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Message-ID: <CAGXu5j+RLXgO=N=h1qGfsZnzFdD6h7DcH7oTdXdib_Tn7bv4rA@mail.gmail.com>
Date: Tue, 4 Nov 2014 10:47:52 -0800
From: Kees Cook <keescook@...omium.org>
To: David Drysdale <drysdale@...gle.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Meredydd Luff <meredydd@...atehouse.org>,
Will Drewry <wad@...omium.org>,
Jorge Lucangeli Obes <jorgelo@...gle.com>,
Ricky Zhou <rickyz@...gle.com>,
Lee Campbell <leecam@...gle.com>,
Julien Tinnes <jln@...gle.com>,
Mike Depinet <mdepinet@...gle.com>,
James Morris <james.l.morris@...cle.com>,
Andy Lutomirski <luto@...capital.net>,
Paolo Bonzini <pbonzini@...hat.com>,
Paul Moore <paul@...l-moore.com>,
Christoph Hellwig <hch@...radead.org>,
Linux API <linux-api@...r.kernel.org>,
linux-security-module <linux-security-module@...r.kernel.org>
Subject: Re: [PATCHv2 2/3] selftests: Add test of O_BENEATH & openat(2)
On Tue, Nov 4, 2014 at 1:54 AM, David Drysdale <drysdale@...gle.com> wrote:
> Add simple tests of openat(2) variations, including examples that
> check the new O_BENEATH flag.
>
> Signed-off-by: David Drysdale <drysdale@...gle.com>
Excellent! Thank you for including self tests. :)
Acked-by: Kees Cook <keescook@...omium.org>
-Kees
> ---
> tools/testing/selftests/Makefile | 1 +
> tools/testing/selftests/openat/.gitignore | 4 +
> tools/testing/selftests/openat/Makefile | 28 +++++
> tools/testing/selftests/openat/openat.c | 180 ++++++++++++++++++++++++++++++
> 4 files changed, 213 insertions(+)
> create mode 100644 tools/testing/selftests/openat/.gitignore
> create mode 100644 tools/testing/selftests/openat/Makefile
> create mode 100644 tools/testing/selftests/openat/openat.c
>
> diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
> index 36ff2e4c7b6f..812e973233d2 100644
> --- a/tools/testing/selftests/Makefile
> +++ b/tools/testing/selftests/Makefile
> @@ -14,6 +14,7 @@ TARGETS += powerpc
> TARGETS += user
> TARGETS += sysctl
> TARGETS += firmware
> +TARGETS += openat
>
> TARGETS_HOTPLUG = cpu-hotplug
> TARGETS_HOTPLUG += memory-hotplug
> diff --git a/tools/testing/selftests/openat/.gitignore b/tools/testing/selftests/openat/.gitignore
> new file mode 100644
> index 000000000000..835b2dcd8678
> --- /dev/null
> +++ b/tools/testing/selftests/openat/.gitignore
> @@ -0,0 +1,4 @@
> +openat
> +subdir
> +topfile
> +symlinkdown
> \ No newline at end of file
> diff --git a/tools/testing/selftests/openat/Makefile b/tools/testing/selftests/openat/Makefile
> new file mode 100644
> index 000000000000..84cd06e7ee82
> --- /dev/null
> +++ b/tools/testing/selftests/openat/Makefile
> @@ -0,0 +1,28 @@
> +CC = $(CROSS_COMPILE)gcc
> +CFLAGS = -Wall
> +BINARIES = openat
> +DEPS = subdir topfile symlinkdown subdir/bottomfile subdir/symlinkup subdir/symlinkout subdir/symlinkin
> +all: $(BINARIES) $(DEPS)
> +
> +subdir:
> + mkdir -p subdir
> +topfile:
> + echo 0123456789 > $@
> +subdir/bottomfile: | subdir
> + echo 0123456789 > $@
> +subdir/symlinkup: | subdir
> + ln -s ../topfile $@
> +subdir/symlinkout: | subdir
> + ln -s /etc/passwd $@
> +subdir/symlinkin: | subdir
> + ln -s bottomfile $@
> +symlinkdown:
> + ln -s subdir/bottomfile $@
> +%: %.c
> + $(CC) $(CFLAGS) -o $@ $^
> +
> +run_tests: all
> + ./openat
> +
> +clean:
> + rm -rf $(BINARIES) $(DEPS)
> diff --git a/tools/testing/selftests/openat/openat.c b/tools/testing/selftests/openat/openat.c
> new file mode 100644
> index 000000000000..0c030cbd10dc
> --- /dev/null
> +++ b/tools/testing/selftests/openat/openat.c
> @@ -0,0 +1,180 @@
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <sys/syscall.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +#include <string.h>
> +#include <errno.h>
> +
> +#include <linux/fcntl.h>
> +
> +/* Bypass glibc */
> +static int openat_(int dirfd, const char *pathname, int flags)
> +{
> + return syscall(__NR_openat, dirfd, pathname, flags);
> +}
> +
> +static int openat_or_die(int dfd, const char *path, int flags)
> +{
> + int fd = openat_(dfd, path, flags);
> +
> + if (fd < 0) {
> + printf("Failed to openat(%d, '%s'); "
> + "check prerequisites are available\n", dfd, path);
> + exit(1);
> + }
> + return fd;
> +}
> +
> +static int check_openat(int dfd, const char *path, int flags)
> +{
> + int rc;
> + int fd;
> + char buffer[4];
> +
> + errno = 0;
> + printf("Check success of openat(%d, '%s', %x)... ",
> + dfd, path?:"(null)", flags);
> + fd = openat_(dfd, path, flags);
> + if (fd < 0) {
> + printf("[FAIL]: openat() failed, rc=%d errno=%d (%s)\n",
> + fd, errno, strerror(errno));
> + return 1;
> + }
> + errno = 0;
> + rc = read(fd, buffer, sizeof(buffer));
> + if (rc < 0) {
> + printf("[FAIL]: read() failed, rc=%d errno=%d (%s)\n",
> + rc, errno, strerror(errno));
> + return 1;
> + }
> + close(fd);
> + printf("[OK]\n");
> + return 0;
> +}
> +
> +#define check_openat_fail(dfd, path, flags, errno) \
> + _check_openat_fail(dfd, path, flags, errno, #errno)
> +static int _check_openat_fail(int dfd, const char *path, int flags,
> + int expected_errno, const char *errno_str)
> +{
> + int rc;
> +
> + errno = 0;
> + printf("Check failure of openat(%d, '%s', %x) with %s... ",
> + dfd, path?:"(null)", flags, errno_str);
> + rc = openat_(dfd, path, flags);
> + if (rc > 0) {
> + printf("[FAIL] (unexpected success from openat(2))\n");
> + close(rc);
> + return 1;
> + }
> + if (errno != expected_errno) {
> + printf("[FAIL] (expected errno %d (%s) not %d (%s)\n",
> + expected_errno, strerror(expected_errno),
> + errno, strerror(errno));
> + return 1;
> + }
> + printf("[OK]\n");
> + return 0;
> +}
> +
> +int check_proc(void)
> +{
> + int proc_dfd = openat_(AT_FDCWD, "/proc/self", O_RDONLY);
> + int fail = 0;
> +
> + if (proc_dfd < 0) {
> + printf("'/proc/self' unavailable (errno=%d '%s'), skipping\n",
> + errno, strerror(errno));
> + return 1;
> + }
> + fail |= check_openat(proc_dfd, "root/etc/passwd", O_RDONLY);
> +#ifdef O_BENEATH
> + fail |= check_openat_fail(proc_dfd, "root/etc/passwd",
> + O_RDONLY|O_BENEATH, EPERM);
> +#endif
> + return fail;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + int fail = 0;
> + int dot_dfd = openat_or_die(AT_FDCWD, ".", O_RDONLY);
> + int subdir_dfd = openat_or_die(AT_FDCWD, "subdir", O_RDONLY);
> + int file_fd = openat_or_die(AT_FDCWD, "topfile", O_RDONLY);
> +
> + /* Sanity check normal behavior */
> + fail |= check_openat(AT_FDCWD, "topfile", O_RDONLY);
> + fail |= check_openat(AT_FDCWD, "subdir/bottomfile", O_RDONLY);
> +
> + fail |= check_openat(dot_dfd, "topfile", O_RDONLY);
> + fail |= check_openat(dot_dfd, "subdir/bottomfile", O_RDONLY);
> + fail |= check_openat(dot_dfd, "subdir/../topfile", O_RDONLY);
> +
> + fail |= check_openat(subdir_dfd, "../topfile", O_RDONLY);
> + fail |= check_openat(subdir_dfd, "bottomfile", O_RDONLY);
> + fail |= check_openat(subdir_dfd, "../subdir/bottomfile", O_RDONLY);
> + fail |= check_openat(subdir_dfd, "symlinkup", O_RDONLY);
> + fail |= check_openat(subdir_dfd, "symlinkout", O_RDONLY);
> +
> + fail |= check_openat(AT_FDCWD, "/etc/passwd", O_RDONLY);
> + fail |= check_openat(dot_dfd, "/etc/passwd", O_RDONLY);
> + fail |= check_openat(subdir_dfd, "/etc/passwd", O_RDONLY);
> +
> + fail |= check_openat_fail(AT_FDCWD, "bogus", O_RDONLY, ENOENT);
> + fail |= check_openat_fail(dot_dfd, "bogus", O_RDONLY, ENOENT);
> + fail |= check_openat_fail(999, "bogus", O_RDONLY, EBADF);
> + fail |= check_openat_fail(file_fd, "bogus", O_RDONLY, ENOTDIR);
> +
> +#ifdef O_BENEATH
> + /* Test out O_BENEATH */
> + fail |= check_openat(AT_FDCWD, "topfile", O_RDONLY|O_BENEATH);
> + fail |= check_openat(AT_FDCWD, "subdir/bottomfile",
> + O_RDONLY|O_BENEATH);
> +
> + fail |= check_openat(dot_dfd, "topfile", O_RDONLY|O_BENEATH);
> + fail |= check_openat(dot_dfd, "subdir/bottomfile",
> + O_RDONLY|O_BENEATH);
> + fail |= check_openat(subdir_dfd, "bottomfile", O_RDONLY|O_BENEATH);
> +
> + /* Symlinks without .. or leading / are OK */
> + fail |= check_openat(dot_dfd, "symlinkdown", O_RDONLY|O_BENEATH);
> + fail |= check_openat(dot_dfd, "subdir/symlinkin", O_RDONLY|O_BENEATH);
> + fail |= check_openat(subdir_dfd, "symlinkin", O_RDONLY|O_BENEATH);
> + /* ... unless of course we specify O_NOFOLLOW */
> + fail |= check_openat_fail(dot_dfd, "symlinkdown",
> + O_RDONLY|O_BENEATH|O_NOFOLLOW, ELOOP);
> + fail |= check_openat_fail(dot_dfd, "subdir/symlinkin",
> + O_RDONLY|O_BENEATH|O_NOFOLLOW, ELOOP);
> + fail |= check_openat_fail(subdir_dfd, "symlinkin",
> + O_RDONLY|O_BENEATH|O_NOFOLLOW, ELOOP);
> +
> + /* Can't open paths with ".." in them */
> + fail |= check_openat_fail(dot_dfd, "subdir/../topfile",
> + O_RDONLY|O_BENEATH, EPERM);
> + fail |= check_openat_fail(subdir_dfd, "../topfile",
> + O_RDONLY|O_BENEATH, EPERM);
> + fail |= check_openat_fail(subdir_dfd, "../subdir/bottomfile",
> + O_RDONLY|O_BENEATH, EPERM);
> +
> + /* Can't open paths starting with "/" */
> + fail |= check_openat_fail(AT_FDCWD, "/etc/passwd",
> + O_RDONLY|O_BENEATH, EPERM);
> + fail |= check_openat_fail(dot_dfd, "/etc/passwd",
> + O_RDONLY|O_BENEATH, EPERM);
> + fail |= check_openat_fail(subdir_dfd, "/etc/passwd",
> + O_RDONLY|O_BENEATH, EPERM);
> + /* Can't sneak around constraints with symlinks */
> + fail |= check_openat_fail(subdir_dfd, "symlinkup",
> + O_RDONLY|O_BENEATH, EPERM);
> + fail |= check_openat_fail(subdir_dfd, "symlinkout",
> + O_RDONLY|O_BENEATH, EPERM);
> +#else
> + printf("Skipping O_BENEATH tests due to missing #define\n");
> +#endif
> + fail |= check_proc();
> +
> + return fail ? -1 : 0;
> +}
> --
> 2.1.0.rc2.206.gedb03e5
>
--
Kees Cook
Chrome OS Security
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