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-rw-r--r--test/syscalls/BUILD4
-rw-r--r--test/syscalls/linux/BUILD19
-rw-r--r--test/syscalls/linux/pty.cc393
-rw-r--r--test/syscalls/linux/pty_root.cc68
-rw-r--r--test/util/BUILD11
-rw-r--r--test/util/pty_util.cc45
-rw-r--r--test/util/pty_util.h30
7 files changed, 551 insertions, 19 deletions
diff --git a/test/syscalls/BUILD b/test/syscalls/BUILD
index 0135435ea..63e4c63dd 100644
--- a/test/syscalls/BUILD
+++ b/test/syscalls/BUILD
@@ -321,6 +321,10 @@ syscall_test(
)
syscall_test(
+ test = "//test/syscalls/linux:pty_root_test",
+)
+
+syscall_test(
add_overlay = True,
test = "//test/syscalls/linux:pwritev2_test",
)
diff --git a/test/syscalls/linux/BUILD b/test/syscalls/linux/BUILD
index 56fe7be37..a4cebf46f 100644
--- a/test/syscalls/linux/BUILD
+++ b/test/syscalls/linux/BUILD
@@ -1287,8 +1287,10 @@ cc_binary(
srcs = ["pty.cc"],
linkstatic = 1,
deps = [
+ "//test/util:capability_util",
"//test/util:file_descriptor",
"//test/util:posix_error",
+ "//test/util:pty_util",
"//test/util:test_main",
"//test/util:test_util",
"//test/util:thread_util",
@@ -1301,6 +1303,23 @@ cc_binary(
)
cc_binary(
+ name = "pty_root_test",
+ testonly = 1,
+ srcs = ["pty_root.cc"],
+ linkstatic = 1,
+ deps = [
+ "//test/util:capability_util",
+ "//test/util:file_descriptor",
+ "//test/util:posix_error",
+ "//test/util:pty_util",
+ "//test/util:test_main",
+ "//test/util:thread_util",
+ "@com_google_absl//absl/base:core_headers",
+ "@com_google_googletest//:gtest",
+ ],
+)
+
+cc_binary(
name = "partial_bad_buffer_test",
testonly = 1,
srcs = ["partial_bad_buffer.cc"],
diff --git a/test/syscalls/linux/pty.cc b/test/syscalls/linux/pty.cc
index d1ab4703f..286388316 100644
--- a/test/syscalls/linux/pty.cc
+++ b/test/syscalls/linux/pty.cc
@@ -13,13 +13,17 @@
// limitations under the License.
#include <fcntl.h>
+#include <linux/capability.h>
#include <linux/major.h>
#include <poll.h>
+#include <sched.h>
+#include <signal.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <sys/types.h>
+#include <sys/wait.h>
#include <termios.h>
#include <unistd.h>
@@ -31,8 +35,10 @@
#include "absl/synchronization/notification.h"
#include "absl/time/clock.h"
#include "absl/time/time.h"
+#include "test/util/capability_util.h"
#include "test/util/file_descriptor.h"
#include "test/util/posix_error.h"
+#include "test/util/pty_util.h"
#include "test/util/test_util.h"
#include "test/util/thread_util.h"
@@ -370,25 +376,6 @@ PosixErrorOr<size_t> PollAndReadFd(int fd, void* buf, size_t count,
return PosixError(ETIMEDOUT, "Poll timed out");
}
-// Opens the slave end of the passed master as R/W and nonblocking.
-PosixErrorOr<FileDescriptor> OpenSlave(const FileDescriptor& master) {
- // Get pty index.
- int n;
- int ret = ioctl(master.get(), TIOCGPTN, &n);
- if (ret < 0) {
- return PosixError(errno, "ioctl(TIOCGPTN) failed");
- }
-
- // Unlock pts.
- int unlock = 0;
- ret = ioctl(master.get(), TIOCSPTLCK, &unlock);
- if (ret < 0) {
- return PosixError(errno, "ioctl(TIOSPTLCK) failed");
- }
-
- return Open(absl::StrCat("/dev/pts/", n), O_RDWR | O_NONBLOCK);
-}
-
TEST(BasicPtyTest, StatUnopenedMaster) {
struct stat s;
ASSERT_THAT(stat("/dev/ptmx", &s), SyscallSucceeds());
@@ -1233,6 +1220,374 @@ TEST_F(PtyTest, SetMasterWindowSize) {
EXPECT_EQ(retrieved_ws.ws_col, kCols);
}
+class JobControlTest : public ::testing::Test {
+ protected:
+ void SetUp() override {
+ master_ = ASSERT_NO_ERRNO_AND_VALUE(Open("/dev/ptmx", O_RDWR | O_NONBLOCK));
+ slave_ = ASSERT_NO_ERRNO_AND_VALUE(OpenSlave(master_));
+
+ // Make this a session leader, which also drops the controlling terminal.
+ // In the gVisor test environment, this test will be run as the session
+ // leader already (as the sentry init process).
+ if (!IsRunningOnGvisor()) {
+ ASSERT_THAT(setsid(), SyscallSucceeds());
+ }
+ }
+
+ // Master and slave ends of the PTY. Non-blocking.
+ FileDescriptor master_;
+ FileDescriptor slave_;
+};
+
+TEST_F(JobControlTest, SetTTYMaster) {
+ ASSERT_THAT(ioctl(master_.get(), TIOCSCTTY, 0), SyscallSucceeds());
+}
+
+TEST_F(JobControlTest, SetTTY) {
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSCTTY, 0), SyscallSucceeds());
+}
+
+TEST_F(JobControlTest, SetTTYNonLeader) {
+ // Fork a process that won't be the session leader.
+ pid_t child = fork();
+ if (!child) {
+ // We shouldn't be able to set the terminal.
+ TEST_PCHECK(ioctl(slave_.get(), TIOCSCTTY, 0));
+ _exit(0);
+ }
+
+ int wstatus;
+ ASSERT_THAT(waitpid(child, &wstatus, 0), SyscallSucceedsWithValue(child));
+ ASSERT_EQ(wstatus, 0);
+}
+
+TEST_F(JobControlTest, SetTTYBadArg) {
+ // Despite the man page saying arg should be 0 here, Linux doesn't actually
+ // check.
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSCTTY, 1), SyscallSucceeds());
+}
+
+TEST_F(JobControlTest, SetTTYDifferentSession) {
+ SKIP_IF(ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SYS_ADMIN)));
+
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSCTTY, 0), SyscallSucceeds());
+
+ // Fork, join a new session, and try to steal the parent's controlling
+ // terminal, which should fail.
+ pid_t child = fork();
+ if (!child) {
+ TEST_PCHECK(setsid() >= 0);
+ // We shouldn't be able to steal the terminal.
+ TEST_PCHECK(ioctl(slave_.get(), TIOCSCTTY, 1));
+ _exit(0);
+ }
+
+ int wstatus;
+ ASSERT_THAT(waitpid(child, &wstatus, 0), SyscallSucceedsWithValue(child));
+ ASSERT_EQ(wstatus, 0);
+}
+
+TEST_F(JobControlTest, ReleaseTTY) {
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSCTTY, 0), SyscallSucceeds());
+
+ // Make sure we're ignoring SIGHUP, which will be sent to this process once we
+ // disconnect they TTY.
+ struct sigaction sa = {
+ .sa_handler = SIG_IGN,
+ .sa_flags = 0,
+ };
+ sigemptyset(&sa.sa_mask);
+ struct sigaction old_sa;
+ EXPECT_THAT(sigaction(SIGHUP, &sa, &old_sa), SyscallSucceeds());
+ EXPECT_THAT(ioctl(slave_.get(), TIOCNOTTY), SyscallSucceeds());
+ EXPECT_THAT(sigaction(SIGHUP, &old_sa, NULL), SyscallSucceeds());
+}
+
+TEST_F(JobControlTest, ReleaseUnsetTTY) {
+ ASSERT_THAT(ioctl(slave_.get(), TIOCNOTTY), SyscallFailsWithErrno(ENOTTY));
+}
+
+TEST_F(JobControlTest, ReleaseWrongTTY) {
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSCTTY, 0), SyscallSucceeds());
+
+ ASSERT_THAT(ioctl(master_.get(), TIOCNOTTY), SyscallFailsWithErrno(ENOTTY));
+}
+
+TEST_F(JobControlTest, ReleaseTTYNonLeader) {
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSCTTY, 0), SyscallSucceeds());
+
+ pid_t child = fork();
+ if (!child) {
+ TEST_PCHECK(!ioctl(slave_.get(), TIOCNOTTY));
+ _exit(0);
+ }
+
+ int wstatus;
+ ASSERT_THAT(waitpid(child, &wstatus, 0), SyscallSucceedsWithValue(child));
+ ASSERT_EQ(wstatus, 0);
+}
+
+TEST_F(JobControlTest, ReleaseTTYDifferentSession) {
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSCTTY, 0), SyscallSucceeds());
+
+ pid_t child = fork();
+ if (!child) {
+ // Join a new session, then try to disconnect.
+ TEST_PCHECK(setsid() >= 0);
+ TEST_PCHECK(ioctl(slave_.get(), TIOCNOTTY));
+ _exit(0);
+ }
+
+ int wstatus;
+ ASSERT_THAT(waitpid(child, &wstatus, 0), SyscallSucceedsWithValue(child));
+ ASSERT_EQ(wstatus, 0);
+}
+
+// Used by the child process spawned in ReleaseTTYSignals to track received
+// signals.
+static int received;
+
+void sig_handler(int signum) { received |= signum; }
+
+// When the session leader releases its controlling terminal, the foreground
+// process group gets SIGHUP, then SIGCONT. This test:
+// - Spawns 2 threads
+// - Has thread 1 return 0 if it gets both SIGHUP and SIGCONT
+// - Has thread 2 leave the foreground process group, and return non-zero if it
+// receives any signals.
+// - Has the parent thread release its controlling terminal
+// - Checks that thread 1 got both signals
+// - Checks that thread 2 didn't get any signals.
+TEST_F(JobControlTest, ReleaseTTYSignals) {
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSCTTY, 0), SyscallSucceeds());
+
+ received = 0;
+ struct sigaction sa = {
+ .sa_handler = sig_handler,
+ .sa_flags = 0,
+ };
+ sigemptyset(&sa.sa_mask);
+ sigaddset(&sa.sa_mask, SIGHUP);
+ sigaddset(&sa.sa_mask, SIGCONT);
+ sigprocmask(SIG_BLOCK, &sa.sa_mask, NULL);
+
+ pid_t same_pgrp_child = fork();
+ if (!same_pgrp_child) {
+ // The child will wait for SIGHUP and SIGCONT, then return 0. It begins with
+ // SIGHUP and SIGCONT blocked. We install signal handlers for those signals,
+ // then use sigsuspend to wait for those specific signals.
+ TEST_PCHECK(!sigaction(SIGHUP, &sa, NULL));
+ TEST_PCHECK(!sigaction(SIGCONT, &sa, NULL));
+ sigset_t mask;
+ sigfillset(&mask);
+ sigdelset(&mask, SIGHUP);
+ sigdelset(&mask, SIGCONT);
+ while (received != (SIGHUP | SIGCONT)) {
+ sigsuspend(&mask);
+ }
+ _exit(0);
+ }
+
+ // We don't want to block these anymore.
+ sigprocmask(SIG_UNBLOCK, &sa.sa_mask, NULL);
+
+ // This child will return non-zero if either SIGHUP or SIGCONT are received.
+ pid_t diff_pgrp_child = fork();
+ if (!diff_pgrp_child) {
+ TEST_PCHECK(!setpgid(0, 0));
+ TEST_PCHECK(pause());
+ _exit(1);
+ }
+
+ EXPECT_THAT(setpgid(diff_pgrp_child, diff_pgrp_child), SyscallSucceeds());
+
+ // Make sure we're ignoring SIGHUP, which will be sent to this process once we
+ // disconnect they TTY.
+ struct sigaction sighup_sa = {
+ .sa_handler = SIG_IGN,
+ .sa_flags = 0,
+ };
+ sigemptyset(&sighup_sa.sa_mask);
+ struct sigaction old_sa;
+ EXPECT_THAT(sigaction(SIGHUP, &sighup_sa, &old_sa), SyscallSucceeds());
+
+ // Release the controlling terminal, sending SIGHUP and SIGCONT to all other
+ // processes in this process group.
+ EXPECT_THAT(ioctl(slave_.get(), TIOCNOTTY), SyscallSucceeds());
+
+ EXPECT_THAT(sigaction(SIGHUP, &old_sa, NULL), SyscallSucceeds());
+
+ // The child in the same process group will get signaled.
+ int wstatus;
+ EXPECT_THAT(waitpid(same_pgrp_child, &wstatus, 0),
+ SyscallSucceedsWithValue(same_pgrp_child));
+ EXPECT_EQ(wstatus, 0);
+
+ // The other child will not get signaled.
+ EXPECT_THAT(waitpid(diff_pgrp_child, &wstatus, WNOHANG),
+ SyscallSucceedsWithValue(0));
+ EXPECT_THAT(kill(diff_pgrp_child, SIGKILL), SyscallSucceeds());
+}
+
+TEST_F(JobControlTest, GetForegroundProcessGroup) {
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSCTTY, 0), SyscallSucceeds());
+ pid_t foreground_pgid;
+ pid_t pid;
+ ASSERT_THAT(ioctl(slave_.get(), TIOCGPGRP, &foreground_pgid),
+ SyscallSucceeds());
+ ASSERT_THAT(pid = getpid(), SyscallSucceeds());
+
+ ASSERT_EQ(foreground_pgid, pid);
+}
+
+TEST_F(JobControlTest, GetForegroundProcessGroupNonControlling) {
+ // At this point there's no controlling terminal, so TIOCGPGRP should fail.
+ pid_t foreground_pgid;
+ ASSERT_THAT(ioctl(slave_.get(), TIOCGPGRP, &foreground_pgid),
+ SyscallFailsWithErrno(ENOTTY));
+}
+
+// This test:
+// - sets itself as the foreground process group
+// - creates a child process in a new process group
+// - sets that child as the foreground process group
+// - kills its child and sets itself as the foreground process group.
+TEST_F(JobControlTest, SetForegroundProcessGroup) {
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSCTTY, 0), SyscallSucceeds());
+
+ // Ignore SIGTTOU so that we don't stop ourself when calling tcsetpgrp.
+ struct sigaction sa = {
+ .sa_handler = SIG_IGN,
+ .sa_flags = 0,
+ };
+ sigemptyset(&sa.sa_mask);
+ sigaction(SIGTTOU, &sa, NULL);
+
+ // Set ourself as the foreground process group.
+ ASSERT_THAT(tcsetpgrp(slave_.get(), getpgid(0)), SyscallSucceeds());
+
+ // Create a new process that just waits to be signaled.
+ pid_t child = fork();
+ if (!child) {
+ TEST_PCHECK(!pause());
+ // We should never reach this.
+ _exit(1);
+ }
+
+ // Make the child its own process group, then make it the controlling process
+ // group of the terminal.
+ ASSERT_THAT(setpgid(child, child), SyscallSucceeds());
+ ASSERT_THAT(tcsetpgrp(slave_.get(), child), SyscallSucceeds());
+
+ // Sanity check - we're still the controlling session.
+ ASSERT_EQ(getsid(0), getsid(child));
+
+ // Signal the child, wait for it to exit, then retake the terminal.
+ ASSERT_THAT(kill(child, SIGTERM), SyscallSucceeds());
+ int wstatus;
+ ASSERT_THAT(waitpid(child, &wstatus, 0), SyscallSucceedsWithValue(child));
+ ASSERT_TRUE(WIFSIGNALED(wstatus));
+ ASSERT_EQ(WTERMSIG(wstatus), SIGTERM);
+
+ // Set ourself as the foreground process.
+ pid_t pgid;
+ ASSERT_THAT(pgid = getpgid(0), SyscallSucceeds());
+ ASSERT_THAT(tcsetpgrp(slave_.get(), pgid), SyscallSucceeds());
+}
+
+TEST_F(JobControlTest, SetForegroundProcessGroupWrongTTY) {
+ pid_t pid = getpid();
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSPGRP, &pid),
+ SyscallFailsWithErrno(ENOTTY));
+}
+
+TEST_F(JobControlTest, SetForegroundProcessGroupNegPgid) {
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSCTTY, 0), SyscallSucceeds());
+
+ pid_t pid = -1;
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSPGRP, &pid),
+ SyscallFailsWithErrno(EINVAL));
+}
+
+TEST_F(JobControlTest, SetForegroundProcessGroupEmptyProcessGroup) {
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSCTTY, 0), SyscallSucceeds());
+
+ // Create a new process, put it in a new process group, make that group the
+ // foreground process group, then have the process wait.
+ pid_t child = fork();
+ if (!child) {
+ TEST_PCHECK(!setpgid(0, 0));
+ _exit(0);
+ }
+
+ // Wait for the child to exit.
+ int wstatus;
+ EXPECT_THAT(waitpid(child, &wstatus, 0), SyscallSucceedsWithValue(child));
+ // The child's process group doesn't exist anymore - this should fail.
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSPGRP, &child),
+ SyscallFailsWithErrno(ESRCH));
+}
+
+TEST_F(JobControlTest, SetForegroundProcessGroupDifferentSession) {
+ ASSERT_THAT(ioctl(slave_.get(), TIOCSCTTY, 0), SyscallSucceeds());
+
+ // Create a new process and put it in a new session.
+ pid_t child = fork();
+ if (!child) {
+ TEST_PCHECK(setsid() >= 0);
+ // Tell the parent we're in a new session.
+ TEST_PCHECK(!raise(SIGSTOP));
+ TEST_PCHECK(!pause());
+ _exit(1);
+ }
+
+ // Wait for the child to tell us it's in a new session.
+ int wstatus;
+ EXPECT_THAT(waitpid(child, &wstatus, WUNTRACED),
+ SyscallSucceedsWithValue(child));
+ EXPECT_TRUE(WSTOPSIG(wstatus));
+
+ // Child is in a new session, so we can't make it the foregroup process group.
+ EXPECT_THAT(ioctl(slave_.get(), TIOCSPGRP, &child),
+ SyscallFailsWithErrno(EPERM));
+
+ EXPECT_THAT(kill(child, SIGKILL), SyscallSucceeds());
+}
+
+// Verify that we don't hang when creating a new session from an orphaned
+// process group (b/139968068). Calling setsid() creates an orphaned process
+// group, as process groups that contain the session's leading process are
+// orphans.
+//
+// We create 2 sessions in this test. The init process in gVisor is considered
+// not to be an orphan (see sessions.go), so we have to create a session from
+// which to create a session. The latter session is being created from an
+// orphaned process group.
+TEST_F(JobControlTest, OrphanRegression) {
+ pid_t session_2_leader = fork();
+ if (!session_2_leader) {
+ TEST_PCHECK(setsid() >= 0);
+
+ pid_t session_3_leader = fork();
+ if (!session_3_leader) {
+ TEST_PCHECK(setsid() >= 0);
+
+ _exit(0);
+ }
+
+ int wstatus;
+ TEST_PCHECK(waitpid(session_3_leader, &wstatus, 0) == session_3_leader);
+ TEST_PCHECK(wstatus == 0);
+
+ _exit(0);
+ }
+
+ int wstatus;
+ ASSERT_THAT(waitpid(session_2_leader, &wstatus, 0),
+ SyscallSucceedsWithValue(session_2_leader));
+ ASSERT_EQ(wstatus, 0);
+}
+
} // namespace
} // namespace testing
} // namespace gvisor
diff --git a/test/syscalls/linux/pty_root.cc b/test/syscalls/linux/pty_root.cc
new file mode 100644
index 000000000..14a4af980
--- /dev/null
+++ b/test/syscalls/linux/pty_root.cc
@@ -0,0 +1,68 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <sys/ioctl.h>
+#include <termios.h>
+
+#include "gtest/gtest.h"
+#include "absl/base/macros.h"
+#include "test/util/capability_util.h"
+#include "test/util/file_descriptor.h"
+#include "test/util/posix_error.h"
+#include "test/util/pty_util.h"
+
+namespace gvisor {
+namespace testing {
+
+// These tests should be run as root.
+namespace {
+
+TEST(JobControlRootTest, StealTTY) {
+ SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SYS_ADMIN)));
+
+ // Make this a session leader, which also drops the controlling terminal.
+ // In the gVisor test environment, this test will be run as the session
+ // leader already (as the sentry init process).
+ if (!IsRunningOnGvisor()) {
+ ASSERT_THAT(setsid(), SyscallSucceeds());
+ }
+
+ FileDescriptor master =
+ ASSERT_NO_ERRNO_AND_VALUE(Open("/dev/ptmx", O_RDWR | O_NONBLOCK));
+ FileDescriptor slave = ASSERT_NO_ERRNO_AND_VALUE(OpenSlave(master));
+
+ // Make slave the controlling terminal.
+ ASSERT_THAT(ioctl(slave.get(), TIOCSCTTY, 0), SyscallSucceeds());
+
+ // Fork, join a new session, and try to steal the parent's controlling
+ // terminal, which should succeed when we have CAP_SYS_ADMIN and pass an arg
+ // of 1.
+ pid_t child = fork();
+ if (!child) {
+ ASSERT_THAT(setsid(), SyscallSucceeds());
+ // We shouldn't be able to steal the terminal with the wrong arg value.
+ TEST_PCHECK(ioctl(slave.get(), TIOCSCTTY, 0));
+ // We should be able to steal it here.
+ TEST_PCHECK(!ioctl(slave.get(), TIOCSCTTY, 1));
+ _exit(0);
+ }
+
+ int wstatus;
+ ASSERT_THAT(waitpid(child, &wstatus, 0), SyscallSucceedsWithValue(child));
+ ASSERT_EQ(wstatus, 0);
+}
+
+} // namespace
+} // namespace testing
+} // namespace gvisor
diff --git a/test/util/BUILD b/test/util/BUILD
index 52f8b9e1f..25ed9c944 100644
--- a/test/util/BUILD
+++ b/test/util/BUILD
@@ -191,6 +191,17 @@ cc_test(
)
cc_library(
+ name = "pty_util",
+ testonly = 1,
+ srcs = ["pty_util.cc"],
+ hdrs = ["pty_util.h"],
+ deps = [
+ ":file_descriptor",
+ ":posix_error",
+ ],
+)
+
+cc_library(
name = "signal_util",
testonly = 1,
srcs = ["signal_util.cc"],
diff --git a/test/util/pty_util.cc b/test/util/pty_util.cc
new file mode 100644
index 000000000..c0fd9a095
--- /dev/null
+++ b/test/util/pty_util.cc
@@ -0,0 +1,45 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "test/util/pty_util.h"
+
+#include <sys/ioctl.h>
+#include <termios.h>
+
+#include "test/util/file_descriptor.h"
+#include "test/util/posix_error.h"
+
+namespace gvisor {
+namespace testing {
+
+PosixErrorOr<FileDescriptor> OpenSlave(const FileDescriptor& master) {
+ // Get pty index.
+ int n;
+ int ret = ioctl(master.get(), TIOCGPTN, &n);
+ if (ret < 0) {
+ return PosixError(errno, "ioctl(TIOCGPTN) failed");
+ }
+
+ // Unlock pts.
+ int unlock = 0;
+ ret = ioctl(master.get(), TIOCSPTLCK, &unlock);
+ if (ret < 0) {
+ return PosixError(errno, "ioctl(TIOSPTLCK) failed");
+ }
+
+ return Open(absl::StrCat("/dev/pts/", n), O_RDWR | O_NONBLOCK);
+}
+
+} // namespace testing
+} // namespace gvisor
diff --git a/test/util/pty_util.h b/test/util/pty_util.h
new file mode 100644
index 000000000..367b14f15
--- /dev/null
+++ b/test/util/pty_util.h
@@ -0,0 +1,30 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef GVISOR_TEST_UTIL_PTY_UTIL_H_
+#define GVISOR_TEST_UTIL_PTY_UTIL_H_
+
+#include "test/util/file_descriptor.h"
+#include "test/util/posix_error.h"
+
+namespace gvisor {
+namespace testing {
+
+// Opens the slave end of the passed master as R/W and nonblocking.
+PosixErrorOr<FileDescriptor> OpenSlave(const FileDescriptor& master);
+
+} // namespace testing
+} // namespace gvisor
+
+#endif // GVISOR_TEST_UTIL_PTY_UTIL_H_