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

Browse source 
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
This commit is contained in:
Elliott Hughes 2015-02-17 10:16:04 -08:00
parent 29576ae890
commit 9d1f515ed1
2 changed files with 31 additions and 2 deletions
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19
libutils/file.cpp
View file

@ -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

14
libutils/tests/file_test.cpp
View file

@ -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);