Re: [PATCH 1/3] Security: Add disablenetwork interface. (v4)

[Serge E. Hallyn]

Quoting Serge E. Hallyn (serge@xxxxxxxxxx):
> Quoting Michael Stone (michael@xxxxxxxxxx):
> > Daniel Bernstein has observed [1] that security-conscious userland processes
> > may benefit from the ability to irrevocably remove their ability to create,
> > bind, connect to, or send messages except in the case of previously connected
> > sockets or AF_UNIX filesystem sockets.
> > 
> > This patch provides
> > 
> >    * a new configuration option named CONFIG_SECURITY_DISABLENETWORK,
> >    * a new prctl option-pair (PR_SET_NETWORK, PR_GET_NETWORK),
> >    * a new prctl(PR_SET_NETWORK) flag named PR_NETWORK_OFF, and
> >    * a new task_struct flags field named "network"
> > 
> > Signed-off-by: Michael Stone <michael@xxxxxxxxxx>
> > ---
> >   include/linux/prctl.h         |    7 +++++
> >   include/linux/prctl_network.h |    7 +++++
> >   include/linux/sched.h         |    4 +++
> >   kernel/sys.c                  |   53 +++++++++++++++++++++++++++++++++++++++++
> >   security/Kconfig              |   11 ++++++++
> >   5 files changed, 82 insertions(+), 0 deletions(-)
> >   create mode 100644 include/linux/prctl_network.h
> > 
> > diff --git a/include/linux/prctl.h b/include/linux/prctl.h
> > index a3baeb2..4eb4110 100644
> > --- a/include/linux/prctl.h
> > +++ b/include/linux/prctl.h
> > @@ -102,4 +102,11 @@
> >   
> >   #define PR_MCE_KILL_GET 34
> >   
> > +/* Get/set process disable-network flags */
> > +#define PR_SET_NETWORK	35
> > +#define PR_GET_NETWORK	36
> > +# define PR_NETWORK_ON        0
> > +# define PR_NETWORK_OFF       1
> > +# define PR_NETWORK_ALL_FLAGS 1
> > +
> >   #endif /* _LINUX_PRCTL_H */
> > diff --git a/include/linux/prctl_network.h b/include/linux/prctl_network.h
> > new file mode 100644
> > index 0000000..d18f8cb
> > --- /dev/null
> > +++ b/include/linux/prctl_network.h
> > @@ -0,0 +1,7 @@
> > +#ifndef _LINUX_PRCTL_NETWORK_H
> > +#define _LINUX_PRCTL_NETWORK_H
> > +
> > +extern long prctl_get_network(unsigned long*);
> > +extern long prctl_set_network(unsigned long*);
> > +
> > +#endif /* _LINUX_PRCTL_NETWORK_H */
> > diff --git a/include/linux/sched.h b/include/linux/sched.h
> > index f2f842d..6fcaef8 100644
> > --- a/include/linux/sched.h
> > +++ b/include/linux/sched.h
> > @@ -1403,6 +1403,10 @@ struct task_struct {
> >   #endif
> >   	seccomp_t seccomp;
> >   
> > +#ifdef CONFIG_SECURITY_DISABLENETWORK
> > +  unsigned long network;
> > +#endif
> > +
> >   /* Thread group tracking */
> >      	u32 parent_exec_id;
> >      	u32 self_exec_id;
> > diff --git a/kernel/sys.c b/kernel/sys.c
> > index 26a6b73..b48f021 100644
> > --- a/kernel/sys.c
> > +++ b/kernel/sys.c
> > @@ -35,6 +35,7 @@
> >   #include <linux/cpu.h>
> >   #include <linux/ptrace.h>
> >   #include <linux/fs_struct.h>
> > +#include <linux/prctl_network.h>
> >   
> >   #include <linux/compat.h>
> >   #include <linux/syscalls.h>
> > @@ -1578,6 +1579,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
> >   			else
> >   				error = PR_MCE_KILL_DEFAULT;
> >   			break;
> > +		case PR_SET_NETWORK:
> > +			error = prctl_set_network((unsigned long*)arg2);
> > +			break;
> > +		case PR_GET_NETWORK:
> > +			error = prctl_get_network((unsigned long*)arg2);
> > +			break;
> 
> Is there any reason not to handle these in
> 	disablenetwork_security_prctl()
> ?
> 
> Other than that, this looks quite good to me...  (No need to
> initialize ret=0 in your security_* updates, to get pedantic,
> that's all I noticed)
> 
> I'll give it a closer look on monday before I ack.

But I'm going to wait to see a response (or new patch) about moving
this code to disablenetwork_security_prctl().

thanks,
-serge
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