cifs: fix ntlmssp on old servers

Some older servers seem to require the workstation name during ntlmssp
to be at most 15 chars (RFC1001 name length), so truncate it before
sending when using insecure dialects.

Link: https://lore.kernel.org/r/e6837098-15d9-acb6-7e34-1923cf8c6fe1@winds.org
Reported-by: Byron Stanoszek <gandalf@winds.org>
Tested-by: Byron Stanoszek <gandalf@winds.org>
Fixes: 49bd49f ("cifs: send workstation name during ntlmssp session setup")
Cc: stable@vger.kernel.org
Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: Paulo Alcantara

fs/cifs/cifsglob.h

@@ -952,7 +952,7 @@ struct cifs_ses {
 				   and after mount option parsing we fill it */
 	char *domainName;
 	char *password;
-	char *workstation_name;
+	char workstation_name[CIFS_MAX_WORKSTATION_LEN];
 	struct session_key auth_key;
 	struct ntlmssp_auth *ntlmssp; /* ciphertext, flags, server challenge */
 	enum securityEnum sectype; /* what security flavor was specified? */
@@ -2018,4 +2018,17 @@ static inline u64 cifs_flock_len(struct file_lock *fl)
 	return fl->fl_end == OFFSET_MAX ? 0 : fl->fl_end - fl->fl_start + 1;
 }
 
+static inline size_t ntlmssp_workstation_name_size(const struct cifs_ses *ses)
+{
+	if (WARN_ON_ONCE(!ses || !ses->server))
+		return 0;
+	/*
+	 * Make workstation name no more than 15 chars when using insecure dialects as some legacy
+	 * servers do require it during NTLMSSP.
+	 */
+	if (ses->server->dialect <= SMB20_PROT_ID)
+		return min_t(size_t, sizeof(ses->workstation_name), RFC1001_NAME_LEN_WITH_NULL);
+	return sizeof(ses->workstation_name);
+}
+
 #endif	/* _CIFS_GLOB_H */

fs/cifs/connect.c

@@ -2037,18 +2037,7 @@ cifs_set_cifscreds(struct smb3_fs_context *ctx, struct cifs_ses *ses)
 		}
 	}
 
-	ctx->workstation_name = kstrdup(ses->workstation_name, GFP_KERNEL);
-	if (!ctx->workstation_name) {
-		cifs_dbg(FYI, "Unable to allocate memory for workstation_name\n");
-		rc = -ENOMEM;
-		kfree(ctx->username);
-		ctx->username = NULL;
-		kfree_sensitive(ctx->password);
-		ctx->password = NULL;
-		kfree(ctx->domainname);
-		ctx->domainname = NULL;
-		goto out_key_put;
-	}
+	strscpy(ctx->workstation_name, ses->workstation_name, sizeof(ctx->workstation_name));
 
 out_key_put:
 	up_read(&key->sem);
@@ -2157,12 +2146,9 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
 		if (!ses->domainName)
 			goto get_ses_fail;
 	}
-	if (ctx->workstation_name) {
-		ses->workstation_name = kstrdup(ctx->workstation_name,
-						GFP_KERNEL);
-		if (!ses->workstation_name)
-			goto get_ses_fail;
-	}
+
+	strscpy(ses->workstation_name, ctx->workstation_name, sizeof(ses->workstation_name));
+
 	if (ctx->domainauto)
 		ses->domainAuto = ctx->domainauto;
 	ses->cred_uid = ctx->cred_uid;

fs/cifs/fs_context.c

@@ -313,7 +313,6 @@ smb3_fs_context_dup(struct smb3_fs_context *new_ctx, struct smb3_fs_context *ctx
 	new_ctx->password = NULL;
 	new_ctx->server_hostname = NULL;
 	new_ctx->domainname = NULL;
-	new_ctx->workstation_name = NULL;
 	new_ctx->UNC = NULL;
 	new_ctx->source = NULL;
 	new_ctx->iocharset = NULL;
@@ -328,7 +327,6 @@ smb3_fs_context_dup(struct smb3_fs_context *new_ctx, struct smb3_fs_context *ctx
 	DUP_CTX_STR(UNC);
 	DUP_CTX_STR(source);
 	DUP_CTX_STR(domainname);
-	DUP_CTX_STR(workstation_name);
 	DUP_CTX_STR(nodename);
 	DUP_CTX_STR(iocharset);
 
@@ -767,8 +765,7 @@ static int smb3_verify_reconfigure_ctx(struct fs_context *fc,
 		cifs_errorf(fc, "can not change domainname during remount\n");
 		return -EINVAL;
 	}
-	if (new_ctx->workstation_name &&
-	    (!old_ctx->workstation_name || strcmp(new_ctx->workstation_name, old_ctx->workstation_name))) {
+	if (strcmp(new_ctx->workstation_name, old_ctx->workstation_name)) {
 		cifs_errorf(fc, "can not change workstation_name during remount\n");
 		return -EINVAL;
 	}
@@ -815,7 +812,6 @@ static int smb3_reconfigure(struct fs_context *fc)
 	STEAL_STRING(cifs_sb, ctx, username);
 	STEAL_STRING(cifs_sb, ctx, password);
 	STEAL_STRING(cifs_sb, ctx, domainname);
-	STEAL_STRING(cifs_sb, ctx, workstation_name);
 	STEAL_STRING(cifs_sb, ctx, nodename);
 	STEAL_STRING(cifs_sb, ctx, iocharset);
 
@@ -1471,22 +1467,15 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
 
 int smb3_init_fs_context(struct fs_context *fc)
 {
-	int rc;
 	struct smb3_fs_context *ctx;
 	char *nodename = utsname()->nodename;
 	int i;
 
 	ctx = kzalloc(sizeof(struct smb3_fs_context), GFP_KERNEL);
-	if (unlikely(!ctx)) {
-		rc = -ENOMEM;
-		goto err_exit;
-	}
+	if (unlikely(!ctx))
+		return -ENOMEM;
 
-	ctx->workstation_name = kstrdup(nodename, GFP_KERNEL);
-	if (unlikely(!ctx->workstation_name)) {
-		rc = -ENOMEM;
-		goto err_exit;
-	}
+	strscpy(ctx->workstation_name, nodename, sizeof(ctx->workstation_name));
 
 	/*
 	 * does not have to be perfect mapping since field is
@@ -1559,14 +1548,6 @@ int smb3_init_fs_context(struct fs_context *fc)
 	fc->fs_private = ctx;
 	fc->ops = &smb3_fs_context_ops;
 	return 0;
-
-err_exit:
-	if (ctx) {
-		kfree(ctx->workstation_name);
-		kfree(ctx);
-	}
-
-	return rc;
 }
 
 void
@@ -1592,8 +1573,6 @@ smb3_cleanup_fs_context_contents(struct smb3_fs_context *ctx)
 	ctx->source = NULL;
 	kfree(ctx->domainname);
 	ctx->domainname = NULL;
-	kfree(ctx->workstation_name);
-	ctx->workstation_name = NULL;
 	kfree(ctx->nodename);
 	ctx->nodename = NULL;
 	kfree(ctx->iocharset);

fs/cifs/fs_context.h

@@ -171,7 +171,7 @@ struct smb3_fs_context {
 	char *server_hostname;
 	char *UNC;
 	char *nodename;
-	char *workstation_name;
+	char workstation_name[CIFS_MAX_WORKSTATION_LEN];
 	char *iocharset;  /* local code page for mapping to and from Unicode */
 	char source_rfc1001_name[RFC1001_NAME_LEN_WITH_NULL]; /* clnt nb name */
 	char target_rfc1001_name[RFC1001_NAME_LEN_WITH_NULL]; /* srvr nb name */

fs/cifs/misc.c

@@ -95,7 +95,6 @@ sesInfoFree(struct cifs_ses *buf_to_free)
 	kfree_sensitive(buf_to_free->password);
 	kfree(buf_to_free->user_name);
 	kfree(buf_to_free->domainName);
-	kfree(buf_to_free->workstation_name);
 	kfree_sensitive(buf_to_free->auth_key.response);
 	kfree(buf_to_free->iface_list);
 	kfree_sensitive(buf_to_free);

fs/cifs/sess.c

@@ -741,9 +741,9 @@ static int size_of_ntlmssp_blob(struct cifs_ses *ses, int base_size)
 	else
 		sz += sizeof(__le16);
 
-	if (ses->workstation_name)
+	if (ses->workstation_name[0])
 		sz += sizeof(__le16) * strnlen(ses->workstation_name,
-			CIFS_MAX_WORKSTATION_LEN);
+					       ntlmssp_workstation_name_size(ses));
 	else
 		sz += sizeof(__le16);
 
@@ -987,7 +987,7 @@ int build_ntlmssp_auth_blob(unsigned char **pbuffer,
 
 	cifs_security_buffer_from_str(&sec_blob->WorkstationName,
 				      ses->workstation_name,
-				      CIFS_MAX_WORKSTATION_LEN,
+				      ntlmssp_workstation_name_size(ses),
 				      *pbuffer, &tmp,
 				      nls_cp);