pipes/fifo_seqnum.h

+/* fifo_seqnum.h
+
+   Header file used by fifo_seqnum_server.c and fifo_seqnum_client.c
+
+   These programs create FIFOS in /tmp. This makes it easy to compile and
+   run the programs. However, for a security reasons, a real-world
+   application should never create sensitive files in /tmp. (As a simple of
+   example of the kind of security problems that can result, a malicious
+   user could create a FIFO using the name defined in SERVER_FIFO, and
+   thereby cause a denial of service attack against this application.
+   See Section 38.7 of "The Linux Programming Interface" for more details
+   on this subject.)
+*/
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 #include "tlpi_hdr.h"
 
 #define SERVER_FIFO "/tmp/seqnum_sv"
                                 /* Well-known name for server's FIFO */
 #define CLIENT_FIFO_TEMPLATE "/tmp/seqnum_cl.%ld"
                                 /* Template for building client FIFO name */
 #define CLIENT_FIFO_NAME_LEN (sizeof(CLIENT_FIFO_TEMPLATE) + 20)
                                 /* Space required for client FIFO pathname
                                   (+20 as a generous allowance for the PID) */
 
 struct request {                /* Request (client --> server) */
     pid_t pid;                  /* PID of client */
     int seqLen;                 /* Length of desired sequence */
 };
 
 struct response {               /* Response (server --> client) */
     int seqNum;                 /* Start of sequence */
 };