commit 7f61a6cb796c3ecdaf7f8a49bdebe69ede3f34a1
parent dbbf9a052f3740edccf3cb3ce4f46d687da158f1
Author: Chris Allegretta <chrisa@asty.org>
Date: Fri, 9 Apr 2010 15:01:51 +0000
2010-04-09 Chris Allegretta <chrisa@asty.org>
* files.c (do_writeout): Better security fixes for backup file writing,
mangled from submission by Dan Rosenberg <dan.j.rosenberg at gmail>.
git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@4496 35c25a1d-7b9e-4130-9fde-d3aeb78583b8
Diffstat:
2 files changed, 28 insertions(+), 18 deletions(-)
diff --git a/ChangeLog b/ChangeLog
@@ -1,4 +1,8 @@
-2010-04-02 Chris Allegretta <chrisa@asty.org>
+2010-04-09 Chris Allegretta <chrisa@asty.org>
+ * files.c (do_writeout): Better security fixes for backup file writing,
+ mangled from submission by Dan Rosenberg <dan.j.rosenberg at gmail>.
+
+2010-04-08 Chris Allegretta <chrisa@asty.org>
* files.c (do_writeout): Previous fixes should not cause a crash
when saving a new file. Discovered by Mike Frysinger <vapier@gentoo.org>.
diff --git a/src/files.c b/src/files.c
@@ -1515,11 +1515,11 @@ bool write_file(const char *name, FILE *f_open, bool tmp, append_type
if (ISSET(BACKUP_FILE) && !tmp && realexists && ((append !=
OVERWRITE || openfile->mark_set) ||
openfile->current_stat->st_mtime == st.st_mtime)) {
+ int backup_fd;
FILE *backup_file;
char *backupname;
struct utimbuf filetime;
int copy_status;
- struct stat backupst;
/* Save the original file's access and modification times. */
filetime.actime = openfile->current_stat->st_atime;
@@ -1589,27 +1589,36 @@ bool write_file(const char *name, FILE *f_open, bool tmp, append_type
sprintf(backupname, "%s~", realname);
}
- if (stat(backupname, &backupst) != -1 &&
- (backupst.st_uid != st.st_uid)) {
- statusbar(_("Error writing backup file %s: File owner mismatch"), backupname,
- strerror(errno));
+ /* First, unlink any existing backups. Next, open the backup
+ file with O_CREAT and O_EXCL. If it succeeds, we
+ have a file descriptor to a new backup file. */
+ if (unlink(backupname) < 0 && errno != ENOENT) {
+ statusbar(_("Error writing backup file %s: %s"), backupname,
+ strerror(errno));
free(backupname);
goto cleanup_and_exit;
}
+ backup_fd = open(backupname, O_WRONLY | O_CREAT | O_APPEND,
+ S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
+ /* Now we've got a safe file stream. If the previous open()
+ call failed, this will return NULL. */
+ backup_file = fdopen(backup_fd, "wb");
- /* Open the destination backup file. Before we write to it, we
- * set its permissions, so no unauthorized person can read it as
- * we write. */
- backup_file = fopen(backupname, "wb");
+ if (backup_fd < 0 || backup_file == NULL) {
+ statusbar(_("Error writing backup file %s: %s"), backupname,
+ strerror(errno));
+ free(backupname);
+ goto cleanup_and_exit;
+ }
- if (backup_file == NULL || chmod(backupname,
- openfile->current_stat->st_mode) == -1) {
+ if (fchmod(backup_fd, openfile->current_stat->st_mode) == -1 ||
+ fchown(backup_fd, openfile->current_stat->st_uid,
+ openfile->current_stat->st_gid) == -1 ) {
statusbar(_("Error writing backup file %s: %s"), backupname,
strerror(errno));
free(backupname);
- if (backup_file != NULL)
- fclose(backup_file);
+ fclose(backup_file);
/* If we can't write to the backup, DONT go on, since
whatever caused the backup file to fail (e.g. disk
full may well cause the real file write to fail, which
@@ -1625,10 +1634,7 @@ bool write_file(const char *name, FILE *f_open, bool tmp, append_type
copy_status = copy_file(f, backup_file);
/* And set its metadata. */
- if (copy_status != 0 || chown(backupname,
- openfile->current_stat->st_uid,
- openfile->current_stat->st_gid) == -1 ||
- utime(backupname, &filetime) == -1) {
+ if (copy_status != 0 || utime(backupname, &filetime) == -1) {
if (copy_status == -1) {
statusbar(_("Error reading %s: %s"), realname,
strerror(errno));
