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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright (c) 2009, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright 2018 Nexenta Systems, Inc. All rights reserved.
*/
/*
* Support for SMB "signing" (message integrity)
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/proc.h>
#include <sys/fcntl.h>
#include <sys/socket.h>
#include <sys/md4.h>
#include <sys/md5.h>
#include <sys/des.h>
#include <sys/kmem.h>
#include <sys/cmn_err.h>
#include <sys/stream.h>
#include <sys/strsun.h>
#include <sys/sdt.h>
#include <netsmb/smb_osdep.h>
#include <netsmb/smb.h>
#include <netsmb/smb_conn.h>
#include <netsmb/smb_subr.h>
#include <netsmb/smb_dev.h>
#include <netsmb/smb_rq.h>
#include <netsmb/smb_signing.h>
#ifdef DEBUG
/*
* Set this to a small number to debug sequence numbers
* that seem to get out of step.
*/
int nsmb_signing_fudge = 0;
#endif
/*
* This is called just after session setup completes,
* at the top of smb_iod_vc_work(). Initialize signing.
*/
int
smb_sign_init(smb_vc_t *vcp)
{
int rc;
ASSERT(vcp->vc_ssnkey != NULL);
ASSERT(vcp->vc_mackey == NULL);
rc = smb_md5_getmech(&vcp->vc_signmech);
if (rc != 0) {
cmn_err(CE_NOTE, "smb can't get signing mechanism");
return (EAUTH);
}
/*
* Convert the session key to the MAC key.
* SMB1 uses the whole session key.
*/
vcp->vc_mackeylen = vcp->vc_ssnkeylen;
vcp->vc_mackey = kmem_zalloc(vcp->vc_mackeylen, KM_SLEEP);
bcopy(vcp->vc_ssnkey, vcp->vc_mackey, vcp->vc_mackeylen);
/* The initial sequence number is two. */
vcp->vc_next_seq = 2;
return (0);
}
#define SMBSIGLEN 8 /* SMB signature length */
#define SMBSIGOFF 14 /* SMB signature offset */
/*
* Compute HMAC-MD5 of packet data, using the stored MAC key.
*
* See similar code for the server side:
* uts/common/fs/smbsrv/smb_signing.c : smb_sign_calc
*/
static int
smb_compute_MAC(struct smb_vc *vcp, mblk_t *mp,
uint32_t seqno, uchar_t *signature)
{
uchar_t digest[MD5_DIGEST_LENGTH];
smb_sign_ctx_t ctx = 0;
mblk_t *m = mp;
int size;
int rc;
/*
* This union is a little bit of trickery to:
* (1) get the sequence number int aligned, and
* (2) reduce the number of digest calls, at the
* cost of a copying 32 bytes instead of 8.
* Both sides of this union are 2+32 bytes.
*/
union {
struct {
uint8_t skip[2]; /* not used - just alignment */
uint8_t raw[SMB_HDRLEN]; /* header length (32) */
} r;
struct {
uint8_t skip[2]; /* not used - just alignment */
uint8_t hdr[SMBSIGOFF]; /* sig. offset (14) */
uint32_t sig[2]; /* MAC signature, aligned! */
uint16_t ids[5]; /* pad, Tid, Pid, Uid, Mid */
} s;
} smbhdr;
if (vcp->vc_mackey == NULL)
return (-1);
if ((rc = smb_md5_init(&ctx, &vcp->vc_signmech)) != 0)
return (rc);
/* Digest the MAC Key */
rc = smb_md5_update(ctx, vcp->vc_mackey, vcp->vc_mackeylen);
if (rc != 0)
return (rc);
/* Our caller should ensure mp has a contiguous header */
ASSERT(m != NULL);
ASSERT(MBLKL(m) >= SMB_HDRLEN);
/*
* Make an aligned copy of the SMB header,
* fill in the sequence number, and digest.
*/
size = SMB_HDRLEN;
bcopy(m->b_rptr, smbhdr.r.raw, size);
smbhdr.s.sig[0] = htolel(seqno);
smbhdr.s.sig[1] = 0;
rc = smb_md5_update(ctx, &smbhdr.r.raw, size);
if (rc != 0)
return (rc);
/*
* Digest the rest of the SMB header packet, starting at
* the data just after the SMB header.
*/
size = MBLKL(m) - SMB_HDRLEN;
rc = smb_md5_update(ctx, m->b_rptr + SMB_HDRLEN, size);
if (rc != 0)
return (rc);
m = m->b_cont;
/* Digest rest of the SMB message. */
while (m != NULL) {
size = MBLKL(m);
if (size > 0) {
rc = smb_md5_update(ctx, m->b_rptr, size);
if (rc != 0)
return (rc);
}
m = m->b_cont;
}
rc = smb_md5_final(ctx, digest);
if (rc != 0)
return (rc);
/*
* Finally, store the signature.
* (first 8 bytes of the mac)
*/
if (signature != NULL)
bcopy(digest, signature, SMBSIGLEN);
return (0);
}
/*
* Sign a request with HMAC-MD5.
*/
void
smb_rq_sign(struct smb_rq *rqp)
{
struct smb_vc *vcp = rqp->sr_vc;
mblk_t *mp = rqp->sr_rq.mb_top;
uint8_t *sigloc;
int status;
/*
* smb_rq_new() ensures this,
* but just in case..
*/
ASSERT(MBLKL(mp) >= SMB_HDRLEN);
sigloc = mp->b_rptr + SMBSIGOFF;
if (vcp->vc_mackey == NULL) {
/*
* Signing is required, but we have no key yet
* fill in with the magic fake signing value.
* This happens with SPNEGO, NTLMSSP, ...
*/
bcopy("BSRSPLY", sigloc, 8);
return;
}
/*
* This will compute the MAC and store it
* directly into the message at sigloc.
*/
status = smb_compute_MAC(vcp, mp, rqp->sr_seqno, sigloc);
if (status != 0) {
SMBSDEBUG("Crypto error %d", status);
bzero(sigloc, SMBSIGLEN);
}
}
/*
* Verify reply signature.
*/
int
smb_rq_verify(struct smb_rq *rqp)
{
struct smb_vc *vcp = rqp->sr_vc;
mblk_t *mp = rqp->sr_rp.md_top;
uint8_t sigbuf[SMBSIGLEN];
uint8_t *sigloc;
int fudge, rsn, status;
/*
* Note vc_mackey and vc_mackeylen gets filled in by
* smb_usr_iod_work as the connection comes in.
*/
if (vcp->vc_mackey == NULL) {
SMBSDEBUG("no mac key\n");
return (0);
}
/*
* Let caller deal with empty reply or short messages by
* returning zero. Caller will fail later, in parsing.
*/
if (mp == NULL) {
SMBSDEBUG("empty reply\n");
return (0);
}
ASSERT(MBLKL(mp) >= SMB_HDRLEN);
sigloc = mp->b_rptr + SMBSIGOFF;
/*
* Compute the expected signature in sigbuf.
*/
rsn = rqp->sr_rseqno;
status = smb_compute_MAC(vcp, mp, rsn, sigbuf);
if (status != 0) {
SMBSDEBUG("Crypto error %d", status);
/*
* If we can't compute a MAC, then there's
* no point trying other seqno values.
*/
return (EBADRPC);
}
/*
* Compare the computed signature with the
* one found in the message (at sigloc)
*/
if (bcmp(sigbuf, sigloc, SMBSIGLEN) == 0)
return (0);
SMBERROR("BAD signature, Server=%s MID=0x%x Seq=%d\n",
vcp->vc_srvname, rqp->sr_mid, rsn);
#ifdef DEBUG
/*
* For diag purposes, we check whether the client/server idea
* of the sequence # has gotten a bit out of sync.
*/
for (fudge = 1; fudge <= nsmb_signing_fudge; fudge++) {
(void) smb_compute_MAC(vcp, mp, rsn + fudge, sigbuf);
if (bcmp(sigbuf, sigloc, SMBSIGLEN) == 0)
break;
(void) smb_compute_MAC(vcp, mp, rsn - fudge, sigbuf);
if (bcmp(sigbuf, sigloc, SMBSIGLEN) == 0) {
fudge = -fudge;
break;
}
}
if (fudge <= nsmb_signing_fudge) {
SMBERROR("MID=0x%x, Seq=%d, but %d would have worked\n",
rqp->sr_mid, rsn, rsn + fudge);
}
#endif
return (EBADRPC);
}
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