s4-pvfs: new pvfs_sys module

The pvfs_sys_*() calls provide wrapper functions for posix file
functions which use root privileges to override EACCES failures if
PVFS_FLAG_PERM_OVERRIDE is set

Pair-Programmed-With: Andrew Bartlett <abartlet@samba.org>

source4/ntvfs/posix/config.mk

@@ -72,6 +72,7 @@ ntvfs_posix_OBJ_FILES = $(addprefix $(ntvfssrcdir)/posix/, \
 		pvfs_xattr.o \
 		pvfs_streams.o \
 		pvfs_notify.o \
+		pvfs_sys.o \
 		xattr_system.o \
 		xattr_tdb.o)
 

source4/ntvfs/posix/pvfs_sys.c

@@ -0,0 +1,300 @@
+/*
+   Unix SMB/CIFS implementation.
+
+   POSIX NTVFS backend - pvfs_sys wrappers
+
+   Copyright (C) Andrew Tridgell 2010
+   Copyright (C) Andrew Bartlett 2010
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "includes.h"
+#include "vfs_posix.h"
+#include "../lib/util/unix_privs.h"
+
+/*
+  these wrapper functions must only be called when the appropriate ACL
+  has already been checked. The wrappers will override a EACCES result
+  by gaining root privileges if the 'pvfs:perm override' is set on the
+  share (it is enabled by default)
+ */
+
+
+/*
+  chown a file that we created with a root privileges override
+ */
+static int pvfs_sys_fchown(struct pvfs_state *pvfs, void *privs, int fd)
+{
+	return fchown(fd, root_privileges_original_uid(privs), -1);
+}
+
+/*
+  chown a directory that we created with a root privileges override
+ */
+static int pvfs_sys_chown(struct pvfs_state *pvfs, void *privs, const char *name)
+{
+	return chown(name, root_privileges_original_uid(privs), -1);
+}
+
+
+/*
+  wrap open for system override
+*/
+int pvfs_sys_open(struct pvfs_state *pvfs, const char *filename, int flags, mode_t mode)
+{
+	int fd, ret;
+	void *privs;
+	int saved_errno, orig_errno;
+	int retries = 5;
+
+	orig_errno = errno;
+
+	fd = open(filename, flags, mode);
+	if (fd != -1 ||
+	    !(pvfs->flags & PVFS_FLAG_PERM_OVERRIDE) ||
+	    errno != EACCES) {
+		return fd;
+	}
+
+	saved_errno = errno;
+	privs = root_privileges();
+
+	/* don't allow permission overrides to follow links */
+#ifdef O_NOFOLLOW
+	flags |= O_NOFOLLOW;
+#endif
+
+	/*
+	   if O_CREAT was specified and O_EXCL was not specified
+	   then initially do the open without O_CREAT, as in that case
+	   we know that we did not create the file, so we don't have
+	   to fchown it
+	 */
+	if ((flags & O_CREAT) && !(flags & O_EXCL)) {
+	try_again:
+		fd = open(filename, flags & ~O_CREAT, mode);
+		/* if this open succeeded, or if it failed
+		   with anything other than ENOENT, then we return the
+		   open result, with the original errno */
+		if (fd == -1 && errno != ENOENT) {
+			talloc_free(privs);
+			errno = saved_errno;
+			return -1;
+		}
+		if (fd != -1) {
+			/* the file already existed and we opened it */
+			talloc_free(privs);
+			errno = orig_errno;
+			return fd;
+		}
+
+		fd = open(filename, flags | O_EXCL, mode);
+		if (fd == -1 && errno != EEXIST) {
+			talloc_free(privs);
+			errno = saved_errno;
+			return -1;
+		}
+		if (fd != -1) {
+			/* we created the file, we need to set the
+			   right ownership on it */
+			ret = pvfs_sys_fchown(pvfs, privs, fd);
+			if (ret == -1) {
+				close(fd);
+				unlink(filename);
+				talloc_free(privs);
+				errno = saved_errno;
+				return -1;
+			}
+			talloc_free(privs);
+			errno = orig_errno;
+			return fd;
+		}
+
+		/* the file got created between the two times
+		   we tried to open it! Try again */
+		if (retries-- > 0) {
+			goto try_again;
+		}
+
+		talloc_free(privs);
+		errno = saved_errno;
+		return -1;
+	}
+
+	fd = open(filename, flags, mode);
+	if (fd == -1) {
+		talloc_free(privs);
+		errno = saved_errno;
+		return -1;
+	}
+
+	/* if we have created a file then fchown it */
+	if (flags & O_CREAT) {
+		ret = pvfs_sys_fchown(pvfs, privs, fd);
+		if (ret == -1) {
+			close(fd);
+			unlink(filename);
+			talloc_free(privs);
+			errno = saved_errno;
+			return -1;
+		}
+	}
+
+	talloc_free(privs);
+	return fd;
+}
+
+
+/*
+  wrap unlink for system override
+*/
+int pvfs_sys_unlink(struct pvfs_state *pvfs, const char *filename)
+{
+	int ret;
+	void *privs;
+	int saved_errno, orig_errno;
+
+	orig_errno = errno;
+
+	ret = unlink(filename);
+	if (ret != -1 ||
+	    !(pvfs->flags & PVFS_FLAG_PERM_OVERRIDE) ||
+	    errno != EACCES) {
+		return ret;
+	}
+
+	saved_errno = errno;
+
+	privs = root_privileges();
+	ret = unlink(filename);
+	if (ret == -1) {
+		errno = saved_errno;
+		talloc_free(privs);
+		return -1;
+	}
+
+	errno = orig_errno;
+	talloc_free(privs);
+	return ret;
+}
+
+
+/*
+  wrap rename for system override
+*/
+int pvfs_sys_rename(struct pvfs_state *pvfs, const char *name1, const char *name2)
+{
+	int ret;
+	void *privs;
+	int saved_errno, orig_errno;
+
+	orig_errno = errno;
+
+	ret = rename(name1, name2);
+	if (ret != -1 ||
+	    !(pvfs->flags & PVFS_FLAG_PERM_OVERRIDE) ||
+	    errno != EACCES) {
+		return ret;
+	}
+
+	saved_errno = errno;
+
+	privs = root_privileges();
+	ret = rename(name1, name2);
+	if (ret == -1) {
+		errno = saved_errno;
+		talloc_free(privs);
+		return -1;
+	}
+
+	errno = orig_errno;
+	talloc_free(privs);
+	return ret;
+}
+
+
+/*
+  wrap mkdir for system override
+*/
+int pvfs_sys_mkdir(struct pvfs_state *pvfs, const char *dirname, mode_t mode)
+{
+	int ret;
+	void *privs;
+	int saved_errno, orig_errno;
+
+	orig_errno = errno;
+
+	ret = mkdir(dirname, mode);
+	if (ret != -1 ||
+	    !(pvfs->flags & PVFS_FLAG_PERM_OVERRIDE) ||
+	    errno != EACCES) {
+		return ret;
+	}
+
+	saved_errno = errno;
+	privs = root_privileges();
+
+	ret = mkdir(dirname, mode);
+	if (ret == -1) {
+		talloc_free(privs);
+		errno = saved_errno;
+		return -1;
+	}
+
+	ret = pvfs_sys_chown(pvfs, privs, dirname);
+	if (ret == -1) {
+		rmdir(dirname);
+		talloc_free(privs);
+		errno = saved_errno;
+		return -1;
+	}
+
+	talloc_free(privs);
+	return ret;
+}
+
+
+/*
+  wrap rmdir for system override
+*/
+int pvfs_sys_rmdir(struct pvfs_state *pvfs, const char *dirname)
+{
+	int ret;
+	void *privs;
+	int saved_errno, orig_errno;
+
+	orig_errno = errno;
+
+	ret = rmdir(dirname);
+	if (ret != -1 ||
+	    !(pvfs->flags & PVFS_FLAG_PERM_OVERRIDE) ||
+	    errno != EACCES) {
+		return ret;
+	}
+
+	saved_errno = errno;
+
+	privs = root_privileges();
+	ret = rmdir(dirname);
+	if (ret == -1) {
+		errno = saved_errno;
+		talloc_free(privs);
+		return -1;
+	}
+
+	errno = orig_errno;
+	talloc_free(privs);
+	return ret;
+}