commit 309122017ebc6fff039a7cab1b82f632853d82d5
from: Alexander Barton <alex@barton.de>
date: Fri Aug 23 19:40:51 2013 UTC

Correctly handle return code of Handle_Write()

There have been code paths that ignored the return code of Handle_Write()
when sending "notice auth" messages to new clients connecting to the
server. But because Handle_Write() would have closed the client connection
again if an error occurred, this would have resulted in new errors and
assert()'s later on that could have crashed the server (denial of service).

Only setups having the configuration option "NoticeAuth" enabled are
affected, which is not the default.

CVE-2013-5580.

commit - 8f530eb3154c7d62201c28a53fac5594a956b447
commit + 309122017ebc6fff039a7cab1b82f632853d82d5
blob - 30dfd094467397ac958052fd41bfd5f33960ff14
blob + 8d72c1c3253ef9ecb2cea8fb6e3521ee72306fbb
--- src/ngircd/conn.c
+++ src/ngircd/conn.c
@@ -1668,7 +1668,11 @@ Conn_StartLogin(CONN_ID Idx)
 #endif
 			(void)Conn_WriteStr(Idx,
 				"NOTICE AUTH :*** Looking up your hostname");
-		(void)Handle_Write(Idx);
+		/* Send buffered data to the client, but break on errors
+		 * because Handle_Write() would have closed the connection
+		 * again in this case! */
+		if (!Handle_Write(Idx))
+			return;
 	}
 
 	Resolve_Addr(&My_Connections[Idx].proc_stat, &My_Connections[Idx].addr,
@@ -2458,8 +2462,13 @@ cb_Read_Resolver_Result( int r_fd, UNUSED short events
 		}
 #endif
 
-		if (Conf_NoticeAuth)
-			(void)Handle_Write(i);
+		if (Conf_NoticeAuth) {
+			/* Send buffered data to the client, but break on
+			 * errors because Handle_Write() would have closed
+			 * the connection again in this case! */
+			if (!Handle_Write(i))
+				return;
+		}
 
 		Class_HandleServerBans(c);
 	}