Read iptables via sockopts.

PiperOrigin-RevId: 264180125

3 files changed, 226 insertions, 0 deletions

diff --git a/test/syscalls/BUILD b/test/syscalls/BUILD
index f50d83f38..6b8c4a39d 100644
--- a/test/syscalls/BUILD
+++ b/test/syscalls/BUILD
@@ -180,6 +180,10 @@ syscall_test(
 )
 
 syscall_test(
+    test = "//test/syscalls/linux:iptables_test",
+)
+
+syscall_test(
     size = "medium",
     test = "//test/syscalls/linux:itimer_test",
 )
diff --git a/test/syscalls/linux/BUILD b/test/syscalls/linux/BUILD
index db0a1e661..e2b0716ef 100644
--- a/test/syscalls/linux/BUILD
+++ b/test/syscalls/linux/BUILD
@@ -913,6 +913,24 @@ cc_library(
 )
 
 cc_binary(
+    name = "iptables_test",
+    testonly = 1,
+    srcs = [
+        "iptables.cc",
+    ],
+    linkstatic = 1,
+    deps = [
+        ":iptables_types",
+        ":socket_test_util",
+        "//test/util:capability_util",
+        "//test/util:file_descriptor",
+        "//test/util:test_main",
+        "//test/util:test_util",
+        "@com_google_googletest//:gtest",
+    ],
+)
+
+cc_binary(
     name = "itimer_test",
     testonly = 1,
     srcs = ["itimer.cc"],
diff --git a/test/syscalls/linux/iptables.cc b/test/syscalls/linux/iptables.cc
new file mode 100644
index 000000000..b8e4ece64
--- /dev/null
+++ b/test/syscalls/linux/iptables.cc
@@ -0,0 +1,204 @@
+// 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/syscalls/linux/iptables.h"
+
+#include <arpa/inet.h>
+#include <linux/capability.h>
+#include <linux/netfilter/x_tables.h>
+#include <net/if.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/ip_icmp.h>
+#include <stdio.h>
+#include <sys/poll.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <algorithm>
+
+#include "gtest/gtest.h"
+#include "test/util/capability_util.h"
+#include "test/util/file_descriptor.h"
+#include "test/util/test_util.h"
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+constexpr char kNatTablename[] = "nat";
+constexpr char kErrorTarget[] = "ERROR";
+constexpr size_t kEmptyStandardEntrySize =
+    sizeof(struct ipt_entry) + sizeof(struct ipt_standard_target);
+constexpr size_t kEmptyErrorEntrySize =
+    sizeof(struct ipt_entry) + sizeof(struct ipt_error_target);
+
+TEST(IPTablesBasic, CreateSocket) {
+  SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_NET_RAW)));
+
+  int sock;
+  ASSERT_THAT(sock = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP),
+              SyscallSucceeds());
+
+  ASSERT_THAT(close(sock), SyscallSucceeds());
+}
+
+TEST(IPTablesBasic, FailSockoptNonRaw) {
+  // Even if the user has CAP_NET_RAW, they shouldn't be able to use the
+  // iptables sockopts with a non-raw socket.
+  SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_NET_RAW)));
+
+  int sock;
+  ASSERT_THAT(sock = socket(AF_INET, SOCK_DGRAM, 0), SyscallSucceeds());
+
+  struct ipt_getinfo info = {};
+  snprintf(info.name, XT_TABLE_MAXNAMELEN, "%s", kNatTablename);
+  socklen_t info_size = sizeof(info);
+  EXPECT_THAT(getsockopt(sock, IPPROTO_IP, SO_GET_INFO, &info, &info_size),
+              SyscallFailsWithErrno(ENOPROTOOPT));
+
+  ASSERT_THAT(close(sock), SyscallSucceeds());
+}
+
+// Fixture for iptables tests.
+class IPTablesTest : public ::testing::Test {
+ protected:
+  // Creates a socket to be used in tests.
+  void SetUp() override;
+
+  // Closes the socket created by SetUp().
+  void TearDown() override;
+
+  // The socket via which to manipulate iptables.
+  int s_;
+};
+
+void IPTablesTest::SetUp() {
+  SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_NET_RAW)));
+
+  ASSERT_THAT(s_ = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP), SyscallSucceeds());
+}
+
+void IPTablesTest::TearDown() {
+  SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_NET_RAW)));
+
+  EXPECT_THAT(close(s_), SyscallSucceeds());
+}
+
+// This tests the initial state of a machine with empty iptables. We don't have
+// a guarantee that the iptables are empty when running in native, but we can
+// test that gVisor has the same initial state that a newly-booted Linux machine
+// would have.
+TEST_F(IPTablesTest, InitialState) {
+  SKIP_IF(!IsRunningOnGvisor());
+  SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_NET_RAW)));
+
+  //
+  // Get info via sockopt.
+  //
+  struct ipt_getinfo info = {};
+  snprintf(info.name, XT_TABLE_MAXNAMELEN, "%s", kNatTablename);
+  socklen_t info_size = sizeof(info);
+  ASSERT_THAT(getsockopt(s_, IPPROTO_IP, SO_GET_INFO, &info, &info_size),
+              SyscallSucceeds());
+
+  // The nat table supports PREROUTING, and OUTPUT.
+  unsigned int valid_hooks = (1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_LOCAL_OUT) |
+                             (1 << NF_IP_POST_ROUTING) | (1 << NF_IP_LOCAL_IN);
+
+  EXPECT_EQ(info.valid_hooks, valid_hooks);
+
+  // Each chain consists of an empty entry with a standard target..
+  EXPECT_EQ(info.hook_entry[NF_IP_PRE_ROUTING], 0);
+  EXPECT_EQ(info.hook_entry[NF_IP_LOCAL_IN], kEmptyStandardEntrySize);
+  EXPECT_EQ(info.hook_entry[NF_IP_LOCAL_OUT], kEmptyStandardEntrySize * 2);
+  EXPECT_EQ(info.hook_entry[NF_IP_POST_ROUTING], kEmptyStandardEntrySize * 3);
+
+  // The underflow points are the same as the entry points.
+  EXPECT_EQ(info.underflow[NF_IP_PRE_ROUTING], 0);
+  EXPECT_EQ(info.underflow[NF_IP_LOCAL_IN], kEmptyStandardEntrySize);
+  EXPECT_EQ(info.underflow[NF_IP_LOCAL_OUT], kEmptyStandardEntrySize * 2);
+  EXPECT_EQ(info.underflow[NF_IP_POST_ROUTING], kEmptyStandardEntrySize * 3);
+
+  // One entry for each chain, plus an error entry at the end.
+  EXPECT_EQ(info.num_entries, 5);
+
+  EXPECT_EQ(info.size, 4 * kEmptyStandardEntrySize + kEmptyErrorEntrySize);
+  EXPECT_EQ(strcmp(info.name, kNatTablename), 0);
+
+  //
+  // Use info to get entries.
+  //
+  socklen_t entries_size = sizeof(struct ipt_get_entries) + info.size;
+  struct ipt_get_entries* entries =
+      static_cast<struct ipt_get_entries*>(malloc(entries_size));
+  snprintf(entries->name, XT_TABLE_MAXNAMELEN, "%s", kNatTablename);
+  entries->size = info.size;
+  ASSERT_THAT(
+      getsockopt(s_, IPPROTO_IP, SO_GET_ENTRIES, entries, &entries_size),
+      SyscallSucceeds());
+
+  // Verify the name and size.
+  ASSERT_EQ(info.size, entries->size);
+  ASSERT_EQ(strcmp(entries->name, kNatTablename), 0);
+
+  // Verify that the entrytable is 4 entries with accept targets and no matches
+  // followed by a single error target.
+  size_t entry_offset = 0;
+  while (entry_offset < entries->size) {
+    struct ipt_entry* entry = reinterpret_cast<struct ipt_entry*>(
+        reinterpret_cast<char*>(entries->entrytable) + entry_offset);
+
+    // ip should be zeroes.
+    struct ipt_ip zeroed = {};
+    EXPECT_EQ(memcmp(static_cast<void*>(&zeroed),
+                     static_cast<void*>(&entry->ip), sizeof(zeroed)),
+              0);
+
+    // target_offset should be zero.
+    EXPECT_EQ(entry->target_offset, sizeof(ipt_entry));
+
+    if (entry_offset < kEmptyStandardEntrySize * 4) {
+      // The first 4 entries are standard targets
+      struct ipt_standard_target* target =
+          reinterpret_cast<struct ipt_standard_target*>(entry->elems);
+      EXPECT_EQ(entry->next_offset, kEmptyStandardEntrySize);
+      EXPECT_EQ(target->target.u.user.target_size, sizeof(*target));
+      EXPECT_EQ(strcmp(target->target.u.user.name, ""), 0);
+      EXPECT_EQ(target->target.u.user.revision, 0);
+      // This is what's returned for an accept verdict. I don't know why.
+      EXPECT_EQ(target->verdict, -NF_ACCEPT - 1);
+    } else {
+      // The last entry is an error target
+      struct ipt_error_target* target =
+          reinterpret_cast<struct ipt_error_target*>(entry->elems);
+      EXPECT_EQ(entry->next_offset, kEmptyErrorEntrySize);
+      EXPECT_EQ(target->target.u.user.target_size, sizeof(*target));
+      EXPECT_EQ(strcmp(target->target.u.user.name, kErrorTarget), 0);
+      EXPECT_EQ(target->target.u.user.revision, 0);
+      EXPECT_EQ(strcmp(target->errorname, kErrorTarget), 0);
+    }
+
+    entry_offset += entry->next_offset;
+  }
+
+  free(entries);
+}
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor