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Fix pledge() thread killing semantics

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- tkill(tid, sig) should be allowed by stdio
- tgkill(getpid(), tid, sig) should be allowed by stdio

Fixes #628
This commit is contained in:
Justine Tunney 2022-09-19 15:31:16 -07:00
parent c7a8cd21e9
commit 1ea01fc905
No known key found for this signature in database
GPG key ID: BE714B4575D6E328
2 changed files with 45 additions and 11 deletions
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20
libc/calls/pledge-linux.c
View file

@ -540,7 +540,8 @@ static const uint16_t kPledgeStdio[] = {
__NR_linux_sigsuspend, //
__NR_linux_sigpending, //
__NR_linux_kill | SELF, //
__NR_linux_tkill | SELF, //
__NR_linux_tkill, //
__NR_linux_tgkill | SELF, //
__NR_linux_socketpair, //
__NR_linux_getrusage, //
__NR_linux_times, //
@ -691,6 +692,7 @@ static const uint16_t kPledgeProc[] = {
__NR_linux_vfork, //
__NR_linux_clone | RESTRICT, //
__NR_linux_kill, //
__NR_linux_tgkill, //
__NR_linux_setsid, //
__NR_linux_setpgid, //
__NR_linux_prlimit, //
@ -707,8 +709,6 @@ static const uint16_t kPledgeProc[] = {
__NR_linux_sched_setaffinity, //
__NR_linux_sched_getparam, //
__NR_linux_sched_setparam, //
__NR_linux_tkill, //
__NR_linux_tgkill, //
};
static const uint16_t kPledgeId[] = {
@ -1028,15 +1028,15 @@ static privileged void AllowKillSelf(struct Filter *f) {
AppendFilter(f, PLEDGE(fragment));
}
// The first argument of tkill() must be
// The first argument of tgkill() must be
//
// - gettid()
// - getpid()
//
static privileged void AllowTkillSelf(struct Filter *f) {
static privileged void AllowTgkillSelf(struct Filter *f) {
struct sock_filter fragment[] = {
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_linux_tkill, 0, 4),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_linux_tgkill, 0, 4),
BPF_STMT(BPF_LD | BPF_W | BPF_ABS, OFF(args[0])),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, GetTid(), 0, 1),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, GetPid(), 0, 1),
BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW),
BPF_STMT(BPF_LD | BPF_W | BPF_ABS, OFF(nr)),
};
@ -1949,8 +1949,8 @@ static privileged void AppendPledge(struct Filter *f, //
case __NR_linux_kill | SELF:
AllowKillSelf(f);
break;
case __NR_linux_tkill | SELF:
AllowTkillSelf(f);
case __NR_linux_tgkill | SELF:
AllowTgkillSelf(f);
break;
default:
notpossible;

36
test/libc/calls/pledge_test.c
View file

@ -17,7 +17,6 @@
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/calls.h"
#include "libc/mem/copyfd.internal.h"
#include "libc/calls/internal.h"
#include "libc/calls/ioctl.h"
#include "libc/calls/pledge.internal.h"
@ -26,11 +25,14 @@
#include "libc/calls/struct/flock.h"
#include "libc/calls/struct/seccomp.h"
#include "libc/calls/struct/sigaction.h"
#include "libc/calls/struct/sigset.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/intrin/kprintf.h"
#include "libc/macros.internal.h"
#include "libc/mem/copyfd.internal.h"
#include "libc/mem/mem.h"
#include "libc/runtime/internal.h"
#include "libc/runtime/runtime.h"
@ -53,6 +55,7 @@
#include "libc/sysv/consts/sock.h"
#include "libc/sysv/consts/sol.h"
#include "libc/testlib/ezbench.h"
#include "libc/testlib/subprocess.h"
#include "libc/testlib/testlib.h"
#include "libc/thread/spawn.h"
#include "libc/time/time.h"
@ -143,6 +146,37 @@ TEST(pledge, withThreadMemory) {
EXPECT_EQ(4, job[0]); // check result
}
bool gotusr1;
void OnUsr1(int sig) {
gotusr1 = true;
}
int TgkillWorker(void *arg, int tid) {
sigset_t mask;
signal(SIGUSR1, OnUsr1);
sigemptyset(&mask);
ASSERT_SYS(EINTR, -1, sigsuspend(&mask));
ASSERT_TRUE(gotusr1);
return 0;
}
TEST(pledge, tgkill) {
// https://github.com/jart/cosmopolitan/issues/628
if (!IsLinux()) return;
sigset_t mask;
struct spawn worker;
SPAWN(fork);
sigemptyset(&mask);
sigaddset(&mask, SIGUSR1);
sigprocmask(SIG_BLOCK, &mask, 0);
ASSERT_SYS(0, 0, pledge("stdio", 0));
ASSERT_SYS(0, 0, _spawn(TgkillWorker, 0, &worker));
ASSERT_SYS(0, 0, tgkill(getpid(), worker.ptid, SIGUSR1));
ASSERT_SYS(0, 0, _join(&worker));
EXITS(0);
}
TEST(pledge, stdio_forbidsOpeningPasswd1) {
if (!IsLinux()) return;
int ws, pid;