freebsd-dev/sys/kern/imgact_binmisc.c
Ed Maste 26af611582 tighten buffer bounds in imgact_binmisc_populate_interp
We must ensure there's space for the terminating null in the temporary
buffer in imgact_binmisc_populate_interp().

Note that there's no buffer overflow here because xbe->xbe_interpreter's
length and null termination is checked in imgact_binmisc_add_entry()
before imgact_binmisc_populate_interp() is called. However, the latter
should correctly enforce its own bounds.

Reviewed by:	sbruno
MFC after:	1 week
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D10042
2017-03-21 18:02:14 +00:00

758 lines
18 KiB
C

/*-
* Copyright (c) 2013-16, Stacey D. Son
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/ctype.h>
#include <sys/sbuf.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/exec.h>
#include <sys/imgact.h>
#include <sys/imgact_binmisc.h>
#include <sys/kernel.h>
#include <sys/libkern.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/sysctl.h>
#include <sys/sx.h>
#include <machine/atomic.h>
/**
* Miscellaneous binary interpreter image activator.
*
* If the given target executable's header matches 'xbe_magic' field in the
* 'interpreter_list' then it will use the user-level interpreter specified in
* the 'xbe_interpreter' field to execute the binary. The 'xbe_magic' field may
* be adjusted to a given offset using the value in the 'xbe_moffset' field
* and bits of the header may be masked using the 'xbe_mask' field. The
* 'interpreter_list' entries are managed using sysctl(3) as described in the
* <sys/imgact_binmisc.h> file.
*/
/*
* Node of the interpreter list.
*/
typedef struct imgact_binmisc_entry {
char *ibe_name;
uint8_t *ibe_magic;
uint32_t ibe_moffset;
uint32_t ibe_msize;
uint8_t *ibe_mask;
uint8_t *ibe_interpreter;
uint32_t ibe_interp_argcnt;
uint32_t ibe_interp_length;
uint32_t ibe_flags;
SLIST_ENTRY(imgact_binmisc_entry) link;
} imgact_binmisc_entry_t;
/*
* sysctl() commands.
*/
#define IBC_ADD 1 /* Add given entry. */
#define IBC_REMOVE 2 /* Remove entry for a given name. */
#define IBC_DISABLE 3 /* Disable entry for a given name. */
#define IBC_ENABLE 4 /* Enable entry for a given name. */
#define IBC_LOOKUP 5 /* Lookup and return entry for given name. */
#define IBC_LIST 6 /* Get a snapshot of the interpretor list. */
/*
* Interpreter string macros.
*
* They all start with '#' followed by a single letter:
*/
#define ISM_POUND '#' /* "##" is the escape sequence for single #. */
#define ISM_OLD_ARGV0 'a' /* "#a" is replaced with the old argv0. */
MALLOC_DEFINE(M_BINMISC, KMOD_NAME, "misc binary image activator");
/* The interpreter list. */
static SLIST_HEAD(, imgact_binmisc_entry) interpreter_list =
SLIST_HEAD_INITIALIZER(interpreter_list);
static int interp_list_entry_count = 0;
static struct sx interp_list_sx;
/*
* Populate the entry with the information about the interpreter.
*/
static void
imgact_binmisc_populate_interp(char *str, imgact_binmisc_entry_t *ibe)
{
uint32_t len = 0, argc = 1;
char t[IBE_INTERP_LEN_MAX];
char *sp, *tp;
memset(t, 0, sizeof(t));
/*
* Normalize interpreter string. Replace white space between args with
* single space.
*/
sp = str; tp = t;
while (*sp != '\0') {
if (*sp == ' ' || *sp == '\t') {
if (++len >= IBE_INTERP_LEN_MAX)
break;
*tp++ = ' ';
argc++;
while (*sp == ' ' || *sp == '\t')
sp++;
continue;
} else {
*tp++ = *sp++;
len++;
}
}
*tp = '\0';
len++;
ibe->ibe_interpreter = malloc(len, M_BINMISC, M_WAITOK|M_ZERO);
/* Populate all the ibe fields for the interpreter. */
memcpy(ibe->ibe_interpreter, t, len);
ibe->ibe_interp_argcnt = argc;
ibe->ibe_interp_length = len;
}
/*
* Allocate memory and populate a new entry for the interpreter table.
*/
static imgact_binmisc_entry_t *
imgact_binmisc_new_entry(ximgact_binmisc_entry_t *xbe)
{
imgact_binmisc_entry_t *ibe = NULL;
size_t namesz = min(strlen(xbe->xbe_name) + 1, IBE_NAME_MAX);
ibe = malloc(sizeof(*ibe), M_BINMISC, M_WAITOK|M_ZERO);
ibe->ibe_name = malloc(namesz, M_BINMISC, M_WAITOK|M_ZERO);
strlcpy(ibe->ibe_name, xbe->xbe_name, namesz);
imgact_binmisc_populate_interp(xbe->xbe_interpreter, ibe);
ibe->ibe_magic = malloc(xbe->xbe_msize, M_BINMISC, M_WAITOK|M_ZERO);
memcpy(ibe->ibe_magic, xbe->xbe_magic, xbe->xbe_msize);
ibe->ibe_mask = malloc(xbe->xbe_msize, M_BINMISC, M_WAITOK|M_ZERO);
memcpy(ibe->ibe_mask, xbe->xbe_mask, xbe->xbe_msize);
ibe->ibe_moffset = xbe->xbe_moffset;
ibe->ibe_msize = xbe->xbe_msize;
ibe->ibe_flags = xbe->xbe_flags;
return (ibe);
}
/*
* Free the allocated memory for a given list item.
*/
static void
imgact_binmisc_destroy_entry(imgact_binmisc_entry_t *ibe)
{
if (!ibe)
return;
if (ibe->ibe_magic)
free(ibe->ibe_magic, M_BINMISC);
if (ibe->ibe_mask)
free(ibe->ibe_mask, M_BINMISC);
if (ibe->ibe_interpreter)
free(ibe->ibe_interpreter, M_BINMISC);
if (ibe->ibe_name)
free(ibe->ibe_name, M_BINMISC);
if (ibe)
free(ibe, M_BINMISC);
}
/*
* Find the interpreter in the list by the given name. Return NULL if not
* found.
*/
static imgact_binmisc_entry_t *
imgact_binmisc_find_entry(char *name)
{
imgact_binmisc_entry_t *ibe;
sx_assert(&interp_list_sx, SA_LOCKED);
SLIST_FOREACH(ibe, &interpreter_list, link) {
if (strncmp(name, ibe->ibe_name, IBE_NAME_MAX) == 0)
return (ibe);
}
return (NULL);
}
/*
* Add the given interpreter if it doesn't already exist. Return EEXIST
* if the name already exist in the interpreter list.
*/
static int
imgact_binmisc_add_entry(ximgact_binmisc_entry_t *xbe)
{
imgact_binmisc_entry_t *ibe;
char *p;
int cnt;
if (xbe->xbe_msize > IBE_MAGIC_MAX)
return (EINVAL);
for(cnt = 0, p = xbe->xbe_name; *p != 0; cnt++, p++)
if (cnt >= IBE_NAME_MAX || !isascii((int)*p))
return (EINVAL);
for(cnt = 0, p = xbe->xbe_interpreter; *p != 0; cnt++, p++)
if (cnt >= IBE_INTERP_LEN_MAX || !isascii((int)*p))
return (EINVAL);
/* Make sure we don't have any invalid #'s. */
p = xbe->xbe_interpreter;
while (1) {
p = strchr(p, '#');
if (!p)
break;
p++;
switch(*p) {
case ISM_POUND:
/* "##" */
p++;
break;
case ISM_OLD_ARGV0:
/* "#a" */
p++;
break;
case 0:
default:
/* Anything besides the above is invalid. */
return (EINVAL);
}
}
sx_xlock(&interp_list_sx);
if (imgact_binmisc_find_entry(xbe->xbe_name) != NULL) {
sx_xunlock(&interp_list_sx);
return (EEXIST);
}
/* Preallocate a new entry. */
ibe = imgact_binmisc_new_entry(xbe);
SLIST_INSERT_HEAD(&interpreter_list, ibe, link);
interp_list_entry_count++;
sx_xunlock(&interp_list_sx);
return (0);
}
/*
* Remove the interpreter in the list with the given name. Return ENOENT
* if not found.
*/
static int
imgact_binmisc_remove_entry(char *name)
{
imgact_binmisc_entry_t *ibe;
sx_xlock(&interp_list_sx);
if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
sx_xunlock(&interp_list_sx);
return (ENOENT);
}
SLIST_REMOVE(&interpreter_list, ibe, imgact_binmisc_entry, link);
interp_list_entry_count--;
sx_xunlock(&interp_list_sx);
imgact_binmisc_destroy_entry(ibe);
return (0);
}
/*
* Disable the interpreter in the list with the given name. Return ENOENT
* if not found.
*/
static int
imgact_binmisc_disable_entry(char *name)
{
imgact_binmisc_entry_t *ibe;
sx_xlock(&interp_list_sx);
if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
sx_xunlock(&interp_list_sx);
return (ENOENT);
}
ibe->ibe_flags &= ~IBF_ENABLED;
sx_xunlock(&interp_list_sx);
return (0);
}
/*
* Enable the interpreter in the list with the given name. Return ENOENT
* if not found.
*/
static int
imgact_binmisc_enable_entry(char *name)
{
imgact_binmisc_entry_t *ibe;
sx_xlock(&interp_list_sx);
if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
sx_xunlock(&interp_list_sx);
return (ENOENT);
}
ibe->ibe_flags |= IBF_ENABLED;
sx_xunlock(&interp_list_sx);
return (0);
}
static int
imgact_binmisc_populate_xbe(ximgact_binmisc_entry_t *xbe,
imgact_binmisc_entry_t *ibe)
{
uint32_t i;
sx_assert(&interp_list_sx, SA_LOCKED);
memset(xbe, 0, sizeof(*xbe));
strlcpy(xbe->xbe_name, ibe->ibe_name, IBE_NAME_MAX);
/* Copy interpreter string. Replace NULL breaks with space. */
memcpy(xbe->xbe_interpreter, ibe->ibe_interpreter,
ibe->ibe_interp_length);
for(i = 0; i < (ibe->ibe_interp_length - 1); i++)
if (xbe->xbe_interpreter[i] == '\0')
xbe->xbe_interpreter[i] = ' ';
memcpy(xbe->xbe_magic, ibe->ibe_magic, ibe->ibe_msize);
memcpy(xbe->xbe_mask, ibe->ibe_mask, ibe->ibe_msize);
xbe->xbe_version = IBE_VERSION;
xbe->xbe_flags = ibe->ibe_flags;
xbe->xbe_moffset = ibe->ibe_moffset;
xbe->xbe_msize = ibe->ibe_msize;
return (0);
}
/*
* Retrieve the interpreter with the give name and populate the
* ximgact_binmisc_entry structure. Return ENOENT if not found.
*/
static int
imgact_binmisc_lookup_entry(char *name, ximgact_binmisc_entry_t *xbe)
{
imgact_binmisc_entry_t *ibe;
int error = 0;
sx_slock(&interp_list_sx);
if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
sx_sunlock(&interp_list_sx);
return (ENOENT);
}
error = imgact_binmisc_populate_xbe(xbe, ibe);
sx_sunlock(&interp_list_sx);
return (error);
}
/*
* Get a snapshot of all the interpreter entries in the list.
*/
static int
imgact_binmisc_get_all_entries(struct sysctl_req *req)
{
ximgact_binmisc_entry_t *xbe, *xbep;
imgact_binmisc_entry_t *ibe;
int error = 0, count;
sx_slock(&interp_list_sx);
count = interp_list_entry_count;
xbe = malloc(sizeof(*xbe) * count, M_BINMISC, M_WAITOK|M_ZERO);
xbep = xbe;
SLIST_FOREACH(ibe, &interpreter_list, link) {
error = imgact_binmisc_populate_xbe(xbep++, ibe);
if (error)
break;
}
sx_sunlock(&interp_list_sx);
if (!error)
error = SYSCTL_OUT(req, xbe, sizeof(*xbe) * count);
free(xbe, M_BINMISC);
return (error);
}
/*
* sysctl() handler for munipulating interpretor table.
* Not MP safe (locked by sysctl).
*/
static int
sysctl_kern_binmisc(SYSCTL_HANDLER_ARGS)
{
ximgact_binmisc_entry_t xbe;
int error = 0;
switch(arg2) {
case IBC_ADD:
/* Add an entry. Limited to IBE_MAX_ENTRIES. */
error = SYSCTL_IN(req, &xbe, sizeof(xbe));
if (error)
return (error);
if (IBE_VERSION != xbe.xbe_version)
return (EINVAL);
if (interp_list_entry_count == IBE_MAX_ENTRIES)
return (ENOSPC);
error = imgact_binmisc_add_entry(&xbe);
break;
case IBC_REMOVE:
/* Remove an entry. */
error = SYSCTL_IN(req, &xbe, sizeof(xbe));
if (error)
return (error);
if (IBE_VERSION != xbe.xbe_version)
return (EINVAL);
error = imgact_binmisc_remove_entry(xbe.xbe_name);
break;
case IBC_DISABLE:
/* Disable an entry. */
error = SYSCTL_IN(req, &xbe, sizeof(xbe));
if (error)
return (error);
if (IBE_VERSION != xbe.xbe_version)
return (EINVAL);
error = imgact_binmisc_disable_entry(xbe.xbe_name);
break;
case IBC_ENABLE:
/* Enable an entry. */
error = SYSCTL_IN(req, &xbe, sizeof(xbe));
if (error)
return (error);
if (IBE_VERSION != xbe.xbe_version)
return (EINVAL);
error = imgact_binmisc_enable_entry(xbe.xbe_name);
break;
case IBC_LOOKUP:
/* Lookup an entry. */
error = SYSCTL_IN(req, &xbe, sizeof(xbe));
if (error)
return (error);
if (IBE_VERSION != xbe.xbe_version)
return (EINVAL);
error = imgact_binmisc_lookup_entry(xbe.xbe_name, &xbe);
if (!error)
error = SYSCTL_OUT(req, &xbe, sizeof(xbe));
break;
case IBC_LIST:
/* Return a snapshot of the interpretor list. */
if (!req->oldptr) {
/* No pointer then just return the list size. */
error = SYSCTL_OUT(req, 0, interp_list_entry_count *
sizeof(ximgact_binmisc_entry_t));
return (error);
} else
if (!req->oldlen)
return (EINVAL);
error = imgact_binmisc_get_all_entries(req);
break;
default:
return (EINVAL);
}
return (error);
}
SYSCTL_NODE(_kern, OID_AUTO, binmisc, CTLFLAG_RW, 0,
"Image activator for miscellaneous binaries");
SYSCTL_PROC(_kern_binmisc, OID_AUTO, add,
CTLFLAG_MPSAFE|CTLTYPE_STRUCT|CTLFLAG_WR, NULL, IBC_ADD,
sysctl_kern_binmisc, "S,ximgact_binmisc_entry",
"Add an activator entry");
SYSCTL_PROC(_kern_binmisc, OID_AUTO, remove,
CTLFLAG_MPSAFE|CTLTYPE_STRUCT|CTLFLAG_WR, NULL, IBC_REMOVE,
sysctl_kern_binmisc, "S,ximgact_binmisc_entry",
"Remove an activator entry");
SYSCTL_PROC(_kern_binmisc, OID_AUTO, disable,
CTLFLAG_MPSAFE|CTLTYPE_STRUCT|CTLFLAG_WR, NULL, IBC_DISABLE,
sysctl_kern_binmisc, "S,ximgact_binmisc_entry",
"Disable an activator entry");
SYSCTL_PROC(_kern_binmisc, OID_AUTO, enable,
CTLFLAG_MPSAFE|CTLTYPE_STRUCT|CTLFLAG_WR, NULL, IBC_ENABLE,
sysctl_kern_binmisc, "S,ximgact_binmisc_entry",
"Enable an activator entry");
SYSCTL_PROC(_kern_binmisc, OID_AUTO, lookup,
CTLFLAG_MPSAFE|CTLTYPE_STRUCT|CTLFLAG_RW|CTLFLAG_ANYBODY, NULL, IBC_LOOKUP,
sysctl_kern_binmisc, "S,ximgact_binmisc_entry",
"Lookup an activator entry");
SYSCTL_PROC(_kern_binmisc, OID_AUTO, list,
CTLFLAG_MPSAFE|CTLTYPE_STRUCT|CTLFLAG_RD|CTLFLAG_ANYBODY, NULL, IBC_LIST,
sysctl_kern_binmisc, "S,ximgact_binmisc_entry",
"Get snapshot of all the activator entries");
static imgact_binmisc_entry_t *
imgact_binmisc_find_interpreter(const char *image_header)
{
imgact_binmisc_entry_t *ibe;
const char *p;
int i;
size_t sz;
sx_assert(&interp_list_sx, SA_LOCKED);
SLIST_FOREACH(ibe, &interpreter_list, link) {
if (!(IBF_ENABLED & ibe->ibe_flags))
continue;
p = image_header + ibe->ibe_moffset;
sz = ibe->ibe_msize;
if (IBF_USE_MASK & ibe->ibe_flags) {
/* Compare using mask. */
for (i = 0; i < sz; i++)
if ((*p++ ^ ibe->ibe_magic[i]) &
ibe->ibe_mask[i])
break;
} else {
for (i = 0; i < sz; i++)
if (*p++ ^ ibe->ibe_magic[i])
break;
}
if (i == ibe->ibe_msize)
return (ibe);
}
return (NULL);
}
static int
imgact_binmisc_exec(struct image_params *imgp)
{
const char *image_header = imgp->image_header;
const char *fname = NULL;
int error = 0;
size_t offset, l;
imgact_binmisc_entry_t *ibe;
struct sbuf *sname;
char *s, *d;
/* Do we have an interpreter for the given image header? */
sx_slock(&interp_list_sx);
if ((ibe = imgact_binmisc_find_interpreter(image_header)) == NULL) {
sx_sunlock(&interp_list_sx);
return (-1);
}
/* No interpreter nesting allowed. */
if (imgp->interpreted & IMGACT_BINMISC) {
sx_sunlock(&interp_list_sx);
return (ENOEXEC);
}
imgp->interpreted |= IMGACT_BINMISC;
if (imgp->args->fname != NULL) {
fname = imgp->args->fname;
sname = NULL;
} else {
/* Use the fdescfs(5) path for fexecve(2). */
sname = sbuf_new_auto();
sbuf_printf(sname, "/dev/fd/%d", imgp->args->fd);
sbuf_finish(sname);
fname = sbuf_data(sname);
}
/*
* We need to "push" the interpreter in the arg[] list. To do this,
* we first shift all the other values in the `begin_argv' area to
* provide the exact amount of room for the values added. Set up
* `offset' as the number of bytes to be added to the `begin_argv'
* area.
*/
offset = ibe->ibe_interp_length;
/* Adjust the offset for #'s. */
s = ibe->ibe_interpreter;
while (1) {
s = strchr(s, '#');
if (!s)
break;
s++;
switch(*s) {
case ISM_POUND:
/* "##" -> "#": reduce offset by one. */
offset--;
break;
case ISM_OLD_ARGV0:
/* "#a" -> (old argv0): increase offset to fit fname */
offset += strlen(fname) - 2;
break;
default:
/* Hmm... This shouldn't happen. */
sx_sunlock(&interp_list_sx);
printf("%s: Unknown macro #%c sequence in "
"interpreter string\n", KMOD_NAME, *(s + 1));
error = EINVAL;
goto done;
}
s++;
}
/* Check to make sure we won't overrun the stringspace. */
if (offset > imgp->args->stringspace) {
sx_sunlock(&interp_list_sx);
error = E2BIG;
goto done;
}
/* Make room for the interpreter */
bcopy(imgp->args->begin_argv, imgp->args->begin_argv + offset,
imgp->args->endp - imgp->args->begin_argv);
/* Adjust everything by the offset. */
imgp->args->begin_envv += offset;
imgp->args->endp += offset;
imgp->args->stringspace -= offset;
/* Add the new argument(s) in the count. */
imgp->args->argc += ibe->ibe_interp_argcnt;
/*
* The original arg[] list has been shifted appropriately. Copy in
* the interpreter path.
*/
s = ibe->ibe_interpreter;
d = imgp->args->begin_argv;
while(*s != '\0') {
switch (*s) {
case '#':
/* Handle "#" in interpreter string. */
s++;
switch(*s) {
case ISM_POUND:
/* "##": Replace with a single '#' */
*d++ = '#';
break;
case ISM_OLD_ARGV0:
/* "#a": Replace with old arg0 (fname). */
if ((l = strlen(fname)) != 0) {
memcpy(d, fname, l);
d += l;
}
break;
default:
/* Shouldn't happen but skip it if it does. */
break;
}
break;
case ' ':
/* Replace space with NUL to separate arguments. */
*d++ = '\0';
break;
default:
*d++ = *s;
break;
}
s++;
}
*d = '\0';
sx_sunlock(&interp_list_sx);
if (!error)
imgp->interpreter_name = imgp->args->begin_argv;
done:
if (sname)
sbuf_delete(sname);
return (error);
}
static void
imgact_binmisc_init(void *arg)
{
sx_init(&interp_list_sx, KMOD_NAME);
}
static void
imgact_binmisc_fini(void *arg)
{
imgact_binmisc_entry_t *ibe, *ibe_tmp;
/* Free all the interpreters. */
sx_xlock(&interp_list_sx);
SLIST_FOREACH_SAFE(ibe, &interpreter_list, link, ibe_tmp) {
SLIST_REMOVE(&interpreter_list, ibe, imgact_binmisc_entry,
link);
imgact_binmisc_destroy_entry(ibe);
}
sx_xunlock(&interp_list_sx);
sx_destroy(&interp_list_sx);
}
SYSINIT(imgact_binmisc, SI_SUB_EXEC, SI_ORDER_MIDDLE, imgact_binmisc_init, 0);
SYSUNINIT(imgact_binmisc, SI_SUB_EXEC, SI_ORDER_MIDDLE, imgact_binmisc_fini, 0);
/*
* Tell kern_execve.c about it, with a little help from the linker.
*/
static struct execsw imgact_binmisc_execsw = { imgact_binmisc_exec, KMOD_NAME };
EXEC_SET(imgact_binmisc, imgact_binmisc_execsw);