Based on the patch from https://www.sudo.ws/repos/sudo/raw-rev/c2e36a80a279
Backported to 1.8.15 by Mark H Weaver <mhw@netris.org>
# HG changeset patch
# User Todd C. Miller <Todd.Miller@courtesan.com>
# Date 1452475889 25200
# Node ID c2e36a80a27927c32cba55afae78b8dc830cddc3
# Parent 94ffd6b18431fa4b9ed0a0c3f0b7b9582a4f6bde
Rewritten sudoedit_checkdir support that checks all the dirs in the
path and refuses to follow symlinks in writable directories.
This is a better fix for CVE-2015-5602.
Adapted from a diff by Ben Hutchings. Bug #707
diff -r 94ffd6b18431 -r c2e36a80a279 doc/CONTRIBUTORS
--- a/doc/CONTRIBUTORS Mon Jan 04 10:47:11 2016 -0700
+++ b/doc/CONTRIBUTORS Sun Jan 10 18:31:29 2016 -0700
@@ -58,6 +58,7 @@
Holloway, Nick
Hoover, Adam
Hunter, Michael T.
+ Hutchings, Ben
Irrgang, Eric
Jackson, Brian
Jackson, John R.
diff -r 94ffd6b18431 -r c2e36a80a279 doc/UPGRADE
--- a/doc/UPGRADE Mon Jan 04 10:47:11 2016 -0700
+++ b/doc/UPGRADE Sun Jan 10 18:31:29 2016 -0700
@@ -1,6 +1,15 @@
Notes on upgrading from an older release
========================================
+o Upgrading from a version prior to the post-1.8.15 fix for CVE-2015-5602.
+
+ The meaning of the sudoedit_checkdir sudoers option has changed.
+ Previously, it would only check the parent directory
+ of the file to be edited. After the CVE fix, all directories
+ in the path to be edited are checked and sudoedit will refuse
+ to follow a symbolic link in a directory that is writable by
+ the invoking user.
+
o Upgrading from a version prior to 1.8.15:
Prior to version 1.8.15, when env_reset was enabled (the default)
diff -r 94ffd6b18431 -r c2e36a80a279 doc/sudoers.cat
--- a/doc/sudoers.cat Mon Jan 04 10:47:11 2016 -0700
+++ b/doc/sudoers.cat Sun Jan 10 18:31:29 2016 -0700
@@ -1275,12 +1275,15 @@
system call. This flag is _o_f_f by default.
sudoedit_checkdir
- If set, ssuuddooeeddiitt will refuse to edit files located in a
- directory that is writable by the invoking user unless
- it is run by root. On many systems, this option
- requires that the parent directory of the file to be
- edited be readable by the target user. This flag is
- _o_f_f by default.
+ If set, ssuuddooeeddiitt will check directories in the path to
+ be edited for writability by the invoking user.
+ Symbolic links will not be followed in writable
+ directories and ssuuddooeeddiitt will also refuse to edit a
+ file located in a writable directory. Theses
+ restrictions are not enforced when ssuuddooeeddiitt is invoked
+ as root. On many systems, this option requires that
+ all directories in the path to be edited be readable by
+ the target user. This flag is _o_f_f by default.
sudoedit_follow By default, ssuuddooeeddiitt will not follow symbolic links
when opening files. The _s_u_d_o_e_d_i_t___f_o_l_l_o_w option can be
diff -r 94ffd6b18431 -r c2e36a80a279 doc/sudoers.man.in
--- a/doc/sudoers.man.in Mon Jan 04 10:47:11 2016 -0700
+++ b/doc/sudoers.man.in Sun Jan 10 18:31:29 2016 -0700
@@ -2715,10 +2715,16 @@
.br
If set,
\fBsudoedit\fR
-will refuse to edit files located in a directory that is writable
-by the invoking user unless it is run by root.
-On many systems, this option requires that the parent directory
-of the file to be edited be readable by the target user.
+will check directories in the path to be edited for writability
+by the invoking user.
+Symbolic links will not be followed in writable directories and
+\fBsudoedit\fR
+will also refuse to edit a file located in a writable directory.
+Theses restrictions are not enforced when
+\fBsudoedit\fR
+is invoked as root.
+On many systems, this option requires that all directories
+in the path to be edited be readable by the target user.
This flag is
\fIoff\fR
by default.
diff -r 94ffd6b18431 -r c2e36a80a279 doc/sudoers.mdoc.in
--- a/doc/sudoers.mdoc.in Mon Jan 04 10:47:11 2016 -0700
+++ b/doc/sudoers.mdoc.in Sun Jan 10 18:31:29 2016 -0700
@@ -2549,10 +2549,16 @@
.It sudoedit_checkdir
If set,
.Nm sudoedit
-will refuse to edit files located in a directory that is writable
-by the invoking user unless it is run by root.
-On many systems, this option requires that the parent directory
-of the file to be edited be readable by the target user.
+will check directories in the path to be edited for writability
+by the invoking user.
+Symbolic links will not be followed in writable directories and
+.Nm sudoedit
+will also refuse to edit a file located in a writable directory.
+Theses restrictions are not enforced when
+.Nm sudoedit
+is invoked as root.
+On many systems, this option requires that all directories
+in the path to be edited be readable by the target user.
This flag is
.Em off
by default.
diff -r 94ffd6b18431 -r c2e36a80a279 include/sudo_compat.h
--- a/include/sudo_compat.h Mon Jan 04 10:47:11 2016 -0700
+++ b/include/sudo_compat.h Sun Jan 10 18:31:29 2016 -0700
@@ -182,6 +182,8 @@
# ifndef UTIME_NOW
# define UTIME_NOW -2L
# endif
+#endif
+#if !defined(HAVE_OPENAT) || (!defined(HAVE_FUTIMENS) && !defined(HAVE_UTIMENSAT))
# ifndef AT_FDCWD
# define AT_FDCWD -100
# endif
diff -r 94ffd6b18431 -r c2e36a80a279 src/sudo_edit.c
--- a/src/sudo_edit.c Mon Jan 04 10:47:11 2016 -0700
+++ b/src/sudo_edit.c Sun Jan 10 18:31:29 2016 -0700
@@ -179,13 +179,15 @@
}
#ifndef HAVE_OPENAT
-/* This does not support AT_FDCWD... */
static int
sudo_openat(int dfd, const char *path, int flags, mode_t mode)
{
int fd, odfd;
debug_decl(sudo_openat, SUDO_DEBUG_EDIT)
+ if (dfd == AT_FDCWD)
+ debug_return_int(open(path, flags, mode));
+
/* Save cwd */
if ((odfd = open(".", O_RDONLY)) == -1)
debug_return_int(-1);
@@ -207,6 +209,64 @@
#define openat sudo_openat
#endif /* HAVE_OPENAT */
+#ifdef O_NOFOLLOW
+static int
+sudo_edit_openat_nofollow(int dfd, char *path, int oflags, mode_t mode)
+{
+ debug_decl(sudo_edit_open_nofollow, SUDO_DEBUG_EDIT)
+
+ debug_return_int(openat(dfd, path, oflags|O_NOFOLLOW, mode));
+}
+#else
+/*
+ * Returns true if fd and path don't match or path is a symlink.
+ * Used on older systems without O_NOFOLLOW.
+ */
+static bool
+sudo_edit_is_symlink(int fd, char *path)
+{
+ struct stat sb1, sb2;
+ debug_decl(sudo_edit_is_symlink, SUDO_DEBUG_EDIT)
+
+ /*
+ * Treat [fl]stat() failure like there was a symlink.
+ */
+ if (fstat(fd, &sb1) == -1 || lstat(path, &sb2) == -1)
+ debug_return_bool(true);
+
+ /*
+ * Make sure we did not open a link and that what we opened
+ * matches what is currently on the file system.
+ */
+ if (S_ISLNK(sb2.st_mode) ||
+ sb1.st_dev != sb2.st_dev || sb1.st_ino != sb2.st_ino) {
+ debug_return_bool(true);
+ }
+
+ debug_return_bool(false);
+}
+
+static int
+sudo_edit_openat_nofollow(char *path, int oflags, mode_t mode)
+{
+ struct stat sb1, sb2;
+ int fd;
+ debug_decl(sudo_edit_openat_nofollow, SUDO_DEBUG_EDIT)
+
+ fd = openat(dfd, path, oflags, mode);
+ if (fd == -1)
+ debug_return_int(-1);
+
+ if (sudo_edit_is_symlink(fd, path)) {
+ close(fd);
+ fd = -1;
+ errno = ELOOP;
+ }
+
+ debug_return_int(fd);
+}
+#endif /* O_NOFOLLOW */
+
/*
* Returns true if the directory described by sb is writable
* by the user. We treat directories with the sticky bit as
@@ -245,49 +305,94 @@
debug_return_bool(false);
}
+/*
+ * Directory open flags for use with openat(2) and fstat(2).
+ * Use O_PATH and O_DIRECTORY where possible.
+ */
+#if defined(O_PATH) && defined(O_DIRECTORY)
+# define DIR_OPEN_FLAGS (O_PATH|O_DIRECTORY)
+#elif defined(O_PATH) && !defined(O_DIRECTORY)
+# define DIR_OPEN_FLAGS O_PATH
+#elif !defined(O_PATH) && defined(O_DIRECTORY)
+# define DIR_OPEN_FLAGS (O_RDONLY|O_DIRECTORY)
+#else
+# define DIR_OPEN_FLAGS (O_RDONLY|O_NONBLOCK)
+#endif
+
static int
sudo_edit_open_nonwritable(char *path, int oflags, mode_t mode)
{
- char *base, *dir;
+ int dfd, fd, dflags = DIR_OPEN_FLAGS;
+#if defined(__linux__) && defined(O_PATH)
+ char *opath = path;
+#endif
+ bool is_writable;
struct stat sb;
- int dfd, fd;
debug_decl(sudo_edit_open_nonwritable, SUDO_DEBUG_EDIT)
- base = strrchr(path, '/');
- if (base != NULL) {
- *base++ = '\0';
- dir = path;
+#if defined(__linux__) && defined(O_PATH)
+restart:
+#endif
+ if (path[0] == '/') {
+ dfd = open("/", dflags);
+ path++;
} else {
- base = path;
- dir = ".";
+ dfd = open(".", dflags);
+ if (path[0] == '.' && path[1] == '/')
+ path += 2;
}
-#ifdef O_PATH
- if ((dfd = open(dir, O_PATH)) != -1) {
- /* Linux kernels < 3.6 can't do fstat on O_PATH fds. */
- if (fstat(dfd, &sb) == -1) {
- close(dfd);
- dfd = open(dir, O_RDONLY);
- if (fstat(dfd, &sb) == -1) {
- close(dfd);
- dfd = -1;
- }
- }
- }
-#else
- if ((dfd = open(dir, O_RDONLY)) != -1) {
- if (fstat(dfd, &sb) == -1) {
- close(dfd);
- dfd = -1;
- }
- }
-#endif
- if (base != path)
- base[-1] = '/'; /* restore path */
if (dfd == -1)
debug_return_int(-1);
- if (dir_is_writable(&sb, user_details.uid, user_details.gid,
- user_details.ngroups, user_details.groups)) {
+ for (;;) {
+ char *slash;
+ int subdfd;
+
+ /*
+ * Look up one component at a time, avoiding symbolic links in
+ * writable directories.
+ */
+ if (fstat(dfd, &sb) == -1) {
+ close(dfd);
+#if defined(__linux__) && defined(O_PATH)
+ /* Linux prior to 3.6 can't fstat an O_PATH fd */
+ if (ISSET(dflags, O_PATH)) {
+ CLR(dflags, O_PATH);
+ path = opath;
+ goto restart;
+ }
+#endif
+ debug_return_int(-1);
+ }
+#ifndef O_DIRECTORY
+ if (!S_ISDIR(sb.st_mode)) {
+ close(dfd);
+ errno = ENOTDIR;
+ debug_return_int(-1);
+ }
+#endif
+ is_writable = dir_is_writable(&sb, user_details.uid, user_details.gid,
+ user_details.ngroups, user_details.groups);
+
+ while (path[0] == '/')
+ path++;
+ slash = strchr(path, '/');
+ if (slash == NULL)
+ break;
+ *slash = '\0';
+ if (is_writable)
+ subdfd = sudo_edit_openat_nofollow(dfd, path, dflags, 0);
+ else
+ subdfd = openat(dfd, path, dflags, 0);
+ *slash = '/'; /* restore path */
+ close(dfd);
+ if (subdfd == -1)
+ debug_return_int(-1);
+ path = slash + 1;
+ dfd = subdfd;
+ }
+
+ if (is_writable) {
close(dfd);
errno = EISDIR;
debug_return_int(-1);
@@ -332,27 +437,10 @@
if (!ISSET(oflags, O_NONBLOCK))
(void) fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) & ~O_NONBLOCK);
- /*
- * Treat [fl]stat() failure like an open() failure.
- */
- if (fstat(fd, &sb1) == -1 || lstat(path, &sb2) == -1) {
- const int serrno = errno;
+ if (!ISSET(sflags, CD_SUDOEDIT_FOLLOW) && sudo_edit_is_symlink(fd, path)) {
close(fd);
- errno = serrno;
- debug_return_int(-1);
- }
-
- /*
- * Make sure we did not open a link and that what we opened
- * matches what is currently on the file system.
- */
- if (!ISSET(sflags, CD_SUDOEDIT_FOLLOW)) {
- if (S_ISLNK(sb2.st_mode) ||
- sb1.st_dev != sb2.st_dev || sb1.st_ino != sb2.st_ino) {
- close(fd);
- errno = ELOOP;
- debug_return_int(-1);
- }
+ fd = -1;
+ errno = ELOOP;
}
debug_return_int(fd);