win: Expect uneven symbolic link support

As mentioned at
https://chromium-review.googlesource.com/c/chromium/src/+/735820#message-e8b199498d8b850f2612c46648069d819dd47517,
the typical Windows behavior for symbolic links requires administrative
privileges.

Symbolic links are available to non-administrators in Windows 10.0.15063
and later (1703, Creators Update), provided that developer mode has been
enabled and SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE is passed to
CreateSymbolicLink(). See
https://blogs.windows.com/buildingapps/2016/12/02/symlinks-windows-10/.

This adds SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE to uses of
CreateSymbolicLink(), and creates test::CanCreateSymbolicLinks() to
determine whether symbolic link creation is possible. Tests that
exercise symbolic links are adapted to gate all symbolic link operations
on this test.

Test: crashpad_util_test DirectoryReader.*:Filesystem.*
Change-Id: I8250cadd974ffcc7abe32701a0d5bc487061baf0
Bug: crashpad:
Reviewed-on: https://chromium-review.googlesource.com/739472
Commit-Queue: Mark Mentovai <mark@chromium.org>
Reviewed-by: Joshua Peraza <jperaza@chromium.org>
Reviewed-by: Scott Graham <scottmg@chromium.org>

compat/compat.gyp

@@ -54,6 +54,7 @@
         'win/sys/types.h',
         'win/time.cc',
         'win/time.h',
+        'win/winbase.h',
         'win/winnt.h',
         'win/winternl.h',
       ],

compat/win/winbase.h

@@ -0,0 +1,27 @@
+// Copyright 2017 The Crashpad Authors. All rights reserved.
+//
+// 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 CRASHPAD_COMPAT_WIN_WINBASE_H_
+#define CRASHPAD_COMPAT_WIN_WINBASE_H_
+
+// include_next <winbase.h>
+#include <../um/winbase.h>
+
+// 10.0.15063.0 SDK
+
+#ifndef SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE
+#define SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE (0x2)
+#endif
+
+#endif  // CRASHPAD_COMPAT_WIN_WINBASE_H_

test/gtest_disabled.cc

@@ -51,7 +51,7 @@ void DisabledTestGtestEnvironment::DisabledTest() {
       "[ DISABLED ] %s\n",
       disabled_test.c_str());
 
-  disabled_tests_.insert(disabled_test);
+  disabled_tests_.push_back(disabled_test);
 }
 
 DisabledTestGtestEnvironment::DisabledTestGtestEnvironment()

test/gtest_disabled.h

@@ -15,8 +15,8 @@
 #ifndef CRASHPAD_TEST_GTEST_DISABLED_H_
 #define CRASHPAD_TEST_GTEST_DISABLED_H_
 
-#include <set>
 #include <string>
+#include <vector>
 
 #include "base/macros.h"
 #include "gtest/gtest.h"
@@ -54,7 +54,7 @@ class DisabledTestGtestEnvironment final : public testing::Environment {
   // testing::Environment:
   void TearDown() override;
 
-  std::set<std::string> disabled_tests_;
+  std::vector<std::string> disabled_tests_;
 
   DISALLOW_COPY_AND_ASSIGN(DisabledTestGtestEnvironment);
 };

util/file/directory_reader_test.cc

@@ -21,6 +21,7 @@
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "gtest/gtest.h"
+#include "test/gtest_disabled.h"
 #include "test/scoped_temp_dir.h"
 #include "util/file/file_io.h"
 #include "util/file/filesystem.h"
@@ -30,6 +31,51 @@ namespace crashpad {
 namespace test {
 namespace {
 
+TEST(DirectoryReader, BadPaths) {
+  DirectoryReader reader;
+  EXPECT_FALSE(reader.Open(base::FilePath()));
+
+  ScopedTempDir temp_dir;
+  base::FilePath file(temp_dir.path().Append(FILE_PATH_LITERAL("file")));
+  ASSERT_TRUE(CreateFile(file));
+  EXPECT_FALSE(reader.Open(file));
+
+  EXPECT_FALSE(
+      reader.Open(temp_dir.path().Append(FILE_PATH_LITERAL("doesntexist"))));
+}
+
+#if !defined(OS_FUCHSIA)
+
+TEST(DirectoryReader, BadPaths_SymbolicLinks) {
+  if (!CanCreateSymbolicLinks()) {
+    DISABLED_TEST();
+  }
+
+  ScopedTempDir temp_dir;
+  base::FilePath file(temp_dir.path().Append(FILE_PATH_LITERAL("file")));
+  ASSERT_TRUE(CreateFile(file));
+
+  base::FilePath link(temp_dir.path().Append(FILE_PATH_LITERAL("link")));
+  ASSERT_TRUE(CreateSymbolicLink(file, link));
+
+  DirectoryReader reader;
+  EXPECT_FALSE(reader.Open(link));
+
+  ASSERT_TRUE(LoggingRemoveFile(file));
+  EXPECT_FALSE(reader.Open(link));
+}
+
+#endif  // !OS_FUCHSIA
+
+TEST(DirectoryReader, EmptyDirectory) {
+  ScopedTempDir temp_dir;
+  DirectoryReader reader;
+
+  ASSERT_TRUE(reader.Open(temp_dir.path()));
+  base::FilePath filename;
+  EXPECT_EQ(reader.NextFile(&filename), DirectoryReader::Result::kNoMoreFiles);
+}
+
 void ExpectFiles(const std::set<base::FilePath>& files,
                  const std::set<base::FilePath>& expected) {
   EXPECT_EQ(files.size(), expected.size());
@@ -41,36 +87,7 @@ void ExpectFiles(const std::set<base::FilePath>& files,
   }
 }
 
-TEST(DirectoryReader, BadPaths) {
+void TestFilesAndDirectories(bool symbolic_links) {
-  DirectoryReader reader;
-  EXPECT_FALSE(reader.Open(base::FilePath()));
-
-  ScopedTempDir temp_dir;
-  base::FilePath file(temp_dir.path().Append(FILE_PATH_LITERAL("file")));
-  ASSERT_TRUE(CreateFile(file));
-  EXPECT_FALSE(reader.Open(file));
-
-  base::FilePath link(temp_dir.path().Append(FILE_PATH_LITERAL("link")));
-  ASSERT_TRUE(CreateSymbolicLink(file, link));
-  EXPECT_FALSE(reader.Open(link));
-
-  ASSERT_TRUE(LoggingRemoveFile(file));
-  EXPECT_FALSE(reader.Open(link));
-
-  EXPECT_FALSE(
-      reader.Open(temp_dir.path().Append(FILE_PATH_LITERAL("doesntexist"))));
-}
-
-TEST(DirectoryReader, EmptyDirectory) {
-  ScopedTempDir temp_dir;
-  DirectoryReader reader;
-
-  ASSERT_TRUE(reader.Open(temp_dir.path()));
-  base::FilePath filename;
-  EXPECT_EQ(reader.NextFile(&filename), DirectoryReader::Result::kNoMoreFiles);
-}
-
-TEST(DirectoryReader, FilesAndDirectories) {
   ScopedTempDir temp_dir;
   std::set<base::FilePath> expected_files;
 
@@ -78,17 +95,6 @@ TEST(DirectoryReader, FilesAndDirectories) {
   ASSERT_TRUE(CreateFile(temp_dir.path().Append(file)));
   EXPECT_TRUE(expected_files.insert(file).second);
 
-  base::FilePath link(FILE_PATH_LITERAL("link"));
-  ASSERT_TRUE(CreateSymbolicLink(temp_dir.path().Append(file),
-                                 temp_dir.path().Append(link)));
-  EXPECT_TRUE(expected_files.insert(link).second);
-
-  base::FilePath dangling(FILE_PATH_LITERAL("dangling"));
-  ASSERT_TRUE(
-      CreateSymbolicLink(base::FilePath(FILE_PATH_LITERAL("not_a_file")),
-                         temp_dir.path().Append(dangling)));
-  EXPECT_TRUE(expected_files.insert(dangling).second);
-
   base::FilePath directory(FILE_PATH_LITERAL("directory"));
   ASSERT_TRUE(LoggingCreateDirectory(temp_dir.path().Append(directory),
                                      FilePermissions::kWorldReadable,
@@ -99,6 +105,23 @@ TEST(DirectoryReader, FilesAndDirectories) {
   ASSERT_TRUE(
       CreateFile(temp_dir.path().Append(directory).Append(nested_file)));
 
+#if !defined(OS_FUCHSIA)
+
+  if (symbolic_links) {
+    base::FilePath link(FILE_PATH_LITERAL("link"));
+    ASSERT_TRUE(CreateSymbolicLink(temp_dir.path().Append(file),
+                                   temp_dir.path().Append(link)));
+    EXPECT_TRUE(expected_files.insert(link).second);
+
+    base::FilePath dangling(FILE_PATH_LITERAL("dangling"));
+    ASSERT_TRUE(
+        CreateSymbolicLink(base::FilePath(FILE_PATH_LITERAL("not_a_file")),
+                           temp_dir.path().Append(dangling)));
+    EXPECT_TRUE(expected_files.insert(dangling).second);
+  }
+
+#endif  // !OS_FUCHSIA
+
   std::set<base::FilePath> files;
   DirectoryReader reader;
   ASSERT_TRUE(reader.Open(temp_dir.path()));
@@ -113,6 +136,22 @@ TEST(DirectoryReader, FilesAndDirectories) {
   ExpectFiles(files, expected_files);
 }
 
+TEST(DirectoryReader, FilesAndDirectories) {
+  TestFilesAndDirectories(false);
+}
+
+#if !defined(OS_FUCHSIA)
+
+TEST(DirectoryReader, FilesAndDirectories_SymbolicLinks) {
+  if (!CanCreateSymbolicLinks()) {
+    DISABLED_TEST();
+  }
+
+  TestFilesAndDirectories(true);
+}
+
+#endif  // !OS_FUCHSIA
+
 }  // namespace
 }  // namespace test
 }  // namespace crashpad

util/file/filesystem_posix.cc

@@ -56,7 +56,7 @@ bool MoveFileOrDirectory(const base::FilePath& source,
 bool IsRegularFile(const base::FilePath& path) {
   struct stat st;
   if (lstat(path.value().c_str(), &st) != 0) {
-    PLOG_IF(ERROR, errno != ENOENT) << "stat " << path.value();
+    PLOG(ERROR) << "stat " << path.value();
     return false;
   }
   return S_ISREG(st.st_mode);
@@ -69,11 +69,9 @@ bool IsDirectory(const base::FilePath& path, bool allow_symlinks) {
       PLOG(ERROR) << "stat " << path.value();
       return false;
     }
-  } else {
+  } else if (lstat(path.value().c_str(), &st) != 0) {
-    if (lstat(path.value().c_str(), &st) != 0) {
+    PLOG(ERROR) << "lstat " << path.value();
-      PLOG(ERROR) << "lstat " << path.value();
+    return false;
-      return false;
-    }
   }
   return S_ISDIR(st.st_mode);
 }

util/file/filesystem_test.cc

@@ -16,6 +16,7 @@
 
 #include "base/logging.h"
 #include "gtest/gtest.h"
+#include "test/gtest_disabled.h"
 #include "test/scoped_temp_dir.h"
 #include "util/file/filesystem_test_util.h"
 
@@ -60,16 +61,16 @@ TEST(Filesystem, MoveFileOrDirectory) {
   base::FilePath file2(temp_dir.path().Append(FILE_PATH_LITERAL("file2")));
   EXPECT_TRUE(MoveFileOrDirectory(file, file2));
   EXPECT_TRUE(IsRegularFile(file2));
-  EXPECT_FALSE(IsRegularFile(file));
+  EXPECT_FALSE(PathExists(file));
 
   EXPECT_FALSE(MoveFileOrDirectory(file, file2));
   EXPECT_TRUE(IsRegularFile(file2));
-  EXPECT_FALSE(IsRegularFile(file));
+  EXPECT_FALSE(PathExists(file));
 
   ASSERT_TRUE(CreateFile(file));
   EXPECT_TRUE(MoveFileOrDirectory(file2, file));
   EXPECT_TRUE(IsRegularFile(file));
-  EXPECT_FALSE(IsRegularFile(file2));
+  EXPECT_FALSE(PathExists(file2));
 
   // directories
   base::FilePath dir(temp_dir.path().Append(FILE_PATH_LITERAL("dir")));
@@ -100,6 +101,19 @@ TEST(Filesystem, MoveFileOrDirectory) {
   EXPECT_FALSE(MoveFileOrDirectory(dir2, file));
   EXPECT_TRUE(IsDirectory(dir2, false));
   EXPECT_TRUE(IsRegularFile(file));
+}
+
+#if !defined(OS_FUCHSIA)
+
+TEST(Filesystem, MoveFileOrDirectory_SymbolicLinks) {
+  if (!CanCreateSymbolicLinks()) {
+    DISABLED_TEST();
+  }
+
+  ScopedTempDir temp_dir;
+
+  base::FilePath file(temp_dir.path().Append(FILE_PATH_LITERAL("file")));
+  ASSERT_TRUE(CreateFile(file));
 
   // file links
   base::FilePath link(temp_dir.path().Append(FILE_PATH_LITERAL("link")));
@@ -135,6 +149,10 @@ TEST(Filesystem, MoveFileOrDirectory) {
   EXPECT_FALSE(PathExists(link));
 
   // directory links
+  base::FilePath dir(temp_dir.path().Append(FILE_PATH_LITERAL("dir")));
+  ASSERT_TRUE(
+      LoggingCreateDirectory(dir, FilePermissions::kWorldReadable, false));
+
   ASSERT_TRUE(CreateSymbolicLink(dir, link));
 
   EXPECT_TRUE(MoveFileOrDirectory(link, link2));
@@ -148,6 +166,8 @@ TEST(Filesystem, MoveFileOrDirectory) {
   EXPECT_FALSE(PathExists(link2));
 }
 
+#endif  // !OS_FUCHSIA
+
 TEST(Filesystem, IsRegularFile) {
   EXPECT_FALSE(IsRegularFile(base::FilePath()));
 
@@ -159,6 +179,18 @@ TEST(Filesystem, IsRegularFile) {
 
   ASSERT_TRUE(CreateFile(file));
   EXPECT_TRUE(IsRegularFile(file));
+}
+
+#if !defined(OS_FUCHSIA)
+
+TEST(Filesystem, IsRegularFile_SymbolicLinks) {
+  if (!CanCreateSymbolicLinks()) {
+    DISABLED_TEST();
+  }
+
+  ScopedTempDir temp_dir;
+  base::FilePath file(temp_dir.path().Append(FILE_PATH_LITERAL("file")));
+  ASSERT_TRUE(CreateFile(file));
 
   base::FilePath link(temp_dir.path().Append(FILE_PATH_LITERAL("link")));
   ASSERT_TRUE(CreateSymbolicLink(file, link));
@@ -173,6 +205,8 @@ TEST(Filesystem, IsRegularFile) {
   EXPECT_FALSE(IsRegularFile(dir_link));
 }
 
+#endif  // !OS_FUCHSIA
+
 TEST(Filesystem, IsDirectory) {
   EXPECT_FALSE(IsDirectory(base::FilePath(), false));
   EXPECT_FALSE(IsDirectory(base::FilePath(), true));
@@ -187,6 +221,18 @@ TEST(Filesystem, IsDirectory) {
   ASSERT_TRUE(CreateFile(file));
   EXPECT_FALSE(IsDirectory(file, false));
   EXPECT_FALSE(IsDirectory(file, true));
+}
+
+#if !defined(OS_FUCHSIA)
+
+TEST(Filesystem, IsDirectory_SymbolicLinks) {
+  if (!CanCreateSymbolicLinks()) {
+    DISABLED_TEST();
+  }
+
+  ScopedTempDir temp_dir;
+  base::FilePath file(temp_dir.path().Append(FILE_PATH_LITERAL("file")));
+  ASSERT_TRUE(CreateFile(file));
 
   base::FilePath link(temp_dir.path().Append(FILE_PATH_LITERAL("link")));
   ASSERT_TRUE(CreateSymbolicLink(file, link));
@@ -204,6 +250,8 @@ TEST(Filesystem, IsDirectory) {
   EXPECT_TRUE(IsDirectory(dir_link, true));
 }
 
+#endif  // !OS_FUCHSIA
+
 TEST(Filesystem, RemoveFile) {
   EXPECT_FALSE(LoggingRemoveFile(base::FilePath()));
 
@@ -216,27 +264,45 @@ TEST(Filesystem, RemoveFile) {
   ASSERT_TRUE(CreateFile(file));
   EXPECT_TRUE(IsRegularFile(file));
 
+  base::FilePath dir(temp_dir.path().Append(FILE_PATH_LITERAL("dir")));
+  ASSERT_TRUE(
+      LoggingCreateDirectory(dir, FilePermissions::kWorldReadable, false));
+  EXPECT_FALSE(LoggingRemoveFile(dir));
+
+  EXPECT_TRUE(LoggingRemoveFile(file));
+  EXPECT_FALSE(PathExists(file));
+  EXPECT_FALSE(LoggingRemoveFile(file));
+}
+
+#if !defined(OS_FUCHSIA)
+
+TEST(Filesystem, RemoveFile_SymbolicLinks) {
+  if (!CanCreateSymbolicLinks()) {
+    DISABLED_TEST();
+  }
+
+  ScopedTempDir temp_dir;
+  base::FilePath file(temp_dir.path().Append(FILE_PATH_LITERAL("file")));
+  ASSERT_TRUE(CreateFile(file));
+
+  base::FilePath dir(temp_dir.path().Append(FILE_PATH_LITERAL("dir")));
+  ASSERT_TRUE(
+      LoggingCreateDirectory(dir, FilePermissions::kWorldReadable, false));
+
   base::FilePath link(temp_dir.path().Append(FILE_PATH_LITERAL("link")));
   ASSERT_TRUE(CreateSymbolicLink(file, link));
   EXPECT_TRUE(LoggingRemoveFile(link));
   EXPECT_FALSE(PathExists(link));
   EXPECT_TRUE(PathExists(file));
 
-  base::FilePath dir(temp_dir.path().Append(FILE_PATH_LITERAL("dir")));
-  ASSERT_TRUE(
-      LoggingCreateDirectory(dir, FilePermissions::kWorldReadable, false));
-  EXPECT_FALSE(LoggingRemoveFile(dir));
-
   ASSERT_TRUE(CreateSymbolicLink(dir, link));
   EXPECT_TRUE(LoggingRemoveFile(link));
   EXPECT_FALSE(PathExists(link));
   EXPECT_TRUE(PathExists(dir));
-
-  EXPECT_TRUE(LoggingRemoveFile(file));
-  EXPECT_FALSE(IsRegularFile(file));
-  EXPECT_FALSE(LoggingRemoveFile(file));
 }
 
+#endif  // !OS_FUCHSIA
+
 TEST(Filesystem, RemoveDirectory) {
   EXPECT_FALSE(LoggingRemoveDirectory(base::FilePath()));
 
@@ -253,6 +319,25 @@ TEST(Filesystem, RemoveDirectory) {
   EXPECT_FALSE(LoggingRemoveDirectory(file));
   EXPECT_FALSE(LoggingRemoveDirectory(dir));
 
+  ASSERT_TRUE(LoggingRemoveFile(file));
+  EXPECT_TRUE(LoggingRemoveDirectory(dir));
+}
+
+#if !defined(OS_FUCHSIA)
+
+TEST(Filesystem, RemoveDirectory_SymbolicLinks) {
+  if (!CanCreateSymbolicLinks()) {
+    DISABLED_TEST();
+  }
+
+  ScopedTempDir temp_dir;
+  base::FilePath dir(temp_dir.path().Append(FILE_PATH_LITERAL("dir")));
+  ASSERT_TRUE(
+      LoggingCreateDirectory(dir, FilePermissions::kWorldReadable, false));
+
+  base::FilePath file(dir.Append(FILE_PATH_LITERAL("file")));
+  EXPECT_FALSE(LoggingRemoveDirectory(file));
+
   base::FilePath link(temp_dir.path().Append(FILE_PATH_LITERAL("link")));
   ASSERT_TRUE(CreateSymbolicLink(file, link));
   EXPECT_FALSE(LoggingRemoveDirectory(link));
@@ -261,11 +346,10 @@ TEST(Filesystem, RemoveDirectory) {
   ASSERT_TRUE(CreateSymbolicLink(dir, link));
   EXPECT_FALSE(LoggingRemoveDirectory(link));
   EXPECT_TRUE(LoggingRemoveFile(link));
-
-  ASSERT_TRUE(LoggingRemoveFile(file));
-  EXPECT_TRUE(LoggingRemoveDirectory(dir));
 }
 
+#endif  // !OS_FUCHSIA
+
 }  // namespace
 }  // namespace test
 }  // namespace crashpad

util/file/filesystem_test_util.cc

@@ -20,9 +20,9 @@
 
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
-#include "build/build_config.h"
 #include "gtest/gtest.h"
 #include "test/errors.h"
+#include "test/scoped_temp_dir.h"
 #include "util/file/file_io.h"
 #include "util/file/filesystem.h"
 
@@ -37,6 +37,60 @@
 namespace crashpad {
 namespace test {
 
+namespace {
+
+#if defined(OS_WIN)
+
+// Detects the flags necessary to create symbolic links and stores them in
+// |flags| if non-nullptr, and returns true on success. If symbolic links can’t
+// be created, returns false.
+bool SymbolicLinkFlags(DWORD* flags) {
+  static DWORD symbolic_link_flags = []() {
+    ScopedTempDir temp_dir_;
+
+    base::FilePath target_path = temp_dir_.path().Append(L"target");
+    base::FilePath symlink_path = temp_dir_.path().Append(L"symlink");
+    if (::CreateSymbolicLink(
+            symlink_path.value().c_str(), target_path.value().c_str(), 0)) {
+      return 0;
+    }
+
+    DWORD error = GetLastError();
+    if (error == ERROR_PRIVILEGE_NOT_HELD) {
+      if (::CreateSymbolicLink(symlink_path.value().c_str(),
+                               target_path.value().c_str(),
+                               SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE)) {
+        return SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE;
+      }
+
+      // This may fail with ERROR_INVALID_PARAMETER if the OS is too old to
+      // understand SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE, so keep
+      // ERROR_PRIVILEGE_NOT_HELD for |error|.
+    }
+
+    // Don’t use ErrorMessage() here because the second CreateSymbolicLink() may
+    // have scrambled it. Use the saved |error| value instead.
+    EXPECT_EQ(error, ERROR_PRIVILEGE_NOT_HELD)
+        << "CreateSymbolicLink: "
+        << logging::SystemErrorCodeToString(GetLastError());
+    return -1;
+  }();
+
+  if (symbolic_link_flags == -1) {
+    return false;
+  }
+
+  if (flags) {
+    *flags = symbolic_link_flags;
+  }
+
+  return true;
+}
+
+#endif  // OS_WIN
+
+}  // namespace
+
 bool CreateFile(const base::FilePath& file) {
   ScopedFileHandle fd(LoggingOpenFileForWrite(
       file, FileWriteMode::kCreateOrFail, FilePermissions::kOwnerOnly));
@@ -44,6 +98,35 @@ bool CreateFile(const base::FilePath& file) {
   return fd.is_valid();
 }
 
+bool PathExists(const base::FilePath& path) {
+#if defined(OS_POSIX)
+  struct stat st;
+  if (lstat(path.value().c_str(), &st) != 0) {
+    EXPECT_EQ(errno, ENOENT) << ErrnoMessage("lstat ") << path.value();
+    return false;
+  }
+  return true;
+#elif defined(OS_WIN)
+  if (GetFileAttributes(path.value().c_str()) == INVALID_FILE_ATTRIBUTES) {
+    EXPECT_EQ(GetLastError(), ERROR_FILE_NOT_FOUND)
+        << ErrorMessage("GetFileAttributes ")
+        << base::UTF16ToUTF8(path.value());
+    return false;
+  }
+  return true;
+#endif
+}
+
+#if !defined(OS_FUCHSIA)
+
+bool CanCreateSymbolicLinks() {
+#if defined(OS_POSIX)
+  return true;
+#elif defined(OS_WIN)
+  return SymbolicLinkFlags(nullptr);
+#endif  // OS_POSIX
+}
+
 bool CreateSymbolicLink(const base::FilePath& target_path,
                         const base::FilePath& symlink_path) {
 #if defined(OS_POSIX)
@@ -53,35 +136,24 @@ bool CreateSymbolicLink(const base::FilePath& target_path,
     PLOG(ERROR) << "symlink";
     return false;
   }
+  return true;
 #elif defined(OS_WIN)
+  DWORD symbolic_link_flags = 0;
+  SymbolicLinkFlags(&symbolic_link_flags);
   if (!::CreateSymbolicLink(
           symlink_path.value().c_str(),
           target_path.value().c_str(),
-          IsDirectory(target_path, true) ? SYMBOLIC_LINK_FLAG_DIRECTORY : 0)) {
+          symbolic_link_flags |
+              (IsDirectory(target_path, true) ? SYMBOLIC_LINK_FLAG_DIRECTORY
+                                              : 0))) {
     PLOG(ERROR) << "CreateSymbolicLink";
     return false;
   }
-#endif  // OS_POSIX
   return true;
+#endif  // OS_POSIX
 }
 
-bool PathExists(const base::FilePath& path) {
+#endif  // !OS_FUCHSIA
-#if defined(OS_POSIX)
-  struct stat st;
-  if (lstat(path.value().c_str(), &st) != 0) {
-    EXPECT_EQ(errno, ENOENT) << ErrnoMessage("lstat ") << path.value();
-    return false;
-  }
-#elif defined(OS_WIN)
-  if (GetFileAttributes(path.value().c_str()) == INVALID_FILE_ATTRIBUTES) {
-    EXPECT_EQ(GetLastError(), ERROR_FILE_NOT_FOUND)
-        << ErrorMessage("GetFileAttributes ")
-        << base::UTF16ToUTF8(path.value());
-    return false;
-  }
-#endif
-  return true;
-}
 
 }  // namespace test
 }  // namespace crashpad

util/file/filesystem_test_util.h

@@ -17,15 +17,41 @@
 
 #include "base/files/file_path.h"
 
+#include "build/build_config.h"
+
 namespace crashpad {
 namespace test {
 
 bool CreateFile(const base::FilePath& file);
 
+bool PathExists(const base::FilePath& path);
+
+#if !defined(OS_FUCHSIA) || DOXYGEN
+// There are no symbolic links on Fuchsia. Don’t bother declaring or defining
+// symbolic link-related functions at all, because it’s an error to even pretend
+// that symbolic links might be available on Fuchsia.
+
+//! \brief Determines whether it should be possible to create symbolic links.
+//!
+//! It is always possible to create symbolic links on POSIX.
+//!
+//! On Windows, it is only possible to create symbolic links when running as an
+//! administrator, or as a non-administrator when running Windows 10 build 15063
+//! (1703, Creators Update) or later, provided that developer mode is enabled
+//! and `SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE` is used. This function
+//! tests the creation of a symbolic link and returns true on success, and false
+//! on failure. If the symbolic link could not be created for a reason other
+//! than the expected lack of privilege, a message is logged.
+//!
+//! Additional background: <a
+//! href="https://blogs.windows.com/buildingapps/2016/12/02/symlinks-windows-10/">Symlinks
+//! in Windows 10!</a>
+bool CanCreateSymbolicLinks();
+
 bool CreateSymbolicLink(const base::FilePath& target_path,
                         const base::FilePath& symlink_path);
 
-bool PathExists(const base::FilePath& path);
+#endif  // !OS_FUCHSIA || DOXYGEN
 
 }  // namespace test
 }  // namespace crashpad

util/file/filesystem_win.cc

@@ -82,8 +82,7 @@ bool MoveFileOrDirectory(const base::FilePath& source,
 bool IsRegularFile(const base::FilePath& path) {
   DWORD fileattr = GetFileAttributes(path.value().c_str());
   if (fileattr == INVALID_FILE_ATTRIBUTES) {
-    PLOG_IF(ERROR, GetLastError() != ERROR_FILE_NOT_FOUND)
+    PLOG(ERROR) << "GetFileAttributes " << base::UTF16ToUTF8(path.value());
-        << "GetFileAttributes " << base::UTF16ToUTF8(path.value());
     return false;
   }
   if ((fileattr & FILE_ATTRIBUTE_DIRECTORY) != 0 ||