Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1298154

Re: [PATCH] ptrace: being capable wrt a process requires mapped uids/gids

Show all headers | View raw

[Multipart message — attachments visible in raw view] - view raw

On Sat, Dec 12, 2015 at 09:12:41PM +0100, Jann Horn wrote:
> With this change, the entering process can first enter the
> namespace and then safely inspect the namespace's
> properties, e.g. through /proc/self/{uid_map,gid_map},
> assuming that the namespace owner doesn't have access to
> uid 0.

Actually, I think I missed something there. Well, at least it
should not directly lead to a container escape.


> -static int ptrace_has_cap(struct user_namespace *ns, unsigned int mode)
> +static bool ptrace_has_cap(const struct cred *tcred, unsigned int mode)
>  {
> +	struct user_namespace *tns = tcred->user_ns;
> +	struct user_namespace *curns = current_cred()->user_ns;
> +
> +	/* When a root-owned process enters a user namespace created by a
> +	 * malicious user, the user shouldn't be able to execute code under
> +	 * uid 0 by attaching to the root-owned process via ptrace.
> +	 * Therefore, similar to the capable_wrt_inode_uidgid() check,
> +	 * verify that all the uids and gids of the target process are
> +	 * mapped into the current namespace.
> +	 * No fsuid/fsgid check because __ptrace_may_access doesn't do it
> +	 * either.
> +	 */
> +	if (!kuid_has_mapping(curns, tcred->euid) ||
> +			!kuid_has_mapping(curns, tcred->suid) ||
> +			!kuid_has_mapping(curns, tcred->uid)  ||
> +			!kgid_has_mapping(curns, tcred->egid) ||
> +			!kgid_has_mapping(curns, tcred->sgid) ||
> +			!kgid_has_mapping(curns, tcred->gid))
> +		return false;
> +
>  	if (mode & PTRACE_MODE_NOAUDIT)
> -		return has_ns_capability_noaudit(current, ns, CAP_SYS_PTRACE);
> +		return has_ns_capability_noaudit(current, tns, CAP_SYS_PTRACE);
>  	else
> -		return has_ns_capability(current, ns, CAP_SYS_PTRACE);
> +		return has_ns_capability(current, tns, CAP_SYS_PTRACE);
>  }

If the namespace owner can run code in the init namespace, the kuids are
mapped into curns but he is still capable wrt the target namespace.

I think a proper fix should first determine the highest parent of
tcred->user_ns in which the caller still has privs, then do the
kxid_has_mapping() checks in there.

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH] ptrace: being capable wrt a process requires mapped uids/gids Jann Horn <jann@thejh.net> - 2015-12-12 21:30 +0100
  Re: [PATCH] ptrace: being capable wrt a process requires mapped uids/gids Andy Lutomirski <luto@amacapital.net> - 2015-12-15 01:30 +0100
  Re: [PATCH] ptrace: being capable wrt a process requires mapped  uids/gids "Serge E. Hallyn" <serge.hallyn@ubuntu.com> - 2015-12-17 20:10 +0100
  Re: [PATCH] ptrace: being capable wrt a process requires mapped  uids/gids Jann Horn <jann@thejh.net> - 2015-12-26 02:20 +0100
    [PATCH] ptrace: being capable wrt a process requires mapped uids/gids Jann Horn <jann@thejh.net> - 2015-12-26 04:00 +0100
      Re: [PATCH] ptrace: being capable wrt a process requires mapped  uids/gids "Serge E. Hallyn" <serge.hallyn@ubuntu.com> - 2015-12-26 22:20 +0100
        Re: [PATCH] ptrace: being capable wrt a process requires mapped  uids/gids Jann Horn <jann@thejh.net> - 2015-12-26 22:30 +0100
          Re: [PATCH] ptrace: being capable wrt a process requires mapped  uids/gids "Serge E. Hallyn" <serge.hallyn@ubuntu.com> - 2015-12-26 23:00 +0100
      Re: [PATCH] ptrace: being capable wrt a process requires mapped  uids/gids "Serge E. Hallyn" <serge.hallyn@ubuntu.com> - 2015-12-26 23:00 +0100
        Re: [PATCH] ptrace: being capable wrt a process requires mapped uids/gids Andy Lutomirski <luto@amacapital.net> - 2015-12-27 03:10 +0100
    Re: [PATCH] ptrace: being capable wrt a process requires mapped  uids/gids "Serge E. Hallyn" <serge.hallyn@ubuntu.com> - 2015-12-26 21:30 +0100
      Re: [PATCH] ptrace: being capable wrt a process requires mapped  uids/gids Jann Horn <jann@thejh.net> - 2015-12-26 22:00 +0100
        Re: [PATCH] ptrace: being capable wrt a process requires mapped  uids/gids "Serge E. Hallyn" <serge.hallyn@ubuntu.com> - 2015-12-26 22:10 +0100

csiph-web