;
ksba_cms_t cms = NULL;
ksba_stop_reason_t stopreason;
ksba_cert_t cert;
KEYDB_HANDLE kh;
gcry_md_hd_t data_md = NULL;
int signer;
const char *algoid;
int algo;
int is_detached;
estream_t in_fp = NULL;
char *p;
audit_set_type (ctrl->audit, AUDIT_TYPE_VERIFY);
kh = keydb_new ();
if (!kh)
{
log_error (_("failed to allocate keyDB handle\n"));
rc = gpg_error (GPG_ERR_GENERAL);
goto leave;
}
in_fp = es_fdopen_nc (in_fd, "rb");
if (!in_fp)
{
rc = gpg_error_from_syserror ();
log_error ("fdopen() failed: %s\n", strerror (errno));
goto leave;
}
rc = gnupg_ksba_create_reader
(&b64reader, ((ctrl->is_pem? GNUPG_KSBA_IO_PEM : 0)
| (ctrl->is_base64? GNUPG_KSBA_IO_BASE64 : 0)
| (ctrl->autodetect_encoding? GNUPG_KSBA_IO_AUTODETECT : 0)),
in_fp, &reader);
if (rc)
{
log_error ("can't create reader: %s\n", gpg_strerror (rc));
goto leave;
}
if (out_fp)
{
rc = gnupg_ksba_create_writer
(&b64writer, ((ctrl->create_pem? GNUPG_KSBA_IO_PEM : 0)
| (ctrl->create_base64? GNUPG_KSBA_IO_BASE64 : 0)),
ctrl->pem_name, out_fp, &writer);
if (rc)
{
log_error ("can't create writer: %s\n", gpg_strerror (rc));
goto leave;
}
}
rc = ksba_cms_new (&cms);
if (rc)
goto leave;
rc = ksba_cms_set_reader_writer (cms, reader, writer);
if (rc)
{
log_error ("ksba_cms_set_reader_writer failed: %s\n",
gpg_strerror (rc));
goto leave;
}
rc = gcry_md_open (&data_md, 0, 0);
if (rc)
{
log_error ("md_open failed: %s\n", gpg_strerror (rc));
goto leave;
}
if (DBG_HASHING)
gcry_md_debug (data_md, "vrfy.data");
audit_log (ctrl->audit, AUDIT_SETUP_READY);
is_detached = 0;
do
{
rc = ksba_cms_parse (cms, &stopreason);
if (rc)
{
log_error ("ksba_cms_parse failed: %s\n", gpg_strerror (rc));
goto leave;
}
if (stopreason == KSBA_SR_NEED_HASH)
{
is_detached = 1;
audit_log (ctrl->audit, AUDIT_DETACHED_SIGNATURE);
if (opt.verbose)
log_info ("detached signature\n");
}
if (stopreason == KSBA_SR_NEED_HASH
|| stopreason == KSBA_SR_BEGIN_DATA)
{
audit_log (ctrl->audit, AUDIT_GOT_DATA);
/* We are now able to enable the hash algorithms */
for (i=0; (algoid=ksba_cms_get_digest_algo_list (cms, i)); i++)
{
algo = gcry_md_map_name (algoid);
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"));
audit_log_s (ctrl->audit, AUDIT_BAD_DATA_HASH_ALGO, algoid);
}
else
{
if (DBG_X509)
log_debug ("enabling hash algorithm %d (%s)\n",
algo, algoid? algoid:"");
gcry_md_enable (data_md, algo);
audit_log_i (ctrl->audit, AUDIT_DATA_HASH_ALGO, algo);
}
}
if (opt.extra_digest_algo)
{
if (DBG_X509)
log_debug ("enabling extra hash algorithm %d\n",
opt.extra_digest_algo);
gcry_md_enable (data_md, opt.extra_digest_algo);
audit_log_i (ctrl->audit, AUDIT_DATA_HASH_ALGO,
opt.extra_digest_algo);
}
if (is_detached)
{
if (data_fd == -1)
{
log_info ("detached signature w/o data "
"- assuming certs-only\n");
audit_log (ctrl->audit, AUDIT_CERT_ONLY_SIG);
}
else
audit_log_ok (ctrl->audit, AUDIT_DATA_HASHING,
hash_data (data_fd, data_md));
}
else
{
ksba_cms_set_hash_function (cms, HASH_FNC, data_md);
}
}
else if (stopreason == KSBA_SR_END_DATA)
{ /* The data bas been hashed */
audit_log_ok (ctrl->audit, AUDIT_DATA_HASHING, 0);
}
}
while (stopreason != KSBA_SR_READY);
if (b64writer)
{
rc = gnupg_ksba_finish_writer (b64writer);
if (rc)
{
log_error ("write failed: %s\n", gpg_strerror (rc));
audit_log_ok (ctrl->audit, AUDIT_WRITE_ERROR, rc);
goto leave;
}
}
if (data_fd != -1 && !is_detached)
{
log_error ("data given for a non-detached signature\n");
rc = gpg_error (GPG_ERR_CONFLICT);
audit_log (ctrl->audit, AUDIT_USAGE_ERROR);
goto leave;
}
for (i=0; (cert=ksba_cms_get_cert (cms, i)); i++)
{
/* Fixme: it might be better to check the validity of the
certificate first before entering it into the DB. This way
we would avoid cluttering the DB with invalid
certificates. */
audit_log_cert (ctrl->audit, AUDIT_SAVE_CERT, cert,
keydb_store_cert (ctrl, cert, 0, NULL));
ksba_cert_release (cert);
}
cert = NULL;
for (signer=0; ; signer++)
{
char *issuer = NULL;
gcry_sexp_t sigval = NULL;
ksba_isotime_t sigtime, keyexptime;
ksba_sexp_t serial;
char *msgdigest = NULL;
size_t msgdigestlen;
char *ctattr;
int sigval_hash_algo;
int info_pkalgo;
unsigned int nbits;
int pkalgo;
char *pkalgostr = NULL;
char *pkfpr = NULL;
unsigned int pkalgoflags, verifyflags;
rc = ksba_cms_get_issuer_serial (cms, signer, &issuer, &serial);
if (!signer && gpg_err_code (rc) == GPG_ERR_NO_DATA
&& data_fd == -1 && is_detached)
{
log_info ("certs-only message accepted\n");
rc = 0;
break;
}
if (rc)
{
if (signer && rc == -1)
rc = 0;
break;
}
gpgsm_status (ctrl, STATUS_NEWSIG, NULL);
audit_log_i (ctrl->audit, AUDIT_NEW_SIG, signer);
if (DBG_X509)
{
log_debug ("signer %d - issuer: '%s'\n",
signer, issuer? issuer:"[NONE]");
log_debug ("signer %d - serial: ", signer);
gpgsm_dump_serial (serial);
log_printf ("\n");
}
if (ctrl->audit)
{
char *tmpstr = gpgsm_format_sn_issuer (serial, issuer);
audit_log_s (ctrl->audit, AUDIT_SIG_NAME, tmpstr);
xfree (tmpstr);
}
rc = ksba_cms_get_signing_time (cms, signer, sigtime);
if (gpg_err_code (rc) == GPG_ERR_NO_DATA)
*sigtime = 0;
else if (rc)
{
log_error ("error getting signing time: %s\n", gpg_strerror (rc));
*sigtime = 0; /* (we can't encode an error in the time string.) */
}
rc = ksba_cms_get_message_digest (cms, signer,
&msgdigest, &msgdigestlen);
if (!rc)
{
algoid = ksba_cms_get_digest_algo (cms, signer);
algo = gcry_md_map_name (algoid);
if (DBG_X509)
log_debug ("signer %d - digest algo: %d\n", signer, algo);
if (! gcry_md_is_enabled (data_md, algo))
{
log_error ("digest algo %d (%s) has not been enabled\n",
algo, algoid?algoid:"");
audit_log_s (ctrl->audit, AUDIT_SIG_STATUS, "unsupported");
goto next_signer;
}
}
else if (gpg_err_code (rc) == GPG_ERR_NO_DATA)
{
assert (!msgdigest);
rc = 0;
algoid = NULL;
algo = 0;
}
else /* real error */
{
audit_log_s (ctrl->audit, AUDIT_SIG_STATUS, "error");
break;
}
rc = ksba_cms_get_sigattr_oids (cms, signer,
"1.2.840.113549.1.9.3", &ctattr);
if (!rc)
{
const char *s;
if (DBG_X509)
log_debug ("signer %d - content-type attribute: %s",
signer, ctattr);
s = ksba_cms_get_content_oid (cms, 1);
if (!s || strcmp (ctattr, s))
{
log_error ("content-type attribute does not match "
"actual content-type\n");
ksba_free (ctattr);
ctattr = NULL;
audit_log_s (ctrl->audit, AUDIT_SIG_STATUS, "bad");
goto next_signer;
}
ksba_free (ctattr);
ctattr = NULL;
}
else if (rc != -1)
{
log_error ("error getting content-type attribute: %s\n",
gpg_strerror (rc));
audit_log_s (ctrl->audit, AUDIT_SIG_STATUS, "bad");
goto next_signer;
}
rc = 0;
sigval = gpgsm_ksba_cms_get_sig_val (cms, signer);
if (!sigval)
{
log_error ("no signature value available\n");
audit_log_s (ctrl->audit, AUDIT_SIG_STATUS, "bad");
goto next_signer;
}
sigval_hash_algo = gpgsm_get_hash_algo_from_sigval (sigval, &pkalgoflags);
if (DBG_X509)
{
log_debug ("signer %d - signature available (sigval hash=%d pkaf=%u)",
signer, sigval_hash_algo, pkalgoflags);
}
if (!sigval_hash_algo)
sigval_hash_algo = algo; /* Fallback used e.g. with old libksba. */
/* Find the certificate of the signer */
keydb_search_reset (kh);
rc = keydb_search_issuer_sn (ctrl, kh, issuer, serial);
if (rc)
{
if (rc == -1)
{
log_error ("certificate not found\n");
rc = gpg_error (GPG_ERR_NO_PUBKEY);
}
else
log_error ("failed to find the certificate: %s\n",
gpg_strerror(rc));
{
char numbuf[50];
sprintf (numbuf, "%d", rc);
gpgsm_status2 (ctrl, STATUS_ERROR, "verify.findkey",
numbuf, NULL);
}
audit_log_s (ctrl->audit, AUDIT_SIG_STATUS, "no-cert");
goto next_signer;
}
rc = keydb_get_cert (kh, &cert);
if (rc)
{
log_error ("failed to get cert: %s\n", gpg_strerror (rc));
audit_log_s (ctrl->audit, AUDIT_SIG_STATUS, "error");
goto next_signer;
}
pkfpr = gpgsm_get_fingerprint_hexstring (cert, GCRY_MD_SHA1);
pkalgostr = gpgsm_pubkey_algo_string (cert, NULL);
pkalgo = gpgsm_get_key_algo_info (cert, &nbits);
log_info (_("Signature made "));
if (*sigtime)
{
/* We take the freedom as noted in RFC3339 to use a space
* instead of the "T" delimiter between date and time. We
* also append a separate UTC instead of a "Z" or "+00:00"
* suffix because that makes it clear to everyone what kind
* of time this is. */
dump_isotime (sigtime);
log_printf (" UTC");
}
else
log_printf (_("[date not given]"));
log_info (_(" using %s key %s\n"), pkalgostr, pkfpr);
if (opt.verbose)
{
log_info (_("algorithm:"));
log_printf (" %s + %s",
pubkey_algo_to_string (pkalgo),
gcry_md_algo_name (sigval_hash_algo));
if (algo != sigval_hash_algo)
log_printf (" (%s)", gcry_md_algo_name (algo));
log_printf ("\n");
}
audit_log_i (ctrl->audit, AUDIT_DATA_HASH_ALGO, algo);
/* Check compliance. */
if (! gnupg_pk_is_allowed (opt.compliance, PK_USE_VERIFICATION,
pkalgo, pkalgoflags, NULL, nbits, NULL))
{
char kidstr[10+1];
snprintf (kidstr, sizeof kidstr, "0x%08lX",
gpgsm_get_short_fingerprint (cert, NULL));
log_error (_("key %s may not be used for signing in %s mode\n"),
kidstr,
gnupg_compliance_option_string (opt.compliance));
goto next_signer;
}
if (!gnupg_digest_is_allowed (opt.compliance, 0, sigval_hash_algo))
{
log_error (_("digest algorithm '%s' may not be used in %s mode\n"),
gcry_md_algo_name (sigval_hash_algo),
gnupg_compliance_option_string (opt.compliance));
goto next_signer;
}
/* Check compliance with CO_DE_VS. */
if (gnupg_pk_is_compliant (CO_DE_VS, pkalgo, pkalgoflags,
NULL, nbits, NULL)
&& gnupg_digest_is_compliant (CO_DE_VS, sigval_hash_algo))
gpgsm_status (ctrl, STATUS_VERIFICATION_COMPLIANCE_MODE,
gnupg_status_compliance_flag (CO_DE_VS));
/* Now we can check the signature. */
if (msgdigest)
{ /* Signed attributes are available. */
gcry_md_hd_t md;
unsigned char *s;
/* Check that the message digest in the signed attributes
matches the one we calculated on the data. */
s = gcry_md_read (data_md, algo);
if ( !s || !msgdigestlen
|| gcry_md_get_algo_dlen (algo) != msgdigestlen
|| memcmp (s, msgdigest, msgdigestlen) )
{
char *fpr;
log_error (_("invalid signature: message digest attribute "
"does not match computed one\n"));
if (DBG_X509)
{
if (msgdigest)
log_printhex (msgdigest, msgdigestlen, "message: ");
if (s)
log_printhex (s, gcry_md_get_algo_dlen (algo),
"computed: ");
}
fpr = gpgsm_fpr_and_name_for_status (cert);
gpgsm_status (ctrl, STATUS_BADSIG, fpr);
xfree (fpr);
audit_log_s (ctrl->audit, AUDIT_SIG_STATUS, "bad");
goto next_signer;
}
audit_log_i (ctrl->audit, AUDIT_ATTR_HASH_ALGO, sigval_hash_algo);
rc = gcry_md_open (&md, sigval_hash_algo, 0);
if (rc)
{
log_error ("md_open failed: %s\n", gpg_strerror (rc));
audit_log_s (ctrl->audit, AUDIT_SIG_STATUS, "error");
goto next_signer;
}
if (DBG_HASHING)
gcry_md_debug (md, "vrfy.attr");
ksba_cms_set_hash_function (cms, HASH_FNC, md);
rc = ksba_cms_hash_signed_attrs (cms, signer);
if (rc)
{
log_error ("hashing signed attrs failed: %s\n",
gpg_strerror (rc));
gcry_md_close (md);
audit_log_s (ctrl->audit, AUDIT_SIG_STATUS, "error");
goto next_signer;
}
rc = gpgsm_check_cms_signature (cert, sigval, md, sigval_hash_algo,
pkalgoflags, &info_pkalgo);
gcry_md_close (md);
}
else
{
rc = gpgsm_check_cms_signature (cert, sigval, data_md,
algo, pkalgoflags, &info_pkalgo);
}
if (rc)
{
char *fpr;
log_error ("invalid signature: %s\n", gpg_strerror (rc));
fpr = gpgsm_fpr_and_name_for_status (cert);
gpgsm_status (ctrl, STATUS_BADSIG, fpr);
xfree (fpr);
audit_log_s (ctrl->audit, AUDIT_SIG_STATUS, "bad");
goto next_signer;
}
rc = gpgsm_cert_use_verify_p (cert); /*(this displays an info message)*/
if (rc)
{
gpgsm_status_with_err_code (ctrl, STATUS_ERROR, "verify.keyusage",
gpg_err_code (rc));
rc = 0;
}
if (DBG_X509)
log_debug ("signature okay - checking certs\n");
audit_log (ctrl->audit, AUDIT_VALIDATE_CHAIN);
rc = gpgsm_validate_chain (ctrl, cert,
*sigtime? sigtime : "19700101T000000",
keyexptime, 0,
NULL, 0, &verifyflags);
{
char *fpr, *buf, *tstr;
fpr = gpgsm_fpr_and_name_for_status (cert);
if (gpg_err_code (rc) == GPG_ERR_CERT_EXPIRED)
{
gpgsm_status (ctrl, STATUS_EXPKEYSIG, fpr);
rc = 0;
}
else
gpgsm_status (ctrl, STATUS_GOODSIG, fpr);
xfree (fpr);
fpr = gpgsm_get_fingerprint_hexstring (cert, GCRY_MD_SHA1);
tstr = strtimestamp_r (sigtime);
buf = xasprintf ("%s %s %s %s 0 0 %d %d 00", fpr, tstr,
*sigtime? sigtime : "0",
*keyexptime? keyexptime : "0",
info_pkalgo, algo);
xfree (tstr);
xfree (fpr);
gpgsm_status (ctrl, STATUS_VALIDSIG, buf);
xfree (buf);
}
audit_log_ok (ctrl->audit, AUDIT_CHAIN_STATUS, rc);
if (rc) /* of validate_chain */
{
log_error ("invalid certification chain: %s\n", gpg_strerror (rc));
if (gpg_err_code (rc) == GPG_ERR_BAD_CERT_CHAIN
|| gpg_err_code (rc) == GPG_ERR_BAD_CERT
|| gpg_err_code (rc) == GPG_ERR_BAD_CA_CERT
|| gpg_err_code (rc) == GPG_ERR_CERT_REVOKED)
gpgsm_status_with_err_code (ctrl, STATUS_TRUST_NEVER, NULL,
gpg_err_code (rc));
else
gpgsm_status_with_err_code (ctrl, STATUS_TRUST_UNDEFINED, NULL,
gpg_err_code (rc));
audit_log_s (ctrl->audit, AUDIT_SIG_STATUS, "bad");
goto next_signer;
}
audit_log_s (ctrl->audit, AUDIT_SIG_STATUS, "good");
for (i=0; (p = ksba_cert_get_subject (cert, i)); i++)
{
log_info (!i? _("Good signature from")
: _(" aka"));
log_printf (" \"");
gpgsm_es_print_name (log_get_stream (), p);
log_printf ("\"\n");
ksba_free (p);
}
/* Print a note if this is a qualified signature. */
{
size_t qualbuflen;
char qualbuffer[1];
rc = ksba_cert_get_user_data (cert, "is_qualified", &qualbuffer,
sizeof (qualbuffer), &qualbuflen);
if (!rc && qualbuflen)
{
if (*qualbuffer)
{
log_info (_("This is a qualified signature\n"));
if (!opt.qualsig_approval)
log_info
(_("Note, that this software is not officially approved "
"to create or verify such signatures.\n"));
}
}
else if (gpg_err_code (rc) != GPG_ERR_NOT_FOUND)
log_error ("get_user_data(is_qualified) failed: %s\n",
gpg_strerror (rc));
}
gpgsm_status (ctrl, STATUS_TRUST_FULLY,
(verifyflags & VALIDATE_FLAG_STEED)?
"0 steed":
(verifyflags & VALIDATE_FLAG_CHAIN_MODEL)?
"0 chain": "0 shell");
next_signer:
rc = 0;
xfree (issuer);
xfree (serial);
gcry_sexp_release (sigval);
xfree (msgdigest);
xfree (pkalgostr);
xfree (pkfpr);
ksba_cert_release (cert);
cert = NULL;
}
rc = 0;
leave:
ksba_cms_release (cms);
gnupg_ksba_destroy_reader (b64reader);
gnupg_ksba_destroy_writer (b64writer);
keydb_release (kh);
gcry_md_close (data_md);
es_fclose (in_fp);
if (rc)
{
char numbuf[50];
sprintf (numbuf, "%d", rc );
gpgsm_status2 (ctrl, STATUS_ERROR, "verify.leave",
numbuf, NULL);
}
return rc;
}
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