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Description: Predictable behaviour of client program.
Better error recovery and exeption handling.
.
Ignore the SIGPIPE trigger.
.
Give priority to reading the device being snooped at,
only then reading from standard input.
Author: Mats Erik Andersson <debian@gisladisker.se>
Forwarded: no
Last-Update: 2010-06-21
--- ttysnoop-0.12d.debian/ttysnoop.c
+++ ttysnoop-0.12d/ttysnoop.c
@@ -25,6 +25,7 @@
#include <grp.h>
#include <utmp.h>
#include <errno.h>
+#include <signal.h>
#include "config.h"
#include "common.h"
@@ -33,6 +34,11 @@
char buff[BUFF_SIZE];
+void message (void)
+{
+ printf ("\r\nBack at local tty.\r\n");
+}
+
int main (int argc, char *argv[])
{
fd_set readset;
@@ -40,24 +46,30 @@ int main (int argc, char *argv[])
int sockfd, fdmax, quit = 0, n;
char sockname[128];
+ if (geteuid())
+ errorf("Insufficient privileges.\n");
+
if (argc < 2)
errorf ("Usage: ttysnoop <pty>\n");
/* create the client socket */
if ((sockfd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
- errorf ("can't create client socket\n");
+ errorf ("Cannot create client socket.\n");
- sprintf (sockname, "%s/%s", SPOOLDIR, argv[1]);
+ snprintf (sockname, sizeof(sockname), "%s/%s", SPOOLDIR, argv[1]);
+ memset (&sock_addr, '\0', sizeof(sock_addr));
sock_addr.sun_family = AF_UNIX;
strncopy (sock_addr.sun_path, sockname);
+
if (connect(sockfd, (struct sockaddr *) &sock_addr, sizeof(sock_addr)) < 0)
- errorf ("can't connect to server\n");
+ errorf ("Cannot connect to server. Is it really a valid socket?\n");
/* put stdin into raw mode */
stty_initstore ();
atexit (stty_orig);
+ atexit (message);
if (isatty(STDIN_FILENO))
stty_raw (STDIN_FILENO);
@@ -67,32 +79,52 @@ int main (int argc, char *argv[])
/* do our thing */
+ signal(SIGPIPE, SIG_IGN);
+ FD_ZERO (&readset);
+
while (!quit)
{
- FD_ZERO (&readset);
+ int ret;
+
FD_SET (STDIN_FILENO, &readset);
FD_SET (sockfd, &readset);
- select (fdmax + 1, &readset, NULL, NULL, NULL);
-
- if (FD_ISSET(STDIN_FILENO, &readset))
- {
- n = read(STDIN_FILENO, buff, BUFF_SIZE);
+ if ( (ret = select (fdmax + 1, &readset, NULL, NULL, NULL)) < 0 ) {
+ if ( errno == EINTR )
+ continue;
- if (write(sockfd, buff, n) < 0)
- quit = 1;
+ break; /* Cannot recover. */
}
+ /* Give precedence to the end point where we snoop. */
if (FD_ISSET(sockfd, &readset))
{
- if ((n = read(sockfd, buff, BUFF_SIZE)) < 1)
- quit = 1;
+ if ((n = read(sockfd, buff, BUFF_SIZE)) <= 0) {
+ if ( (n < 0) && (errno == EINTR) )
+ continue;
+ if ( n == 0 )
+ break; /* EOF on socket. */
+ quit = 1; /* Will soon exit! */
+ }
if (n > 0)
write (STDOUT_FILENO, buff, n);
}
+
+ if (FD_ISSET(STDIN_FILENO, &readset))
+ {
+ n = read(STDIN_FILENO, buff, BUFF_SIZE);
+ if ( n == 0 ) {
+ /* The observer has left. Close down! */
+ shutdown(sockfd, SHUT_WR);
+ FD_CLR(STDIN_FILENO, &readset);
+ quit = 1;
+ }
+
+ if ( ( n > 0 ) && ( write(sockfd, buff, n) < 0 ) )
+ quit = 1; /* The terminal service has already closed down. */
+ }
}
- printf ("\r\nBack at local tty.\r\n");
return 0;
}
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