From eb27f9b7bf9c1dc902d9545eecf805831bd4e46c Mon Sep 17 00:00:00 2001
From: Jeremy Allison <jra@samba.org>
Date: Tue, 5 Jan 2016 11:18:12 -0800
Subject: [PATCH 1/8] CVE-2015-7560: s3: smbd: Add refuse_symlink() function
 that can be used to prevent operations on a symlink.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11648

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Michael Adam <obnox@samba.org>
---
 source3/smbd/trans2.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

--- source3/smbd/trans2.c
+++ source3/smbd/trans2.c
@@ -51,6 +51,34 @@ static char *store_file_unix_basic_info2
 				files_struct *fsp,
 				const SMB_STRUCT_STAT *psbuf);
 
+/****************************************************************************
+ Check if an open file handle or pathname is a symlink.
+****************************************************************************/
+
+static NTSTATUS refuse_symlink(connection_struct *conn,
+			const files_struct *fsp,
+			const char *name)
+{
+	SMB_STRUCT_STAT sbuf;
+	const SMB_STRUCT_STAT *pst = NULL;
+
+	if (fsp) {
+		pst = &fsp->fsp_name->st;
+	} else {
+		int ret = vfs_stat_smb_fname(conn,
+				name,
+				&sbuf);
+		if (ret == -1) {
+			return map_nt_error_from_unix(errno);
+		}
+		pst = &sbuf;
+	}
+	if (S_ISLNK(pst->st_ex_mode)) {
+		return NT_STATUS_ACCESS_DENIED;
+	}
+	return NT_STATUS_OK;
+}
+
 /********************************************************************
  Roundup a value to the nearest allocation roundup size boundary.
  Only do this for Windows clients.
@@ -181,12 +209,22 @@ NTSTATUS get_ea_names_from_file(TALLOC_C
 	char **names, **tmp;
 	size_t num_names;
 	ssize_t sizeret = -1;
+	NTSTATUS status;
+
+	if (pnames) {
+		*pnames = NULL;
+	}
+	*pnum_names = 0;
 
 	if (!lp_ea_support(SNUM(conn))) {
-		if (pnames) {
-			*pnames = NULL;
-		}
-		*pnum_names = 0;
+		return NT_STATUS_OK;
+	}
+
+	status = refuse_symlink(conn, fsp, fname);
+	if (!NT_STATUS_IS_OK(status)) {
+		/*
+		 * Just return no EA's on a symlink.
+		 */
 		return NT_STATUS_OK;
 	}
 
@@ -236,10 +274,6 @@ NTSTATUS get_ea_names_from_file(TALLOC_C
 
 	if (sizeret == 0) {
 		TALLOC_FREE(names);
-		if (pnames) {
-			*pnames = NULL;
-		}
-		*pnum_names = 0;
 		return NT_STATUS_OK;
 	}
 
@@ -550,6 +584,7 @@ NTSTATUS set_ea(connection_struct *conn,
 		const struct smb_filename *smb_fname, struct ea_list *ea_list)
 {
 	char *fname = NULL;
+	NTSTATUS status;
 
 	if (!lp_ea_support(SNUM(conn))) {
 		return NT_STATUS_EAS_NOT_SUPPORTED;
@@ -559,6 +594,12 @@ NTSTATUS set_ea(connection_struct *conn,
 		return NT_STATUS_ACCESS_DENIED;
 	}
 
+	status = refuse_symlink(conn, fsp, smb_fname->base_name);
+	if (!NT_STATUS_IS_OK(status)) {
+		return status;
+	}
+
+
 	/* For now setting EAs on streams isn't supported. */
 	fname = smb_fname->base_name;
 
@@ -4931,6 +4972,13 @@ NTSTATUS smbd_do_qfilepathinfo(connectio
 				uint16 num_file_acls = 0;
 				uint16 num_def_acls = 0;
 
+				status = refuse_symlink(conn,
+						fsp,
+						smb_fname->base_name);
+				if (!NT_STATUS_IS_OK(status)) {
+					return status;
+				}
+
 				if (fsp && fsp->fh->fd != -1) {
 					file_acl = SMB_VFS_SYS_ACL_GET_FD(fsp);
 				} else {
@@ -6452,6 +6500,7 @@ static NTSTATUS smb_set_posix_acl(connec
 	uint16 num_def_acls;
 	bool valid_file_acls = True;
 	bool valid_def_acls = True;
+	NTSTATUS status;
 
 	if (total_data < SMB_POSIX_ACL_HEADER_SIZE) {
 		return NT_STATUS_INVALID_PARAMETER;
@@ -6479,6 +6528,11 @@ static NTSTATUS smb_set_posix_acl(connec
 		return NT_STATUS_INVALID_PARAMETER;
 	}
 
+	status = refuse_symlink(conn, fsp, smb_fname->base_name);
+	if (!NT_STATUS_IS_OK(status)) {
+		return status;
+	}
+
 	DEBUG(10,("smb_set_posix_acl: file %s num_file_acls = %u, num_def_acls = %u\n",
 		smb_fname ? smb_fname_str_dbg(smb_fname) : fsp_str_dbg(fsp),
 		(unsigned int)num_file_acls,
--- source3/smbd/nttrans.c
+++ source3/smbd/nttrans.c
@@ -877,6 +877,12 @@ NTSTATUS set_sd(files_struct *fsp, struc
 		return NT_STATUS_OK;
 	}
 
+	if (S_ISLNK(fsp->fsp_name->st.st_ex_mode)) {
+		DEBUG(10, ("ACL set on symlink %s denied.\n",
+			fsp_str_dbg(fsp)));
+		return NT_STATUS_ACCESS_DENIED;
+	}
+
 	if (psd->owner_sid == NULL) {
 		security_info_sent &= ~SECINFO_OWNER;
 	}
@@ -1925,6 +1931,12 @@ NTSTATUS smbd_do_query_security_desc(con
 		return NT_STATUS_ACCESS_DENIED;
 	}
 
+	if (S_ISLNK(fsp->fsp_name->st.st_ex_mode)) {
+		DEBUG(10, ("ACL get on symlink %s denied.\n",
+			fsp_str_dbg(fsp)));
+		return NT_STATUS_ACCESS_DENIED;
+	}
+
 	if (security_info_wanted & (SECINFO_DACL|SECINFO_OWNER|
 			SECINFO_GROUP|SECINFO_SACL)) {
 		/* Don't return SECINFO_LABEL if anything else was