Add support for SMB request signing, which prevents "man in the middle"

attacks and is required to connect to Windows 2003 servers in their
default configuration. This adds an extra field to the SMB header
containing the truncated 64-bit MD5 digest of a key (a function of the
user's password and the server's authentication challenge), an implicit
sequence number, and the message data itself. As signing each message
imposes a significant performance penalty, we only enable it if the
server will not let us connect without it; this should eventually become
an option to mount_smbfs.

8 files changed, 249 insertions, 12 deletions

diff --git a/sys/netsmb/smb_conn.c b/sys/netsmb/smb_conn.c
index 23eb4be..7ea63ee 100644
--- a/sys/netsmb/smb_conn.c
+++ b/sys/netsmb/smb_conn.c
@@ -405,6 +405,9 @@ smb_vc_create(struct smb_vcspec *vcspec,
 	vcp->vc_mode = vcspec->rights & SMBM_MASK;
 	vcp->obj.co_flags = vcspec->flags & (SMBV_PRIVATE | SMBV_SINGLESHARE);
 	vcp->vc_tdesc = &smb_tran_nbtcp_desc;
+	vcp->vc_seqno = 0;
+	vcp->vc_mackey = NULL;
+	vcp->vc_mackeylen = 0;
 
 	if (uid == SMBM_ANY_OWNER)
 		uid = realuid;
@@ -474,6 +477,8 @@ smb_vc_free(struct smb_connobj *cp)
 	SMB_STRFREE(vcp->vc_srvname);
 	SMB_STRFREE(vcp->vc_pass);
 	SMB_STRFREE(vcp->vc_domain);
+	if (vcp->vc_mackey)
+		free(vcp->vc_mackey, M_SMBTEMP);
 	if (vcp->vc_paddr)
 		free(vcp->vc_paddr, M_SONAME);
 	if (vcp->vc_laddr)
diff --git a/sys/netsmb/smb_conn.h b/sys/netsmb/smb_conn.h
index 70f43e1..4092dcb 100644
--- a/sys/netsmb/smb_conn.h
+++ b/sys/netsmb/smb_conn.h
@@ -268,6 +268,9 @@ struct smb_vc {
 	int		vc_wxmax;	/* max writex data size */
 	struct smbiod *	vc_iod;
 	struct smb_slock vc_stlock;
+	u_int32_t	vc_seqno;	/* my next sequence number */
+	u_int8_t	*vc_mackey;	/* MAC key */
+	int		vc_mackeylen;	/* length of MAC key */
 };
 
 #define vc_maxmux	vc_sopt.sv_maxmux
diff --git a/sys/netsmb/smb_crypt.c b/sys/netsmb/smb_crypt.c
index 6695d57..9d01217 100644
--- a/sys/netsmb/smb_crypt.c
+++ b/sys/netsmb/smb_crypt.c
@@ -2,6 +2,9 @@
  * Copyright (c) 2000-2001, Boris Popov
  * All rights reserved.
  *
+ * Copyright (c) 2003, 2004 Tim J. Robbins.
+ * All rights reserved.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ -43,13 +46,17 @@ __FBSDID("$FreeBSD$");
 #include <sys/socket.h>
 #include <sys/socketvar.h>
 #include <sys/sysctl.h>
-
+#include <sys/endian.h>
+#include <sys/mbuf.h>
+#include <sys/mchain.h>
 #include <sys/md4.h>
+#include <sys/md5.h>
 #include <sys/iconv.h>
 
 #include <netsmb/smb.h>
 #include <netsmb/smb_conn.h>
 #include <netsmb/smb_subr.h>
+#include <netsmb/smb_rq.h>
 #include <netsmb/smb_dev.h>
 
 #include "opt_netsmb.h"
@@ -146,3 +153,187 @@ smb_ntencrypt(const u_char *apwd, u_char *C8, u_char *RN)
 #endif
 }
 
+/*
+ * Calculate message authentication code (MAC) key for virtual circuit.
+ */
+int
+smb_calcmackey(struct smb_vc *vcp)
+{
+#ifdef NETSMBCRYPTO
+	const char *pwd;
+	u_int16_t *unipwd;
+	int len;
+	MD4_CTX md4;
+	u_char S16[16], S21[21];
+
+	KASSERT(vcp->vc_hflags2 & SMB_FLAGS2_SECURITY_SIGNATURE,
+	    ("signatures not enabled"));
+
+	if (vcp->vc_mackey != NULL) {
+		free(vcp->vc_mackey, M_SMBTEMP);
+		vcp->vc_mackey = NULL;
+		vcp->vc_mackeylen = 0;
+		vcp->vc_seqno = 0;
+	}
+
+	/*
+	 * The partial MAC key is the concatenation of the 16 byte session
+	 * key and the 24 byte challenge response.
+	 */
+	vcp->vc_mackeylen = 16 + 24;
+	vcp->vc_mackey = malloc(vcp->vc_mackeylen, M_SMBTEMP, M_WAITOK);
+
+	/*
+	 * Calculate session key:
+	 *	MD4(MD4(U(PN)))
+	 */
+	pwd = smb_vc_getpass(vcp);
+	len = strlen(pwd);
+	unipwd = malloc((len + 1) * sizeof(u_int16_t), M_SMBTEMP, M_WAITOK);
+	smb_strtouni(unipwd, pwd);
+	MD4Init(&md4);
+	MD4Update(&md4, (u_char *)unipwd, len * sizeof(u_int16_t));
+	MD4Final(S16, &md4);
+	MD4Init(&md4);
+	MD4Update(&md4, S16, 16);
+	MD4Final(vcp->vc_mackey, &md4);
+	free(unipwd, M_SMBTEMP);
+
+	/*
+	 * Calculate response to challenge:
+	 *	Ex(concat(MD4(U(pass)), zeros(5)), C8)
+	 */
+	bzero(S21, 21);
+	bcopy(S16, S21, 16);
+	smb_E(S21, vcp->vc_ch, vcp->vc_mackey + 16);
+	smb_E(S21 + 7, vcp->vc_ch, vcp->vc_mackey + 24);
+	smb_E(S21 + 14, vcp->vc_ch, vcp->vc_mackey + 32);
+
+	return (0);
+#else
+	panic("smb_calcmackey: encryption not available");
+	return (0);
+#endif	/* NETSMBCRYPTO */
+}
+
+/*
+ * Sign request with MAC.
+ */
+int
+smb_rq_sign(struct smb_rq *rqp)
+{
+#ifdef NETSMBCRYPTO
+	struct smb_vc *vcp = rqp->sr_vc;
+	struct mbchain *mbp;
+	struct mbuf *mb;
+	MD5_CTX md5;
+	u_char digest[16];
+
+	KASSERT(vcp->vc_hflags2 & SMB_FLAGS2_SECURITY_SIGNATURE,
+	    ("signatures not enabled"));
+
+	if (vcp->vc_mackey == NULL)
+		/* XXX Should assert that cmd == SMB_COM_NEGOTIATE. */
+		return (0);
+
+	/*
+	 * This is a bit of a kludge. If the request is non-TRANSACTION,
+	 * or it is the first request of a transaction, give it the next
+	 * sequence number, and expect the reply to have the sequence number
+	 * following that one. Otherwise, it is a secondary request in
+	 * a transaction, and it gets the same sequence numbers as the
+	 * primary request.
+	 */
+	if (rqp->sr_t2 == NULL ||
+	    (rqp->sr_t2->t2_flags & SMBT2_SECONDARY) == 0) {
+		rqp->sr_seqno = vcp->vc_seqno++;
+		rqp->sr_rseqno = vcp->vc_seqno++;
+	} else {
+		/*
+		 * Sequence numbers are already in the struct because
+		 * smb_t2_request_int() uses the same one for all the
+		 * requests in the transaction.
+		 * (At least we hope so.)
+		 */
+		KASSERT(rqp->sr_t2 == NULL ||
+		    (rqp->sr_t2->t2_flags & SMBT2_SECONDARY) == 0 ||
+		    rqp->sr_t2->t2_rq == rqp,
+		    ("sec t2 rq not using same smb_rq"));
+	}
+
+	/* Initialize sec. signature field to sequence number + zeros. */
+	*(u_int32_t *)rqp->sr_rqsig = htole32(rqp->sr_seqno);
+	*(u_int32_t *)(rqp->sr_rqsig + 4) = 0;
+
+	/*
+	 * Compute HMAC-MD5 of packet data, keyed by MAC key.
+	 * Store the first 8 bytes in the sec. signature field.
+	 */
+	smb_rq_getrequest(rqp, &mbp);
+	MD5Init(&md5);
+	MD5Update(&md5, vcp->vc_mackey, vcp->vc_mackeylen);
+	for (mb = mbp->mb_top; mb != NULL; mb = mb->m_next)
+		MD5Update(&md5, mtod(mb, void *), mb->m_len);
+	MD5Final(digest, &md5);
+	bcopy(digest, rqp->sr_rqsig, 8);
+
+	return (0);
+#else
+	panic("smb_rq_sign: encryption not available");
+	return (0);
+#endif	/* NETSMBCRYPTO */
+}
+
+/*
+ * Verify reply signature.
+ */
+int
+smb_rq_verify(struct smb_rq *rqp)
+{
+#ifdef NETSMBCRYPTO
+	struct smb_vc *vcp = rqp->sr_vc;
+	struct mdchain *mdp;
+	u_char sigbuf[8];
+	MD5_CTX md5;
+	u_char digest[16];
+	struct mbuf *mb;
+
+	KASSERT(vcp->vc_hflags2 & SMB_FLAGS2_SECURITY_SIGNATURE,
+	    ("signatures not enabled"));
+
+	if (vcp->vc_mackey == NULL)
+		/* XXX Should check that this is a SMB_COM_NEGOTIATE reply. */
+		return (0);
+
+	/*
+	 * Compute HMAC-MD5 of packet data, keyed by MAC key.
+	 * We play games to pretend the security signature field
+	 * contains their sequence number, to avoid modifying
+	 * the packet itself.
+	 */
+	smb_rq_getreply(rqp, &mdp);
+	mb = mdp->md_top;
+	KASSERT(mb->m_len >= SMB_HDRLEN, ("forgot to m_pullup"));
+	MD5Init(&md5);
+	MD5Update(&md5, vcp->vc_mackey, vcp->vc_mackeylen);
+	MD5Update(&md5, mtod(mb, void *), 14);
+	*(u_int32_t *)sigbuf = htole32(rqp->sr_rseqno);
+	*(u_int32_t *)(sigbuf + 4) = 0;
+	MD5Update(&md5, sigbuf, 8);
+	MD5Update(&md5, mtod(mb, u_char *) + 22, mb->m_len - 22);
+	for (mb = mb->m_next; mb != NULL; mb = mb->m_next)
+		MD5Update(&md5, mtod(mb, void *), mb->m_len);
+	MD5Final(digest, &md5);
+
+	/*
+	 * Now verify the signature.
+	 */
+	if (bcmp(mtod(mdp->md_top, u_char *) + 14, digest, 8) != 0)
+		return (EAUTH);
+
+	return (0);
+#else
+	panic("smb_rq_verify: encryption not available");
+	return (0);
+#endif	/* NETSMBCRYPTO */
+}
diff --git a/sys/netsmb/smb_iod.c b/sys/netsmb/smb_iod.c
index ae9c457..e2abac5 100644
--- a/sys/netsmb/smb_iod.c
+++ b/sys/netsmb/smb_iod.c
@@ -247,6 +247,8 @@ smb_iod_sendrq(struct smbiod *iod, struct smb_rq *rqp)
 		*rqp->sr_rqtid = htole16(ssp ? ssp->ss_tid : SMB_TID_UNKNOWN);
 		*rqp->sr_rquid = htole16(vcp ? vcp->vc_smbuid : 0);
 		mb_fixhdr(&rqp->sr_rq);
+		if (vcp->vc_hflags2 & SMB_FLAGS2_SECURITY_SIGNATURE)
+			smb_rq_sign(rqp);
 	}
 	if (rqp->sr_sendcnt++ > 5) {
 		rqp->sr_flags |= SMBR_RESTART;
diff --git a/sys/netsmb/smb_rq.c b/sys/netsmb/smb_rq.c
index c507cac..03c7eb6 100644
--- a/sys/netsmb/smb_rq.c
+++ b/sys/netsmb/smb_rq.c
@@ -114,6 +114,7 @@ smb_rq_new(struct smb_rq *rqp, u_char cmd)
 	struct smb_vc *vcp = rqp->sr_vc;
 	struct mbchain *mbp = &rqp->sr_rq;
 	int error;
+	u_int16_t flags2;
 
 	rqp->sr_sendcnt = 0;
 	mb_done(mbp);
@@ -125,11 +126,20 @@ smb_rq_new(struct smb_rq *rqp, u_char cmd)
 	mb_put_uint8(mbp, cmd);
 	mb_put_uint32le(mbp, 0);		/* DosError */
 	mb_put_uint8(mbp, vcp->vc_hflags);
+	flags2 = vcp->vc_hflags2;
 	if (cmd == SMB_COM_TRANSACTION || cmd == SMB_COM_TRANSACTION_SECONDARY)
-		mb_put_uint16le(mbp, (vcp->vc_hflags2 & ~SMB_FLAGS2_UNICODE));
-	else
-		mb_put_uint16le(mbp, vcp->vc_hflags2);
-	mb_put_mem(mbp, tzero, 12, MB_MSYSTEM);
+		flags2 &= ~SMB_FLAGS2_UNICODE;
+	if (cmd == SMB_COM_NEGOTIATE)
+		flags2 &= ~SMB_FLAGS2_SECURITY_SIGNATURE;
+	mb_put_uint16le(mbp, flags2);
+	if ((flags2 & SMB_FLAGS2_SECURITY_SIGNATURE) == 0) {
+		mb_put_mem(mbp, tzero, 12, MB_MSYSTEM);
+		rqp->sr_rqsig = NULL;
+	} else {
+		mb_put_uint16le(mbp, 0 /*scred->sc_p->p_pid >> 16*/);
+		rqp->sr_rqsig = (u_int8_t *)mb_reserve(mbp, 8);
+		mb_put_uint16le(mbp, 0);
+	}
 	rqp->sr_rqtid = (u_int16_t*)mb_reserve(mbp, sizeof(u_int16_t));
 	mb_put_uint16le(mbp, 1 /*scred->sc_p->p_pid & 0xffff*/);
 	rqp->sr_rquid = (u_int16_t*)mb_reserve(mbp, sizeof(u_int16_t));
@@ -349,6 +359,10 @@ smb_rq_reply(struct smb_rq *rqp)
 	error = md_get_uint16le(mdp, &rqp->sr_rpuid);
 	error = md_get_uint16le(mdp, &rqp->sr_rpmid);
 
+	if (error == 0 &&
+	    (rqp->sr_vc->vc_hflags2 & SMB_FLAGS2_SECURITY_SIGNATURE))
+		error = smb_rq_verify(rqp);
+
 	SMBSDEBUG("M:%04x, P:%04x, U:%04x, T:%04x, E: %d:%d\n",
 	    rqp->sr_rpmid, rqp->sr_rppid, rqp->sr_rpuid, rqp->sr_rptid,
 	    rqp->sr_errclass, rqp->sr_serror);
@@ -575,6 +589,7 @@ smb_t2_request_int(struct smb_t2rq *t2p)
 		return error;
 	rqp->sr_flags |= SMBR_MULTIPACKET;
 	t2p->t2_rq = rqp;
+	rqp->sr_t2 = t2p;
 	mbp = &rqp->sr_rq;
 	smb_rq_wstart(rqp);
 	mb_put_uint16le(mbp, totpcount);
@@ -649,6 +664,7 @@ smb_t2_request_int(struct smb_t2rq *t2p)
 	if (error)
 		goto bad;
 	while (leftpcount || leftdcount) {
+		t2p->t2_flags |= SMBT2_SECONDARY;
 		error = smb_rq_new(rqp, t2p->t_name ? 
 		    SMB_COM_TRANSACTION_SECONDARY : SMB_COM_TRANSACTION2_SECONDARY);
 		if (error)
diff --git a/sys/netsmb/smb_rq.h b/sys/netsmb/smb_rq.h
index 7d99fea..8cdc1f6 100644
--- a/sys/netsmb/smb_rq.h
+++ b/sys/netsmb/smb_rq.h
@@ -54,6 +54,7 @@
 #define	SMBT2_ALLOCED		0x0004
 #define	SMBT2_RESTART		0x0008
 #define	SMBT2_NORESTART		0x0010
+#define	SMBT2_SECONDARY		0x0020	/* secondary request */
 
 #define SMBRQ_SLOCK(rqp)	smb_sl_lock(&(rqp)->sr_slock)
 #define SMBRQ_SUNLOCK(rqp)	smb_sl_unlock(&(rqp)->sr_slock)
@@ -75,6 +76,8 @@ struct smb_rq {
 	struct smb_vc * 	sr_vc;
 	struct smb_share*	sr_share;
 	u_short			sr_mid;
+	u_int32_t		sr_seqno;
+	u_int32_t		sr_rseqno;
 	struct mbchain		sr_rq;
 	u_int8_t		sr_rqflags;
 	u_int16_t		sr_rqflags2;
@@ -91,6 +94,7 @@ struct smb_rq {
 	int			sr_sendcnt;
 	struct timespec 	sr_timesent;
 	int			sr_lerror;
+	u_int8_t *		sr_rqsig;
 	u_int16_t *		sr_rqtid;
 	u_int16_t *		sr_rquid;
 	u_int8_t		sr_errclass;
@@ -103,7 +107,7 @@ struct smb_rq {
 	u_int16_t		sr_rpuid;
 	u_int16_t		sr_rpmid;
 	struct smb_slock	sr_slock;	/* short term locks */
-/*	struct smb_t2rq*sr_t2;*/
+	struct smb_t2rq *	sr_t2;
 	TAILQ_ENTRY(smb_rq)	sr_link;
 };
 
diff --git a/sys/netsmb/smb_smb.c b/sys/netsmb/smb_smb.c
index b38f8e8..c7d2a07 100644
--- a/sys/netsmb/smb_smb.c
+++ b/sys/netsmb/smb_smb.c
@@ -55,6 +55,8 @@ __FBSDID("$FreeBSD$");
 #include <netsmb/smb_conn.h>
 #include <netsmb/smb_tran.h>
 
+#include "opt_netsmb.h"
+
 struct smb_dialect {
 	int		d_id;
 	const char *	d_name;
@@ -80,24 +82,29 @@ smb_vc_maxread(struct smb_vc *vcp)
 	/*
 	 * Specs say up to 64k data bytes, but Windows traffic
 	 * uses 60k... no doubt for some good reason.
+	 *
+	 * Don't exceed the server's buffer size if signatures
+	 * are enabled otherwise Windows 2003 chokes. Allow space
+	 * for the SMB header & a little bit extra.
 	 */
-	if (vcp->vc_sopt.sv_caps & SMB_CAP_LARGE_READX)
+	if ((vcp->vc_sopt.sv_caps & SMB_CAP_LARGE_READX) &&
+	    (vcp->vc_hflags2 & SMB_FLAGS2_SECURITY_SIGNATURE) == 0)
 		return (60*1024);
 	else
-		return (vcp->vc_sopt.sv_maxtx);
+		return (vcp->vc_sopt.sv_maxtx - SMB_HDRLEN - 64);
 }
 
 static u_int32_t
 smb_vc_maxwrite(struct smb_vc *vcp)
 {
 	/*
-	 * Specs say up to 64k data bytes, but Windows traffic
-	 * uses 60k... probably for some good reason.
+	 * See comment above.
 	 */
-	if (vcp->vc_sopt.sv_caps & SMB_CAP_LARGE_WRITEX)
+	if ((vcp->vc_sopt.sv_caps & SMB_CAP_LARGE_WRITEX) &&
+	    (vcp->vc_hflags2 & SMB_FLAGS2_SECURITY_SIGNATURE) == 0)
 		return (60*1024);
 	else
-		return (vcp->vc_sopt.sv_maxtx);
+		return (vcp->vc_sopt.sv_maxtx - SMB_HDRLEN - 64);
 }
 
 static int
@@ -190,6 +197,10 @@ smb_smb_negotiate(struct smb_vc *vcp, struct smb_cred *scred)
 				vcp->vc_chlen = sblen;
 				vcp->obj.co_flags |= SMBV_ENCRYPT;
 			}
+#ifdef NETSMBCRYPTO
+			if (sp->sv_sm & SMB_SM_SIGS_REQUIRE)
+				vcp->vc_hflags2 |= SMB_FLAGS2_SECURITY_SIGNATURE;
+#endif
 			vcp->vc_hflags2 |= SMB_FLAGS2_KNOWS_LONG_NAMES;
 			if (dp->d_id == SMB_DIALECT_NTLM0_12 &&
 			    sp->sv_maxtx < 4096 &&
@@ -385,6 +396,8 @@ again:
 	smb_rq_bend(rqp);
 	if (ntencpass)
 		free(ntencpass, M_SMBTEMP);
+	if (vcp->vc_hflags2 & SMB_FLAGS2_SECURITY_SIGNATURE)
+		smb_calcmackey(vcp);
 	error = smb_rq_simple(rqp);
 	SMBSDEBUG("%d\n", error);
 	if (error) {
diff --git a/sys/netsmb/smb_subr.h b/sys/netsmb/smb_subr.h
index 276190f..62c084a 100644
--- a/sys/netsmb/smb_subr.h
+++ b/sys/netsmb/smb_subr.h
@@ -114,6 +114,7 @@ void smb_strfree(char *s);
 void smb_memfree(void *s);
 void *smb_zmalloc(unsigned long size, struct malloc_type *type, int flags);
 
+int  smb_calcmackey(struct smb_vc *vcp);
 int  smb_encrypt(const u_char *apwd, u_char *C8, u_char *RN);
 int  smb_ntencrypt(const u_char *apwd, u_char *C8, u_char *RN);
 int  smb_maperror(int eclass, int eno);
@@ -123,5 +124,7 @@ int  smb_put_dstring(struct mbchain *mbp, struct smb_vc *vcp,
 	const char *src, int caseopt);
 int  smb_put_string(struct smb_rq *rqp, const char *src);
 int  smb_put_asunistring(struct smb_rq *rqp, const char *src);
+int  smb_rq_sign(struct smb_rq *rqp);
+int  smb_rq_verify(struct smb_rq *rqp);
 
 #endif /* !_NETSMB_SMB_SUBR_H_ */