Add support for resetting the terminal modes on stderr to something sensible

before printing error messages to it.  This should fix the stair-stepping
in Plink's progress messages.

[originally from svn r7745]

unix/unix.h

@@ -60,6 +60,18 @@ extern long tickcount_offset;
 #define WCHAR wchar_t
 #define BYTE unsigned char
 
+/*
+ * Unix-specific global flag
+ *
+ * FLAG_STDERR_TTY indicates that standard error might be a terminal and
+ * might get its configuration munged, so anything trying to output plain
+ * text (i.e. with newlines in it) will need to put it back into cooked
+ * mode first.  Applications setting this flag should also call
+ * stderr_tty_init() before messing with any terminal modes, and can call
+ * premsg() before outputting text to stderr and postmsg() afterwards.
+ */
+#define FLAG_STDERR_TTY 0x1000
+
 /* Things pty.c needs from pterm.c */
 char *get_x_display(void *frontend);
 int font_dimension(void *frontend, int which);/* 0 for width, 1 for height */
@@ -91,6 +103,12 @@ char *x_get_default(const char *key);
 /* Things uxstore.c provides to pterm.c */
 void provide_xrm_string(char *string);
 
+/* Things provided by uxcons.c */
+struct termios;
+void stderr_tty_init(void);
+void premsg(struct termios *);
+void postmsg(struct termios *);
+
 /* The interface used by uxsel.c */
 void uxsel_init(void);
 typedef int (*uxsel_callback_fn)(int fd, int event);

unix/uxcons.c

@@ -18,6 +18,31 @@ int console_batch_mode = FALSE;
 
 static void *console_logctx = NULL;
 
+static struct termios orig_termios_stderr;
+static int stderr_is_a_tty;
+
+void stderr_tty_init()
+{
+    /* Ensure that if stderr is a tty, we can get it back to a sane state. */
+    if ((flags & FLAG_STDERR_TTY) && isatty(STDERR_FILENO)) {
+	stderr_is_a_tty = TRUE;
+	tcgetattr(STDERR_FILENO, &orig_termios_stderr);
+    }
+}
+
+void premsg(struct termios *cf)
+{
+    if (stderr_is_a_tty) {
+	tcgetattr(STDERR_FILENO, cf);
+	tcsetattr(STDERR_FILENO, TCSADRAIN, &orig_termios_stderr);
+    }
+}
+void postmsg(struct termios *cf)
+{
+    if (stderr_is_a_tty)
+	tcsetattr(STDERR_FILENO, TCSADRAIN, cf);
+}
+
 /*
  * Clean up and exit.
  */
@@ -101,6 +126,7 @@ int verify_ssh_host_key(void *frontend, char *host, int port, char *keytype,
     static const char abandoned[] = "Connection abandoned.\n";
 
     char line[32];
+    struct termios cf;
 
     /*
      * Verify the key.
@@ -110,6 +136,7 @@ int verify_ssh_host_key(void *frontend, char *host, int port, char *keytype,
     if (ret == 0)		       /* success - key matched OK */
 	return 1;
 
+    premsg(&cf);
     if (ret == 2) {		       /* key was different */
 	if (console_batch_mode) {
 	    fprintf(stderr, wrongmsg_batch, keytype, fingerprint);
@@ -141,9 +168,11 @@ int verify_ssh_host_key(void *frontend, char *host, int port, char *keytype,
     if (line[0] != '\0' && line[0] != '\r' && line[0] != '\n') {
 	if (line[0] == 'y' || line[0] == 'Y')
 	    store_host_key(host, port, keytype, keystr);
+	postmsg(&cf);
         return 1;
     } else {
 	fprintf(stderr, abandoned);
+	postmsg(&cf);
         return 0;
     }
 }
@@ -166,7 +195,9 @@ int askalg(void *frontend, const char *algtype, const char *algname,
     static const char abandoned[] = "Connection abandoned.\n";
 
     char line[32];
+    struct termios cf;
 
+    premsg(&cf);
     if (console_batch_mode) {
 	fprintf(stderr, msg_batch, algtype, algname);
 	return 0;
@@ -187,9 +218,11 @@ int askalg(void *frontend, const char *algtype, const char *algname,
     }
 
     if (line[0] == 'y' || line[0] == 'Y') {
+	postmsg(&cf);
 	return 1;
     } else {
 	fprintf(stderr, abandoned);
+	postmsg(&cf);
 	return 0;
     }
 }
@@ -215,7 +248,9 @@ int askappend(void *frontend, Filename filename,
 	"Logging will not be enabled.\n";
 
     char line[32];
+    struct termios cf;
 
+    premsg(&cf);
     if (console_batch_mode) {
 	fprintf(stderr, msgtemplate_batch, FILENAME_MAX, filename.path);
 	fflush(stderr);
@@ -235,6 +270,7 @@ int askappend(void *frontend, Filename filename,
 	tcsetattr(0, TCSANOW, &oldmode);
     }
 
+    postmsg(&cf);
     if (line[0] == 'y' || line[0] == 'Y')
 	return 2;
     else if (line[0] == 'n' || line[0] == 'N')
@@ -266,7 +302,10 @@ void old_keyfile_warning(void)
 	"Once the key is loaded into PuTTYgen, you can perform\n"
 	"this conversion simply by saving it again.\n";
 
+    struct termios cf;
+    premsg(&cf);
     fputs(message, stderr);
+    postmsg(&cf);
 }
 
 void console_provide_logctx(void *logctx)
@@ -276,8 +315,11 @@ void console_provide_logctx(void *logctx)
 
 void logevent(void *frontend, const char *string)
 {
+    struct termios cf;
+    premsg(&cf);
     if (console_logctx)
 	log_eventlog(console_logctx, string);
+    postmsg(&cf);
 }
 
 static void console_data_untrusted(const char *data, int len)

unix/uxplink.c

@@ -27,14 +27,19 @@
 
 void *logctx;
 
+static struct termios orig_termios;
+
 void fatalbox(char *p, ...)
 {
+    struct termios cf;
     va_list ap;
+    premsg(&cf);
     fprintf(stderr, "FATAL ERROR: ");
     va_start(ap, p);
     vfprintf(stderr, p, ap);
     va_end(ap);
     fputc('\n', stderr);
+    postmsg(&cf);
     if (logctx) {
         log_free(logctx);
         logctx = NULL;
@@ -43,12 +48,15 @@ void fatalbox(char *p, ...)
 }
 void modalfatalbox(char *p, ...)
 {
+    struct termios cf;
     va_list ap;
+    premsg(&cf);
     fprintf(stderr, "FATAL ERROR: ");
     va_start(ap, p);
     vfprintf(stderr, p, ap);
     va_end(ap);
     fputc('\n', stderr);
+    postmsg(&cf);
     if (logctx) {
         log_free(logctx);
         logctx = NULL;
@@ -57,12 +65,15 @@ void modalfatalbox(char *p, ...)
 }
 void connection_fatal(void *frontend, char *p, ...)
 {
+    struct termios cf;
     va_list ap;
+    premsg(&cf);
     fprintf(stderr, "FATAL ERROR: ");
     va_start(ap, p);
     vfprintf(stderr, p, ap);
     va_end(ap);
     fputc('\n', stderr);
+    postmsg(&cf);
     if (logctx) {
         log_free(logctx);
         logctx = NULL;
@@ -71,17 +82,19 @@ void connection_fatal(void *frontend, char *p, ...)
 }
 void cmdline_error(char *p, ...)
 {
+    struct termios cf;
     va_list ap;
+    premsg(&cf);
     fprintf(stderr, "plink: ");
     va_start(ap, p);
     vfprintf(stderr, p, ap);
     va_end(ap);
     fputc('\n', stderr);
+    postmsg(&cf);
     exit(1);
 }
 
 static int local_tty = FALSE; /* do we have a local tty? */
-static struct termios orig_termios;
 
 static Backend *back;
 static void *backhandle;
@@ -582,7 +595,9 @@ int main(int argc, char **argv)
     default_protocol = PROT_SSH;
     default_port = 22;
 
-    flags = FLAG_STDERR;
+    flags = FLAG_STDERR | FLAG_STDERR_TTY;
+
+    stderr_tty_init();
     /*
      * Process the command line.
      */