When creating a file for DCC download, make sure we won't run into any race

conditions if /SET dcc_download_path was set to some directory where other
users could write files as well. Also, the created file mode is always 0600
now.


git-svn-id: http://svn.irssi.org/repos/irssi/trunk@2318 dbcabf3a-b0e7-0310-adc4-f8d773084564

1 files changed, 26 insertions, 3 deletions

diff --git a/src/irc/dcc/dcc-get.c b/src/irc/dcc/dcc-get.c
index 39b368f6..b04cab40 100644
--- a/src/irc/dcc/dcc-get.c
+++ b/src/irc/dcc/dcc-get.c
@@ -169,7 +169,8 @@ static void sig_dccget_receive(GET_DCC_REC *dcc)
 static void sig_dccget_connected(GET_DCC_REC *dcc)
 {
 	struct stat statbuf;
-	char *fname;
+	char *fname, *tempfname;
+        int temphandle, old_umask;
 
 	if (net_geterror(dcc->handle) != 0) {
 		/* error connecting */
@@ -195,8 +196,30 @@ static void sig_dccget_connected(GET_DCC_REC *dcc)
 	}
 
 	if (dcc->get_type != DCC_GET_RESUME) {
-		dcc->fhandle = open(dcc->file, O_WRONLY | O_TRUNC | O_CREAT,
-				    dcc_file_create_mode);
+		/* we want to overwrite the file, remove it here.
+		   if it gets created after this, we'll fail. */
+		unlink(dcc->file);
+
+		/* just to make sure we won't run into race conditions
+		   if download_path is in some global temp directory */
+		tempfname = g_strconcat(dcc->file, ".XXXXXX", NULL);
+
+                old_umask = umask(066);
+		temphandle = mkstemp(tempfname);
+                umask(old_umask);
+
+                dcc->fhandle = -1;
+		if (link(tempfname, dcc->file) == 0) {
+                        /* ok, we're the file owner now */
+			dcc->fhandle = open(dcc->file, O_WRONLY | O_TRUNC | O_CREAT,
+					    dcc_file_create_mode);
+		}
+
+                /* close/remove the temp file */
+		close(temphandle);
+		unlink(tempfname);
+		g_free(tempfname);
+
 		if (dcc->fhandle == -1) {
 			signal_emit("dcc error file create", 2,
 				    dcc, dcc->file);