Merge "Add a WriteStringToFile overload that cares about permissions."

2 files changed, 38 insertions, 8 deletions

diff --git a/include/utils/file.h b/include/utils/file.h
index 108cabc..d6b7057 100644
--- a/include/utils/file.h
+++ b/include/utils/file.h
@@ -18,11 +18,14 @@
 #define UTILS_FILE_H
 
 #include <string>
+#include <sys/stat.h>
 
 namespace android {
 
 bool ReadFileToString(const std::string& path, std::string* content);
 bool WriteStringToFile(const std::string& content, const std::string& path);
+bool WriteStringToFile(const std::string& content, const std::string& path,
+                       mode_t mode, uid_t owner, gid_t group);
 
 } // namespace android
 
diff --git a/libutils/file.cpp b/libutils/file.cpp
index aa35ff2..bfd1f55 100644
--- a/libutils/file.cpp
+++ b/libutils/file.cpp
@@ -46,14 +46,7 @@ bool android::ReadFileToString(const std::string& path, std::string* content) {
   }
 }
 
-bool android::WriteStringToFile(const std::string& content, const std::string& path) {
-  int fd = TEMP_FAILURE_RETRY(open(path.c_str(),
-                                   O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC | O_NOFOLLOW,
-                                   DEFFILEMODE));
-  if (fd == -1) {
-    return false;
-  }
-
+static bool WriteStringToFd(const std::string& content, int fd) {
   const char* p = content.data();
   size_t left = content.size();
   while (left > 0) {
@@ -68,3 +61,37 @@ bool android::WriteStringToFile(const std::string& content, const std::string& p
   TEMP_FAILURE_RETRY(close(fd));
   return true;
 }
+
+static bool CleanUpAfterFailedWrite(const std::string& path) {
+  // Something went wrong. Let's not leave a corrupt file lying around.
+  int saved_errno = errno;
+  unlink(path.c_str());
+  errno = saved_errno;
+  return false;
+}
+
+bool android::WriteStringToFile(const std::string& content, const std::string& path,
+                                mode_t mode, uid_t owner, gid_t group) {
+  int fd = TEMP_FAILURE_RETRY(open(path.c_str(),
+                                   O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC | O_NOFOLLOW,
+                                   mode));
+  if (fd == -1) {
+    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.
+  if (fchmod(fd, mode) != -1 && fchown(fd, owner, group) == -1 && WriteStringToFd(content, fd)) {
+    return true;
+  }
+  return CleanUpAfterFailedWrite(path);
+}
+
+bool android::WriteStringToFile(const std::string& content, const std::string& path) {
+  int fd = TEMP_FAILURE_RETRY(open(path.c_str(),
+                                   O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC | O_NOFOLLOW,
+                                   DEFFILEMODE));
+  if (fd == -1) {
+    return false;
+  }
+  return WriteStringToFd(content, fd) || CleanUpAfterFailedWrite(path);
+}