libcli/smb/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 "system/filesys.h"
  23 #include "../libcli/smb/smb_common.h"
  24 #include "../lib/crypto/crypto.h"
  25
  26 NTSTATUS smb2_signing_sign_pdu(DATA_BLOB signing_key,
  27                                enum protocol_types protocol,
  28                                struct iovec *vector,
  29                                int count)
  30 {
  31         uint8_t *hdr;
  32         uint64_t session_id;
  33         uint8_t res[16];
  34         int i;
  35
  36         if (count < 2) {
  37                 return NT_STATUS_INVALID_PARAMETER;
  38         }
  39
  40         if (vector[0].iov_len != SMB2_HDR_BODY) {
  41                 return NT_STATUS_INVALID_PARAMETER;
  42         }
  43
  44         hdr = (uint8_t *)vector[0].iov_base;
  45
  46         session_id = BVAL(hdr, SMB2_HDR_SESSION_ID);
  47         if (session_id == 0) {
  48                 /*
  49                  * do not sign messages with a zero session_id.
  50                  * See MS-SMB2 3.2.4.1.1
  51                  */
  52                 return NT_STATUS_OK;
  53         }
  54
  55         if (signing_key.length == 0) {
  56                 DEBUG(2,("Wrong session key length %u for SMB2 signing\n",
  57                          (unsigned)signing_key.length));
  58                 return NT_STATUS_ACCESS_DENIED;
  59         }
  60
  61         memset(hdr + SMB2_HDR_SIGNATURE, 0, 16);
  62
  63         SIVAL(hdr, SMB2_HDR_FLAGS, IVAL(hdr, SMB2_HDR_FLAGS) | SMB2_HDR_FLAG_SIGNED);
  64
  65         if (protocol >= PROTOCOL_SMB2_24) {
  66                 struct aes_cmac_128_context ctx;
  67                 uint8_t key[AES_BLOCK_SIZE];
  68
  69                 ZERO_STRUCT(key);
  70                 memcpy(key, signing_key.data, MIN(signing_key.length, 16));
  71
  72                 aes_cmac_128_init(&ctx, key);
  73                 for (i=0; i < count; i++) {
  74                         aes_cmac_128_update(&ctx,
  75                                         (const uint8_t *)vector[i].iov_base,
  76                                         vector[i].iov_len);
  77                 }
  78                 aes_cmac_128_final(&ctx, res);
  79         } else {
  80                 struct HMACSHA256Context m;
  81                 uint8_t digest[SHA256_DIGEST_LENGTH];
  82
  83                 ZERO_STRUCT(m);
  84                 hmac_sha256_init(signing_key.data, MIN(signing_key.length, 16), &m);
  85                 for (i=0; i < count; i++) {
  86                         hmac_sha256_update((const uint8_t *)vector[i].iov_base,
  87                                            vector[i].iov_len, &m);
  88                 }
  89                 hmac_sha256_final(digest, &m);
  90                 memcpy(res, digest, 16);
  91         }
  92         DEBUG(5,("signed SMB2 message\n"));
  93
  94         memcpy(hdr + SMB2_HDR_SIGNATURE, res, 16);
  95
  96         return NT_STATUS_OK;
  97 }
  98
  99 NTSTATUS smb2_signing_check_pdu(DATA_BLOB signing_key,
 100                                 enum protocol_types protocol,
 101                                 const struct iovec *vector,
 102                                 int count)
 103 {
 104         const uint8_t *hdr;
 105         const uint8_t *sig;
 106         uint64_t session_id;
 107         uint8_t res[16];
 108         static const uint8_t zero_sig[16] = { 0, };
 109         int i;
 110
 111         if (count < 2) {
 112                 return NT_STATUS_INVALID_PARAMETER;
 113         }
 114
 115         if (vector[0].iov_len != SMB2_HDR_BODY) {
 116                 return NT_STATUS_INVALID_PARAMETER;
 117         }
 118
 119         hdr = (const uint8_t *)vector[0].iov_base;
 120
 121         session_id = BVAL(hdr, SMB2_HDR_SESSION_ID);
 122         if (session_id == 0) {
 123                 /*
 124                  * do not sign messages with a zero session_id.
 125                  * See MS-SMB2 3.2.4.1.1
 126                  */
 127                 return NT_STATUS_OK;
 128         }
 129
 130         if (signing_key.length == 0) {
 131                 /* we don't have the session key yet */
 132                 return NT_STATUS_OK;
 133         }
 134
 135         sig = hdr+SMB2_HDR_SIGNATURE;
 136
 137         if (protocol >= PROTOCOL_SMB2_24) {
 138                 struct aes_cmac_128_context ctx;
 139                 uint8_t key[AES_BLOCK_SIZE];
 140
 141                 ZERO_STRUCT(key);
 142                 memcpy(key, signing_key.data, MIN(signing_key.length, 16));
 143
 144                 aes_cmac_128_init(&ctx, key);
 145                 aes_cmac_128_update(&ctx, hdr, SMB2_HDR_SIGNATURE);
 146                 aes_cmac_128_update(&ctx, zero_sig, 16);
 147                 for (i=1; i < count; i++) {
 148                         aes_cmac_128_update(&ctx,
 149                                         (const uint8_t *)vector[i].iov_base,
 150                                         vector[i].iov_len);
 151                 }
 152                 aes_cmac_128_final(&ctx, res);
 153         } else {
 154                 struct HMACSHA256Context m;
 155                 uint8_t digest[SHA256_DIGEST_LENGTH];
 156
 157                 ZERO_STRUCT(m);
 158                 hmac_sha256_init(signing_key.data, MIN(signing_key.length, 16), &m);
 159                 hmac_sha256_update(hdr, SMB2_HDR_SIGNATURE, &m);
 160                 hmac_sha256_update(zero_sig, 16, &m);
 161                 for (i=1; i < count; i++) {
 162                         hmac_sha256_update((const uint8_t *)vector[i].iov_base,
 163                                            vector[i].iov_len, &m);
 164                 }
 165                 hmac_sha256_final(digest, &m);
 166                 memcpy(res, digest, 16);
 167         }
 168
 169         if (memcmp(res, sig, 16) != 0) {
 170                 DEBUG(0,("Bad SMB2 signature for message\n"));
 171                 dump_data(0, sig, 16);
 172                 dump_data(0, res, 16);
 173                 return NT_STATUS_ACCESS_DENIED;
 174         }
 175
 176         return NT_STATUS_OK;
 177 }
 178
 179 void smb2_key_derivation(const uint8_t *KI, size_t KI_len,
 180                          const uint8_t *Label, size_t Label_len,
 181                          const uint8_t *Context, size_t Context_len,
 182                          uint8_t KO[16])
 183 {
 184         struct HMACSHA256Context ctx;
 185         uint8_t buf[4];
 186         static const uint8_t zero = 0;
 187         uint8_t digest[SHA256_DIGEST_LENGTH];
 188         uint32_t i = 1;
 189         uint32_t L = 128;
 190
 191         /*
 192          * a simplified version of
 193          * "NIST Special Publication 800-108" section 5.1
 194          * using hmac-sha256.
 195          */
 196         hmac_sha256_init(KI, KI_len, &ctx);
 197
 198         RSIVAL(buf, 0, i);
 199         hmac_sha256_update(buf, sizeof(buf), &ctx);
 200         hmac_sha256_update(Label, Label_len, &ctx);
 201         hmac_sha256_update(&zero, 1, &ctx);
 202         hmac_sha256_update(Context, Context_len, &ctx);
 203         RSIVAL(buf, 0, L);
 204         hmac_sha256_update(buf, sizeof(buf), &ctx);
 205
 206         hmac_sha256_final(digest, &ctx);
 207
 208         memcpy(KO, digest, 16);
 209 }