Only add trailing carriage return to messages if output is a raw tty.

If output is being written to a terminal in "raw" mode, we need to
add a carriage return after the newline to avoid "stair-step" output.
However, we should not write the carriage return if the terminal
is in "cooked" mode, output to a pipe, or output redirected to a file.
Bug #1042.

include/sudo_util.h

@@ -349,6 +349,8 @@ sudo_dso_public bool sudo_term_raw_v1(int fd, int isig);
 #define sudo_term_raw(_a, _b) sudo_term_raw_v1((_a), (_b))
 sudo_dso_public bool sudo_term_restore_v1(int fd, bool flush);
 #define sudo_term_restore(_a, _b) sudo_term_restore_v1((_a), (_b))
+sudo_dso_public bool sudo_term_is_raw_v1(int fd);
+#define sudo_term_is_raw(_a) sudo_term_is_raw_v1((_a))
 
 /* ttyname_dev.c */
 sudo_dso_public char *sudo_ttyname_dev_v1(dev_t tdev, char *name, size_t namelen);

lib/util/fatal.c

@@ -239,7 +239,7 @@ warning(const char *errstr, const char *fmt, va_list ap)
             fputs(": ", stderr);
             fputs(errstr, stderr);
         }
-        if (isatty(fileno(stderr)))
+        if (sudo_term_is_raw(fileno(stderr)))
             putc('\r', stderr);
         putc('\n', stderr);
     }

lib/util/term.c

@@ -288,3 +288,27 @@ sudo_term_copy_v1(int src, int dst)
 
     debug_return_bool(true);
 }
+
+/*
+ * Returns true if fd refers to a tty in raw mode, else false.
+ */
+bool
+sudo_term_is_raw_v1(int fd)
+{
+    struct termios term;
+    debug_decl(sudo_term_is_raw, SUDO_DEBUG_UTIL);
+
+    if (tcgetattr(fd, &term) != 0)
+	debug_return_bool(false);
+
+    if (term.c_cc[VMIN] != 1 || term.c_cc[VTIME] != 0)
+	debug_return_bool(false);
+
+    if (ISSET(term.c_oflag, OPOST))
+	debug_return_bool(false);
+
+    if (ISSET(term.c_oflag, ECHO|ECHONL|ICANON))
+	debug_return_bool(false);
+
+    debug_return_bool(true);
+}

lib/util/util.exp.in

@@ -145,6 +145,7 @@ sudo_term_cbreak_v1
 sudo_term_copy_v1
 sudo_term_eof
 sudo_term_erase
+sudo_term_is_raw_v1
 sudo_term_kill
 sudo_term_noecho_v1
 sudo_term_raw_v1

src/conversation.c

@@ -91,11 +91,16 @@ sudo_conversation(int num_msgs, const struct sudo_conv_message msgs[],
 		    const char *crnl = NULL;
 		    bool written = false;
 		    int ttyfd = -1;
+		    bool raw_tty = false;
 
 		    if (ISSET(msg->msg_type, SUDO_CONV_PREFER_TTY) &&
-			    !ISSET(tgetpass_flags, TGP_STDIN))
+			    !ISSET(tgetpass_flags, TGP_STDIN)) {
 			ttyfd = open(_PATH_TTY, O_WRONLY);
-		    if (len != 0 && (ttyfd != -1 || isatty(fileno(fp)))) {
+			raw_tty = sudo_term_is_raw(ttyfd);
+		    } else {
+			raw_tty = sudo_term_is_raw(fileno(fp));
+		    }
+		    if (len != 0 && raw_tty) {
 			/* Convert nl -> cr nl in case tty is in raw mode. */
 			if (msg->msg[len - 1] == '\n') {
 			    if (len == 1 || msg->msg[len - 2] != '\r') {
@@ -177,12 +182,14 @@ sudo_conversation_printf(int msg_type, const char *fmt, ...)
     case SUDO_CONV_INFO_MSG:
 	/* Convert nl -> cr nl in case tty is in raw mode. */
 	len = strlen(fmt);
-	if (len < ssizeof(fmt2) && len > 0 && fmt[len - 1] == '\n') {
+	if (sudo_term_is_raw(fileno(ttyfp ? ttyfp : fp))) {
-	    if (len == 1 || fmt[len - 2] != '\r') {
+	    if (len < ssizeof(fmt2) && len > 0 && fmt[len - 1] == '\n') {
-		memcpy(fmt2, fmt, len - 1);
+		if (len == 1 || fmt[len - 2] != '\r') {
-		fmt2[len - 1] = '\0';
+		    memcpy(fmt2, fmt, len - 1);
-		fmt = fmt2;
+		    fmt2[len - 1] = '\0';
-		crnl = "\r\n";
+		    fmt = fmt2;
+		    crnl = "\r\n";
+		}
 	    }
 	}
 	va_start(ap, fmt);