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Disable connectat/bindat with AT_FDCWD in capmode

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Previously it was possible to connect a socket (which had the
CAP_CONNECT right) by calling "connectat(AT_FDCWD, ...)" even in
capabilties mode.  This combination should be treated the same as a call
to connect (i.e. forbidden in capabilities mode).  Similarly for bindat.

Disable connectat/bindat with AT_FDCWD in capabilities mode, fix up the
documentation and add tests.

PR:		222632
Submitted by:	Jan Kokemüller <jan.kokemueller@gmail.com>
Reviewed by:	Domagoj Stolfa
MFC after:	1 week
Relnotes:	Yes
Differential Revision:	https://reviews.freebsd.org/D15221
This commit is contained in:
emaste 2018-04-30 17:31:06 +00:00
parent d4300ecd5d
commit e8c6b9b238
4 changed files with 266 additions and 6 deletions
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26
share/man/man4/rights.4
View File

@ -32,7 +32,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd August 17, 2016
.Dd April 30, 2018
.Dt RIGHTS 4
.Os
.Sh NAME
@ -94,8 +94,15 @@ Permit
and
.Xr acl_set_fd_np 3 .
.It Dv CAP_BIND
Permit
.Xr bind 2 .
When not in capabilities mode, permit
.Xr bind 2
and
.Xr bindat 2
with special value
.Dv AT_FDCWD
in the
.Fa fd
parameter.
Note that sockets can also become bound implicitly as a result of
.Xr connect 2
or
@ -116,9 +123,16 @@ An alias to
and
.Dv CAP_LOOKUP .
.It Dv CAP_CONNECT
Permit
.Xr connect 2 ;
also required for
When not in capabilities mode, permit
.Xr connect 2
and
.Xr connectat 2
with special value
.Dv AT_FDCWD
in the
.Fa fd
parameter.
This right is also required for
.Xr sendto 2
with a non-NULL destination address.
.It Dv CAP_CONNECTAT

10
sys/kern/uipc_syscalls.c
View File

@ -187,6 +187,11 @@ kern_bindat(struct thread *td, int dirfd, int fd, struct sockaddr *sa)
cap_rights_t rights;
int error;
#ifdef CAPABILITY_MODE
if (IN_CAPABILITY_MODE(td) && (dirfd == AT_FDCWD))
return (ECAPMODE);
#endif
AUDIT_ARG_FD(fd);
AUDIT_ARG_SOCKADDR(td, dirfd, sa);
error = getsock_cap(td, fd, cap_rights_init(&rights, CAP_BIND),
@ -483,6 +488,11 @@ kern_connectat(struct thread *td, int dirfd, int fd, struct sockaddr *sa)
cap_rights_t rights;
int error, interrupted = 0;
#ifdef CAPABILITY_MODE
if (IN_CAPABILITY_MODE(td) && (dirfd == AT_FDCWD))
return (ECAPMODE);
#endif
AUDIT_ARG_FD(fd);
AUDIT_ARG_SOCKADDR(td, dirfd, sa);
error = getsock_cap(td, fd, cap_rights_init(&rights, CAP_CONNECT),

3
tests/sys/capsicum/Makefile
View File

@ -2,8 +2,11 @@
TESTSDIR= ${TESTSBASE}/sys/capsicum
ATF_TESTS_C+= bindat_connectat
ATF_TESTS_C+= ioctls_test
CFLAGS.bindat_connectat.c+= -I${SRCTOP}/tests
WARNS?= 6
.include <bsd.test.mk>

233
tests/sys/capsicum/bindat_connectat.c Normal file
View File

@ -0,0 +1,233 @@
/*
* Copyright (c) 2017 Jan Kokemüller
*
* 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/capsicum.h>
#include <sys/socket.h>
#include <sys/sysctl.h>
#include <sys/stat.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <atf-c.h>
#include <dlfcn.h>
#include <errno.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include "freebsd_test_suite/macros.h"
static int rootfd = -1;
/* circumvent bug 215690 */
int
open(const char *path, int flags, ...)
{
mode_t mode = 0;
if (flags & O_CREAT) {
va_list ap;
va_start(ap, flags);
mode = (mode_t) va_arg(ap, int);
va_end(ap);
}
if (path && path[0] == '/' && rootfd >= 0) {
return (openat(rootfd, path + 1, flags, mode));
} else {
return (openat(AT_FDCWD, path, flags, mode));
}
}
static void
check_capsicum(void)
{
ATF_REQUIRE_FEATURE("security_capabilities");
ATF_REQUIRE_FEATURE("security_capability_mode");
ATF_REQUIRE((rootfd = open("/", O_EXEC | O_CLOEXEC)) >= 0);
}
typedef int (*socket_fun)(int, const struct sockaddr *, socklen_t);
static int
connectat_fdcwd(int s, const struct sockaddr *name, socklen_t namelen)
{
return (connectat(AT_FDCWD, s, name, namelen));
}
static int
bindat_fdcwd(int s, const struct sockaddr *name, socklen_t namelen)
{
return (bindat(AT_FDCWD, s, name, namelen));
}
ATF_TC(bindat_connectat_1);
ATF_TC_HEAD(bindat_connectat_1, tc)
{
atf_tc_set_md_var(tc, "descr",
"Verify that connect/bind work in normal case");
}
static void
check_1(socket_fun f, int s, const struct sockaddr_in *name)
{
ATF_REQUIRE((s = socket(AF_INET, SOCK_STREAM, 0)) >= 0);
ATF_REQUIRE_ERRNO(EAFNOSUPPORT,
f(s, (const struct sockaddr *)(name),
sizeof(struct sockaddr_in)) < 0);
}
ATF_TC_BODY(bindat_connectat_1, tc)
{
struct sockaddr_in sin;
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_port = htons(0);
sin.sin_addr.s_addr = htonl(0xE0000000);
check_1(bindat_fdcwd, 0, &sin);
check_1(bind, 0, &sin);
check_1(connectat_fdcwd, 0, &sin);
check_1(connect, 0, &sin);
}
ATF_TC(bindat_connectat_2);
ATF_TC_HEAD(bindat_connectat_2, tc)
{
atf_tc_set_md_var(tc, "descr",
"Verify that connect/bind are disabled in cap-mode");
}
static void
check_2(socket_fun f, int s, const struct sockaddr_in *name)
{
ATF_REQUIRE_ERRNO(ECAPMODE,
f(s, (const struct sockaddr *)name,
sizeof(struct sockaddr_in)) < 0);
}
ATF_TC_BODY(bindat_connectat_2, tc)
{
int sock;
struct sockaddr_in sin;
check_capsicum();
ATF_REQUIRE(cap_enter() >= 0);
/* note: sock is created _after_ cap_enter() and contains all rights */
ATF_REQUIRE((sock = socket(AF_INET, SOCK_STREAM, 0)) >= 0);
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
/* dummy port and multicast address (224.0.0.0) to distinguish two
* cases:
* - ECAPMODE/ENOTCAPABLE --> call blocked by capsicum
* - EAFNOSUPPORT --> call went through to protocol layer
*/
sin.sin_port = htons(0);
sin.sin_addr.s_addr = htonl(0xE0000000);
check_2(bindat_fdcwd, sock, &sin);
check_2(bind, sock, &sin);
check_2(connectat_fdcwd, sock, &sin);
check_2(connect, sock, &sin);
}
ATF_TC(bindat_connectat_3);
ATF_TC_HEAD(bindat_connectat_3, tc)
{
atf_tc_set_md_var(tc, "descr",
"Check that taking away CAP_BIND/CAP_CONNECT "
"sabotages bind/connect");
}
static void
check_3(socket_fun f, int s, const struct sockaddr_in *name,
cap_rights_t *rights, cap_rights_t *sub_rights)
{
ATF_REQUIRE((s = socket(AF_INET, SOCK_STREAM, 0)) >= 0);
ATF_REQUIRE(cap_rights_limit(s, rights) >= 0);
ATF_REQUIRE_ERRNO(EAFNOSUPPORT,
f(s, (const struct sockaddr *)name,
sizeof(struct sockaddr_in)) < 0);
ATF_REQUIRE(cap_rights_limit(s,
cap_rights_remove(rights, sub_rights)) >= 0);
ATF_REQUIRE_ERRNO(ENOTCAPABLE,
f(s, (const struct sockaddr *)name,
sizeof(struct sockaddr_in)) < 0);
}
ATF_TC_BODY(bindat_connectat_3, tc)
{
struct sockaddr_in sin;
cap_rights_t rights, sub_rights;
check_capsicum();
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_port = htons(0);
sin.sin_addr.s_addr = htonl(0xE0000000);
check_3(bindat_fdcwd, 0, &sin,
cap_rights_init(&rights, CAP_SOCK_SERVER),
cap_rights_init(&sub_rights, CAP_BIND));
check_3(bind, 0, &sin,
cap_rights_init(&rights, CAP_SOCK_SERVER),
cap_rights_init(&sub_rights, CAP_BIND));
check_3(connectat_fdcwd, 0, &sin,
cap_rights_init(&rights, CAP_SOCK_CLIENT),
cap_rights_init(&sub_rights, CAP_CONNECT));
check_3(connect, 0, &sin,
cap_rights_init(&rights, CAP_SOCK_CLIENT),
cap_rights_init(&sub_rights, CAP_CONNECT));
}
ATF_TP_ADD_TCS(tp)
{
ATF_TP_ADD_TC(tp, bindat_connectat_1);
ATF_TP_ADD_TC(tp, bindat_connectat_2);
ATF_TP_ADD_TC(tp, bindat_connectat_3);
return (atf_no_error());
}