1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21 /*
22 * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
23 * Copyright 2015 Nexenta Systems, Inc. All rights reserved.
24 */
25 /*
26 * These routines provide the SMB MAC signing for the SMB server.
27 * The routines calculate the signature of a SMB message in an mbuf chain.
28 *
29 * The following table describes the client server
30 * signing registry relationship
31 *
32 * | Required | Enabled | Disabled
33 * -------------+---------------+------------ +--------------
34 * Required | Signed | Signed | Fail
35 * -------------+---------------+-------------+-----------------
36 * Enabled | Signed | Signed | Not Signed
37 * -------------+---------------+-------------+----------------
38 * Disabled | Fail | Not Signed | Not Signed
39 */
40
41 #include <sys/uio.h>
42 #include <smbsrv/smb_kproto.h>
43 #include <smbsrv/smb_signing.h>
44 #include <sys/isa_defs.h>
45 #include <sys/byteorder.h>
46
47 #define SMB_SIG_SIZE 8
48 #define SMB_SIG_OFFS 14
49 #define SMB_HDRLEN 32
50
51 #ifdef _LITTLE_ENDIAN
52 #define htolel(x) ((uint32_t)(x))
53 #else
54 #define htolel(x) BSWAP_32(x)
55 #endif
56
57 static int
58 smb_sign_calc(smb_request_t *sr, struct mbuf_chain *mbc,
59 uint32_t seqnum, unsigned char *sig);
60
61 #ifdef DEBUG
62 uint32_t smb_sign_debug_search = 10;
63
64 /*
65 * Debug code to search +/- for the correct sequence number.
66 * If found, correct sign->seqnum and return 0, else return -1
67 */
68 static int
69 smb_sign_find_seqnum(
70 smb_request_t *sr,
71 struct mbuf_chain *mbc,
72 unsigned char *mac_sig,
73 unsigned char *sr_sig)
74 {
75 struct smb_sign *sign = &sr->session->signing;
76 uint32_t i, t;
77
78 for (i = 1; i < smb_sign_debug_search; i++) {
79 t = sr->sr_seqnum + i;
80 (void) smb_sign_calc(sr, mbc, t, mac_sig);
81 if (memcmp(mac_sig, sr_sig, SMB_SIG_SIZE) == 0) {
82 goto found;
83 }
84 t = sr->sr_seqnum - i;
85 (void) smb_sign_calc(sr, mbc, t, mac_sig);
86 if (memcmp(mac_sig, sr_sig, SMB_SIG_SIZE) == 0) {
87 goto found;
88 }
89 }
90 cmn_err(CE_WARN, "smb_sign_find_seqnum: failed after %d", i);
91 return (-1);
92
93 found:
94 cmn_err(CE_WARN, "smb_sign_find_seqnum: found! %d <- %d",
95 sign->seqnum, t);
96 sign->seqnum = t;
97 return (0);
98 }
99 #endif
100
101 /*
102 * Called during session destroy.
103 */
104 static void
105 smb_sign_fini(smb_session_t *s)
106 {
107 smb_sign_mech_t *mech;
108
109 if ((mech = s->sign_mech) != NULL) {
110 kmem_free(mech, sizeof (*mech));
111 s->sign_mech = NULL;
112 }
113 }
114
115 /*
116 * smb_sign_begin
117 *
118 * Intializes MAC key based on the user session key and
119 * NTLM response and store it in the signing structure.
120 * This is what begins SMB signing.
121 */
122 int
123 smb_sign_begin(smb_request_t *sr, smb_token_t *token)
124 {
125 smb_arg_sessionsetup_t *sinfo = sr->sr_ssetup;
126 smb_session_t *session = sr->session;
127 struct smb_sign *sign = &session->signing;
128 smb_sign_mech_t *mech;
129 int rc;
130
131 /*
132 * We should normally have a session key here because
133 * our caller filters out Anonymous and Guest logons.
134 * However, buggy clients could get us here without a
135 * session key, in which case: just don't sign.
136 */
137 if (token->tkn_ssnkey.val == NULL || token->tkn_ssnkey.len == 0)
138 return (0);
139
140 /*
141 * Session-level initialization (once per session)
142 */
143 smb_rwx_rwenter(&session->s_lock, RW_WRITER);
144
145 /*
146 * Signing may already have been setup by a prior logon,
147 * in which case we're done here.
148 */
149 if (sign->mackey != NULL) {
150 smb_rwx_rwexit(&session->s_lock);
151 return (0);
152 }
153
154 /*
155 * Get the mech handle
156 */
157 if (session->sign_mech == NULL) {
158 mech = kmem_zalloc(sizeof (*mech), KM_SLEEP);
159 rc = smb_md5_getmech(mech);
160 if (rc != 0) {
161 kmem_free(mech, sizeof (*mech));
162 smb_rwx_rwexit(&session->s_lock);
163 return (rc);
164 }
165 session->sign_mech = mech;
166 session->sign_fini = smb_sign_fini;
167 }
168
169 /*
170 * Compute and store the signing (MAC) key.
171 *
172 * With extended security, the MAC key is the same as the
173 * session key (and we'll have sinfo->ssi_ntpwlen == 0).
174 * With non-extended security, it's the concatenation of
175 * the session key and the "NT response" we received.
176 */
177 sign->mackey_len = token->tkn_ssnkey.len + sinfo->ssi_ntpwlen;
178 sign->mackey = kmem_alloc(sign->mackey_len, KM_SLEEP);
179 bcopy(token->tkn_ssnkey.val, sign->mackey, token->tkn_ssnkey.len);
180 if (sinfo->ssi_ntpwlen > 0) {
181 bcopy(sinfo->ssi_ntpwd, sign->mackey + token->tkn_ssnkey.len,
182 sinfo->ssi_ntpwlen);
183 }
184
185 session->signing.seqnum = 0;
186 sr->sr_seqnum = 2;
187 sr->reply_seqnum = 1;
188 sign->flags = 0;
189
190 if (session->secmode & NEGOTIATE_SECURITY_SIGNATURES_ENABLED) {
191 sign->flags |= SMB_SIGNING_ENABLED;
192 if (session->secmode & NEGOTIATE_SECURITY_SIGNATURES_REQUIRED)
193 sign->flags |= SMB_SIGNING_CHECK;
194 }
195
196 smb_rwx_rwexit(&session->s_lock);
197 return (0);
198 }
199
200 /*
201 * smb_sign_calc
202 *
203 * Calculates MAC signature for the given buffer and returns
204 * it in the mac_sign parameter.
205 *
206 * The sequence number is placed in the first four bytes of the signature
207 * field of the signature and the other 4 bytes are zeroed.
208 * The signature is the first 8 bytes of the MD5 result of the
209 * concatenated MAC key and the SMB message.
210 *
211 * MACsig = head(MD5(concat(MACKey, SMBMsg)), 8)
212 *
213 * where
214 *
215 * MACKey = concat( UserSessionKey, NTLMResp )
216 *
217 * and
218 *
219 * SMBMsg is the SMB message containing the sequence number.
220 *
221 * Return 0 if success
222 *
223 */
224 static int
225 smb_sign_calc(smb_request_t *sr, struct mbuf_chain *mbc,
226 uint32_t seqnum, unsigned char *mac_sign)
227 {
228 smb_session_t *s = sr->session;
229 struct smb_sign *sign = &s->signing;
230 smb_sign_ctx_t ctx = 0;
231 uchar_t digest[MD5_DIGEST_LENGTH];
232 uchar_t *hdrp;
233 struct mbuf *mbuf = mbc->chain;
234 int offset = mbc->chain_offset;
235 int size;
236 int rc;
237
238 /*
239 * This union is a little bit of trickery to:
240 * (1) get the sequence number int aligned, and
241 * (2) reduce the number of digest calls, at the
242 * cost of a copying 32 bytes instead of 8.
243 * Both sides of this union are 2+32 bytes.
244 */
245 union {
246 struct {
247 uint8_t skip[2]; /* not used - just alignment */
248 uint8_t raw[SMB_HDRLEN]; /* header length (32) */
249 } r;
250 struct {
251 uint8_t skip[2]; /* not used - just alignment */
252 uint8_t hdr[SMB_SIG_OFFS]; /* sig. offset (14) */
253 uint32_t sig[2]; /* MAC signature, aligned! */
254 uint16_t ids[5]; /* pad, Tid, Pid, Uid, Mid */
255 } s;
256 } smbhdr;
257
258 if (s->sign_mech == NULL || sign->mackey == NULL)
259 return (-1);
260
261 if ((rc = smb_md5_init(&ctx, s->sign_mech)) != 0)
262 return (rc);
263
264 /* Digest the MAC Key */
265 rc = smb_md5_update(ctx, sign->mackey, sign->mackey_len);
266 if (rc != 0)
267 return (rc);
268
269 /*
270 * Make an aligned copy of the SMB header,
271 * fill in the sequence number, and digest.
272 */
273 hdrp = (unsigned char *)&smbhdr.r.raw;
274 size = SMB_HDRLEN;
275 if (smb_mbc_peek(mbc, offset, "#c", size, hdrp) != 0)
276 return (-1);
277 smbhdr.s.sig[0] = htolel(seqnum);
278 smbhdr.s.sig[1] = 0;
279
280 rc = smb_md5_update(ctx, &smbhdr.r.raw, size);
281 if (rc != 0)
282 return (rc);
283
284 /*
285 * Digest the rest of the SMB packet, starting at the data
286 * just after the SMB header.
287 */
288 offset += size;
289 while (mbuf != NULL && (offset >= mbuf->m_len)) {
290 offset -= mbuf->m_len;
291 mbuf = mbuf->m_next;
292 }
293 if (mbuf != NULL && (size = (mbuf->m_len - offset)) > 0) {
294 rc = smb_md5_update(ctx, &mbuf->m_data[offset], size);
295 if (rc != 0)
296 return (rc);
297 offset = 0;
298 mbuf = mbuf->m_next;
299 }
300 while (mbuf != NULL) {
301 rc = smb_md5_update(ctx, mbuf->m_data, mbuf->m_len);
302 if (rc != 0)
303 return (rc);
304 mbuf = mbuf->m_next;
305 }
306 rc = smb_md5_final(ctx, digest);
307 if (rc == 0)
308 bcopy(digest, mac_sign, SMB_SIG_SIZE);
309
310 return (rc);
311 }
312
313
314 /*
315 * smb_sign_check_request
316 *
317 * Calculates MAC signature for the request mbuf chain
318 * using the next expected sequence number and compares
319 * it to the given signature.
320 *
321 * Note it does not check the signature for secondary transactions
322 * as their sequence number is the same as the original request.
323 *
324 * Return 0 if the signature verifies, otherwise, returns -1;
325 *
326 */
327 int
328 smb_sign_check_request(smb_request_t *sr)
329 {
330 struct mbuf_chain mbc = sr->command;
331 unsigned char mac_sig[SMB_SIG_SIZE];
332
333 /*
334 * Don't check secondary transactions - we dont know the sequence
335 * number.
336 */
337 if (sr->smb_com == SMB_COM_TRANSACTION_SECONDARY ||
338 sr->smb_com == SMB_COM_TRANSACTION2_SECONDARY ||
339 sr->smb_com == SMB_COM_NT_TRANSACT_SECONDARY)
340 return (0);
341
342 /* Reset the offset to begining of header */
343 mbc.chain_offset = sr->orig_request_hdr;
344
345 /* calculate mac signature */
346 if (smb_sign_calc(sr, &mbc, sr->sr_seqnum, mac_sig) != 0)
347 return (-1);
348
349 /* compare the signatures */
350 if (memcmp(mac_sig, sr->smb_sig, SMB_SIG_SIZE) == 0) {
351 /* They match! OK, we're done. */
352 return (0);
353 }
354
355 DTRACE_PROBE2(smb__signature__mismatch, smb_request_t, sr,
356 unsigned char *, mac_sig);
357 cmn_err(CE_NOTE, "smb_sign_check_request: bad signature");
358
359 /*
360 * check nearby sequence numbers in debug mode
361 */
362 #ifdef DEBUG
363 if (smb_sign_debug) {
364 return (smb_sign_find_seqnum(sr, &mbc, mac_sig, sr->smb_sig));
365 }
366 #endif
367 return (-1);
368 }
369
370 /*
371 * smb_sign_check_secondary
372 *
373 * Calculates MAC signature for the secondary transaction mbuf chain
374 * and compares it to the given signature.
375 * Return 0 if the signature verifies, otherwise, returns -1;
376 *
377 */
378 int
379 smb_sign_check_secondary(smb_request_t *sr, unsigned int reply_seqnum)
380 {
381 struct mbuf_chain mbc = sr->command;
382 unsigned char mac_sig[SMB_SIG_SIZE];
383 int rtn = 0;
384
385 /* Reset the offset to begining of header */
386 mbc.chain_offset = sr->orig_request_hdr;
387
388 /* calculate mac signature */
389 if (smb_sign_calc(sr, &mbc, reply_seqnum - 1, mac_sig) != 0)
390 return (-1);
391
392
393 /* compare the signatures */
394 if (memcmp(mac_sig, sr->smb_sig, SMB_SIG_SIZE) != 0) {
395 cmn_err(CE_WARN, "SmbSignCheckSecond: bad signature");
396 rtn = -1;
397 }
398 /* Save the reply sequence number */
399 sr->reply_seqnum = reply_seqnum;
400
401 return (rtn);
402 }
403
404 /*
405 * smb_sign_reply
406 *
407 * Calculates MAC signature for the given mbuf chain,
408 * and write it to the signature field in the mbuf.
409 *
410 */
411 void
412 smb_sign_reply(smb_request_t *sr, struct mbuf_chain *reply)
413 {
414 struct mbuf_chain mbc;
415 unsigned char mac[SMB_SIG_SIZE];
416
417 if (reply)
418 mbc = *reply;
419 else
420 mbc = sr->reply;
421
422 /* Reset offset to start of reply */
423 mbc.chain_offset = 0;
424
425 /*
426 * Calculate MAC signature
427 */
428 if (smb_sign_calc(sr, &mbc, sr->reply_seqnum, mac) != 0) {
429 cmn_err(CE_WARN, "smb_sign_reply: error in smb_sign_calc");
430 return;
431 }
432
433 /*
434 * Put signature in the response
435 */
436 (void) smb_mbc_poke(&mbc, SMB_SIG_OFFS, "#c",
437 SMB_SIG_SIZE, mac);
438 }