Date: Sat, 24 Aug 2013 13:50:01 GMT From: Oliver Pinter <oliver.pntr@gmail.com> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/181497: ASLR Feature Request - patch included Message-ID: <201308241350.r7ODo12O084969@freefall.freebsd.org>
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The following reply was made to PR kern/181497; it has been noted by GNATS. From: Oliver Pinter <oliver.pntr@gmail.com> To: Steven Lee <steven@roothosts.com> Cc: freebsd-gnats-submit@freebsd.org Subject: Re: kern/181497: ASLR Feature Request - patch included Date: Sat, 24 Aug 2013 15:48:49 +0200 new version of the patchset: https://github.com/opntr/freebsd-patches-2013-tavasz/tree/master/r249952+ASLR On 8/24/13, Steven Lee <steven@roothosts.com> wrote: > >>Number: 181497 >>Category: kern >>Synopsis: ASLR Feature Request - patch included >>Confidential: no >>Severity: non-critical >>Priority: low >>Responsible: freebsd-bugs >>State: open >>Quarter: >>Keywords: >>Date-Required: >>Class: change-request >>Submitter-Id: current-users >>Arrival-Date: Sat Aug 24 02:20:00 UTC 2013 >>Closed-Date: >>Last-Modified: >>Originator: Steven Lee >>Release: releng/9.2 >>Organization: > Root Hosts >>Environment: > N/A >>Description: > Most modern operating systems have ASLR to help mitigate yet-unknown > vulnerabilities. > > It would be very nice if FreeBSD shipped with ASLR features in the kernel > (default off), that could be easily switched on with a sysctl variable. > > I understand that in some production environments ASLR may make a system > slower through memory fragmentation, but at least give people the option to > turn ASLR on for those who actually want it. :) > >>How-To-Repeat: > N/A >>Fix: > This patch has been circulating the internet since FreeBSD 7.0-RELEASE at > least. It looks like parts of it are from OpenBSD? (I could be wrong.) I've > used it in production for many many years and it works like a champ. > > The patch will just need the sysctl defaults inverted and the variable names > possibly renamed for clarity. > > > Patch attached with submission follows: > > commit 779a962519e7ead63dda24348b98f6cde8156752 > Author: Oliver Pinter <opn@opn.(none)> > Date: Tue Oct 4 00:24:01 2011 +0200 > > forwardport mmap-randomization patch from 7-STABLE-op > > Signed-off-by: Oliver Pinter <oliver.pntr@gmail.com> > > diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c > index fe01142..dc66db6 100644 > --- a/sys/kern/kern_exec.c > +++ b/sys/kern/kern_exec.c > @@ -106,6 +106,7 @@ MALLOC_DEFINE(M_PARGS, "proc-args", "Process > arguments"); > static int sysctl_kern_ps_strings(SYSCTL_HANDLER_ARGS); > static int sysctl_kern_usrstack(SYSCTL_HANDLER_ARGS); > static int sysctl_kern_stackprot(SYSCTL_HANDLER_ARGS); > +static int sysctl_kern_stackgap_random(SYSCTL_HANDLER_ARGS); > static int do_execve(struct thread *td, struct image_args *args, > struct mac *mac_p); > > @@ -120,6 +121,9 @@ SYSCTL_PROC(_kern, KERN_USRSTACK, usrstack, > CTLTYPE_ULONG|CTLFLAG_RD| > SYSCTL_PROC(_kern, OID_AUTO, stackprot, CTLTYPE_INT|CTLFLAG_RD, > NULL, 0, sysctl_kern_stackprot, "I", ""); > > +SYSCTL_PROC(_kern, OID_AUTO, stackgap_random, CTLTYPE_INT|CTLFLAG_RW, > + NULL, 0, sysctl_kern_stackgap_random, "I", "stackgap maximum offset"); > + > u_long ps_arg_cache_limit = PAGE_SIZE / 16; > SYSCTL_ULONG(_kern, OID_AUTO, ps_arg_cache_limit, CTLFLAG_RW, > &ps_arg_cache_limit, 0, ""); > @@ -177,6 +181,30 @@ sysctl_kern_stackprot(SYSCTL_HANDLER_ARGS) > sizeof(p->p_sysent->sv_stackprot))); > } > > +static int stackgap_random = 64 * 1024; > + > +static int > +sysctl_kern_stackgap_random(SYSCTL_HANDLER_ARGS) > +{ > + int err; > + int val; > + > + val=stackgap_random; > + err=sysctl_handle_int(oidp, &val, sizeof(int), req); > + if (err || !req->newptr) { > + return (err); > + } > + > + if ((val<ALIGNBYTES && (val!=0)) > + || !powerof2(val) || val>64*1024*1024) { > + return (EINVAL); > + } > + > + stackgap_random=val; > + > + return (0); > +} > + > /* > * Each of the items is a pointer to a `const struct execsw', hence the > * double pointer here. > @@ -1248,6 +1276,7 @@ exec_copyout_strings(imgp) > size_t execpath_len; > int szsigcode, szps; > char canary[sizeof(long) * 8]; > + int sgap; > > szps = sizeof(pagesizes[0]) * MAXPAGESIZES; > /* > @@ -1265,7 +1294,11 @@ exec_copyout_strings(imgp) > if (p->p_sysent->sv_szsigcode != NULL) > szsigcode = *(p->p_sysent->sv_szsigcode); > } > - destp = (caddr_t)arginfo - szsigcode - SPARE_USRSPACE - > + sgap=0; > + if (stackgap_random!=0) { > + sgap=ALIGN(arc4random()&(stackgap_random-1)); > + } > + destp = (caddr_t)arginfo - szsigcode - SPARE_USRSPACE - sgap - > roundup(execpath_len, sizeof(char *)) - > roundup(sizeof(canary), sizeof(char *)) - > roundup(szps, sizeof(char *)) - > diff --git a/sys/vm/vm_mmap.c b/sys/vm/vm_mmap.c > index e85b681..991a37d 100644 > --- a/sys/vm/vm_mmap.c > +++ b/sys/vm/vm_mmap.c > @@ -68,6 +68,7 @@ __FBSDID("$FreeBSD$"); > #include <sys/stat.h> > #include <sys/sysent.h> > #include <sys/vmmeter.h> > +#include <sys/sysctl.h> > > #include <security/mac/mac_framework.h> > > @@ -99,6 +100,10 @@ static int vm_mmap_cdev(struct thread *, vm_size_t, > vm_prot_t, vm_prot_t *, > static int vm_mmap_shm(struct thread *, vm_size_t, vm_prot_t, vm_prot_t *, > int *, struct shmfd *, vm_ooffset_t, vm_object_t *); > > +static int mmap_random=1; > +SYSCTL_INT(_vm, OID_AUTO, mmap_random, CTLFLAG_RW, &mmap_random, 0, > + "random mmap offset"); > + > /* > * MPSAFE > */ > @@ -256,7 +261,8 @@ sys_mmap(td, uap) > /* > * XXX for non-fixed mappings where no hint is provided or > * the hint would fall in the potential heap space, > - * place it after the end of the largest possible heap. > + * place it after the end of the largest possible heap, > + * plus a random offset, if mmap_random is set. > * > * There should really be a pmap call to determine a reasonable > * location. > @@ -265,9 +271,13 @@ sys_mmap(td, uap) > if (addr == 0 || > (addr >= round_page((vm_offset_t)vms->vm_taddr) && > addr < round_page((vm_offset_t)vms->vm_daddr + > - lim_max(td->td_proc, RLIMIT_DATA)))) > + lim_max(td->td_proc, RLIMIT_DATA)))) { > addr = round_page((vm_offset_t)vms->vm_daddr + > lim_max(td->td_proc, RLIMIT_DATA)); > + if (mmap_random) { > + addr+=arc4random()&(256*1024*1024-1); > + } > + } > PROC_UNLOCK(td->td_proc); > } > if (flags & MAP_ANON) { > >>Release-Note: >>Audit-Trail: >>Unformatted: > _______________________________________________ > freebsd-bugs@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-bugs > To unsubscribe, send any mail to "freebsd-bugs-unsubscribe@freebsd.org" >
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