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Prevent Make from talking to public Internet

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This change introduces the nointernet() function which may be called to
prevent a process and its descendants from communicating with publicly
routable Internet addresses. GNU Make has been modified to always call
this function. In the future Landlock Make will have a way to whitelist
subnets to override this behavior, or disable it entirely. Support is
available for Linux only. Our firewall does not require root access.

Calling nointernet() will return control to the caller inside a new
process that has a SECCOMP BPF filter installed, which traps network
related system calls. Your original process then becomes a permanent
ptrace() supervisor that monitors all processes and threads descending
from the returned child. Whenever a networking system call happens the
kernel will stop the process and wakes up the monitor, which then peeks
into the child memory to read the sockaddr_in to determine if it's ok.

The downside to doing this is that there can be only one supervisor at a
time using ptrace() on a process. So this firewall won't be enabled if
you run make under strace or inside gdb. It also makes testing tricky.
This commit is contained in:
Justine Tunney 2022-08-12 05:17:06 -07:00
parent 8a0a2c0c36
commit 7cf66bc161
48 changed files with 4924 additions and 2046 deletions
Download patch file Download diff file Expand all files Collapse all files

0
test/libc/calls/ptrace_test.c Normal file
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0
test/libc/calls/sys_ptrace_test.c Normal file
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85
test/libc/sock/nointernet_test.c Normal file
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@ -0,0 +1,85 @@
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2022 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/calls.h"
#include "libc/calls/struct/stat.h"
#include "libc/calls/syscall_support-sysv.internal.h"
#include "libc/dce.h"
#include "libc/errno.h"
#include "libc/log/log.h"
#include "libc/runtime/runtime.h"
#include "libc/sock/sock.h"
#include "libc/sock/struct/msghdr.h"
#include "libc/sock/struct/sockaddr.h"
#include "libc/sysv/consts/af.h"
#include "libc/sysv/consts/ipproto.h"
#include "libc/sysv/consts/o.h"
#include "libc/sysv/consts/sock.h"
#include "libc/testlib/testlib.h"
char testlib_enable_tmp_setup_teardown;
void SetUpOnce(void) {
if (nointernet() == -1) {
ASSERT_TRUE(errno == EPERM || // already traced
errno == ENOSYS); // non-linux or ancient linux
if (errno == ENOSYS) {
exit(0);
}
}
}
TEST(nointernet, testLocalhost_isAllowed) {
struct sockaddr_in addr = {AF_INET, 0, {htonl(0x7f000001)}};
ASSERT_SYS(0, 3, socket(AF_INET, SOCK_STREAM, IPPROTO_TCP));
ASSERT_SYS(0, 0, bind(3, &addr, sizeof(addr)));
ASSERT_SYS(ECONNREFUSED, -1, connect(3, &addr, sizeof(addr)));
ASSERT_SYS(0, 0, close(3));
}
TEST(nointernet, testPublicInternet_isDenied) {
struct sockaddr_in addr = {AF_INET, 0, {htonl(0x06060600)}};
ASSERT_SYS(EPERM, -1, socket(AF_BLUETOOTH, SOCK_STREAM, IPPROTO_TCP));
ASSERT_SYS(0, 3, socket(AF_INET, SOCK_STREAM, IPPROTO_TCP));
ASSERT_SYS(ENOSYS, -1, bind(3, &addr, sizeof(addr)));
ASSERT_SYS(ENOSYS, -1, connect(3, &addr, sizeof(addr)));
ASSERT_SYS(0, 0, close(3));
}
TEST(nointernet, sendmsgPrivateNetwork_doesntGetBlocked) {
struct msghdr msg = {
.msg_name = &(struct sockaddr_in){AF_INET, 31337, {htonl(0x0a000001)}},
.msg_namelen = sizeof(struct sockaddr_in),
.msg_iov = &(struct iovec){"hi", 2},
.msg_iovlen = 1,
};
ASSERT_SYS(EBADF, -1, sendmsg(-1, &msg, 0));
}
TEST(nointernet, sendmsgPublicNetwork_raisesEnosys_whichPreemptsEbadf) {
struct msghdr msg = {
.msg_name = &(struct sockaddr_in){AF_INET, 31337, {htonl(0x06060600)}},
.msg_namelen = sizeof(struct sockaddr_in),
.msg_iov = &(struct iovec){"hi", 2},
.msg_iovlen = 1,
};
ASSERT_SYS(ENOSYS, -1, sendmsg(-1, &msg, 0));
ASSERT_SYS(0, 3, socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP));
ASSERT_SYS(ENOSYS, -1, sendmsg(3, &msg, 0));
ASSERT_SYS(0, 0, close(3));
}

3
test/libc/sock/sendrecvmsg_test.c
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@ -19,11 +19,14 @@
#include "libc/assert.h"
#include "libc/calls/struct/iovec.h"
#include "libc/dce.h"
#include "libc/errno.h"
#include "libc/runtime/gc.internal.h"
#include "libc/sock/sock.h"
#include "libc/sock/struct/msghdr.h"
#include "libc/sock/struct/sockaddr.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/af.h"
#include "libc/sysv/consts/ipproto.h"
#include "libc/sysv/consts/o.h"
#include "libc/sysv/consts/sock.h"
#include "libc/testlib/testlib.h"

1
test/libc/sock/test.mk
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@ -34,6 +34,7 @@ TEST_LIBC_SOCK_DIRECTDEPS = \
LIBC_STR \
LIBC_STUBS \
LIBC_SYSV \
LIBC_SYSV_CALLS \
LIBC_TESTLIB \
LIBC_X \
TOOL_DECODE_LIB