Implement /proc/net/unix.

PiperOrigin-RevId: 232948478
Change-Id: Ib830121e5e79afaf5d38d17aeef5a1ef97913d23

3 files changed, 270 insertions, 0 deletions

diff --git a/test/syscalls/BUILD b/test/syscalls/BUILD
index 148d9c366..53da121ec 100644
--- a/test/syscalls/BUILD
+++ b/test/syscalls/BUILD
@@ -534,6 +534,13 @@ syscall_test(
 
 syscall_test(test = "//test/syscalls/linux:write_test")
 
+syscall_test(
+    test = "//test/syscalls/linux:proc_net_unix_test",
+    # Unix domain socket creation isn't supported on all file systems. The
+    # sentry-internal tmpfs is known to support it.
+    use_tmpfs = True,
+)
+
 go_binary(
     name = "syscall_test_runner",
     srcs = ["syscall_test_runner.go"],
diff --git a/test/syscalls/linux/BUILD b/test/syscalls/linux/BUILD
index a311ca12c..590ee1659 100644
--- a/test/syscalls/linux/BUILD
+++ b/test/syscalls/linux/BUILD
@@ -3102,3 +3102,20 @@ cc_binary(
         "@com_google_googletest//:gtest",
     ],
 )
+
+cc_binary(
+    name = "proc_net_unix_test",
+    testonly = 1,
+    srcs = ["proc_net_unix.cc"],
+    linkstatic = 1,
+    deps = [
+        ":unix_domain_socket_test_util",
+        "//test/util:file_descriptor",
+        "//test/util:fs_util",
+        "//test/util:test_main",
+        "//test/util:test_util",
+        "@com_google_absl//absl/strings",
+        "@com_google_absl//absl/strings:str_format",
+        "@com_google_googletest//:gtest",
+    ],
+)
diff --git a/test/syscalls/linux/proc_net_unix.cc b/test/syscalls/linux/proc_net_unix.cc
new file mode 100644
index 000000000..ea7c93012
--- /dev/null
+++ b/test/syscalls/linux/proc_net_unix.cc
@@ -0,0 +1,246 @@
+// Copyright 2019 Google LLC
+//
+// 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 "gtest/gtest.h"
+#include "gtest/gtest.h"
+#include "absl/strings/numbers.h"
+#include "absl/strings/str_format.h"
+#include "absl/strings/str_join.h"
+#include "absl/strings/str_split.h"
+#include "test/syscalls/linux/unix_domain_socket_test_util.h"
+#include "test/util/file_descriptor.h"
+#include "test/util/fs_util.h"
+#include "test/util/test_util.h"
+
+namespace gvisor {
+namespace testing {
+namespace {
+
+using absl::StrCat;
+using absl::StreamFormat;
+using absl::StrFormat;
+
+constexpr char kProcNetUnixHeader[] =
+    "Num       RefCount Protocol Flags    Type St Inode Path";
+
+// UnixEntry represents a single entry from /proc/net/unix.
+struct UnixEntry {
+  uintptr_t addr;
+  uint64_t refs;
+  uint64_t protocol;
+  uint64_t flags;
+  uint64_t type;
+  uint64_t state;
+  uint64_t inode;
+  std::string path;
+};
+
+std::string ExtractPath(const struct sockaddr* addr) {
+  const char* path =
+      reinterpret_cast<const struct sockaddr_un*>(addr)->sun_path;
+  // Note: sockaddr_un.sun_path is an embedded character array of length
+  // UNIX_PATH_MAX, so we can always safely dereference the first 2 bytes below.
+  //
+  // The kernel also enforces that the path is always null terminated.
+  if (path[0] == 0) {
+    // Abstract socket paths are null padded to the end of the struct
+    // sockaddr. However, these null bytes may or may not show up in
+    // /proc/net/unix depending on the kernel version. Truncate after the first
+    // null byte (by treating path as a c-std::string).
+    return StrCat("@", &path[1]);
+  }
+  return std::string(path);
+}
+
+// Returns a parsed representation of /proc/net/unix entries.
+PosixErrorOr<std::vector<UnixEntry>> ProcNetUnixEntries() {
+  std::string content;
+  RETURN_IF_ERRNO(GetContents("/proc/net/unix", &content));
+
+  bool skipped_header = false;
+  std::vector<UnixEntry> entries;
+  std::vector<std::string> lines = absl::StrSplit(content, absl::ByAnyChar("\n"));
+  for (std::string line : lines) {
+    if (!skipped_header) {
+      EXPECT_EQ(line, kProcNetUnixHeader);
+      skipped_header = true;
+      continue;
+    }
+    if (line.empty()) {
+      continue;
+    }
+
+    // Abstract socket paths can have trailing null bytes in them depending on
+    // the linux version. Strip off everything after a null byte, including the
+    // null byte.
+    std::size_t null_pos = line.find('\0');
+    if (null_pos != std::string::npos) {
+      line.erase(null_pos);
+    }
+
+    // Parse a single entry from /proc/net/unix.
+    //
+    // Sample file:
+    //
+    // clang-format off
+    //
+    // Num       RefCount Protocol Flags    Type St Inode Path"
+    // ffffa130e7041c00: 00000002 00000000 00010000 0001 01 1299413685 /tmp/control_server/13293772586877554487
+    // ffffa14f547dc400: 00000002 00000000 00010000 0001 01  3793 @remote_coredump
+    //
+    // clang-format on
+    //
+    // Note that from the second entry, the inode number can be padded using
+    // spaces, so we need to handle it separately during parsing. See
+    // net/unix/af_unix.c:unix_seq_show() for how these entries are produced. In
+    // particular, only the inode field is padded with spaces.
+    UnixEntry entry;
+
+    // Process the first 6 fields, up to but not including "Inode".
+    std::vector<std::string> fields = absl::StrSplit(line, absl::MaxSplits(' ', 6));
+
+    if (fields.size() < 7) {
+      return PosixError(EINVAL, StrFormat("Invalid entry: '%s'\n", line));
+    }
+
+    // AtoiBase can't handle the ':' in the "Num" field, so strip it out.
+    std::vector<std::string> addr = absl::StrSplit(fields[0], ':');
+    ASSIGN_OR_RETURN_ERRNO(entry.addr, AtoiBase(addr[0], 16));
+
+    ASSIGN_OR_RETURN_ERRNO(entry.refs, AtoiBase(fields[1], 16));
+    ASSIGN_OR_RETURN_ERRNO(entry.protocol, AtoiBase(fields[2], 16));
+    ASSIGN_OR_RETURN_ERRNO(entry.flags, AtoiBase(fields[3], 16));
+    ASSIGN_OR_RETURN_ERRNO(entry.type, AtoiBase(fields[4], 16));
+    ASSIGN_OR_RETURN_ERRNO(entry.state, AtoiBase(fields[5], 16));
+
+    absl::string_view rest = absl::StripAsciiWhitespace(fields[6]);
+    fields = absl::StrSplit(rest, absl::MaxSplits(' ', 1));
+    if (fields.empty()) {
+      return PosixError(
+          EINVAL, StrFormat("Invalid entry, missing 'Inode': '%s'\n", line));
+    }
+    ASSIGN_OR_RETURN_ERRNO(entry.inode, AtoiBase(fields[0], 10));
+
+    entry.path = "";
+    if (fields.size() > 1) {
+      entry.path = fields[1];
+    }
+
+    entries.push_back(entry);
+  }
+
+  return entries;
+}
+
+// Finds the first entry in 'entries' for which 'predicate' returns true.
+// Returns true on match, and sets 'match' to point to the matching entry.
+bool FindBy(std::vector<UnixEntry> entries, UnixEntry* match,
+            std::function<bool(UnixEntry)> predicate) {
+  for (int i = 0; i < entries.size(); ++i) {
+    if (predicate(entries[i])) {
+      *match = entries[i];
+      return true;
+    }
+  }
+  return false;
+}
+
+bool FindByPath(std::vector<UnixEntry> entries, UnixEntry* match,
+                const std::string& path) {
+  return FindBy(entries, match, [path](UnixEntry e) { return e.path == path; });
+}
+
+TEST(ProcNetUnix, Exists) {
+  const std::string content =
+      ASSERT_NO_ERRNO_AND_VALUE(GetContents("/proc/net/unix"));
+  const std::string header_line = StrCat(kProcNetUnixHeader, "\n");
+  if (IsRunningOnGvisor()) {
+    // Should be just the header since we don't have any unix domain sockets
+    // yet.
+    EXPECT_EQ(content, header_line);
+  } else {
+    // However, on a general linux machine, we could have abitrary sockets on
+    // the system, so just check the header.
+    EXPECT_THAT(content, ::testing::StartsWith(header_line));
+  }
+}
+
+TEST(ProcNetUnix, FilesystemBindAcceptConnect) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(
+      FilesystemBoundUnixDomainSocketPair(SOCK_STREAM).Create());
+
+  std::string path1 = ExtractPath(sockets->first_addr());
+  std::string path2 = ExtractPath(sockets->second_addr());
+  std::cout << StreamFormat("Server socket address: %s\n", path1);
+  std::cout << StreamFormat("Client socket address: %s\n", path2);
+
+  std::vector<UnixEntry> entries =
+      ASSERT_NO_ERRNO_AND_VALUE(ProcNetUnixEntries());
+  if (IsRunningOnGvisor()) {
+    EXPECT_EQ(entries.size(), 2);
+  }
+
+  // The server-side socket's path is listed in the socket entry...
+  UnixEntry s1;
+  EXPECT_TRUE(FindByPath(entries, &s1, path1));
+
+  // ... but the client-side socket's path is not.
+  UnixEntry s2;
+  EXPECT_FALSE(FindByPath(entries, &s2, path2));
+}
+
+TEST(ProcNetUnix, AbstractBindAcceptConnect) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(
+      AbstractBoundUnixDomainSocketPair(SOCK_STREAM).Create());
+
+  std::string path1 = ExtractPath(sockets->first_addr());
+  std::string path2 = ExtractPath(sockets->second_addr());
+  std::cout << StreamFormat("Server socket address: '%s'\n", path1);
+  std::cout << StreamFormat("Client socket address: '%s'\n", path2);
+
+  std::vector<UnixEntry> entries =
+      ASSERT_NO_ERRNO_AND_VALUE(ProcNetUnixEntries());
+  if (IsRunningOnGvisor()) {
+    EXPECT_EQ(entries.size(), 2);
+  }
+
+  // The server-side socket's path is listed in the socket entry...
+  UnixEntry s1;
+  EXPECT_TRUE(FindByPath(entries, &s1, path1));
+
+  // ... but the client-side socket's path is not.
+  UnixEntry s2;
+  EXPECT_FALSE(FindByPath(entries, &s2, path2));
+}
+
+TEST(ProcNetUnix, SocketPair) {
+  // Under gvisor, ensure a socketpair() syscall creates exactly 2 new
+  // entries. We have no way to verify this under Linux, as we have no control
+  // over socket creation on a general Linux machine.
+  SKIP_IF(!IsRunningOnGvisor());
+
+  std::vector<UnixEntry> entries =
+      ASSERT_NO_ERRNO_AND_VALUE(ProcNetUnixEntries());
+  ASSERT_EQ(entries.size(), 0);
+
+  auto sockets =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_STREAM).Create());
+
+  entries = ASSERT_NO_ERRNO_AND_VALUE(ProcNetUnixEntries());
+  EXPECT_EQ(entries.size(), 2);
+}
+
+}  // namespace
+}  // namespace testing
+}  // namespace gvisor