This adds PR_{GET,SET}_NO_NEW_PRIVS. As an example of its use, it
allows some unshare operations and (sometimes) chroot when no_new_privs
is set. Another example is the experimental pam module here:
http://web.mit.edu/luto/www/linux/
After some impressively long mailing list threads, I still think that
blocking setresuid, setuid, and capset in no_new_privs mode is
unnecessary and overcomplicated. Additionally, blocking those calls
will make my pam module either fail or become a giant security hole
(depending on how carefully the core pam stuff is written -- I haven't
checked).
Changes from v2:
- Rebased onto a very recent -linus tree.
- Changed prctl numbering. (Needed because prctl 35 is now taken.)
- Fixed a typo or two.
- Removed explicit propagation of no_new_privs. dup_task_struct is enough.
- Reworked the chroot patch. It now uses hopefully much more sane logic
to decide whether the user is chrooted. It also checks that fs is not
shared (which was a big security hole in the earlier version).
For the git-inclined, this series is here:
https://git.kernel.org/?p=linux/kernel/git/luto/linux.git;a=shortlog;h=refs/heads/security/no_new_privs/patch_v3
Test it like this:
---- begin test case
#include <sys/prctl.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#define PR_SET_NO_NEW_PRIVS 36
#define PR_GET_NO_NEW_PRIVS 37
int main()
{
int nnp = prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0);
if (nnp == -EINVAL) {
printf("Failed!\n");
return 1;
}
printf("nnp was %d\n", nnp);
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) != 0) {
printf("Failed!\n");
return 1;
}
nnp = prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0);
if (nnp == -EINVAL) {
printf("Failed!\n");
return 1;
}
printf("nnp is %d\n", nnp);
printf("here goes...\n");
execlp("bash", "bash", NULL);
printf("Failed to exec bash\n");
return 1;
}
---- end test case
Andy Lutomirski (3):
Add PR_{GET,SET}_NO_NEW_PRIVS to prevent execve from granting privs
Allow unprivileged CLONE_NEWUTS and CLONE_NEWIPC with no_new_privs
Allow unprivileged chroot when safe
John Johansen (1):
Fix apparmor for PR_{GET,SET}_NO_NEW_PRIVS
fs/exec.c | 10 ++++++++-
fs/open.c | 46 ++++++++++++++++++++++++++++++++++++++++++-
include/linux/prctl.h | 15 ++++++++++++++
include/linux/sched.h | 2 +
include/linux/security.h | 1 +
kernel/nsproxy.c | 8 ++++++-
kernel/sys.c | 10 +++++++++
security/apparmor/domain.c | 35 +++++++++++++++++++++++++++++++++
security/commoncap.c | 7 ++++-
security/selinux/hooks.c | 10 ++++++++-
10 files changed, 137 insertions(+), 7 deletions(-)
--
1.7.7.6
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