/*
* Copyright (C) 2013-2019 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
* Copyright (C) 2011-2013 Sourcefire, Inc.
*
* Authors: aCaB
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program 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.
*/
#if HAVE_CONFIG_H
#include "clamav-config.h"
#endif
#include "clamav.h"
#include "others.h"
#include "crtmgr.h"
#define OID_1_2_840_113549_2_5 "\x2a\x86\x48\x86\xf7\x0d\x02\x05"
#define OID_md5 OID_1_2_840_113549_2_5
#define OID_1_3_14_3_2_26 "\x2b\x0e\x03\x02\x1a"
#define OID_sha1 OID_1_3_14_3_2_26
#define OID_2_16_840_1_101_3_4_2_1 "\x60\x86\x48\x01\x65\x03\x04\x02\x01"
#define OID_sha256 OID_2_16_840_1_101_3_4_2_1
#define OID_2_16_840_1_101_3_4_2_2 "\x60\x86\x48\x01\x65\x03\x04\x02\x02"
#define OID_sha384 OID_2_16_840_1_101_3_4_2_2
#define OID_2_16_840_1_101_3_4_2_3 "\x60\x86\x48\x01\x65\x03\x04\x02\x03"
#define OID_sha512 OID_2_16_840_1_101_3_4_2_3
int cli_crt_init(cli_crt *x509)
{
int ret;
memset(x509, 0, sizeof(*x509));
if ((ret = mp_init_multi(&x509->n, &x509->e, &x509->sig, NULL))) {
cli_errmsg("cli_crt_init: mp_init_multi failed with %d\n", ret);
return 1;
}
return 0;
}
void cli_crt_clear(cli_crt *x509)
{
UNUSEDPARAM(x509);
mp_clear_multi(&x509->n, &x509->e, &x509->sig, NULL);
}
/* Look for an existing certificate in the trust store m. This search allows
* the not_before / not_after / certSign / codeSign / timeSign fields to be
* more restrictive than the values associated with a cert in the trust store,
* but not less. It's probably overkill to not do exact matching on those
* fields... TODO Is there a case where this is needed
*
* There are two ways that things get added to the whitelist - through the CRB
* rules, and through embedded signatures / catalog files that we parse. CRB
* rules don't currently allow the issuer and hashtype to be specified, so the
* code sets those to sentinel values (0xcacacaca repeating and
* CLI_HASHTYPE_ANY respectively). There are two ways we'd like to use this
* function:
*
* - To see whether x509 already exists in m (when adding new CRB sig certs
* and when adding certs that are embedded in Authenticode signatures) to
* prevent duplicate entries. In this case, we want to take x509's
* hashtype and issuer field into account, so a CRB sig cert entry isn't
* returned for an embedded cert duplicate check, and so that two embedded
* certs with different hash types or issuers aren't treated as being the
* same.
*
* - To see whether a CRB sig matches against x509, deeming it worthy to be
* added to the trust store. In this case, we don't want to compare
* hashtype and issuer, since the embedded sig will have the actual values
* and the CRB sig cert will have placeholder values.
*
* Use crb_crts_only to distinguish between the two cases. If True, it will
* ignore all crts not added from CRB rules and ignore x509's issuer and
* hashtype fields */
cli_crt *crtmgr_whitelist_lookup(crtmgr *m, cli_crt *x509, int crb_crts_only)
{
cli_crt *i;
for (i = m->crts; i; i = i->next) {
if (i->isBlacklisted) {
continue;
}
if (crb_crts_only) {
if (i->hashtype != CLI_HASHTYPE_ANY) {
continue;
}
} else {
/* Almost all of the rules in m will be CRB rules, so optimize for
* the case where we are trying to determine whether an embedded
* cert already exists in m (by checking the hashtype first). Do
* the issuer check here too to simplify the code. */
if (x509->hashtype != i->hashtype ||
memcmp(x509->issuer, i->issuer, sizeof(i->issuer))) {
continue;
}
}
if (x509->not_before >= i->not_before &&
x509->not_after <= i->not_after &&
(i->certSign | x509->certSign) == i->certSign &&
(i->codeSign | x509->codeSign) == i->codeSign &&
(i->timeSign | x509->timeSign) == i->timeSign &&
!memcmp(x509->subject, i->subject, sizeof(i->subject)) &&
!memcmp(x509->serial, i->serial, sizeof(i->serial)) &&
!mp_cmp(&x509->n, &i->n) &&
!mp_cmp(&x509->e, &i->e)) {
return i;
}
}
return NULL;
}
cli_crt *crtmgr_blacklist_lookup(crtmgr *m, cli_crt *x509)
{
cli_crt *i;
for (i = m->crts; i; i = i->next) {
// The CRB rules are based on subject, serial, and public key,
// so do blacklist queries based on those fields
// TODO the rule format specifies CodeSign / TimeSign / CertSign
// which we could also match on, but we just ignore those fields
// for blacklist certs for now
// TODO Handle the case where these items aren't specified in a CRB
// rule entry - substitute in default values instead (or make the
// crb parser not permit leaving these fields blank).
if (i->isBlacklisted &&
!memcmp(i->subject, x509->subject, sizeof(i->subject)) &&
!memcmp(i->serial, x509->serial, sizeof(i->serial)) &&
!mp_cmp(&x509->n, &i->n) &&
!mp_cmp(&x509->e, &i->e)) {
return i;
}
}
return NULL;
}
/* Determine whether x509 already exists in m. The fields compared depend on
* whether x509 is a blacklist entry or a trusted certificate */
cli_crt *crtmgr_lookup(crtmgr *m, cli_crt *x509)
{
if (x509->isBlacklisted) {
return crtmgr_blacklist_lookup(m, x509);
} else {
return crtmgr_whitelist_lookup(m, x509, 0);
}
}
int crtmgr_add(crtmgr *m, cli_crt *x509)
{
cli_crt *i;
int ret = 0;
if (x509->isBlacklisted) {
if (crtmgr_blacklist_lookup(m, x509)) {
cli_dbgmsg("crtmgr_add: duplicate blacklist entry detected - not adding\n");
return 0;
}
} else {
if (crtmgr_whitelist_lookup(m, x509, 0)) {
cli_dbgmsg("crtmgr_add: duplicate trusted certificate detected - not adding\n");
return 0;
}
}
i = cli_malloc(sizeof(*i));
if (!i)
return 1;
if ((ret = mp_init_multi(&i->n, &i->e, &i->sig, NULL))) {
cli_warnmsg("crtmgr_add: failed to mp_init failed with %d\n", ret);
free(i);
return 1;
}
if ((ret = mp_copy(&x509->n, &i->n)) || (ret = mp_copy(&x509->e, &i->e)) || (ret = mp_copy(&x509->sig, &i->sig))) {
cli_warnmsg("crtmgr_add: failed to mp_init failed with %d\n", ret);
cli_crt_clear(i);
free(i);
return 1;
}
if ((x509->name))
i->name = strdup(x509->name);
else
i->name = NULL;
memcpy(i->raw_subject, x509->raw_subject, sizeof(i->raw_subject));
memcpy(i->raw_issuer, x509->raw_issuer, sizeof(i->raw_issuer));
memcpy(i->raw_serial, x509->raw_serial, sizeof(i->raw_serial));
memcpy(i->subject, x509->subject, sizeof(i->subject));
memcpy(i->serial, x509->serial, sizeof(i->serial));
memcpy(i->issuer, x509->issuer, sizeof(i->issuer));
memcpy(i->tbshash, x509->tbshash, sizeof(i->tbshash));
i->not_before = x509->not_before;
i->not_after = x509->not_after;
i->hashtype = x509->hashtype;
i->certSign = x509->certSign;
i->codeSign = x509->codeSign;
i->timeSign = x509->timeSign;
i->isBlacklisted = x509->isBlacklisted;
i->next = m->crts;
i->prev = NULL;
if (m->crts)
m->crts->prev = i;
m->crts = i;
m->items++;
return 0;
}
void crtmgr_init(crtmgr *m)
{
m->crts = NULL;
m->items = 0;
}
void crtmgr_del(crtmgr *m, cli_crt *x509)
{
cli_crt *i;
for (i = m->crts; i; i = i->next) {
if (i == x509) {
if (i->prev)
i->prev->next = i->next;
else
m->crts = i->next;
if (i->next)
i->next->prev = i->prev;
cli_crt_clear(x509);
if ((x509->name))
free(x509->name);
free(x509);
m->items--;
return;
}
}
}
void crtmgr_free(crtmgr *m)
{
while (m->items)
crtmgr_del(m, m->crts);
}
static int crtmgr_rsa_verify(cli_crt *x509, mp_int *sig, cli_crt_hashtype hashtype, const uint8_t *refhash)
{
int keylen = mp_unsigned_bin_size(&x509->n), siglen = mp_unsigned_bin_size(sig);
int ret, j, objlen, hashlen;
uint8_t d[513];
mp_int x;
if (hashtype == CLI_SHA1RSA) {
hashlen = SHA1_HASH_SIZE;
} else if (hashtype == CLI_MD5RSA) {
hashlen = MD5_HASH_SIZE;
} else if (hashtype == CLI_SHA256RSA) {
hashlen = SHA256_HASH_SIZE;
} else if (hashtype == CLI_SHA384RSA) {
hashlen = SHA384_HASH_SIZE;
} else if (hashtype == CLI_SHA512RSA) {
hashlen = SHA512_HASH_SIZE;
} else {
cli_errmsg("crtmgr_rsa_verify: Unsupported hashtype: %d\n", hashtype);
return 1;
}
if ((ret = mp_init(&x))) {
cli_errmsg("crtmgr_rsa_verify: mp_init failed with %d\n", ret);
return 1;
}
do {
if (MAX(keylen, siglen) - MIN(keylen, siglen) > 1) {
cli_dbgmsg("crtmgr_rsa_verify: keylen and siglen differ by more than one\n");
break;
}
if ((ret = mp_exptmod(sig, &x509->e, &x509->n, &x))) {
cli_warnmsg("crtmgr_rsa_verify: verification failed: mp_exptmod failed with %d\n", ret);
break;
}
if (mp_unsigned_bin_size(&x) != keylen - 1) {
cli_dbgmsg("crtmgr_rsa_verify: keylen-1 doesn't match expected size of exptmod result\n");
break;
}
if (((unsigned int)mp_unsigned_bin_size(&x)) > sizeof(d)) {
cli_dbgmsg("crtmgr_rsa_verify: exptmod result would overrun working buffer\n");
break;
}
if ((ret = mp_to_unsigned_bin(&x, d))) {
cli_warnmsg("crtmgr_rsa_verify: mp_unsigned_bin_size failed with %d\n", ret);
break;
}
if (*d != 1) { /* block type 1 */
cli_dbgmsg("crtmgr_rsa_verify: expected block type 1 at d[0]\n");
break;
}
keylen -= 1; /* 0xff padding */
for (j = 1; j < keylen - 2; j++)
if (d[j] != 0xff)
break;
if (j == keylen - 2) {
cli_dbgmsg("crtmgr_rsa_verify: only encountered 0xFF padding parsing cert\n");
break;
}
if (d[j] != 0) { /* 0x00 separator */
cli_dbgmsg("crtmgr_rsa_verify: expected 0x00 separator\n");
break;
}
j++;
keylen -= j; /* asn1 size */
if (keylen < hashlen) {
cli_dbgmsg("crtmgr_rsa_verify: encountered keylen less than hashlen\n");
break;
}
if (keylen > hashlen) {
/* hash is asn1 der encoded */
/* SEQ { SEQ { OID, NULL }, OCTET STRING */
if (keylen < 2 || d[j] != 0x30 || d[j + 1] + 2 != keylen) {
cli_dbgmsg("crtmgr_rsa_verify: unexpected hash to be ASN1 DER encoded\n");
break;
}
keylen -= 2;
j += 2;
if (keylen < 2 || d[j] != 0x30) {
cli_dbgmsg("crtmgr_rsa_verify: expected SEQUENCE at beginning of cert AlgorithmIdentifier\n");
break;
}
objlen = d[j + 1];
keylen -= 2;
j += 2;
if (keylen < objlen) {
cli_dbgmsg("crtmgr_rsa_verify: key length mismatch in ASN1 DER hash encoding\n");
break;
}
if (objlen == 9) {
// Check for OID type indicating a length of 5, OID_sha1, and the NULL type/value
if (hashtype != CLI_SHA1RSA || memcmp(&d[j], "\x06\x05" OID_sha1 "\x05\x00", 9)) {
cli_errmsg("crtmgr_rsa_verify: FIXME ACAB - CRYPTO MISSING?\n");
break;
}
} else if (objlen == 12) {
// Check for OID type indicating a length of 8, OID_md5, and the NULL type/value
if (hashtype != CLI_MD5RSA || memcmp(&d[j], "\x06\x08" OID_md5 "\x05\x00", 12)) {
cli_errmsg("crtmgr_rsa_verify: FIXME ACAB - CRYPTO MISSING?\n");
break;
}
} else if (objlen == 13) {
if (hashtype == CLI_SHA256RSA) {
// Check for OID type indicating a length of 9, OID_sha256, and the NULL type/value
if (0 != memcmp(&d[j], "\x06\x09" OID_sha256 "\x05\x00", 13)) {
cli_dbgmsg("crtmgr_rsa_verify: invalid AlgorithmIdentifier block for SHA256 hash\n");
break;
}
} else if (hashtype == CLI_SHA384RSA) {
// Check for OID type indicating a length of 9, OID_sha384, and the NULL type/value
if (0 != memcmp(&d[j], "\x06\x09" OID_sha384 "\x05\x00", 13)) {
cli_dbgmsg("crtmgr_rsa_verify: invalid AlgorithmIdentifier block for SHA384 hash\n");
break;
}
} else if (hashtype == CLI_SHA512RSA) {
// Check for OID type indicating a length of 9, OID_sha512, and the NULL type/value
if (0 != memcmp(&d[j], "\x06\x09" OID_sha512 "\x05\x00", 13)) {
cli_dbgmsg("crtmgr_rsa_verify: invalid AlgorithmIdentifier block for SHA512 hash\n");
break;
}
} else {
cli_errmsg("crtmgr_rsa_verify: FIXME ACAB - CRYPTO MISSING?\n");
break;
}
} else {
cli_errmsg("crtmgr_rsa_verify: FIXME ACAB - CRYPTO MISSING?\n");
break;
}
keylen -= objlen;
j += objlen;
if (keylen < 2 || d[j] != 0x04 || d[j + 1] != hashlen) {
cli_dbgmsg("crtmgr_rsa_verify: hash length mismatch in ASN1 DER hash encoding\n");
break;
}
keylen -= 2;
j += 2;
if (keylen != hashlen) {
cli_dbgmsg("crtmgr_rsa_verify: extra data in the ASN1 DER hash encoding\n");
break;
}
}
if (memcmp(&d[j], refhash, hashlen)) {
// This is a common error case if we are using crtmgr_rsa_verify to
// determine whether we've found the right issuer certificate based
// (as is done by crtmgr_verify_crt). If we are pretty sure that
// x509 is the correct cert to use for verification, then this
// case is more of a concern.
break;
}
mp_clear(&x);
return 0;
} while (0);
mp_clear(&x);
return 1;
}
/* For a given cli_crt, returns a pointer to the signer x509 certificate if
* one is found in the crtmgr and it's signature can be validated (NULL is
* returned otherwise.) */
cli_crt *crtmgr_verify_crt(crtmgr *m, cli_crt *x509)
{
cli_crt *i = m->crts, *best = NULL;
int score = 0;
unsigned int possible = 0;
// Loop through each of the certificates in our trust store and see whether
// x509 is signed with it. If it is, it's trusted
// TODO Technically we should loop through all of the blacklisted certs
// first to see whether one of those is used to sign x509. This case
// will get handled if the blacklisted certificate is embedded, since we
// will call crtmgr_verify_crt on it and match against the blacklist entry
// that way, but the cert doesn't HAVE to be embedded. This case seems
// unlikely enough to ignore, though. If we ever want to blacklist a
// stolen CA cert or something, then we will need to revisit this.
for (i = m->crts; i; i = i->next) {
if (i->certSign &&
!i->isBlacklisted &&
!memcmp(i->subject, x509->issuer, sizeof(i->subject)) &&
!crtmgr_rsa_verify(i, &x509->sig, x509->hashtype, x509->tbshash)) {
int curscore;
if ((x509->codeSign & i->codeSign) == x509->codeSign && (x509->timeSign & i->timeSign) == x509->timeSign)
return i;
possible++;
curscore = (x509->codeSign & i->codeSign) + (x509->timeSign & i->timeSign);
if (curscore > score) {
best = i;
score = curscore;
}
}
}
if (possible > 1) {
// If this is ever triggered, it's probably an indication of an error
// in the CRB being used.
cli_warnmsg("crtmgr_verify_crt: choosing between codeSign cert and timeSign cert without enough info - errors may result\n");
}
return best;
}
cli_crt *crtmgr_verify_pkcs7(crtmgr *m, const uint8_t *issuer, const uint8_t *serial, const void *signature, unsigned int signature_len, cli_crt_hashtype hashtype, const uint8_t *refhash, cli_vrfy_type vrfytype)
{
cli_crt *i;
mp_int sig;
int ret;
if (signature_len < 1024 / 8 || signature_len > 4096 / 8 + 1) {
cli_dbgmsg("crtmgr_verify_pkcs7: unsupported sig len: %u\n", signature_len);
return NULL;
}
if ((ret = mp_init(&sig))) {
cli_dbgmsg("crtmgr_verify_pkcs7: mp_init failed with %d\n", ret);
return NULL;
}
if ((ret = mp_read_unsigned_bin(&sig, signature, signature_len))) {
cli_dbgmsg("crtmgr_verify_pkcs7: mp_read_unsigned_bin failed with %d\n", ret);
return NULL;
}
for (i = m->crts; i; i = i->next) {
if (vrfytype == VRFY_CODE && !i->codeSign)
continue;
if (vrfytype == VRFY_TIME && !i->timeSign)
continue;
if (!memcmp(i->issuer, issuer, sizeof(i->issuer)) &&
!memcmp(i->serial, serial, sizeof(i->serial))) {
if (!crtmgr_rsa_verify(i, &sig, hashtype, refhash)) {
break;
}
cli_dbgmsg("crtmgr_verify_pkcs7: found cert with matching issuer and serial but RSA verification failed\n");
}
}
mp_clear(&sig);
return i;
}
int crtmgr_add_roots(struct cl_engine *engine, crtmgr *m, int exclude_bl_crts)
{
cli_crt *crt;
/*
* Certs are cached in engine->cmgr. Copy from there.
*/
if (m != &(engine->cmgr)) {
for (crt = engine->cmgr.crts; crt != NULL; crt = crt->next) {
if (exclude_bl_crts && crt->isBlacklisted) {
continue;
}
if (crtmgr_add(m, crt)) {
crtmgr_free(m);
return 1;
}
}
return 0;
}
return 0;
}