From dce4683cbbe107a95f1f0d45fabc304acfb5d71a Mon Sep 17 00:00:00 2001 From: Andreas Gruenbacher Date: Mon, 15 Jul 2019 16:21:48 +0200 Subject: Don't follow symlinks unless --follow-symlinks is given * src/inp.c (plan_a, plan_b), src/util.c (copy_to_fd, copy_file, append_to_file): Unless the --follow-symlinks option is given, open files with the O_NOFOLLOW flag to avoid following symlinks. So far, we were only doing that consistently for input files. * src/util.c (create_backup): When creating empty backup files, (re)create them with O_CREAT | O_EXCL to avoid following symlinks in that case as well. CVE: CVE-2019-13636 Upstream-Status: Backport[https://git.savannah.gnu.org/cgit/patch.git/patch/?id=dce4683cbbe107a95f1f0d45fabc304acfb5d71a] Signed-off-by: Anuj Mittal --- src/inp.c | 12 ++++++++++-- src/util.c | 14 +++++++++++--- 2 files changed, 21 insertions(+), 5 deletions(-) diff --git a/src/inp.c b/src/inp.c index 32d0919..22d7473 100644 --- a/src/inp.c +++ b/src/inp.c @@ -238,8 +238,13 @@ plan_a (char const *filename) { if (S_ISREG (instat.st_mode)) { - int ifd = safe_open (filename, O_RDONLY|binary_transput, 0); + int flags = O_RDONLY | binary_transput; size_t buffered = 0, n; + int ifd; + + if (! follow_symlinks) + flags |= O_NOFOLLOW; + ifd = safe_open (filename, flags, 0); if (ifd < 0) pfatal ("can't open file %s", quotearg (filename)); @@ -340,6 +345,7 @@ plan_a (char const *filename) static void plan_b (char const *filename) { + int flags = O_RDONLY | binary_transput; int ifd; FILE *ifp; int c; @@ -353,7 +359,9 @@ plan_b (char const *filename) if (instat.st_size == 0) filename = NULL_DEVICE; - if ((ifd = safe_open (filename, O_RDONLY | binary_transput, 0)) < 0 + if (! follow_symlinks) + flags |= O_NOFOLLOW; + if ((ifd = safe_open (filename, flags, 0)) < 0 || ! (ifp = fdopen (ifd, binary_transput ? "rb" : "r"))) pfatal ("Can't open file %s", quotearg (filename)); if (TMPINNAME_needs_removal) diff --git a/src/util.c b/src/util.c index 1cc08ba..fb38307 100644 --- a/src/util.c +++ b/src/util.c @@ -388,7 +388,7 @@ create_backup (char const *to, const struct stat *to_st, bool leave_original) try_makedirs_errno = ENOENT; safe_unlink (bakname); - while ((fd = safe_open (bakname, O_CREAT | O_WRONLY | O_TRUNC, 0666)) < 0) + while ((fd = safe_open (bakname, O_CREAT | O_EXCL | O_WRONLY | O_TRUNC, 0666)) < 0) { if (errno != try_makedirs_errno) pfatal ("Can't create file %s", quotearg (bakname)); @@ -579,10 +579,13 @@ create_file (char const *file, int open_flags, mode_t mode, static void copy_to_fd (const char *from, int tofd) { + int from_flags = O_RDONLY | O_BINARY; int fromfd; ssize_t i; - if ((fromfd = safe_open (from, O_RDONLY | O_BINARY, 0)) < 0) + if (! follow_symlinks) + from_flags |= O_NOFOLLOW; + if ((fromfd = safe_open (from, from_flags, 0)) < 0) pfatal ("Can't reopen file %s", quotearg (from)); while ((i = read (fromfd, buf, bufsize)) != 0) { @@ -625,6 +628,8 @@ copy_file (char const *from, char const *to, struct stat *tost, else { assert (S_ISREG (mode)); + if (! follow_symlinks) + to_flags |= O_NOFOLLOW; tofd = create_file (to, O_WRONLY | O_BINARY | to_flags, mode, to_dir_known_to_exist); copy_to_fd (from, tofd); @@ -640,9 +645,12 @@ copy_file (char const *from, char const *to, struct stat *tost, void append_to_file (char const *from, char const *to) { + int to_flags = O_WRONLY | O_APPEND | O_BINARY; int tofd; - if ((tofd = safe_open (to, O_WRONLY | O_BINARY | O_APPEND, 0)) < 0) + if (! follow_symlinks) + to_flags |= O_NOFOLLOW; + if ((tofd = safe_open (to, to_flags, 0)) < 0) pfatal ("Can't reopen file %s", quotearg (to)); copy_to_fd (from, tofd); if (close (tofd) != 0) -- cgit v1.0-41-gc330