librpc/rpc/dcerpc_helper.c

   1 /*
   2  * Copyright (c) 2020      Andreas Schneider <asn@samba.org>
   3  *
   4  * This program is free software: you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation, either version 3 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #include "includes.h"
  19 #include "librpc/gen_ndr/security.h"
  20 #include "librpc/gen_ndr/auth.h"
  21 #include "lib/crypto/gnutls_helpers.h"
  22 #include "libcli/security/dom_sid.h"
  23 #include "libcli/security/security_token.h"
  24 #include "libcli/smb/smb2_constants.h"
  25
  26 #include "dcerpc_helper.h"
  27
  28 static bool smb3_sid_parse(const struct dom_sid *sid,
  29                            uint16_t *pdialect,
  30                            uint16_t *pencrypt,
  31                            uint16_t *pcipher)
  32 {
  33         uint16_t dialect;
  34         uint16_t encrypt;
  35         uint16_t cipher;
  36
  37         if (sid->sub_auths[0] != global_sid_Samba_SMB3.sub_auths[0]) {
  38                 return false;
  39         }
  40
  41         dialect = sid->sub_auths[1];
  42         if (dialect > 0x03ff) {
  43                 return false;
  44         }
  45
  46         encrypt = sid->sub_auths[2];
  47         if (encrypt > 0x0002) {
  48                 return false;
  49         }
  50
  51         cipher = sid->sub_auths[3];
  52         if (cipher > 256) {
  53                 /*
  54                  * It is unlikely that we
  55                  * ever have more then 256
  56                  * encryption algorithms
  57                  */
  58                 return false;
  59         }
  60
  61         if (pdialect != NULL) {
  62                 *pdialect = dialect;
  63         }
  64
  65         if (pencrypt != NULL) {
  66                 *pencrypt = encrypt;
  67         }
  68
  69         if (pcipher != NULL) {
  70                 *pcipher = cipher;
  71         }
  72
  73         return true;
  74 }
  75
  76 bool dcerpc_is_transport_encrypted(struct auth_session_info *session_info)
  77 {
  78         struct security_token *token = session_info->security_token;
  79         struct dom_sid smb3_dom_sid = global_sid_Samba_SMB3;
  80         const struct dom_sid *smb3_sid = NULL;
  81         uint16_t dialect = 0;
  82         uint16_t encrypt = 0;
  83         uint16_t cipher = 0;
  84         size_t num_smb3_sids;
  85         bool ok;
  86
  87         num_smb3_sids = security_token_count_flag_sids(token,
  88                                                        &smb3_dom_sid,
  89                                                        3,
  90                                                        &smb3_sid);
  91         if (num_smb3_sids > 1) {
  92                 DBG_ERR("ERROR: The SMB3 SID has been detected %zu times\n",
  93                         num_smb3_sids);
  94                 return false;
  95         }
  96
  97         if (smb3_sid == NULL) {
  98                 return false;
  99         }
 100
 101         ok = smb3_sid_parse(smb3_sid, &dialect, &encrypt, &cipher);
 102         if (!ok) {
 103                 DBG_ERR("Failed to parse SMB3 SID!\n");
 104                 return false;
 105         }
 106
 107         DBG_DEBUG("SMB SID - dialect: %#04x, encrypt: %#04x, cipher: %#04x\n",
 108                   dialect,
 109                   encrypt,
 110                   cipher);
 111
 112         if (dialect < SMB3_DIALECT_REVISION_300) {
 113                 DBG_DEBUG("Invalid SMB3 dialect!\n");
 114                 return false;
 115         }
 116
 117         if (encrypt != DCERPC_SMB_ENCRYPTION_REQUIRED) {
 118                 DBG_DEBUG("Invalid SMB3 encryption!\n");
 119                 return false;
 120         }
 121
 122         switch (cipher) {
 123         case SMB2_ENCRYPTION_AES128_CCM:
 124         case SMB2_ENCRYPTION_AES128_GCM:
 125                 break;
 126         default:
 127                 DBG_DEBUG("Invalid SMB3 cipher!\n");
 128                 return false;
 129         }
 130
 131         return true;
 132 }