Adding upstream version 2.2.40.upstream/2.2.40upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 616 insertions, 0 deletions

diff --git a/sm/certcheck.c b/sm/certcheck.c
new file mode 100644
index 0000000..d6b967c
--- /dev/null
+++ b/sm/certcheck.c
@@ -0,0 +1,616 @@
+/* certcheck.c - check one certificate
+ * Copyright (C) 2001, 2003, 2004 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"
+
+
+/* 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_sexp_t pkey, gcry_mpi_t *r_val)
+{
+  int n;
+  size_t nframe;
+  unsigned char *frame;
+
+  if (pkalgo == GCRY_PK_DSA || pkalgo == GCRY_PK_ECDSA)
+    {
+      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 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
+    {
+      int i;
+      unsigned char asn[100];
+      size_t asnlen;
+      size_t len;
+
+      nframe = (nbits+7) / 8;
+
+      asnlen = DIM(asn);
+      if (!algo || gcry_md_test_algo (algo))
+        return gpg_error (GPG_ERR_DIGEST_ALGO);
+      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 ();
+      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;
+  /* Because this function is called only for verification we can
+     assume that ECC actually means ECDSA.  */
+  else if (n==3 && !memcmp (name, "ecc", 3))
+    algo = GCRY_PK_ECDSA;
+  else if (n==13 && !memcmp (name, "ambiguous-rsa", 13))
+    algo = GCRY_PK_RSA;
+  else
+    algo = 0;
+  gcry_sexp_release (l2);
+  return algo;
+}
+
+
+/* Return the hash algorithm's algo id from its name given in the
+ * non-null termnated string in (buffer,buflen).  Returns 0 on failure
+ * or if the algo is not known.  */
+static int
+hash_algo_from_buffer (const void *buffer, size_t buflen)
+{
+  char *string;
+  int algo;
+
+  string = xtrymalloc (buflen + 1);
+  if (!string)
+    {
+      log_error (_("out of core\n"));
+      return 0;
+    }
+  memcpy (string, buffer, buflen);
+  string[buflen] = 0;
+  algo = gcry_md_map_name (string);
+  if (!algo)
+    log_error ("unknown digest algorithm '%s' used in certificate\n", string);
+  xfree (string);
+  return algo;
+}
+
+
+/* Return an unsigned integer from the non-null termnated string
+ * (buffer,buflen).  Returns 0 on failure.  */
+static unsigned int
+uint_from_buffer (const void *buffer, size_t buflen)
+{
+  char *string;
+  unsigned int val;
+
+  string = xtrymalloc (buflen + 1);
+  if (!string)
+    {
+      log_error (_("out of core\n"));
+      return 0;
+    }
+  memcpy (string, buffer, buflen);
+  string[buflen] = 0;
+  val = strtoul (string, NULL, 10);
+  xfree (string);
+  return val;
+}
+
+
+/* Extract the hash algorithm and the salt length from the sigval.  */
+static gpg_error_t
+extract_pss_params (gcry_sexp_t s_sig, int *r_algo, unsigned int *r_saltlen)
+{
+  gpg_error_t err;
+  gcry_buffer_t ioarray[2] = { {0}, {0} };
+
+  err = gcry_sexp_extract_param (s_sig, "sig-val",
+                                 "&'hash-algo''salt-length'",
+                                 ioarray+0, ioarray+1, NULL);
+  if (err)
+    {
+      log_error ("extracting params from PSS failed: %s\n", gpg_strerror (err));
+      return err;
+    }
+
+  *r_algo = hash_algo_from_buffer (ioarray[0].data, ioarray[0].len);
+  *r_saltlen = uint_from_buffer (ioarray[1].data, ioarray[1].len);
+  xfree (ioarray[0].data);
+  xfree (ioarray[1].data);
+  if (*r_saltlen < 20)
+    {
+      log_error ("length of PSS salt too short\n");
+      return gpg_error (GPG_ERR_DIGEST_ALGO);
+    }
+  if (!*r_algo)
+    {
+      return gpg_error (GPG_ERR_DIGEST_ALGO);
+    }
+
+  /* PSS has no hash function firewall like PKCS#1 and thus offers
+   * a path for hash algorithm replacement.  To avoid this it makes
+   * sense to restrict the allowed hash algorithms and also allow only
+   * matching salt lengths.  According to Peter Gutmann:
+   *  "Beware of bugs in the above signature scheme;
+   *   I have only proved it secure, not implemented it"
+   *   - Apologies to Donald Knuth.
+   * https://www.metzdowd.com/pipermail/cryptography/2019-November/035449.html
+   *
+   * Given the set of supported algorithms currently available in
+   * Libgcrypt and the extra hash checks we have in some compliance
+   * modes, it would be hard to trick gpgsm to verify a forged
+   * signature.  However, if eventually someone adds the xor256 hash
+   * algorithm (1.3.6.1.4.1.3029.3.2) to Libgcrypt we would be doomed.
+   */
+  switch (*r_algo)
+    {
+    case GCRY_MD_SHA1:
+    case GCRY_MD_SHA256:
+    case GCRY_MD_SHA384:
+    case GCRY_MD_SHA512:
+    case GCRY_MD_SHA3_256:
+    case GCRY_MD_SHA3_384:
+    case GCRY_MD_SHA3_512:
+      break;
+    default:
+      log_error ("PSS hash algorithm '%s' rejected\n",
+                 gcry_md_algo_name (*r_algo));
+      return gpg_error (GPG_ERR_DIGEST_ALGO);
+    }
+
+  if (gcry_md_get_algo_dlen (*r_algo) != *r_saltlen)
+    {
+      log_error ("PSS hash algorithm '%s' rejected due to salt length %u\n",
+                 gcry_md_algo_name (*r_algo), *r_saltlen);
+      return gpg_error (GPG_ERR_DIGEST_ALGO);
+    }
+
+  return 0;
+}
+
+
+/* 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;
+  ksba_sexp_t p;
+  size_t n;
+  gcry_sexp_t s_sig, s_data, s_pkey;
+  int use_pss = 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 (!algo)
+    {
+      log_error ("unknown digest algorithm '%s' used certificate\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);
+    }
+
+  /* The the signature from the certificate.  */
+  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");
+      ksba_free (p);
+      return gpg_error (GPG_ERR_BUG);
+    }
+  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));
+      return rc;
+    }
+  if (DBG_CRYPTO)
+    gcry_log_debugsxp ("sigval", s_sig);
+
+  if (use_pss)
+    {
+      rc = extract_pss_params (s_sig, &algo, &saltlen);
+      if (rc)
+        {
+          gcry_sexp_release (s_sig);
+          return rc;
+        }
+    }
+
+
+  /* Hash the to-be-signed parts of the certificate.  */
+  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);
+
+  /* Get the public key from the certificate.  */
+  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;
+    }
+  if (DBG_CRYPTO)
+    gcry_log_debugsxp ("pubkey:", s_pkey);
+
+  if (use_pss)
+    {
+      rc = gcry_sexp_build (&s_data, NULL,
+                            "(data (flags pss)"
+                            "(hash %s %b)"
+                            "(salt-length %u))",
+                            hash_algo_to_string (algo),
+                            (int)gcry_md_get_algo_dlen (algo),
+                            gcry_md_read (md, algo),
+                            saltlen);
+      if (rc)
+        BUG ();
+    }
+  else
+    {
+      /* RSA or DSA: Prepare the hash for verification.  */
+      gcry_mpi_t frame;
+
+      rc = do_encode_md (md, algo, pk_algo_from_sexp (s_pkey),
+                         gcry_pk_get_nbits (s_pkey), s_pkey, &frame);
+      if (rc)
+        {
+          gcry_md_close (md);
+          gcry_sexp_release (s_sig);
+          gcry_sexp_release (s_pkey);
+          return rc;
+        }
+      if ( gcry_sexp_build (&s_data, NULL, "%m", frame) )
+        BUG ();
+      gcry_mpi_release (frame);
+    }
+  if (DBG_CRYPTO)
+    gcry_log_debugsxp ("data:", s_data);
+
+  /* Verify.  */
+  rc = gcry_pk_verify (s_sig, s_data, 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_data);
+  gcry_sexp_release (s_pkey);
+  return rc;
+}
+
+
+
+int
+gpgsm_check_cms_signature (ksba_cert_t cert, gcry_sexp_t s_sig,
+                           gcry_md_hd_t md, int mdalgo,
+                           unsigned int pkalgoflags, int *r_pkalgo)
+{
+  int rc;
+  ksba_sexp_t p;
+  gcry_sexp_t s_hash, s_pkey;
+  size_t n;
+  int pkalgo;
+  int use_pss;
+  unsigned int saltlen = 0;
+
+  if (r_pkalgo)
+    *r_pkalgo = 0;
+
+  /* Check whether rsaPSS is needed.  This information is indicated in
+   * the SIG-VAL and already provided to us by the caller so that we
+   * do not need to parse this out. */
+  use_pss = !!(pkalgoflags & PK_ALGO_FLAG_RSAPSS);
+  if (use_pss)
+    {
+      int algo;
+
+      rc = extract_pss_params (s_sig, &algo, &saltlen);
+      if (rc)
+        {
+          gcry_sexp_release (s_sig);
+          return rc;
+        }
+      if (algo != mdalgo)
+        {
+          log_error ("PSS hash algo mismatch (%d/%d)\n", mdalgo, algo);
+          gcry_sexp_release (s_sig);
+          return gpg_error (GPG_ERR_DIGEST_ALGO);
+        }
+    }
+
+  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);
+      return gpg_error (GPG_ERR_BUG);
+    }
+  if (DBG_CRYPTO)
+    log_printhex (p, n, "public key: ");
+
+  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));
+      return rc;
+    }
+
+  pkalgo = pk_algo_from_sexp (s_pkey);
+  if (r_pkalgo)
+    *r_pkalgo = pkalgo;
+
+  if (use_pss)
+    {
+      rc = gcry_sexp_build (&s_hash, NULL,
+                            "(data (flags pss)"
+                            "(hash %s %b)"
+                            "(salt-length %u))",
+                            hash_algo_to_string (mdalgo),
+                            (int)gcry_md_get_algo_dlen (mdalgo),
+                            gcry_md_read (md, mdalgo),
+                            saltlen);
+      if (rc)
+        BUG ();
+    }
+  else
+    {
+      /* RSA or DSA: Prepare the hash for verification.  */
+      gcry_mpi_t frame;
+
+      rc = do_encode_md (md, mdalgo, pkalgo,
+                         gcry_pk_get_nbits (s_pkey), s_pkey, &frame);
+      if (rc)
+        {
+          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_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;
+}