From: Steve French <stfrench@microsoft.com>
Date: Tue, 3 Sep 2019 21:18:49 -0500
Subject: [PATCH] smb3: allow skipping signature verification for perf
 sensitive configurations
Git-commit: 4f5c10f1ad45ae453822113dd0fe39ed757037fb
References: bsc#1144333
Patch-mainline: v5.4-rc1

Add new mount option "signloosely" which enables signing but skips the
sometimes expensive signing checks in the responses (signatures are
calculated and sent correctly in the SMB2/SMB3 requests even with this
mount option but skipped in the responses).  Although weaker for security
(and also data integrity in case a packet were corrupted), this can provide
enough of a performance benefit (calculating the signature to verify a
packet can be expensive especially for large packets) to be useful in
some cases.

Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Acked-by: Paulo Alcantara <palcantara@suse.de>
---
 fs/cifs/cifsglob.h      |  2 ++
 fs/cifs/connect.c       | 13 ++++++++++---
 fs/cifs/smb2transport.c |  1 +
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index fa5abe3a8514..1f53dee211d8 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -542,6 +542,7 @@ struct smb_vol {
 	umode_t dir_mode;
 	enum securityEnum sectype; /* sectype requested via mnt opts */
 	bool sign; /* was signing requested via mnt opts? */
+	bool ignore_signature:1;
 	bool retry:1;
 	bool intr:1;
 	bool setuids:1;
@@ -681,6 +682,7 @@ struct TCP_Server_Info {
 	char server_GUID[16];
 	__u16 sec_mode;
 	bool sign; /* is signing enabled on this connection? */
+	bool ignore_signature:1; /* skip validation of signatures in SMB2/3 rsp */
 	bool session_estab; /* mark when very first sess is established */
 	int echo_credits;  /* echo reserved slots */
 	int oplock_credits;  /* oplock break reserved slots */
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 85f8d943a05a..17882cede197 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -91,7 +91,7 @@ enum {
 	Opt_serverino, Opt_noserverino,
 	Opt_rwpidforward, Opt_cifsacl, Opt_nocifsacl,
 	Opt_acl, Opt_noacl, Opt_locallease,
-	Opt_sign, Opt_seal, Opt_noac,
+	Opt_sign, Opt_ignore_signature, Opt_seal, Opt_noac,
 	Opt_fsc, Opt_mfsymlinks,
 	Opt_multiuser, Opt_sloppy, Opt_nosharesock,
 	Opt_persistent, Opt_nopersistent,
@@ -183,6 +183,7 @@ static const match_table_t cifs_mount_option_tokens = {
 	{ Opt_noacl, "noacl" },
 	{ Opt_locallease, "locallease" },
 	{ Opt_sign, "sign" },
+	{ Opt_ignore_signature, "signloosely" },
 	{ Opt_seal, "seal" },
 	{ Opt_noac, "noac" },
 	{ Opt_fsc, "fsc" },
@@ -1877,6 +1878,10 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 		case Opt_sign:
 			vol->sign = true;
 			break;
+		case Opt_ignore_signature:
+			vol->sign = true;
+			vol->ignore_signature = true;
+			break;
 		case Opt_seal:
 			/* we do not do the following in secFlags because seal
 			 * is a per tree connection (mount) not a per socket
@@ -2608,6 +2613,9 @@ static int match_server(struct TCP_Server_Info *server, struct smb_vol *vol)
 	if (server->rdma != vol->rdma)
 		return 0;
 
+	if (server->ignore_signature != vol->ignore_signature)
+		return 0;
+
 	return 1;
 }
 
@@ -2785,7 +2793,7 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
 	tcp_ses->tcpStatus = CifsNeedNegotiate;
 
 	tcp_ses->nr_targets = 1;
-
+	tcp_ses->ignore_signature = volume_info->ignore_signature;
 	/* thread spawned, put it on the list */
 	spin_lock(&cifs_tcp_ses_lock);
 	list_add(&tcp_ses->tcp_ses_list, &cifs_tcp_ses_list);
@@ -3235,7 +3243,6 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb_vol *volume_info)
 
 	ses->sectype = volume_info->sectype;
 	ses->sign = volume_info->sign;
-
 	mutex_lock(&ses->session_mutex);
 	rc = cifs_negotiate_protocol(xid, ses);
 	if (!rc)
diff --git a/fs/cifs/smb2transport.c b/fs/cifs/smb2transport.c
index b02242eacb55..148d7942c796 100644
--- a/fs/cifs/smb2transport.c
+++ b/fs/cifs/smb2transport.c
@@ -522,6 +522,7 @@ smb2_verify_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
 	if ((shdr->Command == SMB2_NEGOTIATE) ||
 	    (shdr->Command == SMB2_SESSION_SETUP) ||
 	    (shdr->Command == SMB2_OPLOCK_BREAK) ||
+	    server->ignore_signature ||
 	    (!server->session_estab))
 		return 0;
 
-- 
2.25.1