output_data(), output_datalen() and netflush() didn't actually guarantee

to do what they are supposed to: under some circumstances output data would
be truncated, or the buffer would not actually be flushed (possibly leading
to overflows when the caller assumes the operation succeeded).  Change the
semantics so that these functions ensure they complete the operation before
returning.

Comment out diagnostic code enabled by '-D reports' which causes an
infinite recursion and an eventual crash.

Patch developed with assistance from ru and assar.


git-svn-id: http://svn0.us-east.freebsd.org/base/head/contrib/telnet@80224 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f

telnetd/ext.h

@@ -190,7 +190,7 @@ extern void
 	wontoption P((int));
 
 int	output_data __P((const char *, ...)) __printflike(1, 2);
-int	output_datalen __P((const char *, size_t));
+void	output_datalen __P((const char *, int));
 
 #ifdef	ENCRYPTION
 extern void	(*encrypt_output) P((unsigned char *, int));

telnetd/slc.c

@@ -176,7 +176,6 @@ end_slc(bufp)
 	register unsigned char **bufp;
 {
 	register int len;
-	void netflush();
 
 	/*
 	 * If a change has occured, store the new terminal control

telnetd/state.c

@@ -1615,40 +1615,46 @@ send_status()
 
 /*
  * This function appends data to nfrontp and advances nfrontp.
+ * Returns the number of characters written altogether (the
+ * buffer may have been flushed in the process).
  */
 
 int
 output_data(const char *format, ...)
 {
 	va_list args;
-	size_t remaining, ret;
+	int len;
+	char *buf;
 
 	va_start(args, format);
-	remaining = BUFSIZ - (nfrontp - netobuf);
-	/* try a netflush() if the room is too low */
-	if (strlen(format) > remaining || BUFSIZ / 4 > remaining) {
-		netflush();
-		remaining = BUFSIZ - (nfrontp - netobuf);
-	}
-	ret = vsnprintf(nfrontp, remaining, format, args);
-	nfrontp += (ret < remaining) ? ret : remaining;
+	if ((len = vasprintf(&buf, format, args)) == -1)
+		return -1;
+	output_datalen(buf, len);
 	va_end(args);
-	return ret;
-}
-
-int
-output_datalen(const char *buf, size_t len)
-{
-	size_t remaining;
-
-	remaining = BUFSIZ - (nfrontp - netobuf);
-	if (remaining < len) {
-		netflush();
-		remaining = BUFSIZ - (nfrontp - netobuf);
-		if (remaining < len)
-			return -1;
-	}
-	memmove(nfrontp, buf, len);
-	nfrontp += len;
+	free(buf);
 	return (len);
 }
+
+void
+output_datalen(const char *buf, int len)
+{
+	int remaining, copied;
+	
+	remaining = BUFSIZ - (nfrontp - netobuf);
+	while (len > 0) {
+		/* Free up enough space if the room is too low*/
+		if ((len > BUFSIZ ? BUFSIZ : len) > remaining) {
+			netflush();
+			remaining = BUFSIZ - (nfrontp - netobuf);
+		}
+
+		/* Copy out as much as will fit */
+		copied = remaining > len ? len : remaining;
+		memmove(nfrontp, buf, copied);
+		nfrontp += copied;
+		len -= copied;
+		remaining -= copied;
+		buf += copied;
+	}
+	return;
+}

telnetd/telnetd.c

@@ -952,7 +952,6 @@ telnet(f, p, host)
 	char *HE;
 	char *HN;
 	char *IM;
-	void netflush();
 	int nfd;
 
 	/*

telnetd/termstat.c

@@ -140,7 +140,6 @@ int	newmap = 1;	/* nonzero if \n maps to ^M^J */
 	void
 localstat()
 {
-	void netflush();
 	int need_will_echo = 0;
 
 #if	defined(CRAY2) && defined(UNICOS5)
@@ -404,7 +403,6 @@ flowstat()
 clientstat(code, parm1, parm2)
 	register int code, parm1, parm2;
 {
-	void netflush();
 
 	/*
 	 * Get a copy of terminal characteristics.

telnetd/utility.c

@@ -69,10 +69,9 @@ static const char rcsid[] =
     void
 ttloop()
 {
-    void netflush();
 
     DIAG(TD_REPORT, output_data("td: ttloop\r\n"));
-    if (nfrontp-nbackp) {
+    if (nfrontp - nbackp > 0) {
 	netflush();
     }
     ncc = read(net, netibuf, sizeof netibuf);
@@ -257,10 +256,13 @@ netflush()
     int n;
     extern int not42;
 
-    if ((n = nfrontp - nbackp) > 0) {
+    while ((n = nfrontp - nbackp) > 0) {
+#if 0
+	/* XXX This causes output_data() to recurse and die */
 	DIAG(TD_REPORT, {
 	    n += output_data("td: netflush %d chars\r\n", n);
 	});
+#endif
 #ifdef	ENCRYPTION
 	if (encrypt_output) {
 		char *s = nclearto ? nclearto : nbackp;
@@ -293,25 +295,26 @@ netflush()
 		n = send(net, nbackp, n, MSG_OOB);	/* URGENT data */
 	    }
 	}
-    }
-    if (n < 0) {
-	if (errno == EWOULDBLOCK || errno == EINTR)
-		return;
-	cleanup(0);
-    }
-    nbackp += n;
+	if (n == -1) {
+	    if (errno == EWOULDBLOCK || errno == EINTR)
+		continue;
+	    cleanup(0);
+	    /* NOTREACHED */
+	}
+	nbackp += n;
 #ifdef	ENCRYPTION
-    if (nbackp > nclearto)
-	nclearto = 0;
+	if (nbackp > nclearto)
+	    nclearto = 0;
 #endif	/* ENCRYPTION */
-    if (nbackp >= neturg) {
-	neturg = 0;
-    }
-    if (nbackp == nfrontp) {
-	nbackp = nfrontp = netobuf;
+	if (nbackp >= neturg) {
+	    neturg = 0;
+	}
+	if (nbackp == nfrontp) {
+	    nbackp = nfrontp = netobuf;
 #ifdef	ENCRYPTION
-	nclearto = 0;
+	    nclearto = 0;
 #endif	/* ENCRYPTION */
+	}
     }
     return;
 }  /* end of netflush */