The following reply was made to PR kern/181497; it has been noted by GNATS.
From: Steven Lee <ste...@roothosts.com> To: Oliver Pinter <oliver.p...@gmail.com>, freebsd-gnats-sub...@freebsd.org Cc: Subject: Re: kern/181497: ASLR Feature Request - patch included Date: Sat, 24 Aug 2013 14:49:03 -0600 Wow... very nice. :) On 13-08-24 07:48 AM, Oliver Pinter wrote: > new version of the patchset: > https://github.com/opntr/freebsd-patches-2013-tavasz/tree/master/r249952+ASLR > > On 8/24/13, Steven Lee <ste...@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.p...@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-unsubscr...@freebsd.org" >> -- Regards, Steven Lee _______________________________________________ freebsd-bugs@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-bugs To unsubscribe, send any mail to "freebsd-bugs-unsubscr...@freebsd.org"
