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Commit 9d1f515e authored by Elliott Hughes's avatar Elliott Hughes
Browse files

Fix the WriteStringToFile overload that takes mode/owner/group. 

The actual bug is == instead of !=, but the real cause was me trying to be
too clever. This patch switches to much simpler code, and -- since the
intended use of this code is security anyway -- adds logging if anything
goes wrong.

Bug: 19361774
Change-Id: If2af07d31a5002f9010b838247b691f6b28bdfb1
parent 29576ae8

libutils/file.cpp

+17 −2
Original line number Diff line number Diff line
@@ -14,6 +14,9 @@ 
 * limitations under the License.

 */



#define LOG_TAG "utils.file"

#include <cutils/log.h>



#include "utils/file.h"



#include <errno.h>
@@ -75,14 +78,26 @@ bool android::WriteStringToFile(const std::string& content, const std::string& p 
                                   O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC | O_NOFOLLOW,

                                   mode));

  if (fd == -1) {

    ALOGE("android::WriteStringToFile open failed: %s", strerror(errno));

    return false;

  }



  // We do an explicit fchmod here because we assume that the caller really meant what they

  // said and doesn't want the umask-influenced mode.

  bool result = (fchmod(fd, mode) != -1 && fchown(fd, owner, group) == -1 && WriteStringToFd(content, fd));

  if (fchmod(fd, mode) == -1) {

    ALOGE("android::WriteStringToFile fchmod failed: %s", strerror(errno));

    return CleanUpAfterFailedWrite(path);

  }

  if (fchown(fd, owner, group) == -1) {

    ALOGE("android::WriteStringToFile fchown failed: %s", strerror(errno));

    return CleanUpAfterFailedWrite(path);

  }

  if (!WriteStringToFd(content, fd)) {

    ALOGE("android::WriteStringToFile write failed: %s", strerror(errno));

    return CleanUpAfterFailedWrite(path);

  }

  TEMP_FAILURE_RETRY(close(fd));

  return result || CleanUpAfterFailedWrite(path);

  return true;

}

#endif

libutils/tests/file_test.cpp

+14 −0
Original line number Diff line number Diff line
@@ -71,6 +71,20 @@ TEST(file, WriteStringToFile) { 
  EXPECT_EQ("abc", s);

}



TEST(file, WriteStringToFile2) {

  TemporaryFile tf;

  ASSERT_TRUE(tf.fd != -1);

  ASSERT_TRUE(android::WriteStringToFile("abc", tf.filename, 0660, getuid(), getgid())) << errno;

  struct stat sb;

  ASSERT_EQ(0, stat(tf.filename, &sb));

  ASSERT_EQ(0660U, (sb.st_mode & ~S_IFMT));

  ASSERT_EQ(getuid(), sb.st_uid);

  ASSERT_EQ(getgid(), sb.st_gid);

  std::string s;

  ASSERT_TRUE(android::ReadFileToString(tf.filename, &s)) << errno;

  EXPECT_EQ("abc", s);

}



TEST(file, WriteStringToFd) {

  TemporaryFile tf;

  ASSERT_TRUE(tf.fd != -1);