gpg,sm: New option --with-key-screening.

* common/pkscreening.c: New.
* common/pkscreening.h: New.
* common/Makefile.am (common_sources): Add them.
* g10/gpg.c (opts): New option --with-key-screening.
* g10/options.h (struct opt): New field with_key_screening.
* g10/keylist.c: Include pkscreening.h.
(print_pk_screening): New.
(list_keyblock_print): Call it.
(print_compliance_flags): Call it.
* sm/gpgsm.c (opts): New option --with-key-screening.
* sm/gpgsm.h (scruct opt): New field with_key_screening.
* sm/keylist.c:  Include pkscreening.h.
(print_pk_screening): New.
(print_compliance_flags): Call it.  Add new arg cert.
(list_cert_colon): Pass arg cert
(list_cert_std): Call print_pk_screening.
* sm/fingerprint.c (gpgsm_get_rsa_modulus): New.
--

This new option can be used to detect ROCA affected keys.  To scan an
entire keyring and print the affected fingerprints use this:

  gpg -k --with-key-screening --with-colons | gawk -F: \
       '$1~/pub|sub|sec|ssb|crt/ && $18~/\<6001\>/ {found=1;next};
        $1=="fpr" && found {print $10}; {found=0}'

The same works for gpgsm.  Note that we need gawk due to the "\<" in
the r.e.

Signed-off-by: Werner Koch <[email protected]>

1 files changed, 159 insertions, 0 deletions

diff --git a/common/pkscreening.c b/common/pkscreening.c
new file mode 100644
index 000000000..a3bfb474e
--- /dev/null
+++ b/common/pkscreening.c
@@ -0,0 +1,159 @@
+/* pkscreening.c - Screen public keys for vulnerabilities
+ * Copyright (C) 2017 Werner Koch
+ *
+ * This file is part of GnuPG.
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This file 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 Lesser General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <stdlib.h>
+
+#include "util.h"
+#include "pkscreening.h"
+
+
+/* Helper */
+static inline gpg_error_t
+my_error (gpg_err_code_t ec)
+{
+  return gpg_err_make (default_errsource, ec);
+}
+
+
+/* Emulation of the new gcry_mpi_get_ui function.  */
+static gpg_error_t
+my_mpi_get_ui (unsigned int *v, gcry_mpi_t a)
+{
+  gpg_error_t err;
+  unsigned char buf[8];
+  size_t n;
+  int i, mul;
+
+  if (gcry_mpi_cmp_ui (a, 16384) > 0)
+    return my_error (GPG_ERR_ERANGE); /* Clearly too large for our purpose.  */
+
+  err = gcry_mpi_print (GCRYMPI_FMT_USG, buf, sizeof buf, &n, a);
+  if (err)
+    return err;
+
+  *v = 0;
+  for (i = n - 1, mul = 1; i >= 0; i--, mul *= 256)
+    *v += mul * buf[i];
+
+  return 0;
+}
+
+
+/* Detect whether the MODULUS of a public RSA key is affected by the
+ * ROCA vulnerability as found in the Infinion RSA library
+ * (CVE-2017-15361).  Returns 0 if not affected, GPG_ERR_TRUE if
+ * affected, GPG_ERR_BAD_MPI if an opaque RSA was passed, or other
+ * error codes if something weird happened  */
+gpg_error_t
+screen_key_for_roca (gcry_mpi_t modulus)
+{
+  static struct {
+    unsigned int prime_ui;
+    const char *print_hex;
+    gcry_mpi_t prime;
+    gcry_mpi_t print;
+  } table[] = {
+   { 3,   "0x6" },
+   { 5,   "0x1E" },
+   { 7,   "0x7E" },
+   { 11,  "0x402" },
+   { 13,  "0x161A" },
+   { 17,  "0x1A316" },
+   { 19,  "0x30AF2" },
+   { 23,  "0x7FFFFE" },
+   { 29,  "0x1FFFFFFE" },
+   { 31,  "0x7FFFFFFE" },
+   { 37,  "0x4000402"  },
+   { 41,  "0x1FFFFFFFFFE" },
+   { 43,  "0x7FFFFFFFFFE" },
+   { 47,  "0x7FFFFFFFFFFE" },
+   { 53,  "0x12DD703303AED2" },
+   { 59,  "0x7FFFFFFFFFFFFFE" },
+   { 61,  "0x1434026619900B0A" },
+   { 67,  "0x7FFFFFFFFFFFFFFFE" },
+   { 71,  "0x1164729716B1D977E" },
+   { 73,  "0x147811A48004962078A" },
+   { 79,  "0xB4010404000640502"   },
+   { 83,  "0x7FFFFFFFFFFFFFFFFFFFE" },
+   { 89,  "0x1FFFFFFFFFFFFFFFFFFFFFE" },
+   { 97,  "0x1000000006000001800000002" },
+   { 101, "0x1FFFFFFFFFFFFFFFFFFFFFFFFE" },
+   { 103, "0x16380E9115BD964257768FE396" },
+   { 107, "0x27816EA9821633397BE6A897E1A" },
+   { 109, "0x1752639F4E85B003685CBE7192BA" },
+   { 113, "0x1FFFFFFFFFFFFFFFFFFFFFFFFFFFE" },
+   { 127, "0x6CA09850C2813205A04C81430A190536" },
+   { 131, "0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE" },
+   { 137, "0x1FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE" },
+   { 139, "0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE" },
+   { 149, "0x1FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE" },
+   { 151, "0x50C018BC00482458DAC35B1A2412003D18030A" },
+   { 157, "0x161FB414D76AF63826461899071BD5BACA0B7E1A" },
+   { 163, "0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE" },
+   { 167, "0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE" }
+  };
+  gpg_error_t err;
+  int i;
+  gcry_mpi_t rem;
+  unsigned int bitno;
+
+  /* Initialize on the first call. */
+  if (!table[0].prime)
+    {
+      /* We pass primes[i] to the call so that in case of a concurrent
+       * second thread the already allocated space is reused.  */
+      for (i = 0; i < DIM (table); i++)
+        {
+          table[i].prime = gcry_mpi_set_ui (table[i].prime, table[i].prime_ui);
+          if (gcry_mpi_scan (&table[i].print, GCRYMPI_FMT_HEX,
+                             table[i].print_hex, 0, NULL))
+            BUG ();
+        }
+    }
+
+  /* Check that it is not NULL or an opaque MPI.  */
+  if (!modulus || gcry_mpi_get_flag (modulus, GCRYMPI_FLAG_OPAQUE))
+    return my_error (GPG_ERR_BAD_MPI);
+
+  /* We divide the modulus of an RSA public key by a set of small
+   * PRIMEs and examine all the remainders.  If all the bits at the
+   * index given by the remainder are set in the corresponding PRINT
+   * masks the key is very likely vulnerable.  If any of the tested
+   * bits is zero, the key is not vulnerable.  */
+  rem = gcry_mpi_new (0);
+  for (i = 0; i < DIM (table); i++)
+    {
+      gcry_mpi_mod (rem, modulus, table[i].prime);
+      err = my_mpi_get_ui (&bitno, rem);
+      if (gpg_err_code (err) == GPG_ERR_ERANGE)
+        continue;
+      if (err)
+        goto leave;
+      if (!gcry_mpi_test_bit (table[i].print, bitno))
+        goto leave;  /* Not vulnerable.  */
+    }
+
+  /* Very likely vulnerable */
+  err = my_error (GPG_ERR_TRUE);
+
+ leave:
+  gcry_mpi_release (rem);
+  return err;
+}