Commit ad46faff authored by Paulo Alcantara's avatar Paulo Alcantara Committed by Steve French
Browse files

smb: client: fix DFS mount against old servers with NTLMSSP 



Old Windows servers will return not fully qualified DFS targets by
default as specified in

  MS-DFSC 3.2.5.5 Receiving a Root Referral Request or Link Referral
  Request

    | Servers SHOULD<30> return fully qualified DNS host names of
    | targets in responses to root referral requests and link referral
    | requests.
    | ...
    | <30> Section 3.2.5.5: By default, Windows Server 2003, Windows
    | Server 2008, Windows Server 2008 R2, Windows Server 2012, and
    | Windows Server 2012 R2 return DNS host names that are not fully
    | qualified for targets.

Fix this by converting all NetBIOS host names from DFS targets to
FQDNs and try resolving them first if DNS domain name was provided in
NTLMSSP CHALLENGE_MESSAGE message from previous SMB2_SESSION_SETUP.
This also prevents the client from translating the DFS target
hostnames to another domain depending on the network domain search
order.

Signed-off-by: default avatarPaulo Alcantara (Red Hat) <pc@manguebit.com>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 0e8ae9b9

fs/smb/client/cifsglob.h

+21 −0
Original line number Diff line number Diff line
@@ -828,6 +828,7 @@ struct TCP_Server_Info { 
	 */

	char *leaf_fullpath;

	bool dfs_conn:1;

	char dns_dom[CIFS_MAX_DOMAINNAME_LEN + 1];

};



static inline bool is_smb1(struct TCP_Server_Info *server)
@@ -2312,4 +2313,24 @@ static inline bool cifs_ses_exiting(struct cifs_ses *ses) 
	return ret;

}



static inline bool cifs_netbios_name(const char *name, size_t namelen)

{

	bool ret = false;

	size_t i;



	if (namelen >= 1 && namelen <= RFC1001_NAME_LEN) {

		for (i = 0; i < namelen; i++) {

			const unsigned char c = name[i];



			if (c == '\\' || c == '/' || c == ':' || c == '*' ||

			    c == '?' || c == '"' || c == '<' || c == '>' ||

			    c == '|' || c == '.')

				return false;

			if (!ret && isalpha(c))

				ret = true;

		}

	}

	return ret;

}



#endif	/* _CIFS_GLOB_H */

fs/smb/client/connect.c

+4 −1
Original line number Diff line number Diff line
@@ -97,7 +97,8 @@ static int reconn_set_ipaddr_from_hostname(struct TCP_Server_Info *server) 
	ss = server->dstaddr;

	spin_unlock(&server->srv_lock);



	rc = dns_resolve_server_name_to_ip(unc, (struct sockaddr *)&ss, NULL);

	rc = dns_resolve_server_name_to_ip(server->dns_dom, unc,

					   (struct sockaddr *)&ss, NULL);

	kfree(unc);



	if (rc < 0) {
@@ -1710,6 +1711,8 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx, 
			goto out_err;

		}

	}

	if (ctx->dns_dom)

		strscpy(tcp_ses->dns_dom, ctx->dns_dom);



	if (ctx->nosharesock)

		tcp_ses->nosharesock = true;

fs/smb/client/dfs.c

+9 −4
Original line number Diff line number Diff line
@@ -9,6 +9,8 @@ 
#include "fs_context.h"

#include "dfs.h"



#define DFS_DOM(ctx) (ctx->dfs_root_ses ? ctx->dfs_root_ses->dns_dom : NULL)



/**

 * dfs_parse_target_referral - set fs context for dfs target referral

 *
@@ -46,8 +48,9 @@ int dfs_parse_target_referral(const char *full_path, const struct dfs_info3_para 
	if (rc)

		goto out;



	rc = dns_resolve_server_name_to_ip(path, (struct sockaddr *)&ctx->dstaddr, NULL);



	rc = dns_resolve_server_name_to_ip(DFS_DOM(ctx), path,

					   (struct sockaddr *)&ctx->dstaddr,

					   NULL);

out:

	kfree(path);

	return rc;
@@ -59,8 +62,9 @@ static int get_session(struct cifs_mount_ctx *mnt_ctx, const char *full_path) 
	int rc;



	ctx->leaf_fullpath = (char *)full_path;

	ctx->dns_dom = DFS_DOM(ctx);

	rc = cifs_mount_get_session(mnt_ctx);

	ctx->leaf_fullpath = NULL;

	ctx->leaf_fullpath = ctx->dns_dom = NULL;



	return rc;

}
@@ -264,7 +268,8 @@ static int update_fs_context_dstaddr(struct smb3_fs_context *ctx) 
	int rc = 0;



	if (!ctx->nodfs && ctx->dfs_automount) {

		rc = dns_resolve_server_name_to_ip(ctx->source, addr, NULL);

		rc = dns_resolve_server_name_to_ip(NULL, ctx->source,

						   addr, NULL);

		if (!rc)

			cifs_set_port(addr, ctx->port);

		ctx->dfs_automount = false;

fs/smb/client/dfs_cache.c

+2 −1
Original line number Diff line number Diff line
@@ -1114,7 +1114,8 @@ static bool target_share_equal(struct cifs_tcon *tcon, const char *s1) 
	extract_unc_hostname(s1, &host, &hostlen);

	scnprintf(unc, sizeof(unc), "\\\\%.*s", (int)hostlen, host);



	rc = dns_resolve_server_name_to_ip(unc, (struct sockaddr *)&ss, NULL);

	rc = dns_resolve_server_name_to_ip(server->dns_dom, unc,

					   (struct sockaddr *)&ss, NULL);

	if (rc < 0) {

		cifs_dbg(FYI, "%s: could not resolve %.*s. assuming server address matches.\n",

			 __func__, (int)hostlen, host);

fs/smb/client/dns_resolve.c

+60 −42
Original line number Diff line number Diff line
@@ -20,69 +20,87 @@ 
#include "cifsproto.h"

#include "cifs_debug.h"



static int resolve_name(const char *name, size_t namelen,

			struct sockaddr *addr, time64_t *expiry)

{

	char *ip;

	int rc;



	rc = dns_query(current->nsproxy->net_ns, NULL, name,

		       namelen, NULL, &ip, expiry, false);

	if (rc < 0) {

		cifs_dbg(FYI, "%s: unable to resolve: %*.*s\n",

			 __func__, (int)namelen, (int)namelen, name);

	} else {

		cifs_dbg(FYI, "%s: resolved: %*.*s to %s expiry %llu\n",

			 __func__, (int)namelen, (int)namelen, name, ip,

			 expiry ? (*expiry) : 0);



		rc = cifs_convert_address(addr, ip, strlen(ip));

		kfree(ip);

		if (!rc) {

			cifs_dbg(FYI, "%s: unable to determine ip address\n",

				 __func__);

			rc = -EHOSTUNREACH;

		} else {

			rc = 0;

		}

	}

	return rc;

}



/**

 * dns_resolve_server_name_to_ip - Resolve UNC server name to ip address.

 * @dom: optional DNS domain name

 * @unc: UNC path specifying the server (with '/' as delimiter)

 * @ip_addr: Where to return the IP address.

 * @expiry: Where to return the expiry time for the dns record.

 *

 * Returns zero success, -ve on error.

 */

int

dns_resolve_server_name_to_ip(const char *unc, struct sockaddr *ip_addr, time64_t *expiry)

int dns_resolve_server_name_to_ip(const char *dom, const char *unc,

				  struct sockaddr *ip_addr, time64_t *expiry)

{

	const char *hostname, *sep;

	char *ip;

	int len, rc;

	const char *name;

	size_t namelen, len;

	char *s;

	int rc;



	if (!ip_addr || !unc)

		return -EINVAL;



	len = strlen(unc);

	if (len < 3) {

		cifs_dbg(FYI, "%s: unc is too short: %s\n", __func__, unc);

	cifs_dbg(FYI, "%s: dom=%s unc=%s\n", __func__, dom, unc);

	if (strlen(unc) < 3)

		return -EINVAL;

	}



	/* Discount leading slashes for cifs */

	len -= 2;

	hostname = unc + 2;



	/* Search for server name delimiter */

	sep = memchr(hostname, '/', len);

	if (sep)

		len = sep - hostname;

	else

		cifs_dbg(FYI, "%s: probably server name is whole unc: %s\n",

			 __func__, unc);

	extract_unc_hostname(unc, &name, &namelen);

	if (!namelen)

		return -EINVAL;



	cifs_dbg(FYI, "%s: hostname=%.*s\n", __func__, (int)namelen, name);

	/* Try to interpret hostname as an IPv4 or IPv6 address */

	rc = cifs_convert_address(ip_addr, hostname, len);

	rc = cifs_convert_address(ip_addr, name, namelen);

	if (rc > 0) {

		cifs_dbg(FYI, "%s: unc is IP, skipping dns upcall: %*.*s\n", __func__, len, len,

			 hostname);

		cifs_dbg(FYI, "%s: unc is IP, skipping dns upcall: %*.*s\n",

			 __func__, (int)namelen, (int)namelen, name);

		return 0;

	}



	/* Perform the upcall */

	rc = dns_query(current->nsproxy->net_ns, NULL, hostname, len,

		       NULL, &ip, expiry, false);

	if (rc < 0) {

		cifs_dbg(FYI, "%s: unable to resolve: %*.*s\n",

			 __func__, len, len, hostname);

	} else {

		cifs_dbg(FYI, "%s: resolved: %*.*s to %s expiry %llu\n",

			 __func__, len, len, hostname, ip,

			 expiry ? (*expiry) : 0);



		rc = cifs_convert_address(ip_addr, ip, strlen(ip));

		kfree(ip);

	/*

	 * If @name contains a NetBIOS name and @dom has been specified, then

	 * convert @name to an FQDN and try resolving it first.

	 */

	if (dom && *dom && cifs_netbios_name(name, namelen)) {

		len = strnlen(dom, CIFS_MAX_DOMAINNAME_LEN) + namelen + 2;

		s = kmalloc(len, GFP_KERNEL);

		if (!s)

			return -ENOMEM;



		if (!rc) {

			cifs_dbg(FYI, "%s: unable to determine ip address\n", __func__);

			rc = -EHOSTUNREACH;

		} else

			rc = 0;

		scnprintf(s, len, "%.*s.%s", (int)namelen, name, dom);

		rc = resolve_name(s, len - 1, ip_addr, expiry);

		kfree(s);

		if (!rc)

			return 0;

	}

	return rc;

	return resolve_name(name, namelen, ip_addr, expiry);

}