smb2_signing.c revision a90cf9f29973990687fa61de9f1f6ea22e924e40
/*
* 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) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright 2015 Nexenta Systems, Inc. All rights reserved.
*/
/*
* These routines provide the SMB MAC signing for the SMB2 server.
* The routines calculate the signature of a SMB message in an mbuf chain.
*
* The following table describes the client server
* signing registry relationship
*
* | Required | Enabled | Disabled
* -------------+---------------+------------ +--------------
* Required | Signed | Signed | Fail
* -------------+---------------+-------------+-----------------
* Enabled | Signed | Signed | Not Signed
* -------------+---------------+-------------+----------------
* Disabled | Fail | Not Signed | Not Signed
*/
#include <sys/uio.h>
#include <smbsrv/smb_kproto.h>
#include <smbsrv/smb_signing.h>
#include <sys/isa_defs.h>
#include <sys/byteorder.h>
#include <sys/cmn_err.h>
#define SMB2_SIG_OFFS 48
#define SMB2_SIG_SIZE 16
/*
* Called during session destroy.
*/
static void
smb2_sign_fini(smb_session_t *s)
{
smb_sign_mech_t *mech;
if ((mech = s->sign_mech) != NULL) {
kmem_free(mech, sizeof (*mech));
s->sign_mech = NULL;
}
}
/*
* smb2_sign_begin
*
* Get the mechanism info.
* Intializes MAC key based on the user session key and store it in
* the signing structure. This begins signing on this session.
*/
int
smb2_sign_begin(smb_request_t *sr, smb_token_t *token)
{
smb_session_t *s = sr->session;
smb_user_t *u = sr->uid_user;
struct smb_key *sign_key = &u->u_sign_key;
smb_sign_mech_t *mech;
int rc;
/*
* We should normally have a session key here because
* our caller filters out Anonymous and Guest logons.
* However, buggy clients could get us here without a
* session key, in which case we'll fail later when a
* request that requires signing can't be checked.
*/
if (token->tkn_ssnkey.val == NULL || token->tkn_ssnkey.len == 0)
return (0);
/*
* Session-level initialization (once per session)
* Get mech handle, sign_fini function.
*/
smb_rwx_rwenter(&s->s_lock, RW_WRITER);
if (s->sign_mech == NULL) {
mech = kmem_zalloc(sizeof (*mech), KM_SLEEP);
rc = smb2_hmac_getmech(mech);
if (rc != 0) {
kmem_free(mech, sizeof (*mech));
smb_rwx_rwexit(&s->s_lock);
return (rc);
}
s->sign_mech = mech;
s->sign_fini = smb2_sign_fini;
}
smb_rwx_rwexit(&s->s_lock);
/*
* Compute and store the signing key, which lives in
* the user structure.
*/
sign_key->len = SMB2_SIG_SIZE;
/*
* For SMB2, the signing key is just the first 16 bytes
* of the session key (truncated or padded with zeros).
* [MS-SMB2] 3.2.5.3.1
*/
bcopy(token->tkn_ssnkey.val, sign_key->key,
MIN(token->tkn_ssnkey.len, sign_key->len));
mutex_enter(&u->u_mutex);
if (s->secmode & SMB2_NEGOTIATE_SIGNING_ENABLED)
u->u_sign_flags |= SMB_SIGNING_ENABLED;
if (s->secmode & SMB2_NEGOTIATE_SIGNING_REQUIRED)
u->u_sign_flags |=
SMB_SIGNING_ENABLED | SMB_SIGNING_CHECK;
mutex_exit(&u->u_mutex);
/*
* If we just turned on signing, the current request
* (an SMB2 session setup) will have come in without
* SMB2_FLAGS_SIGNED (and not signed) but the response
* is is supposed to be signed. [MS-SMB2] 3.3.5.5
*/
if (u->u_sign_flags & SMB_SIGNING_ENABLED)
sr->smb2_hdr_flags |= SMB2_FLAGS_SIGNED;
return (0);
}
/*
* smb2_sign_calc
*
* Calculates MAC signature for the given buffer and returns
* it in the mac_sign parameter.
*
* The signature is in the last 16 bytes of the SMB2 header.
* The signature algorighm is to compute HMAC SHA256 over the
* entire command, with the signature field set to zeros.
*
* Return 0 if success else -1
*/
static int
smb2_sign_calc(smb_request_t *sr, struct mbuf_chain *mbc,
uint8_t *digest)
{
uint8_t tmp_hdr[SMB2_HDR_SIZE];
smb_sign_ctx_t ctx = 0;
smb_session_t *s = sr->session;
smb_user_t *u = sr->uid_user;
struct smb_key *sign_key = &u->u_sign_key;
struct mbuf *mbuf;
int offset, resid, tlen, rc;
if (s->sign_mech == NULL || sign_key->len == 0)
return (-1);
rc = smb2_hmac_init(&ctx, s->sign_mech, sign_key->key, sign_key->len);
if (rc != 0)
return (rc);
/*
* Work with a copy of the SMB2 header so we can
* clear the signature field without modifying
* the original message.
*/
tlen = SMB2_HDR_SIZE;
offset = mbc->chain_offset;
resid = mbc->max_bytes - offset;
if (smb_mbc_peek(mbc, offset, "#c", tlen, tmp_hdr) != 0)
return (-1);
bzero(tmp_hdr + SMB2_SIG_OFFS, SMB2_SIG_SIZE);
if ((rc = smb2_hmac_update(ctx, tmp_hdr, tlen)) != 0)
return (rc);
offset += tlen;
resid -= tlen;
/*
* Digest the rest of the SMB packet, starting at the data
* just after the SMB header.
*
* Advance to the src mbuf where we start digesting.
*/
mbuf = mbc->chain;
while (mbuf != NULL && (offset >= mbuf->m_len)) {
offset -= mbuf->m_len;
mbuf = mbuf->m_next;
}
if (mbuf == NULL)
return (-1);
/*
* Digest the remainder of this mbuf, limited to the
* residual count, and starting at the current offset.
* (typically SMB2_HDR_SIZE)
*/
tlen = mbuf->m_len - offset;
if (tlen > resid)
tlen = resid;
rc = smb2_hmac_update(ctx, (uint8_t *)mbuf->m_data + offset, tlen);
if (rc != 0)
return (rc);
resid -= tlen;
/*
* Digest any more mbufs in the chain.
*/
while (resid > 0) {
mbuf = mbuf->m_next;
if (mbuf == NULL)
return (-1);
tlen = mbuf->m_len;
if (tlen > resid)
tlen = resid;
rc = smb2_hmac_update(ctx, (uint8_t *)mbuf->m_data, tlen);
if (rc != 0)
return (rc);
resid -= tlen;
}
/*
* Note: digest is _always_ SMB2_SIG_SIZE,
* even if the mech uses a longer one.
*/
if ((rc = smb2_hmac_final(ctx, digest)) != 0)
return (rc);
return (0);
}
/*
* smb2_sign_check_request
*
* Calculates MAC signature for the request mbuf chain
* using the next expected sequence number and compares
* it to the given signature.
*
* Note it does not check the signature for secondary transactions
* as their sequence number is the same as the original request.
*
* Return 0 if the signature verifies, otherwise, returns -1;
*
*/
int
smb2_sign_check_request(smb_request_t *sr)
{
uint8_t req_sig[SMB2_SIG_SIZE];
uint8_t vfy_sig[SMB2_SIG_SIZE];
struct mbuf_chain *mbc = &sr->smb_data;
smb_user_t *u = sr->uid_user;
int sig_off;
/*
* Don't check commands with a zero session ID.
* [MS-SMB2] 3.3.4.1.1
*/
if (sr->smb_uid == 0 || u == NULL)
return (0);
/* Get the request signature. */
sig_off = sr->smb2_cmd_hdr + SMB2_SIG_OFFS;
if (smb_mbc_peek(mbc, sig_off, "#c", SMB2_SIG_SIZE, req_sig) != 0)
return (-1);
/*
* Compute the correct signature and compare.
*/
if (smb2_sign_calc(sr, mbc, vfy_sig) != 0)
return (-1);
if (memcmp(vfy_sig, req_sig, SMB2_SIG_SIZE) != 0) {
cmn_err(CE_NOTE, "smb2_sign_check_request: bad signature");
return (-1);
}
return (0);
}
/*
* smb2_sign_reply
*
* Calculates MAC signature for the given mbuf chain,
* and write it to the signature field in the mbuf.
*
*/
void
smb2_sign_reply(smb_request_t *sr)
{
uint8_t reply_sig[SMB2_SIG_SIZE];
struct mbuf_chain tmp_mbc;
smb_user_t *u = sr->uid_user;
int hdr_off, msg_len;
if (u == NULL)
return;
msg_len = sr->reply.chain_offset - sr->smb2_reply_hdr;
(void) MBC_SHADOW_CHAIN(&tmp_mbc, &sr->reply,
sr->smb2_reply_hdr, msg_len);
/*
* Calculate the MAC signature for this reply.
*/
if (smb2_sign_calc(sr, &tmp_mbc, reply_sig) != 0)
return;
/*
* Poke the signature into the response.
*/
hdr_off = sr->smb2_reply_hdr + SMB2_SIG_OFFS;
(void) smb_mbc_poke(&sr->reply, hdr_off, "#c",
SMB2_SIG_SIZE, reply_sig);
}