[Devel] Re: [PATCH 2/2] hijack: update task_alloc_security
Serge E. Hallyn
serue at us.ibm.com
Tue Nov 27 07:50:13 PST 2007
Quoting Rodrigo Rubira Branco (BSDaemon) (rodrigo at kernelhacking.com):
> It will give another easy way to locate selinux security structures inside
> the kernel, will not?
By locate, you mean actually finding the structures in kernel memory to
overwrite them?
> Again, if you have a kernel vulnerability and this feature, someone will
> easily disable selinux for the process, or just change the security concerns
> for it ;).
Maybe hijack should go under a kernel config for security reasons.
thanks,
-serge
> cya,
>
>
> Rodrigo (BSDaemon).
>
> --
> http://www.kernelhacking.com/rodrigo
>
> Kernel Hacking: If i really know, i can hack
>
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>
>
> --------- Mensagem Original --------
> De: Joshua Brindle <method at manicmethod.com>
> Para: Mark Nelson <markn at au1.ibm.com>
> C?pia: containers at lists.linux-foundation.org,
> linux-security-module at vger.kernel.org, selinux at tycho.nsa.gov,
> menage at google.com, Stephen Smalley <sds at tycho.nsa.gov>, James Morris
> <jmorris at namei.org>, Serge E. Hallyn <serue at us.ibm.com>
> Assunto: Re: [PATCH 2/2] hijack: update task_alloc_security
> Data: 27/11/07 02:38
>
> >
> > Mark Nelson wrote:
> > > Subject: [PATCH 2/2] hijack: update task_alloc_security
> > >
> > > Update task_alloc_security() to take the hijacked task as a second
> > > argument.
> > >
> > > For the selinux version, refuse permission if hijack_src!=current,
> > > since we have no idea what the proper behavior is. Even if we
> > > assume that the resulting child should be in the hijacked task's
> > > domain, depending on the policy that may not be enough information
> > > since init_t executing /bin/bash could result in a different domain
> > > than login_t executing /bin/bash.
> > >
> > >
> > This means its basically not possible to hijack tasks with SELinux
> > right? It would be a shame if this weren't useful to people running
> SELinux.
> >
> > It seems to me (I may be wrong, I'm sure someone will let me know if I
> > am) that the right way to handle this with SELinux is to check to see if
> > the current task (caller of sys_hijack) has permission to ptrace (or
> > some other permission deemed suitable, perhaps a new one) and if so copy
> > the security blob pointer from the hijacked task to the new one (we
> > don't want tranquility problems).
> >
> > From your paragraph above it seems like you were thinking there should
> > be a transition at hijack time but we don't automatically transition
> > anywhere except exec.
> >
> > Anyway, I just don't think you should completely disable this for
> > SELinux users.
> >
> > > Signed-off-by: Serge Hallyn <serue at us.ibm.com>
> > > Signed-off-by: Mark Nelson <markn at au1.ibm.com>
> > > ---
> > > include/linux/security.h | 12 +++++++++---
> > > kernel/fork.c | 2 +-
> > > security/dummy.c | 3 ++-
> > > security/security.c | 4 ++--
> > > security/selinux/hooks.c | 6 +++++-
> > > 5 files changed, 19 insertions(+), 8 deletions(-)
> > >
> > > Index: upstream/include/linux/security.h
> > > ===================================================================
> > > --- upstream.orig/include/linux/security.h
> > > +++ upstream/include/linux/security.h
> > > @@ -545,9 +545,13 @@ struct request_sock;
> > > * Return 0 if permission is granted.
> > > * @task_alloc_security:
> > > * @p contains the task_struct for child process.
> > > + * @task contains the task_struct for process to be hijacked
> > > * Allocate and attach a security structure to the p->security
> field. The
> > > * security field is initialized to NULL when the task structure is
> > > * allocated.
> > > + * @task will usually be current. If it is not equal to current,
> then
> > > + * a sys_hijack system call is going on, and current is asking for a
> > > + * child to be created in the context of the hijack src, @task.
> > > * Return 0 if operation was successful.
> > > * @task_free_security:
> > > * @p contains the task_struct for process.
> > > @@ -1301,7 +1305,8 @@ struct security_operations {
> > > int (*dentry_open) (struct file *file);
> > >
> > > int (*task_create) (unsigned long clone_flags);
> > > - int (*task_alloc_security) (struct task_struct * p);
> > > + int (*task_alloc_security) (struct task_struct *p,
> > > + struct task_struct *task);
> > > void (*task_free_security) (struct task_struct * p);
> > > int (*task_setuid) (uid_t id0, uid_t id1, uid_t id2, int flags);
> > > int (*task_post_setuid) (uid_t old_ruid /* or fsuid */ ,
> > > @@ -1549,7 +1554,7 @@ int security_file_send_sigiotask(struct
> > > int security_file_receive(struct file *file);
> > > int security_dentry_open(struct file *file);
> > > int security_task_create(unsigned long clone_flags);
> > > -int security_task_alloc(struct task_struct *p);
> > > +int security_task_alloc(struct task_struct *p, struct task_struct
> *task);
> > > void security_task_free(struct task_struct *p);
> > > int security_task_setuid(uid_t id0, uid_t id1, uid_t id2, int
> flags);
> > > int security_task_post_setuid(uid_t old_ruid, uid_t old_euid,
> > > @@ -2021,7 +2026,8 @@ static inline int security_task_create (
> > > return 0;
> > > }
> > >
> > > -static inline int security_task_alloc (struct task_struct *p)
> > > +static inline int security_task_alloc(struct task_struct *p,
> > > + struct task_struct *task)
> > > {
> > > return 0;
> > > }
> > > Index: upstream/kernel/fork.c
> > > ===================================================================
> > > --- upstream.orig/kernel/fork.c
> > > +++ upstream/kernel/fork.c
> > > @@ -1177,7 +1177,7 @@ static struct task_struct *copy_process(
> > > /* Perform scheduler related setup. Assign this task to a CPU. */
> > > sched_fork(p, clone_flags);
> > >
> > > - if ((retval = security_task_alloc(p)))
> > > + if ((retval = security_task_alloc(p, task)))
> > > goto bad_fork_cleanup_policy;
> > > if ((retval = audit_alloc(p)))
> > > goto bad_fork_cleanup_security;
> > > Index: upstream/security/dummy.c
> > > ===================================================================
> > > --- upstream.orig/security/dummy.c
> > > +++ upstream/security/dummy.c
> > > @@ -475,7 +475,8 @@ static int dummy_task_create (unsigned l
> > > return 0;
> > > }
> > >
> > > -static int dummy_task_alloc_security (struct task_struct *p)
> > > +static int dummy_task_alloc_security(struct task_struct *p,
> > > + struct task_struct *task)
> > > {
> > > return 0;
> > > }
> > > Index: upstream/security/security.c
> > > ===================================================================
> > > --- upstream.orig/security/security.c
> > > +++ upstream/security/security.c
> > > @@ -568,9 +568,9 @@ int security_task_create(unsigned long c
> > > return security_ops->task_create(clone_flags);
> > > }
> > >
> > > -int security_task_alloc(struct task_struct *p)
> > > +int security_task_alloc(struct task_struct *p, struct task_struct
> *task)
> > > {
> > > - return security_ops->task_alloc_security(p);
> > > + return security_ops->task_alloc_security(p, task);
> > > }
> > >
> > > void security_task_free(struct task_struct *p)
> > > Index: upstream/security/selinux/hooks.c
> > > ===================================================================
> > > --- upstream.orig/security/selinux/hooks.c
> > > +++ upstream/security/selinux/hooks.c
> > > @@ -2788,11 +2788,15 @@ static int selinux_task_create(unsigned
> > > return task_has_perm(current, current, PROCESS__FORK);
> > > }
> > >
> > > -static int selinux_task_alloc_security(struct task_struct *tsk)
> > > +static int selinux_task_alloc_security(struct task_struct *tsk,
> > > + struct task_struct *hijack_src)
> > > {
> > > struct task_security_struct *tsec1, *tsec2;
> > > int rc;
> > >
> > > + if (hijack_src != current)
> > > + return -EPERM;
> > > +
> > > tsec1 = current->security;
> > >
> > > rc = task_alloc_security(tsk);
> > > -
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