Revert 237242 "Linux sandbox: move CurrentProcessHasOpenDirectories"

> Linux sandbox: move CurrentProcessHasOpenDirectories
> 
> Move CurrentProcessHasOpenDirectories() to the Credentials class and rename
> it to HasOpenDirectory().
> Also add some unittests.
> 
> BUG=312380
> R=jorgelo@chromium.org
> 
> Review URL: https://codereview.chromium.org/85403011

TBR=jln@chromium.org

Review URL: https://codereview.chromium.org/85343005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237251 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 3 insertions, 121 deletions

diff --git a/sandbox/linux/services/credentials.cc b/sandbox/linux/services/credentials.cc
index cea757c..0af5a42b 100644
--- a/sandbox/linux/services/credentials.cc
+++ b/sandbox/linux/services/credentials.cc
@@ -4,13 +4,9 @@
 
 #include "sandbox/linux/services/credentials.h"
 
-#include <dirent.h>
 #include <errno.h>
-#include <fcntl.h>
 #include <stdio.h>
 #include <sys/capability.h>
-#include <sys/stat.h>
-#include <sys/types.h>
 #include <unistd.h>
 
 #include "base/basictypes.h"
@@ -53,15 +49,6 @@ struct FILECloser {
 // TODO(jln): fix base/.
 typedef scoped_ptr<FILE, FILECloser> ScopedFILE;
 
-struct DIRCloser {
-  void operator()(DIR* d) const {
-    DCHECK(d);
-    PCHECK(0 == closedir(d));
-  }
-};
-
-typedef scoped_ptr<DIR, DIRCloser> ScopedDIR;
-
 COMPILE_ASSERT((base::is_same<uid_t, gid_t>::value), UidAndGidAreSameType);
 // generic_id_t can be used for either uid_t or gid_t.
 typedef uid_t generic_id_t;
@@ -156,51 +143,6 @@ Credentials::Credentials() {
 Credentials::~Credentials() {
 }
 
-bool Credentials::HasOpenDirectory(int proc_fd) {
-  int proc_self_fd = -1;
-  if (proc_fd >= 0) {
-    proc_self_fd = openat(proc_fd, "self/fd", O_DIRECTORY | O_RDONLY);
-  } else {
-    proc_self_fd = openat(AT_FDCWD, "/proc/self/fd", O_DIRECTORY | O_RDONLY);
-    if (proc_self_fd < 0) {
-      // If not available, guess false.
-      // TODO(mostynb@opera.com): add a CHECK_EQ(ENOENT, errno); Figure out what
-      // other situations are here. http://crbug.com/314985
-      return false;
-    }
-  }
-  CHECK_GE(proc_self_fd, 0);
-
-  // Ownership of proc_self_fd is transferred here, it must not be closed
-  // or modified afterwards except via dir.
-  ScopedDIR dir(fdopendir(proc_self_fd));
-  CHECK(dir);
-
-  struct dirent e;
-  struct dirent* de;
-  while (!readdir_r(dir.get(), &e, &de) && de) {
-    if (strcmp(e.d_name, ".") == 0 || strcmp(e.d_name, "..") == 0) {
-      continue;
-    }
-
-    int fd_num;
-    CHECK(base::StringToInt(e.d_name, &fd_num));
-    if (fd_num == proc_fd || fd_num == proc_self_fd) {
-      continue;
-    }
-
-    struct stat s;
-    // It's OK to use proc_self_fd here, fstatat won't modify it.
-    CHECK(fstatat(proc_self_fd, e.d_name, &s, 0) == 0);
-    if (S_ISDIR(s.st_mode)) {
-      return true;
-    }
-  }
-
-  // No open unmanaged directories found.
-  return false;
-}
-
 bool Credentials::DropAllCapabilities() {
   ScopedCap cap(cap_init());
   CHECK(cap);
@@ -257,9 +199,6 @@ bool Credentials::MoveToNewUserNS() {
 }
 
 bool Credentials::DropFileSystemAccess() {
-  // Chrooting to a safe empty dir will only be safe if no directory file
-  // descriptor is available to the process.
-  DCHECK(!HasOpenDirectory(-1));
   return ChrootToSafeEmptyDir();
 }
 
diff --git a/sandbox/linux/services/credentials.h b/sandbox/linux/services/credentials.h
index c23db93..80b2ec1 100644
--- a/sandbox/linux/services/credentials.h
+++ b/sandbox/linux/services/credentials.h
@@ -26,20 +26,6 @@ class Credentials {
   Credentials();
   ~Credentials();
 
-  // Checks whether the current process has any directory file descriptor open.
-  // Directory file descriptors are "capabilities" that would let a process use
-  // system calls such as openat() to bypass restrictions such as
-  // DropFileSystemAccess().
-  // Sometimes it's useful to call HasOpenDirectory() after file system access
-  // has been dropped. In this case, |proc_fd| should be a file descriptor to
-  // /proc. The file descriptor in |proc_fd| will be ignored by
-  // HasOpenDirectory() and remains owned by the caller. It is very important
-  // for the caller to close it.
-  // If /proc is available, |proc_fd| can be passed as -1.
-  // If |proc_fd| is -1 and /proc is not available, this function will return
-  // false.
-  bool HasOpenDirectory(int proc_fd);
-
   // Drop all capabilities in the effective, inheritable and permitted sets for
   // the current process.
   bool DropAllCapabilities();
@@ -66,8 +52,9 @@ class Credentials {
   // CAP_SYS_CHROOT can be acquired by using the MoveToNewUserNS() API.
   // Make sure to call DropAllCapabilities() after this call to prevent
   // escapes.
-  // To be secure, it's very important for this API to not be called while the
-  // process has any directory file descriptor open.
+  // To be secure, it's very important for this API to not be called with any
+  // directory file descriptor present. TODO(jln): integrate with
+  // crbug.com/269806 when available.
   bool DropFileSystemAccess();
 
  private:
diff --git a/sandbox/linux/services/credentials_unittest.cc b/sandbox/linux/services/credentials_unittest.cc
index 9160bf7..da61cd5 100644
--- a/sandbox/linux/services/credentials_unittest.cc
+++ b/sandbox/linux/services/credentials_unittest.cc
@@ -5,20 +5,14 @@
 #include "sandbox/linux/services/credentials.h"
 
 #include <errno.h>
-#include <fcntl.h>
 #include <stdio.h>
-#include <sys/stat.h>
-#include <sys/types.h>
 #include <unistd.h>
 
-#include "base/file_util.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "sandbox/linux/tests/unit_tests.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-using file_util::ScopedFD;
-
 namespace sandbox {
 
 namespace {
@@ -58,44 +52,6 @@ TEST(Credentials, CreateAndDestroy) {
   scoped_ptr<Credentials> cred2(new Credentials);
 }
 
-TEST(Credentials, HasOpenDirectory) {
-  Credentials creds;
-  // No open directory should exist at startup.
-  EXPECT_FALSE(creds.HasOpenDirectory(-1));
-  {
-    // Have a "/dev" file descriptor around.
-    int dev_fd = open("/dev", O_RDONLY | O_DIRECTORY);
-    ScopedFD dev_fd_closer(&dev_fd);
-    EXPECT_TRUE(creds.HasOpenDirectory(-1));
-  }
-  EXPECT_FALSE(creds.HasOpenDirectory(-1));
-}
-
-TEST(Credentials, HasOpenDirectoryWithFD) {
-  Credentials creds;
-
-  int proc_fd = open("/proc", O_RDONLY | O_DIRECTORY);
-  ScopedFD proc_fd_closer(&proc_fd);
-  ASSERT_LE(0, proc_fd);
-
-  // Don't pass |proc_fd|, an open directory (proc_fd) should
-  // be detected.
-  EXPECT_TRUE(creds.HasOpenDirectory(-1));
-  // Pass |proc_fd| and no open directory should be detected.
-  EXPECT_FALSE(creds.HasOpenDirectory(proc_fd));
-
-  {
-    // Have a "/dev" file descriptor around.
-    int dev_fd = open("/dev", O_RDONLY | O_DIRECTORY);
-    ScopedFD dev_fd_closer(&dev_fd);
-    EXPECT_TRUE(creds.HasOpenDirectory(proc_fd));
-  }
-
-  // The "/dev" file descriptor should now be closed, |proc_fd| is the only
-  // directory file descriptor open.
-  EXPECT_FALSE(creds.HasOpenDirectory(proc_fd));
-}
-
 SANDBOX_TEST(Credentials, DropAllCaps) {
   Credentials creds;
   CHECK(creds.DropAllCapabilities());