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gnupg/common/compliance.c

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/* compliance.c - Functions for compliance modi
* Copyright (C) 2017 g10 Code GmbH
* Copyright (C) 2017 Bundesamt für Sicherheit in der Informationstechnik
*
* This file is part of GnuPG.
*
* This file is free software; you can redistribute it and/or modify
* it under the terms of either
*
* - the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 3 of the License, or (at
* your option) any later version.
*
* or
*
* - 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.
*
* or both in parallel, as here.
*
* 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 General Public License
* along with this program; if not, see <https://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <gcrypt.h>
#include "openpgpdefs.h"
#include "logging.h"
#include "util.h"
#include "i18n.h"
#include "compliance.h"
static int initialized;
static int module;
/* This value is used by DSA and RSA checks in addition to the hard
* coded length checks. It allows one to increase the required key length
* using a confue file. */
static unsigned int min_compliant_rsa_length;
/* Return the address of a compliance cache variable for COMPLIANCE.
* If no such variable exists NULL is returned. FOR_RNG returns the
* cache variable for the RNG compliance check. */
static int *
get_compliance_cache (enum gnupg_compliance_mode compliance, int for_rng)
{
static int r_gnupg = -1, s_gnupg = -1;
static int r_rfc4880 = -1, s_rfc4880 = -1;
static int r_rfc2440 = -1, s_rfc2440 = -1;
static int r_pgp7 = -1, s_pgp7 = -1;
static int r_pgp8 = -1, s_pgp8 = -1;
static int r_de_vs = -1, s_de_vs = -1;
int *ptr = NULL;
switch (compliance)
{
case CO_GNUPG: ptr = for_rng? &r_gnupg : &s_gnupg ; break;
case CO_RFC4880: ptr = for_rng? &r_rfc4880 : &s_rfc4880; break;
case CO_RFC2440: ptr = for_rng? &r_rfc2440 : &s_rfc2440; break;
case CO_PGP7: ptr = for_rng? &r_pgp7 : &s_pgp7 ; break;
case CO_PGP8: ptr = for_rng? &r_pgp8 : &s_pgp8 ; break;
case CO_DE_VS: ptr = for_rng? &r_de_vs : &s_de_vs ; break;
}
return ptr;
}
/* Initializes the module. Must be called with the current
* GNUPG_MODULE_NAME. Checks a few invariants, and tunes the policies
* for the given module. */
void
gnupg_initialize_compliance (int gnupg_module_name)
{
log_assert (! initialized);
/* We accept both OpenPGP-style and gcrypt-style algorithm ids.
* Assert that they are compatible. At some places gcrypt ids are
* used which can't be encoded in an OpenPGP algo octet; we also
* assert this. */
log_assert ((int) GCRY_PK_RSA == (int) PUBKEY_ALGO_RSA);
log_assert ((int) GCRY_PK_RSA_E == (int) PUBKEY_ALGO_RSA_E);
log_assert ((int) GCRY_PK_RSA_S == (int) PUBKEY_ALGO_RSA_S);
log_assert ((int) GCRY_PK_ELG_E == (int) PUBKEY_ALGO_ELGAMAL_E);
log_assert ((int) GCRY_PK_DSA == (int) PUBKEY_ALGO_DSA);
log_assert ((int) GCRY_PK_ECC == (int) PUBKEY_ALGO_ECDH);
log_assert ((int) GCRY_PK_ELG == (int) PUBKEY_ALGO_ELGAMAL);
log_assert ((int) GCRY_PK_ECDSA > 255);
log_assert ((int) GCRY_PK_ECDH > 255);
log_assert ((int) GCRY_PK_EDDSA > 255);
log_assert ((int) GCRY_CIPHER_NONE == (int) CIPHER_ALGO_NONE);
log_assert ((int) GCRY_CIPHER_IDEA == (int) CIPHER_ALGO_IDEA);
log_assert ((int) GCRY_CIPHER_3DES == (int) CIPHER_ALGO_3DES);
log_assert ((int) GCRY_CIPHER_CAST5 == (int) CIPHER_ALGO_CAST5);
log_assert ((int) GCRY_CIPHER_BLOWFISH == (int) CIPHER_ALGO_BLOWFISH);
log_assert ((int) GCRY_CIPHER_AES == (int) CIPHER_ALGO_AES);
log_assert ((int) GCRY_CIPHER_AES192 == (int) CIPHER_ALGO_AES192);
log_assert ((int) GCRY_CIPHER_AES256 == (int) CIPHER_ALGO_AES256);
log_assert ((int) GCRY_CIPHER_TWOFISH == (int) CIPHER_ALGO_TWOFISH);
log_assert ((int) GCRY_MD_MD5 == (int) DIGEST_ALGO_MD5);
log_assert ((int) GCRY_MD_SHA1 == (int) DIGEST_ALGO_SHA1);
log_assert ((int) GCRY_MD_RMD160 == (int) DIGEST_ALGO_RMD160);
log_assert ((int) GCRY_MD_SHA256 == (int) DIGEST_ALGO_SHA256);
log_assert ((int) GCRY_MD_SHA384 == (int) DIGEST_ALGO_SHA384);
log_assert ((int) GCRY_MD_SHA512 == (int) DIGEST_ALGO_SHA512);
log_assert ((int) GCRY_MD_SHA224 == (int) DIGEST_ALGO_SHA224);
switch (gnupg_module_name)
{
case GNUPG_MODULE_NAME_GPGSM:
case GNUPG_MODULE_NAME_GPG:
break;
default:
log_assert (!"no policies for this module");
}
module = gnupg_module_name;
initialized = 1;
}
/* Return true if ALGO with a key of KEYLENGTH is compliant to the
* given COMPLIANCE mode. If KEY is not NULL, various bits of
* information will be extracted from it. If CURVENAME is not NULL, it
* is assumed to be the already computed. ALGO may be either an
* OpenPGP-style pubkey_algo_t, or a gcrypt-style enum gcry_pk_algos,
* both are compatible from the point of view of this function. */
int
gnupg_pk_is_compliant (enum gnupg_compliance_mode compliance, int algo,
unsigned int algo_flags,
gcry_mpi_t key[], unsigned int keylength,
const char *curvename)
{
enum { is_rsa, is_dsa, is_elg, is_ecc, is_kem } algotype;
int result = 0;
if (! initialized)
return 0;
switch (algo)
{
case PUBKEY_ALGO_RSA:
case PUBKEY_ALGO_RSA_E:
case PUBKEY_ALGO_RSA_S:
algotype = is_rsa;
break;
case PUBKEY_ALGO_DSA:
algotype = is_dsa;
break;
case PUBKEY_ALGO_ELGAMAL_E:
algotype = is_elg;
break;
case PUBKEY_ALGO_ECDH:
case PUBKEY_ALGO_ECDSA:
case PUBKEY_ALGO_EDDSA:
case GCRY_PK_ECDSA:
case GCRY_PK_ECDH:
case GCRY_PK_EDDSA:
algotype = is_ecc;
break;
case PUBKEY_ALGO_ELGAMAL:
return 0; /* Signing with Elgamal is not at all supported. */
case PUBKEY_ALGO_KYBER:
algotype = is_kem;
break;
default: /* Unknown. */
return 0;
}
if (compliance == CO_DE_VS)
{
char *curve = NULL;
switch (algotype)
{
case is_elg:
result = 0;
break;
case is_rsa:
result = ((keylength == 2048
|| keylength == 3072
|| keylength == 4096)
&& keylength >= min_compliant_rsa_length);
/* Although rsaPSS was not part of the original evaluation
* we got word that we can claim compliance. */
(void)algo_flags;
break;
case is_dsa:
if (key)
{
size_t P = gcry_mpi_get_nbits (key[0]);
size_t Q = gcry_mpi_get_nbits (key[1]);
result = (Q == 256
&& (P == 2048 || P == 3072)
&& P >= min_compliant_rsa_length);
}
break;
case is_ecc:
if (!curvename && key)
{
curve = openpgp_oid_to_str (key[0]);
curvename = openpgp_oid_to_curve (curve, 0);
if (!curvename)
curvename = curve;
}
result = (curvename
&& (algo == PUBKEY_ALGO_ECDH
|| algo == PUBKEY_ALGO_ECDSA
|| algo == GCRY_PK_ECDH
|| algo == GCRY_PK_ECDSA)
&& (!strcmp (curvename, "brainpoolP256r1")
|| !strcmp (curvename, "brainpoolP384r1")
|| !strcmp (curvename, "brainpoolP512r1")));
break;
case is_kem:
result = 0;
break;
default:
result = 0;
}
xfree (curve);
}
else
{
result = 1; /* Assume compliance. */
}
return result;
}
/* Return true if ALGO with the given KEYLENGTH is allowed in the
* given COMPLIANCE mode. USE specifies for which use case the
* predicate is evaluated. This way policies can be strict in what
* they produce, and liberal in what they accept. */
int
gnupg_pk_is_allowed (enum gnupg_compliance_mode compliance,
enum pk_use_case use, int algo,
unsigned int algo_flags, gcry_mpi_t key[],
unsigned int keylength, const char *curvename)
{
int result = 0;
if (! initialized)
return 1;
/* Map the the generic ECC algo to ECDSA if requested. */
if ((algo_flags & PK_ALGO_FLAG_ECC18)
&& algo == GCRY_PK_ECC
&& (use == PK_USE_VERIFICATION
|| use == PK_USE_SIGNING))
algo = GCRY_PK_ECDSA;
switch (compliance)
{
case CO_DE_VS:
switch (algo)
{
case PUBKEY_ALGO_RSA:
case PUBKEY_ALGO_RSA_E:
case PUBKEY_ALGO_RSA_S:
switch (use)
{
case PK_USE_DECRYPTION:
case PK_USE_VERIFICATION:
result = 1;
break;
case PK_USE_ENCRYPTION:
case PK_USE_SIGNING:
result = ((keylength == 2048
|| keylength == 3072
|| keylength == 4096)
&& keylength >= min_compliant_rsa_length);
break;
default:
log_assert (!"reached");
}
break;
case PUBKEY_ALGO_DSA:
if (use == PK_USE_VERIFICATION)
result = 1;
else if (use == PK_USE_SIGNING && key)
{
size_t P = gcry_mpi_get_nbits (key[0]);
size_t Q = gcry_mpi_get_nbits (key[1]);
result = (Q == 256
&& (P == 2048 || P == 3072)
&& keylength >= min_compliant_rsa_length);
}
break;
case PUBKEY_ALGO_ELGAMAL:
case PUBKEY_ALGO_ELGAMAL_E:
result = (use == PK_USE_DECRYPTION);
break;
case PUBKEY_ALGO_ECDH: /* Same value as GCRY_PK_ECC, i.e. 18 */
case GCRY_PK_ECDH:
if (use == PK_USE_DECRYPTION)
result = 1;
else if (use == PK_USE_ENCRYPTION)
{
char *curve = NULL;
if (!curvename && key)
{
curve = openpgp_oid_to_str (key[0]);
curvename = openpgp_oid_to_curve (curve, 0);
if (!curvename)
curvename = curve;
}
result = (curvename
&& (!strcmp (curvename, "brainpoolP256r1")
|| !strcmp (curvename, "brainpoolP384r1")
|| !strcmp (curvename, "brainpoolP512r1")));
xfree (curve);
}
break;
case PUBKEY_ALGO_ECDSA:
case GCRY_PK_ECDSA:
if (use == PK_USE_VERIFICATION)
result = 1;
else
{
char *curve = NULL;
if (! curvename && key)
{
curve = openpgp_oid_to_str (key[0]);
curvename = openpgp_oid_to_curve (curve, 0);
if (!curvename)
curvename = curve;
}
result = (use == PK_USE_SIGNING
&& curvename
&& (!strcmp (curvename, "brainpoolP256r1")
|| !strcmp (curvename, "brainpoolP384r1")
|| !strcmp (curvename, "brainpoolP512r1")));
xfree (curve);
}
break;
case PUBKEY_ALGO_EDDSA:
if (use == PK_USE_VERIFICATION)
result = 1;
else /* We may not create such signatures in de-vs mode. */
result = 0;
break;
default:
break;
}
break;
default:
/* The default policy is to allow all algorithms. */
result = 1;
}
return result;
}
/* Return true if (CIPHER, MODE) is compliant to the given COMPLIANCE mode. */
int
gnupg_cipher_is_compliant (enum gnupg_compliance_mode compliance,
cipher_algo_t cipher,
enum gcry_cipher_modes mode)
{
if (! initialized)
return 0;
switch (compliance)
{
case CO_DE_VS:
switch (cipher)
{
case CIPHER_ALGO_AES:
case CIPHER_ALGO_AES192:
case CIPHER_ALGO_AES256:
case CIPHER_ALGO_3DES:
switch (module)
{
case GNUPG_MODULE_NAME_GPG:
return mode == GCRY_CIPHER_MODE_CFB;
case GNUPG_MODULE_NAME_GPGSM:
return mode == GCRY_CIPHER_MODE_CBC;
}
log_assert (!"reached");
default:
return 0;
}
log_assert (!"reached");
default:
return 0;
}
log_assert (!"reached");
}
/* Return true if CIPHER is allowed in the given COMPLIANCE mode. If
* PRODUCER is true, the predicate is evaluated for the producer, if
* false for the consumer. This way policies can be strict in what
* they produce, and liberal in what they accept. */
int
gnupg_cipher_is_allowed (enum gnupg_compliance_mode compliance, int producer,
cipher_algo_t cipher,
enum gcry_cipher_modes mode)
{
if (! initialized)
return 1;
switch (compliance)
{
case CO_DE_VS:
switch (cipher)
{
case CIPHER_ALGO_AES:
case CIPHER_ALGO_AES192:
case CIPHER_ALGO_AES256:
case CIPHER_ALGO_3DES:
switch (module)
{
case GNUPG_MODULE_NAME_GPG:
return (mode == GCRY_CIPHER_MODE_NONE
|| mode == GCRY_CIPHER_MODE_CFB);
case GNUPG_MODULE_NAME_GPGSM:
return (mode == GCRY_CIPHER_MODE_NONE
|| mode == GCRY_CIPHER_MODE_CBC
|| (mode == GCRY_CIPHER_MODE_GCM && !producer));
}
log_assert (!"reached");
case CIPHER_ALGO_BLOWFISH:
case CIPHER_ALGO_CAMELLIA128:
case CIPHER_ALGO_CAMELLIA192:
case CIPHER_ALGO_CAMELLIA256:
case CIPHER_ALGO_CAST5:
case CIPHER_ALGO_IDEA:
case CIPHER_ALGO_TWOFISH:
return (module == GNUPG_MODULE_NAME_GPG
&& (mode == GCRY_CIPHER_MODE_NONE
|| mode == GCRY_CIPHER_MODE_CFB)
&& ! producer);
default:
return 0;
}
log_assert (!"reached");
default:
/* The default policy is to allow all algorithms. */
return 1;
}
log_assert (!"reached");
}
/* Return true if DIGEST is compliant to the given COMPLIANCE mode. */
int
gnupg_digest_is_compliant (enum gnupg_compliance_mode compliance,
digest_algo_t digest)
{
if (! initialized)
return 0;
switch (compliance)
{
case CO_DE_VS:
switch (digest)
{
case DIGEST_ALGO_SHA256:
case DIGEST_ALGO_SHA384:
case DIGEST_ALGO_SHA512:
return 1;
default:
return 0;
}
log_assert (!"reached");
default:
return 0;
}
log_assert (!"reached");
}
/* Return true if DIGEST is allowed in the given COMPLIANCE mode. If
* PRODUCER is true, the predicate is evaluated for the producer, if
* false for the consumer. This way policies can be strict in what
* they produce, and liberal in what they accept. */
int
gnupg_digest_is_allowed (enum gnupg_compliance_mode compliance, int producer,
digest_algo_t digest)
{
if (! initialized)
return 1;
switch (compliance)
{
case CO_DE_VS:
switch (digest)
{
case DIGEST_ALGO_SHA256:
case DIGEST_ALGO_SHA384:
case DIGEST_ALGO_SHA512:
return 1;
case DIGEST_ALGO_SHA1:
case DIGEST_ALGO_SHA224:
case DIGEST_ALGO_RMD160:
return ! producer;
case DIGEST_ALGO_MD5:
return ! producer && module == GNUPG_MODULE_NAME_GPGSM;
default:
return 0;
}
log_assert (!"reached");
default:
/* The default policy is to allow all algorithms. */
return 1;
}
log_assert (!"reached");
}
/* Return True if the random number generator is compliant in
* COMPLIANCE mode. */
int
gnupg_rng_is_compliant (enum gnupg_compliance_mode compliance)
{
int *result;
int res;
/* #warning debug code ahead */
/* return 1; */
result = get_compliance_cache (compliance, 1);
if (result && *result != -1)
res = *result; /* Use cached result. */
else if (compliance == CO_DE_VS)
{
/* We also check whether the library is at all compliant. */
res = gnupg_gcrypt_is_compliant (compliance);
/* In DE_VS mode under Windows we also require that the JENT RNG
* is active. Check it here. */
#ifdef HAVE_W32_SYSTEM
if (res == 1)
{
char *buf;
const char *fields[5];
buf = gcry_get_config (0, "rng-type");
if (buf
&& split_fields_colon (buf, fields, DIM (fields)) >= 5
&& atoi (fields[4]) > 0)
; /* Field 5 > 0 := Jent is active. */
else
result = 0; /* Force non-compliance. */
gcry_free (buf);
}
#endif /*HAVE_W32_SYSTEM*/
}
else
res = 1;
if (result)
*result = res;
return res;
}
/* Return true if the used Libgcrypt is compliant in COMPLIANCE
* mode. */
int
gnupg_gcrypt_is_compliant (enum gnupg_compliance_mode compliance)
{
int *result;
int res;
result = get_compliance_cache (compliance, 0);
if (result && *result != -1)
res = *result; /* Use cached result. */
else if (compliance == CO_DE_VS)
{
int is19orlater = !!gcry_check_version ("1.9.0");
/* A compliant version of GnuPG requires Libgcrypt >= 1.8.1 and
* less than 1.9.0. Version 1.9.0 requires a re-evaluation and
* can thus not be used for de-vs. */
if (gcry_check_version ("1.8.1") && !is19orlater)
res = 1; /* Compliant version of Libgcrypt. */
else if (is19orlater)
{
/* Libgcrypt might be nice enough to tell us whether it is
* compliant. */
char *buf;
const char *fields[3];
buf = gcry_get_config (0, "compliance");
if (buf
&& split_fields_colon (buf, fields, DIM (fields)) >= 2
&& strstr (fields[1], "de-vs"))
res = 1; /* Compliant. */
else
res = 0; /* Non-compliant. */
gcry_free (buf);
}
else
res = 0; /* Non-compliant version of Libgcrypt. */
}
else
res = 1;
if (result)
*result = res;
return res;
}
const char *
gnupg_status_compliance_flag (enum gnupg_compliance_mode compliance)
{
switch (compliance)
{
case CO_GNUPG:
return "8";
case CO_RFC4880:
case CO_RFC2440:
case CO_PGP7:
case CO_PGP8:
log_assert (!"no status code assigned for this compliance mode");
case CO_DE_VS:
return "23";
}
log_assert (!"invalid compliance mode");
}
/* Parse the value of --compliance. Returns the value corresponding
* to the given STRING according to OPTIONS of size LENGTH, or -1
* indicating that the lookup was unsuccessful, or the list of options
* was printed. If quiet is false, an additional hint to use 'help'
* is printed on unsuccessful lookups. */
int
gnupg_parse_compliance_option (const char *string,
struct gnupg_compliance_option options[],
size_t length,
int quiet)
{
size_t i;
if (! ascii_strcasecmp (string, "help"))
{
log_info (_("valid values for option '%s':\n"), "--compliance");
for (i = 0; i < length; i++)
log_info (" %s\n", options[i].keyword);
return -1;
}
for (i = 0; i < length; i++)
if (! ascii_strcasecmp (string, options[i].keyword))
return options[i].value;
log_error (_("invalid value for option '%s'\n"), "--compliance");
if (! quiet)
log_info (_("(use \"help\" to list choices)\n"));
return -1;
}
/* Return the command line option for the given COMPLIANCE mode. */
const char *
gnupg_compliance_option_string (enum gnupg_compliance_mode compliance)
{
switch (compliance)
{
case CO_GNUPG: return "--compliance=gnupg";
case CO_RFC4880: return "--compliance=openpgp";
case CO_RFC2440: return "--compliance=rfc2440";
case CO_PGP7: return "--compliance=pgp7";
case CO_PGP8: return "--compliance=pgp8";
case CO_DE_VS: return "--compliance=de-vs";
}
log_assert (!"invalid compliance mode");
}
/* Set additional infos for example taken from config files at startup. */
void
gnupg_set_compliance_extra_info (unsigned int min_rsa)
{
min_compliant_rsa_length = min_rsa;
}
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