source3/smbd/smb2_signing.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    SMB2 signing
   4
   5    Copyright (C) Stefan Metzmacher 2009
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19 */
  20
  21 #include "includes.h"
  22 #include "smbd/smbd.h"
  23 #include "smbd/globals.h"
  24 #include "../libcli/smb/smb_common.h"
  25 #include "../lib/crypto/crypto.h"
  26
  27 NTSTATUS smb2_signing_sign_pdu(DATA_BLOB session_key,
  28                                struct iovec *vector,
  29                                int count)
  30 {
  31         uint8_t *hdr;
  32         uint64_t session_id;
  33         struct HMACSHA256Context m;
  34         uint8_t res[SHA256_DIGEST_LENGTH];
  35         int i;
  36
  37         if (count < 2) {
  38                 return NT_STATUS_INVALID_PARAMETER;
  39         }
  40
  41         if (vector[0].iov_len != SMB2_HDR_BODY) {
  42                 return NT_STATUS_INVALID_PARAMETER;
  43         }
  44
  45         hdr = (uint8_t *)vector[0].iov_base;
  46
  47         session_id = BVAL(hdr, SMB2_HDR_SESSION_ID);
  48         if (session_id == 0) {
  49                 /*
  50                  * do not sign messages with a zero session_id.
  51                  * See MS-SMB2 3.2.4.1.1
  52                  */
  53                 return NT_STATUS_OK;
  54         }
  55
  56         if (session_key.length == 0) {
  57                 DEBUG(2,("Wrong session key length %u for SMB2 signing\n",
  58                          (unsigned)session_key.length));
  59                 return NT_STATUS_ACCESS_DENIED;
  60         }
  61
  62         memset(hdr + SMB2_HDR_SIGNATURE, 0, 16);
  63
  64         SIVAL(hdr, SMB2_HDR_FLAGS, IVAL(hdr, SMB2_HDR_FLAGS) | SMB2_HDR_FLAG_SIGNED);
  65
  66         ZERO_STRUCT(m);
  67         hmac_sha256_init(session_key.data, MIN(session_key.length, 16), &m);
  68         for (i=0; i < count; i++) {
  69                 hmac_sha256_update((const uint8_t *)vector[i].iov_base,
  70                                    vector[i].iov_len, &m);
  71         }
  72         hmac_sha256_final(res, &m);
  73         DEBUG(5,("signed SMB2 message\n"));
  74
  75         memcpy(hdr + SMB2_HDR_SIGNATURE, res, 16);
  76
  77         return NT_STATUS_OK;
  78 }
  79
  80 NTSTATUS smb2_signing_check_pdu(DATA_BLOB session_key,
  81                                 const struct iovec *vector,
  82                                 int count)
  83 {
  84         const uint8_t *hdr;
  85         const uint8_t *sig;
  86         uint64_t session_id;
  87         struct HMACSHA256Context m;
  88         uint8_t res[SHA256_DIGEST_LENGTH];
  89         static const uint8_t zero_sig[16] = { 0, };
  90         int i;
  91
  92         if (count < 2) {
  93                 return NT_STATUS_INVALID_PARAMETER;
  94         }
  95
  96         if (vector[0].iov_len != SMB2_HDR_BODY) {
  97                 return NT_STATUS_INVALID_PARAMETER;
  98         }
  99
 100         hdr = (const uint8_t *)vector[0].iov_base;
 101
 102         session_id = BVAL(hdr, SMB2_HDR_SESSION_ID);
 103         if (session_id == 0) {
 104                 /*
 105                  * do not sign messages with a zero session_id.
 106                  * See MS-SMB2 3.2.4.1.1
 107                  */
 108                 return NT_STATUS_OK;
 109         }
 110
 111         if (session_key.length == 0) {
 112                 /* we don't have the session key yet */
 113                 return NT_STATUS_OK;
 114         }
 115
 116         sig = hdr+SMB2_HDR_SIGNATURE;
 117
 118         ZERO_STRUCT(m);
 119         hmac_sha256_init(session_key.data, MIN(session_key.length, 16), &m);
 120         hmac_sha256_update(hdr, SMB2_HDR_SIGNATURE, &m);
 121         hmac_sha256_update(zero_sig, 16, &m);
 122         for (i=1; i < count; i++) {
 123                 hmac_sha256_update((const uint8_t *)vector[i].iov_base,
 124                                    vector[i].iov_len, &m);
 125         }
 126         hmac_sha256_final(res, &m);
 127
 128         if (memcmp(res, sig, 16) != 0) {
 129                 DEBUG(0,("Bad SMB2 signature for message\n"));
 130                 dump_data(0, sig, 16);
 131                 dump_data(0, res, 16);
 132                 return NT_STATUS_ACCESS_DENIED;
 133         }
 134
 135         return NT_STATUS_OK;
 136 }