adding GNUNET_DISK_file_backup function; fixing #2646

2 files changed, 36 insertions, 9 deletions

diff --git a/src/util/crypto_rsa.c b/src/util/crypto_rsa.c
index ff99ecf0b..cd9a33f61 100644
--- a/src/util/crypto_rsa.c
+++ b/src/util/crypto_rsa.c
@@ -641,12 +641,11 @@ try_read_key (const char *filename)
   if (fs > UINT16_MAX)
   {
     LOG (GNUNET_ERROR_TYPE_ERROR,
-         _("File `%s' does not contain a valid private key (too long, %llu bytes).  Deleting it.\n"),   
+         _("File `%s' does not contain a valid private key (too long, %llu bytes).  Renaming it.\n"),   
          filename,
          (unsigned long long) fs);
     GNUNET_break (GNUNET_OK == GNUNET_DISK_file_close (fd));
-    if (0 != UNLINK (filename))    
-      LOG_STRERROR_FILE (GNUNET_ERROR_TYPE_WARNING, "unlink", filename);
+    GNUNET_DISK_file_backup (filename);
     return NULL;
   }
 
@@ -662,8 +661,7 @@ try_read_key (const char *filename)
          filename,
          (unsigned long long) fs);
     GNUNET_break (GNUNET_OK == GNUNET_DISK_file_close (fd));
-    if (0 != UNLINK (filename))    
-      LOG_STRERROR_FILE (GNUNET_ERROR_TYPE_WARNING, "unlink", filename);
+    GNUNET_DISK_file_backup (filename);
     GNUNET_free (enc);
     return NULL;
   }
@@ -857,10 +855,7 @@ GNUNET_CRYPTO_rsa_key_create_from_file (const char *filename)
     LOG (GNUNET_ERROR_TYPE_ERROR,
          _("File `%s' does not contain a valid private key.  Deleting it.\n"),
          filename);
-    if (0 != UNLINK (filename))
-    {
-      LOG_STRERROR_FILE (GNUNET_ERROR_TYPE_WARNING, "unlink", filename);
-    }
+    GNUNET_DISK_file_backup (filename);
   }
   GNUNET_free (enc);
   if (GNUNET_YES !=
diff --git a/src/util/disk.c b/src/util/disk.c
index 8d1fed897..8cb69d2a4 100644
--- a/src/util/disk.c
+++ b/src/util/disk.c
@@ -495,6 +495,38 @@ GNUNET_DISK_mkdtemp (const char *t)
 
 
 /**
+ * Move a file out of the way (create a backup) by
+ * renaming it to "orig.NUM~" where NUM is the smallest
+ * number that is not used yet.
+ *
+ * @param fil name of the file to back up
+ */
+void
+GNUNET_DISK_file_backup (const char *fil)
+{
+  size_t slen;
+  char *target;
+  unsigned int num;
+
+  slen = strlen (fil) + 20;
+  target = GNUNET_malloc (slen);
+  num = 0;
+  do
+  {
+    GNUNET_snprintf (target, slen,
+                     "%s.%u~",
+                     fil,
+                     num++);
+  } while (0 == access (target, F_OK));
+  if (0 != rename (fil, target))
+    GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR,
+                              "rename",
+                              fil);
+  GNUNET_free (target);  
+}
+
+
+/**
  * Create an (empty) temporary file on disk.  If the given name is not
  * an absolute path, the current 'TMPDIR' will be prepended.  In any case,
  * 6 random characters will be appended to the name to create a unique